Light interaction with nanomaterials

Resume : Semiconductor quantum dots (QDs) have attracted increasing interest in the last two decades, because of their tunable band-gap, their narrow luminescence and because they can act as sources of non-classical light states, potentially useful in quantum information technology. For such advanced applications, however, the requisite control of the QD's position and confinement potential cannot be achieved by the conventional bottom-up growth techniques, which currently give the best results in terms of QD optical properties. In this work, site-controlled, single-photon emitting QDs are created by exploiting the H properties in Ga(AsN). H irradiation of Ga(AsN) results in the formation of N-2H-H complexes, which neutralize all the effects N incorporation has on GaAs, including a large reduction of the band-gap energy. Starting from a completely hydrogenated GaAs/Ga(AsN):H/GaAs quantum well, we demonstrated the ability to selectively break the N-H bonds located within the near-field hot spot generated by a SNOM tip, thus obtaining site-controlled Ga(AsN) QDs surrounded by a barrier of Ga(AsN):H. By tuning the laser power density and exposure time, the optical properties of these QDs were optimized to obtain quantum confinement effects, sharp and bright emissions on the nanosecond timescale and antibunching in single-exciton recombination. The present work also paves the way for the fabrication of more elaborate nanostructures, such as quantum wires, quantum rings and QD molecules.

Resume : Active control of three-dimensional configuration is one of the key steps towards smart plasmonic nanostructures with desired functionalities. We lay out a multi-disciplinary strategy to create active 3D plasmonic nanostructures, which execute DNA-regulated conformational changes on the nanoscale. Construction of 3D reconfigurable plasmonic nanostructures witnesses major technological limitations, arising from the required subwavelength dimensions and controlled 3D motion. There have been considerable efforts on integration of plasmonic nanostructures with active platforms using top-down techniques. Here we lay out and implement a multi-disciplinary strategy to create active 3D plasmonic nanostructures by merging plasmonics and DNA nanotechnology on the nanoscale. First, we show the creation of a reconfigurable plasmonic switch, which can execute DNA-regulated conformational changes. In one role, DNA works as molecular platform for organizing plasmonic nanoparticles into a 3D architecture. In the other role, DNA is used as fuel to drive the constructed 3D plasmonic switch along fully programmable routes. Simultaneously, the 3D plasmonic switch serves as optical reporter, which transduces its own conformational information into optical circular dichroism changes upon external stimuli in real time. Next, we demonstrate the first plasmonic walker, which can carry out directional, progressive, and reverse nanoscale walking on a DNA original origami track.

Resume : Abstract: Recent studies have shown that plasmonic nanostructures can be used to drive chemical reaction with visible light. This behavior is attributed to the plasmonic effect of some noble Metal Nanoparticles (MNPs). Indeed, the free electron gas of such MNPs features a resonant oscillation upon illumination in the visible part of the spectrum [1,2]. This resonant electronic oscillation is known by localized surface plasmon resonance (LSPR); which is accompanied by valuable physical effects such as optical-near field enhancement, heat generation and hot electron injection [3,4] . Since then, the MNPs tend to behave as efficient sources of light, heat and energetic electrons [3]. Their excitation provides an efficient conversion of light into heat that can then transfer energy to the microenvironment of the NPs [5]. Moreover, it can provide an electronic transition for nearby molecules. Therefore, the above mentioned approaches have been applied to a large variety of chemical reactions [6,7]. In this work, the possibility to triggering thermally chemical reactions and electronic transfer from Gold NPs (GNPs) to semi-conductors through LSPR excitation is studied. In this context, we use the oxidation of glycerol (co-product of biodiesel production) as probe reaction that is catalyzed in the presence of supported GNPs and thermally activated by using green laser excitation at 532 nm at atmospheric pressure and ambient temperature. The obtained conversion was 89% after 2 h of reaction at ambient temperature. Experimental results indicate that oxidation was induced by photoexcited GNPs and that organic acid such as glyceric acid and tartronic acid are appropriate as essential products in the oxidation reaction. More interestingly, the reaction does not occur in the absence of laser irradiation. In parallel, we investigate the coupling between Plasmonic GNPs and catalyst supports such as TiO2, ZnO and Al2O3 in order to study the photodegradation of Bisphenol A (BPA). In this study, a thin film of TiO2 was fabricated by sol-gel spin coating method. The thickness can be adjusted by repeating the cycle by adding the Titanium alkoxide precursor on the substrate after calcination at 450?C. The morphology of the nanocomposite and the phases of the films were determined by (Scanning Electron Microscope) SEM and Raman. MNPs with tunable resonance frequency are deposited on the surface of semi-conductor. In particular, the photocatalytic degradation of Bisphenol A (BPA) under visible irradiation (laser source and LED) was demonstrated. The experimental investigations have shown extremely fast and complete photodegradation of BPA in water after only 12 min [8]. References: [1] Matthew E. Stewart, Christopher R. Anderton, Lucas B. Thompson, Joana Maria, Stephen K. Gray, John A. Rogers, and Ralph G. Nuzzo, Nanostructured plasmonic sensors, Chem. Rev. (2008), 108, 494?521 [2] Guillaum Baffou, Romain Quidant, Thermo-plasmonics: using metallic nanostructures as nano-sources of heat, Laser Photonics Rev. (2013), 2, 171?187. [3] Peng Wang, Baibao Huang, Ying Dai, and Myung-Hwan Whangbo, Plasmonic photocatalysts: harvesting visible light with noble metal nanoparticles, Phys.chem. (2012), 14, 9813-9825. [4] Guillaume Baffou and Romain Quidant, Nanoplasmonics for chemistry, Chem. Soc. Rev. (2014), 43, 3898-3907. [5] Guillaume Baffou, Romain Quidant, and F. Javier Garcia de Abajo, Nanoscale Control of Optical Heating in complex plasmonic systems, J. Am. Chem. Soc. (2010), 4, 709-716. [6] Shaunak Mukherjee, Florian Libisch, Nicolas Large, Oara Neumann, Lisa V. Brown, Jin Cheng, J. Britt Lassiter, Emily A. Carter, Peter Nordlander, and Naomi J. Halas, Hot Electrons Do the Impossible: Plasmon-Induced Dissociation of H2 on Au, Nano lett. (2013), 13, 240-247. [7] Feng Wang, Chuanhao Li, Huanjun Chen, Ruibin Jiang, Ling-Dong Sun, Quan Li, Jianfang Wang, Jimmy C. Yu, and Chun-Hua Yan, Plasmonic Harvesting of Light Energy for Suzuki Coupling Reactions, J. Am. Chem. Soc. (2013), 135, 5588?5601. [8] Zeinab Chehadi, Nadeen Alkees, Aurélien Bruyant, Joumana Toufaily, Jean-Sebastien Girardon, Mickaël Capron, Franck Dumeignil, Tayssir Hamieh, Renaud Bachelot, Safi Jradi, Plasmonic enhanced photocatalytic activity of semiconductors for the degradation of organic pollutants under visible light, Materials Science in Semiconductor Processing (2016), 42,81-84.

Resume : Localized surface plasmon resonances (LSPR) in near-infrared (NIR) region have been extensively studied for copper chalcogenide nanostructures not only for the absorption enhancement but also tunable LSPR characteristics with their free carrier concentrations or defects. In the present work, one-step cation exchange method has been used to synthesize stoichiometric Cu2-xS nanowire with x varied between 0 and 1, including Cu2S, Cu7S4 and CuS etc. The plasmonic band of Cu2-xS nanowire shifts to a shorter wavelength with the increase in x, as observed in vis-NIR spectra, which is attributed to the increase in density of copper vacancies. The Cu2-xS nanowires have been applied to enhance the photocatalytic activities for the generation of H2 from ammonia borane (AB). For samples with different Cu-S compositions, Cu7S4 samples exhibit the highest activity of H2 evolution rate of (25.54 mmol/g.h). Moreover, a strong enhancement of H2 evolution rate (157.04 mmol/g.h) could be achieved after Cu2-xS nanowires were decorated by Pd nanoparticles to form the hybrid structure. The results of present investigation may lead to an effective strategy for the design and development of LSPR materials for photocatalytic applications.

Resume : The interaction between nanometer-sized metallic structures and electromagnetic radiation in the visible or near-infrared frequency range generates very fast plasma oscillations and can lead to localized surface plasmon resonances (LSPRs) when the frequency of the incident field is properly tuned. LSPR have been widely demonstrated and investigated for nanoparticles isolated or embedded in dielectrics. New opportunities for plasmonics and biosensing are offered by novel hybrid heterojunctions combining, semiconductors, graphene and metals. In those hybrids, graphene activates interfacial charge transfer, metal nanoparticles, in turn, activate the plasmonic electromagnetic coupling of light. In order to design these hybrid platforms to take advantage of applications exploiting interfacial charge transfer, we need to better understand the optical and electronic phenomena at interfaces of those hybrids. In this contribution, we present extensive optical characterisation using ellipsometry and magneto-spectroscopy, from the infrared to visible and ultraviolet range, to describe phenomena arising from coupling wavelength-resolved light into various heterojunctions based on plasmonic metals from NIR to UV (Au, Ag, Ga, Al, ..) coupled to semiconductors (Si, GaAs, ..) and graphene. We show hybrids that can extend plasmonic applications to THz and UV ranges and that can exploit charge transfer at interfaces to enhance or quench or shift the frequency of the plasmon resonance providing a fully tunable plasmonic platform. Experimental pectroscopic data will be corroborated by simulations by FEM and RWCA (rigorous wave coupled analysis). We aknowledge the contribution of the H2020 European programme under the project TWINFUSYON (GA692034)

Resume : Tip Enhanced Raman Scattering (TERS), a technique that provides molecular information on the nanometer scale, has been a subject of great scientific interest for 15 years. But regardless of the recent achievements and applications of TERS, ranging from material science and nanotechnology, strain measure-ment in semiconductors, to cell biological applications, the TERS technique has been hampered by extremely long acquisition times, measured in hours, required for collection of reasonably high pixel density TERS maps. In this talk, specifics of the TERS setup that enable fast, high pixel density nano-Raman imaging will be discussed: The innovative integration of technologies brings high-throughput optics and high-resolution scanning for high-speed imaging without interferences between the techniques. The latest developments in near-field optical probes also provide reliable solutions for academic and industrial researchers alike to easily get started with nanoscale Raman spectroscopy. Thanks to those latest instrumental de-velopments, we will present the nanoscale imaging of nanopatterned flakes of graphene and graphene oxide, carbon nanotubes and exfoliated MoS2 flakes with a spatial resolution routinely obtained in TERS maps in the 15 - 20 nm range and a best resolution achieved being of 7 nm.

Resume : Active plasmonic nanomaterials are of interest in a variety of device applications ranging from solar cells to optical sensors. An important aspect of optimising plasmonic nanomaterials for, e.g., optical sensor applications is the ability to engineer areas of intense, localised electromagnetic fields. Here, the formation of microscale arrays comprising Au nanoparticles created by photodeposition on a periodically proton exchanged ferroelectric lithium niobate (PPELN) crystal is demonstrated. This PPELN template affords the ability to tailor the electrostatic fields near the surface of LN crystals to engineer the formation of the patterned Au nanostructures (Au-PPELN). The Au-PPELN substrate provides a platform for ultra-sensitive Raman spectroscopy at the single molecule level detection limit. The acquired optical images show the presence of localised blinking. Temporal and spectral acquisitions of blinking events have been recorded individually using high-speed detectors and a high-resolution spectrometer, respectively. The obtained spectra indicate that the observed blinking can be assigned to single molecules. This finding opens opportunities to use Au-PPELN substrates for ultrasensitive characterization in the fields of biophysical and biomedical spectroscopy.

Resume : Recently metal oxides have been introduced as promising materials for infrared and active plasmonics. By designing nanoantennas and metamaterials using transparent conducting oxides, we can achieve strong light-matter interactions in the infrared while maintaining high transparency in the visible range. Next to plasmonic nanomaterials with tunable properties by design, efficient and reversible control of plasmonic modes at visible and near-infrared wavelengths will allow new tunable devices for control of local hotspots or plasmonic switches. In recent studies, we have investigated how local field enhancement around a nanoantenna can be used to drive an optical nonlinear material. As the nonlinear medium, indium-tin-oxide was shown to provide a large nonlinear response. An ultrafast hybrid nonlinearity can be designed where the antenna assists the nonlinear substrate through the strong optical near-fields and also enhances the readout of the nonlinear response. Phase-change materials offer another technologically relevant opportunities as they can provide very large changes in the dielectric response. We have successfully demonstrated ultrafast phase changes in a plasmonic antenna - VO2 hybrid. The phase change response is fully reversible over >1 million cycles per second, opening new avenues for ultracompact and low energy transistor-type optical switches.

Resume : We use boundary element method simulations to simulate the effect of varying the length of a gallium phosphide nanorod. The structure used is a cylindrical rod with hemispherical end-facets. This is considered as a simplification of crystalline morphologies and, by varying length of the cylindrical section, allows a continuous transition form a sphere to an semi-infinite cylinder. Our results show a continuous transition between previously established regimes: that of the spherical Mie resonances and the leaky-mode resonances of a sphere. The intermediate regime is found to consist of two dimensional Fabry-Perot modes, dependent on both the length and diameter of the nanorod. We further this investigation by placing two nanorods end-to-end to form a dimer structure. While this has little effect on the scattering spectra, such structures are capable of producing large electric field enhancement and magnetic field suppression. For certain antenna resonances, we see as much as a 300-fold electric field intensity enhancement for an interparticle spacing of 20 nm. This is comparable to some plasmonic structures. Alternatively, it is possible to achieve almost complete quenching of the magnetic field. This study is concluded by looking at the angle dependence of the excited modes. It is found that normal or grazing incidence excites odd order cavity modes, whereas light incident at 45o is able to excite even order modes. In addition to this work, we have investigated the effect of phase change materials on the resonances of plasmonic antenna. Our group has studied techniques to deposit thin layers of vanadium dioxide (VO2) with very uniform thickness. On top of this we are able to deposit small gold antenna structures via e-beam lithography. While our group has previously published results taken from antenna arrays, we are now able to take single particle measurements. Using spatial modulation, we measure the how the reflected spectra of a single gold nanorod and gold dimer antenna are modified when the substrate is changed from a dielectric to a metallic material. We observe a strong blue shift in the antenna resonance when the sample his heated to 80oC with a strong hysteresis effect. The next step is use pump-probe spectroscopy to attempt to achieve this switching optically on an ultra-fast time scale.

Resume : Plasmonic nanostructures enable control and manipulation of light at deep subwavelength scales. However, its ohmic losses lead to temperature increase in the metal and surroundings. This effect is well known and some applications take advantage of it, such as photothermal imaging or cancer therapy. However, for other applications, it is detrimental as it strongly limits the power that can be delivered to a hot spot before the particle reshapes or melts, affecting its nanoscale lighting, the CMOS integration of current plasmonic devices or the emission properties of molecules placed near the nanoantennas. Another limitation of metals is the difficulty to generate optical magnetic response. Recently, the use of low-loss resonators made of high-permittivity dielectric materials, has shown to be efficient in enhancing the interaction of light with molecules. Here we present how non-plasmonic nanoantennas can produce both, high surface enhanced fluorescence, and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments. We also show another key aspect of these nanoantennas, which is the possibility of exciting nanoscale displacement currents which can induce magnetic response in them. This can allow the tuning of the amplitude and phase difference of the electric and magnetic resonances independently, so that they can arbitrarily interfere to direct the light towards a desired direction.

Resume : The dye-sensitized B-doped diamond exhibits stable cathodic photocurrents under visible light illumination in aqueous electrolyte solution with dimethylviologen serving as electron mediator. To enhance the dye loading, nanotextured diamond foam is used instead of flat films. The dyes are anchored to a H-terminated diamond surface either non-covalently (with polyethylene imine linker) or covalently through a combination of diazonium electrografting and Suzuki cross-coupling reactions. The electrodes are tested for application in p-type dye-sensitized solar cells. Photocurrents under solar light illumination (AM 1.5) are about 3-times larger on foam electrodes compared to those on flat diamond, which is prepared with the standard chemical-vapour deposition. Illumination of the sensitized foam electrodes with chopped light at 1 sun intensity causes an increase of the cathodic photocurrent density to ca. 15-22 μA/cm2. Photocurrent densities scale linearly with light intensity (between 0.1 a 1 sun), and they represent the largest values reported so far for dye-sensitized diamond electrodes. The photoelectrochemical activation of the sensitized diamond electrodes is accompanied with characteristic changes of the dark voltammogram of the MV2+/MV+ redox couple and with gradual changes of the IPCE spectra. This work was supported by the Grant Agency of the Czech Republic (contract No. 13-31783S).

Resume : Perovskite materials have attracted much attention in the last years due to their interesting optical properties and possible application for low-cost photovoltaic devices. Cesium lead halide (CsPbX3, X=Cl, Br, I, Cl/Br and Br/I) nanocrystals (NCs) are of interest because they combine the advantageous properties of perovskites and quantum dots. Colloidal CsPbX3 are known to reach photoluminescence (PL) quantum efficiencies up to 90%[1]. By changing the composition and the NC size, the emission wavelength can be precisely tuned, being able to cover the whole visible region of the spectrum. For future applications in optoelectronics and photovoltaics, an efficient energy and/or carrier exchange is a necessary condition. In this study we synthesize CsPbBr3 colloidal NCs and identify the Förster resonant energy transfer (FRET) between them for the first time, proceeding from small to large NCs[2]. We show that the energy transfer can be driven by the concentration gradient of excited NCs as well as by the bandgap energy difference. The evidence of the energy transfer has been derived from PL spectral and temporal modifications upon mixing of two colloids of NCs with different sizes. The observed energy transfer is enabled in the colloids by proximity of individual nanocrystals due to clustering. [1] L. Protesescu et al. Nano Lett. 2015; 15: 3692 – 36962 [2] C. de Weerd and L. Gomez et al., currently under review

Resume : Optical gain in an ensemble of semiconductor nanocrystals is usually difficult to reach because multi-excitons efficiently decay by non-radiative Auger process. Therefore we examine theoretically the conditions required to obtain optical gain in the single-exciton regime, which is very attractive for low-threshold laser applications. We show that the electron-phonon interaction can play a very positive role, in addition to the exciton-exciton interaction. In that situation, the optical gain regime can be reached even when the population of nanocrystals containing single excitons is below 10%. On the basis of these results, we propose that ultra-small nanocrystals, or nanocrystals with deep defects at their surface, could be promising materials for light amplification.

Resume : Fluorescent nanodiamonds (FNDs) represent a key component in recent development of ultra-high precision optical resolution techniques. FNDs can accommodate nitrogen-vacancy (NV) centers ? an extremely photostable crystal lattice defect emitting in near-infrared region. Electron transitions among NV quantum states can be influenced by very weak external electric or magnetic fields, which have been utilized for construction of various types of probes and nanosensors. Utilization of these particles in sensing will be demonstrated as well as chemical aspects infuencing interactions at their surface.

Resume : The machining of templates in photoresist layer, for applications such as Diffractive Optical Element (DOE) manufacturing, is generally obtained by a non-linear absorption process taking place at the laser/material interface thanks to high power, ultra-short pulsed lasers. These lasers are nonetheless still expensive, thus making the process still costly. Thanks to recent advances in photonic nanojet, cheap low power, continuous wave lasers can now be used to process materials with of accuracy and resolution comparable, if not higher, than with expensive ultra-short pulsed laser. Successful machining of SU8 photoresist was obtained using a 514 nm continuous wave pigtail Coherent Obis laser connected to a fibre with a shaped tip combined with a Nanocube XYZ high-accuracy Compact Multi-Axis Piezo System for Nanopositioning. The surface functionalisation was performed bby focusing the laser beam out of a SM450 optical fibre with a 1.2 µm tip length and a shape described by a rational Bezier function of weight 0.2, giving a theoretical FWHM of ?/2 and a Rayleigh range of 2? can be obtained. The SU8 was developed and its profile was characterised by white light scanning interferometry, AFM and SEM. These encouraging results prove that sub-wavelength laser manufacturing of DOE in SU8 can be achieved, opening the way to rapid prototyping of high precision and low cost DOEs.

Resume : Porous nanostructured photonic materials in the shape of periodic multilayers have demonstrated their potential in different fields ranging from photovoltaics [1] to sensing [2]. On the one hand their porosity makes it feasible to infiltrate them with an electrolyte or a polymeric matrix (which allows their use in dye sensitized solar cells or as flexible films [3]). On the other, the possibility of controlling their refractive index profile via their nanostructure or the choice of materials, strongly affects the way light is transported or generated within them. When applications dealing with light absorption or emission are considered, knowledge on how the local density of states (LDOS) is distributed within them is mandatory [4] in order to realize a judicious design which maximizes light matter interaction. In order to do so, access to a photonic probe which senses the LDOS at different spatial positions is desired. Such probe must have reduced dimensions (in order to achieve a high spatial resolution in the mapping of the LDOS) and should lend itself to be incorporated in the fabrication procedure in such a manner that its spatial position within the sample can be controlled. We report a detailed study of how dye doped polystyrene nanospheres constitute an effective LDOS probe to study the local photonic environment within nanostructured photonic media [5]. Nanospheres (with a diameter of 25 nm) are incorporated at different stages of the fabrication procedure of nanostructured photonic multilayers (through a combination of spin and dip-coating with suspensions of oxide nanoparticles) so that they can be placed at several positions of the structured sample. A combined use of photoluminescence spectroscopy and time resolved measurements are used to retrieve information on field intensity as well as LDOS distribution within the structures. Information on the local photonic environment is obtained with a spatial resolution of 25 nm (provided by the probe size) and relative changes in the decay rates as small as ca. 1%, evidencing the possibility of exerting a fine deterministic control on the photonic surroundings of an emitter. Beyond probing the LDOS in these photonic architectures, the possibility of maximizing light-matter interaction by combining them with metallic structures is explored. References [1] C. López-López, S. Colodrero, M. E. Calvo and H. Míguez, "Angular Response of Photonic Crystal Based Dye Sensitized Solar Cells", Energy Environ. Sci. 23, 123902 (2013). [2] A. Jiménez-Solano, C. López-López, O. Sánchez-Sobrado, J. M. Luque, M. E. Calvo, C. Fernández-López, A. Sánchez-Iglesias, L. M. Liz-Marzán and H. Míguez, “Integration of Gold Nanoparticles in Optical Resonators”, Langmuir 28, 9161 (2012). [3] J. R. Castro-Smirnov, M. E. Calvo and H. Míguez, “Selective UV Reflecting Mirrors Based on Nanoparticle Multilayers”, Adv. Funct.Mater, 23, 2805 (2013). [4] N. Danz, R. Waldhäusl, A. Bräuer and R. Kowarschik, “Dipole Lifetime in Stratified Media”, J. Opt. Soc. Am. B, 19, 412 (2002). [5] A. Jiménez-Solano, J. F. Galisteo-López and H. Míguez “Fine Tuning of the Emission Properties of Nano-Emitters in Multilayered Structures by Deterministic Control of their Local Photonic Environment”, Small 11, 2727 (2015) (Cover story).

Resume : The presence of internal electric fields in quantum confining structures, like quantum wells and discs (QDiscs), has a major effect on their optical properties. Indeed, upon excitation, additional carriers, in out of equilibrium conditions, will partially screen the electric field within the QDisc. This causes a reduction of the quantum confined Stark effect (QCSE) and shifts energy levels towards higher energies, depending on the carrier concentration. Cathodoluminescence (CL) in a Scanning Transmission Electron Microscope (STEM) allows the deployment of very local excitation probes and the assessment of single QDiscs.[1,2] Here we show a direct observation of very local emission of light from single GaN QDiscs formed between AlN barriers in the growth axis of GaN nanowires. Indeed, due to the height of AlN barrier, the diffusion length of carriers is as short as about 5 nm in this system.[2] Moreover, we show that the internal field can be screened by CL-generated charge carriers inside these QDiscs. CL spectral imaging with nanometre resolution tracks the emission of QDiscs as function of the electron probe position, allowing the creation of different concentrations of carriers in QDiscs. It is then possible to study energy shifts in individual QDiscs by observing different emission rates.[3] [1] L. F. Zagonel et al. Nano Lett. 11 (2011) p. 568. [2] L. F. Zagonel et al. Nanotechnology 23 (2012) 455205. [3] Acknowledgements: FAPESP funding 2014/23399-9.

Resume : Plasmonic optical antennas are receiving a large interest to interface light with molecules on dimensions much beyond the optical wavelength. A specific design called antenna-in-box has been developed for the enhanced detection of single fluorescent molecules in solutions at high concentrations, reaching detection volumes down to 58 zL (four orders of magnitude smaller that the diffraction limit) and large enhancement of the single molecule ?uorescence, up to 1100-fold [1]. Thanks to their ability to control and manipulate optical fields down to the nanometre scale, it is appealing to use plasmonic antennas to enhance the energy transfer between single quantum emitters. Energy transfer between molecules is an essential phenomenon for photosynthesis, photovoltaics and biotechnology. We have recently demonstrated enhanced energy transfer within single donor-acceptor fluoro-phore pairs confined in single gold nanoapertures [2]. Here we investigate the nanogap antenna between two metal nanoparticles to reach strong intensity and LDOS enhancement [3]. Our experiments monitor both the donor and the acceptor emission photodynamics on single donor and acceptor quantum emitters attached on a double stranded DNA linker. Our results establish that nanophotonics can be used to intensify and control the near-?eld energy transfer. References [1] D. Punj, M. Mivelle, S. B. Moparthi, T. van Zanten, H. Rigneault, N. F. van Hulst, M. F. Garcia-Parajo, J. Wenger, A plasmonic ?antenna-in-box? platform for enhanced single-molecule analysis at micromolar concentrations, Nature Nanotech. 8, 512-516 (2013). [2] P. Ghenuche, J. de Torres, S. B. Moparthi, V. Grigoriev, J. Wenger, Nanophotonic Enhancement of the Förster Resonance Energy-Transfer Rate with Single Nanoapertures, Nano Lett 14, 4707-4714 (2014). [3] P. Ghenuche, M. Mivelle, J. de Torres, S. B. Moparthi, H. Rigneault, N. F. Van Hulst, M. F. García-Parajo?, J. Wenger, Matching Nanoantenna Field Confinement to FRET Distances Enhances Förster Energy Transfer Rates, Nano Lett 15, 6193-6201 (2015).

Resume : The optical properties of silver metal nanoparticles are dominated by the excitation of localized surface plasmons. Light incident on silver particles with spherical shape and diameters below 100 nanometers excites primarily the dipolar mode. The higher-order modes, i.e., modes with larger angular momentum l, such as the quadrupole mode, are strongly damped as their larger resonance energy tend to be positioned in the range of interband transitions in silver. By encapsulating silver nanospheres in a high permittivity dielectric medium, in this work silicon nitride, we redshift all of the plasmon modes and thereby get access to the higher-order modes of silver nanoparticles. We map the dipolar and higher-order modes of individual silver nanoparticles with electron energy-loss spectroscopy in a state-of-the-art transmission electron microscope. For particle radii smaller than 4 nanometers, we observe a strong blueshift of the dipolar mode of 0.9 eV and a strong damping of the higher-order modes in qualitative agreement with a generalized nonlocal optical response theory. We discuss the influence of these higher-order modes on the optical properties of few-nanometer silver nanoparticles probed by electron beams as done routinely in electron energy-loss spectroscopy experiments and on single silver nanospheres coupled to dipole emitters such as single atoms or molecules.

Resume : Mixing metals at the nanoscale to obtain alloy nanostructures with tailored physicochemical properties offers appealing opportunities in catalysis and solid state devices. The precise control of the alloy composition in nanoparticles and the batch-to-batch reproducibility is often limited in colloidal synthesis methods, with a few exceptions [1]. To address this deficiency, we introduce a generic nanolithography-compatible strategy to fabricate arrays of supported alloy nanoparticles with fine-tuned composition [2]. Our approach is based on automated layer-by-layer physical vapor deposition of alloy constituents through a nanofabricated mask and subsequent annealing. We demonstrate the nanofabrication of large (cm^2) area arrays of nanoparticles of binary and ternary Au alloy with Ag, Cu and Pd. We characterize in detail the nanoparticles by electron microscopy and energy-dispersive X-ray spectroscopy and we find their composition to match the nominal one with excellent precision. Then, we characterize and discuss their plasmonic properties. The possible combination of spectrally tunable plasmonic characteristics and tailored chemical properties for a specific targeted function [3] promises to have a significant impact in applications such as plasmonic gas sensing, metamaterials and plasmon mediated catalysis. References: [1] Dallaire, A.-M.; Rioux, D.; Rachkov, A.; Patskovsky, S.: Meunier, M. J. Phys. Chem. C 2012, 116, 11370–1137. [2] Nugroho, F. A. A.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Submitted for publication. 2015. [3] Wadell, C.; Nugroho, F. A. A.; Lidström, E.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Nano Lett. 2015, 15, 3563–3570.

Resume : Quantum-confined systems and nanoscale resonators are fundamental components of advanced nanomaterials. The former, including quantum-dots and nanowires, are efficient light emitters with tunable electronic states. The latter, including plasmonic and dielectric nanoparticles, allow for extreme light localization and modification of the photonic density of states. Here, we design and fabricate a metamaterial combining silicon nanocrystals (Si-NCs) and silica nano-resonators for solar energy down-conversion. Si-NCs with size smaller than the Bohr radius show quantum confinement effects, and have been demonstrated to support the generation of multiple excitons in separated but proximal Si-NCs, upon the absorption of a single photon. The practical utilization of Si-NCs is limited by their low absorption cross-sections and by the long emission lifetimes. In order to address these issues, we design and fabricate a metamaterial made of Si-NCs embedded in silica nanopillars, which support Mie-type electromagnetic resonances. We characterize the optical properties of the metamaterial by spectrally- and temporally-resolved photoluminescence measurements, demonstrating that it is able to localize photons, and to enhance the photoluminescence of the Si-NCs. Currently, an enhancement of 200% has been achieved. These results represent a promising route to increased solar conversion efficiency in quantum-dot-based cells.

Resume : Metal nanoparticles (M-NPs) are suitable to be integrated in silicon based solar cells due to their unique optical and electrical properties which are very different from those of bulk material. Illuminated by light, M-NPs can exhibit localized surface plasmon resonance (LSPR) caused by the collective oscillations of the conduction electrons. This behavior results in a strong optical scattering by multiple and high angle scattering and a strongly enhanced optical near field in the close vicinity of nanoparticles. Different characteristics can influence the LSPR of these particles, such as the NP shape and size, surrounding medium and dielectric spacer layer. Tuning the LSPR characteristics can lead to interesting properties in terms of enhancement, localization and guiding of the electromagnetic field. In particular, the effect of underlying spacer layer on the LSPR has attracted a great deal of attention. In this contribution, we attempt to investigate the effect of a dielectric spacer layer on the optical properties induced by Ag-NPs. We use numerical simulation (FDTD) to evaluate the presence of the dielectric layer (TiO2) with different thicknesses on the LSPR and the scattering cross section. It is revealed that for particles of certain size, a preferable dielectric spacer thickness is desirable to achieve a significant reduction of reflectivity which can be useful in solar cells.

Resume : Surface plasmon polaritons have been proposed in several solar cells architectures as a way to enhance light collection and thus increase the efficiency of the solar cells. In the case of photon conversion systems (downshifting, downconversion), metallic nanoparticles (nps) coupled to the emitting elements (Si nanocrystals, rare earth elements, …) were proposed as a way to increase the quantum yield of the photon conversion. Experimentally, several techniques were used to obtain Ag particles of size ranging from 6 nm to 200 nm, embedded into a SiON antireflective layer. One of the techniques, that will be presented, is based on an electroless deposition technique, which allows the control of the size of the Ag nps. The plasmonic effects are modelled using the rigorous Lorenz-Mie theory as a function of np size, SiON refractive indexes and incident wavelengths. The plasmonic resonances is observed experimentally with a good agreement with theory. From the comparison between scattering and absorption efficiency, it is found that Ag nps larger than 30 nm mainly contribute to light scattering (green-red light), whereas Ag nps smaller than 15 nm absorb light (blue-green). From the study several engineering rules are established for the use of Ag nanoparticles in a SiON antireflective coating depending on the application.

Resume : Illuminating thin film semiconductors above their optical band-gap may result in interesting phenomena. We report here ?random lasing? (RL) arising from interaction between a quadrupled NdYAG laser and crystallized semiconductor films. If many works have been done on the archetypical case of ZnO films (structure, influence of the crystallite size, growth temperature?) no experience and model on RL of GaN in thin films are available for optical pumping schemes. The energy deposition by the pumping beam injected in films is investigated using quantum many-body theory: Frequency dependence of the refractive index and absorption coefficient are obtained for different carriers densities. Results are analysed regarding the experimental data obtained from time resolved high-resolution photoluminescence measurements. Both resonant and non-resonant feedback theories of RL in semiconductor thin films are discussed.

Resume : Surface coating is a commonly used strategy to enhance upconversion emissions by shielding the luminescent core from surface quenching. In this work, we provide insights into the effect of surface coating on upconversion by investigating NaYF4:Yb/Er nanoparticles and the corresponding NaYF4:Yb/Er@NaYF4 core–shell nanoparticles, as a function of dopant concentration of Yb3+ and excitation power. We observe declining emission enhancement factors with decreasing Yb3+ concentration and increasing excitation power. Our mechanistic investigations suggest that the phenomenon originates from stepwise excitation in the upconversion process, as well as energy hopping among the Yb3+ dopants. This increased understanding of the effect of surface coating on upconversion should be important towards the rational design of lanthanide-doped core–shell nanoparticles for various applications.

Resume : Surface plasmons at metal/dielectric interface can resonate with the incident light depending on the refractive index (RI) of the medium, the incident angle or wavelength of the light. These characteristics have been utilized as a basis of surface plasmon resonance (SPR) sensors, providing label-free and real-time sensing format. However, the sensitivity of SPR sensors still needs to be improved to meet the requirements for the small molecule sensing. In order to enhance the performance, plasmonic nanomaterials have been introduced on SPR sensor chip. Dirac fermions in graphene behave like photons showing linear dispersion relation. In this regard, graphene can be utilized as an alternative plasmonic material to conventional metal nanostructure. Herein, we employed graphene oxide (GO)-coated Au substrates with the aim to increase electric field through coupling of graphene plasmons with propagating SPs from Au film. Thickness, reduction state and nitrogen doping state of GO were systematically controlled and RI sensing was conducted. GO/Au substrates showed higher RI sensitivity (RIS) compared to bare Au film and the figure of merit of GO/Au samples was not deteriorated due to the extremely thin graphene layer. Immunosensing was demonstrated with the mass sensitivity of 1430 pg/mm^2, 3.3 times higher than that of bare Au film. Therefore, GO adlayers could amplify near-field and biomolecular adsorption which was experimentally proved by monitoring RIS and immunoassay.

Resume : Crystalline NaYF4 microstructures are harnessed to realize directional emissions by near infrared excitations through photon upconversion. By incorporating lanthanide ions of varying composition and concentration into the microcrystals, guided emissions of tunable colors (blue, green, and red) are achieved by near infrared excitations at diverse wavelengths (808−1532 nm).

Resume : For the rational design and fabrication of novel nanostructures, we present a new approach to generating arrays of three-dimensionally controlled, stacked nanostructures by exploiting light-matter interaction. To create controlled three-dimensional (3D) nanostructures, we utilize the 3D spatial distribution of light, induced by the light-matter interaction, within the matter to be patterned. As a systematic approach, we establish 3D modelling that integrates the physical and chemical effects of the photolithographic process. Based on a comprehensive analysis of structural formation process and nanoscale features through this modelling, we are able to realize three-dimensionally controlled nanostructures using facile photolithographic process. Here we first demonstrate the arrays of three-dimensionally controlled, stacked nanostructures with nanoscale, tunable layers. We expect that the promising strategy would open new opportunities to produce the arrays of controllable 3D nanostructures using more accessible and facile fabrication process for various applications ranging from metamaterials to biosensors.

Resume : In recent years, growth and study of noble metal nanoparticles (NPs) exhibiting plasmonic resonances have received great importance for fundamental as well as technological interest. Peak position of this resonance senses the refractive index of the environment of the noble metal NP, and thus plasmonic spectroscopy is able to detect biomolecules that are bound to the metal NP. In this work, nanostructured regions were produced by single-pulse homogenous laser irradiation (λ=193 nm, τ=20ns) of an Au discontinuous films. Upon melting, irradiated regions are transformed into spherical NPs, thus optical extinction of this regions are characterized by the plasmonic resonance related to the NPs. As constant laser fluence, morphology of the NPs and thus the plasmonic response is determined by the initial Au thickness. As a proof of concept, we use these nanostructured regions as a biosensing platform for the determination of the immunosuppressant tacrolimus (FK506). The surface was activated with amino groups using poly-L-lysine 0.1 % (v/v) and a carboxylated derivative of tacrolimus (FK506-COOH) was subsequently immobilized via carbodiimide chemistry (100 µg/mL FK506-COOH, 100 mM EDC and 50 mM NHS in MES buffer). The measuring principle was based on an affinity assay between the antigen FK506-COOH, immobilized onto the sensing area, and the specific IgM antibody anti-FK506 (5 µg/mL in PBS) that was incubated for 4 h. Unbound antibodies were removed by rinsing 3x 0.4 mL of PBS (supplemented with 0.5% (v/v) Tween 20 and 0.3 % (w/v) defat milk). Extinction spectra show a clear red-shift of the plasmonic response in the regions exposed to the anti-FK506 antibodies, and this shift increase with the initial Au thickness. Acknowledgments: European Union under the program FP7-ICT-2011-8(contract no. FP7-318372 “NANODEM”; http://nanodem.ifac.cnr.it/), as well as the Spanish MINECO (grant no. CTQ-2012-37573-C02 and JCI-2012-13034).

Resume : Recently, perovskites attract considerable attention as possible materials for future photovoltaics due to their strong absorption, attractive bandgap energies, high mobilities and low production costs. Here, we synthesize and investigate a monodisperse colloidal nanomaterial of fully inorganic cesium lead halide (CsPbBr3) perovskites using inexpensive commercial precursors. These all-inorganic perovskite nanocrystals (NCs) feature tunable bandgap energies and emission spectra, short radiative lifetimes and high photoluminescence quantum yields, making them attractive for many applications. Since processes of essential importance for many applications occur on ultrafast timescales, we have also investigated the carrier dynamics in detail using a pump-probe transient induced absorption (IA) setup. Particular focus is placed on Auger recombination of excitons. Compared to bulk, the efficiency of this process is considerably increased in NCs due to the enhanced Coulomb electron-electron coupling. We investigate the Auger process under conditions of strong pumping, when it limits the emissivity of multiple excitons in the same NC. By measuring IA transients and spectra under several pumping conditions, we determine the Auger recombination time as function of the NC size and exciton multiplicity. We compare the obtained time constants with those of Auger processes in NCs of other semiconductors. These results offer insight into the ultrafast processes and their mutual competition occurring in all-inorganic perovskites.

Resume : Studying nanoparticles for catalytic applications in situ is a challenge because their working environment is often harsh in terms of temperature, pressure and chemical reactivity. Nonetheless, the ability to study the chemistry of nanoparticles while reactions occur in or around them is of great interest in many fields, including heterogeneous catalysis, and indirect plasmonic sensing (INPS) has shown to be an effective strategy for this purpose. Nevertheless, INPS experiments are still hampered by the fact that, for instance, sample temperature changes (e.g. due to dissipated reaction heat or in transient experiments) can affect the measured plasmonic parameters and induce unwanted signals that complicate ambiguous measurements. To conceptually address this issue, we have previously demonstrated a method that utilizes indirect plasmonic sensing on specifically tailored asymmetrical heterodimers consisting of a symmetrical inert sensor paired with a smaller reactive particle[1]. By monitoring the structures using two probing light polarizations simultaneously, changes in the small reactive particle can be effectively singled out and drift as well as temperature-induced plasmon shifts can be efficiently eliminated. The reason for this is the near-field coupling that occurs between nanoparticles placed close to each other when light polarized along the dimer long axis is applied. The fabricated structures are therefore dichroic and changes occurring in the small reactive particle adjacent to the inert element in the dimer are only detectable in the polarization parallel to the dimer axis. In this study oxidation and reduction of Cu nanoparticles has been studied in situ using plasmonic sensing both by directly monitoring the spectra of pure Cu structures and indirectly by monitoring the Cu particles using an inert Au sensor placed beside the reacting Cu particle. The reactions have been studied in a temperature range of 20-300°C, and in different gas concentrations. Using direct sensing there is a dramatic change in the plasmonic spectra when the particle oxidizes, however, the measured spectrum is also affected by changes in temperature which motivated us to use the indirect measuring scheme presented above. Using INPS we find that changes in the plasmonic response obtained from the Au-Cu dimers’ simultaneously monitored orthogonal polarization readouts stem from several contributions, including temperature changes, spill-over processes to the support, and the targeted oxidation of the Cu. Using the difference between the two polarization direction signals, however, we can then elegantly single out the sensor response stemming exclusively from the Cu oxidation and reduction process. The optical response of the Cu disks and the Au-Cu dimer system has then been compared with corresponding FDTD simulations that have shown good correlation. We will also report on our progress of applying the above strategy at the single nanoparticle level, to further expand the possibilities of single particle plasmonic nanospectroscopy for the characterization of catalytic processes at the individual nanoparticle level, as we recently demonstrated possible on the example hydrogenation of individual Pd nanocrystals with different size and shape[2]. Combining these two methods creates an effective analysis platform for a wide set of chemical reactions with the possibility to be both accurate and selective. 1. Wadell, C. & Langhammer, C. "Drift-corrected nanoplasmonic hydrogen sensing by polarization." Nanoscale , no. 7 (2015): 10963–10969. 2. Syrenova, S. et al. "Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape." Nature Materials, no. 14 (2015): 1236–1244.

Resume : Due to their interesting properties, silicon nanowires (SiNWs) have attracted a lot of attention, being a promising material for different applications. In this work, an easy cost-effective approach to form silicon nanowire arrays on multi-crystalline silicon (mc-Si) wafer has been successfully developed through silver assisted chemical etching method. Characterization of the formed SiNWs films were performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-Visible measurement and Raman spectroscopy analysis. We investigate the role of etching time in the enhancement of Raman signal and light trapping. The results show that the formation of the SiNWs depend greatly on the etching time. The formed SiNWs on mc-Si wafer can be used in various applications.

Resume : Over the past few decades, the optical processes associated with whispering gallery modes (WGMs) within very small spherical resonators are very attractive because of their highly promising performance in the realization of optoelectronic devices.One of the advantages of WGM oscillations is the strong coupling between confined light beam and the cavity. Owing to the total internal reflections (TIRs) of light at the circular boundary, there exists high-quality factor (Q) of WGMs, which enable low threshold microcavity lasers. In spherical microcavities whose size is several times larger than the emission wavelength, WGM lasing with a series of sharp peaks has been demonstrated. In small optical cavities with dimensions approaching the wavelength of the light, lasers with ultralow threshold and low operating power can be perceived. The coherent light generation on the nano-scale cavity has recently attracted significant attention due to numerous application in the field of lasers. Researchers have demonstrated efficient optically pumped perovskite lasing in the form of vertical microcavities, random lasing, spherical resonator, microdisck, nanoplates and nanowire laser etc… Several promising materials have been successfully identified to be highly potential in practical applications such as light emitters other optoelectronic devices. However, higher lasing threshold not only makes opto-electronic devices difficult, but also imposes fundamental limits such as auger recombination losses. In addition, it is still a challenging task to realize mode control, unidirectional and wavelength scale lasers. In this work, we focus on one-step spin coating process of mixed perovskite solution (CH3NH3I and PbI2) with different concentration for an attractive gain properties by examining the stimulated emission in SiO2 nanospheres coated glass substrate. To couple perovskite gain material into spherical resonator, SiO2 nanospheres was used as nanocavities with an average diameter from 500 nm to 170 nm achieved by Stöber process. Stimulated emission of MAPbI3 (CH3NH3PbI3) perovskite that forms naturally from SiO2 nanospheres spin-coated glass substrate was achieved. With the coupling of SiO2 nanosphere, we have observed a low lasing threshold at 3.0 µJ/cm2 and controllable laser modes. These unprecedented features cannot be found in published reports.5-8 The underlying origin of the laser with large-scale, highly intensed, controllable wavelength, narrow-linewidth (<1.5 nm) mode resonances can be realized in terms of the waveguiding and scattering media within the nanosphere network.

Resume : In this study, we have prepared nano-laminated metal-oxide/metal/metal-oxide transparent cathodes and applied to transparent organic light emitting diodes (OLEDs). To obtain high transmittance and low sheet resistance, MoO3/Ag/MoO3 nano-laminated sandwich type transparent cathode layer was prepared on glass and plastic substrates. MoO3 and Ag layer was deposited on substrates by using DC magnetron sputtering and e-beam evaporation, respectively. For optimal electrical and optical properties, the optimal thickness of each layer consists of transparent cathode was explored. When the thickness of nano-laminated cathode structure was 30/25/45, the lowest sheet resistance of 1.5ohm/sq. was obtained whereas the highest transparency of 87% in visible ray range was achieved from the thickness of 30/15/45nm. The obtained low sheet resistance and high transparency can allow effective cathode material for transparent OLEDs display and lighting system. Since there is a discrepancy between transparency and sheet resistance, trade-off should be considered for device application. Therefore, to apply transparent OLEDs, 30/25/45nm thick MoO3/Ag/MoO3 cathode layer was employed with transparency of 81% and 1.5ohm/sq. sheet resistance. We have fabricated green emission transparent OLEDs with nano-laminated cathode structure and characterized optical and electrical properties of. The fabricated green emission transparent OLEDs showed 16.7 and 42 lm/W of power efficiency emitted from top and bottom direction. Furthermore, viewing angle independent stable emission spectrum was observed which means stable spectrum can be obtained from both emission direction by using nano-laminated transparent cathode structure.

Resume : ZnGa2O4:Cr3+ is promising red persistent phosphor which is emitting lights after removing the excitation light sources. Persistent phosphors have been used to night vision field such as emergency route signage, identification markers and military markers to date. In the past few years, red to near infrared(NIR) persistent phosphors have been proposed to apply to medical imaging since their emission range is suitable to pass through the animal tissues. In this study, Bi2O3 were used as co-dopant and flux material. ZnGa2O4:Cr3+ with various content of Bi2O3 were synthesized at 800-1200 oC in air atmosphere by using the cellulose assisted liquid phase precursor (LPP) method. The prepared phosphors showed a pure ZnGa2O4 spinel phase and the red to NIR luminescence at 600-800 nm, moreover, it can be excited at visible light as well as ultraviolet range light. Bi3+ ions considerably enhanced the luminescence intensity. Cr3+ ions stabilized in the structure and furthermore, the crystallinity and particle size of the phosphors were increased with adding Bi2O3.

Resume : Zinc oxide (ZnO), an important semiconductor with a wide band gap of 3.34 eV, has been intensively studied for UV photodetectors due to its excellent optoelectronic properties. ZnO based UV photodetectors are drawing much attention for various commercial and defence technology, pollution monitoring, flame sensing, and missile plume detection. Piezoelectric and pyroelectric properties of ZnO have been further applied to boost the performance of optoelectronic devices. Recently, the fabrication of ZnO nanostructure photodetectors on polymer substrates has been stimulated interest for flexible device applications. Here, we present the demonstration of ZnO nanorod array (NRA) photodetectors (PDs) on biocompatible Au-silk protein/glass or PET substrates. The devices exhibited a low dark current in the order of pA and a high photo to dark-current ratio. The ZnO PD on Au-silk film shows a higher specific detectivity as compared to that on glass substrates due to the lower dark current. Ultrafast photodetection is achieved in PDs by light induced pyroelectric effect of ZnO. We have also fabricated and measured photoconductive properties of devices on flexible PET substrates. The flexible PDs exhibited similar performance to those fabricated on rigid glass substrates. This novel concept of ZnO NRA PDs on natural silk protein platform provides an opportunity to design bio-integrated flexible photonic devices for medical applications in near future.

Resume : Titanium dioxide nanotube arrays (TNTs) have been extensively studied during the last two decades as they show potential in various fields, such as: the removal of organic and inorganic pollutants, water splitting processes, air purification, gas sensing, sensors and solar cells. However, for some applications that is solar cells or electrochromic windows, the semitransparent TiO2 nanotubes formed on conductive substrates are highly desired. Here, we show formation and characterization of titania NTs covered with Au nanoparticles. The ordered nanotubes were obtained via anodization of sputtered 1.5 μm-thick Ti films deposited onto the FTO substrate covered previously by thin titania film acting as protective coating. Magnetron sputtering was also used in order to deposit gold onto TNTs. The structural and optical properties of obtained materials were investigated using Raman and UV-vis spectroscopies. Obtained samples exhibited semitransparence behavior that allows their application in photovoltaic or electrochromic devices. The surface morphology and cross-section were examined by SEM inspection that confirmed the nanotubes presence characterized with 0.5 µm-thick walls and length of 2.4 µm. Furthermore, electrochemical and photoelectrochemical studies were carried out and the clear impact of Au presence was shown. The National Science Centre of Poland is acknowledged for financial support via grants 2012/07/N/ST5/02139 and 2012/07/D/ST5/02269.

Resume : Now days often the goal is to use the nanoparticles as building blocks and assemble them into prescribed and complex structures in order to harvest their unique properties and implement them in novel biosensors, nanoelectronic and photonic devices. We present the experimental results of template based ordering of nanoparticles by the capillary forces using our custom deposition setup. Deposition is done by confining a droplet with suspension of particles and moving the template below the confined drop where capillary forces drive particles to assemble on predefined trapping sites. This assembly approach offers high placement precision, scalability and much higher throughput compared to methods, like geometry-induced electrostatic trapping or optical tweezers. Holographic lithography and electron beam lithography followed by the replication techniques have been employed to produce large area nanostructured templates. Large area complex patterns of nanoparticles ranging from 100 to 500 nm in radius have been successfully realized. Arrays of metallic and fluorescent particles were deposited and investigated using scanning electron microscopy, Raman scattering and UV-VIS spectroscopy. Highly ordered arrays of nanoparticles produced in this manner are expected to be applicable in localized surface plasmon resonance and surface enhanced raman scattering based sensing scenarios as well as in fluorescence microscopy.

Resume : The functionalisation of nanodiamond is a key step in furthering its application in areas such as surface coatings, drug delivery, bio imaging and other biomedical avenues. Accordingly, analytical methods for the detailed characterisation of functionalised nano-material are of great importance. This work presents an alternative approach for the elemental analysis of zero-dimensional nanocarbons, specifically detonation nanodiamond (DND) following purification and functionalisation procedures. There is a particular emphasis on the presence of silicon, both for the purified DND and after its functionalisation with silanes. Five different silylation procedures for purified DND were explored and assessed quantitatively using inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of dilute suspensions. A maximum Si loading of 29,300 μg g-1 on the DND was achieved through a combination of silylating reagents. The presence of 28 other elements in the DND materials was also quantified by ICP-MS. The characterisation of Si-bond formation was supported by FTIR and XPS evaluation of relevant functional groups. The thermal stability of the silylated DND was examined by thermogravimetric analysis. Improved particle size distribution and dispersion stability resulted from the silylation procedure, as confirmed by dynamic light scattering and capillary zone electrophoresis.

Resume : In this paper, the interaction between terahertz light and 1D/2D nanomaterials in nonequilibrium as well as in equilibrium state will be discussed. Si1-xGex nanowires (NWs) were synthesized via a Vapor-Liquid-Solid (VLS) procedure. After ultrafast optical pulses excite the sample, the transient change of the sample in the 0.2-2.6 THz frequency range was probed by THz pulses. We have measured the terahertz response of Si1-xGex NWs as a function of Ge content with ~200 fs time resolution. We will discuss the results in terms of intraband energy relaxation of photoexcited carriers and interband electron-hole recombination. Chalcogenide based compound, especially Sb2Te3 and related compounds, are suitable candidates for rewritable optical storage media and phase change random access memory. We will show the relationship between structural phase transition of {Sb(3)Te(9)}n thin film from amorphous into crystalline states and the transition of optical properties in THz range using THz-TDS(Terahertz Time Domain Spectroscopy) and OPTP(Optical Pump Terahertz Probe). From the 2-dimensional THz spectroscopy, the frequency dependent time evolution of the transient change can also be monitored as a function of delay time between the pump and the THz pulse.

Resume : Plasmonics and metamaterials (MMs) field merging the area of optics and nanoelectronics have widely researched. Silver and gold are the most conventional metals for plasmonic applications due to their negative-refractive-index in visible and near-infrared (NIR) ranges, and in addition, relatively low loss than other metals. However, these conventional metals (silver and gold) are limited by their high losses in the visible and NIR ranges and high negative real permittivity values. And the optical properties of these metals cannot be tuned. Many research groups have been studying the controlling of the optical properties of silver and gold by alloying two or more elements for applying to plasmonics and metamaterial applications. And the alternative plasmonic materials with improved optical properties over the traditional materials have been studied. In this study, we focus on the coupled nanocrystals (NCs) for plasmonic and metamaterial applications in the visible and NIR regions. We discussed the optical and electrical properties of the coupled Ag NCs and the Ag-CdSe coupled NPs with various factor such as concentrations. We manufactured the hybrid Ag NCs with CdSe NCs that were covalently linked via short ligand on surface of each NC. And the NCs metamaterial was fabricated by direct nanoimprint process in other to control optical, electronic or magnetic properties based on interaction of the constituent NCs. Experimentally, we used spectroscopic ellipsometry to determine the refractive index of coupled Ag NCs and Ag-CdSe coupled NPs. In case of the coupled Ag NPs, the real part of permittivity is considerably lower than bulk Ag as the near zero negative value. Ag-CdSe coupled NPs showed the different optical properties from Ag NCs and the tunable properties with ratio.

Resume : In the present study the capabilities of two-step synthesis method based on the processing of the stoichiometric mixture of the micropowder reagents in the electrical discharge in liquid followed by laser annealing of the resulting particles for the preparation of ternary compounds nanoparticles (NPs) were estimated. A high-voltage spark discharge between two tungsten electrodes submerged into ethanol (the peak current of the pulsed spark discharge was 60 A with a pulse duration of 30 μs) was used in our experiments. For modification of the synthesized NPs the second harmonic of the YAG:Nd3+ laser (532 nm, power density of 0.2-0.4 J/cm2) was applied. A set of discharge conditions effective to produce magnetic gadolinium germanosilicide and copper-indium diselenide NPs with a mean size in the range of 20 – 25 nm were established. The phase composition, morphology, optical and magnetic properties of the synthesized and laser-irradiated NPs were studied. It has been shown that the laser irradiation may serve as a tool to alter not only morphology but also the composition of the particles synthesized through processes of laser-induced fusion, interdiffusion and chemical interactions of the components. The synthesized materials could be promising candidates for the biomedical and photovoltaic applications, respectively.

Resume : InxGa1-xAs/GaAs structures, grown by metalorganic vapor phase epitaxy (MOVPE) at 520°C, were investigated by in situ spectral reflectance (SR), high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM). HRXRD curves are analyzed to determine the indium composition of different samples, denoted A, B, C, D and E. Reflectance three-dimensional plot as function of time and wavelength was recorded to quantify the evolution of reflectivity in the wavelength range from 400 to 1000 nm and to determine some growth parameters such us growth rates and thicknesses of InxGa1-xAs layers. Longitudinal cut through the 3D plot shows dissimilar behavior of reflectivity temporal evolution in three regions: region I (400-560 nm), region II (560-750 nm) and region III (750-1000 nm). Best simulations of reflectivity signals using the transfer matrix method (TMM) are developed to analysis the variation of optical constants spectra and the sensitivity (σSR) of incident wavelength to surface morphology of InxGa1-xAs layers. The obtained values of σSR were compared to RMS surface roughness given by AFM. A good agreement between the experimental results and the theoretical predictions was found. Keywords: InxGa1-xAs/GaAs structures; In situ spectral reflectance; refractive index; Atomic force microscopy; MOVPE. *Corresponding Author: mohamedmourad.habchi@fsm.rnu.tn

Resume : In this work the plasmonic effect and electronic characteristics of the electrode interface between nano-array of Au particles produced by pulsed laser structuring of thin Au films and the transparent semiconductor indium-tin-oxide (ITO) are reported. Samples are prepared on ITO from 5-30 nm thick Au films by UV laser pulses (fluence: 60-180 mJ/cm2). Microscope observation of the sample morphology indicates on strong dependence of the nano-array geometry (particle size, distribution and spacing) on the laser processing parameters. From FFT analysis of the particle distribution the self-organization of the produced nanostructures showing pitch dimension of about 140 nm is derived. Data obtained from temperature dependent carrier transport measurements and the absorbance spectra of the samples confirm strong correlation between the structure geometry and its electronic and optical properties. In particular, the latter one are demonstrated by a strong enhancement of the electromagnetic field due to plasmonic effect. This is confirmed by an agreement of the recorded absorbance spectra with these obtained from a half-empirical model and with field distributions from FDTD simulations. Results indicate that ITO/Au electrodes functionalized by laser nanostructuring are promising candidates for applications in areas of ultra-sensitive detection, photocatalysis and photovoltaics. The National Science Centre of Poland is acknowledged for financial support via grant 2012/07/N/ST5/02139.

Resume : A major challenge of the surface plasmon resonance (SPR) technique is the detection of small molecules (M < 200 Da) as well as very low analyte concentrations. A number of physical approaches to enhance the SPR signal have been reported including the optimization of the detection angle and temperature stabilization, the introduction of bimetallic coatings in SPR sensor chips, and the development of a differential double-wavelength method. Alternatively, the SPR signal can be enhanced by directly influencing the refractive index change upon binding reactions. Here, small particles such as nanovesicles, gold nanoparticles and superparamagnetic microparticles show great promise. Based on our expertise in nanovesicle technology, we are therefore investigating optimal vesicle characteristics for use as signal amplification system for SPR sensors. Nanovesicles are prepared using the reverse phase evaporation method encapsulating salt and sucrose solutions with a high refractive index. Current findings show that the binding of biotinylated nanovesicles encapsulating 500 mM sucrose can amplify the signal change generated by streptavidin binding to a biotinylated sensor surface up to 23-fold. Dose-response studies of streptavidin with and without nanovesicle enhancement revealed an improvement of the limit of detection from 10 nM to 320 pM with a significantly higher sensitivity of 3 mRIU (refractive index units) per logarithmic unit in the streptavidin concentration.

Resume : Lanthanide doped SrF2 core-shell nanoparticles (average size around 15 nm) are synthesized following a simple hydrothermal method[1]. The core is activated with Yb3+, Nd3+ ions and also Tm3+, Er3+ or Dy3+ ions, while the shell is doped with a high percentage of Nd3+ ions. The relative amounts of dopant ions in the core are varied, keeping Nd3+ and Yb3+ ions concentration as fixed while varying the third dopant concentration. The behavior of the upconversion emission of Tm3+, Er3+ and Dy3+ for each dopant concentration is investigated upon laser excitation in the near infrared range (980 nm or 808 nm)[2]. The effect of the third dopant on the Yb3+ and Nd3+ near-infrared emissions is evaluated by exciting the NPs with 808 nm radiation. Interesting variations of the relative emissions are found, suggesting that the third dopant affects significantly the energy transfer between Nd3+ and Yb3+ ions, therefore modifying the emission features. The possible application in the biomedical field as nanothermometers based on the near infrared emissions of Yb3+ and Nd3+ is shown[3]. Remarkable changes in the sensitivity of the nanothermometers are found for the NPs doped with different lanthanides or, in the case of same third dopant ion, with different concentrations. 1. Pedroni, M., et al., Crystal Growth & Design, 2013. 13(11): p. 4906-4913. 2. Shen, J., et al., Advanced Optical Materials, 2013. 1(9): p. 644-650. 3. Benayas, A., et al., Advanced Optical Materials, 2015. 3(5): p. 687-694.

Resume : Terahertz (THz) and infrared (IR) radiation has very interesting properties in light-matter interaction, like phonons, plasmons, intersubband transitions, even in chemical and structural analysis of materials. This is the reason why there are many efforts aiming to the development of IR and THz imaging systems. However, farfield optical imaging in this range of frequencies has diffraction-limited spatial resolution preventing applications in nano-scale material and device analysis. Scattering type scanning near-field optical microscopy (s-SNOM or apertureless-SNOM) is a valuable technique for nano-scale material characterization, in IR, THz, and optics, enabling high spatial resolution (10 nm) independently of the wavelength [1]–[4]. S-SNOM is typically based on an Atomic Force Microscope (AFM) where a focused laser beam illuminates the probe tip placed in close vicinity to the sample. This is related to the fact that a small scatter particle (in practice the AFM tip) can exhibit enhanced evanescent waves that are modified by the sample presence, and then the scattered light contains sample’s local information. Our set-up is based on the commercial NeaSNOM from Neaspec GmbH. Standard Pt-coated silicon AFM probe is illuminated with a 10μm (30THz) laser beam generated by a quantum cascade laser (QCL). The beam is divided, reflected in a reference mirror in one side and focused on the tip by a parabolic mirror in the other side. Near-field interaction between tip and sample modifies the scattered light that is collected in the far field by the same parabolic mirror and focused then, simultaneously with the beam from the reference mirror, on a liquid nitrogen cooled HgCdTe detector. Undesired background contributions are suppressed by vertical tip oscillations at a frequency Ω (~280kHz) and the demodulation of the detector signal at higher harmonics, nΩ with n>2 [5]. The main advantage with this s-SNOM setup is that we can obtain simultaneously topography and nearfield optical signals. We present our results with two samples, one of nano-scale slits (~100nm) and the other with gold nanoparticles (~15nm), under SiO2 layer. Topography and nearfield images are recorded simultaneously. In the first sample we can observe interactions and interferences of the illuminating MIR electromagnetic field propagated in the sample’s surface that cannot been see with simple AFM topography. In the other sample we can also observe the dependency between spatial resolution and tip apex size. We will also give few trends that we are exploring in order to use this technique at terahertz (THz) frequencies and the application with metamaterials to observe near-field interactions. [1] J. Wessel, “Surface-enhanced optical microscopy,” J. Opt. Soc. Am. B, vol. 2, no. 9, p. 1538, Sep. 1985. [2] B. Knoll and F. Keilmann, “Enhanced dielectric contrast in scattering-type scanning near-field optical microscopy,” Opt. Commun., vol. 182, no. 4, pp. 321–328, 2000. [3] M. B. Raschke and C. Lienau, “Apertureless near-field optical microscopy: Tip–sample coupling in elastic light scattering,” Appl. Phys. Lett., vol. 83, no. 24, p. 5089, 2003. [4] H.-G. von Ribbeck, M. Brehm, D. W. van der Weide, S. Winnerl, O. Drachenko, M. Helm, and F. Keilmann, “Spectroscopic THz near-field microscope.,” Opt. Express, vol. 16, no. 5, pp. 3430–3438, 2008. [5] R. Hillenbrand, B. Knoll, and F. Keilmann, “Pure optical contrast in scattering-type scanning near-field microscopy.,” J. Microsc., vol. 202, no. Pt 1, pp. 77–83, Apr. 2001.

Resume : The thermal projection is a surface coating process that allows the manufacture making of deposits of various functions. This process lies on the creation of a plasma and injection of a coating pouder material. During the process of interaction between particles and plasma beam, the pouder particles are accelerated in a fusion state and there crush on the material to be coated. The characteristics of particles crushing such as the crushing rate, the speed and the cooling time play an important role in the diagnosis of mechanical properties and mainly the coating adhesion. In this case, the numerical analysis is the only alterative to understand the physics involved in these phenomena. In fact, the functioning phenomena scale does not allow an efficient experimental diagnosis: cooling rate of the order of 106 k/s; mean velocity of particles 200 m/s, crushing time of the order of 1 μs. Experimental results obtained are: - Optimisation of the model parameters - Determination of the enthalpy, temperature, velocity and viscosity of the plasma jet - Building of the calculation model from experimental data on coating of the type: Al2O3-TiO2, Al2O3, Al-Ni - Modelling of the kinetics of the particle crushing. - Discussion of the optimal conditions of crushing - Determination of the rate of sprawl and the number of Reynolds in the crush of the small size particles by molecular dynamics and the finite element method. - Validation of the numerical calculations with the experimental data. Key words: Thermal projection, Al2O3-TiO2, enthalpy, Reynolds, finite element

Resume : The development of engineered biotechnological nanosystems for tissue engineering (e.g. for bone repair) or in the emerging nanomedecine field (exploiting nanoparticles for cell-based diagnostic or therapy) pushes continually to adopt novel and smart techniques which should respond to new technological challenges. Through “green laser approach” we explored, at different scale, the possibility to architecture the surface of phosphate calcium apatite biomaterials well known for thier chemical and crystallographic resemblance to bone and tooth minerals. (i) First method that addresses the problem at the nanometer scale is laser ablation in liquids. The experiments consist in a femtosecond laser focusing on a solid target placed into a vessel containing deionized water or an organic solvent. The interaction leads to ablated species which nucleate and coalesce by cooling effect in the solvent and form individualized nanoparticles. (ii) Second method is the preparation of mesoporous surfaces by laser interaction with microspheres. In the experiment, a self-assembled monolayer of microspheres is prepared on the surface. When illuminated with pulsed lasers, the light is focused underneath each sphere leaving behind a well ordered array of submicrometer holes. (iii) Finally, to structure the surfaces at the micrometer scale, we use conventional laser micromachining. However, we use Bessel-like beams that make possible the writing of ultra-high aspect-ratio structures with high-resolution while suppressing the need for precise positioning of the target. Laser approach open new way to elaborate controlled and calibrated architecture surfaces at different scale level and potentially shed some more light on fundamental questions concerning the bioactivity of synthetic materials in biological media and their biointegration.

Resume : Electrically active native point defects (NPD) often, directly or indirectly controls the optical and electrical properties of oxide based semiconductor nanostructures[1]. The reduced dimensionality further influencing the defect density and their population at the surfaces. Consequently, controlling the NPD abundance and understanding their physical properties have become quite important, for not only do they critically affect the performance characteristics of the ensuing devices but often offer novel applications, hitherto unknown. ZnO nanostructures (ZoNS) possessing rather unique electrical and optical properties (band gap ~ 3.3 eV) is one such promising candidate for developing novel opto-electronic devices. Interestingly, the native electrical conductivity (n-type) of nominally un-doped ZoNS stems from the density and distribution of non-stoichiometric NPDs at its surfaces and interfaces[2, 3]. Broadly, their control has been successfully achieved by engineering the morphology of the ZoNS[4], primarily by tailoring the growth techniques and conditions[5]. And, understanding the correlation of morphology with optoelectronic transport has become central to optimizing the device properties. The presence of these NPDs become evident in the luminescence properties of ZoNS. The typical photoluminescence spectrum shows the characteristic near-band-edge emission in the UV, along with several prominent broad emissions in violet, green, orange and red, indicating the presence of shallow and deep level defect states[3]. Further, coupling of optical events to electrical response through NPDs at ZoNS surface has been an intriguing phenomenon with several important applications. Here, we report conductive atomic force microscopy (CAFM) studies of spatially resolved photoresponse properties on individual ZnO nanorods, with the aim of correlating surface morphology with defect distribution via the spatial variation in photoresponse. The CAFM measurements were conducted on vertically aligned hexagonal ZnO nanorods of height ~4?m and diameter ~400nm, prepared by an oxidation technique[3]. The rods predominantly display c-axis (002) oriented growth, though the morphology of the exposed hexagonal facets and x-ray diffraction spectra indicate the presence of differentially oriented crystallites. The simultaneously recorded topography and dark current maps, on the hexagonal top facets exhibit a broad grain size distribution, ranging from 30 ? 150 nm. Interestingly, the smaller grains carry much larger current than the bigger ones, indicating their higher conductivity. The side planes of a large fraction of nanorods do not appear single crystallographic in origin, but is suggestive of nanorod formation by a ?stack? of hexagonal (002) oriented crystallites. Such side planes appear more conducting than the top facets, with the current maps indicating a difference of an order in magnitude, or more. Interestingly, both the disorder of the side planes and the granularity of the top facets appear highly correlated with the local conductivity and photoresponse of the ZnO nanorods. The high current appear only at regions with the small grains i.e. regions with higher incidence of native point defects[6]. The spatially resolved photoresponse data were recorded for two wave-lengths, ultraviolet (355 nm) and green (532 nm). While the former corresponds to a super-bandgap energy h? > 3.3 eV, the latter at 2.33 eV was chosen to match the emission energies of the deep level defect states. The results not only provides direct evidence of correlation between surface morphology and photoresponse, but also discriminates between the photoactive regions in terms of the excitation energies. Firstly, the evidenced surface photoresponse is highly non-uniform for both excitations. Interestingly, for the 532nm excitation, photoresponse appears localized exclusively onto the smallest grains (diameter < 50 nm) ? the medium to larger grains showing no activity at all. The 355nm photoresponse though relatively more uniform again displays a strong preference for the smaller grains, with the larger grains occasionally becoming active. Differential conductance (dI/dV) maps (CMAP), at constant dc bias, were also recorded simultaneously with topography in the dark and both the above illuminations. The results show the variation of surface conductivity with a lateral resolution ~2nm and crucially its correlation with topography. The spatial variation in the defect centres on the top facet is accompanied by a non-uniformity in electrical conductivity on the surface of a single nanorod in the dark as well as under either illumination. Lastly, point current-voltage (IV) characteristics were recorded at regions of varying conductivity, with and without optical excitation. These electrical transport measurements across the Schottky nanocontact (between n-ZnO and cantilever tip), provided evidence of multiple transport processes at individual surface grains and grain boundaries. Depending on the local defect distribution and carrier density the transport varied between dominantly thermionic to tunnelling, between the high and low conducting regions, respectively. The forward biased IV data were analysed using the various transport models yielding a spatial variation of the barrier parameters, providing important information regarding the energetics of the defect states. In conclusion, the observed correlation between surface morphology (grain size) and the native conductivity and photoresponse in these ZnO nanorods is analysed based on the energetics of ZnO. Most nanostructures of the wide band gap ZnO is an intrinsic n-type semiconductor likely due to the interplay of two defect dopants, oxygen vacancies and interstitial Zn, both of which donate electrons to its conduction band[3]. Cumulatively, the current and conductance maps, recorded in the dark indicate that the smaller grains are more conducting, likely harboring a larger fraction of the above defects compared to the larger grains, resulting in their higher conductivity. The free electrons therein then may then facilitate adsorption of atmospheric oxygen[7] selectively onto the surface of the smaller grains. Upon UV exposure, especially in the reverse bias, the photogenerated holes migrate to the surface (junction) neutralizing the oxygen ions, which desorb leaving behind the free electrons. These freed electrons along with their photogenerated counterparts then contribute to the exponential increase in local conductivity. Such local carrier generation would also aid the junction current by simultaneously lowering the effective barrier height[4] and decreasing the depletion width, around the desorbed oxygen sites, namely the smaller grains. The highly disordered grain boundaries though impede effective conduction of the junction current, due to scattering, thus limiting the photoresponse to the centre of the smaller grains. The observed photoresponse with sub bandgap excitation is rather intriguing[8] and its origin is discussed with reference to the energetics of the oxygen vacancy states. Our investigations have drawn a direct relationship between the morphology, electrical conductivity and photoresponse in these ZoNS, along with a demonstration of the capability of using photo-conductive AFM as a tool to characterize spatially resolved photoresponse of semiconductor nanostructures. 1. Brillson, L.J., et al., Interplay of native point defects with ZnO Schottky barriers and doping. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2012. 30(5): p. 050801-050801-11. 2. Kim, Y.-S. and C.H. Park, Rich Variety of Defects in ZnO via an Attractive Interaction between O Vacancies and Zn Interstitials: Origin of n-Type Doping. Physical Review Letters, 2009. 102(8): p. 086403. 3. Bandopadhyay, K. and J. Mitra, Zn interstitials and O vacancies responsible for n-type ZnO: what do the emission spectra reveal? RSC Advances, 2015. 5(30): p. 23540-23547. 4. Gedamu, D., et al., Rapid Fabrication Technique for Interpenetrated ZnO Nanotetrapod Networks for Fast UV Sensors. Advanced Materials, 2014. 26(10): p. 1541-1550. 5. Alenezi, M.R., S.J. Henley, and S.R.P. Silva, On-chip Fabrication of High Performance Nanostructured ZnO UV Detectors. Sci. Rep., 2015. 5. 6. Vanheusden, K., et al., Mechanisms behind green photoluminescence in ZnO phosphor powders. Journal of Applied Physics, 1996. 79(10): p. 7983-7990. 7. Ahn, S.E., et al., Photoresponse of sol-gel-synthesized ZnO nanorods. Applied Physics Letters, 2004. 84(24): p. 5022-5024. 8. Vempati, S., et al., Unusual photoresponse of indium doped ZnO/organic thin film heterojunction. Applied Physics Letters, 2012. 100(16): p. 162104-4.

Resume : 9,10-diphenylanthracene (DPA) micro/nanostructures with uniform sizes and shapes have been synthesized via a surfactant-assisted self-assembly process. The shape of the micro/nanostructures can be controlled by a different kind of the surfactant solution, as well as varying the ratio of DPA solution to the preparation solution. Here, we have used Poly-(ethylene glycol)-block-poly(propyleneglycol)-block-poly-(ethylene glycol) (P123) and cetyltrimethylammonium bromide (CTAB) as the surfactant solutions. These micro/nanostructures have been characterized by UV-vis, fluorescence spectra, field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Our results indicated that as the ratio of DPA solution/P123 aqueous solution was increased, the shape of DPA structures changed from rods to wires [1]. When the ratio of DPA/P123 was 1:4.4, microstructures with the diameter of 2-2.5 ㎛ and the length between 7.5 and 8.5 ㎛ were obtained (Figure 1). However, for CTAB with same ratio, microstructures with the diameter of ~1 ㎛ and the length of 5-6 ㎛. And slightly change in optical properties were observed for micro/nanostructures of different morphology. When the length of micro/nanostrucutres was increased, a blue shift was observed.

Resume : During the last decades applications of Chemical Vapor Deposition (CVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) technologies show constant grow in various fields of scientific research, followed by technology and medicine [1-4]. In particular PECVD is an outstanding alternative for depositing a range of thin films at lower temperatures than those applied in CVD reactors; this often without settling for a lesser coating quality. The application of "cold plasma" PECVD equipment provides an excellent opportunity to coat thermally sensitive substrates, including porous and nanostructured plastics. In the same time plasma-assisted polymerisation renders possible an utilisation of "non-conventional" organic monomers for highly branched and cross-linked thermo reactive films having pronounced resistance towards solvents and strong adhesion to the substrate. The creation of composite materials or layers provides the researchers with an ability to combine the desirable properties of each of the materials, involved in the layered composite. In our case three types of input compounds were applied for varied PECVD deposition of nano-thick functional layers, namely hexamethyldisiloxane, pentane and toluene. The output plasma-polymerised coatings were characterised through SEM imaging, ATR-FTIR, EDX, AFM and contact angle measurements. [1] H. Pierson, Handbook of Chemical Vapor Deposition, Norwich, New York, ISBN 978-0-8155-1432-9, 1999 [2] M. Kumar, Y. Ando, Chemical Vapor Deposition of Carbon Nanotubes: A Review on Growth Mechanism and Mass Production, Journal of Nanoscience and Nanotechnology, 2010, 10 (6), 3739-3758 [3] J. Rath, M. Brinza, Y. Liu, A. Borreman, R. Schropp, Fabrication of thin film silicon solar cells on plastic substrate by very high frequency PECVD, Solar Energy Materials and Solar Cells, 2010, 94 (9), 1534-1541 [4] (Chapter) L. Pramatarova, E. Radeva, E. Pecheva, T. Hikov, N. Krasteva, R. Dimitrova, D. Mitev, P. Montgomery, R. Sammons, The advantages of polymer composites with detonation nanodiamond particles for medical applications, On Biomimetics, Rijeka, ISBN 978-953-307-271-5, 2011, 297-320

Resume : Recently the quantum dots (QDs) synthesis from single source precursors (SSPs) showed a potential interest for patterning formation of nano-composites [1]. In this approach the SSP has to be mixed with the matrix that afterwards is treated selectively to obtain the desired nanocomposite. The study of the generation of the QDs from the SSPs is, therefore, crucial for the definition of its behaviour within the polymeric matrix. The formation of the CdS nanoparticles via thermolysis of the cadmium carbammate was performed and studied in the presence of a coordinating solvent (trioctylphosphineoxide). In this work the use of this precursor is presented for the generation of the CdS QDs under the laser irradiation. The effect of the laser has been studied on a different polymer/precursor blends films with the aid of the fluorescence microscope. The results are used to identify the optimal laser parameters to obtain the decomposition of the precursor and to evaluate the effect of the laser irradiation on the polymer. References [1] A. K. Bansal, M. T. Sajjad, F. Antolini, L. Stroea, P. Gečys, G. Raciukaitis, P. André, A. Hirzer, V. Schmidt , L. Ortolani, S. Toffanin, S. Allard, U. Scherf & I. D.W. Samuel “In situ formation and photo patterning of emissive quantum dots in organic small molecules“ Nanoscale Vol 7, 11163-11172, 2015;

Resume : Photonic jets are propagating beams concentrated beyond the diffraction limit in the vicinity of dielectric micro-objects. They allow concentrating the incident power density more than 200 times in a spot with a full-width at half maximum smaller than a half wavelength. We show that this beam can be used directly to achieve sub-wavelength direct etching but also indirectly to excite localized surface plasmons of metallic nanoparticles and in this way to reach lambda/10 spatial resolution. The theoretical study is achieved considering a 2D finite-element method and 3D Lorenz-Mie theory. Two ways have been considered to generate the photonic jet: dielectric microspheres and optical fibers with shaped tip. The direct sub-wavelength photonic jet parameters are computed. The possibility to excite indirectly localized surface plasmons on metallic nanoparticles is demonstrated. First experiments show the possibility to achieve photonic jet under dielectric microsphere and under the shaped tip of optical fiber. Sub-wavelength etchings have been performed on silicon both with dielectric sphere and optical fiber. The possibility to etch material with higher threshold is also discussed.

Resume : Since its implementation as Hole Transport Material (HTM) in Solid-State Perovskite solar cells, the research on the molecule 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (abbreviated as Spiro-OMeTAD) has increased significantly.(1,2) This type of solid state hole conductor is crucial in the performance of perovskite solar cells and most of the research during the last years have focused in its deposition by wet methods.(3) In this work we have sublimed Spiro-OMeTAD molecules under vacuum onto silicon and silicon oxide substrates at mild temperatures. This molecule has the particularity that transform to the liquid phase at around 245 ºC and its deposition onto annealed substrates produce the formation of ordered nanodroplets of Spiro-OMeTAD molecules. The size and separation of these nanodroplets has been found to be dependent on the temperature of the substrates and the amount of material deposited. The samples present interesting optical properties such as diffraction patterns or iridescence due to the ordered arrangement of the nanodroplets. At the same time, these samples has been utilized as templates for the deposition of other oxides by PVD such as TiO2, enabling a fast and cheap route for the fabrication of nanopatterned samples. (1) Lee, M. M. et al. Science 2012, 338 (6107), 643–647. (2) Völker, S. F. et al. ChemSusChem 2015, 8 (18), 3012–3028. (3) Hsu, C.-Y. et al. Phys. Chem. Chem. Phys. 2012, 14 (41), 14099–14109.

Resume : The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Green and red up-conversion emissions of Er3+-Yb3+ co-doped TiO2 nanocrystals were reported. The phase structure, particle size and optical properties of Er3+-Yb3+ co-doped TiO2 nanocrystals samples were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis–NIR absorption spectra and photoluminescence (PL) spectra. Green and red up-conversion emissions in the range of 520–570 nm (2H11/2, 4S3/2-4I15/2) and 640–690 nm (4F9/2-4I15/2) were observed for the Er3+–Yb3+ co-doped TiO2 nanocrystals. The visible up-conversion mechanism and temperature dependence of up-conversion emission for Er3+ in TiO2 nanocrystals were discussed in detail. The absolute upconversion Quantum Yield (UC-QY) of each nanopowders was measured for the UC emissions centered at 525, 550 and 655 nm at varying excitation power densities. UC-QY analysis has revealed that 5 mol.% Er - 5 mol.% Yb : TiO2 nanopowders possess the highest total quantum yield of 2.8±0.1 % with a power density of 16.7 W/cm2. These results show that this nanopowder is promising as an efficient up-conversion oxide nanopowder suitable for potential photonic applications.

Resume : Colloidal semiconductor nanostructures, such as quantum dots (QDs) or nanoplatelets (NPs), and graphene offer exciting avenues for opto-electronics. Graphene, as an atomically thin semi-metal, may be viewed as an ultimate quasi-transparent electrode, while QDs and NPs exhibit excellent light emission and light harvesting properties. It is thus natural to combine these two model systems into novel hybrid devices. In such conditions, the photophysical properties of the nanoemitter are expected to be dramatically affected by the neighboring graphene layer. In particular, energy and/or charge transfer may occur and govern the performance of the hybrid device. Understanding of these phenomena requires fundamental investigations at the single particle level. Here, we make use of time correlated single photon counting to investigate the photophysics of individual CdSe/CdS QDs that are physisorbed onto a graphene monolayer. We observe highly efficient Förster energy transfer, resulting in a shortening of the luminescence decay and subsequent luminescence quenching. The energy transfer rate is further monitored as a function of the distance d between the QDs and the graphene layer. We obtain an energy transfer rate in quantitative agreement with a 1/d4 scaling, as expected for the Förster energy transfer rate between a “zero-dimensional” emitter and an atomically thin acceptor surface. Preliminary results using two-dimensional NPs show a different distance scaling.

Resume : Down shift converting high energy photons to low energy photons has been tried to enhance solar cell efficiency further. Phosphors or quantum dots like CdSe are usually used as materials for down shift. However, due to their low conversion efficiency, specially, in nano-sized down shift materials, there have been little enhancement of solar cell efficiency. Recently, quantum dots combined with nanostructures like photonic crystal structures have shown the enhancement of conversion efficiency and therefore solar cell efficiency. In this study, we used lanthanide-doped polymer-derived ceramics as luminescent down shift (LDS) materials. Photoluminescent intensity of LDS incorporated with nanopattern was enhanced 30 times higher than that of reference LDS without nanopatterns. As expected, the external quantum efficiency of Si photodetector which had LDS with nanopattern on its front side was also enhanced at the few-percent level in the UV and visible range. The enhancement in the UV range resulted from wavelength conversion by down shift of LDS with nanopattern, while the one in the visible range from anti-reflection effect. We expect that UV images can be obtained by low cost Si photodetectors by optimized combination of LDS with nanopattern and Si photodetectors.

Resume : Plasmonic metamaterials have gained great attention due to their unique optical properties and have already achieved a significant impact in a variety of photonic, data processing, and sensing applications. The resonant plasmonic behaviour may be tuned by varying the geometry of the nanorod arrays and the permittivity of the surrounding medium. Light can be coupled between two plasmon surfaces leading to nanoscale confinement that shows high sensitivity to the surrounding medium. This effect can be used for a variety of applications in the fields of bio- and chemical sensing, enhanced nonlinear optical effects, as well as for localised light sources for imaging. Here we describe the design and low cost fabrication technique of periodic arrays of multisegment Au-ZnO-Au nanorods using highly ordered porous alumina template. Perfectly ordered nanoporous alumina membranes, having large domain areas (square microns) has been obtained by employing two-step anodization. The pore geometry and spacing can be controlled over a wide range with nanoscale precision by a choice of anodization conditions and chemical post processing. The resonant wavelength can be tuned by changing thickness of ZnO between two Au segments during electrodeposition. These metamaterials open up new possibilities for a variety of applications in the field of nanophotonics and nano-opto-electronics.

Resume : Semiconductor nanowires (NWs) have attracted a considerable interest within the scientific community as innovative materials for applications in light sources, sensing and nano-scale photovoltaic devices. The optimization of NWs dimensions and the spatial arrangement in novel textured materials, both ordered and disordered, play a key role on the transport of the light towards striking optical performances based on light trapping, multiple scattering and localization of light. Here we present the impressive optical properties of a forest of ultrathin vertically aligned silicon nanowires arranged in a 2D fractal array realised without the use of mask or lithography process. This kind of structure allows for a particularly high efficiency of light trapping in all the visible range, approaching diffuse reflectance values as low as the 0.1% when the incident wavelength matches the maximum heterogeneity size exhibited by the Si NWs arrangement [1]. Furthermore the occurrence of strong in plane multiple light scattering are responsible for a giant photoluminescence and an enhanced Raman scattering, paving the way towards a new class of light emitting devices. [1] “Strongly Enhanced Light Trapping in a Two-dimensional Silicon Nanowire Random Fractal Array” B. Fazio, P Artoni, M A Iatì, C D’Andrea, M J Lo Faro , S Del Sorbo, S Pirotta, P G Gucciardi, P Musumeci, C Vasi, R Saija, M Galli, F Priolo, and A Irrera. In press to Light: Science & Applications

Resume : The optical properties of carbon nanotubes (CNTs) are serving as a powerful nano-photonic platform with potential for innovative devices such as ultra-short pulse lasers, light emitters, photonic sensors. The photonic applications together with traditional reinforcement and conductive composites products require mass production of CNTs in thousands of tons making CNTs a potential environmental pollutant. The nanotubes might get into the environment during fabrication process, exploitation, and disposal. Therefore, an efficient method for their rapid, efficient and selective detection must be established. Here, we demonstrate novel ionic complexes of carbon nanotubes – polymethine dyes with the enhanced nanotubes emission in the range of dye excitation. This is a sensitive and selective response to carbon nanotubes with a photoluminescent signal. The complexes are formed due to Coulomb force attraction of the charged polymethine dye to carbon nanotube covered by ionic surfactant in water, so excitation of the dyes can be transferred to the tubes. As a result of photoluminescent excitation of the dye that is transferred to the nanotubes, a selective and strong amplification (up to a factor of 6) of the light emission from the excitonic levels of carbon nanotubes in the near-infrared spectral range is observed experimentally via excitation-emission photoluminescence mapping. The type of ionic surfactant used to disperse the nanotubes as well as the chirality of the nanotubes strongly affect the amplification. This way the complexation provides selective detection mechanism for specific carbon nanotubes. Besides, uncharged dyes and carbon nanotubes covered with neutral surfactant do not form such complexes. The easy tailorable molecules of polymethine dyes, in particular cyanines [1] and dioxaborines [2] were used as model organic molecules for the complexation. The ability to tune π-conjugated system of polymethine dyes allows us to alter the energy levels in the studied complexes in controllable manner. Thus, functionalization of the nanotubes towards breaking the limitation of low photoluminescence quantum yield is a key issue for engineering of novel photonic applications. In this work, we provide efficient light-harvesting-and-emitting system with great potential to boost future various photonic applications including an efficient sensing of carbon nanotubes in water. Acknowledgements: The work was supported by NATO SPS project (NUKR.SFPP 984189) and EU FP ‘Horizon-2020’ Marie Skłodowska-Curie Individual Fellowship (FOC4SIP, 654733). References: [1] P. Lutsyk, R. Arif, J. Hruby, A. Bukivskyi, O. Vinijchuk, M. Shandura, V. Yakubovskyi, Yu. Kovtun, G.A. Rance, M. Fay, Y. Piryatinski, O. Kachkovsky, A. Verbitsky, A. Rozhin. Light: Science& Applications (2016) 5, e16028. [2] M.P. Shandura, Yu.P. Kovtun, V.P. Yakubovskyi, Yu.P. Piryatinski, P.M. Lutsyk, R.J. Perminov, R.N. Arif, A.B. Verbitsky, A. Rozhin, Sensor Letters (2014) 12, 1361-1367.

Resume : Colloidal quantum dot (CQD) films and optical metamaterials are two well-known classes of artificial matter. While they are used in different contexts, both types of composite media have much richer properties than naturally occurring substances because their behavior is not solely defined by their chemical composition, but also largely by their inner geometry. Here we show that combining CQD films and optical metamaterials dramatically increases the possibilities of artificial media for optoelectronic applications. We demonstrate these ideas by introducing the concept of structural electroluminescence (arising from geometrical effects in discrete blocks of subwavelength dimensions) and discuss the potential of our findings for LEDs, displays, light-harvesting devices and sensors.

Resume : Plasmonic nanostructures have recently been shown to alter the energy density of states increasing and then to provide a tunable trigger to control the photophysical response of semiconductor materials.1-6 Experimentally and theoretically,7 we investigated the effects of a range of plasmonic nanostuctures on the photoluminescence (PL) lifetime of several organic chromophores which emission ranges from UV to visible. These molecules were immersed in a polymeric matrix spincoated on top of the plasmonic nanostructures and streak camera measurements were completed to monitor spontaneous emission. The PL lifetime was shown to be altered by the underlying plasmonic nanostructures in a non-monotonous way. To analyze systematically, this behavior and fully understand the involved mechanisms, we also developed a theoretical analysis and took advantage of both invariant imbedding and FDTD methods as computational tools to quantitatively explain the experimental results and predict the responses, which could be observed when varying further the plasmonic nanostructures.

Resume : Following Fermat’s principle, optical components shape incident light beams by introducing a difference in optical path length of two adjacent light rays. This can be realized by a local change of the device thickness or refractive index, with respect to the light path. In contrast, metasurfaces can introduce an additional phase shift by using the response behavior of nanoantennas, excited near their resonance frequency [1]. To produce these antennas, very flexible and precise direct writing lithography technologies are the method of choice, although these techniques have disadvantages in terms of cost-efficiency on large scales. Nanosphere lithography (NSL) instead is a powerful low-cost method to pattern large-area planar substrate surfaces with 2D arrays of nanostructures to form optical metasurfaces [2-4]. Never the less, to build functional devices, coordinated regions are needed, patterned with different types of metasurfaces, each formed by an array of specially designed nanoantennas. Therefore we expand the NSL technique and show how optical devices, like metasurfaces-based flat vortex lenses for the creation of donut-shaped foci, can be fabricated. [1]: N. Yu et al., Science, 334, 6054, 333 (2011) [2]: C. L. Haynes, R. P. Van Duyne, J. Phys. Chem. B, 105, 5599 (2001) [3]: A. Kosiorek et al., small, 1, 4, 439 (2005) [4]: A. Nemiroski et al., ACS Nano, 8, 11, 11061 (2014)

Resume : Small diameter semiconducting single-walled carbon nanotubes (s-SWNT) show photo- (PL) and electroluminescence (EL) in the near-infrared with very narrow line widths and emission wavelengths precisely defined by the SWNT chirality. Combination of various chiralities and thus bandgaps in dense networks results in a shift of intensity toward nanotubes with smaller bandgaps by fast exciton transfer. Incorporating networks of purely semiconducting SWNTs into field-effect transistors enables the observation of EL due to balanced electron and hole mobilities. The obtained EL spectra show an even more pronounced shift toward emission from smaller bandgap s-SWNTs compared to the corresponding PL spectra. They can be used as a quantitative measure for charge distribution within an energetically disordered network. Here, we demonstrate this approach with a variety of networks of s-SWNTs sorted and enriched by polyfluorene wrapping. This leads to gate voltage-dependent EL spectra with a large shift toward emission from small bandgap nanotubes that reflects the distribution of charges within the network and reveals the large impact of small fractions of small bandgap SWNTs on device performance. With increasing charge carrier density the EL spectra approach the PL spectra as more and more s-SWNTs participate in the transport. Furthermore, spatial images of EL versus PL of the transistor channel show current percolation paths within SWNT networks.

Resume : The study of metal nanoparticles (NP) is challenging for the control of the light matter interaction phenomena. In this context, our work is focused on the optical properties of synthesised silver nanostructures enclosed in a polymer host matrix. The NP in polymer thin films are assumed to result in layers with tunable optical properties. Thin film layers with inclusions of differently shaped and sized NP, such as spherical NP (SNP) and prismatic NP (PNP), are optically characterised to get the scattering, reflection and absorption. One step (SNP) and two step seed based (PNP) methods of silver ions reduction by ascorbic acid are used for the chemical synthesis of NP. The plasmonic resonance peaks of these colloidal solutions range from 360 nm to 1300 nm. At first, a PVP polymer matrix is chosen for its non-absorbing and NP-stabilising properties. AFM, SEM and TEM morphological studies of the spin coated layers are performed to have details on the shape, size, concentration and dispersion of the embedded NP. The optical studies of the layers include spectrophotometry and ellipsometry, for reflection, transmission, absorption and optical indices n and k. A 25 nm redshift in absorption is measured between same volume deposited SNP and PNP. FDTD simulations allow calculation of far and near field properties. The visualisation of the NP interactions or the electric field enhancement on and around the NP can be studied to improve the understanding of the far field properties.

Resume : Plasmonic metallic nanoparticles (NP) have gained significant attention due to their exceptional functionality, extreme chemical sensitivity and the strong optical phenomena they manifest at the nanoscale. The excitation of plasmon oscillations on metal NP gives rise to both absorption and scattering. The scattering process can be orientated towards specific angles (primarily specular) but depending on the nanostructure can be diffuse as well. The identification and quantification of specular and diffuse scattering is of great importance in order to design nanoparticle structures that favour a specific scattering regime. To date, there is very limited literature relating to this full optical characterisation and the angular properties of NP arrays. Here we present a novel investigation into the diffuse and specular reflection of light from laser fabricated plasmonic NP across a range of silica thicknesses on a silicon substrate. These nanoparticles present a single resonance at normal incidence but with a strong variation to their colouration over a wide range of angles when viewed with the naked eye. For the full characterisation of these samples we have considered the reflectance of various NP templates at a series of specular positions, from normal incidence (0 degrees) to a grazing incidence (70 degrees) with a custom built goniometric system. We have separated the S-, P-, and N-polarization reflectance to establish the nature of this resonance shift.

Resume : Scanning a plasmonic particle with a sharp dielectric tip and simultaneously monitoring the plasmon spectra allows us to measure the full spectral changes of a plasmonic resonance induced by a local dielectric pertubation. The spectra are fitted by Lorentzian functions to extract different spectral parameters without cross correlations. The obtained data are aranged according to the relative position of dielectric tip and plasmonic nanoparticle to obtain a surprising diversity of spectral patterns. We find that the obtained resonance shift, i.e., the local refractive index sensitivity, is closely related to the near field intensity, in accordance with theoretical predictions. A position dependent increase and decrease of the total scattering section of the combined system is observed, which can be explained within a simple model, taking into account the vectorial nature of the near fields. Finally, a change in plasmon linewidth is related to a change in radiation damping from the tip. Apart from fundamental interest, our results are significant for the interpretation of optical near field measurements. The possibility to perform local refractive index sensitivity measurements is useful for the development of future plasmonic bio-sensors.

Resume : Modern products are becoming more miniaturised, more complex and have an increasing number of functionalities. As a consequence, the critical dimensions of structures written in silicon are becoming considerably smaller than the wavelength of the applied light source and this trend is to be sustained for the coming years until the next-generation patterning using extreme UV is implemented. As the feature sizes are decreasing, so the theoretical and practical constraints of making them and ensuring their quality are increasing. The same holds true for other industrial branches such as machine construction and automotive engineering where the surface-quality requirements of critical components and the overall complexity of the products have dramatically grown over the past few years. Consequently, modern production and inspection technologies are confronted with a bundle of challenges. In this paper at first the mentioned challenges and the physical limitations are addressed. Afterwards a systematisation of existing approaches for resolution enhancement is presented and some modern approaches such as active wave front control, model based feature reconstruction, intelligent sensor fusion, and super lens design using metamaterials are discussed. On example of the inspection of non-resolved semiconductor structures new practical ways to cope with challenges such as CD metrology in the presence of line edge roughness, precise overlay control for multiple patterning, and detection of grating asymmetries for mask alignment are presented.

Resume : Coherent control over the propagation of light well beyond the diffraction limit has been so far realized using metallic nanostructures which sustain surface plasmons [1]. Besides the ability to control the light propagation at nanoscales, localization of light in volumes which can be theoretically as small as a few atoms via localized surface plasmon resonances has found a large variety of applications in harmonic generation and optical circuitry. A critical point of field localization at nanoscales is, however, the coupling efficiency of the optical far-field radiation into the volume fraction of interest. It has been proposed that tapered metallic waveguides can offer a highly efficient control over the delivery of energy at their apex through an adiabatic reduction of the plasmon velocity, which asymptotically leads to field localization and stopping. As a model system we use single-crystalline gold tapers, whose particularly smooth surfaces eliminate surface plasmon localization and scattering losses along the taper shaft. We experimentally investigate the energy bands of these tapers as plasmonic light trappers by electron energy-loss spectroscopy (EELS) and energy-filtering transmission electron microscopy (EFTEM). The experiments were conducted at the Zeiss SESAM microscope operated at an accelerating voltage of 200 kV. The microscope is equipped with an electron monochromator and the MANDOLINE energy filter. The striking evidence is that plasmons are excited both at the apex and along the taper shaft. By moving the electron beam along the taper shaft, we probe the evolution of the optical modes versus the distance from the apex. At the very apex, we resolve an extremely broadband spectral feature covering the whole energy range from 0.5 eV to 2.0 eV. By moving the electron beam away from the apex, further resonances are excited by the electron beam. Using the finite-difference time-domain technique with an embedded electron probe [2], the experimental EELS patterns are perfectly reproduced in our simulations, including both the broadband spectrum at the apex and the occurrence of higher-order resonances. In summary, our results show higher-order angular momentum modes with unexpected resonance dispersions. These findings suggest that the three dimensional gold tapers can be used for an efficient coupling of the far-field to the near-field which makes them particularly interesting for future quantum-optical applications [3]. References [1] B. Ogut et al., Nano Lett 12 (2012) 5239 [2] N. Talebi et al., New J. Phys. 15 (2013) 053013 [3] N. Talebi et al., ACS Nano 9 (2015) 7641 Acknowledgements NT gratefully acknowledges Alexander von Humboldt Foundation for the research scholarship. Financial support by the European Union project CRONOS (Grant number 280879-2), the Deutsche Forschungsgemeinschaft (SPP1391, DFGLi580/8-1, INST184/107-1) and the Korea Foundation for International Cooperation of Science and Technology (Global Research Laboratory project, K20815000003) is gratefully acknowledged. The research leading to these results has received funding from the European Union Seventh Framework Program [FP/2007/2013] under grant agreement no 312483 (ESTEEM2).

Resume : Semiconductor nanoplatelets (NPLs) is a new class of nanostructures which holds a great promise to become the most efficient colloidal luminophores. The radiative lifetime of NPLs is shorter and photoluminescence (PL) linewidth is narrower than that in other colloidal nanostructures, due to a quasi-two-dimensional spectra of carriers in ideally flat structures and specifics of two-dimensional dielectric confinement. Although NPLs emission is obviously connected with two-dimensional excitons, the mechanisms responsible for their radiative decay and the PL linewidth have not been understood yet. We study magneto-optical properties of CdSe NPLs with 4 and 5 monolayer thickness using combined time- and spectrally-resolved spectroscopy in high magnetic fields (up to 15 T) at cryogenic temperatures (down to 2.2 K). We find a strikingly high circular polarization degree, up to 60% at a magnetic field of 3T. By contrast with quantum dots, the circular polarization degree displays a non-monotonous magnetic field dependence. After reaching a maximum of 60% at 3T, it drops to less than 30% at 15T. Concomitantly, the exciton spin dynamics changes from mono-to two-exponential decay. These results show that, contrary to quantum dots, magnetic-field-induced bright-dark exciton mixing is not sufficient to describe the magneto-optical properties of NPLs. The unusual magnetic field behavior could be connected with a contribution of the surface dangling bonds.

Resume : Metal nanoparticles (NPs) upon interaction with light exhibit localized surface plasmon resonances (LSPRs) that can be strongly manipulated by bringing them into close proximity. Plasmonically-coupled assemblies display highly localized and maximized plasmonic effects resulting from “hot spot” formation.[1] Gold nanorods (Au NRs) are attractive plasmonic building-blocks due to the strong electric field enhancement localized at their tips upon excitation of their longitudinal LSPR, while DNA is known as a powerful biomolecule that can be used to self-organize colloidal NPs with a high specificity.[2] However, the formation of controlled tip-bound NP assemblies with Au NR-DNA conjugates as building-blocks remains challenging due to the identical assembly potential of the conjugates’ tips and sides. In this work, we report a synthetic approach developed in order to impinge Au NR-DNA conjugates with directional interactions at their tips. We thereafter show that by controlling the experimental conditions it is possible to evolve from non-directional into fully-directional Au NR-DNA conjugates with the ability to undergo tip-selective self-assembly with other Au NPs functionalized with complementary DNA strands. The assemblies display strong directional plasmonic properties upon interaction with light. Among other effects, we demonstrate that these assemblies can be employed as SERS (surface enhanced Raman scattering) ultrasensitive label-free DNA sensors, where only a few strands are needed to provide excellent read-outs. References: [1]. Ko, H. et. al., Small, 2008, 4(10), 1576–1599. [2]. Tan, S. J. et. al., Nature Nanotech., 2011, 6, 268-276.

Resume : Transition metal dichalcogenide materials (TMDs) are increasingly gaining attention, due to their unique optical, spintronic, and electronic properties [1]. These properties result from the ultimate confinement in 2D monolayers of the excitons, a direct band-gap semiconductor and the lack of inversion symmetry in the crystallographic structure [2]. To control and enhance the optical response of these materials, it is interesting to integrate them with plasmonic nano-resonators, known by their ability to strongly boost the light absorption and emission of nano-objects located in the vicinity of their surface [3-4]. In this context, we investigated the interaction between the surface plasmons of gold nanodisks and the 2D excitons confined in MoSe2 monolayers. The MoSe2 layers were grown by Chemical Vapor Deposition (CVD) and then transferred to the gold nanodisks array. The latter were synthesized by nano-sphere lithography and designed in such a way that their surface plasmon resonance falls in the spectral range of the excitonic transition of MoSe2 . Optical measurements revealed the presence of transparency dips, typical of Fano spectral lineshapes, thus proving the interference between the plasmonic and excitonic resonances. Fano-type coupling regime was evidenced by a quantitative analysis of the optical extinction spectra based on an analytical model of two coupled oscillators [5] . This analysis was complemented by numerical simulations of the optical spectra and of the electric near-field distribution. We found that the surface plasmon-exciton interaction is mainly localized in the gap region between the nanodisks. Moreover, by changing the temperature of the sample, we were able to fine tune the excitonic transition to the plasmonic resonance, which allows to investigate the Fano-lineshape dependence on excitonic energy and broadening. In addition, using a fitting of the experimental data by the analytical model[6], we were able to extract the temperature dependence of the plasmonic-excitonic coupling strength. Our results contribute to the understanding of the near-field interaction between strongly localized surface plasmons and excitons and paves the way to the development of new applications in the field of hybrid plasmonics. [1] Z.Weijie, R. Mendes Ribeiro, G. Eda, Electronic Structure and Optical Signatures of Semiconducting Transition Metal Dichalcogenide Nanosheets, Accounts of Chemical Research 48, 91 ( 2015) [2] W. Q. Hua, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, M.S. Strano, Electronics and optoelectronics of two-dimensional transition metal dichalcogenides, Nature Nanotechnology7, 699 (2012) [3]E. Petryayeva and U. J. Krull, Localized surface plasmon resonance: Nanostructures, bioassays and biosensing Anal. Chim. Acta 706, 8 (2011) [4] S. Najmaei, A.Mlayah, A. Arbouet, C. Girard, J. Léotin, J.Lou, Plasmonic Pumping of Excitonic Photoluminescence in Hybrid MoS 2 –Au Nanostructures , ACS Nano, 8, 12, 12682 (2014) [5] I. Abid, A. Bohloul, S. Najmaei, C. Avendano, H.-L. Liu, R. Péchou,A. Mlayah and J. Lou, Resonant surface plasmons-excitons interaction in hybrid MoSe 2 @Au nanostructures : submitted to nanoscale [6] X. Wu, S. K. Gray, and M. Pelton, Quantum-dot-induced transparency in a nanoscale plasmonic resonator, Opt. Express, 18, 23, 23633 (2010)

Resume : Hybrid materials have been intensively developed for optical applications (sensors, filters, imaging, photocatalysis…). Interactions between optical components and plasmonic systems can be used to tune and optimize the optical responses (emission, absorption) using the local electromagnetic field. Our strategy was to prepare transparent glass materials incorporating both optically active systems (dyes, semiconductors) together with plasmonic nanostructures with controlled shape and size. In order to achieve such complex material, we have first developed the synthesis of various gold nanostructures and in particular bipyramids with high yield and purity, exhibiting plasmon resonance from the visible to the NIR wavelengths.[1] These nanostructures were functionalized though a specifically designed silicon in order to allow their homogeneous incorporation in transparent hybrid silica glasses using the sol-gel process.[2] Co-dispersion of the metallic structures with dyes or semiconducting nanoparticles (TiO2) was successfully achieved. The role of the concentration, shape and size of the metal nanoparticles on the optical response was evaluated. Unexpectedly, strong enhancement was observed at low concentrations and the mechanisms will be discussed. The results will be illustrated though applications such as optical protection or photocatalysis.

Resume : This presentation will overview methods for the improvement of physical sensitivity of plasmonic biosensors, which rely on the detection of biological binding events on gold surface through refractive index monitoring. Our original approach addresses to the employment of phase properties of light instead of amplitude ones in order to improve the performance of plasmonic biosensing technology [1,2]. As it was confirmed in numerous studies and commercial implementations, such approach makes possible at least 2 orders of gain of sensor sensitivity in classical thin film geometry of plasmon excitation [3]. The concept of phase-sensitive plasmonic biosensing is now extended to a variety of new nanoscale architectures, including ones involving metamaterials, which are better adapted for modern requirements of bio-nanotechnology and offer new functionalities. The presentation will describe several novel promising nanoscale designs and architectures, including: (i) periodically arrayed gold nanodots, which support diffractive-coupled plasmon modes yielding to a drastic improvement of plasmon resonance quality and, as a consequence, to the amplification of sensing response [4]; (ii) gold nanorod metamaterials, which are capable of supporting new guided modes, which are more sensitive to refractive index changes compared to localized plasmon counterparts [5]; gold-graphene metasurface architectures, which can profit from the combination of a high phase sensitivity and new graphene-based functionalization strategies based on many aromatic structure biomolecules (helical peptides, proteins, ssDNA, etc.) [6]. Depending on a concrete biosensing task, the metamaterials can be designed either to record several binding events (a way toward ultimate label-free single molecular detection) or to enable large surface coverage in order to improve integral sensitivity. Combined with tuneable spectral response and strong local field enhancement, the designed biosensors outperform conventional plasmonics-based counterparts and open up new opportunities for the advancement of current state-of-the-art biosensing technology. [1] Kabashin, A. V., Nikitin, P. I., Opt. Commun., 1998, 150, 5-8 (1998) [2] Kabashin, A. V., Patskovsky, S., Grigorenko, A. N. Opt. Express, 17, 21191-21204 (2009) [3] Huang, Y. H., Ho, H. P., Kong, S. K., Kabashin, A. V. Annal. der Physik 524, 637 (2012) [4] Kravets, V. G., Schedin, F., Jalil, R., Britnell, L., Gorbachev, R. V., Ansell, D., Thackray, B., Novoselov, K. S., Geim, A. K., Kabashin, A. V., Grigorenko, A. N. Nature Mater., 12, 304-309 (2013) [5] Kabashin, A. V., Evans, P., Patskovsky, S., Wurtz, G., Hendren, W., Dickson, W., Pollard, R. J., Podolsky, V., Zayats A. V., Nature Mater., 8, 867-871 (2009). [6] Zeng, S., Sreekanth, K. V., Shang, J., Yu T., Chen, C.-K., Yin, F., Baillargeat, D., Coquet, P., Ho, H.-P., Kabashin, A. V., Yong, K.-T., Adv. Mater., 27, 6163?6169 (2015).

Resume : In this work we compare the photoluminescence of nanorods collected by two different means: fiber based optical tweezers and traditional objective based confocal microscopy. Our nanocrystals (NaYF4) are doped during a hydrothermal synthesis by rare earth elements (Ytterbium and Erbium). Under IR laser excitation, the nanoparticles present strong, photostable upconversion signals in the visible range. In addition, by changing the gadolinium content of the host matrix, we obtain nanorods with a well defined crystalline structure and a controlled aspect ratio up to 20. The high aspect ratio of the nanorods results in a strong polarisation of the photoluminescence. To investigate these properties, we observe and characterize first our nanoparticles in a confocal microscope. To complete our characterization, we use optical tweezers to trap nanoparticles in water. We first show the possibility to trap these nanoparticles with an original optical tweezers based on two chemically etched fibers. Afterwards, the fibers are not only use to trap the particles but also to collect the luminescence emitted only by the trapped nanoparticles. Moreover, an orthogonal third fiber was implement in the set up. This fiber can move along the particle and collect the light emitted at different point. By this means we can analyse the emitted light with a spatial resolution. This result will be compare to previous observation done on the same particles with our confocal microscope.

Resume : Hydroxyapatite (HA) is the mineral component of bones and teeth and is one of the most common natural biomaterials widely used in medical applications. There are two main ways of using white-light interference microscopy to measure HA according to whether observations are performed on the surface or inside the layer. First, coherence scanning interferometry provides rapid, contactless measurements of surface roughness using the single fringe envelope associated with the surface. Second, full-field optical coherence tomography is another associated technique that can be used to measure the thickness and internal structures of transparent layers by detection of multiple fringe envelope signals. However, the semi transparency of HA, its high surface roughness and complex spongy aspect makes its structural characterization a challenge for any technique. Basic post processing methods, such as image averaging, and dark and flat corrections, can be used to improve the quality of the fringe images by increasing the signal to noise ratio. Likewise, the image contrast can be enhanced by combining images with different exposures. In this paper we propose a hybrid high dynamic range (HDR) technique combined with other image processing methods applied to HA to enable normally unmeasured features to be observed. The result is an improvement in the lateral resolution of the system and the increase of its power of detection, enabling new sub-diffraction sized structures to be detected.

Resume : The unrivalled Young?s modulus, low density and high thermal conductivity of diamond make it attractive for high frequency, low dimensional electro-mechanical systems. Thin diamond films can now be produced on substrates such as silicon with Young?s modulus as high as 1100 GPa and high thermal conductivity. However, diamond growth on foreign substrates is still ultimately polycrystalline with surface roughness proportional to thickness. In this work the steps necessary to produce high quality diamond films for Micro-Electro-Mechanical Systems explained. Nucleation of diamond on foreign substrates, control over the CVD growth process, Chemical Mechanical Polishing and device fabrication will be demonstrated. Integration with materials such as AlN and GaN will be discussed. Superconducting and non-superconducting MEMS / SAW devices will be demonstrated with frequency-Q products as high as 1014 Hz. The potential of diamond as material for Quantum metrology will be discussed.

Resume : We report on a novel concept for on-chip engineering of dynamically reconfigurable structures for many advanced optoelectronics device applications, using novel class of hybrid fluid nanocomposite materials- graphene liquid crystal (GLC). Such hybrid materials were synthesized by doping nematic liquid crystalline host fluid with graphene/graphene oxide nano-particles, which are then aligned by the liquid crystal?s self-assembling capability into pre-designed configurations. For the first time, the use of micro-fluidic technology for the infiltration of synthesized GLC nano-composites into Si photonic chip is successfully demonstrated, as a back-end integration process, and for low-power controllable manipulation directly on chip utilizing fundamental tuning approaches in Si photonics: electro-optic and thermo-optic effects. The properties of the fabricated GLC nano-composites have been accessed directly on chip using in-situ characterization techniques such as SEM, TEM, electrical testing, micro-FTIR and micro-Raman spectroscopies. It was demonstrated that for silicon-on-insulator (SOI) based microfluidic channels (< 5?m width) the self-aligned graphene oxide colloidal particles can be optically trapped during characterization with micro-Raman spectroscopy. Finally, we will present and discuss the first practicable GLC based device designs for application in integrated photonics.

Resume : Infrared detection of short wave infrared (SWIR) and mid wave IR (MWIR) is important for numerous potential applications in the civil, medical, defense and security areas. State of the art, photon detection technologies for the extended SWIR (beyond 1.7µm) and MWIR are based on low operating temperatures. Due to the temperature requirement, the detection systems (mainly, focal plane arrays – FPAs) are complicate, heavy and expensive. Therefore room temperature easy produced mid-IR (3-5 μm) and short-IR (1.7-2.5 μm) wavelength detectors are still needed to be developed. We are developing a sensitive and a simple detector which responds to the SWIR and MWIR spectral regimes. To achieve this goal I will present preliminary results to utilize doped self-assembled colloidal semiconductor nanocrystals that exhibit IR inter- and intra-band absorption, on top of FET transistor.