Materials- nanoelectronics & -nanophotonics

Resume : Hybrid photonic-plasmonic systems are promising devices in fields such as biosensing and optoelectronics, due to their specific modulation of light behaviour. In this work, multilayer porous silicon (PSi) interference structures have been used as support for arrays of Au nanocavities to combine the photonic properties of the former with the plasmonic properties of the latter, to develop an hybrid photonic-plasmonic device. PSi multilayer stacks were produced by carefully tuning the electrochemical etch of p-type monocrystalline silicon wafers to produce contrasting porosity strata and thus achieve a predetermined interference response [1]. On top of this structure, a large area colloidal monolayer was deposited and shaped by reactive ion etching, A 200 nm thick Au layer was deposited followed by a final step of lift off of the remaining colloidal structure, producing a plasmonic Au nanocavity array [2]. Different post-processing treatments of annealing and chemical etching were applied to tailor the Au microstructure. These hybrid structures have been characterized by scanning electron microscopy, which has allowed to infer the main characteristics of the system, such as thickness of individual PSi layers in the interference stack, and the evolution of the grain size of the Au out-structure. In addition, cummulative reflectance measurements at each fabrication step allowed evaluating the individualized optical contribution of each structure and their coupling. Results suggest that these type of hybrid structures may allow the development of dual photonic-plasmonic biosensors with enhanced sensitivity. [1] C. Pacholski. Photonic Crystal Sensors Based on Porous Silicon. Sensors 2013, 13, 4694-4713. [2] B. Bottazzi, et al. Multiplexed label-free optical biosensor for medical diagnostics. Journal of Biomedical Optics 2014, 19 (1), 017006.

Resume : Plasmonics provides excellent templates for engineering emission from organic molecules, fluorescent dyes and quantum dots, as it is characterised by strong enhancement and confinement of light and large modification of the local density of states. Modern nanotechnology offers unprecedented flexibility in designing narrow plasmonic cavities, and precisely positioning emitters in them, with few- or even sub-nm accuracy. Such experimental advances go hand in hand with novel theoretical approaches which highlight the necessity to depart from classical electrodynamics. Nonclassical effects such as electron spill-out, quantum tunnelling, nonlocal screening, and surface-enhanced Landau damping become highly relevant in these situations. Here we implement the Generalised Nonlocal Optical Response theory to explore how the latter two, larger-scale effects, affect the coupling of emitters with canonical plasmonic nanostructures. For single fluorescent molecules coupled to the plasmon modes of Ag nanoshells, the nonlocal description shows that fluorescence enhancement reduces by up to two orders of magnitude. On the other hand, nonlocality becomes less important when examining the Rabi splitting induced by the interaction of the excitonic and plasmonic states in J-aggregates/Ag nanoparticle systems. Our discussion provides useful insight into experimentally relevant nonclassical processes, and should therefore facilitate the analysis of emitter-plasmon hybrids in practice.

Resume : Implementing nanostructures on flexible plastic film is indispensable for highly efficient optoelectronic devices. Recently, several attempts to realize nanostructures on flexible polymer substrates have been developed through nanoimprint and Langmuir-Blodgett method. However, there are distinct limitations like as low throughput, deformation, complex process and long synthesis time, in application to highly efficient flexible optoelectronic devices. Here, we will propose a new and simple growth of nanorod on polymer film by plasma-assisted strain relaxation to overcome the existing problems. By employing the Cl2 plasma treatment onto the Ag film on polymer substrate, large lattice mismatch between Ag and AgCl caused the substrate to flex. This flexion provided effective strain relaxation and access of Cl radicals to the surface of the growing AgCl nanorods (NRs). From the crystallographic analysis by transmission electron microscopy and X-ray diffraction, we elucidated the single crystal AgCl NR with (200)-preferred direction and proved that quasi-epitaxial growth is made by matching domains. The nanorods grown for 45 s exhibit superior haze up to 100 % and luminance of optical device increased by up to 33%. The advantages of this technique are low temperature process and high growth rate (about 2,000 nm min-1). Such process condition allows the AgCl NRs to implement the R2R process.

Resume : In this work we have reported on hybrid metallic nanostructures that surface plasmon resonance is modulated by combination of silver nanoparticles with copper or nickel nanovoids. Such hybrid materials were fabricated by electroplating and following silver immersion deposition on macroporous silicon. Porous material played a role of template for the formation of nanovoids. Presented data implies that morphology and ratio of the silver/copper, silver/nickel nanostructures on macroporous silicon allow to manage the position of their surface plasmon resonance band from near UV to IR ranges. It is shown that such nanostructures demonstrate efficiency in surface enhanced Raman scattering both under blue and red excitation wavelengths and allow detection of test organic molecules which concentration varies from micro- to nanomol.

Resume : In recent times the design and development of bio sensors with functional coatings have increasingly become popular. One such type of coating is Hydroxyapatite. In most cases the Hydroxyapatite-based coatings are fabricated with deposition of thin films via magnetron sputtering, electrophoretic deposition and spin coating techniques with subsequent high temperature sintering. The high temperature treatment greatly limits the choice of materials that can be used in the sensor fabrication and also will not be economically viable. Recently there were studies that have utilized Hydroxyapatite thin films deposited under ambient conditions for sensing adsorption desorption behaviours of proteins. In this research the fabrication of Nano-Hydroxyapatite films on quartz crystal microbalance sensors using electrophoretic deposition and spin coating technique are reported. Synthesized Nano-Hydroxyapatite particles were characterized by X-ray powder diffraction and scanning electron microscope. The study looks at the stability of the Nano-Hydroxyapatite films immediately after deposition, after sonication and after prolong water exposure. The stability is measured by monitoring the changes in the quartz crystal microbalance resonance frequency, which is proportional to the mass accumulation or removal, at each of the above steps. Separate scanning electron microscope measurements were carried out to confirm the observations. The results from the above experiments show that the initial thicknesses of the Nano-Hydroxyapatite films formed are concentration dependent with thicker coating obtained with the electrophoretic deposition method compared to that obtained with spin coating. However, these thicker coatings are unstable and can easily be reduced to thin quasi stable Nano-Hydroxyapatite films on the gold surfaces. While the resulting thin films show significant stability under ultrasonic treatment in aqueous medium, the subsequent prolong exposure to similar mediums show the complete removal of the Nano-Hydroxyapatite film from the substrate. This instability can be related to the preferential crystal orientation of the Nano-Hydroxyapatite particles on the gold surface. Comparative studies on coatings fabricated from other forms of Hydroxyapatite structures indicate that the resulting film morphology and the interfacial properties are the key parameters that controls the thin film stability. Keywords: Nano-Hydroxyapatite, Quartz crystal microbalance, Thin films Financial assistance given by the National Research Council Sri Lanka (NRC Grant: 15 004) is acknowledged

Resume : Ordered arrays or superlattices consisting of nanocrystals (NCs) of different diameter represent an important class of materials. There have been advanced methods to assemble nanoparticles of two different materials into binary nanoparticle superlattices (BNSLs).1 Recently, Rafal et al. has reported highly organized monocomponent helical structures formed from magnetic cubes.2 But this process is limited only to magnetic inorganic materials. On the other hand, there were no unique approaches to make highly organized non-close packed self-assembled structures in the size regime below 20 nm. For example, self-assembly of alkanethiol-protected gold nanoparticles can only give rise to close-packed structures such as hexagonal or FCC arrangements. It is challenging to produce superlattices of inorganic nanoparticles into loosely packed arrangements. Despite these advances in template-assisted arrangement of inorganic nanoparticles,3 little progress has been made over controlling the desired structure of the superlattices. Here, we developed a new approach based on post-modification of BNSLs to create unprecedented monocomponent nanoparticle crystals. We demonstrate the formation various non-close packed monocomponent structures. We have examined several different NP arrays as substrates for surface-enhanced Raman scattering (SERS) and found the best arrays for superior signal enhancement properties. 1. A. Dong, J. Chen, P. M. Vora, J. M. Kikkawa C. B. Murray Nature 2010, 466, 474. 2. G. Singh, H. Chan, A. Baskin, E. Gelman, N. Repnin, P. Král, R. Klajn Science 2014, 345, 1149. 3. S. Y. Park, A. K. R. Lytton-Jean, B. Lee, S. Weigand, G. C. Schatz, C. A. Mirkin, Nature 2008, 451, 553.

Resume : Magnetic metallic nanoparticles (NPs) are self-assembled, under specific conditions, in organized structures, called supracrystals [1]. Such self-organization process requires a small particle size dispersion as well as the use of an adapted coating agent preventing coalescence and oxidation. Supracrystals potential covers various fields, including electronics, charge transport and information storage. However, their thermodynamic properties have been little examined, particularly under high pressure conditions. The current work aims at establishing the temperature-pressure phase diagram of Cobalt-based supracrystals hold together via lauric acid chains. To this end, two experimental techniques were employed in combination with a resistive heated membrane diamond anvil cell (mDAC) for the generation of high pressures (0-20 GPa) and moderate temperatures (0-200 °C) conditions. First, low wavenumber Raman scattering was used to determine both spherical and quadrupole vibrational modes of individual Co NPs [2]. In addition, the collective vibrations of the supracrystal, and their dependence on temperature/pressure conditions, were detected with a pump-probe picosecond acoustics setup [3]. Lauric acid was studied separately in order to identify its contribution to the physical properties of the supracrystals. [1] I. Lisiecki et al., Adv. Mater. 15, 712 (2003). [2] G. Simon et al., J. Raman Spectrosc, 47, 248 (2015). [3]F. Decremps et al., Ultrasonics, 56, 129 (2015).

Resume : To date, studies of noble metal nanostructures and their use as biosensors, optical filters, plasmonic waveguides and in photovoltaic technology have attracted significant attention. The plasmonic properties of the metallic nanostructures can be tailored by varying different parameters such as size, shape, surface structure and particle spacing.1 In this work, we theoretically and experimentally investigate the plasmonic properties of periodic gold nano-triangle arrays. We fabricate large-area periodic gold nano-triangle arrays on glass substrates using a nano-sphere lithography method. The nano-sphere lithography technique is based on the self-assembly of polystyrene nano-spheres achieving a well-packed hexagonal mask, which leads to the formation of metal triangle nanostructures after metal deposition and mask removal. The field enhancement properties, induced by the triangularly shaped nanostructures arranged in hexagonal arrays, are characterized by a laser ablation technique.2 To better understand the optical behavior of this nanostructure, we perform numerical studies, based on finite-difference time-domain (FDTD) analysis and finite element method (FEM), modeling the electromagnetic field distribution of the targeted substrate. We study the field distribution as a function of input light polarization and nanostructure geometry. Our results indicate that the nanostructure-induced plasmonic properties alter by varying these parameters. In addition, our study provides important information for nanostructure design towards high electric field enhancement in thin film devices. Together with the prospect of low production cost and the ease of scalability, we believe that the presented nanostructures hold prospect to be beneficial for the optical enhancement in various optical and optoelectronic devices. 1. Hulteen, J. C. et al. Nanosphere Lithography:  Size-Tunable Silver Nanoparticle and Surface Cluster Arrays. The Journal of Physical Chemistry B 103, 3854-3863 (1999). 2. Fiutowski, J., Maibohm, C., Kjelstrup-Hansen, J. & Rubahn, H.-G. Laser ablation of polymer coatings allows for electromagnetic field enhancement mapping around nanostructures. Applied Physics Letters 98, 193117 (2011).

Resume : Graphene has been proposed as the current controlling element of vertical transport in heterojunction transistors due to its high mobility and 2D nature. Simulations of graphene acting as a thermionic barrier between the transport of two semiconductor layers have shown cut-off frequencies larger than 1 THz. Furthermore, along with graphene the use of doped amorphous silicon (a-Si:H) as the semiconductor for this approach could enable flexible electronics with high cutoff frequencies. In this work, we will present the fabrication of a vertical structure where graphene is embedded between two differently doped a-Si:H layers deposited by very high frequency (> 100 MHz) plasma-enhanced chemical vapor deposition on a rigid substrate. The operation of this vertical transistor is investigated by the two diode-like interfaces by means of temperature dependent current-voltage (IV) and capacitance-voltage (CV) characterization. It will be shown that the vertical current between the a-Si:H layers is successfully controlled by the ultra-thin graphene base voltage. While current saturation is yet to be achieved, high current gain values were obtained. These results show promising advances for the application of graphene base heterojunction transistors.

Resume : Charge recombination rate is at the essence of photocatalysis. Introducing a metal, is a common approach to decrease the energy loss through electron-hole recombination via electron transfer from the conduction band of the semiconductor to the metal [1]. Gold nanoparticles (Au NPs) have proven to be effective through both Mott-Schottky junction, and localized surface plasmon resonance (LSPR) properties [2]; these can be tuned by altering their shape and size [3]. Tailoring Au NPs size and morphology has been widely studied due to the benefits of LSPR in multiple fields [4]. Achieving a similar degree of morphology control of Au NPs deposited on a support would be extremely useful to the photocatalysis field. In this work, we show that non-spherical Au NPs could be directly grown on a visible light harvesting semiconductor: graphitic carbon nitride (Eg=2.7eV) [5]. A deposition precipitation method was used in presence of urea, a process used for spherical Au NPs deposition on TiO2 [6,7] and g-C3N4 [8]. However, our work demonstrates the preparation steps necessary to reduce the gold precursor to Au0 is of high relevance with regards to Au NPs shape. A mixture of various morphologies (nanorods, cubes, triangular nanoplates or tetrahedral) was obtained under reducing conditions. While work is in progress to understand the effect of reduction conditions on the Au NPs shape on g-C3N4, an increase in the reaction rate by 1.6-fold for the photocatalytic hydrogen evolution from oxalic acid, when compared to regular spherical Au NPs, was seen on these irregular shaped Au NPs. This increase might be linked to the enhancement of the electric field at the edges and corners of Au NPs [9] which in turn is poised to decrease the electron-hole recombination rate of the semiconductor. [1] V. Subramanian, E. Wolf, P. V. Kamat, J. Phys. Chem. B. 105 (2001) 11439–11446. [2] M.A. Khan, L. Sinatra, M. Oufi, O.M. Bakr, H. Idriss, Catal. Letters. 147 (2017) 811–820. [3] X. Zhang, Y.L. Chen, R.-S. Liu, D.P. Tsai, Rep. Prog. Phys. 76 (2013) 46401. [4] M.R. Langille, M.L. Personick, J. Zhang, C.A. Mirkin, J. Am. Chem. Soc. 134 (2012) 14542–14554. [5] K. Domen, X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J.M. Carlsson, M. Antonietti, Nat. Mater. 8 (2009) 76–80. [6] Z.H.N. Al-Azri, W.T. Chen, A. Chan, V. Jovic, T. Ina, H. Idriss, G.I.N. Waterhouse, J. Catal. 329 (2015) 355–367. [7] A. Hugon, L. Delannoy, C. Louis, Gold Bull. 41 (2008) 127–138. [8] S. Samanta, S. Martha, K. Parida, ChemCatChem. 6 (2014) 1453–1462. [9] S. Link, M.A. El-Sayed, Int. Rev. Phys. Chem., 19 (2000) 409–453.

Resume : Graphene, with its high optical nonlinearity and dispersionless nonlinear optical response over a broad wavelength range, has been investigated widely to implement optical devices such as fiber laser, broadband optical modulator, polarizer, and optical switches. Conventionally synthesized graphene relying on high temperature and vacuum equipment mostly requires deleterious transfer steps to implement devices that degrade the graphene crystal quality, thereby affecting the efficiency of nonlinear optical operation and lacking the customized patterning with minimized footprint as well as missing the facilitated fabrication process. Here, we present a laser induced in situ synthesis of multilayered graphene directly onto the optical fiber in ambient condition for absolute investigation of as-grown graphene crystal in optical domain. The evanescent field of an amplified continuous wave (CW) laser, propagating through the waveguide, provides activation energy for carbon atoms to diffuse through the nickel catalyst and to grow graphene directly on the waveguide. The in situ grown graphene shows nonlinear optical absorption property with the modulation depth of 3 % and acts as saturable absorber (SA) in the fiber laser ring cavity to generate ultrafast optical pulses, thus ensuring the passive mode-locking of fiber laser operating in femtosecond scale. We also demonstrate ultrafast all-optical switching near 1550 nm by capitalizing four-wave mixing (FWM) with the grown graphene to ensure that the nonlinear response enhancement of 66 % is originated from the graphene. The input signal channel is modulated at the ultrafast speed up to 20 GHz, and this modulation information is successfully copied to the newly generated signals.

Resume : The fabrication of metal/graphene contacts is one of the main technological issues in the development of graphene-based electron devices, whose performance strongly depends on the capability to achieve very low contact resistance. Gold contacts seem to be particularly promising from the experimental point of view, but few theoretical studies are available. Here we investigate the properties of two types of gold/graphene contacts: flat contacts – between vertically stacked layers of gold and graphene – and edges contacts – between the edges of a graphene layer and gold. We perform ab-initio simulations of electron properties based on Density Functional Theory (DFT) and quantum simulations of electron transport through the interface using the PWCOND module of Quantum Espresso. We show that the nature of the bonds formed in the case of different contact configurations has a strong effect on contact resistance and the formation of strong chemical bonds in the case of edge contacts leads to lower contact resistance.

Resume : Two-dimensional layered materials remain in focus of researchers, and recently heterostructructes of these materials have attracted a lot of attention. Graphene and hexagonal Boron Nitride (Graphene/h-BN) heterostructures constitute an important family of such materials. Consisting of layers of graphene and BN sheets with various stacking, vertical Graphene/h-BN heterostructures combine properties of both materials. Many different possible arrangements of heterostructures’ building blocks allow for design materials with desired properties and functionalities, for which the quantitative predictions of relation between morphology of the structures and their electronic structure play the crucial role. We present an in-depth theoretical study of graphene/h-BN heterostructures carried out in the framework of density functional theory. We focus on the relation between electronic and structural properties, and investigate the role of van der Waals interactions in these systems, using DFT-D2 scheme proposed by Grimme. The results of our investigations shed light on physical mechanisms that determine the magnitude of the energy band gap and provide a tool for band gap engineering in graphene/h-BN systems. Results of present studies for Graphene/h-BN heterostructures have been compared to other theoretical works and available experimental data.

Resume : Monolayer molybdenum disulphide (MoS2) is a promising candidate in optoelectronics due to its strongly-bond excitons and their non-linear optic behaviour. However, the low refractive index characteristic of this two dimensional (2D) material results in poor light-matter interactions. We demonstrate a strategy to enhance photoemission of CVD-grown MoS2 for more than 20-fold by embedding designed silver nanostructures in the monolayer structure. This is achieved by fabrication of silver nanodisc arrays able to generate localized surface plasmon resonance (LSPR) collective modes, with addition modification as dimer and trimer with 30 nm gap and 400 nm pitch to maximize light- matter interaction. The dimers and trimers were embedded using O2 reactive ion etching (RIE) assisted with a designed mask. This designed arrays led to prevailing exciton over trion recombination, which enhance photoemission of monolayer MoS2. In summary, RIE defect engineering of MoS2 in order to make nanohole arrays along with coupling modified LSPR supported silver nanostructures leads to enhancing light-matter interaction and consequently increment in photoluminescence of MoS2. This project is supported by the Research Grant Council of Hong Kong SAR (Project Number 16204815), the Innovation and Technology Commission (ITS/267/15). We appreciate support from Center for 1D/2D Quantum Materials, financial support from the Guangzhou Science & Technology Project (2016201604030023).

Resume : Biomolecule-graphene composites continue to gain attention for their use in biomedical and biotechnological applications, such as: next generation biocatalysis, biosensors, implantable electronic devices, or drug delivery. In this study, three commercial graphene derivatives: graphene oxide (GO), graphene oxide nanocoloids (GOC), and polycarboxylate functionalized graphene nanoplatelets (GN), were compared as biomolecule carriers. ATR-FTIR analysis showed that GO and GOC were similar in functional groups content, and very different to GN. The α-L-Rhamnosidase RhaB1 from the bacterium Lactobacillus plantarum, a relevant enzyme in the pharma and food industries, was immobilized on the materials. RhaB1-GO and RhaB1-GOC showed a high binding efficiency, while the enzyme loading on GN was low. Regarding the biochemical properties of RhaB1-GO, RhaB1-GOC, and RhaB1-GN, the thermal stability and the effect of pH on the activity of all immobilized enzymes was similar to that observed for the free enzyme. Also, the Km for the immobilized and soluble enzymes was the same. However, the activity-temperature profiles and the response to different inhibitors varied significantly between them. Finally, the free RhaB1 and the immobilized enzyme in GOC showed the highest stability degree, keeping almost the 100% their initial activity at least after 8 weeks of storage at 4 °C. This study shows that distinct graphene derivatives can influence differently on an enzyme catalytic properties.

Resume : Need for fabrication of low temperature gas sensors has fostered extensive research in realizing 2D materials with high surface area for fast response and low ppm detection of volatile organic compounds (VOCs) [1-2]. In this work, a fast response and low ppm acetone gas sensor operating at near room temperature has been fabricated successfully by utilizing cubic mesoporous g-CN (commonly known as g-C3N4), synthesized through template inversion of mesoporous silica, KIT-6 [2-3]. Upon exposure to 20 ppm acetone at 200 C, the optimized In(III)-SnO2/g-CN showed significant higher response (Ra/Rg = 18.2), fast response (14 s), and full recovery within 4 s in air. The sensor was also able to detect 20 ppm (R=1.7) and 50 ppm (R=3.9) acetone gas at 80 C. Compared to mesoporous In(III)-SnO2, the g-CN supported In(III)-SnO2 nanocomposite shows 2.8 fold increase in response to acetone gas while reducing the operating temperature by 50 C. This outstanding response is due to easily accessible 3D mesoporous structure with higher surface area and their unique planar morphology of In(III)-SnO2/g-CN [3-4]. The findings reported in this study shows promising glimpse for designing a novel strategy to the development of ultrasensitive VOCs sensors working at low operating temperature [5]. Refs: [1] ACS Omega 2, 2017, 3658; [2] J. Mater. Chem. A 5, 2017, 14134; [3] Sensors Actuators B: Chem. 253, 2017, 703; [4] Sensors Actuators B: Chem. 239, 2017, 364; [5] J. Mater. Chem. A 4, 2016, 1033.

Resume : In search of new energy sources, photoelectrochemical splitting of water to produce hydrogen is a viable approach to transform sunlight into chemical energy, which has triggered a quest for suitable photocatalysts. Among different semiconductor metal oxides, hematite (?-Fe2O3) has emerged as a promising photo-anode material for water oxidation since it is cheap, abundant, non-toxic and stable under photoelectrochemical conditions. Although it promises high theoretical photocurrent densities (11?14 mA/cm2), corresponding to a solar-to-hydrogen (STH) efficiency of 14-17 %, these values can hardly be attained since hematite suffers from high resistivity,] short lifetime of the photoexcited charge carriers, and short hole diffusion length (2-4 nm). Few of these limitations can be overcome by optimizing the nanostructure and electronic properties, as recently shown in a number of studies. In this study, we have focused on Interfacial modification of ?-metal oxide multilayer photoanodes deposited by plasma enhanced chemical vapor deposition (PE-CVD). Different mechanisms such as heterostructuring (Fe2O3//TiO2), nano-structuring, patterning of multilayering with different structure (bar structure or line structure) or graphene supporting were examined in this study. The bilayer electrode exhibited enhanced PEC responses in terms of a lower onset potential and a higher photocurrent density when compared to the single layer ?-Fe2O3 electrode. This enhancement was observed to be due to synergistic light absorption with the bilayer electrode, although charge carrier recombination occurred faster due to interfacial defect states. The incorporation of a graphene layer between the ?-Fe2O3/TiO2 double layer and the FTO substrate resulted in a doubling of the photocurrent, but lead to a loss of the synergistic effect between the two active metal oxide layers. However, depositing the graphene between the two metal oxide layers resulted in an even higher photocurrent, while retaining the enhanced onset potential of the double layer electrode. This enhancement was observed to be due to either the passivation of the oxide defect states or enhancement of the charge transfer between the two oxide layers.

Resume : Copper- or manganese-doped zinc sulfide nanostructure arrays draw close attention due to their great promises in development of modern optoelectronic devices including light sources, optical touch panels or fluorescent labels. The work is focused on development of cheap pathways for formation of ordered ZnS:Cu(Mn) nanosized dot arrays formed by condensation of thermally evaporated ZnS and Cu2S powders in the pores of highly-ordered anodic alumina matrix in ultrahigh vacuum. Matrices with pore diameters of 40, 60 and 120 nm and thickness of interpore walls of 15 ( -5) nm were formed in aluminum plate and glass substrates. ZnS:Cu(Mn)@AAO composites were study by SEM, EDX, XPS, UV-VIS spectroscopy, X-Ray Diffraction and EXAFS-spectroscopy methods in comparison with ZnS:Cu(Mn) thin films. SEM studies shown that the form and arrangement of semiconductor nanostructures replicates well the form and arrangement of matrix channels. EDX analysis shown the penetration of deposited materials into pores to a depth of 3 micron. Luminescent and electroluminescent properties have been also investigated. The samples exhibit luminescence in a visible region depending on type and concentration of dopant atom and pore size of matrix. The work is supported by Russian Scientific Foundation (Grant ? 15-19-10002) and Russian Foundation of Basic Researches (Grant ? 16-48-180303).

Resume : In recent years, an intense interest has emerged in the fabrication of semiconductor nanowires (NWs) based solar cells. Si NWs are potential candidates due to various advantages, including cost-efficiency, well-balanced electrical and optical properties, and well established processing techniques. They exhibit excellent antireflection behavior because of tunable optical absorption in a wide wavelength range originating from multiple scattering by NWs. On the other hand, CdSe based core/shell (core/alloy) QDs has a great potential in boosting light harvesting efficiency with the advantage of adjusting band gap energy to cover most of the visible light wavelength. Here we report, two fasil way in coating Si NWs with the CdSe/CdxZn1-xS (0≤x≤1) Core/Ternary shell nanocrystals to enhance light to current conversion. Well aligned p-Si NWs, were successfully synthesized by a Ag-assisted electroless etching technique which are uniformly distributed over the surface of p-type Si wafer. Si NWs coated with the synthesized QDs through spin coating and chemical bath deposition techniques. Investigate its device characteristics based on current–voltage (I–V), capacitance–voltage (C–V), and photo responsivity measurements.

Resume : Newly developed SiO2 materials, prepared by sol-gel method, were proved to be able to absorb the light in a broad wavelength range due to formation of large number of optically active defects. Localized lattice defects, such Si3+ and oxygen-related imperfections (i.e. O-, O2-, O22-) formed under UV light irradiation in presence of O2, impact positively on both light absorbing properties and photocatalytic activity for methanol reforming. The SiO2 based materials were extensively characterized by a bunch of experimental techniques, such as SEM, AFM, FT-IR, UV-VIS, XPS, XRD and BET. High formation rate of photocatalytically produced H2/CO2 was observed over tubular SiO2 exposed to simulated solar light (AM 1.5) compared to other standard photo-active materials (i.e. TiO2-based compounds). The specific mechanism of methanol photo reforming over SiO2 was analyzed and some specific reaction paths were identified.

Resume : Retinitis pigmentosa (RP) or age-related macular degeneration are degenerative diseases for which the degeneration of natural retinal photoreceptors is responsible for blindness of over 15 million people worldwide. Despite many therapeutics approaches, these diseases still remain incurable presently. One curative approach is the development of retinal prosthesis which consists in replacing the degenerated photoreceptors by a photoreceptive film to stimulate the partially-persistent neuronal network. Thus, our approach is to engineer inorganic photo-sensitive TiO2-based thin films for absorbing solar light and acting as artificial photoreceptors. Firstly, vertically aligned TiO2 nanotubes (NTs) were synthesized through an anodisation process of a Ti foil. A successful activation ex-vivo of retinal neurons on retinas from mice affected by RP was observed on bare TiO2 NTs under UV light. Films were pixellized and miniaturized by laser etching, allowing a subsequent surgical implantation in the eye. To increase light absorption and switch the NTs photo-response from the UV toward the visible light, graphitic-carbon-nitride (g-C3N4) was grafted on the NTs by thermal decomposition of a mixture of melamine and dicyandiamide. The photo-response of bare and g-C3N4 grafted-NTs were measured by electrophysiology when illuminated in the UV range (365 nm) and in the visible range in acellular condition in PBS. The results showed that both grafted and bare NTs exhibit a good photo-response in the UV part (approx 30 mV). However, whereas the photo-response of bare TiO2 is null in the visible range, grafted NTs showed a depolarization of about 1.4 mV. Ex-vivo activation of retinal neurons of mice is currently tested on g-C3N4 grafted NTs.

Resume : Nanocomposites have gained a wide interest in many applications including water treatment. In the present study, a variety of novel magnetic nanocomposites (MNCs), using graphene and cobalt ferrites, were synthesized by solvothermal process. In order to gain an insight into their physico-chemical properties, MNCs were characterized using X-ray diffraction, field emission-scanning electron microscopy, high resolution-transmission electron microscopy, vibrating sample magnetometer, X-ray photo spectroscopy, Brunauer?Emmett?Teller analysis and Fourier infrared spectroscopy. Further, the water purification studies were performed in order to examine the potential of MNCs in removing a wide array of aquatic pollutants (e.g. metal ions, dyes, pharmaceuticals). Experimental conditions were optimized to achieve the maximum removal of pollutants from water by synthesized MNCs. Modeling with the experimental data was also performed to describe and elucidate the mechanism of the process. The prepared MNCs exhibited considerable removal efficacy for studied pollutants. Regeneration experiments were also performed which revealed that prepared MNCs can be reused for multiple cycles without losing the original capacity. The results of this study revealed that the prepared MNCs are efficient in the removal of a wide array of aquatic pollutants thus, making them a potential candidate for water treatment.

Resume : Conversion of solar energy into chemical fuel in a photoelectrochemical (PEC) devices requires an inexpensive and stable semiconductor photoelectrode materials with explicit control over the three main requirements in a single material system: 1) chemical stability 2) visible light absorption and 3) band edges matching to redox levels of water. This talk will summarize the results obtained for photoelectrochemical water splitting using metal oxide semiconductor such as BiVO4, TiO2 and α-Fe2O3. Our attention has been devoted to further modify these oxide semiconductors by using various strategies such as band edge engineering, material disordering, nano/micro engineering, surface/interface engineering to improve the performances of metal oxide-based materials, especially favoring the photoelectrochemical activity under simulated sunlight. Recently, a new engineering strategy, i.e., band re-alignment of BiVO4/TiO2 at the heterostructure was achieved by gas–phase modification technique of the top TiO2 layer which strongly promotes interfacial interaction at the junction and leads to an effective interfacial charge separation and charge transport. The modified BiVO4/TiO2 heterostructures exhibit significant enhancement of visible light absorption and improve the photoelectrochemical response. Keywords: metal oxides, energy conversion, charge recombination, photoelectrochemical, hydrogen production.

Resume : Self-doped semiconductors are promising class of highly efficient photocatalytic materials because the electronic properties can be controlled without sacrificing the chemical and thermal stability of the parent material. In this report, we report facile synthesis of Sn2+ self-doped SnS microparticles via a straight forward template-free hydrothermal route. Due to the ability to successful tune band structure while reducing defect generation, self-doped SnS could potentially serve as promising photocatalyst of waste water. Here, Sn2+ self-doping results in insertion of an energy level slightly below the conduction band of SnS, thereby decreasing the photoexcitation energy. Moreover, dopant sites can act as charge trapping sites, which can subsequently minimize problematic charge recombination. Synthesized materials were characterized by various spectroscopic, microscopic, and surface characterization techniques, all of which confirmed the formation of self-doped SnS. Sn2+ self-doped SnS photocatalyst successfully reduced carcinogenic Cr(VI) to the water-insoluble Cr(III) form under visible light illumination. The best photocatalytic efficiency was obtained from an optimal balance between increased numbers of trapping sites leading to longer charge carrier lifetime, and decreased distance between trapping sites, favoring charge recombination. We expect that similar methodologies can be applied to other non-stoichiometric semiconducting photocatalysts with tunable electronic properties and enhanced photocatalytic efficiency.

Resume : In the current work, Cu2XSnS4 (X = Zn, Mn, Ni, Fe and Co) thin films were grown via one-step electrodeposition technique following sulphur-free annealing procedure at 500oC for 60 min and applied as counter electrodes (CEs) instead of high-cost platinum in dye-sensitized solar cell (DSSC). The physical, structural and electrochemical properties of CXTS thin films were studied by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammogram (CV) measurements. XRD and Raman analyses reveal that CXTS films possess fine crystallite structure with no secondary phases. Furthermore, the CXTS CEs demonstrate a densely packed and rough surface morphology, suggesting a large surface area and high conductivity. Moreover, CV analyses confirm that the electrocatalytic activities of the CXTS CE were ordered as Cu2CoSnS4>Cu2FeSnS4>Cu2ZnSnS4>Cu2NiSnS4>Cu2MnSnS4 due to the highest conductivity of Co, the better crystallite and the largest surface area of Cu2CoSnS4 CE. As a result, power conversion efficiencies were extracted from current density-voltage (J-V) as 3.0% 2.94%, 2.40%, 1.93% and 1.1% for Cu2CoSnS4, Cu2FeSnS4, Cu2ZnSnS4, Cu2NiSnS4 and Cu2MnSnS4 CEs based DSSCs, respectively. This can be ascribed to similar trend of electrocatalytic activities of CXTS thin films. As expected, the Cu2CoSnS4 shows the longest electron lifetime and best start/stop capability while Cu2MnSnS4 based cell exhibits the shortest electron lifetime and the lowest start/stop capability. The obtained results suggest that CXTS thin films synthesized via one-step electrodeposition technique can be promising candidate instead of Pt for low-cost and highly efficient DSSCs owing to their composition include earth abundant materials and their simple fabrication processes. Acknowledgement–This study was supported by the European Union through the COST Action MP1407 “Electrochemical processing methodologies and corrosion protection for device and systems miniaturization (e-MINDS)”, and by the Scientific and Technological Research Council of Turkey (TUBITAK Grant Number 115M762) who provided financial support for this research.

Resume : Three-dimensional (3D) porous carbon structures have been widely investigated for myriad applications because of their versatile characteristics and inherent attractive properties such as light weight, low density, large surface area, high porosity and excellent electrical conductivity. Especially, the unique structure of carbon aerogels (CAs) with an interconnected framework, present many structural advantages like more accessible bulk and active surface, fast ion diffusion with enhanced mass transport rate. However the tedious synthetic conditions, need of template and high cost associated with potential environmental risks are the major obstacle for their large-scale processes. Herein, we report on a facile, efficient and green strategy for the synthesis of lightweight and highly porous carbon aerogels from bio-mass as low-cost precursor by hydrothermal treatment followed by post carbonization. The hierarchical porous structures is basically assembled by internally connected network of dendritic-linked carbon architecture and numerous macropores. The biomass-derived carbon aerogels hold considerable potentials as in low-cost, environmentally friendly and high performance and electrode material. These carbon aerogels shows outstanding capacitive performances of 120 F g-1 in two-electrode systems without using any activation agent.

Resume : Heterogeneous photocatalysis offers great potential for a variety of applications by converting photon energy into chemical energy. It has been established that the size and the shape of a semiconductor particle play an important role in photocatalysis. Quantum confinement often leads to a transition from continuous to discrete energy levels affecting remarkably the photocatalytic activity concerning the smallest nanoparticles (NPs). We synthesized silicon carbide (SiC) NPs with different size around the radius of exciton Bohr radius of SiC, in order to study the photocatalytic activity of a nanoparticle when energy levels transform from continuous to discrete levels. We found that SiC NPs with size below the twice of exciton Bohr radius show negligible activity, whereas larger particles become active. Our results clearly imply the importance of the size of semiconductor NPs for their photocatalytic activity. Furthermore we found that the colloid solution of smaller and larger NPs together shows enhanced photochemical activity with doubled efficiency with respect to the solution with large NPs only. The solution with mixed NPs did not show any long-time association or aggregation. A study of reaction kinetics revealed an energy transfer between the larger and smaller NPs and an adsorption-desorption controlled mechanism between the NPs that indicates a temporary formation of type II homojunction, i.e., the size differences of SiC NPs leads to varying band edges (or highest occupied and lowest unoccupied levels) with type II junction. This system demonstrates that fine tuning of size and surface termination of semiconductor NPs is inevitable to control its photocatalytic efficiency.

Resume : Here we report instantaneous ligand exchange of Cu-In-S/ZnS core-shell quantum dots from hydrophobic ligands such as 1-octadecene (ODE) to hydrophilic ones such as 11-mercapto-1-undecanol (MUD) and 6-mercapto-1-hexanol (MCH) by using flash lamp exposure. We utilized light source to alternate heat source in traditional in-situ ligand exchange methods. The experiment was carried out by exposure of the quantum dots, in solution with high concentration of target ligands, flash lamp having 300nm to 800nm with wide wavelength width range. The output were examined by PL, UV Vis, and TCSPC devices, and high ligand exchange rate with minimal PL reduction was observed. The result shows that the flash lamp can be a promising way to alternate heat source in in-situ ligand exchange, remarkably reducing processing time of the process and greatly enhancing further experimental efficiency.

Resume : Colloidal semiconductor nanocrystals (NCs) are promising materials for the application in light-emitting devices, photodetection and solar energy conversion. Most of the previous fundamental studies and potential applications have been focused on Group II-VI QDs such as Cd-based chalcogenides. However, the toxicity associated with cadmium could impose critical constraints for practicable applications. Indium phosphide (InP) QDs have been suggested as the most promising candidate to replace Cd-based QDs due to their band gap tunability covering the entire visible range and narrow spectral bandwidth. Nevertheless, two major challenges need to be addressed to unlock the full potential of InP QDs in display application. Firstly, the size distribution in InP QDs need to be improved, which in turn will contribute to narrow emission linewidth and improve the color purity. Secondly, robust control over the particle size need to be achieved. In this work, we present an improved synthetic method to synthesize high quality Cd-Free NCs. The emission spectra of the QDs can be continuously controlled from 488 to 640 nm with narrow emission linewidth. We will also present a key parameters for fabrication of large area luminescent QD sheet for commercial optoelectronic devices (i.e., QLED displays).

Resume : We measured the adsorption of protein monolayers on different nanostructures using in situ spectroscopic Kretschmann ellipsometry. The nanostructures (e.g. platina nanoparticles, TiO2 nanotubes) were made by spin coating on glass substrates with a 40 nm thin gold layer. During the in situ investigations we used a home-made semi-cylindrical Kretschmann-Raether flow cell [1,2], so we could use the surface plasmon resonance (SPR) phenomenon to increase the sensitivity of the measurement [4]. Compared to traditional SPR devices [2,3] the ellipsometer provided the phase information of the reflected beam, so we obtained more information that enabled us to increase the sensitivity by one order of magnitude compared to the case of having only amplitude information. The other advantage was that we could choose the SPR angle very precisely (within 0.1 degree) and we used a broad wavelength range from 400 nm to 1690 nm. Using a spectroscopic ellipsometer gave us the opportunity to build a complex optical model and use it to study the adsorbed protein layer quantitatively. The optical model we built successfully described the structure, so we registered in situ information about the adsorbed protein. The best nanostructure was identified with FEM (finite element) simulations, the protein adsorption was modeled also with RSA (random sequential adsorption) and then the numerical results were compared with the measurements.

Resume : Graphene membranes present remarkable electronic and thermal properties, which make them a very promising material for several applications, such as in electronic devices. However, in spite these properties, good graphene/metal electrodes interfaces have been difficult to achieve. The structural graphene/metal mismatch drastically reduces thermal and electronic conductivities. One experimentally approach to address this issue has been high-temperature annealing [1]. Significant improvements in thermal and electrical conduction has been obtained in this way, but the underlying mechanism behind these processes are still elusive. In this work, using fully atomistic reactive molecular dynamics simulations (FARMD), we realistically model the system in order to observe the annealing influence in the interaction between multi-layers graphene and metallic electrodes (nickel and gold). Our results show that the annealing produces an upward and downward movement of the graphene membranes, which lead to atomic polishing-like phenomena and makes the metallic electrode surface flatter. This atomic planarization improves the coupling between graphene and the metallic electrodes and, consequently, contribute to better thermal and electronic conductivities. Acknowledgment: We thank the Brazilian agency FAPESP financial support and the Center for Scientific Computing (NCC/GridUNESP) of the São Paulo State University (UNESP). [1] V. A. Ermakov, et al., Nanotechnology 24 (2013) 155301.

Resume : In modern technology the developments in environmental areas become more important and current. Freshwater stocks and pollution are in the most relevant topics, as they can be crucial in the future of humankind. Within the “WaterSafe” international project, we take part in the development of a device for detecting various water pollution molecules, mainly heavy metal ions. The sensor surface can be a mix of dielectrics, nanostructures or genetically modified bacterial flagellar filaments (FF) that have specific binding sites for the target molecules. The adsorption of the molecules to the immobilized filaments induces a change in the conductance of the electronics which can indicate the presence of the pollution. The main aim of our group is to create the sensing layers by immobilizing the FFs on the sensor surface. Either genetically modified FFs were used, which have sulfur molecules on their surfaces, thus they can develop covalent bonds with the gold surface, or unmodified FFs were immobilized using a chemical cross-linker molecule (DSP). Various titanium-oxide-based surface nanostructures were prepared on the substrates in order to facilitate the adsorption of the FFs. The coverage of the FF layers is investigated in situ by plasmon enhanced spectroscopic ellipsometry and ex situ by AFM, SEM and ellipsometric scanning of the surfaces.

Resume : Fullerenes and nanotubes are between the great discoveries of materials sciences in the last few decades and motivated many studies regarding the search for new materials. One option to be explored is the search for materials with nanostructure geometrically similar to that found for carbon based materials but based in other elements, like Si, Ge, or B and N, or As and Ga, etc. In the present work, we investigate some of these interesting possibilities, our study is focused in the possible existence of closed cage molecules with architecture inspired by the usual fullerenes, but based in other elements. We considered atoms from three different columns of the periodic table of the elements, namely the column of boron, of carbon and of nitrogen. The tests include architectures similar to that of the C60, C20 and that of the recently experimentally synthesized B40. Our calculations indicate that a few of these clusters can be stable at room temperature. Some of these structures are stable only when passivated by hydrogen atoms in the exterior region. We also investigate the electronic structure of these clusters including their absorption and emission spectrum as well their reactivities, calculated by the Fukui indices.

Resume : Nanometric TiO2 and ZnO are the most preferable photocatalytic semiconductor materials, due to their excellent chemical stability, environmental sustainability, nontoxicity and low cost. However, they are limited as sunlight-driven photocatalysts, due to their band gap (ca. 3.2 eV for both), which a photon with wavelength ≤ 400 nm, which means that a UV light source is mandatory. A possible way to overcome this limitation is using a supporting material such as a persistent luminescence material (PeLM). In fact, the PeLM is able to be charged with either natural or artificial radiation and, glowing in darkness, provides the necessary photons to the catalyst (1). The coupled system has applications in wastewater treatment, being particularly effective in the treatment of contaminated water with pharmaceuticals and in turbid wastewaters. A solid state synthesis was performed to obtain the coupled system: amorphous TiO2 powders, ZnO powders (2) and PeLM powders were suspended together in water, dried in an oven at 105 °C for 12 hours and eventually subjected to a thermal treatment for 1 hour at 350°C. Several samples were prepared and chemical physical characterized, and their photocatalytic activity was evaluated using a methylene blue solution. The resulting best samples were also tested on a turbid solution and an aqueous solution contaminated with an antibiotic. 1. Locardi F. et al. Catalysis Communications 2016, 74, 24-27 2. Lova P. et al. Physica Status Solidi (c) 2015, 12 (1-2), 158-162

Resume : Metal and dielectric nanostructures play an important role in several fields such as nanophotonics, optoelectronics, solar cells and sensing. Nanostructured arrays of artificial atoms may be obtained by different methods as reported in the literature. Many of lithographic methods used for manufacturing of these so-called metamaterials rely on using of polymers. In this work we investigate the optical properties of polymethyl metalacrylate (PMMA ) films obtained by spin coating deposition on glass and glass/ITO substrates. The refractive index and extinction coefficient were investigated as a function of the deposition conditions and of post-deposition ion-beam treatment. Focus Ion Beam (FIB) milling was used to fabricate nanostructured arrays on the PMMA surface which is used as a template for the fabrication of optical multilayers. A thin ITO film was deposited by radio frequency sputtering on a glass substrate prior to PMMA deposition in order to avoid excessive surface charging upon the FIB bombardment which may cause polymer degradation. Different concentrations of PMMA in anisole solvent were used for obtaining PMMA films of various thicknesses in the range 200-800 nm, aiming to maximize films' thickness accuracy and reproducibility of optical properties. The optical constants (refractive index and extinction coefficient) and thickness of PMMA films were inferred by fitting transmittance and reflectance spectra measured by a commercial spectrophotometer. The structural change of the polymer upon ion bombardment was observed by SEM in the vicinity of the treated areas and the effective refractive index of the treated nanostructured PMMA was investigated.

Resume : A reliable and non-destructive depth dependent characterization of layer stacks is an important topic in many fields of research. The metrological challenges to sufficiently characterize such systems with respect to their structure-property relationships require a further development of the current analytical techniques in parallel to the quickly increasing complexity of systems to be analyzed. A combined analysis using Grazing Incidence X-ray Fluorescence (GIXRF) and X-Ray Reflectometry (XRR) as proposed by de Boer [1] has already been shown to be capable of contributing to the in-depth analysis of nanoscaled materials. Here, the general approach to model the two experimental data sets using the density ρ, thickness d and roughness σ of each layer as the parameters can quickly result in numerous degrees of freedom and thus unreliable results [2]. In this work, XRR is combined with PTB’s reference-free GIXRF [3], providing a direct access to the mass depositions (ρd) of the present materials. This allows for a significant reduction of the degrees of freedom within the combined GIXRF-XRR modeling and thus improves the characterization reliability of the methodology. Employing the in-house built instrumentation [4] and radiometrically calibrated detectors at the laboratory of the PTB at the BESSY II synchrotron radiation facility, the reference-free GIXRF-XRR method is demonstrated using the example of Al2O3-HfO2 nanolaminate stacks. References [1] D. de Boer et al., Spectrochim. Acta B 46(10), 1323 (1991). [2] P. Hönicke et al., Phys. Stat. Solidi A 212(3), 523 (2015). [3] M. Müller et al., Materials 7(4), 3147 (2014). [4] J. Lubeck et al., Rev. Sci. Instrum. 84, 045106 (2013).

Resume : Studies on the fabrication of sol-gel optical composite materials for photovoltaic devices and (or) planar optical waveguide are continuously caring attention over the years because this material has numerous applications in the field of microelectronics and optoelectronics. However, for oxides many difficulties have to be faced to obtain defect-free, high fidelity, structurally stable films for application in devices. We studied factors strongly influence on the characteristics of the thin hybrid film which would help to tune their quality of surface and body, developed the self-assembled technology based on the sol-gel method to fabricate high-quality hybrid nanocomposite films using network-forming oxides such as silica or titania that allows to variate different types of inclusions. Increase of concentration barrier of quenching of the luminescence and create conditions for waveguide propagation of laser radiation in the film will be the factors significantly influence the film luminescence efficiency and consequently the final laser performance. The possibility of controlling dye locations allowed increasing its concentration several orders compared to conventional materials without reducing the quantum yield of luminescence[1,2]. Preliminary results show that these photosensitive nanostructured films demonstrate nonlinear optical response under excitation of optical pulses of nanosecond duration[3]. The ability of ultrafast excited-state dynamics of composite films containing Rh6G was examined for their potential use as the photonic layer in an all-optical switching device and have obtained the recording of a dynamical grating in a single-pulse regime. Moreover for both films, we observed lasing, which appears as radiation of the central beam that consists from enhanced luminescence (along with track) and occurring due to the distributed feedback grating of enhancement created by the oncoming waves of the enhanced luminescence. Two order reducing the threshold pump intensity and changing the shape of lateral beams under changing TiO2 matrix instead SiO2 one is evidence of formation the waveguide amplifier in the TiO2 film. These results show possibility high-quality lasing on the basic mode of a waveguide that forms the central beam. This work would help on the manufacturing of mesoscale surface patterning of other hybrid films of mixed oxides for the perspective application as active optical materials. [1] A. Kazakevičius, L. Valkunas, E. Leonenko, G. Telbiz and V. Gulbinas Insights into the mechanism of enhanced Rhodamine 6G dimer fluorescence in mesoscopic Рluronic-silica matrixes // Journal of Phys.Chem. C (2015), 119, 19126−19133 [2]. G. Telbiz, E. Leonenko, M. Dvoynenko Оptical properties of Rh6G molecules ordering in the silica- and titanium dioxide mesoscopic sol-gel films//Molecular Crystals and Liquid Crystals (), vol. , – [3] G. Telbiz, S. Bugaychuk, E. Leonenko, L. Derzhypolska, V. Gnatovskyy, I. Pryadko. “Ability of dynamic holography in self-assembled hybrid nanostructured silica films for all-optical switching and multiplexing”, Nanoscale Research Letters, 10:196, p. 1-7 (2015).

Resume : Organic electrochemical transistors (OECT) have been extensively studied as an effective platform for chemical and biological sensing applications, based on their advantages on low-voltage operation, good biocompatibility and interaction with aqueous medium. However, conventional OECTs are normally fabricated in the scale of millimeter or larger, resulting in a slow response time for device operation. To overcome this problem, here we develop a novel approach to miniaturize OECT by using photolithographic technique. The channel of OECTs could be reduced to several to twenty microns therefore the speed of device response could be raised up to order of 10^-5 s in aqueous medium. Due to the improvement in transient response time of the micro OECT device, alternating current (AC) is possible to be introduced for device operation. Combined with lock-in amplifier, the small AC channel signal could be precisely extracted from an extremely noisy environment, which provides the possibility to enhance the sensing capability of the OECT devices in complex situations. The detection limit of dopamine, an important neuro transmitter within the central nervous system, is down to 10-9 M. In conclusion, we introduce a simple and easy-to-fabricate process for miniaturization of OECT devices to the cellular dimensions. The advantage of fast transient response makes the AC-driven micro OECT capable of in-situ cell activity monitoring and associated chemical sensing applications.

Resume : Bacterial cellulose (BC) membranes are produced by some bacteria such as the specie Gluconacetobacter xylinus and commercially used as wound dressing. BC membranes have high crystalline 3D network composed by pure cellulosic fibers with diameters below 100 nm and lengths larger than 3 μm. BC membranes fulfill several pre-requisites as ideal material for biological interface. BC membranes have good adherence to the wound, enable excellent water vapor permeability, and constitute physical barriers for microorganisms. In particular, BC membranes have been poorly explored as substrate for biosensensing materials based on sensors. Voltammetric sensors based on screen-printed carbon electrodes (SPCE's) built on BC membranes may have an incredible potential to be used in biology–device interface. As a proof-of-concept, we evaluated the voltammetric behavior of well-known model analytes in SPCE's printed on BC membranes. The SPCEs were home fabricated over dried BC membranes substrate using a screen printer machine IMAH and appropriate stencil designs fabricated on polyester screens (150 meshes). First, a carbon layer was deposited on BC substrate using a pattern comprising the electrical contacts and the working and counter electrodes. They were obtained SPCEs with a working electrode area of 0.09 cm2 and films thickness (determined by profilometry measurements, n=9) of 8.7 µm for Ag/AgCl and 9.2 µm for carbon films. By using BC membrane as substrates for SPCE, we successfully detected uric acid, pyrogallic acid and ferrocyanide and ferricyanide ions model analytes dissolved in aqueous solutions at concentrations up to 60 ppm, 1 mM and 5 mM, respectively. We also evaluated the modification of SPCE working electrode with inkjet printed metallic nanoparticles and tyrosinase enzyme. Taking advantage of their remarkable biocompatibility, BC membranes can be considered an excellent choice as an emergent biopolymer for the development of future implantable biosensors.

Resume : Gold nanoparticles (Au NPs) were formed by electroless deposition of gold on meso- and macroporous silicon with different porosity from an aqueous solution of potassium dicyanoaurate(I) and hydrofluoric acid. Deposition time was varied in the range from 30 to 70 minutes. The morphology and optical properties of Au NPs were analyzed using SEM, reflection and Raman spectroscopies. Au NPs were found to deposit both on meso- and macroporous silicon according to the layer island mechanism of thin film growth. Analysis of the reflection spectra allowed to determine a location of the surface plasmon resonance band and its intensity for each sample. We also revealed that variation of the porous silicon porosity and the gold deposition time led to different enhancement of the Raman signal from rhodamine 6G (R6G) in micromolar concentration adsorbed on the surface of the gold-coated porous silicon. The measured SERS-spectra correlated with the morphology of Au NPs, porous silicon type and regimes of the gold deposition. The greatest enhancement of Raman signal from R6G molecules was provided by gold-coated macroporous silicon. Its intensity was twice more than that from Au NPs on mesoporous one.

Resume : Redox-based memristive devices (ReRAM) based on ultrathin metal/metal oxide/metal stacks are considered as one of the most promising approaches for future high-density non-volatile data storage and beyond-von Neumann architectures including logic-in memory and neuromorphic applications [1]. Fast switching events on time scales of nanoseconds combined with data retention times in the order of ten years are enabled by the nanoscale redox-type reactions in the ReRAM cells that control the addressable resistance states. Therefore, ReRAM cells can only be understood if their mixed ionic electronic structure is considered. This applies to the material and stack design as well as to the modelling approaches. In other words, differences in the oxidation enthalpies as well as oxygen diffusion coefficients in the respective materials become equivalently important as have been the band gap and permittivity values for capacitive storage devices in the past. In this talk, I’ll summarize different actual trends in the design of materials stack combinations for memristive and for selector elements. Furthermore, I’ll introduce concepts for their high density integration spanning the range from crossbar and pillar-type cells to vertical 3D ReRAM approaches. [1] D. Ilemini, R. Waser, ‘Resistive Switching - From Fundamentals of Nanoionic Redox Processes to Memristive Device Applications’, Wiley-VCH, United Kingdom (2016)

Resume : Here we describe the self-assembly of metal-organic nanoparticles forming 2- and 3- dimensions mesoscopic high-ordered superstructures solvent-triggered using solvent vapour annealing (SVA). We used nanometric, atomically monodisperse molecular complexes with formula Ag44(SR)30 (a.k.a. intensely and broadly absorbing nanoparticles: IBANs) of silver as building blocks. IBANs feature a radius of ≈ 2 nm, and a unique combination of bulk-like and molecular properties, halfway between small inorganic molecules and larger monolayer-protected metal nanoparticles. Their unique optical properties allow to study their behaviour in solution and on surfaces using optical spectroscopy; though, their application in bioscience, nanophotonics, nanoelectronics and light-harvesting is limited due to their reduced thermal and chemical stability. Stable for months in solution, IBANs can pack forming macroscopic 3D crystals with triclinic structure. By heating or exposure to suitable solvents, we rearranged the packing of such building blocks into 2-dimensional monoatomic layers, stabilized on both sides by a layer of thiols, forming stacked structures with high periodicity across the plane. We combined UV-Vis spectroscopy and light scattering in solution with AFM and X-rays scattering in solid to follow the structural transformation of such materials at the nanoscale. The kinetics and the mechanisms of degradation were studied in-situ by Mass Spectroscopy (MS) and X-ray Photoemission Spectroscopy (XPS) in ultra-high vacuum (p = 10-9 mbar). GISAXS/GIWAXS measurements performed with synchrotron light clearly showed the presence of a crystalline structure with different Van der Waals packings.

Resume : Charge transport through organic resistive memory devices has been an arena of intense research. Here we explore the transport properties of a film made of a Ru-complex displaying memristive response at room temperature, i.e. a pinched hysteresis loop in the current-voltage-characteristics J(V). In-situ Raman and UV-Vis spectroscopic measurements establish that the switching in film conductance is controlled by the ligand redox states of the film molecules, while the counter ions account for the hysteresis. As temperature is lowered, the hysteresis in J(V) gradually decays below 145K till ~5K where it completely quenches. In the temperature range of 135K to 110K, we observe well resolved conductance plateaus at different applied bias with sharp transition in between them. The number of plateaus N in the J(V) follows the empirical rule of N= d[nm]/5 where d is the film thickness in nm. The conductance plateaus correspond to a correlation of [J0]^N, with J0 = current of the first plateau. Each of the plateaus are characterized by in-situ Raman spectroscopy as well as photoluminescence (PL) measurement, both of which exhibit sharp transitions corresponding to the switching observed in J(V). PL and Raman peak intensities scale as N x I0, where I0 is the PL/Raman intensity of the first plateau. These observations indicate a layer by layer electron doping in the film where layers of around 5 nm get doped sequentially. This is an unprecedented result in an amorphous film.

Resume : We report on the sensing of volatile organic compounds including alcohols and aromatic molecules by multi-layered photonic crystals made of commodity polymers such as polystyrene, cellulose acetate, and poly (p-phenilenoxide). The simple kinetical analysis of the optical response of these microstructured nanocomposites to the vapours exposure leads, on one hand, to label-free colorimetric sensors, suitable for the quali-quantitative analysis of volatile organic compounds, and on the other, to the determination of the analyte diffusion parameters into the polymer multilayers. We will also show that this simple optical method provides a new powerful tool for the in-situ assessment of the molecular diffusion coefficient in polymer films, widely used in food packaging and for the encapsulation of optoelectronic devices by mean of simple UV-VIS spectroscopy.

Resume : The preparation of complex nanosized 3D structures requires highly developed and expensive laboratory techniques. As an alternative, natural material is available in large quantities and various structures, with properties that may approximate the artificial ones [1]. It was shown that the biological photonic crystal structures occurring in butterfly wing scales can be used as sensing material [2]. The color of certain butterfly wings is determined by two components: pigments and structural coloration [1]. The photonic nanoarchitectures are built up of chitin and air, and their coloration varies if small changes occur in the refractive index of the medium, for example if mixing vapors in the air. This generates a variation perceptible with optical spectroscopy. Measuring the reflected light spectrum, one can determine the concentration of the vapors in the air. As the gas sensing experiments needs high reproducibility, we tested the stability of the wing coloration in the case of Polyommatus icarus butterflies collected from a certain population [3] and from a large temporal and spatial range. Also it was tested the alteration of the color when heat shock was applied on pupal stage of the butterflies [4]. Our latest results on gas/vapor sensing will also include measurements on functionalized wings. [1] L.P. Biró, J.P. Vigneron, Laser Photon. Rev. 5, (2011) [2] R.A. Potyrailo et al. Nat. Phot. 1, (2007) [3] Piszter et. al. Plos One 11, (2016) [4] Kertész et. al. Sci. Rep. 7, (2017)

Resume : Solution processing of graphite and other layered materials provides low-cost inks enabling printed electronic devices [1]. However, the limited quality of the 2d material inks, the complexity of the layered arrangement, and the lack of a suitable dielectric 2d ink [2] has impeded the fabrication of active field effect devices with fully-printed 2d heterostructures [3]. In this work we demonstrate fully inkjet printed 2d material active heterostructures using graphene and hexagonal-boron nitride (h-BN) inks, and use them to fabricate all inkjet printed flexible and washable field effect transistors (FETs) on textile, reaching a field effect mobility of μ ~ 91 ± 29 cm2 V-1 s-1 on polyester fabric, at low operating voltages (< 5 V). The devices maintained their performance even under ∼ 4% tensile strain and showed stable operation for periods up to 2 years, indicating the two-fold role of the h-BN layer as a flexible dielectric and encapsulant. Our graphene/h-BN FETs are washable up to 20 cycles, which is ideal for textile electronics. The viability of our process for printed and textile electronics is demonstrated by fully inkjet printing electronic circuits, such as reprogrammable volatile memory cells, complementary inverters, and OR logic gates with graphene/h-BN FETs. References [1] Torrisi, F. et al. Inkjet-printed graphene electronics. ACS Nano 6, 2992–3006 (2012). [2] Kelly, A. G. et al. All-printed thin-film transistors from networks of liquid-exfoliated nanosheets. Science, 356, 69–73 (2017). [3] Torrisi, F. & Coleman, J. N. Electrifying inks with 2D materials. Nat. Nanotechnol. 9, 738–739 (2014).

Resume : Recent advances in technological and materials innovations have shifted the architecture of integrated circuits from two-dimensional planar to three dimensional (3D) systems, with stacked chips. The performance demands of these 3D-SIC devices seem to be at odds with the reliability needs because while the emerging devices are expected to operate at higher current densities, they have lower voltage tolerances at higher electric fields. With this change, the reliability of the electronic circuitry has shifted from being transistor-dominated to interconnect-dominated challenges such as resistivity changes; stress induced unexplained early failures; electromigration, etc. The problems are by-and-large materials. Unfortunately, traditional metrology has been unable to adequately address the measurement needed to in-situ characterize the underlying failure mechanism. We have introduced and demonstrated the application of broadband radio frequency dielectric spectroscopy (BDS)-based metrology, in addressing the metrology gap. The BDS leverages the well-known concepts from the interaction of electromagnetic radiation matter, except that microwaves induce molecular rotations instead of vibronic spectroscopy (i.e., UV-Visible-IR spectroscopy) in solid state materials. BDS measurements provide both electrical and chemical information to guide the reliable integration of material into more solid designs for the intended applications, and for monitoring the manufacturing process. These RF-dielectric material interactions are reasonably granular and uniquely suitable for studying the buried structures and material interfaces inherent in integrated circuit devices. In this talk I will review several BDS applications in determining the dominant failure mechanisms in disparate reliability issues of emerging 3D integrated electronic devices.

Resume : This work addresses efficiency improvements of solar cells by manipulating the spectrum of sunlight to better match the range of efficient current generation. The intrinsic transmission losses in crystalline silicon can effectively be reduced using photon upconversion in erbium ions in which low energy photons are converted to higher energy photons able to bridge the band gap energy and contribute the energy generation. The upconversion process in erbium is inefficient under the natural solar irradiation, and without any electric field enhancements of the incident light, the process is negligible for photo-voltaic applications. However, the probability for upconversion can be increased by focusing the incident light onto the erbium ions using optimized metal nanostructures [1, 2, 3]. The aim of this work is to increase the photon upconversion yield by optimizing the design of metalic or dielectric nanostructures placed on top of an erbium doped thin film. To achieve this goal, topology optimization [4] is used to create 2D cross-sectional designs of nanostrips able to focus the incident light into the film. The infrared absorption band of erbium is sought utilized by optimizing for multiple excitation wavelengths while also including production inaccuracies directly within the optimization process [5]. The governing physics is modeled using Maxwell equations in a finite spatial domain truncated using periodic or scattering boundary conditions. [1] S. R. Johannsen et al. ?Up-conversion enhancement in Er3+ doped TiO2 through plasmonic coupling: Ex- periments and finite-element modeling?. In: Appl. Phys. Lett. 106.5 (2015), p. 053101. DOI: 10.1063/1. 4907415. [2] S. P. Madsen et al. ?Optimizing Plasmonically Enhanced Upconversion?. In: Energy Procedia 77 (2015), pp. 478?486. DOI: 10.1016/j.egypro.2015.07.068. [3] H. Lakhotiya et al. ?Plasmonically enhanced upconversion of 1500 nm light via trivalent Er in a TiO2 matrix?. In: Appl. Phys. Lett. 109.26 (2016), p. 263102. DOI: 10.1063/1.4972785. [4] J. S. Jensen et al. ?Topology optimization for nano-photonics?. In: Laser Photonics Rev. 5.2 (2011), pp. 308? 321. DOI: 10.1002/lpor.201000014. [5] J. Vester-Petersen et al. ?Topology Optimized Gold Nanostrips for Enhanced Near-infrared Photon Upconversion?. Submitted, 2017.

Resume : Perovskite nanocrystals (NCs) are receiving great deal of attention due to their unique optoelectronic properties [1]. Among these, high fluorescence quantum yields (QYs), tunable emission colour across visible range, large absorption cross-section, large diffusion lengths, and long recombination times make them potential candidates for photovoltaic and light emitting applications. In this presentation, I will introduce facile methods for shape-controlled synthesis of perovskite NCs ranging from nanocubes, to nanoplatelets, and nanowires [2-4]. The tunable optical properties of perovskite NCs by their dimensions and control over halide ion composition will be discussed. References [1] l. Polavarapu,* B. Nickel, J. Feldmann, A. S. Urban, Adv. Energy Mater. 2017, DOI: 10.1002/aenm.201700267 [2] Y. Tong, F. Ehrat, W. Vanderlinden, C. Cardenas-Daw, J. K. Stolarczyk, L. Polavarapu, * Urban, A. S. ACS Nano 2016, 10, 10936-10944. [3] V. A. Hintermayr, A. F. Richter, F. Ehrat, M. Döblinger, W. Vanderlinden, J. A. Sichert, Y. Tong, L. Polavarapu,* J. Feldmann, A. S. Urban, Adv. Mater. 2016, 28, 9478-9485. [4] Y. Tong, E. Bladt, M. F. Aygüler, A. Manzi, K. Z. Milowska, V. A. Hintermayr, P. Docampo, S. Bals, A. S. Urban, L. Polavarapu,* J. Feldmann, Angew. Chem. Int. Ed. 2016, 55, 13887-13892.

Resume : First-principles calculations have been performed on the structural, electronic and elastic properties of the Pm3m cubic CeCoO3 compound, by means of the Density Functional Theory and the Linearized Augmented Plane Waves (FP-LAPW) method with spin polarization. For the calculations, the exchange and correlation potentials were included through the Generalized Gradient Approximation (GGA) with correlation effect correction (GGA + U). The structural properties, including lattice constant are found to be in close agreement with the reported experimental data, the calculated densities of states presented in this study identify the metallic behavior for both approaches. In addition, the ferro-magnetic phase is found to be energetically more favorable than non-magnetic and anti-ferromagnetic phases Finally ,we have evaluated the elastic constants (Cij), the young’s modulus (Y), poison’s ratio and anisotropic factor (A).

Resume : Rare earth orthovanadates have very important applications in various fields involving chemistry and biology, luminescent nanoparticles and light transformers. These compounds are chemically stable and non-toxic. Their range of biological applications includes fluorescent probes for single molecule tracking, drug development, protein detection and fluorescent bio labeling. It is expected that intensities of their luminescent emission can be effectively increased with the A2+ modifying cations. The investigated nanoparticles were prepared by aqueous nitrate-citrate sol-gel synthesis route using citric acid as a complexing agent. XRD study have shown that synthesized samples have monoclinic or tetragonal zircon structure as well as their mixture dependently on Eu and Ca concentrations. Characterization of the samples morphology made using scanning electron microscope Tescan Mira 3 LMU with 1 nm electronic beam diameter have shown that each sample consist of nanoparticles of the same diameters, but these diameters are varied from 20 nm to 100 nm for different samples. The Ca-undoped samples are characterized by the largest 100 nm diameters of nanoparticles. Luminescence properties also depend on concentrations and excitation wave length as well. Two types of Eu3+ centers were found by emission spectra. Structures of these centers are discussed taking into account crystal structure, possible Ca-induced defects and surface effects.

Resume : The efficiency of modern photovoltaic units are approaching the SQ-limit, that is, the maximum obtainable efficiency. Thus, new methods are in demand, to increase this limit in the process towards a renewable energy-system. Upconversion, the process of combining several low energy photons to one photon of higher, is a promising way achieving this goal. Trivalent rare-earth ions, and especially erbium ions, have proven to be a promising candidate for upconversion. We investigate erbium based upconversion form coatings produced by magnetrun sputtering. The coating consists of erbium doped TiO2 placed on a substrate of fused quartz. The aim of this work is to construct a model for the upconversion dynamics based on rate equations. As far as possible, the parameters of the model is experimentally determined. The main parameters of the model are the absorption cross-section of the erbium ions, and the different transition rates governing population decay and increase. The absorption cross-section is determined through absorption spectra using a spectrophotometer and by measurements of the complex index-of-refraction obtained with an ellipsometer. From the ground-state-absorption cross-section combined with the theories of McCumber, and Judd & Ofelt it is possible to compute the exited-state cross-sections as well. The transition rates will be determined through the exited-state lifetime of the erbium ions, measured from time-resolved-luminescence experiments. Besides enabling investigation of the upconversion dynamics the model paves the way for a direct investigation of transition rates such as multi-phonon relaxation and Förster-resonance energy-transfer.

Resume : Transparent electrodes are used in a variety of optoelectrical devices including solar cells, flat panel displays, touch screens and transparent heaters. Indium tin oxide is the most commonly used transparent electrode material, however, the need for material cost reduction, mechanical flexibility and low cost/temperature fabrication techniques have recently oriented research toward alternative materials. Among them, random networks of solution-synthesized silver nanowires present optical and electrical properties approaching those of ITO, while being much more flexible and inexpensive. As with all transparent electrode materials, the conductivity should be maximized for a given transparency. In this work, the strategy to achieve this is to employ two novel silver nanostructures: ultra-long nanowires and branched nanowires. Both these nanostructures reduce the number of high resistance junctions in the nanowire network and thus lower the overall sheet resistance of the electrode. We will show how these nanostructures can be produced in colloidal suspension, how they grow and what impact they have on the electrode properties.

Resume : Molybdenum-cluster-halide complex, expressed by [Mo6X8Z6] (X, Z=halogen), is regarded as a building block for construction of nanostructures hybridizing inorganic complex and organic molecules. Hybridization of organic and inorganic components is a new trends in materials science, as perovskite-type lead halide based compounds including organic molecular ion in their crystal lattice is regarded as a promising new functional material for photovoltaic applications. In this study, we have devoted ourselves to investigate functions of the [Mo6X8Z6]-complex on exploration study aiming to find new functionality in nanostructured materials. In particular, we have investigated the effect of ion exchange for halogens represented by X and Y in [Mo6X8Z6] from both chemical experiments and DFT simulations. As a result, we found that such ion exchange achieves drastic modification of the optical properties of the [Mo6X8Z6]-based complex compounds.

Resume : The dynamic underwater chemistry seen in nature is inspiring for the next generation of sustainable chemistry. This talk discusses the Leidenfrost dynamic chemistry occurring in an underwater overheated confined zone as a new tool for customized creation of nanoclusters of zinc peroxide. Also, the cytotoxicity of such nanoclusters on cancer cells is demonstrated. The Leidenfrost driven swimming enables physical separation between the nucleation and growth events, hence governs a new synthetic route to formation of monodisperse and size tailored nanoparticles whose size is proportional to the concentration of reagents in the solution. Peroxides act as a supplier of oxygen, hence have therapeutic uses against complex diseases, including cancer.

Resume : Label free and real time optical transduction, in particular by Surface Plasmon Resonance (SPR), is undoubtedly at the forefront of affinity-based biosensing (1) thanks to its sensitivity, specificity, versatility, miniaturization perspectives, reusability, and low cost. Despite its application to a broad area of interests, from environment to food analysis, from drug discovery to diagnostics, their exploitation in cultural heritage conservation is still unexplored. First a biosensor containing as specific biomarkers, ovalbumin (OVA) and immunoglobulin Y (IgY) has been set up for egg white and yolk recognition, respectively. This analytical method is here coupled for the first time to some innovative Water-based Highly Viscous Polymeric Dispersions (HVPD) composed by polyvinyl acetate (PVA), borax, and water, recently developed and successfully exploited for the selective removal of protein materials from painted surfaces of historical and artistic interest (2). This SPR biosensor allows the simultaneous recognition of albumen and/or yolk in HVPD extracts. Moreover, other SPR-based approaches based on LSPR phenomenon specifically tailored for the selective recognition of OVA and based on Au nanoparticles (AuNPs) embedded in a polydopanmine matrix have been prepared and tested. Finally, a combined 'clean & check' approach was optimized, consisting in the HVPD application on simulated and real art samples followed by the evaluation of the presence in the extract of egg components. The method is mini-invasive and fast, allowing also the further identification of other protein matrices possibly present in the HVPD extract (3,4). [1] M.L. Ermini, S. Mariani, S. Scarano, M. Minunni, Biosensors and Bioelectronics 61 (2014) 28-37. [2] I. Natali, E. Carretti, L. Angelova, P. Baglioni, R.G. Weiss, L. Dei, Langmuir 27 (2011) 13226?13235. [3] S. Scarano, E. Carretti, L. Dei, P. Baglioni, M. Minunni, Biosensors and Bioelectronics 85 (2016) 83-89. [4] S. Scarano, C. Berlangieri, E. Carretti, L. Dei, M. Minunni, Microchimica Acta, in press

Resume : Self-assembled diphenylalanine (FF) peptide nanotubes (PNTs) have attracted significant attention due to their well-ordered supramolecular structure and wide range of functional capabilities that may enable potential nanobiotechnology applications. However, self-assembled PNTs are generally inhomogenous at the macroscale, which has limited their potential use. Reproducibly controlling the assembly and alignment of PNTs is therefore critical to enable the widespread use of PNTs, e.g., in sensing applications. In this study, a surface patterning technique based on UV/ozone exposure through a shadow mask is used to align PNTs (Fig. 1a). Exposed regions become hydrophilic, leading to directed spreading of the FF solution and alignment of the PNTs that improves as the difference in wettability between adjacent regions increases. Alignment was further found to depend on the concentration- and temperature-dependent diameter of the PNTs formed and the size of the hydrophilic area. Having optimized the alignment of the PNTs (Fig.1b), they are coated with silver nanoparticles and the device is used to sense an analyte molecule using surface enhanced Raman spectroscopy (example shown in Fig. 1c) sensing the presence of a porphyrin TMPyP analyte at concentrations down to 10-14 mol, which indicates single molecule detection (shown in Fig. 1d). Bio-template based on PNTs+Ag NPs nanocomposites is found to be reactive under UV lamp illumination, since PNTs have large band gaps ~4.9 ev, charge transfer can occur when stimulating by visible light. Herein, we also show significant increase in Raman signal using three different probe molecule TMPyP, RB, and 4ABT when the bio-template exposure to UV light for approximately 35 to 40 minutes. The increase in Raman intensity and the fluctuation observed in this study can be due to charge transfer mechanism between the nanotubes and the nanoparticles.

Resume : The interplay of size confinement effects and physical characteristics (positions of maxima in the spectrum of longitudinal acoustic vibration modes, the density of electronic states at the Fermi level) in gold nano-objects may enable special tuning of absorption / emission characteristics in different wavelength ranges, depending on the nano-objects’ shape. Earlier we outlined a design for THz generation in gold nano-objects via phonon-assisted absorption of microwaves (mw) [1]. Our present calculations support a setup for the generation of soft terahertz radiation ([nu] ≈ 0.1–0.5 THz), again by metallic nano-objects exposed to mw; however, in difference from the earlier outlined scheme, the present mechanism anticipates an involvement of two longitudinal acoustic phonons with opposite wavevector directions, whose energy difference would equal h[nu]. The excited Fermi electron then relaxes releasing a THz photon at frequency [nu]. The selectivity in the phonon absorption can be enhanced by tuning the shape of nano-object; in particular, the cases of gold nanobars, nanorings, and nano-cubooctahedra are analysed. The specificty of the suggested THz source would be its broad aperture, that may enable its use e.g. in security control. Otherwise a low-frequency THz source could find its use in biomedical screening, due to known contrast of cancer cells to sane bio tissue in the THz range. [1] K. Moldosanov and A. Postnikov, Beilstein J. of Nanotechnology 7, 983 (2016); DOI:10.3762/bjnano.7.90

Resume : We have developed various platforms for detection of the date-rape drug, ketamine, in beverages like whiskey, rum and pepsi. The present work shows the comparison of the electrochemical sensing and colorimetric detection of ketamine. Firstly, platinum-palladium (Pt-Pd) nanoalloys were used as the sensing platform on fluorine doped tin oxide (FTO) electrode for electrochemical sensing of ketmine. This was done on a 3-electrode system with Ag/AgCl as the reference electrode, platinum wire as the counter electrode and Pt-Pd/FTO as the working electrode. Secondly, Graphene Oxide-Zeolite (GO-Zeo) nanocomposites were synthesized and used for sensing of ketamine on electrochemical microfluidic paper based analytical device (EµPAD). The use of paper based device makes the work highly economic in comparison to the expensive metal electrodes. This paper based device was used as a two electrode system for electrochemical sensing of ketamine. Finally, the cost of the detection was further reduced by preparing a naked eye colorimetric sensor for detection of ketamine. The change in color of the paper strip upon addition of the analyte is the basis of sensing. The developed paper strip was linked with a smart phone app which automatically detects the color change and sends message to the selected numbers when drink is not safe, if needed.

Resume : Localized and recurring delivery of drugs in the hour of need is of great importance in many clinical conditions such as in the treatment of solid tumors, post surgical wounds and localized infections. This helps increase the drug efficacy and minimize the side effects of anesthetics. Lanthanide-doped upconverting nanoparticles (UCNPs) have emerged as excellent nanotransducers for converting longer wavelength near-infrared (NIR) light to shorter wavelengths spanning the ultraviolet (UV) to the visible (Vis) regions of the spectrum via a multiphoton absorption process, known as upconversion. We have developed a new phototriggered drug delivery system consisting of LiYF4:Yb3 /Tm3 @SiO2 NIR to UV–Vis–NIR UCNPs individually coated with a 10 ± 2 nm layer of chitosan (CH) hydrogel cross-linked with a photocleavable cross-linker (PhL). We encapsulated fluorescent-bovine serum albumin (FITC-BSA) inside the gel. Under 980 nm excitation, the upconverted UV emission cleaves the PhL cross-links and instantaneously liberates the FITC-BSA under 2 cm thick tissue. The release is immediately arrested if the excitation source is switched off. The upconverted NIR light allows for the tracking of particles under the tissue. Nucleus pulposus (NP) cells cultured with UCNPs are viable both in the presence and in the absence of laser irradiation. Controlled drug delivery of large biomolecules and deep tissue imaging make this system an excellent theranostic platform for tissue engineering, biomapping, and cellular imaging applications.

Resume : The flame based approach offers unique opportunities for metal oxide nanostructuring, ranging from Q1D nanowires to large 3D interconnected networks.[1] This strategy offers direct integration of ZnO structures and their networks on the desired substrates for various applications, e.g., whispering gallery modes, photocatalysis or nanosensing (UV/gases) applications.[1-4] The flame grown ZnO tetrapods and nano- and microstructures exhibit very low cytotoxicity and have shown strong potentials against antiviral applications.[5] The unique 3D shape of the ZnO tetrapods facilitates them to be used as efficient fillers for advanced composites, e.g., self-reporting composites[6] and many others. The 3D porous, flexible and conducting network from ceramic materials are now-a-days very important because of their technological relevance and the developed flame method offers desired synthesis of various ZnO and SnO2 networks.[1] These 3D porous networks can be decorated with other nanostructures for designing hybrid multifunctional materials[7] and can also be used as sacrificial templates to grow new nanomaterials and composites.[8] Refs: [1]Part. Part. Syst. Charact. 30, 2013, 775-783; [2] ACS Appl. Mater. Interfaces 6, 2014, 7806−7815; [3] ACS Appl. Mater. Interfaces 7, 2015, 14303–14316; [4]Adv. Mater. 26, 2014, 1541-1550; [5]J. Immunol. 196, 2016, 4566-4575; [6] Adv. Mater. 26, 2014, 1342-1347; [7] Adv. Funct. 27, 2017, 1604676; [8]Adv. Mater. 24, 2012, 3486-3490.

Resume : Solid state nanopores have recently attracted a large interest for detection of single molecules and as a possible method for DNA sequencing. The nanopores of a few nanometer dimensions are usually fabricated in a nitride membrane using electron beam drilling. The translocation of DNA strands (or proteins) is then detected by the blockade of the nanopore resulting in a drop of the ionic current between the two reservoirs on opposing sides of the membrane. This technology is, however, difficult to scale up and as an alternative, optical techniques can be used in combination with arrays of nanopores for massive, parallel readout. This requires labelling of biomolecules or nucleotides, by fluorophores which can readily be read out by a CCD or CMOS camera. We have developed a technique for fabricating arrays of nanopores in a silicon membrane reaching diameters down to ~10 nm. The fabrication scheme involves optical lithography and ICP etching from the backside of an SOI wafer to etch out membranes of a few hundreds micrometer diameter. The silicon device layer at the front is then patterned using e-beam or optical lithography followed by anisotropic KOH etching to form inverted pyramids which serve as etch pits to initiate pore formation in a subsequent electrochemical etching step. In this presentation, I will review the fabrication techniques to achieve nanopore arrays and our initial DNA translocation experiments through the nanopore arrays using fluorophore labelled DNA strands. It will also be demonstrated that the DNA translocation is affected by a thermophoretic effect caused by heating from the excitation laser beam spot.

Resume : The conventional CMOS image sensor based on silicon photodetectors has been the efficient route for the fabrication of high performance mobile phone cameras, but this technology now suffers from resolution limitation due to the broad absorption spectrum of Si in the visible region and its low coefficient of absorption. The use of organic materials led to a reduction of the optical and electrical crosstalks, and also to the possible reduction of spectral crosstalk by modifying the molecular structure for better absorption at specific wavelengths.[1] Among acceptors, fullerene derivatives has been the preferred material due to its high electron mobility and its good miscibility. However, the broad absorption spectrum of C60 with a peak intensity in the blue region is a drawback for the performance of green-sensitive organic photodetector (OPD).[2] Therefore, the development of a nonfullerene semiconducting material with specific color absorption and high carrier mobility is required to improve the OPDs for application as CMOS image sensors. In this study, a new n-type small molecule with green-selective absorption was designed using by molecular structure calculation using Gaussian 09 and synthesized, which is comprising of an indacenodithiophene as the fused backbone and two dicyanovinylene at both extremities. As the promising candidate of acceptor material, this material can be adopted for the green-sensitive OPD in CMOS image sensor with high spectral sensitivity. As the promising candidate of acceptor material, this material can be adopted for the green-sensitive OPD in CMOS image sensor with high spectral sensitivity.

Resume : Electronic properties of inorganic compound semiconductors, such as oxides and nitrides, are largely governed by the fixed native defect chemistry of a respective system. Organic molecules, on the other hand, provide a much simpler means to systematically alter energy level alignment at the interface. To study the effect of such modifications, bare polycrystalline Au(111) surfaces were functionalized with phenothiazine based SAMs. Phenothiazines are a class of redox-active, fluorescent molecules, exhibiting p-type semiconducting character. Due to its ability to form dense and well-ordered monolayers as well as its large π-electron system, energy levels should couple with bands of metals/semiconductors. X-ray photoelectron and photoemission yield spectroscopy (XPS and PYS, respectively) have been used to measure the alignment of the frontier orbitals, which correspond to valence and conduction band, with respect to the Fermi level of the system, and the vacuum level of the metal and in the SAMs. The electronic structure was then correlated to the electrochemical properties of the system around the open circuit potential in an acidic, a neutral and an alkaline electrolyte. Electrochemical measurements were performed by linear sweep voltammetry (LSV). As a result, a correlation matrix was obtained, showing the effect of interfacial electronic structure, via the alignment of the frontier orbitals and the work function, on steady state electrochemical quantities.

Resume : Resistive memory devices can be broadly defined as electrical switches that retain a state of internal resistance based on the history of applied voltage. Such devices hold several performance characteristics that can potentially exceed conventional integrated circuit technology and are projected to be the building blocks of the next generation of computing architectures such as neuromorphic computing. While some oxide resistive memory devices are well characterized and slated for commercial applications, other genres, especially organic resistive memories are quite far off from the benchmarks. The challenges include insufficient consistency, endurance, retention, switching speed and a lack of understanding of the operating device mechanisms. In this report, we demonstrate a resistive memory device with a spin-coated active layer of transition metal complex sandwiched between two metal electrodes with reproducibility over 300 devices. We overcome the large read-write voltage and speed limitations of such devices by using nanoparticles on the bottom electrode. This brings the switching voltage down to 500mV and reduces the device resistance by almost 4 orders enabling switching in 30ns. With 100ns pulses we observe endurance of more than 10^11 cycles without degradation along with a stability of more than 10^6s. Insight into the molecular switching mechanism of the device is obtained via in situ Raman-spectroscopy in conjunction with UV-Vis spectroscopy and spectroelectrochemistry (supported by Density Functional Theory (DFT)). These allow the determination of the molecular electronic states at each conductance level and substantiate that the redox state of the ligands determines the switching states of the device. Both in terms of device performance and understanding this study presents a significant leap in organic resistive memory technology.

Resume : Production and sale of fraudulent goods have become a global epidemic, posing major threats to individual consumers and causing enormous financial damages. Considerable efforts have been devoted to designing anti-counterfeiting measures, leading to many different anti-counterfeiting technologies on the current market. However, traditional methods such as barcoding and water marking are not very effective, because these techniques are outdated and easy to be duplicated. We describe a novel strategy for creating anti-counterfeiting patterns by taking advantage of highly tunable lanthanide luminescence. Instead of using multicolor taggants that are responsive to a single-wavelength excitation, we use luminescent nanotaggants that are encrypted to be excited with distinct wavelengths. Decryption is achieved by examining the temporal color response of the pattern to different illuminations. A genuine pattern is guaranteed only if the desired luminescent color sequence is achieved. By spatial partition of different nanotaggants via a serial contact printing process, we further demonstrate that spatially encoded graphics can also be encrypted as anti-counterfeiting patterns. We believe that the encryption technique described here can substantially increase the difficulty of duplication and thus to provide extra high-level security protection in many business applications.

Resume : In this study, the rheological behavior of Cu nano-inks with various wt% of polymer binder was investigated during the flash light sintering process. The rheological behavior of Cu nano-inks was measured using a rheometer system to analyze the influence of rheological factor such as viscosity and thixotropic index. Fabricated Cu nano-inks were printed on polyimide substrate using a screen printing method. Also, the effect of screen printing speed to printability was investigated. To sinter the printed Cu nano-inks, flash light irradiation system was employed. The flash light irradiation conditions (pulse power, pulse number, on-time, and off-time) were optimized to obtain the high sintering characterization of Cu nano-inks. In order to characterize the microstructures and transformation crystal phase of the sintered Cu nano-inks, scanning electron microscopy (SEM) and x-ray diffraction (XRD) were performed. The resistivity of sintered Cu nano-inks was calculated using the four-point probe method and alpha step. From the results, the optimal printed and sintered Cu nano-inks had a 7.56 μΩcm resistivity and 5B level of adhesion strength without substrate warpage. Acknowledgments This work was supported by a National Research Foundation of Korea (NRF), funded by the Ministry of Education (2015R1D1A1A09058418).

Resume : Strongly correlated electronic systems such as Transition Metal Oxides often possess various mid-gap states originating from intrinsic defects in these materials. In this work, we investigate an extremely sharp and strong Photoluminescence (PL) transition originating from such defect states in two widely used perovskites, LaAlO3 and SrTiO3, in the NIR energy range. A detailed study of the PL as a function of temperature and magnetic field has been conducted to understand the behavior and origin of the transition involved. The temperature dependence of the PL peak position for SrTiO3 is observed to be opposite to that in LaAlO3. Our results reveal the presence of a spin/orbital character in these transitions which is evident from the splitting of these defect energy levels under a high magnetic field. These PL transitions have the potential for enabling non-contact thermal and field sensors, and advanced photonic devices for lasing applications. Ref: Sarkar, S. et al. Sci. Rep. 6, 33145; doi: 10.1038/srep33145 (2016)

Resume : While conventional spherical colloidal nanocrystals have shown promise in these fields due to their ease of fabrication, processibility and salient optical properties, it may be envisaged that more applications may emerge if nanocrystals can be synthesized in shapes of higher complexity and therefore increased functionality. Here we will presents a systematic, surfactant-driven hot injection method to synthesize CdSe seeded CdS nanoheterostructures with very high yield. This was extended to other systems such as CdSe/CdTe and CdTe/CdS or PbSe/PbS and Ag2Se/Ag2S via cation exchange techniques. In order to elucidate the reactivity of the facets at the tips of such branched structures as a function of the shape of the arms, we exposed the structures of various arm dimensions to controlled amounts of metal precursors and discovered conditions in which the metal nanoparticle can be deposited precisely at the tip of one of four arms with symmetric reactivity. Afterward, we utilize these particles to overcome some of the key problems in the assembly of anisotropic shaped nanoparticles. In next, we will showcase the utility of such branched heterostructures in applications such as light-emitting diodes and solar cells. CdSe/CdTe tetrapods immobilized on oleylamine-functionalized reduced graphene oxide (rGO) sheets can be homogeneously mixed with an organic dye (PCDTBT) to form donor?acceptor dispersed heterojunctions and exhibit a high power conversion efficiency of ? 3.3% in solar cell devices. At the end we will discuss a single active layer quantum dot light-emitting diode device based on colloidal CdSe (core)/CdS (arm) tetrapod nanostructures capable of simultaneously producing room temperature electroluminesence (EL) peaks at two spectrally distinct wavelengths, namely, at?500 and?660 nm.

Resume : As has been the case for past years, the key challenge in the commercialization of dye-sensitized solar cells (DSSCs) is the poor charge transfer and high recombination rate in device architecture [1,2]. Herein, a novel approach based on high-yield DNA molecules in different structure (eukaryotic / prokaryotic) and shape (circular / linear) has been proposed as not only linker bridging unit in the photosensitization process but also thin tunneling barrier at TiO2/dye/electrolyte interfaces. As compared to bare TiO2, this modification provides a large steric hindrance which plays a role in blocking recombination by preventing the access of electrons to the redox electrolyte as well as facilitates an efficient electron harvesting by introducing alternative anchoring facilities and/or serving as a photon cage. By immobilizing linear shaped genomic DNA molecules in eukaryotic structure, the efficiency has been dramatically enhanced to 8.74% by improving the Voc from 688 to 709 mV, with synergistical Jsc enhancement from 14.51 to 17.88 mA.cm?2. Furthermore, time-resolved fluorescence spectroscopy reveals improved an electron transfer rate whereas electrochemical analysis indicates a reduced charge transport resistance (Rct = 17.29 to 4.08 ?). Finally, we could also demonstrate good stability of the devices under prolonged irradiation. These findings suggest that bio-functionalization by engineering of the photoelectrode can be a novel guideline toward facile passivating mechanisms and high e?ciencies. References [1] Ates Sonmezoglu O., Akin S., Terzi B., Mutlu S., Sonmezoglu S., Adv. Funct. Mater., 2016, 26, 8776?8783. [2] Akin S., Gulen M., Sayin S., Azak H., Yildiz H. B., Sonmezoglu S., J. Power Sources, 2016, 307, 796?805.

Resume : In the current work, for the first time, Cu2XSnS4 (X = Co and Fe) thin films have been directly electrodeposited on the substrates following with sulfurization process at 5000C for 45 min and these thin films were employed as counter electrodes (CEs) in dye sensitized solar cell (DSSC). The physical and electrochemical properties of the thin films were investigated by pertinent measurements. The obtained results exhibited that the kesterite structures with Co and Fe have been successfully built up with the proposed method. Moreover, the introduction of Co into kesterite structure enhances the crystallite structures, narrows crystallite size and enlarges the surface area of the film in comparison with that of Fe due to smaller ionic radius of Co2+. Furthermore, the Cu2CoSnS4 CE demonstrated a higher electrocatalytic activity than that of Cu2FeSnS4, offering a higher efficiency (ɳ) of 5.55%, prolonged electron lifetime, better multiple start/stop capability with no decrement in Jsc after 10 cycles and a higher Jsc stability under sustained irradiation compare to Cu2FeSnS4 based cell (ɳ = 5.14%). These can be ascribed to larger surface area of Cu2CoSnS4 which improves diffusion ability and interaction of electrolyte with CE, higher conductivity and stronger adherence of Cu2CoSnS4 on the substrate which results in lower serial and charge transfer resistances at the interfaces of CE/electrolyte and CE/substrate. Therefore, these CZTS derivatives can be offered as alternatives to high-cost platinum for robust and low-cost DSSC applications due to their excellent catalytic activities, highly stabilities, and simple fabrication processes and low-costs. Acknowledgement–This study was supported by the European Union through the COST Action MP1407 “Electrochemical processing methodologies and corrosion protection for device and systems miniaturization (e-MINDS)”, and by the Scientific and Technological Research Council of Turkey (TUBITAK Grant Number 115M762) who provided financial support for this research.

Resume : Transparent conductive films are widely used in common optoelectronics devices like organics photovoltaics, displays and transparent heaters. The fabrication of transparent conductive films is currently realized with thin films of transparent conductive oxides, and in particular indium tin oxide (ITO). The as-made ITO transparent conductors lead the market with outstanding optoelectronics performances (R/sq >50 ohm/sq and T >90%) but suffer from limitations like costly fabrication process and brittleness under mechanical stresses. The existing market is evolving towards new types of devices, low cost, high-performance and flexible. Candidate replacement materials for ITO include carbon nanotube networks (CNT), graphene thin films, conductive polymers, metallic grids and metal nanowire networks. Metal nanowires appear the most promising alternative. In particular, silver nanowire networks offer flexible transparent electrodes with similar performances to ITO and less fabrication cost, above all a simple and controlled way of synthesis. Thanks to polyol process, we developed synthesis method able to cover a large spectrum of length/diameter combination. That exploit have been performed by means of varying length and diameter in independent way. This, lead to cover a wide range of applications that require specific optoelectronics properties. We will present our synthesis method for several nanowire morphologies and associated optoelectronic performances. Possible integration according to each morphology/performances will be also discussed.

Resume : In this work, the change of silver nanowire during the combined flash light welding process with UV and NIR light was investigated. The coated silver nanowire on a PET substrate using bar-coater were welded at room temperature, and under ambient conditions by combined flash light irradiation. To monitor the changing silver nanowire for the combined flash light welding process, in-situ monitoring system with electrical circuit using Wheatstone bridge was devised and the sheet resistance changes of silver nanowire during the welding process were recorded using oscilloscope under various flash light conditions (e.g. light energy, on- and off-time duration, and pulse numbers) with UV and NIR irradiation. The microstructure of the welded silver nanowire film and the interface between the silver nanowire film and PET substrate were observed using a scanning electron microscope. Using the devised in-situ monitoring system, the combined flash light welding mechanism of silver nanowire was studied (e.g. the evaporation of organic binder around silver nanowire, the welding form of silver nanowires, etc.). The optimized flash light welding process produces a silver nanowire film with a lower sheet resistance (45.2 ohm/sq) and high transparency (93.46 %) without damaging the PET substrate. Acknowledgments This work was supported by a National Research Foundation of Korea (NRF), funded by the Ministry of Education (2015R1D1A1A09058418)

Resume : The nanostructures are of great interest in context with the materials for energy due to their unique electronic and optical properties. The role of nanostructures in various types of materials of energy, e.g., thermoelectric materials [1-3], fuel cell [4,5] having nanometric size pores, materials for photo splitting of water [6,7], photo catalytic action [8] and thermal storage [9], have attracted attention of researchers. Ion irradiation due to their unique property of depositing large energy density in localized region [10] has been exploited in creating nanostructures and engineering the materials for energy. Some of our ongoing research in area of materials for energy in collaboration with other institutions is briefed here. References 1. J.F. Lee et al., NPG Asia Materials (2010) 2, 152–158. 2. M. Bala, C. Pannu, S. Gupta, T.S. Tripathi, S.K. Tripathi, K. Asokan, D.K. Avasthi, Phys. Chem. Chem. Phys. 17(2015)24427, 3. M. Bala, S. Gupta, S. Tripathi, S. Verma, S.K. Tripathi, K. Asokan, D.K. Avasthi, RSC Advances 5 (2015) 25887. 4. C.Wang et al., Nano Letters 4(2004)345, 5. K. K. Jana, A. Srivastava, Om Prakash, D.K. Avasthi, D. Rana, V.K. Shahi, P. Maiti, Jl. Of Power Sources 301(2016)338. 6. S. Hoang et al., J. Am. Chem. Soc. 2012, 134, 3659−3662, 7. Anuradha Verma, Anupam Srivastav, Anamika Banerjee, Dipika Sharma, Shailja Sharma, Udai Bhan Singh, Vibha Rani Satsangi, Rohit Shrivastav, Devesh Kumar Avasthi, Sahab Dass, Journal of Power Sources 315(2016)152-160. 8. Z. Jiang et al., J. Mater. Chem. A 2 (2014) 19861. 9. Avasthi, S., et al., Tailoring the Thermal Conductivity of Paraffin Wax by Nano -fillers for Thermal Storage Applications, IHMTC, (2017). 10. D. K. Avasthi and G. K. Mehta, ‘Swift heavy ions in materials engineering and nanostructuring’, Springer 2011.

Resume : Metal oxides are potential candidates for energy storage devices like supercapacitors and rechargeable batteries because of their several advantages such as natural abundance and lower price. This research work is focused on the fabrication of 2-D metal oxide nanostructured materials, which can have superior electrochemical performance to the bulk materials. The several chemical methods are being used to synthesize metal oxide nanostructures which involve toxic reagents, solvents and introduction of byproducts. However, physical vapour deposition (PVD) methods provide an eco-friendly route to fabricate 2-D metal oxide nanostructures with clean surface morphology. In this report, the fabrication of binder free supercapacitor electrode of MnO2 nanosheet on Nickel (Ni) coated porous anodic aluminum oxide (AAO) substrate by DC magnetron sputtering, is presented for first time. Ni-coated porous AAO substrate acts as an excellent current collector, which enhances the specific capacitance of MnO2 to 649 F/g. The binder free symmetric supercapacitor device delivered a high areal capacitance (112.6 mF/cm2), specific capacitance (194.23 F/g), good cyclic ability (89.83% retention in capacitance after 5000 cycles), energy density (4.2 Wh/kg), and power density (1.4 kW/kg).

Resume : There is a growing interest for flexible, efficient and low cost transparent electrodes and thus for many applications, including several related to energy technologies (photovoltaics, lighting, electro-chromism?) or displays (touch screens, transparent heaters?). When metallic nanowires are deposited to form random percolating networks, the latter can act efficiently as transparent electrodes. Such networks exhibit very good electro-optical properties and appear as an alternative to the reference material, i.e., indium tin oxide (ITO). The latter exhibits good physical properties and is used for many applications, however, the scarcity of indium, the associated high cost and lack of flexibility of ITO have prompted the search for alternative materials. The emerging transparent electrodes based on silver nanowire (AgNW) networks, exhibit excellent optical and electrical properties [1,2] fulfilling the requirements for many applications [3,4] including flexible devices. In addition, the fabrication of these electrodes involves low-temperature processing steps and upscaling methods, thus making them very appropriate for future use as TE for flexible devices. The aim of the contribution is two-folds. From an experimental aspect, the main physical properties of AgNW networks will be presented, including the influence of post treatments [5] or the network density and nanowire size [6,7]. The network stability will be discussed [8]. We will show that atmospheric pressure spatial atomic layer deposition (AP-SALD) technique can drastically enhance the stability of AgNW networks thanks to a very conformal coating [9,10]. From a numerical approach, Monte Carlo modelling are developed to gain a deeper insight into the physical properties of AgNW networks. The main goals are : i/ studying different MNW geometrical associations, obtained by connecting adjacent AgNW forming nanostructured objects, and calculating their respective critical density to reach percolation. The question is can we lower the critical amount of material to reach percolative networks which would lead to less material consumption and higher optical transparency? ii/ The second part of the numerical work concerns the assessment of AgNW based electrodes integrated into solar cells by calculating the photo-generated carrier?s collection efficiency which is an important parameter for an efficient integration. 1. D.P. Langley, G. Giusti, C. Mayousse, C. Celle, D. Bellet and J.-P. Simonato, Nanotechnology 24, 452001 (2013). 2. T. Sannicolo, M. Lagrange, A. Cabos, C. Celle, J.-P. Simonato and D. Bellet, Small 12, 6052 (2016). 3. S. Sorel, D. Bellet, J.N. Coleman, ACS Nano 8, 4805 (2014). 4. D.P. Langley, G. Giusti, M. Lagrange, R. Collins, C. Jiménez, Y. Bréchet and D. Bellet, Solar Energy Mat. & Solar Cells 125, 318 (2014). 5. D.P. Langley, M. Lagrange, G. Giusti, C. Jiménez, Y. Bréchet, N.D. Nguyen and D. Bellet, Nanoscale 6 13535 (2014). 6. M. Lagrange, D.P. Langley, G. Giusti, C. Jiménez, Y. Bréchet and D. Bellet, Nanoscale 7, 17410 (2015). 7. T. Sannicolo, D. Muñoz-Rojas, N.D. Nguyen, S. Moreau, C. Celle, J.-P. Simonato, Y. Bréchet and D. Bellet, Nano. Lett. 16, 7046 (2016). 8. M. Lagrange, T. Sannicolo, D. Muñoz-Rojas, B. Guillo Lohan, A. Khan, M. Anikin, C. Jiménez, F. Bruckert, Y. Bréchet and D. Bellet, Nanotechnology 28, 055709 (2017) 9. D. Muñoz-Rojas and J.L. MacManus-Driscoll, Materials Horizons 1, 314 (2014). 10. D. Bellet, M. Lagrange, T. Sannicolo, S. Aghazadehchors, V. H. Nguyen, D. Langley, D. Muñoz-Rojas, C. Jiménez, Y. Bréchet, N.D. Nguyen, Materials in press.

Resume : As an alternative to Cu2ZnSnS4 (CZTS); Cu2XSnS4 (X = Mn2+, Ni2+) thin films were successfully synthesized by two-step electrodeposition method and employed as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) for the first time. Besides, the influence of deposition time and annealing process on the structural, morphological, and electrical properties of these thin films were investigated in detail. Experimental results confirmed that Cu2XSnS4 thin films show good crystallinity with preferential orientation along the (112) direction with a rough nanoscale surface. Furthermore, cyclic voltammogram (CV) analyses revealed that CNTS CE possesses the highest electrocatalytic activity, whereas CMTS has the lowest one. As a result, DSSC fabricated with the CNTS, CZTS, and CMTS CEs yielded a power conversion efficiency (PCE) of 4.44%, 3.71%, and 2.87%, respectively. This trend can be greatly attributed to the lower ionic radius of Ni2+ (0.72 Å) than that of Mn2+ (0.80 Å) and Zn2+ (0.74 Å), since larger ionic radius disturbs the crystallinity and obstacles the electron flow. The improved interaction between CE and redox electrolyte as a result of enhanced surface area in CNTS nanostructure can be an additional reason of higher PCE. Moreover, CNTS CE based cell exhibited a superior photocurrent transient (on/off capability) as well as obtained efficiency maintained the output performance even under 3600 s of light soaking (>95% of the initial Jsc remained). The easy synthesis, low-cost and excellent electrocatalytic property may help the CXTS thin films stand out as an alternative CE material in DSSCs. Acknowledgement–This study was supported by the European Union through the COST Action MP1407 “Electrochemical processing methodologies and corrosion protection for device and systems miniaturization (e-MINDS)”, and by the Scientific and Technological Research Council of Turkey (TUBITAK Grant Number 115M762) who provided financial support for this research.