Nano-engineering of materials and interfaces: design, synthesis and applications

Resume : Multifunctional core-shell type hybrid nanoparticles such as those made of superparamagnetic iron oxide nanoparticles (SPIONs) coated with either silica, lipids or peptides are emerging as new class of nanomaterials for drug delivery and hyperthermia cancer therapy. Coating SPIONs with biocompatible materials and controlling their physico-chemical properties reduces the agglomeration of ultra-fine sized particles, thereby increasing their dispersibility and stability, while keeping their superparamagnetic properties intact. Coating also enhances the drug loading efficiency of the nanoparticles. The multifunctional nanoparticles can be targeted specifically to the cancer cell by applying external magnetic field which can then release the drug to the tumour cell by inducing local hyperthermia. Herein, we report the heating ability of bare SPIONs and core-shell type nanoparticles and test their efficacy as drug delivery carriers. The synthesis of nanoparticles was carried out using the procedure reported in the literature and the anticancer drug doxorubicin was encapsulated in the core-shell. The results suggest that the drug loading efficiency increased upon coating and drug release is much more controlled under the alternating magnetic field which indicates that core-shell type nanoparticles are promising drug delivery systems for magnetic hyperthermia based cancer therapy.

Resume : Antibody and polymer coated gold nanoparticles in the 15 and 30 nm core diameter range are presented as radiosensitizing agents in the treatment of the head and neck squamous cell carcinomas. The presented parameters and configuration of the functionalizing capping layer allow to control the solution stability, targeting functionality and overall toxicity of the nanocomplexes. The various dependencies and characterizations to obtain this organic interface layer on the inorganic core material are identified and eventually, by targeting the epidermal growth factor receptor on the cell surfaces with the proposed configurations, internalization of the nanoparticles in the cell is obtained. Next, evaluation of the cellular structure after delivery of low dose irradiations, and study of the various downward cell signalizations allow to understand the metastasis process behind this localized eradication of the malignant cells.

Resume : Multiphase solid materials containing nano-scale components have become a subject of considerable interest due to benefits that they offer compared to single phase materials. Among these, hybrid nanocomposites composed of inorganic nanoparticles incorporated into a host material have attracted much attention as alternative sorption media for heavy metals removal. The synergistic effects of two components reduce limitations observed in more commonly used single phase granular media, such as excessive pressure drop in fixed bed columns and the risk of release of nanoparticles into the environment. In this study we present a novel concept of hybrid filters dedicated for water pre- and post-treatment, combining capacities of solid particles retention and arsenic (As) ions removal. Commercial deep bed filters composed of a polypropylene (PP) non-woven fabric with fibres of diameter sizes in the range of 0.2 – 30 µm have been modified with various allotropies of iron oxide nanoparticles. Obtained hybrid filters have shown an increase in filtering efficiency of the most penetrating particle size of c.a. 20 – 40% compared to unmodified filter. Preliminary adsorption tests demonstrated that such hybrid filters exhibit a high efficiency of removal of As to below required limits of 10 µg/L from a spring water with moderate As concentration.

Resume : Organic semiconducting single crystals (OSSCs) have been studied during the last years because of their good electrical properties, which allow to fabricate transistors or direct x-ray detectors. Inkjet printing techniques can be used to print solutions from which OSSCs are grown. However, more understanding of the crystal growth process is needed to fruitfully exploit the inkjet printing technique for producing organic-electronics-based devices. Here we report on the use of different Self-Assembled Monolayers (SAMs), deposited via either drop casting or inkjet printing onto gold substrates, as a way to control the morphology of TIPS-Pentacene (a well know organic semiconductor) single crystals and their characteristics of electrical exchange with the electrodes. In particular, the morphology of TIPS crystals and their electrical characteristics are reviewed against the different types of SAMs applied to the electrodes. Considerations over the effect of the different SAMs on the morphology of the developed crystals are made, and criteria for choosing SAMs able to maximize the charge transport at the crystal/electrode interface are discussed.

Resume : One of the most prolific areas of current research is focused on the synthesis of Nanoscale Coordination Polymers NCPs. The selection of the metal ion and the ligand allow the design and synthesis of NCPs with specific properties (chemical or physical), catalytic and biological activities, applications in gas storage, separation processes, magnetic materials, homogeneous catalysis, as precursors of metal oxides and also as chemotherapeutic agents or in drug delivery. The characteristics of the Zn(II) ion and the fact that Zn(II) complexes with O-donor ligands usually have antibacterial activity, have triggered the development of novel multifunctional Zn(II)-NCPs. Moreover most of the homochiral Zn-NCPs known have polydentate organic ligands with N and O donor atoms but those derived from naturally occurring and nitrogen free compounds are scarce. Here we present several Zn-NCPs, isolated from Zn(II) acetate dihydrate, using cheap and easily controllable processes at room temperature, with their X-ray crystal structures and evidence of their homochiral nature. A comparative study of the influence of the organic multitopic ligands on their thermal stability and their conversion to pure ZnO is also reported. The new products are excellent candidates for their utility in different areas (printed electronics, catalysis…) or for their potential biological activity or uses (as carriers in drug delivery among others).

Resume : A novel fast, low-cost and easy procedure to generate polymer-nanofibers was used to make P3HT nanofibers-based chemiresistors. The so-obtained device is sensitive to acetone gas concentrations as low as 3 ppm, with linear response up to 30 ppm. Additionally, these sensors showed very fast response times, with complete baseline recovery within 10 seconds from the signal maximum at each tested analyte concentration. Most notably, these performances are reproducibly achieved using different gas carriers, namely nitrogen and air, suggesting that the recorded response is little dependent from the gaseous environment in which the detector is operating.

Resume : Soft lithography, a family of conformal contact processes using a patterned elastomer stamp, offer low cost high throughput alternatives for the patterning of functional ceramics and other inorganic materials. They have been receiving considerable interest due to their simplicity, scalability and mild processing conditions, which makes them compatible with many materials and substrates. This presentation highlights a number of soft lithographic fabrication tools that we developed to micropattern metal oxide films, nanoparticles, organically modified silicas and graphene on substrates such as Si and flexible plastics. Printing or molding successive layers to realize 3D stacks and patterns is also possible. All soft patterning methods use elastomeric molds and stamps with a (sub)micron-sized relief pattern. At very high resolution, the easy mechanical deformation of the protruding features of the elastomer becomes a limiting factor. It is possible to use stiffer, less deformable elastomers to pattern smaller features, but they exhibit poorer adhesion to the substrate, and tend to leave residue layers. We developed a couple of new approaches to deal with this limitation, thus allowing lateral resolutions down to 50 nm in some of our processes. The applicability of soft patterning will be illustrated, e.g. by 3D cathode materials for Li batteries, graphene micropatterns on PET plastics, and ZnO micropatterns as sacrificial templates for subsequent deposition of epitaxial (La,Sr)MnO3 by pulsed laser deposition.

Resume : There has been a great deal of interest in the patterning of nanogap electrodes in recent years, owing to their potential as enablers of technologies based on molecular electronics, plasmonics and spintronics. While conventional techniques can be used to pattern symmetric nanogap electrodes on the order of 10 nm or below, complex nanopatterning methodologies are required to obtain asymmetric nanogap electrodes, such as the molecular ruler technique [1], electrodeposition [2] or atomic layer lithography [3]. Such asymmetric nanogap electrodes are key for a variety of nanoelectronic devices including nanoscale organic light emitting diodes (nano-OLEDs), nanoscale photodiodes and nanoscale Schottky diodes [4]. However, the above patterning techniques suffer from low throughput and poor scaleability, particularly over large-area substrates. In the past, we have reported on adhesion lithography, an unparalleled large-area nanogap patterning technique [5]. The process involves the modification of surface energies using self-assembled monolayers and has allowed the patterning of sub-15 nm nanogaps. Herein, we present advances in the technique and frame them within the current state of the art in asymmetric nanogap electrode patterning. Specifically, we detail advances in minimising gap dimensions to below 10 nm, increasing gap fabrication yields to > 90 % and boosting the width of the nanogaps up to 1 m, to achieve aspect ratios in excess of 108. Furthermore, we expand the catalogue of metal electrode materials possible to employ to include Al, Au, Ag, Cr & Ni, and show that this unique technique is compatible with a variety of flexible polymeric substrates. Finally, the unique advantages of these structures will be outlined, with emphasis large-area solution processed electronic and optoelectronic devices. [1] S. Johnson, D. Evans, G. Davies, E. Linfield, C. Wälti, Nanotechnology 20 (2009) 155304 [2] M. Deshmukh, A. Prieto, Q. Gu, H. Park, Nano Lett. 3 (2003) 1383 [3] X. Chen X, H. R. Park, M. Pelton, X. Piao, N. Lindquist, H. Im, et al. Nature Communications. 4 (2013) 2361 [4] J. Semple, S. Rossbauer, C. Burgess, K. Zhao, L. Jagadamma, A. Amassian, M. McLachlan, T. D. Anthopoulos, Small 12 (2016) 1993–2000 [5] D. Beesley, J. Semple, L. Jagadamma, A. Amassian, M. A. McLachlan, T. D. Anthopoulos, J. de Mello Nature communications 5 (2014) 3933

Resume : Controlling the nano-scale structure and morphology of molecular thin films is a key aspect in plastic electronics, as it is typically associated with charge transport and exciton mobility. One promising strategy for tuning the supramolecular architecture of organic films is the post-deposition activation of latent hydrogen bonds between conjugated moieteis suitably functionalized with labile functionalities, whose thermal cleavage leads to the formation of stable, crystalline, molecular aggregates. This strategy has been used to produce high-mobility ambipolar organic field-effect transistors and, more recently, to enhance the performances of bulk-heterojunction solar cells. We demonstrate, for the first time, that latent hydrogen bonds between organic moieties can be activated also by light, which provides the thermal energy necessary for direct laser writing of crystalline semiconducting nanopatterns with diffraction limited resolution. Our molecule of choice is a solution-processable diketopyrrolopyrrole (DPP) derivative, which, in its pristine state forms non-conductive, amorphous films. Optical patterning results in highly resolved crystalline nanostructures of deprotected DPP molecules, as confirmed by side-by-side differential scanning calorimetry and GIWAXS analysis. Thin-film transistors based on pristine and photo-converted DPP reveal over 1000-fold increase in hole mobility, reaching 10-3cm2/Vs, which matches state-of-the-art hole transporting molecular materials.

Resume : The use of graphene as the base electrode in bipolar transistors (GBT), have theoretically shown devices capable of working in the THz regime [1]. The electric current between emitter and collector electrode in GBTs would be controlled by the potential of the base electrode which is isolated by the band gap of two semiconductors. This concept is based on a vertical arrangement of graphene and the semiconductors. Here we use n-type amorphous silicon (a-Si:H) as semiconductor material to bring in contact with graphene. Therefore, a step-wise electrical and structural characterization of the a-Si:H/graphene interfaces is a requirement for the understanding and implementation of GBTs. For this purpose, we investigated the plasma-enhanced chemical vapor deposition of a-Si:H on graphene at different deposition stages and doping levels. Using plasma excitation frequencies larger than 100 MHz, instead of the standard 13.56 MHz, we provide a gentler deposition of a-Si:H onto graphene, as it is reported that ion energies decrease with increasing plasma excitation frequencies [2]. Here we will present the atomic force microscopy characterization of the different growth stages of a-Si:H on graphene, the electrical characterizations for the type of contact and IV behavior of these interfaces. [1] W. Mehr et al. Vertical graphene base transistor, IEEE Electron Device Lett, 33, 5 (2012). [2] G. Lupina et al. Plasma-enhanced chemical vapor deposition of amorphous Si on graphene, Appl. Phys. Lett. 108, 193105 (2016).

Resume : In the present work, role of isolated palladium (Pd) and tin oxide (SnO2) nanoparticles (NPs) deposited on graphene (G) has been investigated in terms of gas sensing characteristics of ethanol and H2 gas at different temperatures. The difference in modification the properties of (SnO2)/G and Pd/G interfaces leads to improvement in selectivity and sensitivity of the chemiresistive sensors. It is observed that, incorporation of isolated Pd NPs on the graphene facilitates the room temperature sensing of H2 gas with fast response and recovery time. In contrast, isolated SnO2 NPs on graphene enables the detection of ethanol at room temperature. However, combination of isolated Pd and SnO2 NPs on graphene results in improvement in the sensitivity for both ethanol and H2 gas. The above results have been explained on the basis for interface formation between G and NPs. These results are important for developing a new class of chemiresistive type gas sensor based on change in the electronic properties of the G and NPs interfaces.

Resume : Over the past decade, Electrochemical Advanced Oxidation Processes (EAOPs) have experienced significant developments, showing great efficiency for the decontamination of wastewater polluted with toxic and persistent pesticides, organic synthetic dyes, pharmaceuticals and personal care products. The most popular technique among them is the electro-Fenton (EF) process, in which H2O2 is generated continuously at the cathode with O2 or air feeding while an iron catalyst (Fe2+, Fe3+, or iron oxides) is added to the effluent. Both iron and hydrogen peroxide react together to generate hydroxyl radicals, mainly oxidant for the treated solution, as shown in the following equations [1]: Fe2+ + H2O2 → Fe3+ + •OH + OH- Since this reaction takes place in acidic medium, it can alternatively be written as: Fe2+ + H2O2 + H+ → Fe3+ + •OH + H2O In this study, reduced Graphene Oxide (rGO) was electrochemically deposited on carbon felt (CF) in order to design a novel cathode applied in electro-Fenton (EF) process for the decontamination of wastewater polluted with persistent organic pollutants (POPs). The effective destruction of POPs by EF process is substantially dependent on the production of H2O2. This r-GO modified cathode enhanced the generation of H2O2 through the improvement of the hydrophilic characteristic and the conductivity of raw carbon felt, proved by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results [2]. The essential factors affecting the modification, such as current density value, time of graphene oxide (GO) deposition and electrochemical reduction to form reduced graphene oxide (rGO), were investigated. The structures of GO, rGO, CF and rGO-CF were characterized by SEM, XRD, XPS and contact angle measurements [3]. Degradation kinetics of dyes (Acid Orange 7) and pharmaceuticals (Paracetamol) were investigated and mineralization rate (i.e. conversion from organic to inorganic carbon) was determined. The degradation of POPs on rGO-CF cathode is much higher than on raw CF, proving that rGO-CF is a powerful promising electrode for improving removal efficiency of pollutants using EF technology. [1] Thi Xuan Huong Le, Christophe Charmette, Mikhael Bechelany, Marc Cretin, Facile Preparation of Porous Carbon Cathode to Eliminate Paracetamol in Aqueous Medium Using Electro-Fenton System, Electrochimica Acta 188 (2016) 378–384. [2] Thi Xuan Huong Le, Mikhael Bechelany, Joffrey Champavert and Marc Cretin, A Highly Active Based Graphene Cathode for Electro-Fenton Reaction, RSC Advances, 2015, 5, 42536 – 42539. [3] Thi Xuan Huong Le, Mikhael Bechelany, Stella Lacour, Nihal Oturan, Mehmet A. Oturan, Marc Cretin, High removal efficiency of dye pollutants by electron-Fenton process using a graphene based cathode, CARBON 94 (2015) 1003–1011.

Resume : Multiple layers of graphene thin films and graphene nano-sheets were grown on different substrates (i.e., polycrystalline nickel foil, Ni(111), HOPG(0001)) using remote Plasma-Enhanced Chemical Vapor Deposition (rPE-CVD). As a novel basic approach to this technique, a new remote low-pressure RF plasma source has been used to (i) minimize the effect of the plasma electrical field on the orientation of resulting graphene nano-sheets, (ii) decouple the dissociation process of the gas from the growth process of graphene on the substrate, (iii) warrant for a low graphene defect density via slow plasma kinetics, (iv) tune the feedstock gas chemistry in view of improving the graphene growth, and (v) reduce the growth temperature as compared to conventional chemical vapor deposition (CVD). In order to assess the quality of the resulting graphene layers Raman spectroscopy, x-ray photoemission spectroscopy, scanning electron microscopy, and scanning tunneling microscopy were used. A systematic characterization of the samples based on a sequence of measurements and detailed cross-checks - together with a comparison with other carbon allotrope references - is reported. Last but not least, the inherent "add-on" characteristics of this remote new plasma source warrants for a remote plasma deposition process compatible with typical UHV surface science requirements before/after the deposition process.

Resume : In this study, the structural stability and electronic properties for two-dimensional (2-D) material were investigated using monolayer Cr2C, which is one of the MXene, with mixed functional groups. Interestingly, unlike the typically 2-D material with mixed functional groups, the F and OH functional groups on each side of Cr2C, Cr2CF(OH), have negligible effect on the magnetic and electronic characteristics of the other side. The unique phenomenon results from slight differences in the geometry of each functional group side, such as the coordination number, bond length, and thickness from those of Cr2CF2 and Cr2C(OH)2 despite the mixed functional groups. Because of the preserved magnetic moments of the Cr atoms bound with each functional group, Cr2CF(OH) shows ferrimagnetism without the entire offset of the magnetic moment. Similarly, the semiconducting properties with an indirect band gap are presented due to the relative position of the energy levels in each spin band whose atomic contributions are maintained from Cr2CF2 and Cr2C(OH)2, respectively. On the basis of these findings, when each surface of the monolayer Cr2C is terminated by the other functional groups, it is expected that the magnetic and electronic characteristics of Cr2C-based MXene are easily anticipated using the previous reported MXene with one functional group on each side.

Resume : The recent discovery of 2D materials has opened up novel exciting opportunities in terms of functionalities and performances for spintronics devices. One of them is to address the issue of the oxidation of ferromagnetic materials which considerably limit the use of air/wet processes in the fabrication of devices. The recent progress on the growth of graphene and h-BN by chemical vapour deposition on top of ferromagnetic catalysts like Ni[1] or Fe[2] has permitted to circumvent this issue. We will first show how a thin graphene passivation layer can prevent the oxidation of a ferromagnetic electrode of Ni while adding a new interesting spin filtering property[3] . We will then present how this study enabled the use of the advantageous but oxidative technique of ALD to deposit homogeneous working sub-nanometer tunnel barriers in vertical spin valves[3]. We will finally highlight the passivation properties of a monolayer of h-BN on top of Fe and show the resulting successful integration of h-BN as a tunnel barrier in magnetic tunnel junctions[4]. These different experiments unveil promising uses of 2D materials for spintronics. [1] Weatherup et al ACS Nano 6, 9996 (2012) [2] Caneva et al Nanoletters 15, 1867 (2015) [3] Martin et al ACS Nano 8(8) 7890 (2014) [4] Piquemal et al APL 108(10), 102404 (2016)

Resume : Hybrid organic-inorganic perovskites have recently emerged as an important class of semiconductor materials, exhibiting remarkable performance in photovoltaics and light emitting applications. To further improve the device efficiency based on these materials, an insightful understanding of the interfacial charge transfer (CT) and charge recombination (CR) processes is highly required. Here, we report for the first direct experimental observation for the tremendous impact of perovskites nanocrystals (NCs) shape on the interfacial CT process in presence of a molecular acceptor. A dramatic change in CT and CR dynamics at the interfaces of three different NCs shapes: spherical, platelets and cubic are recorded in real time. Time-resolved data clearly demonstrated that the degree and the mechanism of interfacial CT and CR in these systems are greatly affected by the NCs shape. More importantly, the results demonstrated that the complexation on the surface of NCs acts as an additional deriving force for tuning the CT dynamics. Moreover, we found that CT at the interface of the spherical and cubic shape is static and dynamics in nature, respectively. On the other hand, platelets shape exhibits a combination of static and diffusion controlled mechanisms. This new observation opens up a new venue for further developing pervoskites NCs-based applications.

Resume : The selective dispersion of semiconducting carbon nanotubes (s-SWNT) by wrapping with conjugated polymers has enabled their application in electronic and optoelectronic devices such as field-effect transistors and light-emitting field-effect transistors. Here, we show that the dispersion process can be easily scaled-up while maintaining good photoluminescence yield (~2%) and nanotube length (>1 µm) to obtain s-SWNT networks with excellent optical and electrical properties. We demonstrate ambipolar charge transport and near-infrared light-emission in field-effect transistors based on monochiral and mixed networks of s-SWNT at low voltages. We investigate the influence of the nanotube diameter distribution on charge transport within the network depending on the applied gate voltage and thus charge carrier density. Voltage-dependent photoluminescence and electroluminescence spectra provide insight into the charge distribution among the different nanotubes. From these insights we can derive guidelines for optimized nanotube networks for high-performance field-effect transistors.

Resume : Alternating Current Powder Electroluminescence (ACPEL) is steadily reaching higher importance in research due to its advantages such as, low manufacturing cost, low operating voltages, flexible choice of substrates. Still, ACPEL devices face challenges in becoming more wide-spread due to the low amount of light produced. To address this problem, conductive materials like carbon nanotubes (CNTs) have been employed and shown promising results for the fabrication of ACPEL devices due to their high aspect ratio facilitating percolation, local field enhancement and high mechanical- and thermal conductivity. However, pristine CNTs exhibit constant agglomeration problems in solution due to the strong Van der Waals forces and pi-pi stacking interactions between individual tubes. Thus, CNT/phosphor mixtures are usually prepared by crude mixing of CNTs in organic solvents. In this work, we systematically investigated the interface chemistries of CNTs and ZnS phosphors in order to prepare pre-coupled semiconductor-carbon composites for ACPEL applications. Phosphor-carbon composites prepared in aqueous systems by heterocoagulation showed enhanced light output already at low CNT concentrations of 0.01 wt%. SEM images obtained did not only prove better distribution of the CNTs on the surface of the luminescent phosphor, but also proved that the heterocoagulation dynamics can be controlled by varying the mixing method, reaction time and pH.

Resume : We present a controlled assembly strategy for the formation of carbon nanotube - quantum dot nanohybrids, where the terminal ends of individual single-walled carbon nanotubes (SWCNT) are selectively functionalised with single quantum dots (QDs), via the formation of covalent bonds. The assembly, in environmentally friendly and biocompatible aqueous solution, was controlled towards the formation of monofunctionalized SWCNT-QD structures. We use DNA wrapped carbon nanotubes, where the DNA acts as a surfactant for the dispersion of the nanotubes in water. Moreover, the DNA’s helical wrapping on the sidewalls of the tubes leaves only the terminal ends of the SWCNTs available for direct functionalization. Atomic force microscopy has been used to image the nanostructures and allowed us to identify the nanodots exclusively at the terminal ends of the tubes. Photoluminescence studies in solution and on surfaces at the single nanohybrid level showed evidence of electronic coupling between the two nanostructures. Quenching of photoluminescence of the CNT-QD nanohybrids in solution has been observed which indicates an electronic coupling between the two nanostructures as previously observed in QD-SWCNT composites. The photoluminescence blinking dynamics of conjugated and un-conjugated individual quantum dots was investigated showing larger off-state probability densities for QDs attached to the tubes, suggesting an increased photoinduced charging of the nanocrystals. The ability to covalently couple heterostructures with single particle control is crucial for the design of novel QD-based optoelectronic and light-energy conversion devices.

Resume : Experimental studies of semiconducting carbon nanotubes (CNTs) doped with gold chloride have shown a remarkable downshift in the Fermi level [1]. Furthermore, the sheet resistances of the CNT thin films have been found to decrease in the doping process [2]. In the present work, we investigate computationally the influence of AuCl4 molecules on the band structures and intratube electron transport of single-wall semiconducting CNTs as well as on the intertube transport. Calculations are carried out with the FHI- aims code package based on the density-functional theory within the hybrid functional and non-equilibrium Green?s function formalisms [3,4]. According to our results, there is a strong charge transfer from CNTs to AuCl4 molecules and CNTs become metallic. Moreover, AuCl4 molecules linking CNTs decrease remarkably the intertube resistance. The decrease of intertube resistance due to acid treatment has been seen also in experiments [2]. These two effects, metallization of CNTs and decrease of the contact resistance, improve significantly the conductivity of CNT networks. [1] K. K. Kim et al., J. Am. Chem. Soc. 130, 12757 (2008). [2] A. Znidarsic et al., J. Phys. Chem. C 117, 13324 (2013). [3] V. Blum et al., Comput. Phys. Commun. 180, 2175 (2009). [4] T. Ketolainen et al., J. Chem. Phys. 142, 054705 (2015).

Resume : The processes of anomalous mass transfer are studied in the Al?Fe system. An aluminum alloy 2024 (D16) were processed with ultrasonic impact treatment (UIT) using a pin or intermediate plate made from Armco-iron. The UIT process was carried out at the amplitude of ultrasonic horn tip of ~25 ?m for different time (50 s to 250 s) under quasi-hydrostatic shock compression of the diffusion pair in air or neutral environment (argon) to avoid the oxidation of the contacting surfaces. When an intermediate Armco-Fe plate was used, the maximum concentration of Fe in the surface layer of the UIT-processed 2024 alloy was of ~10 at.%, and segregations of Cu (up to 30 at.%) were also observed in some local surface areas. After UIT, the surface of Armco-Fe plate contacted with the 2024 alloy contained up to 90 at.% of Al, and mass transfer other components of the 2024 alloy (Cu, Mg and Sn) occurred. The use of the Armco-Fe pin at UIT results in the intensification of the Fe mass transfer deep into the surface layer of the 2024 alloy, and in the formation of banded structure with different phase and elemental compositions of each of the bands, which depend on the duration and environment of the UIT process. In this case, the surface of the Armco-Fe pin did not contain Al or other components of the 2024 alloy. Double increase in microhardness of the 2024 alloy after UIT in a neutral environment (HV ~3 GPa) in comparison with that of the initial state (HV ~1.4 GPa) was observed regardless the presence or absence of the Armco-Fe plate between the treated surface and loading instrument. Severe plastic deformation of the surface layers of the 2024 alloy at the UIT through the Armco-Fe plate occurs less intensively because of the lower impact energy, which is partially dissipated by the Armco-Fe plate. Thus, to explain aforementioned similar magnitudes of microhardness we should account for some additional factor providing surface hardening of the 2024 alloy at presence of Armco-Fe. It is suggested that this factor is mechano-chemical interaction of Al with Fe and Cu, which promotes the formation of inclusions of Al-Cu-Fe intermetallic phases. The highest hardening (up to ~8 times) observed after the UIT process of 2024 alloy the Armco-iron pin in air environment was explained both by the essentially decreased size of coherent scattering areas and by the increased microstrains in crystalline lattice, as well as by the mechano-chemical oxidation of the processed surface during the severe plastic deformation at UIT.

Resume : Galvanic replacement reaction (GRR) involves a redox couple wherein oxidation of a metal and deposition of another metal occurs simultaneously. GRR, when occurs on a nanoscale template material, can yield nano structures with tunable morphologies and composition in a very facile, simple, and rapid manner. Here, we showcase how GRR can be effectively utilized to fabricate i) Cu dendritic structures with superior catalytic activity and exhibiting superhydrophobicity; 2 ii) Cu2O-Ag semiconductor-metal heterostructures, useful for SERS based chemical sensing and photocatalysis, showing evidences of facet selectivity in GRR. The report on the Cu dendritic structures is the first comprehensive and in-depth study on fabrication, characterization of Cu dendrites with superior performance in its application till date. The Cu2O-Ag heterostructures synthesized here, is one of the very few reports on utilizing Cu2O as template for Ag nanoparticle deposition on variety of templates (octahedra, cubes, cuboctahedra) that shows evidences of facet selectivity during GRR. Deposition of Ag on Cu2O through templated GRR has not been studied as extensively as has been for Au. Moreover, we show that an added surfactant (5-Sulfosalicylic acid, SSA) is necessary for the nucleation of Ag NPs on Cu2O template. Such nanostructures are highly beneficial for many applications such as SERS, self-cleaning surfaces and catalysis as demonstrated here.

Resume : Nanocrystalline (nc) materials, defined as those with a grain size less than 100 nm, have proven to attain exceptional mechanical properties such as strength and hardness that exceed those of coarse-grained and counterparts. However, these nanostructures are inherently unstable at elevated temperature, which limits their service temperatures and expected lifetime. That is mainly because the nano-scale grain size provides a very large driving force for grain growth. Here we thermodynamically stabilized the nanostructure of pure Cu via segregation of Nb at the grain boundaries. This segregation tends to reduce the grain boundary (GB) energy and prevent grain growth at elevated temperatures. The Cu-1%Nb nanostructure was analyzed using X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) techniques. Mechanical properties as a function of annealing temperature were evaluated using Vickers microhardness test. Nano precipitation of Nb occurs at high temperature, which also could pin the grain boundary mobility and allow attaining a hardness value of 2.85 GPa (about 10 times higher than that of conventional coarse grained Cu) after annealing at 1073K, which is about 80% of the Cu homologous temperature.

Resume : D16 aluminum alloy was treated by ultrasonic impact treatment (UIT) in chemically active and neutral atmospheres under quasi-hydrostatic compression, that provided surface strengthening more efficient comparing to the heat treatment and classical UIT schemes. It was shown that simultaneously to the low-temperature deformation of grainstructure dispersion it is possible to form durable oxide coatings with the thickness of several tens of micrometers on the alloy surface by means of UIT on the air. Increasing D16 surface microhardness (up to 2.5 times) by ultrasonic impact treatment in the inert atmosphere (Ar, He) was caused by the modification of dislocation structure, nanocrystalline structure formation due to the deformation and formation of nanoscale precipitates of S'- Al2CuMg hardening phase. It was shown the unique opportunity of increasing surface microhardness (up to ~ 5 times) by ultrasonic impact treatment in liquid nitrogen (77.4 K), due to the influence of synergistic processes of nanostructure formation and mechanochemical interaction of Al with N during cryodeformation. The model of surface strengthening by means of structure and phase mechanisms was offered.

Resume : To improve the fatigue strength of a wide range of the metallic materials methods of the surface severe plastic deformation are used [1, 2]. Investigated the influence of ultrasonic shock treatment (USST) in an inert atmosphere on the structure, phase composition and micromechanical properties of composite coatings formed by embedding of dispersed particles of Al2O3, B4C, BN hardening powders and carbon nanotubes into the surface layers of D16 aluminum alloy. Under influence of severe plastic deformation caused by USST, a partial grinding and powder particles implementation and the nanostructuring of matrix alloy with the deformation composite layers take place. The observed maximum strengthening (200 - 350%) and durability increase (~ 7 times) of D16 alloy surface undergoing due to reinforcement by Al2O3 and B4C particles.

Resume : First sandblasted (SB) of the titanium alloy Ti6Al4V surface at the temperature of liquid nitrogen (-196○C) was performed. For comparison, a standard trestment used as SB in the air under the same parameters and duration. It was shown that the major differences relate microhardness changes roughness, character morphology residual amount of the abrasive particles of Al2O3 on the surface. It was studied in detail the chemical composition in the different local areas of the alloy surface after the SB at room and cryogenic temperatures, as well as their degree of oxidation. It is planned to obtain experimental evidence regarding the fact that the low-temperature sandblasting improves wear resistance of the dental implants in chewing loads improves the corrosion resistance and adhesion strength biocompatible coatings applied to titanium substrate after SB in liquid nitrogen, and thus contributes significantly longer service life.

Resume : Process developing at a free surface of thin metal layers, layered compositions of metals and metal alloys of nanometer thickness thermodynamically determine laws of diffusion mass transfer in the volume. These laws have features of superposition of formation processes of structural and concentration and concentration-phase inhomogeneities due to time distribution of different dominant diffusion mass transport mechanisms (boundary diffusion, diffusion by volume, surface diffusion) with "distortion" of the balance of the driving forces, the idea of which historically formed due to nanoscale factor. As a result during diffusion redistribution in such systems concentration gradients persist and homogeneous concentration distribution is not achieved, unlike processes in a bulk state. Experimental confirmation of this hypothesis has been discovered for a number of multi-layer systems obtained by condensation in a vacuum: Cu-Me (Me – Ni, Mn, Sn, Cr, Co), Cu-Mn-Sn, Cu-Cr-Al, Cu-Ni-Au, Cr-Cu-Ni, Cr-Cu-Ni-Au, Al – Me (Me – Ti, Ni, V, Cr, Ta, Mo, Co), Me-Si (Me – Mo, Ti, Cr, W, Ni, Pt), Pt-Ni-Si, Ni-Ti-Si, Ti-W-Si, Au-Co-Si, Al-Ti-W-Si, Au-Ni-Me-Si (Me – Mo, W, Ti), Au-Me-Mo-Si (Me – Co, Ni, Pt, Pd) etc. We consider the regularities of physical and chemical processes of phase formation on the free surface of nanoscale film compositions that develop during thermal treatment in oxygen- and hydrogen atmospheres. phenomenological and analytical models to describe these processes have been suggested. We discuss the impact of nanoscale factor, which manifests itself in the fact that the phase formation occurs in other sequences and other temperature ranges than it is in the case of bulk materials; phase atypical for solid state are formed in certain temperature ranges. Material science criteria to increase thermal stability of film compositions are predicted based on the analysis of thermodynamic parameters of phases formed and additional driving forces of mass transfer due to the influence of external surface and nanoscale factors.

Resume : Graphene monoxide (GMO), a newly two-dimensional material, is the promising candidate for nanoelectronic device due to its proper band gap for transistor and the high carrier mobility induced by the its low effective mass [1-2]. In this study, we investigated the geometric and electronic structure of bilayer GMO and the influence of the external electric field on bilayer GMO through density functional theory (DFT) calculation. All cases of bilayer GMOs show weak van der Waals interaction similar to typical interlayer bonding of two dimensional bilayer systems. The bilayer GMOs are predicted to have proper band gap for electronic device application (0.418 ̶ 0.448 eV). Above all, when applying the electric field to bilayer GMO, the band gap of bilayer GMOs responds more sensitively to the external electric field than the other bilayer two-dimensional system and thereby the semiconductor-metal transition (SMT) occurs in range of 0.21 ̶ 0.3 V/Å. [1] E. C. Mattson et al., Evidence of nanocrystalline semiconducting Graphene monoxide during thermal reduction of graphene oxide in vacuum, ACS nano, 12, 9710-9717 (2011) [2] H. H. Pu et al., Strain-induced band-gap engineering of graphene monoxide and its effect on graphene, Physical review B, 87, 085417 (2013)

Resume : We present the sustainable synthetic process of Fe3O4 nanocrystals. Thermal decomposition of Fe(acac)3 in 1-hexadecanol leads to the formation of Fe3O4 nanocrystals with controlled size and morphology. Formation mechanisms have been elucidated on the basis of GC-MS analysis, which make it possible to large-scale preparation. Structural characterization has been carried out by TEM and XRD. Moreover, we have prepared Fe3O4 nanocrystals with the recycled solvent recovering from initial process. The resulting Fe3O4 shows increased average sizes with irregular pores in nanocrystals. Because 1-hexadecanol can be used repeatedly without any waste, the whole process consumes only iron precursor. This synthetic method has high yield, good reproducibility, and convenient process, which make it possible to large-scale preparation for industrial application.

Resume : Platinum shows outstanding catalytic activity for electrochemical reactions in polymer electrolyte membrane fuel cells. However, the limited reserves and high cost of Pt have directed recent researches toward finding ways to reduce Pt loading by enhancing its catalytic activity and stability. Controlling the shape of Pt nanocrystals is one of the important strategies that influences binding strength between Pt active sites and the adsorbed chemical species thus the catalytic activity. Currently, Pt octahedra enclosed by {111} facets show higher catalytic activity toward oxygen reduction reaction compared to the Pt cubes enclosed by {100} facets. However, those studies revealed the synthesis of Pt octahedra by incorporating transition-metal additives as a capping agent, which could be alloyed with Pt during the synthesis. Because the catalytic activity of Pt-based catalysts is highly dependent on the alloying metals, it is needed to prepare pure Pt octahedra and cubes to investigate the catalytic behavior on Pt{111} and Pt{100} facets. We here introduce, as the first time, a facile synthesis of Pt octahedra and cubes by manipulating the reduction kinetics without adding any metal additives. The morphologies of well-controlled Pt octahedra and cubes were observed by typical transmission electron microscopy.

Resume : Nowadays, there is an emergent expectation and demand for developing efficient protocols for controlling the emissions of pharmaceuticals to reduce their presence in waters and wastewaters. Processes based on adsorption are particularly promising because of their high efficiency, low cost, versatility, as well as availability of different adsorbents. It should be emphasized that successful applications of adsorption processes cannot be considered separately from the production of new adsorbents on both the laboratory and industrial scales. One of the widely studied class of potential sorbents are nanoporous silica materials. Those materials possess high specific surface areas, well-ordered pore structures with adjustable uniform mesopores, and large pore volumes. In addition, their surfaces can be easily functionalized to create tailored surface chemistry. As a result of surface and structural properties, their applications as adsorbents in various environmental processes related to the removal of pollutants from water including heavy metals, dyes and pharmaceuticals have been extensively studied. Above-mentioned exceptional properties of nanoporous silica materials are very attractive particularly for the adsorption of biological molecules, particularly bulky ones such as pharmaceuticals. The aim of this lecture is to provide a brief up to date review of nanoporous silica materials as potential sorbents of pharmaceuticals from waters and wastewaters, as well as to present our own experimental results on the silica-based nanoporous materials? design and synthesis. Strategies on the synthesis and the resulting properties with respect to the envisaged applications will be discussed.

Resume : General approaches were formed by us to the organization of computer calculations based on the «data base science and computer materials design» methodology applied to increasing of temperature and time stability and reliability of thin-film metal contacts for new generation of solar cells. To solve the "computer materials design" problems we have proposed and tested the interpolation approach, which involves the solving both direct and inverse problems. The aim of solving of the direct problem is the construction of the interpolation polynomial from the existing discrete databases, where all compositions or part of the composition intervals are in correspondence with the physical properties. After the construction of such interpolation polynomial the inverse problem is solved: what materials compositions can provide the predetermined properties. Solving of the inverse problem requires a large number of costly experiments (inverse problem of the 1st kind), some of which can be changed through the application of quantum simulation modeling methods (inverse problem of the 2nd kind), e.g. – ab initio methods. According to the developed interpolation approach we made the necessary calculations and defined the prospective search areas of metallic materials compositions and combinations that will slow down the processes of solar cells degradation.

Resume : A passive film is very important to a corrosion resistance of stainless steel. SUS304 steel has the higher resistance than many other stainless steels. This is due to that its passive film is naturally formed and self-regenerated at ordinary temperature and pressure1): SUS304 is a native functional material. As structures of the film on SUS304, two models have been ever proposed2),3). One of them is a network structure composed of Cr-oxide and -hydroxide, and the other is a bilayer structure of Cr-hydroxide/-oxide/SUS304. However, the definitive experimental evidences have not been reported yet. In this study, we investigated the detailed structure using synchrotron XAFS and XPS. To achieve surface sensitive XAFS spectra, the conversion electron yield (CEY) mode was adopted. The Cr-K edge CEY-XAFS spectrum clearly showed an atomically ordered network structure (at least <10 Å) similar to an Cr(IV) oxide. The FEFF simulation revealed that the crystal lattice of the network is “rutile type”. The high resolution O 1s XPS spectrum showed that the local structure of the network is a chromium oxyhydroxide (e.g., -O-Cr-OH-), which forms by a reaction between the oxide and water. Also, besides the network, the normal Cr(III) oxide was independently observed in the film. Since the O 1s peak ratio of the normal oxide to the network increased with incident photon energy, it was indicated that the oxide deposits near the interface of the film/SUS304. These results explain that the base metal is prevented from corroding by the dense passive film. We hope to apply the network structure to other steels in order to make more functional SUS. 1) Massoud et al. J. Electrochem. Soc., 2013. 2) Okamoto, Corros. Sci., 1973. 3) Maurice, J. Electrochem. Soc., 1996.

Resume : We show that the type of copper foil pre-treatment has a significant influence on the resultant graphene formed. We explored electropolishing with two different solutions: 1) water solution of phosphoric acid and 2) a mixture of phosphoric acid, water, ethanol, isopropanol and urea. Samples were electropolished for different voltage and time. The quality of the surface after electropolishing was measured by AFM, SEM and UV-Vis to compare their roughness and reflectance. Before graphene growth the copper foils were annealed in air in order to remove unwanted carbon residuals and in a hydrogen atmosphere to reduce the surface and also to rebuild the crystalline structure. The quality of the grown graphene was measured using light microscopy, SEM and Raman spectroscopy. We show that the surface quality has significant effect on the way that graphene grows.

Resume : Nanowire-based solar cells are attractive due to their ability to increase light absorption while reducing the amount of material used in thin film photovoltaic devices. In particular, III-V nanowires can be grown on silicon substrates to form a tandem solar cell, a promising system able to reach high efficiencies at relatively low costs. However, the design of such solar cells should be carefully optimized to obtain high absorption of light and efficient collection of carriers. In this work the optical and electrical simulations are coupled in order to define the optimal structure for tandem solar cells based on GaAlAs nanowire on silicon. Electromagnetic simulations are carried out with the home-made RCWA software to define the best NWs geometry for the absorption of light under current matching conditions. The optimal geometries deduced from the optical simulation are then used for the electrical simulation. The coupling between optical and electrical simulations is performed by computing a map of the optical generation rate in the structure, which is used as an input for the electrical simulation via the commercial TCAD software Sentaurus. From the electrical simulation, the power conversion efficiency is deduced which allows to analyze the influence of carrier transport mechanism, bulk and interface recombination, junction depth and doping profile, tunnel junctions, etc. in the multijunction structure.

Resume : Thermoelectric modules interconvert thermal gradients for power generation through Seebeck effect. Restricted by its low efficiency, measured by a dimensionless parameter ZT (function of Seebeck coefficient, electrical and thermal conductivities), it finds niche applications. Nanomaterials allow tailoring of the interdependent parameters, which opens up new avenues to enhance efficiency. Low thermal conductivity with a wide range of density of states and phonon electron scattering in nanomaterials make them ideal for thermoelectric applications. When the dimensions of the material are comparable to the mean free path of the phonons, the thermal conductivity drops significantly due to surface scattering mechanism. Nanowires with modulated diameter would further decrease the thermal conductivity substantially as the corrugations would act as a trap for phonons and reduce transmitivity. In this work, dense forest of diameter-modulated silicon nanowires will be grown through template-assisted Chemical Vapor deposition (CVD). Nanoporous alumina, commonly used as templates, is fabricated by anodizing aluminum in acidic electrolytes. The diameter and porosity of the template depend largely on the applied voltage. In order to fabricate porous template with modulating pore diameter, method of pulse anodisation is employed which consists of periodic potential surges. Structural engineering along the film growth direction is achieved by deliberately designing the potential pulse sequences. The arrangement of the pores on the surface is improved by the use of nanoimprint lithography and double anodisation method. The resulting highly ordered and dense structure of modulated pore diameter is suitable as templates for growing nanowires. The diameter of the Si nanowire segment is predefined by the internal pore structure of alumina. Growth of Si nanowires is underway through CVD. Sensitive 3-omega measurements will be carried out on the forest of nanowires to confirm the reduction in the thermal conductivity of Silicon.

Resume : We demonstrate the chemical modification of graphene oxide and the influence of its chemical composition on its sensing ability. Graphene oxide was obtained using a modified Hummers’ method. Additionally, we explored the samples reduced with ascorbic acid and sodium borohydride and also investigated the impact of thiol functional groups on its sensing ability. The sensors were fabricated via drop coating of graphene-based material onto interdigitated chip surfaces. Basic analysis of the explored materials were performed with FTIR spectroscopy, Raman spectroscopy, scanning electron microscopy (lateral size) and atomic force microscopy (height). The sensing responses were measured for different concentrations of ethanol vapors and nitrogen dioxide.

Resume : Femtosecond laser pulses with high emission intensity and low photon energy can be used for uniform modification of a-Si:H films [1] and to achieve anisotropy of their structural, electrical and optical properties. For example, surface periodic structures (ripples) can be produced [2]. In this paper, a-Si:H films treated by femtosecond laser pulses (1250 nm, 100 fs) were investigated. A surface profile with period equal to the laser spot diameter (150 μm) was formed by means of laser beam movement in the raster mode. Scanning electron microscopy also revealed presence of the ripples, perpendicular to polarization of the incident beam on the treated surface, with 0.36±0.03 μm period. The electric conductivity of a-Si:H film after irradiation with femtosecond laser pulses increases by almost 3 orders of magnitude due to dehydrogenation and nanocrystallization of the film [3]. Due to non-uniform crystallization of amorphous silicon and the electric field depolarization by periodic structure, the conductivity along the scan lines and periodic structures is almost threefold greater than in the perpendicular. The work was financially supported by the Russian Foundation for Basic Research (project 16-32-80066). [1] A. V. Emelyanov, M. V. Khenkin, A. G. Kazanskii, et al. Thin Solid Films 556, 410 (2014) [2] R. Drevinskas, M. Beresna, M. Gecevičius et al. Appl. Phys. Letters 106, 171106 (2015) [3] A.V. Emelyanov, A.G. Kazanskii, P.K. Kashkarov et al. Semiconductors 46, 769 (2012)

Resume : Rare Earth Elements (REE) are a group of 17 metals (the so-known as lanthanides plus Ytrium and Scandium), which are increasingly important for many emerging modern applications. Therefore, the development of technologies for their recycling has become a significantly relevant research topic. In this work, a magnetic hybrid nanoadsorbent consisting of an iminodiacetic acid (H2IDA) organosilane derivate grafted onto SiO2 covered g-Fe2O3 nanoparticles was synthesized and fully characterized by FTIR, TGA and 13C CP-MAS solid state NMR. The silica coating process was optimized, resulting in highly stable core-shell nanoparticles. Both REE uptake capacity and desorption efficiency in acidic media were tested by complexometric titration and SEM-EDS analysis revealing very effective and competitive uptake. Selectivity studies with binary REE mixtures revealed a slightly higher capacity towards heavier REE and an appreciable selectivity, especially on desorption. The complexation of the molecular H2IDA with REE under neutral conditions was investigated by single cristal X-Ray Crystallography to produce relevant molecular models, showing an unexpected difference in coordination numbers and binding mode of IDA that potentially provides an explanation for the observed selectivity.

Resume : The functional properties of alloys electrodeposits are defined by the chemical composition including incorporated non-metallic elements such as H, C or O. The quantitative determination of full composition of electrodeposits often is a methodic challenge. In this study the incorporated oxygen and its distribution along the entire thickness of deposited Fe-W layer was investigated by means of glow discharge optical emission spectroscopy (GD-OES) using instrument (Spectruma GDA750). It was calibrated for light elements such as O, H, S and Na using in-house prepared sintered samples. Fe-W alloys were electrodeposited at 20°C and 65°C from glycolic-citrate bath of following composition: 1 M glycolic acid, 0.3 M citric acid, 0.1 M (Fe)2(SO4)3 and 0÷0.5 M Na2WO4; pH 6.5. The influence of bath composition and deposition conditions on distribution of elements in alloyed materials was investigated by GD-OES. Increase in tungstate concentration in the bath from 0.05M to 0.4 M results in the increase in tungsten content from 2 at% to 28 at%. EDS analysis shows a considerable amount of oxygen on the surface and apparent value in some cases exceeds 50 at % (EDS data) while in the deeper layers amount of oxygen is ~15 at.% (GD-OES data). Acknowledgments: Authors acknowledge funding from H2020 (project SELECTA 642642), Research Council of Lithuania (MIP-031/2014) and Moldavian national project (15.817.02.05A). We are also grateful for the cooperation with Spectruma Analytical GmbH.

Resume : CIGS is one of the most promising materials for the fabrication of cost-efficient solar cells, with record power conversion efficiencies above 22 %. In the context of a constant cost reduction, material savings are required for the long-term competitiveness of CIGS solar cells. It can be achieved in ultrathin solar cells with efficient light trapping structures such as nanostructured back mirrors. However, surface recombination at front and rear contacts play an increasing role as the thickness of the CIGS absorber is reduced. In this context, the concept of passivated emitter rear contact (PERC) Si solar cells based on small contacts (i.e. point contacts) surrounded by a passivation layer has been adapted to CIGS solar cells. In this work, we present an in-depth analysis and comparison of passivation layers (Al2O3, SiO2, TiO2) deposited on CIGS. The effect of the passivation layers on the recombination are investigated by steady and time-resolved photoluminescence and cathodoluminescence characterizations, as well as by LBIC and EBIC measurements. Device simulations, calibrated with measured samples, are also used to optimize the spacing between point contacts and get insight in the recombination processes in CIGS solar cells.

Resume : Tin oxide is a widely used transparent conducting oxides and has numerous application. A theoretical study of the same is equally important. Density Functional Theory (DFT) study was performed to analyse the effect of Ni doping on SnO2. GGA-PBE exchange correlation function is used along with basic set of double numeric quality (DNP) to carry out the calculations. The energy convergence tolerance limit was 1.0 x 10-5 Ha/atom. The electronic properties were studied and band structure and density of states of the doped and undoped sample was explored. Electronic structure of Ni doped sample in comparison to pure sample showed better conductivity results. The effect of doping was analysed from density of states graph. A 48-atom SnO2 super cell is considered and Ni atom was used as a dopant for three different structures. Cases were considered for both interstitial and substitutional locations of Ni atom.

Resume : The key factor for efficient water splitting is to optimize band bending at the interface between the semiconductor and electrolyte. Our approach is to induce dipoles inside photoelectrochemical cells (PECs) to lead band bending favorable for water splitting. Ferroelectric materials that have a spontaneous polarization can be one promising material as their polarization domains can be aligned in the desired direction by a poling process. In this work, the vanadium (V)-doped ZnO nanosheets (NSs) were synthesized to apply ferroelectric property as photoanodes for water splitting and systematically investigated poling effects. Spontaneous polarization was induced suitable band bending between photoanodes and electrolyte. As a result, positively polarized PEC electrodes improved water splitting efficiency compared with negatively polarized ones.

Resume : The molybdenum sulfide conjugated materials are the most eminent alternative to Pt for hydrogen evolution reaction catalyst. Heterojunction structures of MoO₃/MoS₂ were fabricated by chemical vapor deposition (CVD) of MoO₃ followed by shallow sulfur doping. Interestingly, morphologies of MoO₃ can be controlled from 2D-blade to 1D-nanorod structures depending on the pressure and temperature in CVD furnace. Molybdenum oxides is well-known for good electron transfer path. But, MoO₃ is limited by poor HER stability. MoS₂ layers are not only good electrocatalyst for HER, but also prevent degradation of MoO₃ in acidic condition. In this study, we will discuss HER-catalytic performance of MoO₃/MoS₂ depending on two different morphologies of MoO₃ based on electrochemical analyses.

Resume : A capillary pen drawing technique was developed as a new patterning methodology for the large-area patterning and fabrication of organic electronics. This approach provided several advantages over conventional approaches: the method was simple and versatile, there were no restrictions on the patterning shapes that could be produced, and the method could be tailored to a variety of substrates. Experimental results suggested several potential application directions for the site-selective patterning technique, including conductive text, electronic art, and electronic array connections. Our approach provides that capillary pen is a quite versatile method to fabricate the soluble organic patterns consisting of the semiconducting/conducting/insulting materials.

Resume : It is well known that Pulsed Laser Deposition (PLD) is a very flexible and versatile technique allowing fast optimization of new and complex material thin films. Among these are Pb(Zr,Ti)O3, PMN-PT, BaTiO3, LiNbO3 and other materials of interest for applications in piezo-MEMS. Furthermore, the unique features of PLD allow for the integration of “Beyond Moore” materials in CMOS and new devices. Using Solmates PLD platform, such devices become now readily available for commercialization. The robust and reliable hardware allows uniform thin film deposition up to 200 mm diameter with high process reproducibility. The process can therefore be easily scaled towards as (pilot) production. In this contribution, the focus will be on wafer scale integration of Solmates new generation high performance PZT thin films. By interface engineering, we demonstrate the possible production of epitaxial piezo thin films on silicon wafers by means of TiN electrodes, buffer layers and nanosheets. Comparison to state of the art textured thin films will be shown. Excellent stability of the electrical and piezoelectric properties of those new films is shown and compared to the properties of state of the art textured PZT thin films grown on standard platinum.

Resume : Nowadays Complementary Metal Oxide Semiconductor (CMOS) Technology demands low power consumption, faster speed performances of devices. Germanium has become again interesting channel material due to its higher (3 to 4 times) carrier mobilities than that of silicon. The main issue with germanium is its native oxide which is water soluble and chemically unstable. Effective passivation is required to overcome this issue. Various passivation techniques have been adopted by different groups on germanium surface such as sulphur passivation, nitride passivation, oxide passivation etc. Among these the nitride passivation is found effective to passivate germanium surface. Here, we are reporting the comparative study of effective passivation of N2 plasma and RTP-NH3. Wherein, we have used thermal and plasma treatment to passivate the germanium surface. NH3 and N2 gases are used for thermal and plasma nitride passivation, respectively. The effect of this passivation has been investigated on HfO2 thin films deposited on passivated germanium. The deposited films have been characterized physically by means of Ellipsometer and XPS. Ellipsometry shows the average thickness of HfO2 films near about 5 nm. Surface roughness has been studied by using AFM technique. To study the electrical properties Cr/Au metal contacts have been formed on both the films by using E- beam evaporator through shadow mask. The comparative study shows the improvement in electrical properties with N2 plasma over RTP-NH3 like, low hysteresis and effective oxide charges. The lower value of flat band voltage (0.22) has been observed for the devices passivated by using N2 plasma. The higher value of density of interface traps has been observed for N2 plasma passivated Ge MOS. The high power plasma (400 W) may be responsible for the high value of Dit and lower value of dielectric constant observed in this work. Keyword: Ge MOS, High-k, Passivation, N2 plasma, NH3 anneal.

Resume : In the last decade, X-B-C (X=Mo, Ta, W) emerged as prospective candidates for protective hard coatings employed in cutting and forming applications. According to theoretical prediction and first experiments, these materials exhibit a high stiffness in combination with moderate ductility. In the present work nanostructured Mo-B-C coatings were prepared on WC-Co hard metal substrates by magnetron sputtering. The microstructure of deposited thin layers was studied by means of scanning and transmission electron microscopy on cross sections prepared using a focused ion beam. Both undisturbed layers and the volume under indentation prints were observed. The microstructure observations were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime using a Berkovich indenter. Crack resistance was tested using indentation experiments with cube-corner indenter. Subsequent annealing of coatings caused elements redistribution and changes in phase constitution. Effect of the microstructure evolution on elastic modulus, indentation hardness and fracture resistance of the coatings is discussed. This research has been supported by the Czech Science Foundation (Project 15-17875S).

Resume : Keywords: zirconia, relative humidity, high pressure, electrochemical impedance spectroscopy, BET, compaction. Nanopowders based on zirconia are widely used in modern high technology. Along with the problem of synthesis of fine homogeneous powder, the problem of obtaining nanoceramics with high physical and mechanical properties from this powder is interesting too. Interparticle forces are prevent at nanopowders sealing. They are proportional to magnitude of surface energy of the system. Nanopowders based on zirconia have high chemical activity of surface. Thus, they can be able quickly change quantitative composition of hydration shell. Structural and thermodynamic energy states of the surface are changed too. Current task is to establish depending of sealing process of nanopowders by high hydrostatic pressure (HHP) from external physical conditions (temperature, humidity, atmospheric pressure). Checking of influence of initial conditions (relative humidity) at sealing process was the aim of this study. As the object of investigation compact sets from ZrO2 + 3% Y2O3 (700° C, 2h) nanopowder was used. Shrinkage, mass losses and specific surface area of samples(using BET-method) to determine the optimal degree of hydration were measured. In parallel, electrochemical impedance spectroscopy (EIS) studies were carried in order to determine dependence of the latter from surface hydration. Measurements of samples shrinkage showed that the maximum level of shrinkage after exposed by high hydrostatic pressure is reached at the level of ambient relative humidity is about 70 % Maximal mass losses of the system after pressure effects were detected at the same humidity. Analysis of BET-data showed that the lowest value of the specific surface area after compression of HHP is observed at 70 %. EIS-data showed that the electrical properties of the system are depending significantly from the ambient humidity. It is shown that humidity increasing from 39 to 94% leads to decreasing of the total resistance of the sample to 55 times (from 2.06MOhms to 37 kOhms). The possibility of establishing correspondence between parameters of electrical impedance and degree of hydration of nanopowders surface was concluded. Results indicate the need to stabilize external physical conditions during manufacturing operations with oxide nanopowders.

Resume : Due to their specific properties, silicon nanocrystals (Si-nc) have recently attracted much interest for their use in silicon-based devices. However, controlling the formation of these nanocrystals (control of diameter and density) in high matrices (semiconductor or dielectric) remains incomplete. The simulation of the deposit and post-treatment steps is therefore necessary for designing the material with the required properties. In this context, this work consists of modeling the formation of silicon nanocrystals by Monte Carlo methods. First, in order to deduct the optimum deposition conditions allowing the obtain of a high density of amorphous silicon clusters and a controlled size, the deposition process of nitrogen doped silicon (SiNx) thin films obtained by a low-pressure chemical vapor deposition technique with a mixture of disilane (Si2H6) and ammonia (NH3) is simulated by using the kinetic Monte Carlo (KMC) method. A Part of this work is dedicated to the study of the formation of silicon nanocrystals in the presence of impurities in a SiNx matrix using the Monte Carlo (MC) method. Simulation results describe well the different stages of the silicon nanocrystal formation. Keywords : silicon nanocrystals, kinetic Monte Carlo, nitrogen doped silicon, silicon clusters, Monte Carlo simulation, crystal growth, crystallization kinetic, impurity distribution.

Resume : Recently, an attention of researchers is focused on studying of functional materials with restructuring of martensitic-type in which a reversible changing in size under the influence of temperature, applied external stress, magnetic fields or combining them takes place and the effects of shape memory, pseudoelasticity (superelasticity), transformation plasticity, magnetoelastic deformation and etc. occur. Such materials find wide application as actuating mechanisms, actuators, sensors and others. Phase transformations of martensitic-type characterize the broad class of materials and alloys. Ageing Cu-Mn-Al alloys with original magnetic characteristics undergo thermo-induced martensitic transformation (MT) as well. Nowadays, such type of MTs which occur after solid solution decomposition with ferromagnetic nanoparticles precipitation in nonferromagnetic matrix attract interest. By thermal treatment, the system of ferromagnetic nano-dispersed particles in the nonferromagnetic matrix can be formed. Herewith, coherent nanoparticles precipitated during decomposition of high-temperature Cu-Al-Mn betta1-phase are coherently connected with matrix and do not undergo spontaneous MT at cooling. In this work, the influence of alloying with Mn as well as regimes of aging of high-temperature phase on subsequent martensitic transformation in Cu-Al-Mn alloy was studied. The morphology of martensitic transformation behaviour as a result of alloy aging under an annealing in a constant magnetic field with different sample orientation relatively to the field and without the field was investigated in order to directly control the process of martensite induction at cooling. The temperature dependences of electrical resistance, magnetic susceptibility, and the temperature and field dependences of magnetization were found. The alloys phase composition and microhardness were determined. The tendency of oriented growth of the precipitation phase particles in a direction of applied field and the increase of volume fraction of these particles under thermal magnetic treatment of material what favours a reversibility of induced martensitic transformation [1]. 1. A. Titenko, L. Demchenko. Effect of Annealing in Magnetic Field on Ferromagnetic Nanoparticle Formation in Cu-Al-Mn Alloy with Induced Martensite Transformation. Nanoscale Research Letters (2016) 11:237, DOI: 10.1186/s11671-016-1453-2

Resume : The influence of mechanical activation on the mechanism of formation of a Ti–Al–Cr alloy has been investigated. Titanium aluminides have aroused considerable interest due to their high heat resistance, high-temperature strength, oxidation resistance, and low density. The indicated properties make them promising materials for the development of protective coatings instead of nickel refractory alloys, used in aerospace engineering. These coatings make it possible to raise substantially the working temperatures of products without changes in the mechanical properties of the substrate, i.e., titanium alloys. On the other hand, low ductility and poor formability restrict considerably their industrial application. A great effort has been devoted to improve the properties of Ti–Al alloys by means of chemistry modification. Mechanical alloying is exploited to produce aluminum–titanium alloys with additional dispersoids. Low-temperature solid-state reaction (SSR), which can be originated in binary or ternary systems by improving a severe plastic deformation as in the case of high-energy ball milling, has been investigated. This may lead to the formation of equilibrium intermetallic compounds. The method of deposition of a protective coating determines requirements to its material. For the detonation-gas method, important factors are morphology and particle-size distribution of sprayed powder, which influence its flowability. It is desirable to obtain spherical particles with a size of 40–60 μm. The optimal regime of mechanical treatment of the initial powders, which provides the beginning of phase formation and accumulation of the sufficient amount of energy for the substantial acceleration of the subsequent process of solid-state synthesis in vacuum in the self-propagating high-temperature mode, has been established. This regime is accompanied by a substantial decreases in the temperatures of beginning and completion of synthesis (below the melting point of aluminum) and provides the formation of intermetallic spherical powders with a mean particle size under 60 μm, which do not require subsequent milling. The investigated protective coatings from the prepared Ti–Al–Cr intermetallic powder sprayed by the detonation method on titanium alloys raise the operating temperature of products up to 1173 K. In this case, the weight gain during oxidation in air decreases by a factor of 2. It has been established that the alloying of titanium aluminide by chromium enhances the heat resistance and fracture toughness of the coatings. A substantial increase in the hardness of the coatings as compared to that of detonation coatings based on γ-TiAl (11 GPa and 5 GPa, respectively) has been achieved. The increased working characteristics make it possible to use the Ti–Al–Cr intermetallic compound in the aerospace industry.

Resume : Thin films of Co2FeSi(111) were grown at 200˚C using molecular beam epitaxy on InAs(111) substrates and characterized by structural and magnetic methods. X-ray analysis showed that the films exhibit L21 structure, while pole figures along the [220] direction, showed a 30˚ in-plane rotation respect to the [220] direction of the InAs substrate. The magnetic moment with the value of 1040 ±60 emu/cm3 is in good agreement with the value of the bulk Co2FeSi at room temperature. On the other hand, weak uniaxial anisotropy in the film plane can indicate on the stress induced by the lattice constants mismatch between the film and the substrate. Overall, the results suggest that Co2FeSi can be used as a highly spin-polarized ferromagnetic spin injector and detector in InAs-based spintronic devices. K.Z. acknowledges support from Polish National Science Center Grant DEC-2014/15/B/ST3/02927.

Resume : Uniqe and often desired properties of both single- and multi-walled carbon nanotubes can be utilised in many ways. One strategy is based on use of individual nanoobjects in the fabrication of, e.g., nanotransistors, another approach employs properties of an assemblage of nanotubes which can form, e.g., a thin film or composite with other materials. In our work we focus on discrete nature of carbon nanotube thin films that implies intrinsic inhomogenity at the nanoscale. To study the thermal properties of single walled carbon nanotubes thin films we use microRaman spectroscopy, a contactless technique with spatial resolution below 1μm. Phonon energies, including their dependencies on the temperature or the laser power, which further enables calculation of the thermal conductivity or interface conductance are investigated in a statistical approach. We present useful methodology for proper handling the heating effects both from laser illumination and heating stage (zero laser power limit). We also demonstrate that the 2D phonon energy derivatives both in respect to the temperature χT or laser power χP have a gaussian distribution which does not originate in the uncertainty of a single measurement but in intrinsic inhomogenity of the sample. For instance, the mean value of χT, acquired from a 30μm x 30μm area, step 3μ, equals -0.036 cm-1/K and standard deviation is 0.0074 cm-1/K. At the end thermal conductivity and total interface conductance of semiconducting, metalic and mixed carbon nanotubes thin films are extracted using an partial differential equation systems.

Resume : Many diseases can be detected from presence of a special specie in a specified quantity of the human exhales. Therefore, sensing exhale gases can be a powerful method of disease diagnosis. For this purpose, field emission (FE) mechanism can be used in high accuracy exhale bio sensors. Recently, ZnO nanorods FE has attracted so much attention because of ZnO exclusive specifications. One of the most important factors in attaining a privileged FE performance from a nanorod array is the array?s resistance and its electron concentration. Thus, Cds nanoparticles deposited on the Aluminum-doped ZnO nanorods can absorb light and generate electron-hole pairs. The generated electron in the presence of light in the thin CdS layer will transfer to ZnO and will positively affect the FE properties. The standard CMOS processing on the glass substrate has been used for the sensor fabrication. 2% AL-doped ZnO sputtering has been used for the seed layer and the array of nanorods was in-situ doped using hydrothermal process. The quantum dots were epitaxially deposited using successive ionic layer adsorption and reaction (SILAR) at room temperature. The morphology of the grown arrays was controlled using top and cross-sectional field emission electron microscopy images. The crystalline quality of all doped samples was investigated using photoluminescence and x-ray diffraction. Finally, the IV curves and field emission responses were measured by Keithley-K361 parameter analyzer to estimate the impact of doping and presence of CdS nanolayer on the electrical response.

Resume : Bovine Serum Albumin (BSA) is highly water soluble and binds noncovalently with drugs or an inorganic material for the efficient drug delivery in various areas the affected body. Historically, albumin has been extensively applied as biodegradable anti-cancer drug charger because of its excellent biocompatibility and high stability in blood can accumulate in malignant or inflamed tissue. Due to the well defined structure of the protein, containing charged amino acids, the albumin nanoparticles may allow electrostatic adsorption molecules negatively or positively charged without the application of other compounds on the surface. Therefore significant amounts of drug can be incorporated within the particle, as a function of different albumin binding sites. In this work we study the synthesis of bovine serum albumin nanoparticles, by desolvation process, containing apocynin as the active agent. Apocynin acts to inhibit NADPH oxidase (NOX) and it has been used as one of the most promising drugs in experimental models of inflammatory and neurodegenerative diseases. Apocynin is a cheap substance and can be obtained commercially from various companies, which facilitates broad application of this phytochemical.To this end, in synthetic procedure, the pH synthesis (7.4 and 9.0) in order to evaluate the influence on the size and stability of the formed nanoparticles. The samples were analyzed using SEM, TEM, AFM, FTIR, UV-Vis and fluorescence. The results demonstrate the obtaining albumin nanoparticles interacting with apocynin but nevertheless failed to set only if they are adsorbed or encapsulated in the protein nanoparticles.

Resume : The thermal conductivity measured and reported by different investigators using transient hot-wire technique shows wide diversity, and the present paper reports for the first time that the container materials used for such measurements is one of the factors leading to this variation. Ultra-fine silver nanoparticles were prepared by a simple chemical reduction method. The as-prepared Ag nanoparticles were characterized by X-ray diffraction analysis, transmission electron microscopy, and fourier transform infrared spectroscopy. From the dynamic light scattering, it was found that the size of the Ag nanoparticles ranged from 6-30 nm, with an average size of 13 nm. Programmed ultrasonication has been carried out for the preparation of the aqueous silver nanofluid. This silver nanofluid was stable for more than a month at neutral pH. To check the distribution of silver nanoparticles in the aqueous silver nanofluid, atomic absorption spectroscopy has been carried out by carefully collecting a small amount of nanofluid samples from various locations in a stainless steel and a polypropylene container. A non-uniform distribution of Ag nanoparticles was observed when the nanofluid was in stainless steel container apparently due to the charge accumulation on the metallic surface, whereas in the polypropylene container the Ag nanoparticles in the nanofluid were found to be evenly distributed. The thermal conductivity of aqueous silver nanofluid in polypropylene and stainless steel containers at different locations have been measured by means of a needle like probe of the KD2 device. It has been observed that the thermal conductivity of silver nanofluid is high near to the stainless steel container wall and less at the centre of the container, whereas in the polypropylene container the conductivity is same everywhere. This novel phenomenon can be explained by the collision mediated model for thermal conductivity enhancement of nanofluids recently formulated by the present school. Their model points out that pulse-like rapid heat transfer in few pico seconds occur during frequent collision of the nanoparticles like Ag with the heat source in the course of the Brownian motion of particles in the nanofluids. This is followed by dissipation of the acquired heat by the nanoparticles to the surrounding fluid during their subsequent Brownian motion that would make a significant contribution to the thermal conductivity enhancement.

Resume : Nanostructured ultrathin bismuth films [1,2] have attracted a lot of interest as they reveal exotic functional properties that do not exist in bulk. The material properties are advantageous for the realization of e.g. spin based electronic devices, magnetoresistance effects and topological properties. Therefore nanosized Bi structures grown at different orientations have high potential for both fundamental research and technological applications. Especially growth on an atomically well defined insulating substrate, providing an infinite potential well barrier, is essential for future electronic applications as well as to get a deeper understanding of its controllability. In this study we demonstrate by Surface X-ray Diffraction (SXRD) the controlled growth of thin Bi(110) and Bi(111) films on such a substrate: atomically smooth insulating sapphire (α-Al2O3(0001)). The preparation of (110)-oriented Bi films, a rather exotic orientation, is a difficult task. At temperatures as low as 40K, we are able to slow down kinetics and thereby controlling the growth of Bi towards Bi(110), stable up to 400K. By annealing the Bi(110) films beyond, they can be transformed towards stable Bi(111) films. For films grown around RT, thin films grow in (110) orientation, followed by growth in (111) orientation. At elevated temperatures, Bi crystallizes in hexagonal (111) orientation on sapphire, having a lattice misfit of 4.6% similar as it does on a wide variety of other substrates [3-7]. * corresponding author: t.r.j.bollmann@utwente.nl References [1] E.I. Rogacheva, et al. Appl. Phys. Lett. 82, 2628 (2003). [2] Y.W. Wang, et al. Appl. Phys. Lett. 88, 143106 (2006). [3] H. Hattab, et al. Thin Solid Films 516, 8227 (2008). [4] M. Kammler, et al. Surface Science 576, 56 (2005). [5] F. Song, ACS Appl. Mater. Interfaces, 7, 8525 (2015). [6] G. Bian, et al. ACS Nano, 10, 3859 (2016). [7] M.-Y. Yao, et al. Scientific Reports 6, 21326 (2016).

Resume : Creating novel functionality utilizing abundant element is a major challenge in material research. 12CaO?7Al2O3(C12A7) with a crystal structure composed of 3D-connected sub-nanometer-sized cages entrapping oxygen ions as the counter anion is an insulator with a band gap of ~7eV. We have attempted to realize novel functionalities by replacing these oxygen ions with unconventional anions such as O-, H- and electron. C12A7:O- and C12A7:H- exhibit high oxidation power enough to oxidize Pt and light-induced insulator-electronic conductor conversion, respectively. The striking results were obtained for C12A7:e-, a first RT electride ; the conductivity at RT is changed from ~E-10 to E+3 Scm-1 and metal-superconductor transition occurs at low temperatures. The most unique property is its low work function of 2.4eV, comparable to metal potassium, but chemically stable. This property led to the finding of high performance catalyst for ammonia synthesis at ambient pressure when Ru nanoparticles are loaded on the surface of C12A7:e-. A series of finding on electro-active functionality in C12A7 demonstrated the power of nanostructure composed of abundant elements and may be regarded as a pioneering research of ?Element Strategy Initiative?, a Japan-original science and technology project. We expect the recent discovery of 2D-electride Ca2N and Y2C along with material design concept would open a new frontier. Recently, we have created amorphous C12A7:e thin films by sputtering. The resulting thin films are optically transparent but retain a low work function (~3.0eV). Such a unique properties meet the requirement for electron injection layers of inverted-type OLEDs. In this talk I show the recent advances in science and application of C12A7:e along with the background.

Resume : Within the last years several concepts were developed for creating environmentally friendly energy sources, such as photovoltaics, fuel cells, and photo-electrochemical cells, which are based on novel nanostructured morphologies and material combinations. For these energy conversion systems semiconducting oxide nanostructures are of great interest since they can be used as e.g. electrode materials or photocatalysts. The occurring interfaces and defects within the nanostructures are the key parameters which determine the functionality and limit charge carrier separation and charge transport. To improve the performance, the inorganic nanostructures can be modified by e.g. doping and/or by creating core-shell structures. Annealing treatments can be performed to minimize defects and to induce phase transformation leading to crystal modifications with a more suitable band gap. Two examples will be presented in this talk, Nb3O7(OH) [1] and TiO2 [2,3] nanowire arrays which can be applied as electrode material in dye sensitized hybrid solar cells and in light induced water-splitting devices. The nanostructures were synthesized hydrothermally. Different advanced transmission electron microscopy (TEM) techniques were applied to study the crystal structure, atomic arrangement, chemical composition, bonding behavior and band gap of the individual nanowires and networks on the atomic scale The results were correlated to the synthesis conditions and used to construct growth models. In addition, the functional properties of the Nb3O7(OH) and TiO2 nanostructures were measured in photo-electrochemical and dye sensitized hybrid solar cells. The properties like charge carrier mobility and lifetime were evaluated and further improved by using modified systems developed with the insights obtained by TEM [3]. [1] S. B. Betzler, A. Wisnet, B. Breitbach, C. Mitterbauer, J. Weickert, L. Schmidt-Mende, and C. Scheu, J. Mater. Chem. A, 2014, 2, 12005 [2] A. Wisnet, S. B. Betzler, R. V. Zucker, J. A. Dorman, P. Wagatha, S. Matich, E.Okunishi, L. Schmidt-Mende, and C. Scheu, Cryst. Growth & Design, 2014, 14(9), 4658. [3] A. Wisnet, K. Bader, S. B. Betzler, M. Handloser, J. Weickert, A. Hartschuh, L. Schmidt-Mende, C. Scheu, J. A. Dorman., Adv. Funct. Mater., 2015, 25, 2601. [4] The author would like to thank the colleagues and co-workers who contributed to this work and the German Research Foundation (DFG) for financial support.

Resume : Within the last years several concepts were developed for creating environmentally friendly energy sources, such as photovoltaics, fuel cells, and photo-electrochemical cells, which are based on novel nanostructured morphologies and material combinations. For these energy conversion systems semiconducting oxide nanostructures are of great interest since they can be used as e.g. electrode materials or photocatalysts. The occurring interfaces and defects within the nanostructures are the key parameters which determine the functionality and limit charge carrier separation and charge transport. To improve the performance, the inorganic nanostructures can be modified by e.g. doping and/or by creating core-shell structures. Annealing treatments can be performed to minimize defects and to induce phase transformation leading to crystal modifications with a more suitable band gap. Two examples will be presented in this talk, Nb3O7(OH) [1] and TiO2 [2,3] nanowire arrays which can be applied as electrode material in dye sensitized hybrid solar cells and in light induced water-splitting devices. The nanostructures were synthesized hydrothermally. Different advanced transmission electron microscopy (TEM) techniques were applied to study the crystal structure, atomic arrangement, chemical composition, bonding behavior and band gap of the individual nanowires and networks on the atomic scale The results were correlated to the synthesis conditions and used to construct growth models. In addition, the functional properties of the Nb3O7(OH) and TiO2 nanostructures were measured in photo-electrochemical and dye sensitized hybrid solar cells. The properties like charge carrier mobility and lifetime were evaluated and further improved by using modified systems developed with the insights obtained by TEM [3]. [1] S. B. Betzler, A. Wisnet, B. Breitbach, C. Mitterbauer, J. Weickert, L. Schmidt-Mende, and C. Scheu, J. Mater. Chem. A, 2014, 2, 12005 [2] A. Wisnet, S. B. Betzler, R. V. Zucker, J. A. Dorman, P. Wagatha, S. Matich, E.Okunishi, L. Schmidt-Mende, and C. Scheu, Cryst. Growth & Design, 2014, 14(9), 4658. [3] A. Wisnet, K. Bader, S. B. Betzler, M. Handloser, J. Weickert, A. Hartschuh, L. Schmidt-Mende, C. Scheu, J. A. Dorman., Adv. Funct. Mater., 2015, 25, 2601. [4] The author would like to thank the colleagues and co-workers who contributed to this work and the German Research Foundation (DFG) for financial support.

Resume : Perovskite oxides have received significant attention in recent years, in part due to their ability to generate very high density two-dimensional electron gases (2DEGs) at interfaces between polar and nonpolar materials [1]. Most of these complex oxides have degenerate conduction bands composed of transition-metal d states, leading to large effective masses and low mobilities, a detriment for electronic applications. BaSnO3 has emerged as an alternative: it crystallizes in the perovskite structure but its conduction band is nondegenerate and composed of Sn s states, resulting in high mobility, favorable for a transparent conductor. I will show how cutting-edge first-principles calculations shed light on the multiple aspects of this problem: band alignment and confinement of the 2DEG [1,2], mobility [3], and for applications requiring transparency, fundamental limits on absorption [4]. Work performed in collaboration with B. Himmetoglu, A. Janotti, E. Kioupakis, K. Krishnaswamy, and H. Peelaers, and supported by ONR, DOE, LEAST, and NSF. [1] L. Bjaalie, B. Himmetoglu, L. Weston, A. Janotti and C. G. Van de Walle, New J. Phys. 16, 025005 (2014). [2] K. Krishnaswamy, L. Bjaalie, B. Himmetoglu, A. Janotti, L. Gordon, and C. G. Van de Walle, Appl. Phys. Lett. 108, 083501 (2016). [3] B. Himmetoglu, A. Janotti, H. Peelaers, A. Alkauskas, and C. G. Van de Walle, Phys. Rev. B 90, 241204(R) (2014). [4] H. Peelaers, E. Kioupakis, and C.G. Van de Walle, Phys. Rev. B 92, 235201 (2015).

Resume : Catalytic and photocatalytic reactions are crucial in various transformations for different applications in Chemistry. However, most of the catalysts used for these reactions, based on homogeneous systems, are expensive, inefficient or need very high quantities of solvent resulting in non-sustainable systems. In this context, our work is focused on the synthesis, characterization and study of the catalytic properties of novel nanomaterials based on immobilized catalytic species such as metal complexes, metal nanoparticles or metal oxide nanoparticles on solid high-surface-area nanostructured materials. In addition, we are developing novel methods for the preparation of nanoparticles stabilized by protective agents that prevent aggregation and enhance the effectiveness and applicability of these heterogeneous systems in a wide variety of catalytic applications such as catalytic oxidation of benzyl alcohol, polymerization of polar monomers, C-C formation via Suzuki-Miyaura coupling reactions, photocatalytic degradation of contaminants in water under visible light and photocatalytic formation of hydrogen via methanol photoreforming. In this communication, the most recent results of our group will be described, emphasizing key factors such as the use of environmentally friendly reagents, utilization of ionic liquids, improvement of the recyclability of the catalytic nanosystems and improving their sustainability.

Resume : We present here the design and synthesis of organic-inorganic nanocomposite materials consisting of a molecularly imprinted polymer (MIP), for specific target recognition, and gold nanoparticles (GNP), for optical detection and photothermal heating, with potential applications in bioimaging and theranostics. MIPs are synthetic antibody mimics that specifically recognize molecular targets. They are highly cross-linked polymers made with functional monomers in the presence of the target molecule acting as template. This interaction renders three-dimensional binding sites in the polymer that are complementary to the template molecule in terms of size, shape, and chemical functionality. GNP display intense colorations in the visible spectrum that make them attractive as platforms for sensing. Their localized surface plasmon resonance (LSPR) is due to the interaction of the metal conduction electrons with light. GNP can be designed to absorb more light than scatter it, with any excess energy released as heat in the vicinity of their surface. We have used the heat generated by these GNP upon irradiation with light to initiate thermally-induced free-radical polymerizations around individual particles. This results in the red-shift and broadening of the LSPR, with polymer coatings that can develop into large networks when the irradiation is prolonged. This polymer shell can be used to modify the surface properties of the particle and for molecular recognition when the polymer is a MIP.

Resume : In this work, we present a novel integrated green synthesis of self-assembled mesoporous silicon-based sieves using a geothermal waste as silicon source. Hydrothermal synthesis was performed using both conventional heating and a coaxial antenna for in-situ microwaves (MW) irradiation . A series of surfactant-templated hexagonally-ordered mesoporous materials were successfully obtained avoiding the use of toxic reagents like alkoxides, colloidal or fumed silicas. All prepared materials exhibit hexagonal structure, narrow pore size distribution, high surface areas and were used as catalytic supports for a Zn active phase. The catalytic activity of these materials was evaluated in a fast and eco-friendly heterogeneous catalytic process to valorize glycerol into a glycerol carbonate using microwaves irradiation for thermal activation. The use of Zn/mesoporous silica derived from the cheap silicon waste precursor and the fast MW processing featured similar catalytic properties than those obtained using the mesoporous material synthesized through the traditional approach. The reaction conditions to yield glycerol carbonate via the urea route, such as temperature, reaction time, and the catalyst dosage were explored. The proposed MW assisted methodology resulted in a high glycerol conversion, high selectivity towards glycerol carbonate and short reaction processing. The synergy between the MW technology and the low cost of the heterogeneous catalyst in the integrated MW-assisted process leads to a promising, environmentally friendly, easily scalable-up and cheap approach to glycerol carbonate production.

Resume : In the following paper we will discuss in brief the results, which we obtained in our laboratory at CNR the last years, about the synthesis of metal nanoparticles (NPs), to be used in the sensing application. Here we make focus on Zinc NPs produced in an inert gas flushing in a quartz reactor (aerosol route) via an evaporation-condensation process. Afterwards, we cope the task of realize a prototype of pollutants gas sensor and compare the electrical responses of three zinc powders, at parity of constituting species, but with different shape and aggregate morphology, that are isolated primary or partially coalesced nanoparticles, aggregates and hollow nanofibers or nanotubes. All the three type of samples (isolated nanoparticles, aggregates and nanotubes) are subjected to a slight surface oxidation off line at 200 °C for one hour, in a way to form core-shell nanostructures with an external 50 Å thick layer of ZnO over the inner Zn core matter. Evidence is given about the fact that a sample constituted by Zn-ZnO nanotubes with about 400 Å diameter, produces an electrical response to the test gas NO2, which is 10^4 times the response of the bulk Zinc-ZnO. An explanation is proposed on the basis of Diffusion Reflectance Fourier Transformed Infra Red spectrometry (DRFTIR) of the same sample via the so-called Oxygen Pseudo-Defects theory.

Resume : We fabricated Ge-on-insulator (GOI) monocrystalline layers with thickness H = 1 – 18 nm using high quality heteroepitaxial growth and Ge layer transfer with epitaxial lift-off technique on fused SiO2 substrate. We study GOI Raman and optical reflection/transmission/absorption spectra. With a decrease in H, we observe electron-confinement-induced blue shift of L-point direct-band-gap absorption peak. Raman spectra display longitudinal optical (LO) phonon and low-frequency confined acoustic phonon bands. For H < 5 nm, additional very weak bands due to insignificant amorphous inclusions appear in the spectra. In accordance with the wave-vector-quantization theory, acoustic phonon frequencies show ~1/H dependence at H > 5 nm. However, for H < 5 nm, we observe deviation from the ~1/H law suggesting a change in GOI mechanical properties or a change from discrete to continuum mode Raman activity. For H > 12 nm, LO phonon Raman band shows slight broadening and upshift compared to bulk Ge. With a decrease in H, the band displays enhancement and downshift. Also as H decreases, the band homogeneously broadens proportionally to 1/H. We attribute these findings to a reduction in reflectance plus electron confinement, thickness-dependent stress (compressive for H > 12 nm and tensile for H < 12 nm) and surface-disorder-induced phonon lifetime reduction. Contrary to the Richter-Campbell-Fauchet optical phonon confinement model, wave-vector-relaxation-induced LO phonon Raman band asymmetric broadening is shown to be negligible. We also observe strong laser-induced GOI heating suggesting extremely low thermal conductivity.

Resume : Recently, ballistic heat transport has been demonstrated experimentally various nanostructures, but a practical use of this phenomenon remained challenging, as thermal phonons tend to travel in almost random directions. We used micro-TDTR experiments and Monte-Carlo (MC) simulations to show the in-plane ballistic heat transport with well-defined directionality in phononic nanostructures and a possibility to use this phenomenon for heat guiding and focusing. First, we studied heat transport in silicon thin films with aligned and staggered periodic arrays of holes, and demonstrated that significant difference in thermal conductance appears when the characteristic size of the structures becomes smaller than 100 nm. The difference in thermal conductance is attributed to ballistic phonon transport in the structures with the aligned lattice. Next, we demonstrated that these structures can be used to guide the phonons and act at a source of ballistic heat emission in solids. This emission was couples into nanowires, where the ballistic path of the phonons was continued, and corresponding nanowire length and temperature dependences were observed. Finally, we used this concept to create thermal lens nanostructures which can focus thermal energy in the focal point. Our theoretical and experimental results suggest that the created hot-spot is smaller than 200 nm in diameter, and thus can be used in biomedicine, thermoelectrics and wherever selective heating is required.

Resume : Recently we reported over a novel wet-processing method able to deliver in minutes nanofibers over large areas, effective on both polymers and carbon nanotubes, termed ASB-SANS (Auxiliary Solvent-Based-Sublimation Aided NanoStructuring) [A. Fraleoni Morgera, Small, 2011, 7, 321-325; A. Fraleoni Morgera et al., RSC Adv., 2013, 3, 15664–15669]. Here we show how it is possible to control the transition from continuous fibers to aligned dots simply changing the composition of the ternary solution (TS) on which ASB-SANS is based. A ternary diagram relating the various TS compositions and the resulting nanopatterns morphologies has been realized. The nanopatterns (fibers/aligned dots) width and inter-pattern distance variations have been analyzed with respect to the TS composition, showing consistency with currently accepted models for macromolecular chains mobility in a medium. In line with these observations, a tentative explanation of the mechanisms underlying the patterns formation is given.

Resume : Mesoporous films of nanocrystalline hematite (α-Fe2O3) show unique properties for applications as electrode material in the field of renewable energy research, e.g. as photoanode for electrochemical water splitting. The performance of iron oxide films in these applications is critically influenced by the material’s phase composition, crystallinity and porosity. We present a comprehensive investigation of the crystallization process of mesoporous ferrihydrite to hematite and deduce guidelines for improved structural control. Films of ferrihydrite on silicon were obtained via soft templating of mesopores with amphiphilic block-copolymer PEO-PB-PEO and iron nitrate as metal oxide precursor. The parameters of the subsequent thermal treatment were systematically varied in a wide range of conditions to assess the influence of temperature, time, gas atmosphere and humidity on the transformation. Physicochemical characterization techniques, particularly SEM, but also TEM, SAXS, SAED and XRD were applied to characterize the evolution of crystallinity, porosity and phase composition during the transformation. The present contribution investigates qualitatively and quantitatively the transformation of ferrihydrite to hematite by elucidating the nucleation rate of hematite, the nucleation mechanism and the activation energy of the phase transformation. Compared to bulk characterization methods we show the advantage of SEM characterization to investigate phase transformation on a nm scale.

Resume : Physical attributes of multicomponent materials of a given chemical composition are determined by atomic arrangement at property-relevant length scales. A potential route to access a vast array of atomic configurations for material property tuning is by synthesis of multicomponent thin films using vapor fluxes with their deposition pattern modulated in the sub-monolayer regime. However, the applicability of this route for creating new functional materials is impeded by the fact that a fundamental understanding of the combined effect of sub-monolayer flux modulation, kinetics and thermodynamics on atomic arrangement is not available in the literature. Here we present a research strategy and verify its viability for addressing the aforementioned gap in knowledge. This strategy encompasses thin film synthesis using a route that generates multi-atomic fluxes with sub-monolayer resolution and precision over a wide range of experimental conditions, deterministic growth simulations and nanoscale microstructural probes. Investigations are focused on structure formation within the archetype immiscible Ag-Cu binary system, revealing that atomic arrangement at different length scales is governed by the arrival pattern of the film forming species, in conjunction with diffusion of near-surface Ag atoms to encapsulate 3D Cu islands growing on 2D Ag layers. The knowledge generated and the methodology presented herein provides the scientific foundation for tailoring atomic arrangement and physical properties in a wide range of miscible and immiscible multinary systems.

Resume : Nanomechanical resonators (NMRs) are now considered as promising candidates for a number of applications, including sensors, filters, switches, and memory elements. The resonant excitation of mechanical vibrations in a beam is the main phenomenon used when developing such devices. Typically, a two-frequency resonance with the driving frequency close to the natural frequency of the beam is exploited. However, such excitation does not provide a convenient possibility for controlling the central frequency of the resonance, its linear dynamic range, and the critical value for the bistability onset what is, however, needed for the applications. Some approaches, like for example, bending of a nanoresonator beam or introducing a gate to control the beam vibrations electrostatically, have formerly been proposed to meet this demand. In this paper, we demonstrate that there is a relatively simple solution to this problem that is based on adding a low-frequency (LF) spectral component to the high-frequency (HF) drive. The beam geometric nonlinearity provides an interaction of these frequencies and a formation of three-frequency resonances. The parameters of these resonances are easily and reversibly controlled by varying the amplitude and the current of the LF driving. In particular, it is possible to increase essentially the linear dynamical range of the resonator by decreasing the current amplitude. This feature can be of interest for various sensor applications. An increase of this amplitude results in lowering the threshold for bistability with respect to the HF driving. This is obviously attractive for the development of memory elements. There are totally three resonances in a NMR with the discussed tandem driving. The distance between the resonances on the frequency scale is much larger than the width of the individual resonances. Hence, the resonances are well localized in the frequency domain, and they can be used (excited) individually or collectively. Practically, such single NMR is equivalent to three NMRs with harmonic driving. The central frequencies of the two- and three-frequency resonances are easily controlled in a wide range by varying the LF. We have considered, as an example, a NMR made of a doubly-clamped beam with magnetomotive driving. However, due to the generality of the mathematical model used, the obtained results are applicable to other types of resonators and are not only limited to the nanosize scale.