Seznam abstraktů 2016: POSTEROVÁ SEKCE A

Quantum dot supercrystals are periodically arranged two- or three-dimensional ensembles of semiconductor nanocrystals. These artificial materials represent a new type of condensed matter systems which properties depend on the individual features of building blocks as well as on many-body effects of their mutual interactions. In this work we suggest the method of calculation the energy spectrum of supercrystals' collective excitations. In particular, by calculating the excitonic spectra of nanocrystals assembled in two-dimensional Bravais lattices and we demonstrate the wide opportunities of design the optical properties of supercrystals by varying geometry and materials parameters of individual nanocrystals. The possibility of tuning the physical properties of quantum dot supercrystals enables the development of new photonics materials and devices.

Magnetotransport, optical, spin-dependent and topological properties of the composite InAs/GaSb/AlSb quantum wells (CQWs) based on the broken-gap heterojunctions are actively studied during two last decades as promising materials for new applications. We report on microwave radiation absorption and Shubnikov-de Haas (SdH) oscillation study in semimetal InAs/GaSb/AlSb CQWs at low temperatures of 2.7-20 K and in magnetic field H up to 14 kOe. Mid-infrared superlinear electroluminescence was observed in deep AlSb/InAsSb QWs [1]. Recently low temperature transport measurement of the invert InAs/GaSb/AlSb CQWs was studied. Hybridization gap and Quantum Spin Hall effect were observed by applying of the electric and magnetic field [2]. CQWs were grown by MOVPE on n-GaSb (100) substrates with various widths of InAs QWs (15 nm or 12.5 nm) and GaSb (10 nm or 8 nm) surrounded by AlSb barriers (30 nm) and GaSb cap layer (3 nm).
Method of EPR spectroscopy was used and derivate microwave power (dP/dH) was measured (f=10 GHz). Intensive oscillations were observed at H > 7-14 kOe. Temperature and orientation dependence of SdH oscillation amplitudes were recorded. 2D-electron concentration ns ≈ 2×1012 cm-2 was obtained from the filling factor dependence on inverse magnetic field. Cyclotron frequency and non-parabolicity of effective mass were evaluated (m*e=0.028 m0 and m*=0.0408 m0) for the samples with different QW widths. Unusual anisotropy of angular dependence of the oscillation amplitudes on orientation of CQW samples in magnetic field was observed in the angle range from 0° up to 180°. These results can be explained by an inversion asymmetry which is the feature of substances with lack of inversion center. REFERENCES: [1] M.P. Mikhailova, E.V. Ivanov, L.V. Danilov, K.V. Kalinina, N.D. Stoyanov, G.G. Zegrya, Yu.P. Yakovlev, E. Hulicius, A. Hospodková, J. Pangrác, M. Zíková, J. Appl. Phys. 112 (2012) 023108; [2] L. Du, I. Knez, G. Sullivan, R.R. Du, Robust Helical Edge Transport in Gated InAs/GaSb Bilayers, Phys. Rev. Let. 114 (2015) 096802. ACKNOWLEDGEMENTS: The authors acknowledge support from MPNS COST ACTION MP1204 - TERA-MIR Radiation: Materials, Generation, Detection and Applications and partly by RFFI grant project 15-02-03151, CSF project number 13-15286S, 16-11769S, 14-21285P and Infrastructural MSMT projects LM 2011 026 and NPU LO1603 - ASTRANIT.

Colloidal CdSe quantum dots (QDs) are in the lead position among other due to their optical properties. However, the bulk band gap of CdSe (1.74 eV) doesn’t allow effective emission of undoped QDs in the IR-range.
Our approach is to obtain highly-defective CdSe QDs, which have an intensive near-IR photoluminescence (PL) (ranging up to 0.9 eV) and high quantum yield (QY) (that exceeds the QY of undoped by more than two times). In our work we used colloidal method and silver halides (AgHal) were added during nanoparticles’ growth.
It was found that a little amount of AgHal leads to the tetrapods’ formation. And the further increase of AgHal amount in synthesis has led to the tetrapods’ destruction and the formation of large ellipsoidal nanoparticles (EPs). A threshold concentration of AgHal above which tetrapods fully disappear has been established.
Nowadays, it is known that halide-ions cause anisotropy of QDs, while silver-doped CdSe nanoparticles are unstable. An overlap between the two conditions allowed to obtain EPs, that have formed from tetrapods at high temperatures. EPs’ PL has two bands – exciton (with maximum ~1.8 eV) and a wide band in low-energy region (with maximum ~1.4 eV). The second band is associated with structure defects and has a long PL lifetime (9 microseconds at 1.3 eV), which could be useful for crating population inversion on this electron level.

The introduction of inorganic nanoparticles into a polymer matrix allows to obtain new hybrid nanomaterials with unique mechanical, thermal and electrical properties, which may possess advanced properties in comparison with conventional materials. In particular, the addition of spherical nanoparticles of silicon dioxide into cheap epoxy optically transparent polymers results in improved thermal properties (high values of glass transition temperatures, Tg and low values of coefficient termal expansion, CTE), suitable for use as matrices for LCD displays. Until now spherical silica nanoparticles were used to improve thermal properties of epoxy polymers, however, we believe that the greater influence of nanoparticles on the Tg is to be expected with the introduction of particles of elongated shape. Elongated nanoparticles have the largest surface compared to the spherical ones of the same volume. This leads to the fact that at equal volume fraction of the particles in the nanocomposite on their surface can contain the largest number of functional groups having strong intermolecular interaction (dipole-dipole interactions, hydrogen and covalent bonds). This should lead to the greatest increase in Tg of nanocomposites and the largest decrease in CTE. In the framework of this project it is planned to develop a method for theoretical evaluation of Tg and CTE of nanocomposites by the method of anharmonic oscillators, taking into account the chemical structure of the polymer matrix and functional groups on the surface of nanoparticles, the interaction strength between nanoparticles and polymer matrix, the size and content of nanoparticles. On the basis of the evaluation will be experimentally obtained optically transparent nanocomposites epoxy / silicon dioxide with a glass transition temperature of 50-70 ° C higher than Tg of epoxy polymer.

Conducting polymers are characterized by π-conjugated structure allowing the conduction of electrical current. Two main representatives – polyaniline (PANI) and polypyrrole (PPYR) – attract the attention of scientists for many years and various applications including anti-corrosive coatings or sensors were developed. Further improvement of electrical properties can be achieved by preparation of nanocomposites combining conducting polymers and layered materials. Natural clay minerals are very suitable for this purpose.
Ghassoul, a stevensite-rich clay mined in the only known deposit in the world, Jbel Ghassoul in Morocco, is studied by Moroccan, French and Spanish materials scientist for a relatively short time (about twenty years). It was found to be excellent adsorbent for various organic and metal cations as well as promising precursor for cordierite ceramics. Nanotechnology centre in VŠB-TU Ostrava is the first Czech scientific institute where the ghassoul is studied.
Present work is focused on preparation and characterization of PPYR/ghassoul and PANI/ghassoul nanocomposites. The nanocomposites in powder form were obtained by polymerization of pyrrole and anilinium sulfate, respectively, in aqueous suspension of ghassoul. For the preparation of PPYR, two oxidizing agents (ammonium peroxydisulfate and ferric chloride) were tested and compared. Nanocomposites were characterized using XRD, Raman spectroscopy, SEM, and conductivity measurements. Enhanced electrical conductivity of nanocomposites in comparison with pure PPYR and PANI was found. Tablets pressed from PPYR/ghassoul exhibit significant electrical anisotropy: conductivity in direction parallel to the tablet’s plane is ~580× higher than conductivity in direction perpendicular to the tablet’s plane. Possible application of tablets as load sensors was tested.

The improvement of hydrogen storage properties of ball-milled Mg-Al-Ti-Zr-C composite was studied in this paper. It has been previously shown, that the addition of Ti, Zr, Al and C improves storage properties of Mg. This beneficial effect of additives upon hydrogen storage properties can be explained by catalysis by the nanoparticles rich in Ti, Zr or Al located on the surface of Mg grains. They provide effective pathways for the hydrogen diffusion into the MgH2. The morphological and microstructural characteristics were investigated by scanning electron microscope Tescan Lyra 3 and by X-ray diffraction. The hydrogen sorption was measured by Sieverts method using Setaram PCT-Pro device.
Studied experimental composite absorbed 4.45 wt.% H2 at 623 K and 1.7 wt.% H2 at 473K within 10 min. The hydrogen storage capacity of the composite was about 4.7% wt.% H2 and 4.2% wt.% H2 at 673K and 473K, respectively.

During the last years constantly increasing demands of modern society to products made from renewable and sustainable resources that are biodegradable, non-petroleum based, carbon neutral, and have low environmental, animal/human health and safety risks .Cellulose is almost inexhaustible source of raw material. It is the world’s most abundant polymer, comprising at least one-third of all biomass matter. Through deconstruction of cellulose hierarchical structure can be extracted highly crystalline cellulose nanocrystals (CNC) with impressive properties. However, the main barrier in the processing of the nanocomposites based on CNC is their inhomogeneous dispersion and distribution in the non-polar polymer matrix. There is strong tendency of CNC to agglomerate and form interconnected networks due to omnipresence of hydroxyl groups on surface and formation of additional hydrogen bonds between nanoparticles. In this paper is this problem addressed by use of novel hydrophobic lignin coated CNC as a biobased nucleation agents in poly (lactic acid) (PLA) nanocomposites. These green nanocomposites based on natural plant derived substances have enormous potential to replace materials originated from non-renewable resources and show promise of providing degradation back into the environment when they are no longer needed. Resulted composites prepared by twin screw extrusion and injection moulding were characterized by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical testing and thermogravimetric analysis (TGA).

We present a combined experimental and theoretical study aimed on the properties of surfaces of 2D materials. We calculated the surface energy of several solid surfaces using high-level quantum mechanical method, the random phase approximation. For fluorographene, we corroborated theoretical result experimentally by using the inverse gas chromatography to estimate the surface energy. Then we studied the behavior of small organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate, hexane, and toluene) on the surfaces of graphene, graphite and fluorographene. We measured the isosteric adsorption enthalpies and entropies by inverse gas chromatography for large interval of coverages. Accurate experimental enthalpies in combination with theoretical modeling enabled us to indentify several phenomena related to surface adsorption: the adsorption enthalpies at low coverage (less than 2%) were influenced by the presence of high-energy sites in graphene and graphite, and the clustering of ethanol molecules on graphene and graphite altered the measured adsorption enthalpies at high coverage. Theoretical calculations were able to explain and accurately quantify the differences among the molecules and their adsorption behavior. REFERENCES: Lazar P, Karlický F, Jurečka P, et al. J. Am. Chem. Soc., 135, 6372-6377, 2013; Lazar P, Otyepková E, Banas P, et al. Carbon, 73, 448-453, 2014; Karlický F, Otyepková E, Banáš P, Lazar P. et al. J. Phys. Chem. C, 119, 20535-20543, 2015; Lazar P, Otyepková E, Karlický F et al. Carbon, 94, 804-809, 2015; Lazar P, Otyepka M, Phys. Rev. B 91, 115402, 2015.

Recently, conductive polymer polyaniline (PANI) attracted much scientific and technological interest because of the simple synthesis, environmental stability and high conductivity. All these properties predispose PANI to many practical applications, such as corrosion inhibitors, membranes, antistatic coatings, microelectronical devices, and wide scale of various sensors. In addition to graphite, diamond, and fullerenes, carbon nanotubes (CNT) represent another type of the well-known organized carbon structure. Nowadays, researchers have an interest in the combination of CNT with conducting polymers, especially PANI, because of the synergic effect arising from the combination of these components.
Present study deals with characterization of electrical conductivity and structure of PANI and CNT/PANI nanocomposites, where CNT were used as filler in PANI matrix. The effect of low amount of CNT (0.8, 2.0, and 3.6 wt.%) on conductivity has been investigated. CNT/PANI nanocomposites in powder form have been prepared using simple one-step process by the oxidative polymerization of anilinium sulfate with ammonium peroxydisulfate in aqueous suspension of CNT at room temperature. Electrical properties of the samples in powder form and in the form of pressed pellets were studied. Anisotropic conductivity has been achieved for all CNT/PANI pellets and decrease in conductivity was found for sample with content of CNT exceeding 2.0 wt.%. Structure and properties of samples have been investigated using combination of X-ray powder diffraction, Raman spectroscopy and scanning electron microscope analysis.

Adsorption using activate carbon (powdered or granular) is widely used for dye removal from wastewaters. However, it's very expensive because it need regeneration and reactive procedure. In this way our study is focused on characterisation, analysis and application of activated carbon issued from the cryogenic grinding of olive stones.
The first part concerns the determination of the characteristics of activated carbons obtained from the olive stones which were reduced to small grounds by using a cryogenic grinding with liquid nitrogen. Chemical activation of this precursor at 450 °C was adopted by using the phosphoric acid as dehydration agent at 2/1 impregnation ratio. FTIR was carried out to identify the surface groups. The microscopic structure and surface were examined by a SEM/EDX and BET respectively. Results showed surface area and pore volume approaching 1000 m2/g and 1 cm3 respectively. The SEM imaging shows a microcrystalline structure and a highly developed porosity.
In the second part we investigate the feasibility of adsorption of Methylene Blue on the activated carbon prepared from olive stones. The stock solution was prepared by dissolving Methylene Blue in 1000 ml distilled water. The experiments were carried out at ambient temperature, with the initial concentration varying from 5–50 mg/l. The absorbance of dye solution was determined by a spectrophotometer at 665 nm wavelength. The amounts of dye adsorbed were calculated from the concentrations in solutions before and after adsorption.
Activated carbon issued from the cryogenic grinding of the olive stones seems to be a promising adsorbent for removal of the cationic dye Methylene Blue from water. Indeed, 5 g of adsorbent could almost completely decolorize solution of Methylene Blue (50 mg/l).

Carbon-based nanolayers have attracted much attention due to their excellent low-friction properties, their high hardness and their good wear resistance. In this work, we present the results of material tests aimed at reducing the friction of the functional surfaces of titanium implants and thus extending their lifetime to reoperation. Nitrogen ion beam assisted deposition of a carbon-based nanolayer was applied to modify the surface properties (i.e. sliding and wear) of Ti6Al4V biomedical titanium alloy. Ion bombardment caused structural changes, leading to an increase in surface hardness by a factor of 1.86 in comparison with the surface modified by a carbon nanolayer without nitrogen ion bombardment. An analysis of the chemical composition showed that the modified surface is composed of a carbon-based nanolayer, a mixed interface and a nitrogen-enriched sublayer. Raman spectroscopy showed the DLC character of the carbon-based nanolayer with sp2 rich bonds. The TiN compound in the modified surface area was detected by X-ray diffraction. A very low friction coefficient below 0.1 was maintained at a normal load of 2N. The sliding behavior of the head (Ti6Al4V) and the shell (PEEK), tested on a wear joint simulator, showed that this surface modification of the head of the implant under optimized deposition conditions provides protection for the functional surfaces, resulting in reduced wear and a substantial increase in the lifetime.

In recent years, research with chemically synthesized graphene quantum dots and functionalized graphene quantum dots have seen a boom in multiple fields of materials science such as optoelectronics, bio-imaging, catalytic, fuel cell applications and so on due to its tunable properties. In this work, specific focus has been given to understand the tunable luminescence behavior chemically synthesized amino functionalized graphene quantum dots along with the exploration of its magnetotransport behavior at room temperature under weak magnetic field regime. We find very interesting excitation dependent fingerprint PL emission from blue to green which is believe is a direct consequence of band to band and interstate transitions that occur within its band gap and find a suitable energy band model to explain this behavior through further confirmation from ab-initio based first principle analysis with ab initio results suggesting formation of an interband state as a manifestation of p orbital hybridization between C–N atoms at the edge sites. Equally intriguing features could be found when magnetotransport measurements are conducted at room temperature in weak field regime. We find positive colossal magnetoresistance (MR) and its suppression, which is a manifestation of weak anti-localization phenomenon where competitive valley (inter and intra) dependent scattering takes place at room temperature under low magnetic field; analogous to low mobility disordered graphene samples. Furthermore, ab-initio analysis shows that sub-lattice sensitive spin-polarized ground state exists in the GQD as a result of pz orbital asymmetry in GQD carbon atoms with amino functional groups. This spin polarized ground state is believed to help the weak anti-localization dependent magneto transport by generating more disorder and strain in a GQD lattice under applied magnetic field and lays the premise for future graphene quantum dot based spintronic applications. This opens up new exciting possibilities in the domain of functionalized GQD dependent magnetotranpsort and spintronics for practical device applications previously not considered before along with its superlative optical and catalytic properties.

Doping graphene with heteroatoms opens a doorway to tailor electronic properties of this material towards its potential applications in spintronics and optoelectronics. One major challenge in this respect is to develop magnetic graphene with spin-polarized conductive behavior. Here, we report on combined experimental and theoretical investigations1 of the graphitic substitution of carbon atoms with sulfur in the graphene lattice. Graphene doped with 4.2 at% of sulfur shows strong ferromagnetic properties below ≈62 K with a saturation magnetization reaching ≈5.5 emu g−1, which is among the highest values reported so far for any graphene-based system. Atomistic modeling indicates that in a narrow concentration window (4-6 at%) magnetic interactions mediated by the π-electron system emerges between the substitution-generated paramagnetic centers leading to a ferromagnetic regime. The theory shows that the gamma-thiothiapyrone motif of sulfur in the graphene lattice is responsible for observed magnetic ordering at low temperatures. Furthermore, the theory predicts that the observed magnetic behavior is solely due to a substitution mechanism, as the addition of sulfur atoms on-top of graphene cannot promote a self-sustainable magnetism. The magnetically ordered S-doped graphene with a prominent saturation magnetization and coercivity offers viable highly conductive material, which, if further functionalized, would display strengthened self-sustainable magnetism against thermal fluctuations with a huge potential in spintronics and other magnetic applications. REFERENCES: [1] Tuček J, Błoński P, Sofer Z, Šimek P, Petr M, Pumera M, Otyepka M, Zbořil R, Sulfur Doping Induces Strong Ferromagnetic Ordering in Graphene: Effect of Concentration and Substitution Mechanism, Advanced Materials 2016. DOI: 10.1002/adma.201600939.

Bulk graphitic carbon nitride (g-C3N4) was prepared by heating of melamine at 600 oC for 2 hours. Thermogravimetric analysis showed that this temperature is optimal for the preparation of g-C3N4 without unnecessary loss of material. The structure and morphology characterization of bulk g-C3N4 was performed by X-ray diffraction (XRD) and scanning and transmission electron microscopy. Specific surface area (SSA) of bulk g-C3N4 obtained by the BET method was about 23 m2g-1. In order to increase the SSA bulk g-C3N4 was exfoliated into nanosheets by heating at 500 oC for 4 hours and by ultrasonication in an aqueous dispersion for 1 hour. The SSA increased at 157 m2g-1 by the heating and at 54 m2g-1 by ultrasonication. XRD revealed the layered structure of bulk-C3N4 as well as of both exfoliated g-C3N4 samples. ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation (project No. 16-10527S) and by VŠB-Technical University of Ostrava (projects No. SP2016/77 and SP2016/62).

The graphitic carbon nitride (g-C3N4) samples were prepared by the three different methods: (i) heating of melamine at 600 ºC (bulk g-C3N4), (ii) exfoliation of bulk g-C3N4 by heating at 500 ºC (Ex500) and (iii) exfoliation of bulk g-C3N4 by ultrasonication in an aqueous dispersion (ExUltra). The exfoliation was performed to obtain g-C3N4 nanosheets or other nanostructures. The samples characterization was performed by UV-Vis diffuse reflectance (DRS UV-Vis), photoluminescence (PL) spectroscopy and photoelectrochemical (PEC) measurement. The smallest transition energies Et was evaluated for bulk g-C3N4 (Et = 2.84 eV). The exfoliation by heating and ultrasonication caused both increase of transition energies Et at 3.07 eV and blue-shift and intensity increase of PL emission bands. The exfoliation by heating at 500 ºC increased photocurrent in comparison with the bulk g-C3N4 and ultrasonicated samples. This indicates the beneficial effect of the exfoliation by heating for various photocatalytic applications due to the higher mobility and separation efficiency of photo-induced carriers. ACKNOWLEDGEMENTS: This work was supported by the Czech Science Foundation (project No. 16-10527S) and by VŠB-Technical University of Ostrava (projects No. SP2016/77 and SP2016/62). This work was financially supported by EU structural funding Operational Programme Research and Development for Innovation project No. CZ.1.05/2.1.00/19.0388.

Metallic and bimetallic nanoparticles have fascinated researchers and scientists for over a century and are now heavily utilized in every field of research and technology. Colloidal metal nanoparticles are of interest in both research and technology, due to their specific properties not available in isolated molecules or bulk metals. Intensive research is searching for high efficiency solar cells with low-cost fabrication. The main problem for solar cell is relatively low efficiency of absorption of solar light. The optical properties of metallic Fe nanoparticles (NPs), Ni NPs and bimetallic Fe/Ni NPs produced under radiolysis in anaerobic condition based on chemical reduction in the presence of oxygen and quercetin in reversed micellar solutions and electrokinetic properties of nanoparticles carbon based nanocomposits were studied. The possibility of the preparation of coating using different nanocomposites with anomalous electrocatalytic is addressed. Optical absorption spectra of the initial solutions and the samples after synthesis of NPs were recorded using spectrophotometer "Hitachi U-3310" and comparison of current-voltage characteristics of NP Fe, NP Ni and bimetallic NP Fe / Ni are measured on a disposable "planar" electrodes in aqueous 0.5 M solution of H2SO4 using a potentiostat IPC-Pro MF. The findings that were presented in this paper suggest that the modification of carbon based nanocomposites coated with metallic and bimetallic nanoparticles of nickel and iron increases the efficiency of absorption of solar light and the electrocatalytic property of anode for a dye-sensitized solar cell (DSSC).

This study is aimed on the controllable reduction of the graphene oxide (GO) sheets during surface initiated atom transfer radical polymerization (SI-ATRP). GO sheets were successfully synthesized using Hummers method and properly characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA). SI-ATRP approach was used to simultaneously modified the GO surface by poly(butyl acrylate) (PBA) brushes and its reduction in the single-step synthesis. The presence of the polymer brushes on the GO sheets was investigated by gel permeation chromatography, nuclear magnetic resonance and FTIR. Simultaneous GO reduction during polymerization was confirmed using TGA, Raman spectroscopy and finally by conductivity measurement. Compatibility of the GO and GO-PBA sheets with silicone oil or elastomer was investigated via sessile drop contact angle measurements. From the potential applicability point of view, the modification of graphene-based hybrids by polymers is highly important especially when the compatibility as well as conductivity of GO-PBA sheets with surroundings plays an crucial role i.e. the light-stimulated sensors based on silicon or other elastomers.

Because of the unique electronic properties, the freestanding graphene nanoribbons are intensively investigated in the last few years. The potential application extends to gas sensors, field effect transistors, spintronics, plasmonics and more. Until recently, there was no possibility to inexpensively produce such structures. By exploiting of the different crystallographic planes of SiC a promising method which may be used to produce freestanding graphene was enabled. In this study we present calculation of molecular mechanics and electronic transport properties of epitaxially grown graphene on step-shaped SiC substrate. We analyzed the effects of hydrogenization of the SiC surface and conducted a series of calculations adressing the shape of the resulting freestanding graphene layer. Finally, we calculated transmission spectrum and I/V curve of the structure.

Two allotropes of C, the sp2-bonded two-dimensional graphene and sp3-bonded three-dimensional diamond exhibit very different electronic properties in their extremities. Our interest is focused on the interactions at the diamond-graphene interface, when graphene, a semimetal owning an excellent charge carrier mobility of 10^5 cm^2/(Vs), is brought into closest proximity of diamond, an insulator with an electron energy gap of 5.5 eV. In the present work, the growth of graphene on diamond via a catalytic transformation of the top diamond layers using scanning electron microscopy, atomic force microscopy and Raman spectroscopy, is studied.
Nanocrystalline diamond films (grain size ~ 200 nm) grown on Si substrates are coated with thin Ni layers of different thicknesses (ranging from 20 to 70 nm) by magnetron sputter deposition. When deposited at room temperature, almost all nanocrystals are individually covered by Ni islands. It is concluded that the nanocrystals are strong nucleation sites for the formation of Ni surface layers. The Ni islands do not intergrow since small gaps of a few nm in width are observed between them. Several layers of graphene were observed on the surface of the diamond nanocrystals after heating to 900°C under a forming gas atmosphere and chemical removal of Ni. However, the originally smooth facets of the diamond nanocrystals show grooves with a size of several of tens of nm. This indicates an inhomogeneous etching by a solid-solution reaction of C with Ni. For a better understanding of this process, the surface morphology after each step is analysed.

We report an informative strategy to both stabilize and electronically modify reduced graphene oxide (rGO) with electron-accepting capping agents [e.g., poly-(diallyldimethylammonium chloride) (PDDA), cetyltrimethylammonium chloride (CTAC), and poly-(allylamine hydrochloride) (PAA)] in carbocatalysis. The surface-modified rGOs with these positively-charged organic molecules possessing an intramolecular charge-transfer capability were directly applied to metal-free reductions of 4-nitrophenol and ferricyanide. The functionalization of the rGO surface with these capping agents influenced the overall reduction kinetics by controlling the induction time, enhancing the catalytic activity, and changing the reaction order compared to the reduction kinetics of bare rGO and GO. As the reaction kinetics were highly related to the way the capping agents were functionalized on rGO, our simple modification approach can pave the way to rationally designing rGO-based non-metallic catalysts.

Recently, graphene oxide (GO) has gained significant attention in many applications, such as touch displays, electronic devices or electrorheological fluids. However, neat GO is hydrophilic, which limits its efficiency in hydrophobic media, e.g. polymer matrices, oil carriers. Therefore, the utilization of GO–coated core–shell structures was proven to be advantageous. In this study, GO sheets were prepared by chemical exfoliation of graphite using modified Hummers method. The specific ATRP initiator, bromoisobutyryl bromide, was covalently immobilized onto as–prepared GO through oxygen–functional hydrophilic groups. Initiator–treated GO sheets were further grafted with poly(methyl methacrylate) (PMMA) via surface–initiated ATRP technique. The molar mass and polydispersity of PMMA chains were investigated using gel permeation chromatography and nuclear magnetic resonance, respectively. The successful grafting process was confirmed by Raman spectroscopy and thermogravimetric analysis. Synthesized GO/PMMA structures exhibited considerably enhanced wettability in hydrophobic media, which was revealed from surface–energy measurements. Therefore, the synthesized GO/PMMA hybrids may found utilization in many aforementioned practical applications providing well–dispersed composite systems.

In this work possibilities of the synthesis of two-dimensional graphene nanosheets in gas phase was studied.
We used microwave plasma torch discharge (2.45 GHz, 210 W) operating at atmospheric pressure conditions to synthesize carbon nanosheets with rectangular shape and typical size of hundreds of nanometers. The torch discharge was ignited in argon flowing through the central channel of the nozzle. Liquid ethanol, whose vapours were led to the discharge by carrier gas - argon, was selected as a precursor. The mixture of ethanol vapour, argon and oxygen or hydrogen was introduced to the discharge through outer channel of the nozzle. Decomposition of ethanol vapours, at specific deposition conditions, led to the synthesis of graphene nanosheets. The synthesized material was collected on the silicon substrate placed in the sample holder situated few centimeters over the discharge. The influence of different amount of oxygen or hydrogen in the gas mixture on the properties of synthesised graphene nanosheets was investigated. Such prepared samples were analysed by scanning electron microscopy, Raman spectroscopy and energy-dispersive X-ray spectroscopy (EDX). The discharge was examined using optical emission spectroscopy.

The report presents the results of the characteristics of the formation of structure in a self-propagating high-temperature synthesis of powders of intermetallic alloys with carbon nanostructures.

The interest in ZnO (zinc oxide) nanoparticles is increasing due to low cost of their processing as well as the ability of fabricating ZnO nanostructures with controllable morphology such as size, shape and orientation. Our method of choice of the preparation of the nanostructured thin ZnO layers is the hydrothermal growth of ZnO nanorods on glass substrates coated by the nucleation layer deposited by the reactive magnetron sputtering. We have developed and optimized conditions of the thin layer growth with controllable dimensions of nanorods followed by the ultrasound peeling (power, frequency, time). The colloid of ZnO nanorods was characterized by measuring the size of particles, zeta potential and photoluminescence. ACKNOWLEDGEMENTS: We acknowledge the CSF project 16-10429J and the SAS project KONNECT 007.

Thanks to their outstanding optical and magnetic properties, accompanied by their low toxicity, nanodiamonds (NDs) are highly promising class of carbon materials for diverse sensing bioapplications. Concurrently, stimuli-responsive polymeric brushes are a common platform for various biosensors construction [1]. Depending on their exact composition, these polymers respond to pH, temperature, ionic strength or other changes in environment by swelling or collapsing their structure. Here we present preparation and properties of a novel core-shell particles formed from ND core and a modifiable responsive polymeric shell while combining perspectives of both. NDs used in our work are prepared under high pressure-high temperature (HPHT) conditions, transformed to fluorescent NDs, coated by a thin silica shell [2] and finally a four-component responsive co-polymer is grafted from the silica surface. These complex particles swell with increasing pH and lowering temperature. Various molecules can be easily attached via click chemistry which makes these nanosystems a promising platform for a novel type of sensors based on influencing diamond core physical properties by varying distance of attached structures. REFERENCES: [1] Cabane, E. et al., Biointerphases, 2012, 7(1), 9.; [2] Rehor, I. et al., ChemPlusChem, 2014, 79 (1), 21-24.

The elements of the fourth column of Mendeleyev's periodic table of elements have been systematically investigated in the long term in relation to the optimization of thin film structures for efficient conversion of solar energy into electrical energy. Various forms of the elements Si and Ge, e.g. Ge NPs formation of crystalline Si are specially studied for other optoelectronic uses. The aim of our work is to reveal the mechanism of formation of Ge NPs on the surface of the hydrogenated silicon. A thin layer of a-Si: H was deposited on a P type nano-diamond thin films by PECVD, deposition of Ge was performed by molecular beam epitaxy (MBE) at substrate temperatures from 300 to 450 ° C. The resulting self - forming Ge NPs was tested by Raman spectroscopy, SEM, TEM and AFM. The work was financially supported by the project KONNECT 007 of the Czech Academy of Sciences and the projects 13-12386S and 13-31783S of Czech Science Foundation.

The Density Functional study on Hydrogen Adsorption on Silicon Carbide Nanosheet has been investigated. All calculations have been performed with density functional theory (DFT) , within the plane-wave pseudopotential approach as implemented in the Quantum ESPRESSO Simulation Package. The Perdew-Burke-Erenzerhof (PBE) formulation of the generalized gradient approximation (GGA) was employed to describe the exchange and correlation energies. we've tried different positions for hydrogen adsorption after simulating our honeycomb nanosheet of SiC. Four different positions of adsorptions are considered in the survey and it is finally shown that the most stable state happens when hydrogen atoms are adsorbed on silicon and carbon atoms at the two opposite sides of silicon carbide nanosheet. This adsorption have made some changes in the atoms positions so that the nano sheet didn't remain flat any more. The results have shown that this structure was the most stable one among those four. Silicon carbide is a semiconductor with a wide band gap about 2.5851 eV. After the hydrogen adsorption, the hydrogenated silicon carbide nano sheet have has a band gap about 3.9499 eV, which is much more than the band gap in the pure structure.

Light-sensitive polymer materials with embedded chromone dyes may be promising candidates for multi-layer fluorescent disks for storage of archival information. The recording is based on two-photon-induced phototransformation and the signal readout is due to single-photon-induced luminescence. The stability of fluorescent chromone compounds upon readout irradiation was studied and local quantum yields of luminescence and phototransformations were measured using the LSM710 confocal laser scanning microscope (Carl Zeiss) in order to estimate the material efficiency.

The magnetic and electrical properties of the nanostructured ZnO films are affected by the non-random dopant distribution due to segregation at grain boundaries, extended defects or interfaces. In order to control these properties it is essential to determine the distribution and localisation of the incorporated dopant ions. We have recently shown [1] that the electron paramagnetic resonance (EPR) spectroscopy provides a relatively simple, statistically relevant and non-destructive method for the quantitative evaluation of the distribution of the paramagnetic ions in nanostructured films.
We present here the results of the investigation of two ZnO films doped with different Mn concentrations, deposited by the sol-gel technique on Si substrates. Elemental energy X-ray spectroscopy (EDS) mapping in Scanning Transmission Electron Microscopy (STEM) and EPR demonstrate that Mn2+ ions in the 0.1 at% Mn doped ZnO film are localized at isolated tetrahedrally coordinated Zn2+ sites in both crystalline ZnO nano-grains and surrounding disordered ZnO, as well as at six-fold coordinated sites in the inter-grain region, while in the 5 at% Mn doped ZnO film the Mn2+ dopant was found in isolated sites, the main amount being aggregated in a secondary phase as an insular-like distribution between the ZnO nano-grains. The Mn2+ ions distribution has changed after annealing at 600° C, reflected by the increase of the ZnO crystallization degree [2]. REFERENCES: [1] D. Ghica, M. Stefan, C. Ghica, G. E. Stan, ACS Appl. Mater. Interfaces 6,14231 (2014); [2] M. Stefan, D. Ghica, S. V. Nistor, A. V. Maraloiu, R. Plugaru; Applied Surface Science; (2016); 10.1016/j.apsusc.2016.02.167. ACKNOWLEDGEMENTS: Financial support from CNCS-UEFISCDI under the Project PN-II-RU-TE-2014-4-0939 is gratefully acknowledged.

The nitrides of AIII group wide band-gap semiconductors represent a family of materials with a huge application potential in current micro- and opto- electronics. AlN is a very prospective substrate material for AIIIN semiconductor growth. The AlN growth was performed in horizontal RF heated MOVPE reactor using trimethylaluminium (TMAl) and ammonia. The influence of V/III ratio, deposition temperature and carrier gas composition on the structure and morphology of the layer were investigated. A significant effect of V/III ratio on layer structure and morphology was observed. High V/III ratio led to deterioration of surface morphology due to the pre-reaction of precursors in the gas phase. A positive effect of high nitrogen concentration in the carrier gas on the surface morphology was observed. No differences were observed for the layers deposited with and without low temperature AlN buffer layer. The growth epitaxial layers were characterized by X-ray diffraction, Raman spectroscopy, reflectance spectroscopy and atomic force microscopy.

Tin dioxide (SnO2) is an important n-type semiconductor with a wide band gap (Eg = 3.6 eV). Due to uniqe physical properties (like high surface to volume ratio) nanostructured stannic oxide are mostly useful in gas sensors and electrooptical devices [1]. A very promising strategy for fabrication of nanoporous tin oxide layers is simple anodic oxidation (anodization) of metallic substrate [2-4].
The main problem which limits potential applications of such kind of anodic films is their relatively poor mechanical stability being a result of the presence of cracks in the internal structure. In addition, in some cases structures with completely closed pores with much lower active surface area are obtained [2]. Some recent papiers report that nanostructured anodic tin oxide layers can exhibit quite good photo- electrochemical activity [3,4].
Here, we present some results on anodic formation of crack–free nanoporous tin oxide layers by anodic oxidation in alkaline electrolytes at various anodizing conditions. As obtained structures were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). A special emphasis is focused on the influence of various anodization conditions (e.g. the value of applied potential) on photoelectrochemical activity of such kind of materials. The dependences between photocurrent density, incident light wavelength and electrode potential were recorded for all obtained samples. Optical band gap energies were also calculated for all studied materials.
ACKNOWLEDGEMENTS: This work was partially supported by National Science Centre, Poland (2014/13/D/ST5/02750).
REFERENCES: [1] LUO S., CHU P.K., LIU W., ZHANG M., LIN C. Origin of low-temperature photoluminescence from SnO2 nanowires fabricated by thermal evaporation and annealed in different ambients. Applied Physics Letters, 1999, vol. 88, pp.183112-1-183112-3; [2] ZARASKA L., BOBRUK M., JASKUŁA M., SULKA G.D., Growth and complex characterization of nanoporous oxide layers on metallic tin during one-step anodic oxidation in oxalic acid at room temperature. Applied Surface Science, 2015, vol. 351, pp. 1034–1042.; [3] PALACIOS-PADROS A., ALTOMARE M., LEE K., DIEZ-PEREZ I., SANZ F., SCHMUKI P., Controlled Thermal Annealing Tunes the Photoelectrochemical Properties of Nanochanneled Tin-Oxide Structures. ChemElectroChem 2014, vol. 1, pp. 1133 – 1137.; [4] ZARASKA L., SYREK K., HNIDA K.E., BOBRUK M., KRZYSIK A., ŁOJEWSKI T., JASKUŁA M., SULKA G.D. Nanoporous tin oxides synthesized via electrochemical anodization in oxalic acid and their photoelectrochemical activity. Electrochimica Acta, 2016, vol. 205, pp. 273–280.

Recently, nanostructured SnO2 has become a subject of great interest, because of its unique properties which are result of both its semiconducting nature and limited size. This material can offer a wide range of applications in many devices such as transistors, lithium-ion batteries and solar cells. Among many methods used for fabrication of SnO2 nanostructures, an electrochemical anodic oxidation has received much scientific attention mainly due to its simplicity and low cost [1]. Unfortunately, in most cases nanoporous SnO2 layers synthesized via anodization exhibit transverse cracks and discontinuities in the internal oxide structure [1, 2]. In addition, very often oxide layers with completely closed pores are formed. To overcome this problem, we proposed a new method of anodization carried out in alkaline electrolyte which allows for fabrication of crack-free nanoporous tin oxide layers with completely open pores [3]. Moreover, it was proved that nanoporous tin oxide layers with ultra-small nanopores (< 15 nm in diameter) can be easily obtained when Sn anodization is carried out at a potential of 2 V in 1 M NaOH electrolyte [3].
Here we present some initial results on fabrication of multilayered nanoporous tin oxide films via potential-controlled one-step anodic oxidation of metallic Sn in 1 M NaOH electrolyte at sequentially changed anodizing potential. Nanoporous SnOx with alternately arranged segments of different nanochannel diameters were successfully obtained. Moreover, it was proved that the thicknesses of individual segments can be precisely adjusted by controlling anodizing duration

Acknowledgements
The research was partially supported by the National Science Centre Poland (Project SONATA No. 2014/13/D/ST5/02750).

References:
[1] H-Ch. Shin, J. Dong, M. Liu, Porous tin oxides prepared using an anodic oxidation process, Adv. Mater. 16 (2004) 237–240.
[2] L. Zaraska, N. Czopik, M. Bobruk, G.D. Sulka, J. Mech, M. Jaskuła, Synthesis of nanoporous tin oxide layers by electrochemical anodization, Electrochim. Acta 104 (2013) 549–557.
[3] L. Zaraska, D. Gilek, K. Gawlak, M. Jaskuła, G.D. Sulka, Formation of crack-free nanoporous tin oxide layers via simple one-step anodic oxidation in NaOH at low applied voltages, Applied Surface Science, in press

Nanocrystalline undoped and erbium doped TiO2 thin films were dip-coated on glass substrates by sol-gel method. The films were annealed at 450 °C during 1 hour. DSC results show that the crystallization effectuates at 339°C for undoped TiO2, whereas for erbium doped TiO2 the crystallization occurs earlier with two separated exothermic. XRD diagrams illustrate that undoped and erbium doped TiO2 crystallize in anatase phase only and indicate that the crystallite size decreases from 24.06 to 21.19 nm as a function of the increase in Er3+ content. This result is confirmed by Raman spectra. Moreover, the VSM results indicate, on one hand, a ferromagnetic behavior of the undoped TiO2. On the other hand, the incorporation of Erbium leads to an enhancement of the ferromagnetic behavior. It is worthy to mention that the weak Er3+doping (0.1 at.%) is the high ordered magnetically with highest saturation magnetization of 1.92 memu. Both elaborated TiO2 and Er:TiO2 films show good structural properties and have a diluted magnetic semiconductors structure. The films are promising for the possible applications in optoelectronic devices.

Two-dimensional colloidal nanocrystals have recently revealed a great potential as optical gain media due to their remarkable optical properties. Various optoelectronic devices designed for CdSe nanoplatelets have been already introduced, such as hybrid light emitting diode and vertical cavity laser shown to the right. So far these devices cover only visible spectra because they use NPLs with thiknesses of 5 monolayers or more, which optical properties are well known. We believe that ultrathin NPLs consisting of only 4 ML will show optical properties more than favorable for their use as optical gain media, providing endless oportunities for creating pure-colored light emitters for UV wavelengths. Here we have synthesised NPLs of both 5 ML and 4 ML thicknesses, studied and compared their optical properties meaning to prove that possibility.

We study the effect of hydrogen plasma treatment of ZnO thin film deposited by DC reactive magnetron sputtering system. Reactive sputtering is a simple method of depositing the undoped metal oxides material. The identity of materials was being changed from hydrogen plasma. Carrier concentration and mobility were being increased after hydrogen plasma treatment. And localized defect states below the optical absorption edge using photothermal deflection spectroscopy (PDS) that allows measuring the optical absorption down to 0,01% in a broad spectral range from UV to near IR. We have shown that the defect density and thus the electrical resistivity can be significantly increased after hydrogen plasma treatment. ACKNOWLEDGEMENTS: We acknowledge the CSF project 16-10429J and the CAS project KONNECT-007.

A one-pot method via solid-state reaction at ambient temperature was established for high throughput and green synthesis of silver nanoparticles (AgNPs). Simple co-grinding of AgNO3 and soy protein isolate (SPI), in the absence of solvent or organic protectors, achieves AgNPs in less than five minutes. Adjusting the reaction parameters such as AgNO3/SPI molar ratio and alkali concentration can readily control the loading and reduction efficiency of SPI. Using XRD, FTIR, SEM, TEM, and XPS elucidates the AgNPs nanostructures of and their formation mechanism. It was found that SPI can reduce silver ions into Ag0 to form AgNPs at high concentrations, directly and without the need for additional reducing agents.

Herein, we represent an innovative precursor for one-pot green synthesis of highly stabilized silver nanoparticles (AgNPs) at high concentration up to 2000 ppm via using of cellulose nanocrystals (CNC). For the first time, CNC without any surface modification in the presence of alkali is acting as both reducing and stabilizing agent in preparation of AgNPs. Extraction of CNC from cotton is carried out as per to acid hydrolysis (H2SO4 60% w/w) technique. The as prepared CNC are subjected to several washing treatments with deionized water to remove salts as well as the excess acid. The pH of never dried CNC slurry solution was then adjusted via using aqueous solution of NaOH (0.1M). During this, the temperature is raising up to 60 0C. At this point, equivalent amounts of silver nitrate are added separately to CNC solutions in order to prepare AgNPs with concentrations of 500 ppm, 1000 ppm and 2000 ppm. Thorough assessment of AgNPs formation, structural and morph-logical characteristics of AgNPs are investigated by making use of UV–vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, FT-IR and X-ray diffraction(XRD) analysis. Research outputs signify (a) CNC has great tendency toward reducing and stabilizing the as formed AgNPs even at high concentration up to 2000ppm, b) average Sizes and size distribution of AgNPs are less than 50 nm with sphere-like morphology even at higher concentration and c) FTIR, XRD and AFM affirm the chemical structure, crystalline phase and spherical shape of AgNPs. Green synthesis of the well stabilized AgNPs at high concentration using CNC-alkali treatment is industrial feasible for quick handling as well as easily applicable in many sectors related to antibacterial purposes e.g. textile, paints, etc.

There are many technical and industrial applications for coloured pigments with anti-fading properties. The development of a low-cost, high-volume production method for anti-fading pigments with low toxicity and minimal environmental impact may promote their widespread use. To accomplish this goal, we need to prepare pigments using abundant and environmentally friendly chemical compounds. Here, I report on the aggregates of various colours formed by spraying fine, submicron spherical silica particles. The aggregate microstructure is isotropic with short-range order on a length scale comparable to optical wavelengths and exhibits an angle-independent structural colour due to wavelength-specific constructive interference (Figure 1). Interestingly, the colour saturation of these aggregates can be controlled by the incorporation of a small amount of conventional black particles, such as carbon black (CB). We demonstrate that a Japanese-style painting can be successfully drawn with this method and that an interesting effect is obtained that can be applied to steganography

Doped zinc oxide colloids can exhibit photoluminescence. In printing industry, it is essential to prepare a feasible printing composition to gain a printable form of zinc oxide nanoparticles which after the actual print can be bound to the printing substrate. This study shows a variety of polymers, namely sodium carboxymethyl cellulose, polyvinylpyrrolidone, and 2-hydroxyethyl cellulose, used as binding agents to compare their effect on the colour and intensity of photoluminescence. Furthermore, optimal concentration of the used binder was studied as well. The optical properties of zinc oxide layers in (or without) polymeric binders were analysed with UV-Vis spectrophotometry and fluorescence spectrophotometry. The homogeneity of deposited layers was characterised from photographs using ImageJ software.

Microwave synthesis is a modern way to prepare different chemical substances in a short time period. Magnetic iron oxides are an example of these substances with two main synthetic roots known as coprecipitation method and precipitation method (using Fe2+ ions). The coprecipitation method is a method with a direct root towards Fe3O4 using a precise ratio of Fe3+ and Fe2+ ions in anoxic conditions. The prepicipation method is more simple for realization but more complex in term
of intermediate products. To influence size distribution of prepared particles we used ultrasounds
applied to Fe(OH)2 before a microwave field was applied. Fe(OH)2 is a intermediate products obtained by alkalisation of Fe2+ ions by (OH)-. Ultrasounds were applied during alkalisation and after alkalisation. The results show that the moment of application of ultrasounds is a key parameter.

Analysis of the nanoscale phases which appear on the surface Fe-6Si samples after various ways of treatments – grinding and etching, annealing, and water jet abrasion were carried out. The basic information on structure, chemical and phase composition was obtained by X-Ray Powder Diffraction (XRD), Scanning Electron Microscopy with EDX, Glow Discharge Optical Emission Spectrometry (GDOES), Mössbauer Spectroscopy, and X-ray Photoelectron Spectrometry (XPS). The results show high stability of the surface phase composition after the mechanical and heat treatments. Results obtained from the surface analysis in micrometer depth (XRD, EDX, GDOES) do not show any changes after the different treatments. Presence of iron oxides was detected in XPS and conversion electron Mössbauer spectra (CEMS) which analyze the surface composition in a nanometer scale. In addition to, fine changes in atomic ordering on the surface can be observed after mechanical and heat treatments in the CEMS spectra.

Titanium and its alloys attract much attention due to their low specific weight, good corrosion resistance, high toughness, high yield strength and efficient biocompatibility. However, these materials have poor wear resistance, high friction and low hardness. Therefore, the surface properties often need to be modified. In the present work, nitrogen ion implantation was used to modify the titanium surface. Nitrogen doped layer integrated into the surface of titanium were investigated by several methods aimed primarily at determination of chemical composition, surface microstructure, surface mechanical properties and coefficient of friction. The present study includes results of Secondary Ion Mass Spectrometry, X-ray diffraction and nanoindentation.

A great deal of interest has been recently focused on the design of new devices using one-dimensional semiconductor nanostructures. Despite a large number of applications, the growth of ZnO from solutions is not well understood and the growth technology mostly relies on empirical results. We investigate the growth of hydrothermally prepared ZnO vertical nanorod arrays on patterned substrates in continuous-flow reactors. Unlike conventional batch reactors, in the continuous-flow reactors the solution supersaturation can be accurately controlled, which allows us to compare experimental results with crystal growth theories to identify the growth mechanisms.
ZnO is a direct wide bandgap semiconductor crystallizing in the wurtzite structure with unique properties: a large exciton binding energy, which inhibits thermal activation and enhances light emission at room temperature; good optical transmittance in the visible region; high optical gain; piezoelectricity; room temperature ferromagnetism; mechanical stability given by the high melting point and large cohesive energy; radiation hardness; or biological compatibility. These properties allow for applications of ZnO in UV light-emitting devices and detectors, field-effect transistors, solar cells, piezoelectric nanogenerators, or chemical sensors. For the majority of these applications, upright standing arrays with controlled positioning, sizes, and physical properties are preferred over the free standing one-dimensional nanostructures.
The upright standing arrays of ZnO nanorods were prepared by hydrothermal growth on Si substrates with a ZnO seed layer and on GaN epitaxial layers patterned by e-beam lithography. To study the electric charge transport in the nanorods, electrical contacts were formed by the deposition of colloidal graphite

In this study, the influence of the boron to carbon ratio (B / C) in boron doped diamond (BDD) electrodes on the electrodeposition of cupric oxide (CuO) was investigated. The BDD layers were grown in a CH4 / H2 gas mixture with addition of (TMB) by using the hot filament chemical vapor deposition. The B / C ratio in the gas phase was set to 0, 2 k, 4 k, 8 k, 10 k, 15 k and 20 k ppm and CH4 / H2 was set to 1 %. The preparation of CuO was performed by potentiostatic pulse electrodeposition using 5 pulses with amplitude of -1 V and a period of 2 s. The CuO modified BDD electrodes were then characterized by scanning electron microscopy. In case of non doped diamond, no CuO deposition was observed. In the case of B / C = 2 k – 4 k ppm CuO micro particles were observed and in the case of B / C > 8 k ppm BDD was fully covered with a CuO layer. This indicates a significant influence of the B / C ratio on the morphology of the CuO film and on deposition rate caused by different BDD conductivities. CuO particles have catalytic properties for various processes and therefore may be interesting for enhancing the electrochemical properties of boron doped diamond electrodes. ACKNOWLEDGEMENTS: This work was financially supported by the grants of Slovak National Grant Agency No. 1/0785/14 and 1/0887/16 and by Slovak Research and Development Agency under the contract APVV-0365-12. The authors are also grateful for financial contribution from the STU Grant scheme for Support of Young Researchers and for the support of the DAAD for funding the cooperation.

The nitrides of AIII group are ones of the most important materials for the construction of modern optoelectronic and microelectronic devices. The large variability of band-gap ranging from 0.7 eV for InN up to 6.2 eV for AlN and possibility of solid solution synthesis gives an opportunity for construction of light emitting and detecting devices covering a broad range of wavelengths from NIR up to UV-Vis region. The syntheses of nitride nanoparticles have been reported using solvothermal synthesis and decomposition of organometallic precursors. Here we present a universal method for synthesis AIII nitrides by rapid thermal ammonolysis of complex fluoride precursors at various temperatures. Optimal conditions for synthesis of InN, GaN and AlN nanoparticles and their solid solutions were investigated in detail. The synthesized nanoparticles show hexagonal platelet character with a thickness below 100 nm. Synthesized materials were characterized by X-ray diffraction, Raman and photoluminescence spectroscopy and the morphology was investigated by SEM and TEM microscopy.

It is widely recognized that the morphology of semiconductor affects its photo activity. Studies have shown that when the top morphology changes, very often photochemical properties of TiO2 changed as well. This aspect has great impact on its photoelectrochemical applications in dye sensitized solar cells (DSSCs), where the efficiency of the process depends on the top surface reflection. The morphology of anodic titanium dioxide is also affected by: an electrolyte type and its composition (e.g., water content and the presence of fluoride anions), pH, previous usage of electrolyte, voltage, time of anodization, temperature, and hydrodynamic conditions.
In this study, the effect of short multi-step anodization on photoelectrochemical properties of formed nanoporous anodic titania was investigated. Nanoporous anodic titanium dioxide layers were synthesized at 20 ºC by a one- to six-step anodization carried out at the constant voltages of 40 V in electrolytes based on ethylene glycol containing NH4F (0.38 wt.%) and water (1.79 wt.%).
Photoelectrochemical tests were performed using a three-electrode cell with a quartz window, where nanoporous TiO2 was used as a working electrode (WE), a platinum foil as a counter electrode (CE), and a Luggin capillary with a saturated calomel electrode (SCE) as the reference electrode. The generated photocurrents were measured using a photoelectric spectrometer equipped with the 150 W xenon arc lamp and combined with the potentiostat. The photoelectrochemical characterization was performed in 0.1 M KNO3 at the potential range of 0 - 1 V and wavelengths ranging from 300 to 400 nm.

The full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory, using the generalized gradient approximation, within the DFT1, 2 framework as implemented in the WIEN2K code, in order to study the structural and optical properties of In0.25Ga0.75As and In0.75Ga0.25As ternaries alloys. The structural parameters such as lattice parameters, bulk modulus, and its pressure derivative were extracted using the local density approximation (LDA)3, and the one of Wu and Cohen (GGA-WC)4 for the exchange correlation functional, In addition, the electronic and the optical properties of our compounds were obtained by using the new semi-local modified Becke–Johnson potential (TB-mBJ)5 developed by Tran and Blaha. The performed results were compared with experimental data and other computational works. Consequently, our computations of the equilibrium lattice parameter and bulk modulus with GGA-WC and LDA approximations, generally give a good agreement with the experimental measurements. For electronic and optical properties, we deduced that the TB-mBJ approach is relatively more suitable for the properties of our two ternaries alloys.

The investigation on the formation and morphology changes of magnetite nanoparticles is done in this work in order to estimate the origin of earlier observed phenomena resulting in the formation of 2D shaped nanoparticles of magnetite at certain conditions during one-step precipitation of magnetite nanoparticles from Mohr' s salt solution with strong base (NaOH). The impact of temperature, mixing and amount of base added during the precipitation reaction is evaluated in this study. Moreover, the intermediate phases formed during the precipitation reaction are studied. For characterization of the prepared particles, SEM-EDS, XRD and PCCS analysis are performed on prepared particles.

We present results of quantum-mechanical study of structural, energetic and elastic properties of extended defects related to pentamerous-symmetry decahedron nanoparticles formed by nonmagnetic Ag and ferromagnetic Ni. Despite the complexity of decahedral shape, these nanoparticles are often observed in fcc metal particles under 50 nm. We determine surface energies of both metals for different crystallographic orientations together with the grain-boundary/quadruple-junction energies in case of the Σ3(111){110} grain boundary and a quadruple junction of Σ5(210) boundaries. These thermodynamic properties as well as structural and anisotropic-elastic properties are predicted by means of state-of-the-art density functional theory (DFT) ab initio calculations. Complementarily to studying individual extended defects separately, we also simulated decahedron nanoparticles containing a number of mutually interacting extended defects. These simulations have been performed for a number of nanoparticles with different sizes.
ACKNOWLEDGEMENTS: This research has been financially supported by the Ministry of Education, Youth and Sports of the Czech Republic under the Project CEITEC 2020 (Project No. LQ1601) and by the Czech Science Foundation under the Projects “Stability and phase equilibria of bimetallic nanoparticles” (Project No. GA14-12653S) and “Structure and properties of selected nanocomposites” (Project No. GA 16-24711S). Computational resources were provided by the Ministry of Education, Youth and Sports of the Czech Republic under the Projects CESNET (Project No. LM2015042), the Project CERIT‑Scientific Cloud (Project No. LM2015085) and by IT4Innovations National Supercomputer Center (Project No. LM2015070) within the program Projects of Large Research, Development and Innovations Infrastructures.

Electric field based control over the absorption properties of semiconductor nanocrystals is attractive for applications due to its dynamic nature and the fact that it does not require altering the structure and changing the positions of the nanocrystals. The scope of electric field applications in the nanocrystal-based devices is narrowed by the lack of a simple physical model that can be used to predict the absorption of nanocrystals in the presence of electric fields stronger than 100 kV/cm.
Here, we present a simple analytical model describing electroabsorption of semiconductor nanocuboids in a wide range of electric field strengths. Using the developed model, we study all the basic electroabsorption effects, including the Stark effect, the Franz-Keldysh effect, and the field-induced broadening of the spectral lines in the nanocrystal spectra, and perform a comparative study of the electrooptical properties of quantum dots, nanorods, and nanoplatelets. We show that the absorption peaks corresponding to the allowed interband transitions become extremely weak in the presence of strong electric field, and the absorption spectrum consists of inhomogeneously broadened lines of initially forbidden transitions, whose intensities grow with the electric field strength. We also show that among quantum dots, nanorods, and nanoplatelets, the latter kind of nanocrystals features the strongest response to the electric field, which proposes that nanoplatelets are the most promising nanocrystals for applications in electroabsorption devices.
Results of our study can prompt the development of new nanocrystal-based lasers, energy harvesting devices, and electrooptical sensing methods for measuring strong near-fields of plasmonic nanostructures.

This paper describes the measurement of the electric wind phenomenon via using Global Imaging methods. Electric wind can be described as movement of the air generated by free ions from metal object (in our case electrodes) which are powered by high voltage. This physical phenomena is a vital part of the AC electrospinning technology that was developed at Technical university of Liberec. We visualize and measure are measuring electric wind velocities around vicinity of the electrode. Measurements are done with our custom build setups. Both high voltage power source system and chamber are original pieces of equipment. We substitute nanofibrous sleeve, the product of the AC electrospinning with various electrically neutral monodispersed particles. The differences in particles are mainly conductivity and polarizability. Particles are accelerated by movement of the air and then lightened by laser and recorded on high speed camera. The outputs of our measurements are vector maps that clearly describes movements of the air around electrode.

We have investigated the temperature and shell thickness effects on the extinction and photoluminescence (PL) optical properties in II-VI semiconductor core-shells of type I. To this purpose, we use Maxwell-Garnett effective theory by defining appropriate dielectric functions for the constitutive materials of the nanoshells. Indeed, for the core, we have considered dielectric function taking into account the spatial confinement of the charge carriers along with the phonon contribution. For the shell, we have considered dielectric function similar to that used in bulk semiconductor. We obtain one sharp resonant peak related to the 1sh -> 1se optical transition, which is red-shifted with the increase of shell thickness as a possible result of the partial tunneling of the carriers wave functions into the shell. This peak is also red-shifted with increasing temperature due to core shrinking bandgap described by Varshni´s law. For the PL spectra, we have considered the radiative relaxation, the thermal escape assisted by longitudinal optical (LO) phonons and the thermally activated carrier localization in surface states as the main processes that can lead to the carrier relaxation. The Stokes shift between the absorption- and PL- peaks is of the order of a few meV. In the light of the above results, our findings are similar to that reported in the literature in absorption and PL experimental spectra.

Two-dimensional photonic crystals (2D PhC) are periodic structures with periodicity spanning in the horizontal plane, typically composed of columns or air holes distributed with the square or hexagonal lattice symmetry on the surface of a thin waveguiding layer. Their technological potential, such as the inhibition of spontaneous emission, enhancement of the optical gain in semiconductor lasers, and integration and miniaturization of optical components, motivates the search for a high optical quality structures. Various materials are used for realization of the optical photonics structures including glass, optical crystal, polymers and semiconductors. Diamond with its optical transparency in the wide spectral range, chemical inertness, biocompatibility, and large bandgap provides an outstanding platform for the development of the new class of 2D PhCs. Diamond can be fabricated either as single-crystal diamond plate but also in the form of polycrystalline diamond film, which is composed of interconnected diamond grains. To fabricate a polycrystalline diamond-based 2D PhCs on quartz substrates we applied two different fabrication strategies: i) dry etching of the continuous diamond film and ii) diamond growth on periodically structured substrates. We will discuss the influence of the diamond PhC dimensions and structural quality on the (out)coupling of light by comparing the results of transmission measurements. Transmission spectra provide direct information about the performance of the samples with respect to the (out)coupling of light from/to the structure via leaky modes and also about its optical quality. ACKNOWLEDGEMENTS: This work was supported by the MSMT project No. LD15003 within the frame of the COST Action MP1403 “Nanoscale Quantum Optics” and GACR project No. 16-09692Y.

Based on a double Fourier Transform and a modal theory we simulate the diffraction of ultrashort laser pulses through several metallic slits. The Fraunhoffer region is analyzed as a function of several opto-geometrical parameters such as broadband width, spot size and slit width.

Identification of gasoline and diesel fuels is an actual task to prevent illegal acts involving smuggling, forgery, fuel theft, establish liability for environmental disasters, etc. Existing chemical methods of fuel analysis require complex sample preparation, usage of expensive equipment and skilled staff to perform analysis. A promising approach is the use of markers which are added to the fuel at low concentrations for its identification. The concentration of the markers in the fuel must be minimized to eliminate the influence on the consumer properties of fuels. At the same time, it requires a sensitive method of marker detection, which would be able to distinguish different markers. Analytical technique used for this purpose should be able to detect and identify trace levels of markers. All these requirements are met by the SERS method utilizing the solid or colloidal plasmonic substrates. We have investigated the possibility of identifying compounds in fuels such as pyridine, 2-methylimidazole and N-methylaniline in the range of concentration from 1% to 10 ppm. Until recently, N-methylaniline was widely applied in Russia as an octane booster. Currently its use is prohibited by Euro 5 standard, therefore, its presence in fuels indicates forgery. For signal detection we used different suspensions of gold nanoparticles and portable Raman spectrometer. We found that markers at levels as small as 10 ppm can be detected and differentiated. Although the proposed markers contain nitrogen atoms, their presence in fuel is not critical because of their low concentration. The advantages of the method also include high-throughput sample preparation and analysis, and the ability to use the cheap portable automated equipment. ACKNOWLEDGEMENTS: This work was supported by Ministry of Education and Science of the Russian Federation (Target funding, project 1256).

We calculated band structure profile of AlAs-GaSb-InAs to understand lh-hh splitting depending on monolayer numbers of AlSb. Without changing e-hh electronic transition energy, incrreasing of hh-lh splitting is to important for supressing Auger recombination process. We show that thus, 3 AlSb mono layers is very suitable for midwave athmosferic windows. As aresult detectivity can be easiliy increase by using N-Structure AlSb inserted Type II superlattice system. N- Structure is very important Type II superlattice structure which is developed by ourself. We obtained 70% quantum efficiency for this system experimentally.