POSTER SESSION A

Nanocomposites are characterized by specific properties. These properties have also the composite systems of geopolymer which are produced by activation of alkaline alumino-silicates.
This article refers to nanocomposite systems using nanoparticles and carbon nanotubes SiO2.
It is presented their structure, adhesion of nanoparticles due to the geopolymer matrix and the mechanical properties of these composites.
Nanocomposite materials were made from commercial materials - cement and activator based on sodium silicate Baucis 160 L. Preparation of geopolymeric matrix was prepared by a standard method.There was used different metod for stirring, the time stirring of geopolymer was extended to 20 minutes. The amount of nanoparticles was used in the following proportions 0.5, 1.0, 1.5, 2.0, 2.5 of weight percent relative to the weight of cement. Structural characteristics were analyzed by scanning electron microscope, then the mechanical properties such as compressive strength on dynamometer.

Thinnig fosil fuel deposits and increasing emphasis on ecological aspects of human activity call for new technology solutions. Energy industry and electronics industry search for novel materials and power sources. In electronics, the power source size is often a limiting parameter. In search of high density power sources carbon materials like nanotubes, graphene, graphite, etc. known for high electrical conductivity, thermal and chemical stability and good mechanical properties, are often utilised. These materials are ideal for use in composite electrodes. Polymers in such composites serve to improve mechanical properties and handling, e.g moulding. Addition of photoactive semiconductors can help with disposal of the polymer after the use. This paper presents a study of compression molded samples of polypropylene (PP) / graphite composites and their thermal stability. The graphite served as a filler for the PP matrix and also as a substrate for MeOx particles, where Me stands for Ti and Zn. TiO2 and ZnO functionalised graphite particles were further used as a filler of PP. The graphite and functionalised graphite content in the PP composites was 75 wt.%. The samples were characterised by X-ray diffraction (XRD), Raman spectroscopy and measurement of Martens hardness (HM). The highest HM value was exhibited by composite containing large grain graphite (denoted as PP/Gra(1)). The HM was affected by thermal treatment (170°C for 1 h). The HM of the composites containing graphite fillers increased, while in case of the composites containing functionalised graphite fillers the decrease in HM was observed.

In this research work, the main objective to synthesize supported heterogenous nanocatalyst by simple co-prepitation procedure without linkers/lingads in aqueous medium and their applications for organic transformations under envrionmentally friendly reaction condition’s such as use of Microwave irradiation technique, flow chemistry and benign reaction media. The results indicates that synthesized magentic nanocompostes including Maghemite-Au, Maghemite-CuO, Maghemite-Pd and others have high catalytic activity and recyclability towards the studied applications for oxidative esterification of aldehydes, hydrogenation of aromatic nitro compounds under flow reactor and MW, and Ullmann-type condensation reaction, Heck olefination and Suzuki reaction of aryl halide etc.

Polymer composite nanofibers are formed from a polymer with inorganic nanoparticles. We deal with parameter combinations of nanoparticles, of polymers, and of solvents for the following electrospinning. They are studied the surface properties, size, crystallinity, density and toxicity of nanoparticles. Further we are studying changes in viscosity and in electrical resistance with increasing concentration of nanoparticles in solution. Combinations of components of surface energy to ensure synergy of nanoparticles with polymer in the resulting polymer nanofibers. Polymeric composite nanofibers can be used, for example, attenuation of the effects of ionizing radiation, magnetic sensors, marking biomaterials and so on.

It is well known that carbon-based materials have large variance in hardness. There are several methods for modifications of properties and hardness improving of carbon-based layers. We applied the ion beam assisted deposition for preparing of a-C:N nanolayers on Ti6Al4V alloy. A Hysitron TI 950 TriboIndenter™ nanomechanical test instrument was used for an assessment of depth profiles of mechanical properties on the modified titanium substrates. Two methods were employed in the measurements: a) quasistatic partial unload b) dynamic Continuous Measurement of X (CMX). We obtained comparable results from both methods. Average nanoindentation hardness increased from HIT ~ 5GPa for reference sample to HIT ~ 8.6 GPa for sample coated by a-C nanolayer and to HIT ~ 11.5 GPa for sample coated by a-C:N nanolayer. Average storage modulus of sample coated by a-C:N increased from E´~130 GPa (reference sample) to E´~155 GPa. However, storage modulus of the sample coated by a-C nanolayer was less than the storage modulus of titanium substrate.

Platinum is a transition metal known for its catalytic properties, which are further enhanced when employed in a nanoparticle form. We have recently shown that a monolayer of Pt nanoparticles deposited on semiconductor substrates forms a high quality Schottky diode. These Schottky diodes were used in highly sensitive hydrogen sensors with a detection limit of 1 ppm of H2 in N2. Preparation of highly ordered monolayers of Pt nanoparticles is essential for the understanding of the behaviour of such an interface. In our previous papers we reported on the preparation of Pt nanoparticles in AOT reverse micelles and their electrophoretic deposition onto Si substrates. Even though a deposition of an almost full monolayer was achieved, the nanoparticle film lacked a long range ordering. This lack of ordering was given by a large degree of polydispersity in size and shape of the Pt nanoparticles synthetized in AOT reverse micelles. To obtain a hexagonal closed-packed (hcp) nanoparticle array, we prepared Pt nanoparticles stabilized by oleylamine, which had better size and shape distribution. A monolayer prepared by dip coating of Si substrate in the suspension containing oleylamine Pt nanoparticles showed a uniform hcp arrangement with the surface coverage up to 60%. Experiments with the electrophoretic deposition of the oleylamine Pt nanoparticle suspensions are under way with the aim to enhance the surface coverage. The nanoparticle suspensions were characterized by dynamic light scattering and transmission electron microscopy. The deposited nanoparticle layers were observed by scanning electron microscopy and electrical measurements.

Silicon nanowires (Si NWs) were grown from Si wafer upon thermal annealing in the presence of catalytic gold layer. During the growth process thin film of catalyst, several nm, is usually used to initiate the process. Recently catalytic layer thickness was investigated in relation to nanowire growth. It was shown that the growth is suppressed when the gold layer thickness exceeds several tens of nanometers. In this work we investigate influence of gas atmosphere during the growth of nanowires from thick catalytic layer. The Si substrate coated with 100 nm thick Au sputtered layer was thermally annealed at 1000 °C for 60 min in vacuum, argon and hydrogen atmosphere at 8 kPa. The influence of argon and hydrogen atmospheres on the growth of Si NWs was investigated. It was found that the hydrogen atmosphere caused dense growth of Si NWs, while the growth in argon atmosphere and vacuum was sporadic. The catalytic layer morphology and composition were examined using atomic force microscopy and laser desorption-ionization time of flight mass spectrometry, while nanowire structure was observed through scanning electron microscopy and energy dispersive X-ray spectroscopy.
ACKNOWLEDGEMENTS:
This work was supported by CEITEC - Central European Institute of Technology CZ.1.05/1.1.00/02.0068 and R&D Center for Low-Cost Plasma and Nanotechnology Surface Modi
cations CZ.1.05/2.1.00/03.0086 funded by European Regional Development Funds.

We report on the preparation and characterization of boron doped diamond (BDD) thin layers grown on structured silicon substrates using hot filament chemical vapor deposition apparatus (HFCVD). BDD layers were grown in CH4/H2 gas mixture with added trimethylboron (TMB). Layers with thicknesses of 200 nm to 1 μm have been prepared with various nucleation parameters, B/C ratio and CH4/H2 ratio to optimize the deposition parameters of BDD for electrochemical applications. Scanning electron microscopy (SEM) measurements confirmed the favorable impact of oxygen plasma pretreatment of silicon substrates before nucleation on the layer adhesion, increase of BDD grains with increase of CH4/H2 ratio and possibility of production of BDD cups on the top of silicon pillars.

Diamond and ZnO are very promising wide-bandgap materials for electronic, photovoltaic and sensor applications because of their excellent electrical, optical, physical and electrochemical properties and biocompatibility. In this contribution we show that combining of these two materials opens up the potential for fabrication of bipolar heterojunctions. Semiconducting boron doped diamond (BDD) thin films were grown by HFCVD method with various boron concentration in the gas mixture on Si and UV grade silica glass substrates. Doped zinc oxide (ZnO:Al, ZnO:Ge) thin layers were deposited by diode and PLD sputtering as the second semiconducting layer. The amount of dopants within the films was changed to obtain optimal semiconducting properties to form a bipolar p-n junction. Finally, different BDD/ZnO heterostructures were prepared and analyzed. Raman spectroscopy, SEM, Hall constant and I-V measurements were used to estimate the quality, structural and electrical properties of deposited heterostructures, respectively. I-V measurements have shown a rectifying ratio of 55 at ±4 V. We found that only very low dopant concentrations of both used semiconducting crystalline materials enabled us to create functional p-n junction. Obtained results indicate a promising potential to enable the production of transparent BDD/ZnO bipolar heterojunction.

This paper deals with deposition of aluminum nitride layer on different underlayers namely silicon (100), amorphous thermal silicon dioxide, and titanium (001). The aluminum nitride layer was deposited using 3 grid radio frequency inductive coupled plasma (RFICP) Kaufman ion-beam source which provides slow deposition rate with low energy of plasma ions. This possibility leads to high homogeneity and very smooth surface. Titanium layer was deposited by argon plasma at low energy of 200 eV to attain the highly oriented c-axis layer. The aluminum nitride was sputtered on substrate which was heated to 350 °C. The nitrogen plasma only at energy of 500 eV was used. It was observed the aluminum nitride deposited on thermal silicon dioxide has the highest root mean square of roughness (RRMS) = 1.49 nm and the lowest intensity of X-ray diffraction in Bragg-Brentano focusing geometry (XRD–BB). The aluminum nitride deposited on silicon (100) shows higher intensity of XRD–BB and the lowest RRMS = 0.48 nm. Although the RRMS = 0.66 nm of aluminum nitride thin film deposited on titanium (001) underlayer was obtained, the highest intensity of XRD–BB was observed. Azimuthally averaged intensity of pole figures obtained using parallel beam setup represents the information about misorientation of individual crystallites. These analyses were performed for aluminum nitride layers deposited on titanium (001) film and silicon (100) wafer. Misorientation determined from full width at half maximum (FWHM) of the pole figures was of about 0.5° lower for aluminum nitride thin film deposited on titanium underlayer than one deposited directly on silicon substrate without silicon dioxide.

The thin films have to comply several criteria. Thin films have to be stable, mechanically resistant and applicable in industry. The thin films were prepared using plasma enhanced chemical vapor deposition technique.
Serie of experiments was started with extended study of surface free energy on polycarbonate and optimisation of substrate surface treatment process before deposition of thin film. For treatment the low pressure glow discharge in hydrogen and nitrogen was used.
Once the process of pre-treatment was optimized, big serie of experiments with different kinds of thin films was done. Thin films were prepared on different types of substrates among others crystalline silicon, glass and polycarbonate.

The surface termination of diamond films strongly affects the surface properties of diamond by inducing electrical conductivity as well as behavior of metal contacts and their characteristics. Previously we reported that surface conductivity of hydrogen-terminated nanocrystalline diamond (NCD) films can be modified by its exposure to different gases and high response was found for phosgene.
In this work, we focus on the fabrication of diamond based gas sensor working at room temperature. The diamond films were grown on fully-integrated sensor device on a micro-hotplate using microwave plasma enhanced chemical vapor deposition (MW PECVD) process at temperature as low as 470ºC. Afterwards the hydrogen termination of diamond surfaces was carried out by their exposure to 25 sccm of H2 for 10 min in a MW PECVD reactor. Then the hydrogen terminated diamond surfaces were fluorinated using RF plasma at 20 sccm CF4 flow rate for 30 s. The comparative sensing performance of hydrogenated diamond surface shows improvement in sensitivity toward acetone, benzene, isopropylalcohol and humid air in contrast to fluorinated diamond surface, where the surface conductivity was suppressed. The influence of the surface area (adjusted by nucleation time) and the electrode arrangement on the sensitivity of NCD sensor is discussed.
The work was supported by the GACR project 14-06054P.

In this work, we study the influence of growth process parameters on photoluminescence activity of Si-V colour centres in diamond. The diamond films were grown by microwave plasma enhanced CVD system. Temperature dependent steady-state photoluminescence of Si-V centres was measured within the range 11-300 K. Photoluminescence measurements are correlated with process parameters (i.e. the influence of CO2 (up to 4.5%) or N2 (up to 6.0%) addition into the H2/CH4 gas mixture, and the substrate temperature (350–1100°C)). Adding of CO2 or N2 in the gas mixture monotonically suppressed the PL intensity, while 800°C was the optimal substrate temperature at which the highest photoluminescence activity of Si-V centre was measured. For all the samples, the temperature dependent PL measurements exhibited the blue shift in zero-phonon line (ZPL) position for lower temperatures and for selected samples, ZPL narrowing were observed. This effect will be discussed from point of temperature behaviour of Si-V electronic transition energy. A technological control of Si-V colour centre activities is perspective for life science and photonic applications.

The aim of the present work was to deposit transparent polymer SiOxCyHz protective coatings from hexamethyldisiloxane/oxygen mixtures in capacitively coupled glow discharge. The coatings prepared under dusty plasma conditions showed nanocomposite character. Complex characterization of the local mechanical properties was carried out on the prepared samples from nano to microscale using indentation techniques. The coatings were very elastic, they exhibited high elastic recovery and low plastic deformation even at indentation depths approaching the coating thickness.

We present the novel, effective, and simplified methodology to simulate and investigate physical properties of vertically aligned multiwall carbon nanotubes (MWCNTs), the mechanical properties in particular. Unlike conventional solutions, we consider nanotube as a beam with a fixed end and a free end, allowing us to employ the mechanics of beam used as cantilever. Considering the atomic force microscopy (AFM) force-distance measurement as possibility to experimental determination of CNTs mechanical properties, we simulated the interaction of carbon nanotube structure with AFM cantilever at the applied force. We investigate the effect of inner and outer radius, different values of Young’s modulus, and various lengths of MWCNTs. The methodology, we present, is a significantly quick simulation approach providing validate information about MWCNTs mechanical behavior.

Montmorillonite was found to be useful matrix for the direct preparation of graphene sheets from conducting polyaniline in the interlayer space of montmorillonite. Oxidative polymerization of the solution of anilinium sulfate by ammonium peroxydisulfate in the presence of montmorillonite particles (size fraction ˂ 40 μm) led to the formation of polyaniline chains both on the surface (revealed by SEM analysis) and in the interlayer space of montmorillonite (proved by a combination of X-ray diffraction analysis and molecular modeling). SEM analysis also showed that superfluous polyaniline created an independent clusters between montmorillonite particles.
Such prepared powder material was pressed into tablets using pressure 400 MPa and these tablets were calcined in dynamic argon atmosphere at temperature 1400°C for 1 hour. X-ray diffraction analysis revealed that calcination induced phase transformation of montmorillonite into cristobalite and mullite preserving the layered structure and thus creating good conditions for formation of graphene from polyaniline chains between the silicate layers.
In fact, three different types of carbon were found by X-ray diffraction analysis and Raman spectroscopy in the resulting material: amorphous carbon, graphite and graphene. Since tablets pressed from pure polyaniline and calcined under the same conditions contained only amorphous carbon, we assume that clusters of polyaniline between montmorillonite particles were transformed into amorphous carbon while polyaniline chains creating layer on the montmorillonite surface turned into graphite and polyaniline in the interlayer space was transformed into graphene.
Original tablets before calcination exhibited electrical conductivity 0.03 S/m in a direction parallel with the montomorillonite layers. After calcination, the conductivity strongly increased 23000 times to 693 S/m suggesting the presence of highly conductive form of carbon.

In this study, we demonstrated the synthesis of two composites consisting of carbon nanotubes and clay mineral montmorillonite which could be used as ceramic reinforcement. Synthetic and natural montmorillonite were examined as a matrix for synthesis using hot filament chemical vapor deposition. Synthesis of CNTs on natural forms of montmorillonite but also on synthetic form can only be achieved by incorporation of a catalytic phase. We have observed, that there is no significant difference between natural and synthetic montmorillonite compared to the final carbon phase. In both cases is the surface of mineral covered by dense network of CNTs.

Electrically conductive composites with polymeric matrix (CPCs) and carbon based filler are the promising group of synthetic materials combining excellent mechanical properties of nonconductive matrix and electrical properties of conductive filler. These materials find application in many fields of interests such as an electromagnetic interference shielding, electro-optical devices, electrostatic discharge or signal transfer used in aerospace, marine, and automotive industries. Conductivity of CPCs can be positively or negatively influenced by many factors, such as change in external conditions, amount of conductive filler, etc. In this work, the changes of conductivity of CPCs with polypropylene matrix and conductive graphite filler are presented. Polypropylene/graphite (PP/graphite) composite was prepared via blending granulated PP, maleic anhydride grafted PP (MAH-g-PP) and natural graphite (either 65, 70 or 75 wt.%). It is obvious that the conductivity increases with increasing amount of conducting filler. The most conductive sample was thermally treated at 170°C for 1 hour or exposed to UV irradiation for 1 and 24 hours. The macroscopic conductivity disappeared and the changes in local current on the surface were studied using scanning spreading resistance microscopy (SSRM). SSRM shows that after the thermal treatment and UV irradiation the conductive areas disappeared and only residual current on the edge of the graphite particles was detected. Positive as well as the negative changes of conductivity of composites have a great influence on their further application.

This paper examines the mechanical properties of the composite of thermoplastic polymer matrix with carbon nanotubes. As the basic polymer matrix was used polyamide (ABS) to which were added the nanoparticles in a given percentage by weight in the form of nanotubes. Composite was injected into the Arburg injection molding machine. For evaluation were measured harness, impact and tensile test. These tests are compared with polymeric materials without added nanofiller. In conclusion is evaluated and compared influence on the mechanical properties of polymer matrix with carbon nanotubes and without fillers.

Graphene´s unique properties predestines it to be great material for the future use in nanoelectronics. Mechanical deformation is one of the methods to manipulate optoelectronic properties in graphene. However, not many succesfull experiments have been performed up to date. One particular way to induce changes in the crystal structure is through bending instability, which creates wrinkles in the system. Wrinkles can be the right way to reach the 1D quantum confinement. In our work we report on the formation as well as on the characterisation of wrinkles created on prestrained polymeric substrates.
Graphene flakes were preparad by mechanical exfoliation on prestrained substrates (bent PMMA-SU8 beam or stretched PDMS). Monolayer as well as few layer graphene sections were identified with optical microscopy. The number of graphene layers was determined by Raman spectroscopy. The surface wrinkling was characterised by Atomic Force Microscopy and by Raman mapping.
Wrinkles formed in graphene placed on prebent (~1%) PMMA-SU8 coated beams exhibit strong linear relation between wavelenght and amplitude as well as the dependence of these parametres on the number of graphene layers. The wrinkles have a clean sinusoidal shape and the onset of wrinkling from the edges corresponds to the wrinklon model(1).
Wrinkles formed on highly prestrained (~50 %) PDMS show inhomogeneous distribution as well as sharp ridges and higher aspect ratio. The ridges are not in contact with substrate surface.
ACKNOWLEDGEMENTS:
This work is supported by Czech Science Foundation (project nr. 14-15357S).
REFERENCES:
(1) Vandeparre et al. PRL 106, 2011, 224301

In this research the heat capacity in the temperature range from 6 to 600 K for functional derivatives of C60 and C70 fullerenes were determined by precision Adiabatic Vacuum Calorimetry (AC) and Differential Scanning Calorimetry (DSC). The phase transitions and in some case chemical transformations were detected for compounds rank under study. The thermodynamic characteristics of these transformations were determined and analyzed with literature results about composition and structure of objects.
Thus, covalent bounded fullerene contained polymers was investigated. The influence of C60 and C70 fullerenes on thermodynamic characteristics and parameters of devitrification and glassy state was revealed. The dependence of temperature of destruction onset for polymers from fullerene content was established.
The heat capacity, characteristics of phase transitions and standard thermodynamic properties of C60 and C70 fullerides with organoelement fragments were studied for the temperature range from 6 to 350 K. On the based of our thermodynamic data, information about the structure and the composition of these and the respective data for the neutral dimer (C60)2 the some conclusion about the bound nature between fullerene fragments in the complex was made.
The standard thermodynamic properties of crystalline polymeric nanostructures of C60 fullerene and amorphous graphite-liked and diamond-liked nanostructures were studied. The dependences of thermodynamics properties vs composition and structure of compounds were analyzed. The rank of relative thermodynamic stability of crystalline phases of C60 at T = 298.15 K and standard pressure was determined. Thus, standard thermodynamic properties of indicated nanostructures, C60 and C70 fullerites, graphite and diamond were compared.
The results of AC were used to calculate the thermodynamic functions: the heat capacity, enthalpy, entropy, residual entropy and Gibbs energy over the range from 0 to 350 K.

Styrene-isoprene-styrene (SIS) block copolymer/carbon nanotubes composite was prepared by deep casting method. The specimen was prepared by dipping of the copper interdigitate electrode into the SIS/carbon nanotubes dispersion in toluene.
The Kraton D SIS is thermoplastic elastomers with a combination of high strength, low hardness and low viscosity for easy thermoplastic processing in solution state. Present work is motivated by the fact that carbon nanotubes have high surface area. Due to this fact carbon nanotubes can easily adsorbed or desorbed gaseous/vapors molecules. Carbon nanotubes also play important role in the electrical path creation because of their electrical conductivity.
Another motivation for presentation this results is the fact that volatile organic compound in the form of vapors, solvent, or gases are widely used in the industry and could be potentially danger for human. We report the preparation and testing the sensing element for volatile organic compound on the base of Styrene-isoprene-styrene (SIS) block copolymer/carbon nanotubes. The sensing element is made by easy dipping method. By this way was reached very thin, sensitive and homogenous layer. The sensor was testing for few solvents. The solvents were chosen according to their ability to swelling/ dissolve the (Styrene-isoprene-styrene (SIS) block copolymer matrix. I this case the suitable candidate seem to be acetone, toluene as a swelling/dissolve agent and ethanol as non-solvent agent. The testing solvents are in the form of saturated vapors.

We studied bond properties of graphene’s fluorinated derivatives and adsorption of fluorine, chlorine and hydrogen atom on graphene. For all calculations density functional theory was used. The character of C-F bond varies with fluorine concentration and local structure: one atom of fluorine makes ionic bond with graphene, but C-F in fluorographene (100% coverage) corresponds to a covalent bond. Configurations with fluorine atoms in trans positions are highly stable. On the other hand, hydrogen atom makes both noncovalent and covalent bond with graphene, which is weaker than a classical hydrogen-carbon covalent bond in other compounds. Chlorine does not make a typical chemical bond with graphene at all, but it creates a charge transfer complex. The strength of this bond is similar to the strength of the hydrogen-graphene covalent bond. Fluorine interacts more strongly with graphene than hydrogen and chlorine. Finally, adsorption of atoms significantly changes electronic properties of graphene.

Tuning the properties of single-molecule magnets (SMMs) through interaction with magnetic materials is a challenging feat that could generate extremely interesting products with enhanced magnetic properties. Such interaction can be potentially achieved using metallic magnetic nanoparticles, but non-metallic graphene-based materials represent a newer and exciting way to influence the properties of SMMs.

A new type of polystyrene (PS)/carbon nanotube (CNT) network laminate is introduced as an electrically conductive composite material; with favorable properties as electro-mechanical signal transducer capable to detect applied mechanical strain. In course of its fabrication a non-woven polystyrene membrane made by electro spinning was used as filtering mesh for CNT aqueous dispersion. Produced semi-product like filtering membrane with entrapped carbon nanotubes was stuck using solvent of PS on polystyrene test specimen. The electrical resistance of final laminate is sensitive to tensile strain when elongation leads to increase of macroscopic electrical resistance. Test specimens were then tested in the course of monotonic strain growth and also when loading/unloading cycles were imposed. Changes in resistance were found to be reversible, reproducible and deformation can by monitored in real time. Finally, sensitivity to strain can be quantified by means of a gauge factor, GF, which defines sensitivity of strain gauge as a relative resistance change divided by the applied strain. Measured GF for PS/CNT laminates reaches relatively high values, compared with ones of commonly used metallic strain gauges, serving for values of around 13 and applied tensile deformation in range 0.1-0.6 %. These experimental results are really promising serving for real practical application of this principle in course of polymeric based strain gauges or as an integrated PS/CNT units into polystyrene based constructions for their so called “health monitoring”.

Graphene-like materials have attracted a lot of attention during recent years due to their unique properties and wide range of applications. This paper is concerned on preparation of materials based on graphene oxide (GO). We performed simultaneous oxidation of graphite and fullerene C60 to prepare hybrid GO-C60 compounds. Further characterization, modification and freeze-drying of prepared product were carried out. The aqueous GO-C60 suspension has the ability to form fine films, their morphology was studied here. Further, we dealt with freeze-drying of prepared products. Due to promising adsorption and separation capacity of GO we suppose possible usage of GO based materials in protective equipment.

Carbon nanowals (CNW) thin films are very promising for various electrochemical and energy storage applications. Its high surface area, porosity and good electrical conductivity make it an ideal electrode material for electrochemical sensors, supercapacitors and batteries. In this work, hot filament chemical vapour deposition (HFCVD) technique was used to grow CNW on silicon substrates using various gas flows of methane and hydrogen. Raman spectroscopy and SEM were used to perform the structural and morphology characterization of the prepared samples. The ID / IG ratio calculated from Raman spectra and its dependence on the CH4 / H2 ratio is described and discussed. We found that, the size and disorder of the multi-layer graphene structure of the deposited CNW thin films is strongly affected by the methane to hydrogen ratio.

Vertical arrays of ZnO nanorods were prepared by low temperature hydrothermal method on a seed layer consisting of electrophoretically deposited ZnO nanoparticles [1]. The low temperature growth results in a high density of native defects, which strongly affect physical and optical properties of ZnO nanostructures. A typical photoluminescence spectrum of ZnO nanorods contains excitonic lines in the UV region and a broad band in the visible region. The red, orange, yellow, and green broad bands are attributed to a variety of native defects such as oxygen vacancies, zinc vacancies, oxygen interstitials, zinc interstitials, and clusters formed by two point defects. Nevertheless, a controlled introduction of defects can be useful for specific applications such as gas sensors or UV photodetectors [2, 3]. In this work we demonstrate that both excitonic line and visible broad band of the ZnO NRs can be easily tuned by applying H2O2 treatment. The H2O2 treatment introduces more oxygen-related defects and thus enhances chemisorption processes in ZnO nanorods.
ACKNOWLEDGEMENTS:
This work was supported by EU COST Action TD1105 – project LD14111 and by the Czech Science Foundation project 15-17044S.
REFERENCES:
[1] R. Yatskiv, J. Grym, P. Gladkov, O. Cernohorsky, J. Vanis, J. Maixner, J. H. Dickerson, submitted to Solid-State Electronics; [2] R. Yatskiv, J. Grym and M. Verde, Solid State Electron 105, 70-73 (2015); [3] R. Yatskiv, V. V. Brus, M. Verde, J. Grym and P. Gladkov, Carbon 77, 1011-1019 (2014).

Mechanical/physical properties are the most important parameters that determine the ease with which silica powders can be handled, stored, transported and processed. Because of silica powders have wide range of its application from pharmaceutical industry, printer toners and electronic parts to application in cancer treatment. Due this fact the silica belongs to highly studied substances across different fields. This is a material with a huge potential and very unique mechanical/physical properties of SiO2 powders which make them very attractive. In this paper, friction properties, compressibility factors and flowability of SiO2 microparticles with nanoparticles addition have been investigated. For this purpose a several mixtures with different amount of nanosilica were prepared and characterized. Experimental work was performed by the Freeman Technology FT4 Powder Rheometer, CPS DC24000 Disk Centrifuge and laser particle size analyzer Cilas 1190 in Laboratory of Bulk Materials in Ostrava. Also a basic characterization such as SEM images, shape analysis etc. of the raw input material was made. The first results show that additions of nanoparticles influences all studied parameters. This study make a significant contribute to the valorization “dry-coated fine particles” theory, which is based on guest-host contacts. During experiments there were discovered a few difficulties. Nanoparticles forces may dominate and individual nanoparticles of the silica adhere one to another and form agglomerates with porous structure. Because of this aglomerates can not be break-down easily and disperse on the host SiO2 microparticles surfaces.

Nanodiamonds (NDs) are highly promising material for biomedical research due to their outstanding optical and magnetic properties and low toxicity. We developed a complex route to the bioapplicable fluorescent nanodiamond particles, including boosting of NDs fluorescence, shaping the particles to become pseudospherical and coating the particles with antifouling and modifiable polymeric shell. [1, 2] Starting material used in our work is prepared under high pressure-high temperature (HPHT) conditions, particles are polydisperse and of irregular shape bearing sharp edges and spiky vertexes. Recent research of cellular fate of diamond nanoparticles has revealed that behaviour of the original angular particles differs from that of rounded NDs. [3]
Here we present a procedure of rounding of NDs at a large scale and a study of rounded NDs properties. The rounding process is based on chemical etching of rough ND particles in molten potassium nitrate and results in pseudospherical NDs with changed particle size distribution. Our study shows dependence of round NDs behaviour, shape and size distribution on etching conditions and compares the results with angular NDs. Round NDs can be easily further processed to create fluorescent and polymer-coated round NDs, unique material perfectly suitable for bioprobes and sensors construction.
REFERENCES:
[1] Rehor, I. et al., Small, 2014, 10(6), 1106–1115. [2] Rehor, I. et al., ChemPlusChem, 2014, 79(1), 21-24. [3] Chu, Z., et al., Sci. Reports, 2014, 4, 4495.

Diamond has outstanding properties which make it a promising material for a wide variety of applications. However, the synthesis of homogeneous large area films on non-diamond surfaces is still a challenge. The material of the substrate and its surface pre-treatment (nucleation) strongly influence the properties of the resulting film.
In this study, we present polymer-based carbon as the nucleation layer for diamond deposition. Two types of polymers were used: polylactic-co-glycolic acid (PLGA) and polyvinyl alcohol (PVA). Both polymers were used either as microspheres or thin films (without/with diamond powder-DP). The polymer films were prepared using spin-coating. The diamond CVD growth was performed in a microwave plasma system.
For ultra-thin pure polymer layers and microsphere monolayers we did not observe any diamond growth. However, increasing the polymer thickness (2-3x spin-coating) enhanced the nucleation process. Higher nucleation density was also observed for a combination of polymer microspheres with pure polymer layers. For (ultra-) thin polymer composite layers containing diamond powder, a clear increase of the nucleation densities was achieved. We propose a model in which carbon-based polymers act as the nucleation layer providing an additional source of C atoms which are partially converted into sp3 bonded carbon phase.
This technique allows diamond growth over a large area on a wide range of substrates, including extremely soft or fragile samples, or substrates with complex geometry and shape such as 3D GaN membranes.

Preparation of iron oxide nano- and submicro-structures with prolonged shape gets great attention due to their unique properties resulting from the shape anisotropy. However, most of the methods proposed for nanostructures synthesis, such as solvothermal and hydrothermal, results in the formation of spherical or polyhedral particles. Among the synthetic routes that support a growth in a certain direction, “precursor syntheses” are interesting from technological point of view since these methods are simple, cost effective and enable large-scale production. Methods utilizing organometallic precursors that decompose at relatively low temperature appear to be the most suitable for both, laboratory and practical use. For this purpose, ferric and ferrous oxalates seem to be proper candidates due to their preferred growth in one dimension at proper conditions thus forming rod-like structures. Conversion of precursor into the final product is a topotactic reaction thus the forming particles preserve the shape given by the precursor. However, tuning the shape of particles and obtaining of particles with high aspect ratio is usually conditioned by the use of surfactants. We performed a synthesis of iron oxalates by various routes and showed that particles aspect ratio can be tuned without a use of any surfactant. Iron (II) oxalate was prepared by a conventional heating, microwave-assisted synthesis at atmospheric pressure utilizing external cooler and also microwave solvothermal synthesis utilizing pressurized reactor. Important finding lies in a possibility to prepare one-dimensional nanostructures with uniform shape by utilizing of microwave solvothermal synthesis without the use any additional surfactants or capping agents.

Structural and magnetic properties of iron nano-clusters that are formed in ytterbium films, prepared by vapor co-deposition onto Kapton substrates kept at room temperature (RT), have been investigated by X-ray absorption spectroscopy, Mössbauer spectroscopy and magnetization measurements as a function of temperature and magnetic field. EXAFS analysis indicates a short-range order for Fe atoms, which is consistent with nano-sized Fe clusters. The temperature dependence of the magnetic properties, using zero-field and in-field Mössbauer spectroscopy as well as AC and DC magnetization measurements, reveal two types of iron clusters, with non-cubic symmetry, that are associated with clusters at ytterbium grain boundaries. In addition, zero-field and in-field Mössbauer experiments indicate that the interactions within the Fe-clusters are predominantly ferromagnetic-like and their average magnetic moments are about 80 μB. As suggested by Mössbauer and AC magnetization data, the Fe-clusters are super-paramagnetic above ca. 20 K, while their magnetic behavior below this temperature is that of cluster-glass-like systems with weak inter-cluster interactions.
ACKNOWLEDGEMENTS:
This work was supported by CNPq/PCI, FAPERJ, FAPES, Brazilian-German research programs financed by CNPq/DFG 444BRA-113/55/0-1, DAAD/CAPES PROBRAL 56265881, and FONDECYT/CONCYTEC.
REFERENCES:
[1] C. Rojas-Ayala, W.T. Herrera, I.S. Dinóla, E.C. Passamani, M. Kraken, E. Baggio-Saitovitch, F.J. Litterst, Hyperfine Interact. 224 (2014) 299–305.
[2] C. Rojas-Ayala, E.C. Passamani, N.M. Suguihiro, F.J. Litterst, E. Baggio Saitovitch, Materials Characterization 96 (2014) 108–114.
[3] C. Rojas-Ayala, E. C. Passamani, F. J. Litterst, E. Baggio-Saitovitch, J. Appl. Phys. 116 (2014) 183907.

The article describes the influence of an unconventional forming method, such as DRECE, on the resulting mechanical properties and structure of tested materials. In the laboratories of the Technical university of Ostrava we have prototype equipment DRECE for production of very fine grained or nanostructured materials in the form of metal strips. The research is focused on perspective materials, mainly on non – alloyed steels and on selected types of non – ferrous alloys. Material after application of the DRECE process has diametrically increased mechanical properties (Ultimate strength, Yield strength, Hardness, etc.). Ultra ‐ fine ‐ grained (UFG) or nanostructured materials represent a new generation of advanced materials exhibiting unique and technologically attractive properties due to dimension and relationship outcomes. Possibilities of nanostructured materials to change many technologies are almost unprecedented.

CALPHAD approach is a very useful technique for calculation of phase diagrams of bulk materials based on thermodynamic database containing data such as chemical potentials of pure substances and excess Gibbs energy of mixtures as a function of composition, temperature and pressure. In order to extend the use of CALPHAD approach to small metallic particles on sub-micron and nano scale, due to the surface effect, the chemical potentials and the excess Gibbs energy should be expressed with an additional parameter: the particle size.
In this study, the nanoalloy Ag-Sn binary phase diagram was calculated by using the CALPHAD method. Silver-tin alloy is one of the promising alternatives for Sn/Pb solders. The calculated nanoalloy phase diagram was verified using experimental data from the literature and also the data from own experimental work.
ACKNOWLEDGEMENTS:
Financial support of the Grant Academy of Czech Republic (grant No. 14-12653S and grant No. 14-15576S) is gratefully acknowledged.

A new key intermediate, 5-(1-benzofuran-2-yl)thiophene-2-carbonitrile, has been prepared and further been used for the synthesis of three DPP pigments by a base catalyzed condensation with succinic ester, 2-phenyl- and 2-(thiophene-2´-yl)-pyrrolinone esters. Their soluble N,N´ dialkyl derivatives were prepared either by direct alkylation with branched alkyl, alkyl ester and acetal, or by Pd catalyzed cross-coupling reactions starting from smaller dialkylated 3,6-dithiophene substituted DPP precursors. Both synthetic routes were critically compared. The second route is considerably more efficient for N,N´-alkylation with branched alkyls, while for an alkylation with branched alkyl esters the yields are comparable. Thermal properties of N-unsubstituted pigments were investigated by TGA which proved high thermal stability. The high sublimation temperature of this pigment (492 °C) exceeded other commercially available DPP pigments. Both absorption spectra as well as electrochemical measurements revealed that the tuning of opti-cap properties and the HOMO-LUMO gap can be carried out either by varying N-substituents or the number of peripheral benzofuran moieties. The experimental data were further supported by the DFT calculations and structure-property relationships were elucidated. Owing to the excellent electrical and optoelectronic properties, DPP derivatives have been attracting extensive attention in solution-processed organic electronics, such as field-effect transistors (OFETs) and photovoltaics (OPVs), which can offer large-area and flexible devices of next generation. In particular, OFETs are an important fundamental component for such devices.

Large band-gap materials, such as diamond or gallium nitride (GaN), are the prime candidates for a variety of sensor applications, particularly working at high temperatures and in harsh environments. In the case of GaN based FETs working at high temperatures, the highly efficient thermal management should be solved in order to suppress the self-heating effect of the device. Combination of diamond and GaN represents an attractive choice for high power electronics where diamond acts as heat spreader.
In the present study, we focus on the diamond-coated c-HEMTs, especially on the influence of the gate electrodes (Ir or IrO2) and the passivation layer (Si3N4) on the electrical characteristics. It was observed that a 100 nm thick SiN layer (without additional diamond coating) improved the electrical characteristics of c-HEMT. This effect was attributed to compensation of subsurface defects and vacancies in AlGaN/GaN active layer. However, after diamond deposition the gate electrodes were degraded. We found out that by short time annealing (2÷5 min) of Schottky gate electrodes in oxygen the obtained gate electrodes in the form of conductive metal oxide layers (i.e. IrO2 instead of Ir) can withstand aggressive conditions during diamond deposition even at much higher temperatures (~1000°C). The obtained results were found as necessary technological issues to successful fabrication of all-in-diamond c-HEMT devices for high-temperature and high-power applications.

Diamond thin films were used as the substrate to cultivate cells and as the bio-electronic sensor. Here we studied the influence of yeast cells (Saccharomyces cerevisiae) on the electrical characteristics onf nanocrystalline diamond-based solution-gated field effect transistor (SGFET). Two different culture solutions (sucrose and yeast peptone dextrose (YPD)) were used without or with yeast cells. The measurement principle of diamond-based SGFETs is based on the H-terminated active surface, which is very sensitive to environment (solution/cell-substrate interactions) and is directly responsible to formation of with subsurface p-type channel of the transistor. Two different cell culture solutions (sucrose and yeast peptone dextrose (YPD)) were used, with or without yeast cells.Any change of the solution or cell culture behavior is reflected in the electrical characteristics of SGFETs. This feature of diamond SGFETs is used for studying the cell-solution and cell-substrate interaction. The transfer characteristics of SGFETs showed a negative shift of the gate voltage to higher values for both cell solutions, i.e. sucrose and YPD with cells, by -26 mV and -42 mV, respectively, in comparison to blank solutions without cells. Possible reason of Tthis effect is attributed to the pH could be related to change in pH in a close vicinity of at the H-terminated diamond surface due to metabolic processes of the yeast cells. The pH sensitivity of the diamond SGFETs as well as the role of the negative surface charge of yeast cells on the experimental SGFETs electrical characteristics results are discussed.

The ternary Cu-Sn-S system, as an important I-IV-VI group semiconductor with small or mid band-gap, have attracted great attention owing to broad application in photovoltaic devices and H2 evolution under visible light irradiation. In this contribution, Cu2SnS3 nanostructures were successfully synthesized by microwave-assisted solvothermal route in a short time, using CuCl2.2H2O, SnCl2.2H2O and thiourea as starting chemicals. The influence of solvent on structure, morphology and optical properties of the as-prepared samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy, and Raman spectroscopy. The morphology of products can be tuned from flower-like to sphere-like by using diethyleneglycol instead of ethyleneglycol as a solvent, while the cubic crystal structure remain unchanged.

Helicenes attract attention as simple models for screw-shaped biomolecules, such as proteins and nucleic acids. Recently, they have been recognized as potential building blocks in nanomaterial sciences and the interest in their chemistry and physico-chemical properties has remarkably increased. The pioneering synthesis and resolution of hexahelicene was afterward followed by successful photochemistry-based attempts at the preparation of nearly homologous series of [n]helicenes. Helicenes as unique 3D polyaromatic systems are chemically stable, soluble in common organic solvents, and π-conjugated materials. This sets them apart from planar polyaromatic systems, which are often insoluable and unstable. Thus, helicenes represent an attractive objective for further research in various branches of chemistry and nanoscience. For mechanical and electrical simulation of helicenes we used Atomistix ToolKit licensed by QuantumWise. It is combining DFT and NEGF for ab initio and semi-empirical calculations of structure and electron transport. We simulated molecular mechanics and basic electronic properties of different helicene structures in standalone and two electrode configurations as well. Molecular energy spectrum, the density of states and electron transmisivities of these structures has been analyzed.

Mixed TixSiyOz materials offer interesting optical properties due to the high difference between refractive indices (TiO2: ~2.5, SiO2:~1.5) and band gaps (TiO2: ~3.2 eV, SiO2: ~8.5 eV). By changing composition a fine-tuning of the optical properties is possible. This opens new possibilities in design of optical devices.
In the present work, the variation of Ti(1-x)SixO2 optical constants caused by changed Si concentration are examined by employing Density Functional Theory. Special Quasirandom Structures method is used to generate structural models of Ti(1-x)SixO2 disordered solid solutions based on TiO2 and SiO2 phases. These initial supercells are structurally optimized (i.e. optimized with respect to the cell shape, size, and atomic positions) using the Vienna Ab initio Simulation Package. Ab initio Molecular Dynamics approach (“simulated annealing”) is used to generate structural models of amorphous phase. Optical
constants of the resulting structures are calculated by the linearized augmented plane wave method as implemented in the Wien2k code together with the recently developed modified Becke-Johnson exchange-correlation potential allowing precise prediction of electronic structure and band gap. The calculated dielectric function is compared to the experimental
data obtained by fitting the optical measurements (ellipsometry, spectrophotometry) carried out on TiO2 and TixSiyOz films prepared by plasma enhanced chemical vapor deposition and atomic layer deposition.