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A series of neodymium oxide-supported cobalt catalysts with cobalt content ranging from 10 to 50 wt.% was obtained through the recurrent deposition-precipitation method. The effect of active phase, i.e., metallic cobalt, content on structural parameters, morphology, crystal structure, surface state, composition and activity of the catalysts was determined after detailed physicochemical measurements were performed using ICP-AES, N2 physisorption, XRPD, TEM, HRTEM, STEM-EDX, H2-TPD and XPS methods. The results indicate that the catalyst activity strongly depends on the active phase content due to the changes in average cobalt particle size. With the increase of the cobalt content, the productivity per catalyst mass increases, while TOF maintains a constant value. The TOF is below average only for the catalyst with the lowest cobalt content, i.e., when the average Co particle size is below 20 nm. This is due to the predominance of strong hydrogen binding sites on the surface, leading to hydrogen poisoning which prevents nitrogen adsorption, thus inhibiting the rate-determining step of the process.

New perspective cubic quasi-alloy {CdO/MgO}m short-period superlattices (SLs) were grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The quality of crystals was charac...

Gallium phosphide can be considered as a prospective material for impurity band solar cell (IBSC), if sufficient amount of an appropriate impurity (Ti in our case) is introduced to the material by ...

O-Carboxymethylchitosan-N-lauryl/γ-Fe2O3 magnetic nanoparticles (OCh-LM) were synthesized and characterized using FT-IR, TGA, SEM and VSM. The OCh-LM was essentially spherical in shape, with a mean particle size of 11.1 ± 3.4 nm and saturated magnetization of 18.4 emu/g. The nanoparticle was used to remove the anionic dye Remazol Red 198 (RR198) from aqueous solution by the batch system. The kinetic data and adsorption isotherm were best fitted by the pseudo-second order kinetic model, and the Langmuir–Freundlich isotherm, respectively. Thermodynamic parameters such as change in enthalpy, change in Gibbs free energy and change in entropy were estimated, and the results indicated that the adsorption process was spontaneous and endothermic. The maximum adsorption capacity, calculated through the Langmuir–Freundlich model at 25 °C, was 216 mg/g. Desorption of the dye and reuse of the adsorbent were performed in four cycles. These results show that OCh-LM can be potentially used as a magnetic adsorbent to remove RR198 and probably other anionic reactive dyes from aqueous solution for avoiding the secondary pollution. Keywords: Dye adsorption, Magnetic nanoparticle, Magnetic separation, O-Carboxymethylchitosan-N-lauryl/γ-Fe2O3, Remazol Red 198

Magnetic carbon activated (MAC) Fe3O4-loaded activated carbon was developed using termite feces and sulfuric acid as the carbon-modifying agent. The key point of the synthetic strategy was that the carbonization, activation and Fe3O4 loading were accomplished simultaneously, via thermic activation/magnetization. The adsorptive characteristics of the MAC for removal of Cr(VI) were investigated. Batch adsorption experiments were performed using both AC and MAC. The evaluation of the adsorption kinetics, isotherm, and thermodynamics was investigated. Adsorption of Cr(VI) onto MAC was highly pH dependent and was found to be optimum at pH 3.0. Nonlinear regression analysis revealed that the Sips isotherm model provides a better correlation for Cr(VI) adsorption onto MAC. The maximum adsorption capacities, at 25 °C, depends on the conditions of preparation of the adsorbent, and were noted to be 60 mg/g for AC and 35, 44 and 66 mg/g for MAC-600, MAC-700 and MAC-800, respectively. The pseudo second-order model best fit the adsorption kinetics. The magnetic property in MAC ensured easy separation of adsorbent using a magnet, after adsorption from the aqueous solution.

We demonstrate a potential optical thermometric material, Pr3+-doped triple-layered perovskite Na2La2Ti3O10 microcrystals, which promises a remarkable performance in temperature sensing over a wide temperature range (125-533 K), with a maximum relative sensitivity of 2.43% K-1 at 423 K. Both temperature and high-pressure dependent photoluminescence measurements were performed for this compound. It turns out that the Pr3+-Ti4+ intervalence charge transfer state is the primary cause for the very efficient thermometric characteristics in the 296-533 K range. In the 125-300 K range, 3P1 and 3P0 levels of Pr3+ can be exploited as thermally coupled energy levels for temperature sensing with high sensitivity at and below room temperature. A significant enhancement of the Pr3+ ions' luminescence observed in the 4.5-300 K range is ascribed to an efficient, thermally activated energy transfer process from the host to Pr3+ ions. Carrier recombination on Pr3+ related hole traps was proposed in the studied system. The thermoluminescence properties are investigated, and possible mechanisms for the interpretation of the experimental results are discussed as well. This work may provide a perspective approach to design a high-performance, self-calibrated optical thermometer operating over a wide temperature range.

Highly reduced (at 500 and 600 °C) 1 wt% Pd/Al2O3 samples showed remarkable isomerization selectivity in n-hexane conversion, >80%, in agreement with previous reports. The catalytic behavior of highly reduced Pd/Al2O3 becomes typical of platinum, the metal regarded as unique in alkane isomerization. Although not detected in low metal loaded catalysts, Pd-Al species evidenced by formation of Pd-Al alloys in 5 wt% metal loaded catalysts appear essential active sites responsible for n-hexane isomerization. Other possible reasons (contribution from alumina acidity and changes in the structure of metal surface) were analyzed and discarded. A mechanistic rationale for the improvement of n-hexane isomerization is outlined.

Nominally 45 nm GaN:Mg/ 5 nm (Ga,Mn)N / 45 nm GaN:Mg trilayers structures prepared by molecular beam epitaxy on GaN-buffered Al2O3 substrates are investigated to verify whether the indirect co-doping by holes from the cladding layers can alter the spin-spin interaction in (Ga,Mn)N. The four investigated structures, differing with the Mg doping level, are carefully characterized at the nanoscale by HRTEM, EDX, and by SIMS. HRTEM decisively excluded a presence of foreign Mn-rich phases. The structures, up to medium Mg doping, show no Mg over-doping effects. Magnetic studies of these structures are aided by the employment of a dedicated experimental approach of the in situ compensation of the magnetic contribution from the substrate, allowing up to about fifty-fold reduction of this contribution. This technique, dedicated to these structures, simultaneously provides a tenfold reduction of temporal instabilities of the magnetometric unit and lowers the experimental jitter to merely $5 \times 10^{-7}$~emu at 70~kOe, vastly increasing the precision and the credibility of the results of the standard integral SQUID magnetometry in high magnetic fields. The magnetic characteristics of the trilayers structures established here prove identical with the already known properties of the thick (Ga,Mn)N single layers, namely (i) the low temperature ferromagnetism among Mn$^{3+}$ ions driven by superexchange and (ii) purely paramagnetic response at higher temperatures. The possible cause of the lack of any effects brought about by the adjacent Mg-doping is a presence of residual Mn in the cladding layers, resulting in the deactivation of the p-type doping intended there. This finding points out that a more intensive technological effort has to be exerted to promote the co-doping-driven carrier-mediated ferromagnetic coupling in Mn-enriched GaN, especially at elevated temperatures., 16 pages, 6 figures

Transmission electron microscopy (TEM) is used for the study of interfaces in two HgTe/HgCdTe single quantum-well (QW) structures grown by molecular beam epitaxy on GaAs substrates. The studies are conducted in bright-field and scanning/high-angle annular dark field modes. The effect of the growth mode on the sharpness of interfaces in the QWs is investigated. Effective in situ ellipsometric control over chemical composition and thickness of the layers constituting the QW structures is demonstrated.

Field emission from materials at high electric fields can be associated with unfavorable or even destructive effect on the surface of the investigated cathode. The impact of high voltage electric power supply causes locally very strong electric fields focusing on the cathode surface. It causes a number of phenomena, which can adversely affect the morphology and the structure of the cathode material. Such a phenomenon is, for example, peeling of an emissive layer from the substrate or its burnout. It results in tearing of the layer and a decrease or loss of its ability to electrons emission. The cold cathodes in a form of CNT films with various CNTs superficial distribution are obtained by physical vapor deposition followed by chemical vapor deposition. CNTs are catalyzed in pyrolytic process with xylene (CVD), by Ni in a form of nanograins (few nm in size) placed in carbonaceous matrix. These films are built of emissive CNTs - carbonaceous film deposited on different substrates. In this work, the morphology and topography of superficial changes resulting from external electric field in such films were investigated.

Well-aligned ZnO nano/micro-rods with identical crystallographic orientation were synthesized on a c-plane GaN template, using a microwave-assisted hydrothermal method at 50 °C for duration of 2 min. The ZnO nanorods exhibited true epitaxial growth, in contrast to most of the previously reported methods, which involve nucleation on a ZnO buffer layer pre-deposited on the substrate. Homogeneous in-plane alignment as well as the c-axis orientation were confirmed by X-ray diffraction measurements and TEM analysis. More importantly, in the photoluminescence spectra of the nanorods a strong, narrow excitonic emission and an extremely weak deep level emission were observed, indicating high optical quality. The diameter was controlled by adjusting pH of the solution used in the growth process. The main achievement of the research was the opportunity to obtain oriented, high quality ZnO nano/microrods, using a surprisingly quick, cheap, and safe growth process, without the use of toxic substances or ultra-high purity compounds.

In this paper, nano-hybrid particles of Ag@Fe2O3 based on O-carboxymethylchitosan were successfully synthesized using different reducing agents (NaBH4, sucrose) and without reducing agent. The smallest silver nanoparticles were those prepared without reducing agent (∼5±3nm). The average size of silver particles prepared with NaBH4 is around 5-15nm, and for samples prepared with sucrose, the average particle size is 10-25nm. The magnetization curves are roughly reversible, indicating that γ-Fe2O3 nanoparticles transit to a superparamagnetic state. Nanocomposites subjected to antimicrobial tests showed great antimicrobial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria, and good activity against the yeast Candida albicans and resistant strains of Staphylococcus aureus. The antibacterial behavior as a function of time was investigated in microbial growth kinetics, and the best nanocomposite was the one without reducing agent, which completely inhibited microbial growth for 48h.

This work describes the chemical formation of composites based on different carbon nanostructures, such as single-walled carbon nanotubes, multi-walled carbon nanotubes, single-layer graphene oxide and p-type conducting polyazulene. The composite materials were synthesized in ethanol solution containing an appropriate amount of carbon nanostructures, azulene and ferric chloride as an oxidizing agent. The main attention was given to the electrochemical properties of these materials and their capacitance performance. The type of nanostructures influenced the morphology of the synthesized polyazulene. Thus, the relationship between the type of nanostructures present in the composite and its morphology and the electrochemical and stability properties were studied. The highest specific capacitance of 649 F g-1 was obtained for the SWCNT/PAZ composite. This value is nine times higher than the specific capacitance of pristine polyazulene synthesized under the same conditions. The SLGO/PAZ composite exhibited the lowest specific capacitance of 53 F g-1. However, this value was improved by approximately 77% by thermal treatment of the composite material at high temperature, resulting in an increase in the BET surface area as well as an increase in conductivity after heat treatment.

Epitaxial ZnO films implanted with ytterbium have been studied by combination of channeling Rutherford backscattering spectrometry and Hall measurements. This approach is able to shed more light onto the difficult problem of optical activation of Yb implanted into the ZnO lattice. ZnO films grown by atomic layer deposition on a GaN/Al 2 O 3 substrate were implanted with Yb + ions to the fluences of 5 × 10 14 , 1 × 10 15 and 5 × 10 15 at./cm 2 . RBS/c spectra show that for as implanted samples the fraction of implanted Yb ions occupying substitutional lattice positions amounts to 72%, 54% and 22%, respectively. Annealing under an ambient atmosphere at 800 °C leads to a partial recovery of the crystal lattice but also substantially reduces substitutional fraction of Yb atoms. Photoluminescence studies on the as-implanted samples revealed a very weak luminescent peak in the near-infrared region, which slightly increases with a fluence. The annealing process leads to optical activation of Yb 3 + ions and significantly increases the previously observed the near-infrared inter-ionic emission. The results obtained from Hall measurements indicate that after implantation Yb ions are mainly in the 2 + state and are transformed to the optically active 3 + state as a result of annealing. It suggests that the process of optical activation via annealing is related not only to lattice recovery, but also to Yb diffusion from substitutional to interstitial positions, where Yb ions are in the optically active 3 + state.

The partially-relaxed heterogeneous GaInNAs layers grown on GaAs substrate by atmospheric pressure vapor phase epitaxy (AP-MOVPE) were investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The planar-view TEM image shows a regular 2D network of misfit dislocations oriented in two orthogonal 〈1 1 0〉 crystallographic directions at the (0 0 1) layer interface. Moreover, the cross-sectional view TEM image reveals InAs-rich and V-shaped precipitates in the near surface region of the GaInNAs epitaxial layer. The resultant undulating surface morphology, known as a cross-hatch pattern, is formed as observed by AFM. The numerical analysis of the AFM image of the GaInNAs layer surface with the well-defined cross-hatch morphology enabled us to determine a lower bound of actual density of misfit dislocations. However, a close correspondence between the asymmetric distribution of interfacial misfit dislocations and undulating surface morphology is observed.

Amorphous FeCrNi/a-C:H coatings are deposited by pulsed magnetron sputtering of austenitic stainless steel in argon/acetylene atmosphere. High-resolution transmission electron microscopy, electron energy loss spectroscopy and energy dispersive X-ray mapping reveal a pronounced nanotubular structure consisting of metallic cores that thread along the film growth direction and are encapsulated by amorphous carbon shells in a cream-roll fashion. The coatings exhibit excellent mechanical, tribological, and anti-corrosion properties.

Three series of glasses of the Li2O-FeO-V2O5-P2O5 system were thermally nanocrystallized and their microstructure was studied, at a nanometer resolution by transmission electron microscopy (TEM). Those observations were complemented by DTA and XRD studies on the same materials. It was shown that appropriate heating of the as-received glasses leads to formation of crystalline nanosize grains embedded in the glassy matrix. Average size of those grains reached even a few nm, was much smaller than that reported for LiFePO4-based nanostructured materials obtained by other methods. The crystal structure of most nanograins was identified as that of the LiFePO4 olivine, but some grains of the Nasicon-like Li3V2(PO4)3 phase were also present. The presence of both phases was confirmed independently by XRD patterns. Due to small size of crystalline grains (down to ca 5 nm) the interfacial regions around them occupy an important fraction of the total volume of the material and their properties can strongly influence the effective properties of the whole material. We have postulated that the defective nature of interfacial regions leads to an increased concentration of Fe2 +/Fe3 +, V4 +/V5 + or V3 +/V4 + aliovalent pairs, crucial for a small polaron hopping mechanism of the electronic transport, and to an enhanced electrical conductivity. The presence of highly conducting interfacial regions in the system where either the glass matrix and both crystalline phases (LiFePO4 and Li3V2(PO4)3) are very poor conductors is the main cause of the observed strong enhancement of the electrical conductivity of the heat-treated glasses of the Li2O-FeO-V2O5-P2O5 system.

In this work, we comprehensively investigate and discuss the structural, magnetostatic, dynamic, and magnetoresistive properties of epitaxial Co/Mo superlattices. The magnetization of the Co sublayers is coupled antiferromagnetically with a strength that depends on the thickness of the nonmagnetic Mo spacer. The magnetization and magnetoresistance hysteresis loops clearly reflect interlayer exchange coupling and the occurrence of uniaxial magnetic anisotropy induced by the strained Co sublayers. Upon accounting for a deviation of the sublayer thicknesses from the nominal value, theoretical modeling, including both micromagnetic and macrospin approaches, precisely reproduces experimental magnetic hysteresis loops, magnetoresistance curves, and ferromagnetic resonance dispersion relations. The Mo spacer thickness as a function of the interlayer magnetic coupling is determined as a fitting parameter by modeling the experimental results.

The purpose of this study was to synthesize a new magnetic material with antimicrobial properties, incorporated into a biopolymer and containing silver nanoparticles (Ag NP) prepared extract of Eugenia umbelliflora as a reducing agent. Silver nanoparticles incorporated into magnetic nanocomposite O-carboxymethylchitosan/y-Fe

Elemental tin in the α-phase is an intriguing member of the family of topological quantum materials. In thin films, with decreasing thickness, α-Sn transforms from a three-dimensional (3D) topological Dirac semimetal (TDS) to a two-dimensional (2D) topological insulator (TI). Getting access to and making use of their topological surface states is challenging and requires interfacing to a magnetically ordered material. Here, we report the successful epitaxial growth of α-Sn thin films on Co, forming the core of a spin-valve structure. We carried out time- and element-selective ferromagnetic resonance experiments to investigate the presence of spin pumping through the spin-valve structure. We applied a rigorous statistical analysis of the experimental data using a Landau-Lifshitz-Gilbert-Slonczewski equation based model. A strong exchange coupling contribution was found, however no unambiguous proof for spin pumping. Nevertheless, the incorporation of α-Sn into a spin-valve remains a promising approach given its simplicity as an elemental TI and its room temperature application potential.

The electrochemical properties of a three-component composite containing polypyrrole, multiwalled carbon nanotubes and tetra(n-octyl)ammonium bromide as a binder have been investigated. The electrochemical behavior of this system depends on the relative amounts of the components within the composite. In the positive potential range, pseudo-capacitive behavior related to the polypyrrole oxidation is observed. The capacitance is enhanced due to the large surface area of the carbon nanotube substrate. Additionally, a contribution of double layer capacitance of multiwalled carbon nanotubes component leads to the capacitance increase. In consequence, high specific capacitance of approximately 600 F g−1 was obtained for this material. This value is about three times higher in comparison for the polymer deposited at the surface of bare gold electrode. The presence of tetra(n-octyl)ammonium bromide enhances the electrochemical and mechanical stability of the composite. The capacitance behavior of ternary composite is also more stable during cyclic charging/discharging processes in comparison to the polypyrrole film or polypyrrole/multiwalled carbon nanotube composite.

Nanoparticles were used to remove the anionic dye Remazol Red 198 (RR198) from aqueous solution by microwave-assisted systems. Adsorption of RR198 on OCh-ML by the microwave-assisted method was investigated with respect to pH, initial dye concentration, temperature, irradiation time, and microwave power. The microwave-assisted process decreases the time required for adsorption of the dye. Removal of the dye was optimized using a three-factor Box–Behnken design, and temperature and microwave power proved to be more influential in dye adsorption than irradiation time. Discoloration of the solution occurs by adsorption of the dye onto the surface of the OCh-ML and not by degradation of the RR198. The tests for phytotoxicity to lettuce seeds showed decreasing toxicity after adsorption of the dye for both adsorption systems. The total power consumed in microwave-assisted was the lower compared to batch method.

The preparation method and some properties of C-Pd multilayered film proper for hydrogen sensing applications are presented. C-Pd multilayered films were obtained by physical vapor deposition (PVD) method by evaporation from of fullerenes (C 60 ) and palladium acetate form two separated sources. The cross-sectional TEM observations were performed for the samples prepared with the use of focused ion beam (FIB) method. EDX spectroscopy was used to obtained information of the element depth composition of the sample. It was found that the depth modulation of Pd and C concentration is characteristic for all the samples. Simple model of Pd segregation based on diffusion and nucleation explains some features of this multilayers structure. All studied samples were sensitive to hydrogen.

New synthesis of solution processable kesterite and kesterite-phenoxazine nanopowders were presented. The direct band-gap semiconductor Cu2ZnSnS4 has attracted the attention of many due to its large absorption coefficient (α > 104 cm-1) and (optical) band-gap energy close to the optimal value for solar light conversion (1.4-1.6 eV). The presence of a kesterite nanocrystal structure has been investigated and confirmed by (HR)TEM, X-ray powder diffraction, EDX and EXAFS measurements. Low-temperature photoluminescence (PL) measurements indicate the absence of PL in the Cu2ZnSnS4 nanocrystals. Electrochemical studies helped to prove that an inorganic-organic heterojunction of nanokesterite-phenoxazine was obtained. Device studies showed a two fold improvement in efficiency upon addition of a kesterite or phenoxazines-kesterite layer.

Structural analysis of epitaxial layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor (DMS), together with investigations of their magnetotransport properties, has been thoroughly performed. The obtained results are compared with those for the reference (Ga,Mn)As layers, grown under similar conditions, with the aim to reveal an impact of Bi incorporation on the properties of this DMS material. Incorporation of Bi into GaAs strongly enhances the spin-orbit coupling strength in this semiconductor, and the same has been expected for the (Ga,Mn)(Bi,As) alloy. In turn, importantly for specific spintronic applications, strong spin-orbit coupling in ferromagnetic systems opens a possibility of directly controlling the direction of magnetization by the electric current. Our investigations, performed with high-resolution X-ray diffractometry and transmission electron microscopy, demonstrate that the (Ga,Mn)(Bi,As) layers of high structural quality and smooth interfaces can be grown by means of the low-temperature molecular-beam epitaxy method, despite a large difference between the sizes of Bi and As atoms. Depending on the applied buffer layer, the DMS layers can be grown under either compressive or tensile misfit strain, which influences their magnetic properties. It is shown that even small 1% Bi content in the layers strongly affects their magnetoelectric properties, such as the coercive field and anisotropic magnetoresistance.

A new tool, PyHoLo software, was developed to help automate the process of determining magnetic field B from a series of holograms, registered at different environmental conditions (e.g. for upside and downside orientations of a sample in a specimen holder). This procedure involves translating single holograms into phase shift of electron wave, but also alignment of holograms (i.e. shift, rotation, magnification) and finally calculation of magnetic field in an area selected for investigation. PyHoLo gives functionality for performing all those steps without having to refer to different programs and tools. The workflow and results of this procedure are discussed using as an example sample of FeCuSiB. Program summary Program title: PyHoLo CPC Library link to program files: http://dx.doi.org/10.17632/n4rgzbnbpw.1 Licensing provisions: GNU General Public License 3 Programming language: Python Nature of problem: (1) Determination of electric and magnetic fields in a sample on the basis of electron holograms, registered on transmission electron microscope during off-axis holography experiment. (2) Alignment of electron holograms acquired for different sample orientations and at different external conditions. Solution method: PyHoLo adapts procedures for all steps required to translate experimental holograms into electric and magnetic signals, i.e. restoration of total phase shift, alignment of electron holograms (shift, rotation, magnification, warping), phase separation. There is no need to refer to different tools and programs. Additional comments: PyHoLo requires Python 3.6 or newer and a number of external libraries to work (see README or manual for details). PyHoLo is a constant work in progress, developed by only one person, so it might be a little rough around the edges. References: For instructions on installation and execution of PyHoLo see README.txt (provided with the source files).

Properties of palladium nanograins obtained by sedimentation of a soluted C-Pd film prepared by PVD method are presented. These properties were studied using SEM and TEM methods. Dissolved films were prepared by PVD method and after dissolving, they were fractionated to obtain different parts classified with palladium nanograins diameters. Several classes of diameters were determined: below 20 nm, between 20 and 100 nm and above 100 nm. The defects and triple junction were observed. Multishell carbonaceous structures were found in the big and medium size Pd nanograins.

A rapid development of solar cells has been observed within recent years. Semiconducting materials based on Cu2ZnSnS4 with the kesterite structure offer a promise of low-cost and environmentally friendly solar cells. The energy gap of Cu2ZnSnS4, which is about 1.5 eV, can be optimized with addition of organic ligands. We report a method of obtaining kesterite nanopowders with grain diameter of approximately 5 nm via solution synthesis using metal chlorides and sulfur in oleylamine at 230 °C. The ligand exchange for diphenylamine upshifted the value of the bandgap to 2.2 eV, which makes it a promising material for an upper layer in tandem photovoltaic devices.

Dielectric films, such as hafnium dioxide (HfO 2 ), aluminum oxide (Al 2 O 3 ), zirconium dioxide (ZrO 2 ), titanium dioxide (TiO 2 ) and their composite layers are deposited on polycrystalline and amorphous substrates by the atomic layer deposition (ALD) method. We demonstrate that the use of this technology guarantees a uniform and controlled surface coverage in the nanometer scale at low temperatures (in our case, below 100 °C). Modification of the composition of oxide layers allows the deposition of materials with quite different absorption coefficients, refractive indexes and dielectric constants. In particular, we demonstrate structural, electrical and optical properties of dielectric layers and test metal-oxide-semiconductor structures with these oxide materials. Our good quality dielectric layers, obtained at low-temperature ALD, are characterized by a high dielectric constant (above 10), very smooth surface, wide energy gap (above 3 eV), low leakage current (in the range of 10 − 8 A/cm 2 at 1 V), high dielectric strength (even 6 MV/cm) and high refractive indexes (above 1.5 in the visible spectral range).

This study describes a new method of passivating ZnO nanofiber-based devices with a ZnS layer. This one-step process was carried out in H2S gas at room temperature, and resulted in the formation of core/shell ZnO/ZnS nanofibers. This study presents the structural, optical and electrical properties of ZnO/ZnS nanofibers formed by a 2 nm ZnS sphalerite crystal shell covering a 5 nm ZnO wurtzite crystal core. The passivation process prevented free carriers from capture by oxygen molecules and significantly reduced the impact of O2 on nanostructure conductivity. The conductivity of the nanofibers was increased by three orders of magnitude after the sulfidation, the photoresponse time was reduced from 1500 s to 30 s, and the cathodoluminescence intensity increased with the sulfidation time thanks to the removal of ZnO surface defects by passivation. The ZnO/ZnS nanofibers were stable in water for over 30 days, and in phosphate buffers of acidic, neutral and alkaline pH for over 3 days. The by-products of the passivation process did not affect the conductivity of the devices. The potential of ZnO/ZnS nanofibers for protein biosensing is demonstrated using biotin and streptavidin as a model system. The presented ZnS shell preparation method can facilitate the construction of future sensors and protects the ZnO surface from dissolving in a biological environment.

Nitrogen-doped and undoped ZnO films were grown by thermal atomic layer deposition (ALD) under oxygen-rich conditions. Low-temperature photoluminescence spectra reveal a dominant donor-related emission at 3.36 eV and characteristic acceptor-related emissions at 3.302 and 3.318 eV. Annealing at 800 °C in oxygen atmosphere leads to conversion of conductivity from n- to p-type, which is reflected in photoluminescence spectra. Annealing does not increase any acceptor-related emission in the undoped sample, while in the ZnO:N it leads to a considerable enhancement of the photoluminescence at 3.302 eV. The high resolution cathodoluminescence cross-section images show different spatial distribution of the donor-related and the acceptor-related emissions, which complementarily contribute to the overall luminescence of the annealed ZnO:N material. Similar area of both emissions indicates that the acceptor luminescence comes neither from the grain boundaries nor from stacking faults. Moreover, in ZnO:N the acceptor-emission regions are located along the columns of growth, which shows a perspective to achieve a ZnO:N material with homogeneous acceptor conductivity at least at the micrometer scale.

The Lorentz off-axis electron holography technique is applied to study the magnetic nature of Mn rich nanoprecipitates in (Mn,Ga)As system. The effectiveness of this technique is demonstrated in detection of the magnetic field even for small nanocrystals having an average size down to 20 nm., 11 pages, 3 figures

In this paper, nano-hybrid particles of Ag@Fe

Addition of some other metals to platinum causes significant increase of its catalytic activity towards ethanol electrochemical oxidation. This may be caused by different adsorption of CO molecules on the surface of the catalyst, and hence different resistance of the M@Pt nanostructures to poisoning by CO. In this work we attempt to verify this hypothesis analyzing vibrational spectra of CO adsorbed on various metal nanoparticles. Au@Pt nanoparticles revealing significantly higher catalytic activity towards ethanol oxidation than one-element Pt nanoparticles have been synthesized. Surface-enhanced infrared absorption (SEIRA) spectra of CO adsorbed on Au@Pt and Pt nanoparticles have been measured. Obtained spectra were very similar, which suggests that the higher catalytic activity of Au@Pt nanoparticles is rather not caused by different adsorption of CO molecules on Pt and Au@Pt nanoparticles. We suppose that better performance of core–shell M@Pt nanoparticles than one elements Pt nanoparticles towards ethanol electrochemical oxidation can be explained as follows: core–shell nanoparticles are probably much more defected than one-element nanoparticles, hence the M@Pt nanoparticles posses greater number of active sites (kinks, adatoms, and so on) for ethanol electrochemical oxidation. Analysis of the catalytic activity and CO adsorption have been also carried out for other nanoparticles including: Sn@Pt, Pb@Pt, Pd, Au@Pd, Sn@Pd and Pb@Pd. Density functional theory (DFT) calculations of C O modes for CO adsorbed on tetrahedral Pt10 or Pd10 clusters with different metal–metal distance have been also performed.

A rapid development of photovoltaics has been observed recently. Permanent interest in new cheap and efficient photovoltaic devices stimulates a constant search for new semiconductor materials and structures. The success of materials based on CIGS (CuIn1–xGaxSe2) is limited by the prohibitive prices of the elements In and Ga. A family of quaternary semiconducting materials of the Cu2ZnSnS4 type, crystallizing mainly in the kesterite structure, offers a promise of new cheap photovoltaic materials. Kesterite is manufactured from nontoxic and naturally abundant materials. The energy gap of Cu2ZnSnS4 is about 1.5 eV, and the absorption coefficient of this direct-band-gap material is α > 104 cm–1 for photon energies higher than the energy gap. In this paper, we report a method of obtaining free-standing single crystals of kesterite (Cu2ZnSnS4).

GaInNAs alloys are mostly used as an active part of light sources for long wavelength telecom applications. Beside this, these materials are used as thin quantum wells (QWs), and a need is to grow thick layers of such semiconductor alloys for photodetectors and photovoltaic cells applications. However, structural characterization of the GaInNAs layers is hindered by non-homogeneity of the In and N distributions along the layer. In this work the challenges of the structural characterization of doped thick GaInNAs layers grown by atmospheric pressure metalorganic vapour phase epitaxy (APMOVPE) will be presented. K e y w o r d s: dilute nitrides, GaInNAs, composition determination, HRXRD

The paper describes the preparation and characteristics of films composed of Pd nanograins placed in carbonaceous matrix. Films were obtained in PVD (Physical Vapor Deposition) process from two sources containing: the first one - fullerene powder and the second one - palladium acetate. The topographical, morphological and structural changes due to different parameters of PVD process were studied with the use of Atomic Force Microscopy and Scanning Electron Microscopy, whereas the structure was studied with the application of the Transmission Electron Microscopy and Fourier Transform Infrared Spectroscopy methods. It was shown that topographical changes are connected with the decomposition ratio of Pd acetate as well as the form of carbonaceous matrix formed due to this decomposition. Palladium nanograins found in all films exhibit the fcc structure type and their diameter changes from 2 nm to 40 nm depending on the PVD process parameters.

Here, we demonstrate heteroepitaxial growth of MgO/TiN thin films on flexible metal foil of copper substrates using pulsed laser deposition. X-ray and electron diffraction measurements revealed that the epitaxial MgO/TiN bilayer was oriented along [002] direction. The large mismatch between TiN film and Cu substrate was effectively reduced by the 5/6 and 6/7 variations of domains. Despite the local irregularity of misfit dislocations at TiN/Cu, the domain-matching epitaxy paradigm is a remarkably accurate theory. MgO/TiN bilayer is chemically homogeneous and Mg, Ti, or Cu atoms do not segregate into the low-angle grain boundaries regardless of MgO/TiN films thickness. Thus, it appears that thickness may be reduced up to the value in which TiN fully covers the rough surface of Cu tape. Unfortunately, issues related to the presence of in-plane TiN contraction, probably generated by the difference in thermal expansion coefficient, and the origin of misfit dislocations irregularity at TiN/Cu interface remain unresolved. Our findings can make a substantial contribution to further research on Cu-based coated conductors and help in better understanding the ways that MgO/TiN bilayer are grown on Cu tape.