International Journal of Nanoscience

We consider the problem of confining the famously elusive Dirac-like quasiparticles, as found in some recently discovered low-dimensional systems. After briefly surveying the existing theoretical proposals for creating bound states in Dirac materials, we study relativistic excitations with a position-dependent mass term. With the aid of an exactly-solvable model, we show how bound states begin to emerge after a critical condition on the size of the mass term is met. We also reveal some exotic properties of the unusual confinement discovered, including an elegant chevron structure of the bound state energies as a function of the size of the mass.

The photoluminescence of gold nanorod-quantum dots complexes was investigated in order to find optimal conditions for the luminescence enhancing. The number of quantum dots and polyelectrolyte layers on the gold nanorod surface in these complexes were considered as main factors in the enhancement.

Photoluminescent properties of CdSe/ZnS nanocrystals (quantum dots, QDs) in complexes with elongated gold nanoparticles was found to be dependent on the effective refractive index of the medium. It has been experimentally shown that changes in the refractive index make possible to increase the photoluminescence intensity by several times.

We present the quantitative analysis of the photoluminescence (PL) obtained for semiconductor TOPO-capped CdSe/ZnS QDs in solutions at 77–293K. The PL bands are approximated more accurately when assuming the superposition of at least two Gaussian components differing considerably in the linewidth (FWHM) and having different nature.

The attachment of pyridyl substituted porphyrin molecule to the surface of CdSe/ZnS quantum dots in solutions is realized in the competition with capping ligand TOPO molecules resulting in the specific change of photoluminescence for the quantum dots across the temperature range of 77–290K. We have shown that fixation of alone quantum dots or quantum dot-porphyrin nanoassemblies on quartz substrate changes significantly temperature dependence of photoluminescence. In contrast to the samples in a glass-forming solution no phase transition of the TOPO capping layer was observed upon removal of the capping layer.

The effects of relative positions of Se atoms in a monomolecular layer of MoS${}_{1.5}$Se${}_{0.5}$ have been studied. It is demonstrated that the distribution of Se atoms between top and bottom chalcogen planes is most energetically favorable. For a more probable distribution of Se atoms this monolayer alloy is a direct semiconductor with the fundamental bandgap of 2.35eV. We have also evaluated the optical band gaps of the alloy at 77K (1.86eV) and room temperature (1.80eV), which are in a good agreement with the experimentally measured bandgap of 1.79eV.

An impact of positions of Te atoms substituting W atoms in two-dimensional WS₂/WSe₂ heterostructures on their electronic properties is investigated by theoretical simulation. The substitution of W by Te tends to reduce the energy band gap and can lead to metallic properties depending on the impurity position and concentration.

Calculations of chemical reactions between C₂₀, C₆₀, hydrogen and water molecules are carried out using the PM3 method. Reactions with a hydrogen release at room temperature and atmospheric pressure are identified by the Gibbs energy change. The hydrogen release can be raised by increasing the number of water molecules in chlorine-assisted decomposition of fullerenes. Calculations of the Gibbs energy of chemical reactions involving water molecules between two parallel curved graphene sheets are carried out using DFT with the functional UB3LYP. During pumping between plates of an electric capacitor designed from curved graphene sheets, the water vapor with the assistance of external illumination is enriched by electrically neutral hydroxyl groups (OH)⁰.

Isobaric heat capacities of C${}_{60}$(OH)${}_{40}$ and C${}_{70}$(OH)${}_{12}$ fullerenols were measured using adiabatic calorimetry in the temperature range of 0–320K along with standard thermodynamic functions: $S_m$, [${\mathrm{\Phi }}_m(T)-{\mathrm{\Phi }}_m(0)$] and [$H_m(T)-H_m(0)$]. Furthermore, the molar entropy of formation and the molar third law entropy of C${}_{60}$(OH)${}_{40}$ and C${}_{70}$(OH)${}_{12}$ in crystalline state at 298.15K were calculated.

One of the most promising platforms to implement quantum technologies are coupled electron-nuclear spins in solids in which electrons can play a role of “fast” qubits, while nuclear spins can store quantum information for a very long time due to their exceptionally high isolation from the environment. The well-known representative of such systems is the “nitrogen-vacancy” (NV) center in diamond coupled by a hyperfine interaction to its intrinsic ${}^{14}$N/${}^{15}$N nuclear spin or to ${}^{13}$C nuclear spins presenting in the diamond lattice. More recently, other paramagnetic color centers in diamond have been identified exhibiting even better characteristics in comparison to the NV center. Essential prerequisite for a high-fidelity spin manipulation in these systems with tailored control pulse sequences is a complete knowledge of hyperfine interactions. Development of this understanding for one of the new color centers in diamond, viz., neutral “silicon-vacancy” (SiV⁰) color center, is a primary goal of this paper, in which we are presenting preliminary results of computer simulation of spatial and hyperfine characteristics of SiV⁰ center in H-terminated clusters C${}_{84}$[SiV⁰]H${}_{78}$ and C${}_{128}$[SiV⁰]H${}_{98}$.

Structure and energy calculations of modified complexes of single-walled carbon nanotubes and fullerenol C${}_{60}$(OH)${}_{24}$ with cisplatin have been performed using the quantum chemical method at the DFT/B3LYP/SV/Lanl2DZ level. The nanotubes were modified with COOH groups at the end and sidewall of the nanotube and cisplatin molecules. The dependence of their structure on the presence of a solvent was established.

Germanium-vacancy (GeV) centers are now studied extensively due to perspectives of their applications in quantum information processing, nanometrology and nanoscale magnetic resonance imaging. One of the important requirements for these applications is a detailed understanding of the hyperfine interactions in such systems. Quantum chemistry simulation of the negatively charged GeV⁻ color center in diamond is the primary goal of this paper in which we present preliminary results of computer simulation of the bulk H-terminated cluster C${}_{69}$[GeV⁻]H${}_{84}$, as well as of the surface cluster C${}_{64}$[GeV⁻]H${}_{68}$_(100)_H${}_{11}$ having one dangling bond at (1 0 0) surface using the DFT/PW91/RI/def2-SVP level of theory.

By means of ab initio calculations, we have estimated stability of 2D Me${}_{2}X$ ($\mathrm{\text{Me}}=\mathrm{\text{Mg}}$, Ca, Sr, Ba and $X=\mathrm{\text{Si}}$, Ge, Sn) in the T and Td phases, which are similar to the ones of 2D transition metal chalcogenides, in addition to their phonon spectra. The T phase is found to be more stable for 2D Ca${}_{2}X$, Sr${}_{2}X$ and Ba${}_{2}X$, whereas the Td phase is predicted to be the ground state for 2D Mg${}_{2}X$. We have also discussed that imaginary frequencies in the calculated phonon spectra of 2D Me${}_{2}X$, which appeared in the vicinity of the $\mathrm{\Gamma }$ point, were not necessarily associated with the dynamic instability.

The crystal structure, optical and electrical properties of Ca silicide films grown by MBE and RDE processes on Si(1 0 0) and Si(1 1 1) substrates have been compared. Optical spectroscopy studies, including Raman spectroscopy, have shown two silicide phases: CaSi₂ and CaSi. The RDE-grown film on Si(1 1 1) substrate with the CaSi₂ phase is characterized by higher transparency than MBE-grown films. Therefore, the CaSi₂ RDE-grown phase is found to be predominant and has a lower absorption in the IR region of the spectrum. After 1.5-year storage of Ca silicide film oxidation, partial destruction of the CaSi₂ phase and conservation of the CaSi layer were revealed by TEM and HRTEM analyses. The complex behavior of magnetoresistance versus magnetic induction, including positive and negative curves, has been found for the MBE-grown films in the temperature range of 1.3–300K. The RDE-grown CaSi₂ film has displayed a semiconducting type of the magnetoresistance.

We analyze the magnetization versus magnetic field curves of Fe-based nanoparticles embedded inside CNT. Measurements were performed at different temperatures and orientations of the magnetic field. We demonstrate that, for the parallel field the magnetic anisotropy dominates and the coherent anisotropy is of great importance at low temperatures. At high temperatures, the exchange coupling becomes stronger, but the coherent anisotropy still occurs. For the perpendicular field, the coherence anisotropy is absent, and the dimensionality of the system reduces to 2D. The results are discussed in the framework of the correlation functions of the magnetic anisotropy axes.

Energy levels of electrons in the semiconductor circular quantum ring are obtained within the framework of perturbation theory in the presence of the Rashba and Dresselhaus spin-orbit interactions and external uniform constant magnetic field. The confinement effect is simulated by the realistic potential well of a finite depth.

Relation between magnetoresistance and magnetization reversal in thin multilayered IrMn–Co/Pd films deposited both on planar and nanoporous substrates is in focus of the present work. Magnetic anisotropy, exchange coupling and mechanisms of magnetic resistivity are discussed.

Dielectric properties of composite materials made of epoxy resin filled with different concentrations of goethite (Fe₂O${}_3\cdot$ H₂O) nanorods and manganese ferrite (MnFe₂O₄) are presented in a wide frequency range. The electrical percolation threshold in these composites is close to 30vol.%. Electrical conductivity in the composites occurs both below and above the percolation threshold due to the finite conductivity of the epoxy resin under high temperatures.

This paper presents a comparative analysis of the magnetization, Kerr and Faraday magneto-optical effects, magnetic force microscopy measurements of CoPt, CoPd, FePd alloy thin films. The films were fabricated by electron-beam evaporation, with the variation of a ferromagnetic material content. A decrease in the size of magnetic domains with an increase of the Co content in CoPt and CoPd films is shown. The presence of two magnetic phases in the films is discussed.

In this paper, we show the possibility of rebuilding of the structure of wave vector surface and the appearance of its local parts with near zero curvature for epsilon-near-zero hyperbolic metamaterials. It is established that when evanescent Bessel light beam falls in special directions related to these local parts, it is transformed into propagating one. The features of transformed beam are analyzed.

In the field of semiconductor nanooptics, copper chalcogenides have challenged a novel direction associated with nontrivial optical features in the near IR range important for applications. We consider this phenomenon in the silica sol–gel derived glasses doped with copper selenide nanoparticles. They were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy and optical absorption spectroscopy. An origin of the near IR optical features is discussed involving both the plasmon resonance concept extended to the self-doping of chalcogenides with a variable stoichiometry and the effect of Cu²⁺ impurity-generated intraband levels providing linear and nonlinear optical response of these materials.

Composite Ag–Cu and Ni–C nanoparticles were synthesized by laser ablation and spark discharge in liquid, respectively. An amplification of the signal during laser induced breakdown spectroscopy was observed after deposition of the nanoparticles on the surface of an aluminum foil. The emission intensity of the laser plume increased from 2 to 20 times depending on the spectral lines used for the measurements. The intensity growth was higher for Ag–Cu nanoparticles.

The electric-field behavior of the resonance features in the photoelectric characteristics of InAs/GaAs heterostructures is studied. We discuss the emission mechanism of the charge carriers excited from InAs quantum dots into the GaAs matrix. It was shown that at the temperature of liquid nitrogen the photocurrent in a strong transverse electric field is only determined by the effect of electron tunneling through the barrier formed at the quantum-dot interfaces. Comparison of the experimental curves with the quasi-classical expression for the tunneling current component and analysis of the potential structure allowed us to specify some parameters of investigated heterostructures. Analysis of the electric-field dependences of the photocurrent-tunneling component revealed resonance peculiarities connected with the local defect states in the vicinity of InAs/GaAs interface.

The theoretical model of electromagnetic transmission through solitary sub-wavelength nanoapertures is considered. The model is based on a rigorous solution of the plane wave diffraction problem by a slot in the perfectly conducting screen of a finite thickness. The local energy of the electric field inside the plane dielectrics arranged behind the screen is used for calculations. The results demonstrate the principal features of the phenomenon that confirms that the diffraction theory can be applied successfully without the concept of surface plasmons.

The effect of the spatial order of a monolayer of monodisperse spherical crystalline silicon nano- and submicrometer-sized particles upon its absorption coefficient is theoretically investigated. The calculation method is based on the quasicrystalline approximation of the theory of multiple scattering of waves and multipole expansion of electromagnetic fields and tensor Green function in terms of vector spherical wave functions. The results can be used for an enhancement of light harvesting in a solar cells design.

The real part of high frequency phononless conductivity was calculated in the pair approximation for a disordered array of densely packed spherical nanogranules. The generalization of the theory of phononless conductivity for systems with hydrogenic impurities to the systems with finite size localization centers reveals that the high frequency conductivity depends on the distribution function $P(w)$ of the distances between the surfaces of granules. This can lead to deviations from the linear frequency dependence of the real part of conductivity ${\sigma }_1(\omega )$. In the vicinity of the frequency ${\omega }_c=2I_0∕\hslash$ ($I_0$ is the pre-exponential factor of the resonance integral) for disordered granular systems, one should expect deviations of ${\sigma }_1(\omega )\sim {\omega }^s$ from universality ($s\approx 1$), associated with weakening of the frequency dependence of ${\sigma }_1(\omega )$, and its nonmonotonicity. With an increase in the size of the granules, nonmonotonicity of ${\sigma }_1(\omega )$ is expected at lower frequencies. This stems from a decrease in the pre-exponential factor $I_0$ of the resonance integral with an increase in the granule size.

The bandgaps of 1.187eV in non-irradiated nanostructured thin films of Cu(In,Ga)Se₂ (CIGSe) and of 1.182eV in those films irradiated with 10keV hydrogen ions were determined using optical transmission and reflection spectroscopy at 4.2K. The observed reduction in the bandgap is assigned to the formation of secondary antisite defect complexes inducing band tails of the density of states in the valence band.

Resistivity, Hall effect and quantum oscillations of magnetoresistance in a two-dimensional electron system at an n-GaAs/Al_0.29Ga_0.71As:Si heterointerface have been investigated under uniaxial compression up to 3.5 kbar along [110] direction in the dark and after illumination by infrared diode at 1.7 K. The observed persistent photoconductivity is connected with the excitation of deep DX centers in the active layer. The electron redistribution between the quantum well and the active layer explains pressure dependence of the electron mobility and concentration fixed after illumination.

An influence of matrix absorbance on electrodynamic coupling in arrays of close-packed plasmonic nanoparticles and on the surface plasmonic resonance absorption (SPRA) band was analyzed with the use of the Mie theory and statistical theory of multiple scattering of waves. A miss of the concentration red shift of the SPRA band in Cu–C₆₀ nanostructures was observed experimentally and explained.

Free charge carrier concentration in arrays of silicon nanowires (SiNWs) with cross-sectional size of the order of 100nm was quantitatively studied by means of the infrared spectroscopy in an attenuated total reflection mode. SiNWs were formed on lightly-doped $p$-type crystalline silicon substrates by metal-assisted chemical etching followed by additional doping through thermoactivated diffusion of boron at 900–1000^∘C. The latter process was found to increase the concentration of free holes in SiNWs up to $(1\text{–}3)\times 10^{19}$cm${}^{-3}$. Potential applications of highly doped SiNWs in thermoelectric energy converters and infrared plasmonic devices are discussed.

In this paper, the chromium ions luminescence in Cr₂O₃/Al₂O₃ nanocomposites has been studied. No photoluminescence from the nanocomposite was observed at room temperature, while at liquid nitrogen temperature the two broad bands were detected at 497 and 665nm caused by $F$- and $F_2$-type oxygen vacancies and Cr${}^{3+}$ and Mn${}^{4+}$impurity centers. The photoluminescence band observed at 616nm is attributed to Cr${}^{6+}$ ions. The excitation of Cr${}^{6+}$ ions occurs at 265 and 375nm, and their formation is the result of Cr${}^{3+}$–Cr${}^{6+}$ redox processes on the surface of Cr₂O₃ crystallites at the annealing temperatures of 400–$900^{\circ }$C.

Stable emulsions of individual n-alkane (n-nonadecane) in water with different average particle size were prepared without surfactants. The phase transition temperatures for n-nonadecane were determined by the dynamic light scattering method. The effect of the n-alkane particle size on the melting and crystallization temperatures was studied. The crystallization temperature significantly decreases for particles smaller than a certain characteristic value.

The irradiation-induced effects in Cu(In,Ca)Se₂ thin films after irradiation with hydrogen ions with dose of $3\times 10^{15}$cm${}^{-2}$ and different energies in the range of 2.5–10keV were studied. Irradiated and nonirradiated thin films were investigated by low-temperature (4.2K) photoluminescence and photoluminescence excitation methods. The appearance of intense bands at $\sim 0.92$eV and 0.77eV in the photoluminescence spectra may be related to radiative recombination on the irradiation-induced defects with deep energy levels in the bandgap of Cu(In,Ca)Se₂ solid solutions. A possible nature of these defects and process of radiative recombination are discussed.

Tunneling transmission of electrons excited by the sun light in the bulk TiO₂ to its surface states is simulated. The model is built for the TiO₂/Si nanostructure. The tunneling transmission coefficient was calculated by the phase functions method. The surface states are considered to be formed due to adsorption of impurities and organic compounds on TiO₂. Energy dependence of the transmission coefficient is influenced by an interference of transmitted and reflected waves under conditions of the complex potential relief.

Monitoring of loss tangent is shown to be a sensitive method allowing control of energy bonds between molecular species in water.

We present the methodologies for developing high-performance thermoelectric materials using nanostructured interfaces by reviewing our three studies and giving the new aspect of nanostructuring results. (1) Connected Si nanocrystals exhibited ultrasmall thermal conductivity. The drastic thermal conductivity reduction was brought by phonon confinement and phonon scattering. Here, we present discussion about the new aspect for phonon transport: not only nanocrystal size but also shape can contribute to thermal conductivity reduction. (2) Si films including Ge nanocrystals demonstrated that phonon and carrier conductions were independently controlled in the films, where carriers were easily transported through the interfaces between Si and Ge, while phonons could be effectively scattered at the interfaces. (3) Embedded-ZnO nanowire structure demonstrated the simultaneous realization of power factor increase and thermal conductivity reduction. The $S^2\sigma$ increase was caused by the interface-dominated carrier transport. The nanowire interfaces also worked as phonon scatterers, resulting in the thermal conductivity reduction.

MoS₂ films on sapphire and SiO₂/Si substrates were fabricated by sulfurization of sputtered Mo precursor films at 900^∘C in a two-zone furnace. Structural, morphological, optical and electrical properties of the films were determined. The films of MoS₂ were successfully grown on the substrates with polycrystalline structures and proposed to be used in electro-optical devices.

There is currently no reliable method for studying interfacial regions within dielectric nanocomposites. The aim of this work was to develop experimental protocols and signal analysis involving Electrostatic Force Microscopy (EFM). Model samples made of spherical nanoparticles deposited on a metallic substrate and covered by two shells were designed and fabricated to simulate the presence of an interphase between a particle and a matrix. EFM performed either with DC or AC gradients detection method proved good sensitivity to certain sample configurations. A quantification of the dielectric permittivity of the intermediate layer was possible, thanks to correlation with finite element numerical simulations. Interfacial states between stacked layers, which can be attributed to film deposition processes, were also evidenced.

Large nanostructures of silicene have been successfully grown on graphene covered 6H-SiC (0001) substrates. The graphene plays an important role to obtain honeycomb structures of silicon in the sp² configuration and acts as an ideal template for 2D materials. The scanning tunneling microscopy images showed nanosheets of silicene with a very small buckling among the Si atoms. Our scanning tunneling spectroscopy confirmed the metallic character of the deposited silicene in excellent agreement with band structure calculations that also exhibit the presence of Dirac cones.

We reported the growth of CZTSSe thin films on Mo-coated SLG substrates by the two-step approach which includes the deposition of precursor films by the magnetron sputtering method at room temperature followed by selenization of the precursor films at 560^∘C. Formation of CZTSSe films with the kesterite structure was confirmed by XRD and Raman spectroscopy analyses. The films are slightly Cu-rich and Zn-deficient. SEM study shown that the films have uniform surface morphology and densely packed structure without any voids and cracks.

Electrochemical deposition of cobalt nanoparticles was used to modify carrier transport properties of single-layered CVD graphene at the SiO₂-on-Si substrate. The structure of graphene with cobalt nanoparticles was analyzed by Raman spectroscopy and scanning electron microscopy. The effect of the deposited cobalt nanoparticles on the sheet resistance of graphene was studied in the temperature range of 4–300K.

We developed and studied facile synthesis of graphitic carbon nitride in macroporous silica glass matrix. Melamine was used as a precursor. The synthesis was performed in a closed air ambience at 400–600^∘C. It was found that the synthesized material was characterized with a broadband room-temperature photoluminescence in the range of 350–750nm with the peak shifting from to 445nm to 702nm when the temperature of the synthesis was increased from $400^{\circ }$C to $575^{\circ }$C while the intensity of the luminescence was decreased. The nature of the luminescent centers and possible applications of the synthesized material are discussed.

Nitrogen and ruthenium co-doped titania films synthesized by sol–gel technique exhibit high photocatalytic activity under both UV and visible light. Incorporation of nitrogen and ruthenium ions in titania lattice is proven by XPS. Both doping agents affected the structural properties of the films.

With the use of sol–gel method BaTiO₃–SiO₂ multilayer structures were fabricated on glass or fused silica substrates employing dipping or spinning procedure. The photonic stop band was observed in the reflection and transmission spectra of the multilayer structure annealed at $450^{\circ }$C. It is redshifted with an increase of the thicknesses of BaTiO₃ and SiO₂ layers. For structures comprising Eu-doped BaTiO₃ layers of different thicknesses photoluminescence with the main band at 614nm was detected. It is characterized with the double-exponential decay with the lifetimes of about 0.5ms and 1.1ms which do not depend significantly on the photonic stop band position.

ZnO nanostructured films doped with Co and Ni deposited by hydrothermal method on silicon substrates covered with undoped ZnO sublayer were studied. SEM images of the films demonstrated them to consist of densely packed vertical nanopillars. Doping ZnO films with Ni or Co at concentrations up to $10^{19}$cm${}^{-3}$ quenches their UV-excited photoluminescence. The doping also leads to the slight ferromagnetic behavior of ZnO.

New fluorescent molecular rotors (FMRs) were developed by modification of the Thioflavin T (ThT) structure via introduction of methyl and methoxy groups. Effects of the substituents on fluorescence properties and twisted intramolecular charge transfer (TICT) rate in the excited state of the molecules were studied using steady-state fluorescence and time-resolved absorption spectroscopy. Quantum chemical calculations of the molecules in the ground and excited states were carried out to aid interpretation of the experimental results. Only cationic forms of ThT derivatives have FMR properties and exhibit viscosity-dependent fluorescence. The TICT rate was found to be affected by the size of the molecular fragments, which experience mutual rotation, dihedral angle $\phi$ between the fragments in the ground state as well as their donor/acceptor properties.

We present ab initio study of structures and properties of silaprismanes Si${}_{2n}$H${}_{2n}$ and their nitro derivatives Si${}_{2n}$H${}_{2n-1}$NO₂ ($n=3$–10). We found that silaprismane Si${}_{10}$H₉NO₂ possesses the highest stability among all studied cages. Attached NO₂ group results in weak decreasing of the HOMO–LUMO gap. The smaller prismanes bind with NO₂ groups more strongly. The comparison between silaprismanes and carbon prismanes is also discussed.

Gold and copper oxide nanoparticles (NPs) were synthesized using pulsed Nd:YAG laser ablation in liquids (acetone and distilled water). The possibility of emission increasing from laser-induced plasma after the deposition of the prepared NPs on a glass surface promising for spectroscopic analysis of transparent samples was demonstrated.

Laser-assisted synthesis of germanium–tin (Ge–Sn) alloy nanoparticles (NPs) using 532-nm laser processing of colloidal solutions produced by laser ablation of Ge in Sn suspension has been demonstrated and studied. Laser-induced rapid heating, subsequent co-melting and re-solidification processes at high cooling rates have been considered to be experimentally achieved at the optimized laser processing parameters. Detailed characterization of the formed Ge–Sn alloys indicated substitution of Sn atoms in the Ge matrix.

Silver plasmonic nanoplatelets functionalized with sodium mercaptoethanesulfonate were electrostatically deposited onto thin films of cationic co-polymers to form a dense planar-oriented layer. We observed a linear dependence of the optical density of as-prepared films versus the amount of tertiary amino groups in the polymeric film. Our novel method allows direct examination of the optical properties and morphology of silver nanoplatelets in the same polymeric film.

By chemical modification of poly(maleic anhydride-alt-1-tetradecene) with different negatively and positively charged groups, we demonstrate how magnitude of zeta potential of encapsulated CdSe quantum dots and their sensitivity to pH can be tuned by varying type and proportion of the negatively and positively charged groups on the surface of quantum dots.

Properties of CdSe nanocrystals (NCs) fabricated in aqueous solutions at relatively mild conditions in the presence of gelatine and stabilized in polymer (gelatine, gelatine + polyvinylpyrrolidone, polyvinyl alcohol) matrices are characterized by Raman, optical absorption and photoluminescence spectroscopies. The effect of heating of the reaction mixture on the average NC size is discussed.

Photoelectrochemical behavior of oleate- and sulfide-capped CdSe QD films fabricated via electrophoretic deposition has been investigated in Na₂SO₃ aqueous electrolyte. The oleate substitution for sulfide led to considerable increase in photocurrent efficiency. Films of the both types show photocurrent switching under 465-nm light irradiation. The photocurrent direction switching potential strongly depends on the particle size demonstrating negative shift of the potential with size: from 0.0V for 2.4nm to $-0.2$V for 6.3nm.

Silvered porous silicon was utilized as an active substrate for a detection of small amounts of meldonium by surface enhanced Raman scattering (SERS) spectroscopy. We were able to detect the meldonium in its water solutions at the concentrations of 10${}^{-2}$–10${}^{-6}$M. Immersion of the silvered porous silicon in the meldonium solutions at the 10${}^{-4}$M concentration and lower led to the dimers’ formation. At the concentrations larger than 10${}^{-3}$M, a greater contribution to the enhancement of the Raman intensity was caused by a chemical mechanism while the smaller amounts were detected mostly due to an electromagnetic mechanism.

Water-soluble potentially biocompatible Au-containing nanocomposites based on the natural polysaccharide arabinogalactan were prepared. They were investigated by electronic and infrared spectroscopies, X-ray diffraction analysis and transmission electron microscopy. Stable zero-valence Au nanoparticles with an average particle size of 5–8nm are formed in the natural macromolecular matrix. The nanocomposites obtained are aggregatively stable and of interest for applications in medicine.

The effect of Al doping on the morphology and sensing properties of ZnO nanorods have been shown. Undoped and Al-doped well-aligned ZnO nanorods have been grown on sputtered ZnO/SiO₂/Si (100) pre-grown seed layer substrate by the hydrothermal method. The molar ratio of dopant (aluminum nitrate) in the solution, [Al/Zn], was varied from 0.1% to 3%. The prepared ZnO nanorods showed preferred orientation $<$0001$>$ and were well aligned vertically. We observed that for 0.5% Al doping the diameter and resistivity of the nanorods became the least, carrier concentration became large. Sensing behavior of the doped samples tested for H₂ gas shows the sensitivity of $\sim 60\%$ at ${250}^{\circ }$C and $\sim 50\%$ at $220^{\circ }$C, respectively.

We present a systematic study of hexangular ZnO nanotube growth using zinc nitrate and NaOH as starting materials by varying solution concentration. ZnO nanotubes were characterized by field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and growth mechanism was discussed. Supersaturation near ZnO surface is higher and leads to the $c$-axis preferential growth. Low-magnification and high-resolution TEM micrographs revealed that best growth conditions for ZnO nanotube arrays were at 5mM zinc nitrate and 1mL of 1M NaOH. The growth morphology is largely determined by varying the NaOH concentration.

We have shown that the surface potential of anodic alumina films changes in time: immediately after the anodization process it was positively followed by the substantial decrease to negative values. Such variations of the surface potential can be associated with the negative built-in electric charge in alumina. The highest negative charge density occurs in the films formed in citric and phosphoric electrolytes.

Theoretical and experimental results on the formation of gold nanoparticles under the influence of pulsed nanosecond laser irradiation of aqueous AuCl${}_4^{-}$ solution are presented. It is shown that high monodispersity of nanoparticles ensemble is related to the strong dependence of total absorbance of laser radiation on nanoparticles diameter and the conductive heat transfer to surrounding medium.

Thin films based on limited solid solutions of cadmium and zinc sulfides have been synthesized by a one-stage epitaxial layer-by-layer deposition from an ammonium-containing aqueous solution of cadmium and zinc chlorides and thiocarbamide on a glass substrate. The thickness control of sulfide layers was carried out by selection of reagent concentrations and the deposition conditions. The relationship between the synthesis conditions of Cd_xZn${}_{1-x}$S thin films and the size of sulfide nanoparticles in these films is established. The films contain two phases: hexagonal (space group $P{6}_{3}mc$) phase with $B4$ structure of wurtzite type and cubic (space group $F$-$43m$) phase with $B3$ structure of sphalerite type. It is shown that the Cd_xZn${}_{1-x}$S film consists of separate $\sim 500$nm agglomerates which are a collection of smaller nanometer-sized particles. The dependence of the band gap of the synthesized films on their thickness is found.

Cubic solid solutions Ag_xPb${}_{1-x}$S are synthesized by chemical co-deposition from aqueous solutions of lead acetate and silver nitrate in the presence of a sulfidizing, complexing and stabilizing agent. For the first time, thermal expansion of the synthesized semiconductor solid solutions Ag_xPb${}_{1-x}$S is determined.

The surface microstructure and wettability of Al-1.0 at.% Cr alloy films obtained by ion-beam-assisted deposition on glass substrates have been investigated using atomic force microscopy, scanning electron microscopy and the sessile drop method. In the passive deposition regime, the surface roughness of the films increased from 8.9nm to 21.6nm with an increase in coating time from 3h to 9h. A quantitative analysis of the morphology evolution of the films during their growth was performed. The results revealed that Al-1.0 at.% Cr alloy films are hydrophilic. The mechanism of heterogeneous water wetting of Al-1.0 at.% Cr alloy films was considered, when the increasing surface roughness accounts for a decrease of hydrophilicity.

The temperature of alumina barrier layer during a high electric field anodization of aluminum (the current density more than 50mA/cm${}^2)$ has been studied by analyzing the aluminum film resistance. In the case of Joule heat power density to be larger than 20W/cm², the temperature inside the barrier layer can exceed $660^{\circ }$C, which leads to the local melting of aluminum. Scanning electron microscopy has shown the location of molten aluminum droplets and their movement during the anodization process.

We report on surface nanostructuring of Cu(In,Ga)Se₂ (CIGS) films using inductively coupled argon plasma treatment with the ion energy of 25–30eV within 30–120s. The films were fabricated on glass substrates using the selenization method and had a polycrystalline structure. We demonstrate that the plasma treatment results in the formation of tip-shaped nanostructure arrays with the geometrical parameters controlled by the treatment duration. The features of the surface nanostructuring using low energy ions are discussed.

Gold nanostructures were fabricated in porous SiO₂/Si ion-track templates by the wet chemical deposition from a solution of Au(I) sulfite complex. Their morphological features were analyzed, and features of the deposition processes were determined. A mechanism describing the selective formation of gold nanostructures in the pores of SiO₂ was proposed. The present approach allows us to control shape and size of Au nanostructures those which can be used as plasmonic active surfaces for SERS detecting of small amounts of biological and chemical substances.

Modification of indium sulfide (In₂S₃) film surface was performed by the treatment in high-density low-pressure inductively coupled argon plasma. The films with thickness of 500–800nm were fabricated on glass substrates by the thermal evaporation method and subsequent annealing in sulfur ambience. The plasma treatment of as-grown and annealed films was carried out with argon ions having the energy of 25–200eV. Nanostructuring of the film surface took place resulting in the formation of arrays of nanosized indium droplets.

The interaction between a solid inert metal Ir and an active liquid metal Ga during mechanical activation in a high-energy planetary mill is studied by X-ray diffraction and scanning electron microscopy with high-resolution energy dispersive X-ray microanalysis. The effect of mechanical activation on the formation of Ga_xIr_y intermetallic compounds and Ga_xIr_y/Ir composites and their solubility in acids was investigated. The subsequent extraction of Ga from intermetallic compounds and composites in the mixture of concentrated acids $(\mathrm{\text{HCl}}+{\mathrm{\text{HNO}}}_3)$ makes it possible to produce nanoscale Ir.

Tribological properties of composite Langmuir–Blodgett monolayers of oleic acid (OA) with MoS₂ nanoparticles formed on silicon surfaces by the horizontal precipitation method were studied. Incorporation of MoS₂ (the average particle size $\sim 90$nm) into the structure of the layer was found to result in the increase of minimal area per molecule from 0.43nm² to 0.58nm² and wear stability of OA monolayer.

This work shows comparative analysis of surface-enhanced Raman scattering (SERS) activity of gold nanoparticles fabricated by chemical synthesis and laser ablation methods. The gold nanoparticles prepared by laser ablation (Au-LA) are more effective for SERS than those prepared chemically (Au-citr). The “analyte on Au film” configuration allows obtaining enhancement of Raman scattering up to 10⁴ in case of Au-LA nanoparticles and up to 10² in case of Au-citr. Also the “sandwich” configuration for Au-LA gives additional enhancement of SERS up to two times, and for Au-citr up to one order, that is consistent with theoretical calculations.

The compounds of (Y${}_{1-x}$La_x)₃(Al${}_{1-y}$Ga_y)₅O${}_{12}$:Ce${}^{3+}$ compositions with partial substitution of Y${}^{3+}$ and Al${}^{3+}$ by La${}^{3+}$ and Ga${}^{3+}$, respectively, were fabricated by the co-precipitation method using different precipitants. Detailed investigations of the crystalline structure were made using the neutron diffraction method. The influence of the precipitant, quantity and type of the substituted ions on the structural and luminescent properties of the compounds was established. Distortion of the oxygen dodecahedron in the crystals has the strongest impact on their luminescent properties.

In this paper we focused on the evolution of transient cavitation activity during the sonochemical treatment of magnesium aqueous suspensions. We have investigated the non-linear behavior of the cavitation activity related to the hydrogen released in the reaction of magnesium with water. Ultrasound modifies magnesium particles leading to the formation of nanostructured Mg(OH)₂ phase (brucite) resulting in the chemical and sonochemical impacts on magnesium.

New accessible sonochemical methods were developed for the functionalization of synthesized graphene oxide (GO) with copper/iron compounds and drug intercalation into their structure in aqueous solution at ambient conditions by using ultrasound (20kHz) treatment. The sonochemical formation mechanism of a new nanomaterial was revealed through the structural analysis of three types of nanocomposites: (i) copper@graphene oxide, (ii) copper/iron@graphene oxide and (iii) iron@graphene oxide. Unique copper/iron-modified graphene oxide nanocomposites can be used as nanocarriers for the anti-inflammatory drug (ketorolac) delivery in aqueous solution due to the reduced submicron size and enlarged surface area. Disintegration of the ultrasonically intercalated ketorolac followed the exponential decay curve fit at higher pH values of the aqueous solution with a higher decay constant observed in copper/iron-modified graphene oxide nanocomposites.

The thermal behavior of water confined in mesopores of silicon membrane was evaluated by differential scanning calorimetry. The results showed strong supercooling of water inside the pores which allowed us to estimate the content of freezable pore water and nonfreezable pore water in the analyzed membranes.

Copper nanostructures demonstrating an activity in the surface-enhanced Raman scattering (SERS) spectroscopy were formed via electrochemical deposition of copper on porous aluminum oxide (PAO) and protected from oxidation by surface coverage with polyethylene glycol (PEG) and silver. The SERS measurements of 10${}^{-6}$-M 4-mercaptophenylboronic acid (MPBA) molecules adsorbed on fresh Cu-coated samples, Cu–PEG and Cu–PEG–Ag nanocomposites after 5, 10, 15, 60, 180 and 300min of storage in air indicated the effectiveness of the proposed approach in protection from oxidation.

Porous nanostructured strontium titanate films doped with europium SrTiO₃:Eu${}_{0.053}$ fabricated on silicon and porous anodic alumina by the sol–gel route are presented. The films with the thicknesses of 430nm and 510nm after depositions of three and five layers, respectively, have the perovskite structure confirmed by X-ray diffraction. The porous films demonstrate Eu${}^{3+}$ photoluminescence peaks at 593 (${}^5{D}_0\to {}^7{F}_1$), 615 (${}^5{D}_0\to {}^7{F}_2$) and 705 (${}^5{D}_0\to {}^7{F}_4$)nm. The porosity and PL intensity of the fabricated films noticeably reduce with the number of deposited layers.

Simple, reliable and scalable tool for the decoration of reduced graphene oxide (RGO) by iron oxide nanoparticles and the creation of polymer–RGO–Fe₃O₄ thin films are proposed. The composite is magnetically sensitive. Structural and microscopic studies and resistance measurements were performed. It has been found that these composites possess the hole-type conductivity.

Colloidal stability of core–shell nanoparticles consisted of silver core and chitosan/dextran sulfate multilayer shell in NaCl and CaCl₂ solutions was investigated. The critical concentration of coagulation and the Hamaker constant were calculated depending on the number of bilayers in the shell on the nanoparticle surface. The colloidal stability of the core–shell nanoparticles significantly increases with the shell growth.

The research of structure, roughness and friction coefficients of tantalum and tantalum oxide coatings on steel and glass substrates by the AFM method is presented. The samples are characterized by low friction coefficients. These materials are proposed for fabrication of stents in medical applications.

Surface properties of a two-layer polymer PMF-351 film exposed to the dielectric barrier discharge (DBD) low-temperature plasma have been studied by atomic force microscopy. It is established that such treatment leads to an increase of surface adhesion. The largest adhesion forces of about 165nN were achieved after 5min of treatment at the distance of 2sm, power of 30W and nitrogen flow of 3.1L/min. SiO₂ nanoparticles with diameters of 10–20nm were distributed over the treated polymer film surface from a suspension by centrifugation and they formed uniform rounded formations with the diameters of 50–100nm.

The potential ability of SiO₂(Ag)–Si nanosystem to induce oxidative stress and death of human peripheral blood cells involving reactive oxygen species was studied using a double-color cytoflourometry method. This SiO₂(Ag)–Si system with silver dendrites obtained via the metal deposition into the pores of SiO₂ template on a silicon substrate was shown to increase the concentration of ROS but not cause the cell death associated with oxidative stress. Such systems are prospective for the analysis of biological substances with Raman scattering.

La₂Zr₂O₇:Er, Yb nanoceramics have been obtained. Its structural and up-conversion luminescent properties were investigated. Under 980 nm laser excitation, the ceramics produced intense green and red up-conversion emission. The influence of Er³⁺ concentration and annealing conditions on the emission intensities has been discussed. The fabricated ceramics are expected to be an efficient up-conversion material with potential applications for laser diodes, display devices, detectors where the near infrared excitation is required.

We review our results on large-scale atomistic simulations of the phase change compound GeTe of interest for applications in nonvolatile electronic memories. The simulations are based on an interatomic potential with an accuracy close to that of the density functional theory (DFT). The potential was generated by fitting a DFT database by means of an artificial neural network method. This methodological advance allowed us to perform molecular dynamics simulations with several thousand atoms for several ns that provided useful insights on several properties of interest for the operation of phase change memories, including the crystallization kinetics, the dynamics of the supercooled liquid, the structural relaxation in the glass and the properties of nanowires.

An analytic model of $J$–$V$ characteristics of photovoltaic devices based on quantum dot (QD) solids is developed. The model yields the upper estimation of the power conversion efficiency and predicts its extremal dependence on the diffusion length of excitons. The predictive power of our model is approved by the comparison with the experimental data for PbS QD-based solar cells.

The $p^{+}$–$p^{-}$–$n$ diode structures with a variable number of $\beta$-FeSi₂ and CrSi₂ nanocrystal (NC) bilayer were studied at room and liquid nitrogen temperatures. The high crystal quality of Si and embedded NCs was determined by HRTEM cross-sectional data. This diode demonstrated a photoresponse in the IR region (1.02–0.8eV) which was associated with a decrease in recombination losses with the main contribution coming from CrSi₂ NCs. Calculations of photoyield and its extrapolation to zero resulted in band gap values of 0.35eV at 300K and 0.46eV at 90K. The spectral sensitivity of $1.06\times 10^{-4}$A/W and specific detectivity of $1.38\times 10^6$(cm Hz${}^{1∕2}$/W) were determined at $\lambda =1.5$$\mu$m and T=300K.

The electrical and structural properties of titanium oxides TiO₂/TiO_x fabricated by reactive magnetron sputtering were studied and used in a memristor. X-ray diffraction and $I$–$V$ measurements were performed in order to characterize the fabricated structures.

Photoconductive and photovoltaic properties of film composites based on poly-$N$-epoxypropylcarbazole doped with a derivative of nickel dithiolene are investigated. These composites possess a hole-type photoconductivity. The internal photoeffect is attributed to the photogeneration of charge carriers from the metal complex and the hole transport through the donor fragments of the polymer matrix.

The degradation of the Surface-enhanced Raman scattering (SERS) signal under laser illumination during spectral measurements is typically observed. To improve the stability of the SERS spectra intensity, hybrid plasmonic structures involving graphene-based protective layers were formed. An observation of the time evolution of the characteristic peak from analyte molecules indicates that the graphene coating can be used to improve the stability of the SERS signal.

Photodetectors (PDs) based on single-walled carbon nanotube film/silicon and graphene/silicon heterojunctions have been realized for fast applications. We investigated the response of the PDs to femtosecond pulsed laser using a three-electrode configuration for photoconductive operations. Both junction PDs exhibit rise times of some nanoseconds, detecting light from ultraviolet (275nm) to infrared (1150nm). Applying a gate voltage $V_G$, the rise time decreases down to about 1ns, making our devices comparable to most commercial PDs.

Porous silicon layers have been formed by electrochemical anodization of $p$- and $n$-type Si substrates. The volume of hydrogen desorbed from the surface of porous silicon after the anodic treatment was measured to be as large as 4wt.%. Regeneration of hydrogen can be achieved by porous silicon reanodization.

SrTiO₃ and SrTiO₃:Nd films of 110nm and 210nm thickness were fabricated using the sol–gel technology on silicon. Their current–voltage characteristics were investigated with and without illumination. The film structures are photosensitive and exhibit the hysteresis on the forward and reverse bias with loop broadening at the reverse part.

Design and manufacturing technology of 3D silicon photonic structures with optical interconnections through microchannel vias interposers were developed. Silicon chips placed over each other were separated by the silicon microchannel vias interposer served as a light waveguide. Light emitting diodes and photodiodes were formed at the inner surfaces of silicon chips from nanostructured silicon clusters embedded into alumina matrix. The developed structure is characterized by the current conversion efficiency of 0.1% and can operate in the GHz frequency range.

Transmission coefficient and field emission current in a silicon vacuum nanostructure with a pyramidal cathode were calculated as a function of applied voltage, size of the cathode and distance between the anode and cathode by the phase function method. The field emission current density in the range of 1–10 A/cm² was found to be achieved by varying the distance between the anode and cathode in the range of 15–25nm and the applied voltage in the range of 1.2–2.3V.

The results of simulation of electron transfer processes in a single graphene layer on a SiC substrate are presented. High mobility of charge carriers with respect to all known materials makes graphene to be a promising candidate for applications in new semiconductor devices. The prevalence of electron–electron scattering over other types of scattering in the range of moderate field energies in a single graphene layer is established by modeling using the Monte Carlo method.