Zinc and vanadium oxide precursor sols have first undergone selective phase separation. The work reveals the mechanisms underlying this process. Traditional sol-gel synthesis of mixed oxide films at low precursor concentrations of one of the oxides leads to generating solid solutions or X-ray amorphous materials. Using sol-gel films of ZnO modified with vanadium in a ratio of [V]/[Zn] = 0.05 as an example, we demonstrate that adding graphene oxide dispersions into the mixed sol during its preparation results in generating a composite crystalline film containing ZnO and VO2 phases after thermal annealing. Conversely, the separate introduction of vanadium compounds and graphene oxide dispersions into the zinc oxide precursor sol causes the amorphization of ZnO.

The work explores the effect of modifying thin ZnO and ZnO:V sol–gel films with graphene oxide (GO) dispersions on their structural and photocatalytic properties. The study has, for the first time, detected the effect of selective phase separation in sols, characterized by the separate crystallization of zinc and vanadium oxides upon adding GO dispersion into a mixed sol. Increasing the GO concentration in ZnO-VO2 precursor sols improves the crystallinity of the material; films of the same composition without added GO are X-ray amorphous. Conversely, adding GO to unmodified ZnO sols causes a reduction in the crystallite size of the films, which increases with higher GO content. Notably, their photocatalytic activity varies non-monotonically: at 10 wt.% GO, it is minimal, while a further increase in the GO concentration leads to its improvement. An increase in the GO concentration in ZnO:V films causes a monotonically enhanced efficiency of photocatalysis. This may be related to the improved crystallinity and the formation of a percolation cluster from reduced graphene oxide.

We discovered that the parameter defined as the ratio of the fraction of zinc atoms at lattice positions in ZnO powders from the total zinc content (calculated using XPS) to the square of the nanocrystallite size (calculated using XRD) presents a very strong positive correlation (rxy = 0.99) with the rate constant of photocatalytic decomposition of paracetamol in UV radiation. ZnO samples were derived by various chemical methods under various process conditions.

Purpose: The aim of the work is to study by X-ray photoelectron spectroscopy the transformation of the surface architecture of zinc oxide powders, previously obtained by mechanical milling, during their etching with argon ions.Experimental: The etching was carried out in two steps of 30 s duration each at a current of 1 μA. It was found that on the surface of initial powders 45 % of zinc is a part of the crystal lattice of ZnO, and the remaining 55 % exist in the form of hydroxide.Conclusions: The first etching step reduced the fraction of hydroxyl groups on the surface to 1 per 5 zinc cations in the ZnO lattice, and further etching showed the impossibility of deeper purification of the sample from OH-groups. In contrast, the carbon atoms almost completely left the powder surface after the end of the second etching step

A controlled modification of the parameters of the zinc oxide band structure has been demonstrated using the methods and approaches of nanostructure engineering by varying the duration of high-energy mechanical grinding. It has been shown that an increase in the dispersion time increases the monodispersity of ultrafine ZnO powder particles. A decrease in the zinc oxide band gap with increasing grinding duration is established based on spectrophotometric investigations. A nonmonotonic time dependence of the top of the valence band, as well as a high-energy shift of the valence and conduction bands for all dispersion durations, are demonstrated using experimental X-ray photoelectron spectroscopy data.

The article suggests a simple one-step sol–gel method for synthesizing nanostructured zinc oxide films co-doped with copper and aluminum. It shows the possibility of forming hierarchical ZnO:Al:Cu nanostructures combining branches of different sizes and ranks and quasi-spherical fractal aggregates. It demonstrates the use of the synthesized samples as highly efficient photocatalysts providing the decomposition of toxic dyes (methyl orange) under the action of both ultraviolet radiation and visible light. It establishes the contribution of the average crystallite size, the proportion of zinc atoms in the crystalline phase, their nanostructure, as well as X-ray amorphous phases of copper and aluminum to the efficiency of the photocatalysis process.

This study delves into the phenomena surrounding the emergence of negative charge accumulation on the surface of zinc oxide (ZnO) crystals upon exposure to low-energy electron irradiation within the range of E = 0 divided by 600 eV. We demonstrate the critical significance of the primary electron energy in dictating the initial processes initiated at the ZnO surface. Energy thresholds governing both the genesis and elimination of surface charge, along with the formation of oxygen vacancies on the ZnO surface, are elucidated. Our findings reveal that irradiation instigates distinct dissociative pathways contingent upon electron energy, engendering diverse physical and chemical transformations via bond dissociation, desorption, and atomic and molecular restructuring of the surface. These insights serve as pivotal groundwork towards advancing the fabrication of epitaxial films, facilitating the controlled generation of two-dimensional structures predicated on surface potential modulation.

The synthesis of a varistor powder based on ZnO is carried out with the further fabrication of a device structure within the framework of the sol-gel method. To monitor the processes occurring in the sol, the method of Fourier-transform infrared spectroscopy is used. Studies of the surface structure of the material are carried out using scanning electron microscopy. The constructed current–voltage characteristic of the varistor structure is nonlinear with a nonlinearity coefficient of 2.36. The use of the sol-gel method for the manufacture of devices of this type makes it possible to obtain a grain size of 0.25 μm and achieve a reduction in the sintering temperature to 900°C.

While preparing oxide layers as gas sensors by a sol-gel approach, a high-temperature annealing makes a challenge to apply in numerous applications like flexible electronics with a heavy influence on the oxide microstructure. Therefore, its replacing by UV irradiation combined with a mild heating as “photo-annealing” paves the way to develop soft protocols when designing oxide-based gas sensors bearing a fine nanocrystallinity. Herein, we consider hierarchical sol-gel derived ZnO films which were a subject of conventional annealing and photoannealing to compare their gas-sensor performance when exposed to alcohol vapors. It is found that films obtained by photoannealing have an X-ray amorphous character, in contrast to ones being thermally annealed; although, the hierarchical organization of both samples revealed by SEM is almost identical. The DFTB modeling performed for ZnO crystal exposed to alcohol molecules and water has indicated the chemiresistive effect to be enhanced with a molecular weight of analytes. These observations were validated in experiment with sol-gel ZnO layers which exhibited an alcohol response in sub-ppm concentration range down to 10 ppb. To selectively compare the impact of various alcohols, we successfully applied a linear-discriminant analysis to the vector signal of the on-chip multisensor array.

The results of studying the electronic states of the conduction band of ultrathin films of furan-phenylene co-oligomer 1,4-bis(5-phenylfuran-2-yl)benzene and the results of analyzing the interfacial potential barrier upon the formation of these films on the surfaces of (SiO2)n-Si and layer-by-layer deposited ZnO are presented. The formation of a (8–10)-nm-thick co-oligomer film was investigated by total current spectroscopy; the energy range from 5 to 20 eV above EF was analyzed. Furan-phenylene co-oligomer films on the (SiO2)n-Si surface have a domain structure with a characteristic domain size of 1 × 1 µm and surface roughness within a domain of no more than 1 nm. The films on the ZnO surface have a granular structure with a grain height of 40–50 nm.

Introduction. The regularities of changes in the photocatalytic activity of zinc oxide ZnO in the presence of synthetic zeolite are investigated. The data on the photocatalytic properties of the surface of lime coating based on the composition with the addition of zinc oxide and synthetic zeolite are presented.Materials and methods. A complex of general scientific research methods was used. Lime with activity of 83 % was used in the development of the formulation of the finishing composition. An aluminosilicate additive was used as a synthetic zeolite, obtained by adding microdispersed aluminum powders to sodium liquid glass with silicate module of 2.9 at a temperature of 60 °C for 90 minutes. The photocatalytic activity of ZnO using synthetic zeolite was studied by photodegradation of methylene blue dye under the action of UV light. The methods presented in the scientific and technical literature were used. Spectroscopic studies of the specimens were carried out on an FSM 1201 IR Fourier spectrometer (LLC “Infraspek”, Russia) and an SF-56 spectrophotometer.Results. An increase in the photocatalytic properties of the surface of a lime coating based on a composition using ZnO oxide and synthetic zeolite was established. The optical band gap of ZnO was determined. It was revealed that the optical band gap of zinc oxide in combination with synthetic zeolite is 2.96 and 2.70 eV, which is significantly less than the value of 3.37 eV characteristic of zinc oxide.Conclusions. To impart self-cleaning properties to lime coatings, it is proposed to introduce zinc oxide into the formulation of the photocatalyst together with an additive based on synthetic zeolite.

Using the methods of optical spectrometry and IR spectroscopy, the processes of self-assembly of nano- and microstructures of zinc oxide in combined sol-gel systems obtained by mixing film-forming sols with different maturation times were studied. Characteristic bands and absorption peaks in the IR spectra were established, demonstrating an unambiguous relationship between the IR transmittance — radiation and maturation time for different volumetric ratios of mixed sols. It has been shown that experimental IR spectroscopy data correlate with optical spectrometry data in the visible and UV radiation range. The correspondence of ZnO films formed on the basis of combined sol-gel systems to the tasks of nanostructural engineering has been demonstrated.

The effect of UV irradiation on sol-gel prepared ZnO films subjected to mild thermal annealing was investigated, with special attention to their structural and surface properties. Sol-gel processes, including a high-temperature annealing stage, have been adapted to the requirements of flexible electronics for in situ synthesis of semiconductor ZnO films on polymer substrates at lower temperatures due to UV irradiation. Application of UV radiation with emission peaks at 185 and 254 nm to films annealed at 180 degrees C made it possible to obtain ZnO films with Zn/O ratios of ca. 1, which cannot be achieved by heat treatment alone.

The surface topography and density of unoccupied electronic states at thermal deposition of ultrathin dibromo-bianthracene films on the ZnO surface have been studied. The electronic characteristics of unoccupied electronic states during growth of dibromo-bianthracene films to a thickness of 10 nm have been investigated by total current spectroscopy using a probe electron beam. The experimental dependences have been analyzed using theoretical calculation of the orbital energies for dibromo-bianthracene molecules by the method of density functional theory (DFT).

Приведены результаты исследования топографии поверхности и плотности незаполненных электронных состояний при термическом осаждении сверхтонких пленок дибромо-биантрацена на поверхность ZnO. Измерения электронных характеристик незаполненных электронных состояний в процессе роста пленок дибромо-биантрацена до толщины 10 нм проводили методом спектроскопии полного тока с использованием тестирующего электронного пучка. Анализ экспериментальных зависимостей проводили с использованием теоретического расчета энергий орбиталей молекул дибромо-биантрацена методом теории функционала плотности.

Thin dielectric Al2O3 and SrO films obtained by thermal evaporation in vacuum, as well as Si3N4 and SiO2 films obtained by RF magnetron sputtering, were studied by atomic force microscopy. The metric and fractal parameters of dielectric layers are estimated using the Gwyddion graphical program for analyzing data from scanning probe microscopy. It has been established that the maximum values of the fractal dimension are characteristic of aluminum oxide films with a thickness of 0.5 μm, while the smallest root-mean-square roughness is characteristic of strontium oxide films. The prospects for using the analyzed dielectric films as insulating layer of sensitive elements of strain gauge pressure sensors with a conductive elastic element are demonstrated.

— X-ray photoelectron spectroscopy has been used to study structural evolution of zinc oxide synthesized by a sol–gel process adapted to flexible electronics. We assessed the effect of ultraviolet irradiation time on the atomic percentages of different Zn, O, and C species. Increasing the UV treatment time from 90 to 150 min has been shown to considerably reduce zinc concentration in the surface layer, which is accompanied by an increase in the percentage of carbon, predominantly in the form of highly oriented pyrolytic graphite. Photoactivation processes ensure completion of surface structure formation and lead to enrichment of the ZnO surface in oxygen with a binding energy of 531.5 eV, resulting in a zinc-deficient solid solution.