Two-dimensional graphitic carbon nitride 2D g-C3N4 has the potential for gas sensing as a metal-free semiconductor with a layered structure, high surface area, and tunability of electronic properties. In this context, 2D g-C3N4 nanosheets were prepared by the thermal polycondensation of urea followed by ultrasonic exfoliation. X-ray diffraction revealed diffraction peaks corresponding to the (110) and (002) crystallographic planes of g-C3N4. Scanning electron microscopy showed a nanosheet structure with a 10-nm crystallite size, while energy-dispersive X-ray spectroscopy demonstrated a uniform distribution of carbon and nitrogen. Ultraviolet-visible absorption spectroscopy revealed a band gap of 2.8 eV. Gas sensing measurements exhibited an increase in response to isopropanol and ethanol as the operating temperature and gas concentration increased. Impedance spectroscopy provided additional insight into the sensing mechanism. Observed depressed semicircles in Nyquist plots were fitted with a charge transfer resistance Rct in parallel with a constant phase element model. The charge transfer resistance Rct fell systematically with isopropanol exposure, confirming the crucial role of adsorption-induced electron transfer in the gas sensing response.

Ternary metal chalcogenide quantum dots (QDs), such as CuInS2, have attracted significant attention due to their lower toxicity compared to binary counterparts containing cadmium or lead, making them promising candidates for biomedical imaging and solar energy applications. The surfactant choice is critical for controlling nanocrystal nucleation, growth kinetics, and functionalization. This directly affects the toxicity and applications of QDs. In this work, we report a synthesis protocol for PVP-capped CuInS2 QDs in an aqueous solution. Using density functional theory (DFT) calculations, we predicted the coordination patterns of PVP on the CuInS2 QDs surface, providing insights into the stabilization mechanism. The synthesized QDs were characterized using TEM, XRD, XPS, and FTIR to assess their morphology, chemical composition, and surface chemistry. The QDs exhibited dual photoluminescence (PL) maxima at 550 nm and 680 nm, attributed to defect-related emissions, making them suitable for cell imaging applications. Cytotoxicity studies and cell imaging experiments demonstrate the excellent biocompatibility and effective staining capabilities of the PVP-capped CuInS2 QDs, highlighting their potential as fluorescent probes for long-term, multicolor cell imaging including two-photon microscopy.

The study of the processes of low-temperature synthesis of one-dimensional particles, which are the basis for two- and three-dimensional structures, is relevant for materials science. The modified metal-stimulated electrochemical etching method made it possible to synthesize silicon nanowires with an average thickness of about 292.6 nm. Scanning electron microscopy has shown the formation of nanowires, flower-like structures, and clusters of matter after the deposition of zinc oxide on the porous surface. The hexagonal structure of ZnO crystallites was determined by X-ray diffraction spectroscopy. Studies of the initial sample by electron paramagnetic resonance (EPR) spectroscopy revealed a narrow signal in the center of the spectrum. The subtraction of the EPR spectra with a sequential increase in microwave power up to 8 mW shows the absence of saturation of the signal. This indicates an almost free flow of charges through the surface nanostructures under the influence of an external field. Heat treatment in an air atmosphere at 300 °C caused a significant increase in the intensity of the EPR spectrum. This led to an increase in the intensity of charge transfer through paramagnetic centers.

The conductivity of direct and alternating current for graphite-like amorphous carbon films after annealing in vacuum at a temperature of 700 °C was studied. The I-V characteristics of such films are symmetrical. The I-V curve in logarithmic coordinates demonstrated the presence of two linear sections. A study of the frequency dependences of structures with a thin graphite-like amorphous carbon film showed a sharp increase in capacitance at low frequencies and a decrease in the high-frequency region. The increase in capacitance in the low-frequency region is explained by the Maxwell-Wagner polarization, which is observed in inhomogeneous dielectrics with conducting inclusions. The results of temperature measurements of resistance showed that at room temperatures, there is a mechanism of conduction of electrons with a variable jump length along localized states lying in a narrow energy band near the Fermi level. At the same time, with an increase in the injection current, an additional mechanism of hopping electrical transport with a variable jump length along localized states in the tail of the valence band arises, which leads to an increase in the conductivity of the films.

The possibility of synthesizing gallium oxide semiconductor layers by the classical thermal method of molecular layering with trimethyl gallium and ozone precursors and controlling the electrical properties of the synthesized layers is shown. Homogeneous layers of specified thickness have been deposited in a single cycle onto a silicon substrate, monocrystalline quartz, and high-aspect-ratio 3D substrates in the form of microchannel plates. The synthesized gallium oxide layers are amorphous, conforming to the Ga2O3 stoichiometry; have a band gap of 4.9 ± 0.2 eV; and do not exhibit the impurity conductivity. The possibility of obtaining gallium oxide films with the impurity conductivity by molecular layering according to a specified program, with alternation of the chemical composition of the precursors used, is demonstrated.

The photoluminescence enhancement of a composite structure on porous silicon with surface-grown silver dendrites was discovered in this study. Silver dendrites are plasmonic antennas that exhibit a slight amplification effect. The small improvement of penetrating light intensity resulted in a significant increase in two-photon absorption, culminating in a remarkable increase in the photoluminescence intensity of the porous silicon material. The manifold enhancement of two-photon absorption was demonstrated by theoretical calculations of its probability.

Currently, semiconductor gas sensors are being actively studied and used in various fields, including ecology, industry, and medical diagnostics. One of the major challenges is to reduce their operating temperature to room temperature. To address this issue, sensor layers based on WO3−x/WS2 nanostructures synthesized by the hydrothermal method have been proposed. In this paper, the morphology of the material’s surface and its elemental composition were investigated, as well as the optical band gap. Additionally, changes in the resistance of the WO3−x/WS2 sensor layers under the influence of alcohol vapors at room temperature were analyzed. The results showed that the layers exhibited a significant response, with short response and recovery times. The achieved response value to 1000 ppm of isopropanol was 1.25, with a response time of 13 s and a recovery time of 12 s. The response to 1000 ppm of ethanol was 1.35, and the response and recovery times were 20 s. This indicates that these sensor layers have promising potential for various applications.

Hybrid organic–inorganic perovskites have emerged as promising materials for next-generation optoelectronic devices owing to their tunable properties and low-cost fabrication. We report the synthesis of 3D hybrid perovskites with monoethanolammonium cations. Specifically, we investigated the optoelectronic properties and morphological characteristics of polycrystalline films of hybrid perovskites MAxMEA1−xPbI3, which contain methylammonium (MA) and monoethanolammonium (MEA) cations. MAxMEA1−xPbI3 crystallizes in a tetragonal perovskite structure. The substitution of methylammonium cations with monoethanolammonium ions led to an increase in the lattice parameters and the bandgap energy. Energy level diagrams of the synthesized samples were also constructed. The bandgap of MA0.5MEA0.5PbI3 makes it a promising material for use in tandem solar cells. These polycrystalline films, namely MA0.5MEA0.5PbI3 and MA0.25MEA0.75PbI3 were fabricated using a one-step spin-coating method without an antisolvent. These films exhibit a uniform surface morphology under the specified deposition parameters. Within the scope of this study, no evidence of dendritic structures or pinhole-type defects were observed. All synthesized samples demonstrated photocurrent generation under visible light illumination. Moreover, using monoethanolammonium cations reduced the hysteresis of the I–V characteristics, indicating improved device stability.

When developing gas sensors, selecting a suitable gas-sensing material is of great importance. Currently, there is great interest in the development of new gas-sensitive layers based on molybdenum oxide MoO3 and improvement of their sensor characteristics. In the work, a MoO3 gas-sensitive layer is obtained by the hydrothermal method followed by annealing at a temperature of 400°C for 2 hours. The elemental composition of the surface of the obtained sample is analyzed using X-ray photoelectron spectroscopy. Studies of the sensor response, response time, and recovery time of the gas-sensitive layer to isopropyl-alcohol vapors at different operating temperatures are carried out. The chemical composition is shown to be consistent with MoO3, but adsorbed hydroxyl groups are also observed on the surface. Analysis of the sensor properties shows that the sensitivity at temperatures of 250°C and 150°C is 13.3 and 5.5, respectively. It is found that layers based on MoO3 nanoparticles synthesized by the hydrothermal method exhibit sensitivity to isopropyl-alcohol vapors even at a temperature of 150°C.

Introduction. Solid-state electron multipliers (EMs) in matrix design, referred to as microchannel plates (MCPs), are an integral part of modern electronics. Recent progress in the field of molecular layering (ML) technology has offered an opportunity to tailor and improve the characteristics of solid-stated EMs by depositing thin layers inside the channels of these structures.Aim. To study the possibility of depositing thin layers inside the surface of solid-state EM channels by ML in order to increase the secondary electron emission coefficient (SEEC) of such structures, thereby improving their performance characteristics.Materials and methods. The ML method was used to deposit nanometer films of magnesium and aluminum oxides inside solid-state EM channels. The composition and structure of the layers were studied using scanning electron microscopy, X-ray photoelectron spectroscopy, secondary electron emission analysis, and atomic force microscopy.Results. Thin aluminum oxide and magnesium oxide films were synthesized inside the micron channels of solidstate EMs. The layers exhibited high uniformity along the entire length of the channels. The layer thickness varied in the range from 2 to 30 nm. Layers with improved emission and protective characteristics were obtained. Comparative tests of MCP samples containing the synthesized films were carried out.Conclusion. Good prospects for the application of emissive layers inside solid-state EM channels were shown. Structures with a high aspect ratio are promising objects for ML application. The creation of nanocomposite structures based on MCPs opens up the fundamental possibility of improving the current technology of producing electrooptic materials and devices. The MCP structures containing aluminum oxide layers obtained by ML technology were experimentally tested to detect beam collisions (FBBC) for work in detectors at the NICA accelerator complex. Following deposition of a 3.0 nm-thick Al2O3 film in the channels of the tested MCP samples, the signal amplitude increased by 1.5 times. The deposition of layers with a film thickness of 10 nm resulted in a 2.5-fold increase in the amplitude.

A comprehensive analysis of the current level of research in the development of intelligent hybrid nanosystems based on porous inorganic materials, in particular porous alumina, is carried out. The presented works show interesting opportunities for the development of intelligent, multifunctional optical devices with a microchip design.

Currently, semiconductor gas sensors are of interest for various applications, including industry, medicine and environmental monitoring. One of the most important tasks in the sensor technology is to reduce the operating temperature of devices. In this paper, it is proposed to use WOx/WS2 nanostructures obtained by a hydrothermal method to solve this problem. The morphology, structure, and composition of the developed nanostructures were studied using scanning electron microscopy, reflected electron diffraction and X-ray photoelectron spectroscopy. It is shown that the nanostructures are formed by 1D and 2D nanoobjects with an average length of 200 nm and are nanocomposites consisting of tungsten oxide WOx and tungsten disulfide WS2. The study of sensory properties when exposed to isopropanol, ethanol and acetone vapors at room temperature was carried out. A reversible change in resistance is demonstrated when these gases appear in the atmosphere. Additionally, exposure to ultraviolet radiation during the measurement process leads to an increase in the response value and speed of the sensor layers in the case of interaction with isopropanol and ethanol vapors.

The crystallization conditions from the solution play an important role in determining the morphology, phase composition, and photovoltaic properties of perovskite films. Post-processing of the obtained films can have a crucial role in increasing the grain size of perovskite and enhancing its crystallinity. It has been shown that the formation of crystal nuclei can be utilized to accelerate crystallization. In this case, crystallization occurs through the growth of seed crystals created in the solution, enabling the formation of relatively large crystals. For the deposition of CH3NH3PbI3 hybrid halide perovskite films from a solution of the perovskite in dimethylformamide, the spin coating technique was employed. Pre-crystallization was achieved by annealing the films at a temperature of 100 or 110 °C. The dissolution process involved adding a drop of dimethylformamide onto the substrate surface and allowing it to partially dissolve the perovskite film. Subsequently, residual solvent was removed through spin coating. The morphological analysis of the perovskite film surface after recrystallization at temperatures ranging from 80 to 130 °C was performed. The infrared transmission spectra of the obtained perovskite films were investigated, and their light absorption characteristics were studied through transmission spectra. The perovskite structure in the obtained films was confirmed by the peaks observed in the X-ray diffraction patterns. It has been shown that the photocurrent values for solar cells with perovskite films obtained by recrystallization are 15–20% higher than those of perovskite films obtained by traditional crystallization methods.

a low-temperature technique for the formation of coatings based on ZnO nanorods decorated with colloidal AgInS2 quantum dots is presented. It is shown that ZnO nanocrystals and colloidal AgInS2 quantum dots with a shell of mercaptopropionic acid molecules form a hetero junction. Sensitization of ZnO nanorods with AgInS2 colloidal quantum dots to visible irradiation provides a gas analytical response of the structure to isopropyl alcohol vapor at room temperature under blue LED illumination with a peak wavelength of 460 nm.

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.

This manuscript comprises the novel experimental, numerical and theoretical investigation results for a newly developed low-macroscopic-field emission cathode prototype. The brief introductory information regarding the baseline for both scientific and engineering background is provided. The prototype acquisition process is described. Scanning electron microscopy images of the material surface are included. The results of emitted electron energy spectra modeling based on WKB approximation considering the formation of charged states with negative correlation energy values, correspond well to the acquired experimental data. Each of the observed peaks relates to the specific "hot electron" energy levels emerging due to the existence of the potential-well structure within the cathode surface layer.

A method for the formation of nanostractured coatings from ZnO nanorods for use in adsorption gas sensors is presented. It has been shown that ultrasonic spray pyrolysis provides the formation of local growth centers for the formation of ZnO nanorods by the low-temperature hydrothermal synthesis. The obtained ZnO nanorods with a small diameter demonstrate a high concentration of oxygen vacancies in the near-surface region of the nanorods and a high surface concentration of hydroxyl groups. An additional method is proposed for testing seed layers by resistance using a liquid probe based on an indium-gallium melt without the need to apply top contacts. The presented technique is suitable for mass production of sensor coatings. The obtained nanostructured coatings from ZnO nanorods demonstrate a high gas analytical response.

Today, air pollution is a global environmental problem. A huge amount of explosive and combustible gas emissions that negatively affect nature and human health. Gas sensors are one of the ways to prevent this impact. Several types of sensors have been developed, but the main problem with them is the high operating temperature. This leads to a decrease in reproducibility and stability over time. The aim of the work is to synthesize zinc stannate nanoparticles, study their phase composition, and modify the structure with silver nanoparticles to improve gas-sensing characteristics. This paper presents the synthesis of zinc stannate nanoparticles by the coprecipitation method and annealing at varying temperatures. A method of decorating zinc stannate with silver nanoparticles was proposed. Using XRD, it was found that a change in the annealing temperature leads to a change in the initial phase composition of the sample. Decoration with silver nanoparticles allows for increasing the sensor response of zinc stannate layers to isopropyl alcohol by 20 times. The corresponding increase in response to ethanol is 16 times.