Zinc oxide nanorods constitute a promising material for making the transducer elements of biosensor systems because of their physical and chemical properties. We report here studies of the effects of annealing temperature on the concentration of the surface hydroxyl groups ensuring successful immobilization of biologically recognizable elements was assessed. X‑ray photoelectron spectroscopy results showed that annealing at 500 °C increased the concentration of oxygen vacancies compared with annealing at 300 °C. FTIR spectroscopy data also confirmed a higher concentration of OH groups in the sample annealed at 500 °C than in commercial nanoparticles.

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.

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.

This paper presents a study of the gas sensitivity of a nanostructured zinc oxide coating to isopropyl alcohol vapor during heating, ultraviolet irradiation, as well as simultaneous heating and irradiation. Simultaneous heating to 150oC and ultraviolet irradiation ensures an increase in the sensor layer response. A 10-fold decrease in the power consumption of an ultraviolet light-emitting diode results in a 1.2-fold decrease in the response of the sensor coating. Reducing the operating temperature of a gas sensor with low power consumption and achieving the required sensitivity can provide adsorption sensors integration into portable devices for monitoring ambient air quality. Keywords: zinc oxide, nanorods, gas sensor, UV irradiation, combined activation.

Impedimetric biosensors represent a powerful and promising tool for studying and monitoring biological processes associated with proteins and can contribute to the development of new approaches in the diagnosis and treatment of diseases. The basic principles, analytical methods, and applications of hybrid impedimetric biosensors for express protein detection in biological fluids are described. The advantages of this type of biosensors, such as simplicity and speed of operation, sensitivity and selectivity of analysis, cost-effectiveness, and an ability to be integrated into hybrid microfluidic systems, are demonstrated. Current challenges and development prospects in this area are analyzed. They include (a) the selection of materials for electrodes and formation of nanostructures on their surface; (b) the development of efficient methods for biorecognition elements’ deposition on the electrodes’ surface, providing the specificity and sensitivity of biosensing; (c) the reducing of nonspecific binding and interference, which could affect specificity; (d) adapting biosensors to real samples and conditions of operation; (e) expanding the range of detected proteins; and, finally, (f) the development of biosensor integration into large microanalytical system technologies. This review could be useful for researchers working in the field of impedimetric biosensors for protein detection, as well as for those interested in the application of this type of biosensor in biomedical diagnostics.

This research focuses on the comparative analysis of effect of barium doping on the behavior of conductivity and impedance of organic-inorganic perovskite films, with an emphasis on their potential application in photovoltaic technology. The structural and electrical characteristics of CH3NH3PbI3 thin films with and without Ba are examined. Atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction are used to investigate the morphology and structure of the samples. It was found that light-dependent transport in CH3NH3PbI3 thin films in the temperature range of 77–295 K leads to a tenfold decrease in the activation energy; this decreases from 160 – 280 meV to 10-20 meV as the temperature drops from 300 to 77 K. Light induces an increase in the activation energy at low temperatures, rising from 10 meV in darkness to 15-20 meV in light. CH3NH3PbI3 thin films doped with Ba stands out due to its notably higher photoluminescence intensity, suggesting an enhanced crystalline quality and a reduced defect density. Such characteristics are crucial for optimizing the efficiency of solar cells.

Nowadays an important task is the development of nanostructures of the Zn–Sn–O ternary oxide system, which are of practical interest for various fields, including gas sensors, photocatalysts, lithium-ion batteries, and solar cells. Zinc-stannate nanowires are formed by the hydrothermal treatment of preliminarily synthesized zinc-oxide nanowires in a solution of potassium stannate and carbamide. Using scanning electron microscopy and backscattered electron diffraction, the samples are found to have the Zn2SnO4 structure, and their geometric dimensions do not change compared to the initial zinc-oxide nanowires. The diameter of the obtained structures is about 300 nm, and the length is about 2 mm. According to X-ray photoelectron spectroscopy data, as a result of hydrothermal treatment, the surface structure changes and tin atoms are incorporated into the crystal structure of zinc oxide. The study of the gas-sensing properties of Zn2SnO4 layers shows that they are more efficient in detecting isopropyl alcohol vapor compared to the initial zinc-oxide nanowires. Zn2SnO4 layers allow the detection of isopropyl alcohol vapor at temperatures of about 150°C. The sensor signal with respect to 1000 ppm C3H7OH is 3.79.

Nowadays, the development of approaches to increase the sensitivity and reduce the operating temperature of gas sensors based on metal oxides is the important task. In this paper, these problems are solved by forming zinc stannate nanostructures during hydrothermal treatment of zinc oxide nanowires. The microstructure and chemical composition of the synthesized nanostructures were studied by SEM, EDS and XPS. Sensor responses to isopropyl alcohol vapors (1000 ppm) at 120 & DEG;C, 180 & DEG;C and 250 & DEG;C were measured. It was found that the sensor response values of zinc stannate nanostructures significantly exceed the responses of zinc oxide. Moreover, zinc stannate demonstrates the response of 6.3 at 120 & DEG;C. Thus, the developed structures can be used to create sensors of reducing gases with low operating temperatures.

The results of studying thin polycrystalline perovskite layers of CH3NH3PbI3 (MAPbI3) are presented. The resulting MAPbI3 layers demonstrate a characteristic absorption spectrum, optical band gap, and photoresponse to irradiation in the visible region of the spectrum. Two crystallization mechanisms have been found in the MAPbI3 layer during heating, which ensure the formation of a film of crystallites with characteristic sizes of 100–200 nm and long dendritic structures with a length of more than 50 μm. A spacecharge-limited current regime has been registered, as well as hysteresis due to ion migration.

Impedimetric biosensors are used for detecting a wide range of analytes. The detection principle is a perspective for the development of new types of analytical devices for biomolecular diagnosis of diseases. Of particular interest are biosensors with very high sensitivities, capable of detecting trace amounts of biomarkers or drugs in biological fluids. Impedimetric biosensors possess a potential for increased sensitivity, since their electrodes can be modified with nanostructured materials, in particular zinc oxide. In this work, a miniature biosensor with an array of zinc oxide nanorods synthesized by the hydrothermal method has been created. Protein A was immobilized on the resulting structure, which was previously tested for binding to omalizumab by capillary electrophoresis. Using impedance spectroscopy, it was possible to detect the binding of omalizumab at concentrations down to 5 pg/mL. The resulting structures are suitable for creating reusable biosensor systems, since ZnO-coated electrodes are easily cleaned by photocatalytic decomposition of the bound molecules. The biosensor is promising for use in Point-of-Care systems designed for fast, multimodal detection of molecular markers of a wide range of diseases.

In the paper, the properties of MaPbI3 films made with or without a precipitant have been investigated. The samples had a planar geometry based on ceramic substrates with interdigitated gold electrodes and also based on glass substrates. The samples were irradiated with green light from a LED source, and a special setup was used to measure current-voltage (I-V) characteristics. The polycrystalline films exhibited high sensitivity (an increase in current by about 2 orders upon irradiation). The width of their optical band gap was the same regardless of the use of the precipitant but the maximum trap-filling voltages turned out to be very sensi-tive to such use. According to optical microscopy, the film microstructure was characterized by a growth of large long dendritic structures, i. e., the nucleation occurred in the solution mass during the films' making. This growth mechanism may be convenient for the use of MaPbI(3) films in photodetectors.

The effect of an increase in the electrical conductivity of a system of zinc oxide nanorods by a factor of 105 during atomic layer deposition of a thin dielectric layer of aluminum oxide was found. It is shown that a change in the electrical conductivity of zinc oxide during atomic layer deposition of aluminum oxide on the surface is also observed for thin polycrystalline layers of zinc oxide. A study of polycrystalline layers of zinc oxide coated with aluminum oxide using ultraviolet and X-ray photoelectron spectroscopy is presented. Based on the results of photoelectron spectroscopy, two main factors for changing the electrical conductivity are proposed, which consist in the formation of a two-dimensional electron gas at the ZnO|Al2O3 interface and doping of the near-surface region of zinc oxide with aluminum atoms. Keywords: nanorods, zinc oxide, aluminum oxide, atomic layer deposition, transparent electrodes, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy.

Currently, new nanostructured materials based on composite metal oxides are of great interest for the development of gas sensors with improved functional characteristics. In this work, zinc oxide nanowires were synthesized by hydrothermal method. Hierarchical ZnO/ZnFe2O4 nanostructures were obtained by immersion of zinc oxide layers in ferrous sulphate aqueous solutions of different concentrations. Zn-Sn-O nanostructures were synthesized by hydrothermal processing of ZnO nanowires in an aqueous-alcohol solution of potassium stannate and urea. The mechanism of composite nanostructures is considered. It was found that the sensitivity of composite structures to isopropyl alcohol vapors significantly exceeds the one of initial zinc oxide nanowires. The improvement of gas-sensitive properties is associated with the presence of various types of surface centers that participate in the adsorption and oxidation of isopropyl alcohol.

This article shows the effect of a strong increase in the electrical conductivity of a coating of ZnO nanorods when a thin dielectric layer of aluminum oxide is deposited on their surface. It is shown that the initial ZnO nanorods have intrinsic point defects, and the deposition of a thin dielectric layer of aluminum oxide affects the optical density spectrum of the nanorods. A strong increase in the electrical conductivity of ZnO nanorods is associated with the inclusion of aluminum atoms in the defect crystal lattice of the near-surface region of the ZnO nanorod and its doping. The obtained uniform coatings of conducting ZnO nanorods can be used as nanostructured transparent conducting electrodes for the formation of bulk heterojunctions of photovoltaic structures.

Наностержни оксида цинка синтезированы гидротермальным методом. Проведена обработка полученных образцов в водно-спиртовом растворе станната калия и мочевины при 170°С в течение 30 и 60 минут. В результате получены наноструктуры Zn - Sn - O. Химический состав поверхности образцов ZnO и Zn - Sn - O исследован с помощью рентгеновской фотоэлектронной спектроскопии. Проанализирована их чувствительность к парам изопропилового спирта (1000 мд) при температурах 120 °С, 180°С, 250 °С. Показано перераспределение электронной плотности при формировании композитных наноструктур Zn - Sn - O, проявляющееся в химическом сдвиге пиков O1s и Zn2p. Это свидетельствует о перестроении химических связей при замещении атомов цинка оловом. Обнаружено, что чувствительность композитных структур к парам изопропилового спирта значительно превышает чувствительность ZnO во всем исследуемом температурном диапазоне. Улучшение газочувствительных свойств связано с наличием в образцах системы Zn - Sn - O поверхностных центров различного типа, принимающих участие в адсорбции и окислении изопропилового спирта. Zinc oxide nanorods were synthesized by the hydrothermal method. The obtained samples were processed in an aqueous-alcohol solution of potassium stannate and urea at 170 °C during different times. As a result, Zn - Sn - O nanostructures were obtained. The surface chemical composition of ZnO and Zn - Sn - O was studied using the X-ray photoelectron spectroscopy. Its sensitivity to vapors of isopropyl alcohol (1000 ppm) at 120 °C, 180 °C, 250 °C was analyzed. The electron density redistribution during the Zn - Sn - O composite nanostructures formation manifests itself in the chemical shift of the O1s and Zn2p peaks. It confirm the rearrangement of chemical bonds when zinc atoms are replaced by tin ones. It was found that the sensitivity of composite structures to isopropyl alcohol vapors significantly exceeds that of ZnO in the entire temperature range under study. The improvement of gas-sensitive properties is associated with the presence of various types of surface centers in the Zn - Sn - O samples that participate in the adsorption and oxidation of isopropyl alcohol.

Ways of creating new generation biosensors for multiparametric express diagnostics based on molecular recognition and direct fluorimetric registration of a peptide aptamer — protein marker complex were considered. The biosensor platform comprises a microfluidic channel for delivery sample solutions, coupled with flow-through zones containing covalently attached arrays of peptide probes — aptamers. An outer glass window of the biochip assembly contains a layer of luminophore ZnS:Cu, bound on it via an acrylic lacquer and intended for the re-emitting native fluorescence of bound proteins into the longer wavelength range, more efficient in registering signals with CMOS sensors. The aptamers were designed using "Protein 3D" program for analysis of spatial complementarity of protein structures. The peptide, complementary to Troponin T, was modified by replacement of aromatic amino acid residue while maintaining the spatial configuration. The complementarity of peptide and Troponin T was confirmed using a capillary electrophoresis-on-a-chip. Biosensors are manufactured using thick-film technology and photolithography. The fluorescence of marker proteins was excited using UV-LED with a radiation wavelength of 275 nm. The limit of detection achieved for Troponin T was 6 ng/ml.

This work is focused on the study of the morphology of porous anodic alumina membranes formed in electrolytes based on organic and mineral acids. The relationship between synthesis conditions and geometric parameters of membranes is presented. The analysis of AFM images was performed and the fractal dimensions of the samples were determined. The electrical characteristics of membranes are studied by impedance spectroscopy. A theoretical model is described to explain the processes in the oxide layer.

The work is focused on the study of the gas sensitivity of structures based on ZnO nanorods at room temperature under conditions of ultraviolet irradiation. Nanostructured layers of ZnO nanorods were formed on ceramic substrates with interdigitated electrodes. The gas sensitivity of nanostructured ZnO layers to isopropyl alcohol vapor upon heating and at room temperature with ultraviolet irradiation has been studied. It is shown that nanostructured ZnO coatings under ultraviolet irradiation have sufficient sensitivity for practical use.

Zinc oxide nanowires were synthesized by hydrothermal method using cetyltrimethylammonium bromide (CTAB) as a surfactant. Samples of nanwires doped with iodine and bromine were also prepared. The influence of CTAB and doping on the microstructure and surface functional composition of samples was analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. It was found that doping with iodine and bromine leads to an increase in the concentration of OH groups on the surface of zinc oxide nanowires. ZnO nanocrystals grow separately from a single center when CTAB is added to growth solution.

The formation of zinc stannate nanostructures, which are of interest for sensorics, solar power, and transparent conductive electronics, has been considered. The structures have been synthesized by the hydrothermal method, with zinc oxide nanorods used as references in the case of synthesis time variation, and studied by X-ray photoelectron spectroscopy. This method has been shown to be effective for analyzing zinc stannate formation.