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Currently, adsorption gas sensors are of great interest for environmental monitoring. The approaches to improving their properties include synthesis of nanostructured materials of various shapes and modification of the metal oxide chemical composition. The aim of this work is to develop ways to improve the sensor properties of zinc oxide nanowires by changing the surface structure during processing in solutions of tin and iron compounds, as well as adding special precursors during their synthesis. The layers consisting of zinc oxide nanowires were produced by hydrothermal method. Ternary Zn-Sn-O and Zn-Fe-O nanosystems were synthesized as a result of processing of zinc oxide nanowires in solutions containing potassium stannate and iron sulfate, respectively. ZnO nanowires were also synthesized in a solution containing sodium bromide in addition to the general precursors. The surface chemical composition was analyzed using X-ray photoelectron spectroscopy. Sensor properties were investigated by detecting acetone, isopropanol and methanol vapors. It was shown that the sensor response of the produced samples exceeds the response of the initial zinc oxide nanowires. The samples of Zn-Sn-O ternary oxide system have the best response. The improvement of the sensor response may be associated with an increase in the content of adsorbed oxygen ions on the surface of the samples, the presence of metal cations with different properties as well as the formation of heterostructures.

When comparing the simulated and experimental optical conductivity, the electronic structure of the aluminum film and powder at room temperature was studied. The positions and occupation of their surface states by electrons are determined. It has been established that the dispersion of aluminum leads to a sharp increase in the filling of its surface states with electrons. Since adsorption processes are most clearly manifested in a change in the characteristics of surface states, such states can be considered as an adsorption center. Thus, we can conclude that the dispersion of aluminum leads to an increase in the number of its adsorption centers. [ABSTRACT FROM AUTHOR]

Numerous attempts have been made to enhance the corrosion inhibition (%IE) of organic compounds. Each method has its own advantages and drawbacks. One of the important methods of enhancing %IE of organic compounds is their chemical functionalization which involves addition of polar functional groups, which enhances %IE due to combined effect of enhanced solubility and the number of adsorption centers. A large number of organic compounds derivatized through covalent and noncovalent functionalization are extensively used as corrosion inhibitors. It is well documented that properly functionalized organic compounds show higher %IE than the parent compounds. Other important factors that usually affect corrosion inhibition performance are transportability rate, immersion time, planarity, strength of electrolyte, and synergism. In the present article effect of these factors has been discussed. A proper understanding of these factors will help corrosion scientists and engineers in designing and synthesis (formulation) of effective corrosion inhibitors for industrial scale applications. [ABSTRACT FROM AUTHOR]

An expression is obtained for the energy band bending eφ on the surface of the SnO film in the clean air + hydrogen mixture. It is assumed that the value of eφ depends not only on the surface charge density of adsorbed oxygen ions O, but also on the negative charged hydroxyl groups (OH). The results of the analysis of the dependences of eφ on the hydrogen concentration $$ {\mathrm{n}}_{{\mathrm{H}}_2} $$ and the absolute humidity of the gas mixture obtained during the operation of the sensor in the thermo-cyclic mode are presented. A method for the determining $$ {\mathrm{n}}_{{\mathrm{H}}_2} $$ in the examined gas mixture is proposed. The method based on the dependence of eφ on the hydrogen concentration established during the calibration of the sensor is proposed. The dependences of the energy band bending on the SnO surface at $$ {\mathrm{n}}_{{\mathrm{H}}_2} $$ = 0 and the conductivity of the sensor on its temperature during the heating period are discussed. [ABSTRACT FROM AUTHOR]

The results of studying the dependence of the energy band bending at the interface of contacting SnO microcrystals in the polycrystalline tin dioxide film on the humidity level of clean air and hydrogen concentration in the gas mixture of clean air + H are presented. The experimental results showed that the bending of energy bands in SnO is decreased under exposure to the water vapors and molecular hydrogen. The presence of two types of the adsorption centers for water molecules on the surface of SnO is found. It is shown that at the absolute humidity of the gas mixture above 12 g/m, the HO and H molecules are adsorbed on the same centers, whose surface density is of 10 сm at a concentration of donor impurity in SnO equal to 1018 сm. [ABSTRACT FROM AUTHOR]

Abstract: The amount of water adsorbed on different centers on the surface of oxalic acid alumina films is a function of the anodizing voltage. It is decreased with increasing the anodizing voltage from 20 up to 50V, came up to maximum value at 20–30V and slightly increased at voltages above 50V. Water adsorption by oxide films formed at voltages below 50V can be due to the negative surface charge that is present on the alumina surface. The negative surface charge disappears in the films formed at voltages higher than 50V, and thus, the water is adsorbed on aluminum ions in a tetrahedral and octahedral environment. The correlation between anodizing conditions of aluminum in oxalic acid and the structure and composition of anodic alumina was established by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), thermogravimetric and differential thermal analyses (TG/DTA). [Copyright &y& Elsevier]