Experimental data on the elemental vapor-phase synthesis of aligned arrays of ZnO nanorods on Si substrates are summarized. A model of the self-catalytic growth of ZnO nanorods via the vapor-liquid-cr

ZnO nanorods are promising materials for many applications, in particular for UV detectors. In the present paper, the properties of high crystal quality individual ZnO nanorods and nanorod arrays grown by the self-catalytic CVD method have been investigated to assess their possible applicationsfor UV photodetectors. X-ray diffraction, Raman spectroscopy and cathodoluminescence investigations demonstrate the high quality of nanorods. The nanorod resistivity and carrier concentration in dark is estimated. The transient photocurrent response of both as grown and annealed at 550 °C nanorod array under UV illumination pulses is studied. It is shown that annealing increases the sensitivity and decreases the responsivity that is explained by oxygen out-diffusion and the formation of near surface layer enriched with oxygen vacancies. Oxygen vacancy formation due to annealing is confirmed by an increase of green emission band intensity.

Sorption of Ag, Cu, Pb, Cd, Fe and Mg cations on multi-walled carbon nanotubes (MWCNTs) produced by CVD method has been investigated in static and dynamic modes. Correlation between synthesis temperature of MWCNTs and their sorption capacity has been demonstrated. It was shown that concentration of carbonyl groups on the oxidized surface of MWNTs increases with the decrease of the synthesis temperature at the same oxidation conditions. Maximal sorption capacities have MWCNTs synthesized at 400°C and then treated by HNO₃ concentrated at 120°C. It may be explained by the formation of more defective material at low temperature of the MWCNTs synthesis.

An original technique of chemical deposition (CVD) by catalytic pyrolysis of ethanol vapor was used to directly grow multiwall carbon nanotubes (MWCNTs) layers on aluminum foil. The grown nanotubes had excellent adhesion and direct electrical contact to the aluminum substrate. This material was perfect for use in electrochemical supercapacitors. In this work, the possibility of a significant increase in the specific capacity of MWCNTs by simple electrochemical oxidation was investigated. The optimal conditions for improving the characteristics of the MWCNT/Al electrodes were found. Electrochemical treatment of MWCNT/Al electrodes in a 0.005 M Na₂SO₄ solution at a potential of 4–5 V for 20–30 min increased the specific capacity of MWCNTs from 30 F/g to 140 F/g. The properties of modified nanotubes were investigated by X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. A significant increase in the concentration of oxygen-containing functional groups on the surface of MWCNTs was found as a result of electrochemical oxidation. The modified MWCNT/Al electrodes maintained excellent stability to multiple charge–discharge cycles. After 20,000 CVs, the capacity loss was less than 5%. Thus, the results obtained significantly expanded the possibilities of using MWCNT/Al composite materials obtained by the method of direct deposition of carbon nanotubes on aluminum foil as electrodes for supercapacitors.

Zinc oxide is a promising material for the creation of various types of sensors, in particular UV detectors. In this work, arrays of ordered nanorods were grown by chemical vapor deposition. The effect of environmental humidity on the sensing properties of zinc oxide nanorod arrays was investigated, and a prototype UV sensor using indium as an ohmic contact was developed. UV photoresponses were measured for the samples stored in dry and wet atmospheres. The increase in sensitivity and response of the ZnO nanorod arrays was observed after prolonged exposure to a wet atmosphere. A model was proposed to explain this effect. This is due to the formation of hydroxyl groups on the surface of zinc oxide nanorods, which is confirmed by FTIR spectroscopy data. For the first time, it has been shown that after storage in a wet atmosphere, the sensory properties of the structure remain stable regardless of the ambient humidity.

Recently, significant progress has been made in the performance of supercapacitors through the development of composite electrodes that combine various charge storage mechanisms. A new method for preparing composite binder-free MnO₂/MWCNT/Al electrodes for supercapacitors is proposed. The method is based on the original technique of direct growth of layers of multi-walled carbon nanotubes (MWCNTs) on aluminum foil by the catalytic pyrolysis of ethanol vapor. Binder-free MnO₂/MWCNT/Al electrodes for electrochemical supercapacitors were obtained by simply treating MWCNT/Al samples with an aqueous solution of KMnO₄ under mild conditions. The optimal conditions for the preparation of MnO₂/MWCNT/Al electrodes were found. The treatment of MWCNT/Al samples in a 1% KMnO₄ aqueous solution for 40 min increased the specific capacitance of the active material of the samples by a factor of 3, up to 100–120 F/g. At the same time, excellent adhesion and electrical contact of the working material to the aluminum substrate were maintained. The properties of the MnO₂/MWCNT/Al samples were studied by electron probe microanalysis (EPMA), Raman spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. Excellent charge/discharge characteristics of composite electrodes were demonstrated. The obtained MnO₂/MWCNT/Al electrodes maintained excellent stability to multiple charge-discharge cycles. After 60,000 CVs, the capacitance loss was less than 20%. Thus, this work opens up new possibilities for using the MWCNT/Al material obtained by direct deposition of carbon nanotubes on aluminum foil for the fabrication of composite binder-free electrodes of supercapacitors.