Facile Low-Cost Synthesis of Highly Photocatalitycally Active Zinc Oxide Powders

The industrial waste can cause significant harm to human health and to the environment. Organic dyes in particular are environmentally dangerous since they may cause the death of aquatic life or contaminate the feed chain. Thus, one of the current research fields consists of the development of an inexpensive and environmentally friendly method to purify wastewater from organic contaminants. Among the others, Zinc oxide (ZnO) is considered one of the most effective photocatalysts for the decomposition of organic pollutants in water. In this work, we developed a highly efficient low-temperature and environmentally safe synthesis method to obtain photocatalytically active nanostructured ZnO by chemical precipitation from a solution. The effect of the technological conditions of synthesis on the photocatalytic properties is considered in detail, the correlation with the morphology, structural, and optical properties of the synthesized ZnO samples is determined. It was found that the maximum photocatalytic activity with respect to the decomposition of the dye rhodamine-B (RhB) is achieved for samples synthesized at NaOH molar concentration from 0.4 to 0.7 M; in this case, the sizes of crystallites along the crystallographic direction 002 reach maximum values of ∼42 nm. On the contrary, the sizes of crystallites along the directions 100 and 101 decrease monotonically from 30 to 25 nm with an increase in the molar concentration of NaOH from 0.14 to 1 M

Creating a virtual device for processing the results of sorption measurements in the study of zinc oxide nanorods

The work is devoted to the creation of a virtual device (computer program) for processing the results of sorption analysis of nanomaterials, including for estimating the size of nanoparticles based on the specific surface area. The obtained evaluation results were compared with the scanning electron microscopy data. Photocatalytically active zinc oxide samples were chosen as the object of the study

STRUCTURAL PROPERTIES OF ZnO NANOPOWDERS SYNTHESIZED BY THERMAL DECOMPOSITION

Zinc oxide nanostructures attract considerable attention of researchers due to their unique properties such as electrical conductivity, piezoelectric properties, optical transparency, emission, wide forbidden zone. Zinc oxide nanopowders are obtained by various methods: hydrothermal synthesis, sol-gel method, pyrolysis, chemical precipitation from solution and others. The task of development of low-cost methods of zinc oxide synthesis with high reproducibility is actual. The thermal decomposition method is a controlled relatively inexpensive method that can enable large scale production without the use of complex equipment and expensive materials.  In this work, nanostructured ZnO samples were prepared by thermal decomposition of zinc acetate dehydrate at temperatures 400 ̊С and 700 ̊С. The influence of such synthesis parameters as duration and temperature on the morphology and structural properties of the obtained samples was investigated. It was found that the morphology of the synthesised ZnO samples significantly depends on the synthesis temperature. The obtained Raman scattering spectra show characteristic peaks of zinc oxide and carbon. An efficient, inexpensive method for the synthesis of zinc oxide nanoparticles with controlled morphology, promising for use as photocatalysts, the basis for the development of sensor devices, is presented

Influence of plasma and heat treatments on the properties of ZnO nanorods

Oxide semiconductor nanostructured materials attract considerable attention of researchers due to their efficiency in electronics, optics, photonics, and other applications. One-dimensional semiconductor nanostructures such as nanowires, nanorods, and nanotubes are widely used for both academic research and industrial applications. Such nanostructures are useful materials for investigating of the dependence of electrical, thermal, and mechanical properties on dimensionality and size reduction. Actual study is the effect of postgrowth treatments on the properties of synthesized materials in order to improve their optical and electrical characteristics. In this work, we consider the effect of thermal annealing and treatment in hydrogen plasma on the morphology, optical, structural, and photoluminescent properties of samples consisting of zinc oxide nanorods obtained by chemical solution deposition. It is shown that the passivation of charged oxygen acceptors on the surface of grain boundaries upon short-term treatment in hydrogen plasma followed by thermal treatment in air makes it possible to activate the photoluminescence of ZnO obtained by chemical solution deposition and to obtain conductive transparent layers of ZnO nanorods with intense photoluminescence

Stabilization of the surface of ZnO films and elimination of the aging effect

Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O(2), where O(2) adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p(3/2) peak at 1022.2 ± 0.2 eV and Zn2p(1/2) peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero

Morphology Effects on Electro- and Photo-Catalytic Properties of Zinc Oxide Nanostructures

Environmental problems are among the most pressing issues in the modern world, including the shortage of clean drinking water partially caused by contamination from various industries and the excessive emission of CO2 primarily from the massive use of fossil fuels. Consequently, it is crucial to develop inexpensive, effective, and environmentally friendly methods for wastewater treatment and CO2 reduction, turning them into useful feedstocks. This study explores a unique method that addresses both challenges by utilizing ZnO, which is recognized as one of the most active semiconductors for photocatalysis, as well as a cost-effective electrocatalyst for the CO2 reduction reaction (CO2RR). Specifically, we investigate the influence of the morphology of various ZnO nanostructures synthesized via different low-cost routes on their photocatalytic properties for degrading the rhodamine-B dye (RhB) and on their electrocatalytic performance for the CO2RR. Our results show that the ZnO lamella morphology achieves the best performance compared to the nanorod and nanoparticle structures. This outcome is likely attributed to the lamella’s higher aspect ratio, which plays a critical role in determining the structural, optical, and electrical properties of ZnO