Semiconductor metal oxides (SMOxs) are widely used in gas sensors due to their excellent sensing properties, abundance, and ease of manufacture. The best examples of these sensing materials are SnO2 and TiO2 that have wide band gap and offer unique set of functional properties; the most important of which are electrical conductivity and high surface reactivity. There has been a constant development of SMOx sensor materials in the literature that has been accompanied by the improvement of their gas-sensitive properties for the gas detection. This review is dedicated to compiling of these efforts in order to mark the achievements in this area. The main material-specific aspects that strongly affect the gas sensing properties and can be controlled by the synthesis method are morphology/nanostructuring and dopants to vary crystallographic structure of MOx sensing material.

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The features of the properties and creation of nanocomposite metal oxide materials, especially TiO2, ZnO, SnO2, ZrO2, and Fe3O4, and their applications for ecology are considered in the article. It is shown that nanomaterials based on them are very promising for use in the ecological direction, especially as sorbents, photocatalysts, and sensitive layers of gas sensors. The crystallochemical characteristics, surface structure, and surface phenomena that occur when they enter the water and air environment are given for these metal oxides, and it is shown that they play a significant role in obtaining the sorption and catalytic characteristics of these nanomaterials. Particular attention is paid to the dispersion and morphology of metal oxide particles by which their physical and chemical properties can be controlled. Synthesis methods of metal oxide nanomaterials and ways for creating of nanocomposites based on them are characterized, and it is noted that there are many methods for obtaining individual nanoparticles of metal oxides with certain properties. The main task is the correct selection and testing of parameters. The prospects for the production of metal oxide nanocomposites and their application for environmental applications are noted, which will lead to a fundamentally new class of materials and new environmental technologies with their participation.

In the past decade, MXenes, a new class of advanced functional 2D nanomaterials, have emerged among numerous types of electrode materials for electrochemical energy storage devices. MXene and their composites have opened up an interesting new opportunity in the field of functional materials, owing to their transition metal nitrides/carbides/carbonitride-based unique layered structures, higher electrical and thermal conductivity, higher charge carrier mobility, high negative zeta-potential, high mechanical properties, tunable bandgap, superior hydrophilicity, metallic nature and rich surface chemistry, which enhance the number of metal active redox sites on the surface and short ion diffusion path. However, in the case of electrochemical energy storage applications, the unavoidable problem of aggregation and nanosheet restacking significantly reduces the accessibility of the active surface sites of MXene materials for electrolyte ions. Currently, there is a number of research efforts devoted to solutions in order to avoid these deficits. This Review complies extensively with the recent advances in the application of MXene-based materials in the energy storage devices such as batteries and supercapacitors. Particular attention is paid to the understanding of the relation of MXenes chemical composition, and morphology with their electrochemical performances. Moreover, the challenges of MXenes and MXene-based composited for the commercial application are considered and the ways to overcome their drawbacks are provided. Finally, opportunities given with MXenes for future research on novel energy storage materials are highlighted.

Corrosion inhibitors are the only most widely applied method for corrosion protection of metallic materials and are of particular importance in industry. Nowadays, the synthesis of corrosion inhibitors using traditional multistep reactions is highly restricted because of the increasing demands of "green chemistry". Plant materials and biomass wastes are ideal green candidatures to replace traditional toxic corrosion inhibitors. Literature survey reveals that different extracts of the plant and agro-food wastes contain naturally phytochemical compounds which have antioxidant properties have been effectively employing as sustainable inhibitors for the corrosion of different metals and alloys. Nevertheless, despite the numerous research papers, the reviews in which the correlation between the antioxidant/free radical scavenging activity of the extracts and their inhibition action is explained are not represented in the literature. This paper provides a brief overview of current knowledge in what kind of methods are used to estimate the antioxidant content, which classes of compounds provide higher antiradical activity and poses questions that we need to answer in order to use parameter of the antioxidant activity as a predictive index for performance evaluation of the plants/biomass wastes extracts as corrosion inhibitors. The conclusion is that no single mechanism of antioxidant actions and anticorrosive protection is operative in plant/wastes extracts. The high inhibitory efficiency is predicated on a number of complementary processes working holistically. By developing the theoretical basis and mechanism of action between the anticorrosive and antioxidant properties of plant extracts, it is possible to create predictive tools for selecting plant extract and further obtaining anti-corrosion protection based on it.