The sensitive detection of harmful gases, in particular nitrogen dioxide, is very important for our health and environment protection. Therefore, many papers on sensor materials used for NO₂ detection have been published in recent years. Materials based on graphene and reduced graphene oxide deserve special attention, as they exhibit excellent sensor properties compared to the other materials. In this paper, we present the most recent advances in rGO hybrid materials developed for NO₂ detection. We discuss their properties and, in particular, the mechanism of their interaction with NO₂. We also present current problems occuring in this field.

In this paper, various graphite oxide (GO) and reduced graphene oxide (rGO) preparation methods are analyzed. The obtained materials differed in their properties, including (among others) their oxygen contents. The chemical and structural properties of graphite, graphite oxides, and reduced graphene oxides were previously investigated using Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). In this paper, hierarchical clustering analysis (HCA) and analysis of variance (ANOVA) were used to trace the directions of changes of the selected parameters relative to a preparation method of such oxides. We showed that the oxidation methods affected the physicochemical properties of the final products. The aim of the research was the statistical analysis of the selected properties in order to use this information to design graphene oxide materials with properties relevant for specific applications (i.e., in gas sensors).

The Au/Pd/Ti–SiO₂-(n) GaAs properties have been analyzed via impedance spectroscopy (IS), as well as DLTS and ICTS, to identify the origin of electron processes responsible for existence of constant phase elements (CPE) in an equivalent circuits of that structure. We showed that CPEs connected in series with resistance represents the electron processes associated with deep levels in GaAs and/or interface states at SiO₂-(n) GaAs interface, depending on the value of n of CPE parameter. CPE with n close to 1 characterize the electron processes associated with EL2 deep level, and CPE with n = 0.5–0.65 the complex electron processes associated with EL3 deep level and interface states together. We stated that constant phase elements in equivalent circuits of MIS-GaAs structures with large frequency dispersion of electrical characteristics can be the result of more than one electron process.

Hydrogen can be considered a clean energy carrier with zero carbon emissions, produced from renewable energy sources. However, hydrogen is a highly flammable gas and can form explosive mixtures with oxygen; hence, sensing techniques are essential for timely leak detection. This paper presents the experimental characterization of a hydrogen sensor based on sensing material consisting of thermally exfoliated/reduced graphene oxide (rGO) films deposited on a sensor device by the drop-coating technique. The measurement of changes in electrical resistance due to hydrogen gas exposure operating at different temperatures (27°C, 90°C, and 150°C) is carried out in a gas chamber with a known concentration of hydrogen in constant air flow. In addition, a generalized mathematical formulation is provided for the dependence of hydrogen gas concentration, temperature, and sensor resistance for the hydrogen gas sensor based on exfoliated/reduced graphene oxide.

\(\hbox {ZnS}_{x}\hbox {Se}_{1-x}\) single crystals with different S contents were examined. The crystals were grown by the modified Bridgman method. Thermal, optical, and electrical measurements for a solid solution of \(\hbox {ZnS}_{ x}\hbox {Se}_{1-x}\) crystals are presented and analyzed to determine the influence of composition on the thermal diffusivity, the electrical resistivity, the relative permittivity, and the energy gap. The thermal measurement was based on the thermal wave method with detection using the mirage effect. For interpretation of the experimental data, a thermal model of a layered system was adopted. The results showed that the thermal diffusivity of samples decreases with an increase of the S content \(x\) . The electrical resistivity of investigated samples was measured by the constant voltage method. The relative permittivity was determined by dielectric spectroscopy and decreased with increasing sulfur content in the ZnSe. Further, the optical bandgap of \(\hbox {ZnS}_{ x}\hbox {Se}_{1-x}\) was determined from photoluminescence spectra. Possible correlations between the thermal diffusivity, the optical bandgap, and electrical properties were studied. The obtained results showed a clear dependence of those parameters on the S concentration in the sample.