Ag-doped WO₃ (Ag–WO₃) films were deposited on a soda-lime glass substrate via a facile spray pyrolysis technique. The surface roughness of the films varied between 0.6 nm and 4.3 nm, as verified by the Atomic Force Microscopy (AFM) studies. Ammonia (NH₃)-sensing measurements of the films were performed for various concentrations at an optimum sensor working temperature of 200 °C. Enrichment of oxygen vacancies confirmed by X-ray Photoelectron Spectroscopy (XPS) in 1% Ag–WO₃ enhanced the sensor response from 1.06 to 3.29, approximately 3 times higher than that of undoped WO₃. Limit of detection (LOD) up to 500 ppb is achieved for 1% Ag–WO₃, substantiating the role of Ag in improving sensor performance.

Pristine WO₃ and Zn-doped WO₃ were synthesized using the spray pyrolysis technique to detect ammonia gas. The prominent orientation of the crystallites along the (200) plane was evident from X-ray diffraction (XRD) studies. Scanning Electron Microscope (SEM) morphology indicated well-defined grains upon Zn doping with a smaller grain size of 62 nm for Zn-doped WO₃ (Zn: WO₃) film. The photoluminescence (PL) emission at different wavelengths was assigned to defects such as oxygen vacancies, interstitial oxygens, localized defects, etc. X-ray Photoelectron spectroscopy (XPS) studies confirmed the formation of oxygen vacancies in the deposited films. The ammonia (NH₃) sensing analysis of the deposited films was carried out at an optimum working temperature of 250 °C. The sensor performance of Zn: WO₃ was enhanced compared to pristine WO₃ at 1 ppm NH₃ concentration, elucidating the possibility of the films in sensing applications.

The influence of Bi doping on the structural and thermoelectric properties of Cu₂Se is presented in this work. Cu_2−xBi_xSe (x = 0.00, 0.004, 0.008, 0.012) samples were prepared using conventional solid-state reaction techniques. According to room temperature XRD results, Cu_2−xBi_xSe samples have a monoclinic crystal structure. Doping Bi to the Cu site acts as a donor, lowering the hole concentration, except for the sample with x = 0.004. The resistivity of the Cu_2−xBi_xSe sample increases with an increase in Bi content. Seebeck coefficient data confirm that the holes are the charge carriers in Cu_2−xBi_xSe samples. At 700 K, the Cu_1.988Bi_0.012Se sample has the highest power factor of 1474 μWm⁻¹K⁻², showing great potential in developing high-performance Cu₂Se based thermoelectric materials.

Cr-doped and electron beam-irradiated WO ₃ films, synthesized by spray pyrolysis, exhibit ultra-sensitive NO ₂ detection (<1 ppm), with a 3.2x response enhancement and fast response/recovery times (<30 s), due to oxygen vacancy modulation.