Cu-doped Cr ₂ O ₃ thin films were deposited onto glass substrate by the sol–gel dip-coating (SGDC) process using dopant values of 0, 3, 6, 9 and 12%. The Chromium (III) Nitrate Nonahydrate [Cr(NO ₃ ) ₃ ·9H ₂ O] was used as a Cr source, whilst for the dopant, the corresponding nitrate (Cu(NO ₃ ) ₂ ) was used. The crystal structure, as well as the optical and electrical properties were examined. XRD data showed that the films with a high degree of crystallinity were rhombohedral Cr ₂ O ₃ phase. The crystallite size reduces with increase in Cu doping proportion. The AFM results indicate a decrease in the surface roughness of the doped Cr ₂ O ₃ : Cu thin films. The UV-Vis spectra of the Cu doped-Cr ₂ O ₃ films showed high transparency in the visible region. The optical band gap of Cr ₂ O ₃ thin films decreases with increasing in Cu doping rate. The Nyquist plot shows that the equivalent circuit of Cu doped-Cr ₂ O ₃ films is a parallel circuit R _p C _p . As the concentration of Cu increases, Resistance R _P regresses while capacitance C _p increases.

In this study, pure ZnCo₂O₄ and SnO₂/ZnCo₂O₄ mix photocatalysts have been synthesized by the sol-gel process with three different SnO₂ loading percentages (10, 20, and 30 wt %). Their photocatalytic activities were assessed on the degradation of organic pollutants in water under visible illumination. The structural, morphological, and optical properties were analyzed by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), nitrogen adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), and UV–Visible diffuse reflectance measurements. The results have shown that the materials are composed of a crystalline ZnCo₂O₄ matrix with a decrease in crystallite size with the amount of SnO₂. Weakly crystalline SnO₂ is also observed for loaded samples. The specific surface area is modified with the loading ratio. The evaluation of the photoactivity of the samples under visible light for the degradation of p-nitrophenol has highlighted that all materials are highly photoactive under visible light thanks to heterojunction between the two oxides. An application test has been conducted on a dye, congo red, showing the same tendencies. An optimal amount of SnO₂ loading is observed for the sample containing 20 wt % of SnO₂. A comparison with commercial Evonik P25 showed that the materials developed in this work have five to six times better efficiency under visible light, leading to a promising photocatalyst material.

Clay minerals are frequently used in adsorption processes with aqueous solution; it was found that the adsorption properties of clays change when the samples are modified. In this context, polyaniline-modified clay nanocomposite (at 10 %) was prepared by in situ polymerization processes. The structural and morphological characteristics of the synthesized material are systematically examined by X-ray diffraction, scanning electron microscopy, thermo-gravimetry, differential scanning calorimetry and infrared spectroscopy techniques. The adsorption property of the modified clay was evaluated for the removal of a reactive dye (methylene blue) from aqueous solution at room temperature (25 °C) via batch adsorption.