Nanocomposites containingTiO₂ and activated carbon were obtained by the sol-gel method in the presence of Brij 58 surfactant. The sample with a higher surface area (185.6 m²/g) was promoted with Fe by impregnating it with aqueous solution of Fe(NO₃)₃. The obtained iron loadings, measured using X-ray fluorescence, were 0.83%, 3.30% and 7.17%. TiO₂ anatase was identified in all the samples by X-ray diffraction and Raman spectroscopy, but the presence of iron oxides could not be detected. However, infrared spectroscopy indicated the existence of Fe-O and Fe-O-Ti bonds. X-ray photoelectron spectroscopy revealed the presence of Fe²⁺ for samples with a lower Fe content and a mixture of Fe²⁺ and Fe³⁺ in the sample with 7.17% Fe. UV-Vis and photoluminescence spectroscopy showed the presence of carbon and Fe alongside TiO₂. This combination led to new properties due to the generation of intermediate energy levels and defects, contributing to an enhancement in the photocatalytic performance. The highest photodegradation efficiency of Congo red in solution (84.46%) was obtained for the sample with 7.17% Fe under visible light irradiation and acidic conditions. The synergistic contribution of dye adsorption and photodegradation was demonstrated, taking into account ZPC values of nanocomposites. Kinetic studies were completed with reaction mechanisms based on the results obtained in the presence of scavengers.

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. Photocatalysts were obtained by modifying these supports with Ag, Fe, and AgFe (each metal around 1% mass). The characterization results showed a stronger influence of titania precursors, surfactants, and AC on the texture and an insignificant effect on the crystalline structure and morphology of the obtained materials. X-ray photoelectron spectroscopy revealed the effects of AC and Fe on the Ag⁰ concentration and of Ag on Fe-reduced species. Based on this information, the results obtained by H₂-TPR, UV–Vis, Raman, and photoluminescence spectroscopy were explained. The performance of the photocatalysts was evaluated in the degradation of Congo Red (CR) and Crystal Violet (CV) dyes under UV and visible light. The Ag-TiO₂ sample exhibited the best activity in degrading CR at acidic pH and in degrading CV under basic conditions. In visible light, we observed the significant effects of the surface plasmon resonance, AC, Ag, and Fe on the activity in CR photodegradation. The proposed kinetics and mechanisms complete the study of the reactions.

Titanium dioxide, TiO₂, plays an important role due to its catalytic properties and high chemical

Boron (B)-modified SnO₂ samples with various B concentrations (1, 2, and 5 at%) were successfully synthesized using the sol–gel method. The effect of the B/SnO₂ molar ratio on the crystal structure, microstructure, optical, and photocatalytic properties was investigated. The samples were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption experiments, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Diffuse reflectance UV–Vis (DR UV–Vis) and photoluminescence (PL) spectroscopy. A decrease in particle size was observed with increasing B concentration. The B-doped samples exhibited a higher fraction of microporosity and a larger specific surface area than those of undoped SnO₂. FTIR spectra display characteristic absorption of B species. The band gap values were lower than that of bulk SnO₂, and the PL results indicated a reduced electron–hole recombination rate upon boron doping. The presence of defects, such as oxygen vacancies, is highlighted. The nanoparticles exhibited excellent photocatalytic activity toward the degradation of crystal violet (CV) dye, achieving a removal efficiency under UV irradiation of over 90% for the 5 at% B-doped SnO₂ sample after 90 min.