The synergistic effect of binary CdTiO₂ and ternary NiCdTiO₂ on the photocatalytic efficiency of TiO₂ nanoparticles was investigated. The SEM analysis demonstrates spherical TiO₂ NPs of different sizes present in agglomerated form. The structural analysis of the nanocomposites reveals a porous structure for TiO₂ with well deposited Cd and Ni NPs. TEM images show NiCdTiO₂ nanocomposites as highly crystalline particles having spherical and cubical geometry with an average particle size of 20 nm. The EDX and XRD analysis confirm the purity and anatase phase of TiO₂, respectively. Physical features of NiCdTiO₂ nanocomposite were determined via BET analysis which shows that the surface area, pore size and pore volume are 61.2 m²/g, 10.6 nm and 0.1 cm³/g, respectively. The absorbance wavelengths of the CdTiO₂ and NiCdTiO₂ nanocomposites have shown red shift as compared to the neat TiO₂ due to coupling with Ni and Cd that results in the enhanced photocatalytic activity. The photocatalytic activity demonstrated that TiO₂, CdTiO₂ and NiCdTiO₂ degrade methylene blue (MB) and methyl green (MG) about 76.59, 82, 86% and 63.5, 88, 97.5%, respectively, at optimum reaction conditions.

This study demonstrates the photocatalytic degradation efficiency of doped NiZnO and co-doped CdNiZnO NPs. Initially, ZnO NPs with a unique mesoporous ellipsoidal morphology were synthesized by simple precipitation and calcination. Powder X-ray diffraction revealed the formation of a hexagonal phase of the wurtzite structure. The average crystallite size of pristine ZnO NPs is 48 nm. The NPs possess higher thermal stability with the surface area, pore volume, and pore size of 9.1302 m²/g, 0.028299 cm³/g, and 12.39819 nm, respectively. Furthermore, different mesoporous doped NiZnO and co-doped CdNiZnO NPs in the range of 34 and 29 nm were synthesized by co-precipitation method and characterized by XRD, EDX, SEM, TEM, PL, Raman, BET analyses and UV–Vis spectroscopy. The calculated optical bandgaps for pure ZnO, doped NiZnO and co-doped CdNiZnO NPs were found to be 3.1, 2.62 and 2.33 eV, respectively. The photocatalytic activity of co-doped CdNiZnO was significantly higher than that of pure ZnO. After 50 min of irradiation, approximately 98% of rhodamine B was degraded by CdNiZnO, compared to 65% with pure ZnO. This enhancement is attributed to the synergistic effects of Ni and Cd, which trap electrons and holes, reducing recombination and extending charge carrier lifetimes. The photocatalytic efficiency of the synthesized materials to decompose the RhB dye (30 mgL⁻¹) in aqueous media was tested via Langmuir–Hinshelwood model under UV–visible light. The degradation process followed pseudo-first order kinetic model. The synthesized NPs were re-used for five cycles without any significant decrease in the photodegradation ability. The mechanistic concept of generating reactive oxygen species by electron and hole charge (e‾/h⁺ ) carriers seems to be responsible for the photocatalytic degradation of the dye by CdNiZnO NPs. Zeta potential analysis revealed positive surface charges for all catalysts, with co-doping significantly increasing charge and colloidal stability, thereby supporting the pH-dependent photocatalytic performance.

Pristine ZnO, binary CdZnO, and ternary NiCdZnO nanocomposites were synthesized via simple co-precipitation method and systematically characterized by XRD, SEM, TEM/HRTEM, EDX mapping, Raman spectroscopy, PL, DRS, UV–VIS, and BET analyses. The results confirmed well-crystalline hexagonal wurtzite structures with controlled morphology, mesoporosity, and band-gap tuning (3.2 eV for ZnO, 3.0 eV for CdZnO, and 2.45 eV for NiCdZnO). Photoluminescence analysis revealed reduced electron–hole recombination in the Cd- and Ni-modified nanocomposites. Under UV-VIS irradiation, NiCdZnO achieved 95% degradation of Allura Red (AR) dye within 50 min, compared with 80% for CdZnO and 50% for ZnO, following pseudo-first-order kinetics. COD analysis further confirmed strong mineralization, with NiCdZnO showing 95–100% reduction at 10 ppm, outperforming CdZnO (80%) and ZnO (65%). Radical scavenging experiments indicated the involvement of reactive oxygen species, while recyclability tests demonstrated stable performance. These results indicate that Cd and Ni incorporation into ZnO can generate a synergistic enhancement in photocatalytic activity, and the present study provides a detailed evaluation of this co-modified system for the degradation of AR dye, a target pollutant that has not been widely explored with such nanocomposites.

Photocatalytic degradation is a promising and sustainable approach for the removal of organic pollutants from wastewater; however, the practical application of SnO₂ is limited by rapid electron–hole recombination and poor visible-light absorption. In this study, pristine SnO₂ nanoparticles (NPs) and SnO₂–NiO binary nanocomposites (NCs) were successfully synthesized via a facile microwave-assisted method. The synthesized materials were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, and UV–Vis spectroscopy. The incorporation of NiO effectively modified the optical properties of SnO₂, reducing the band-gap energy from 3.84 eV for pristine SnO₂ to 3.02 eV and 3.28 eV for the 20% and 40% SnO₂–NiO nanocomposites, respectively. The photocatalytic performance was evaluated through the degradation of Safranin O (SO) and Methylene Blue (MB) under UV-VIS irradiation. Among the synthesized photocatalysts, the 20% SnO₂–NiO nanocomposite exhibited the highest photocatalytic activity, achieving degradation efficiencies of 86.54% for SO and 88.16% for MB within 180 min, which were significantly higher than those of pristine SnO₂ NPs and 40% SnO₂–NiO NCs. The enhanced photocatalytic performance is attributed to the formation of an efficient SnO₂–NiO heterojunction, which promotes charge-carrier separation and facilitates interfacial charge transfer. Furthermore, the SnO₂–NiO NCs exhibited promising antioxidant activity, although their antidiabetic activity was comparatively limited. These findings demonstrate that microwave-assisted synthesis of SnO₂–NiO heterojunction NCs provides an effective strategy for enhancing photocatalytic performance while offering potential for environmental remediation and selected biological applications.