Microwave-assisted synthesis of SnO₂-NiO nanocomposites for the enhanced photocatalytic dye degradation and biological applications

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.