Green synthesis of Au 3+ –yttrium co-doped TiO 2 nanoparticles using gambier leaves extract: structural, optical, and biomedical

This study reports the green sol–gel–hydrothermal synthesis of bi-metal Au–Y co-doped TiO2 using Uncaria gambir leaf extract as a catechin rich capping agent. X-ray diffraction confirmed phase pure anatase TiO2 after calcination at 500 °C, with crystallite sizes of—1–17 nm based on (101) reflections and slight shifts indicating substitution by Au3+ and Y3+ ions. UV–Vis diffuse reflectance spectroscopy revealed visible-light absorption enhancement and indirect band-gap narrowing from 3.16 to 3.04 eV. FE-SEM images showed agglomerated nanospherical structures (30–75 µm) composed of smaller crystallites, while EDX analysis detected the presence of Au, Y, Ti, and O in co-doped samples. Under 365 nm irradiation, Au3–Y3/TiO2 exhibited superior antibacterial activity against Staphylococcus aureus ATCC 25923 and Salmonella sp., attributed to band-gap narrowing and reactive oxygen species generation. In addition, the best-performing co-doped sample achieved strong antioxidant capacity with ∼89 ± 0.1% DPPH scavenging (IC50 ≈ 45.3 mg L−1) and showed higher anti-inflammatory compared with undoped TiO2. The synergistic effect of Au–Y co-doping and plant-mediated synthesis produced eco-designed anatase TiO2 with tuned microstrain, crystallite size, and enhanced multifunctional bioactivity. These findings highlight the promise of Au–Y/TiO2 nanostructures as sustainable photocatalysts for biomedical applications.