Green synthesis of doped TiO2 nanoparticles using Hybanthus enneaspermus: antioxidant and antibacterial evaluation

There is a growing need for eco-friendly techniques to synthesize nanoparticles, with the plant-mediated green synthesis method emerging as an environmentally sustainable alternative to conventional chemical methods. Here, a leaf extract from Hybanthus enneaspermus, a medicinal plant rich in phytochemicals was used as the starting material to synthesize TiO₂ nanoparticles as well as their silver (Ag), gold (Au), and Ag–Au co-doped variants via green hydrothermal routes. This study marks a unique application of plant extract that enables simultaneous co-doping, yielding versatile nanoparticles with enhanced multifunctional properties from a single origination point. These nanoparticles were thoroughly evaluated using XRD, FTIR, SEM, UV–Vis, PL, and EDAX techniques. XRD analysis confirmed the anatase phase with crystallite sizes between 9 and 15 nm; SEM images revealed nanorod-like structures without significant metal doping agglomeration upon doping; EDAX confirmed successful incorporation of Ag and Au; UV–Vis analysis revealed redshift in absorption due to doping; while PL spectra showed decreased intensity which confirmed doping effects as indicating reduced electron–hole recombination as well as enhanced photocatalytic potential. Ag-doped TiO₂ nanoparticles demonstrated strong antibacterial activity against Staphylococcus aureus (zone of inhibition: 39 mm), while Ag–Au co-doped TiO₂ showed superior antioxidant activity with the lowest IC50 value for DPPH scavenging assays; these improvements can be attributed to synergistic interactions between metal dopants and bioactive compounds in plant extract. This study presents a cost-effective, sustainable, and non-toxic route for synthesizing doped TiO₂ nanoparticles with enhanced antioxidant and antibacterial properties for potential applications in biomedical and environmental technologies.