Green biogenic synthesis of Ag-loaded TiO2/rGO nanocomposite and its prospective applications in antibacterial and self-cleaning surface coating

Mangosteen peel (Garcinia mangostana L.) contains secondary metabolites such as α-mangostin, which can act as natural bioreductors. In this study, mangosteen peel extract was utilized in the green synthesis of reduced graphene oxide (rGO) and titanium dioxide (TiO₂) nanoparticles. Subsequently, Ag-loaded TiO₂/rGO (Ag@TiO₂/rGO) nanocomposite was synthesized via the hydrothermal method. The nanocomposite was characterized using FTIR, XRD, GSA, DRS UV–Vis, SEM-EDX, and TEM analyses. FTIR spectra confirmed the formation of Ag–TiO₂ bonds with an absorption shift from 631 to 602.81 cm⁻¹, while XRD revealed TiO₂ in the anatase phase with an average crystal size of 18.155 nm. GSA analysis indicated a mesoporous structure (type IV) with a surface area of 88.277 m² g⁻¹. SEM and TEM images showed Ag successfully coated the TiO₂/rGO. The modification with rGO and Ag doping reduced the band gap of TiO₂ from 3.12 eV to 3.03 eV, leading to improved light absorption in the visible region. The photocatalytic test demonstrated excellent self-cleaning properties, achieving 99.76 % methylene blue degradation under visible light within 20 min. Antibacterial activity tests revealed inhibition zones of 15.33 mm for Escherichia coli (6 h irradiation) and 8.33 mm for Staphylococcus aureus (4 h irradiation), indicating strong and moderate activity, respectively. These findings highlight the potential of Ag@TiO₂/rGO nanocomposites as efficient self-cleaning and antibacterial agents.