Synergistic Effect of Ag and Al Co-Doping on Structure, Surface Chemistry, and Photocatalytic Performance of Green-Synthesized Titania Nanoparticles

Biologically mediated green synthesis of nanoparticles (NPs) offers a low-cost, energy-efficient, and environmentally friendly alternative to conventional physical and chemical methods. In this study, pure and Ag-Al co-doped TiO 2 NPs were synthesized by using the stem extract of Saccharum spontaneum as a reducing agent, where the concentration of Al was fixed to 1 mol%, and the Ag content was varied (1, 2, and 3 mol%). All synthesized NPs were characterized through XRD, FTIR, SEM, EDS, UV-Vis spectroscopy, DLS, and zeta potential analysis. The synergistic effect of Ag and Al doping on the photocatalytic effect was also observed. XRD analysis confirmed the formation of anatase TiO 2 of tetragonal structure. The absence of impurity phases denoted the effective integration of dopant ions into the TiO 2 matrix. Existence of Ti−O, Ti−O−Ti, and O−H bonds confirmed the presence of the TiO 2 framework with absorbed water on the NPs surface. Due to the masking of Ag−O and Al−O by strong Ti−O and O−H bonds, there were no dopant-related peaks. Mostly agglomerated spherical-shaped particles with an average particle size ranging from 24.28 nm to 42.97 nm were obtained from SEM analysis. EDS analysis confirmed the presence of all elements in pure and co-doped TiO 2 samples. Red shifting phenomena and band gap decrement from 3.21 eV to 2.96 eV with an increase in dopant concentration were observed through UV-Vis analysis. DLS analysis showed increased TiO 2 NPs' hydrodynamic size and polydispersity after co-doping, resulting in lower colloidal stability and enhanced aqueous aggregation. Zeta potential analysis revealed that the surface charge was reduced after co-doping, resulting in decreased electrostatic stability and promoting particle aggregation. According to photocatalytic studies, optimized Ag and Al co-doping significantly enhanced the efficiency due to synergistic dopant effects, enhanced light absorption, and suppressed charge recombination. On the other hand, excessive dopant loading resulted in aggregation and decreased photocatalytic performance. The developed green synthesis method and improved photocatalytic activity highlight the potential of Ag-Al co-doped TiO 2 NPs as a sustainable material for environmental process engineering and photocatalytic wastewater remediation.