Green Synthesis and Characterization of Ag@TiO₂ Core–Shell Nanoparticles with Enhanced Antibacterial Activity

Ag@TiO₂ core-shell nanoparticles (NPs) were synthesized through an environmentally benign, two-step method utilizing Aloe vera extract as a natural reducing and capping agent. Structural and morphological characterization via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) confirmed the successful formation of spherical core-shell structures with a size range of 10-40 nm. Optical analysis revealed a wide bandgap of 4.8 eV, indicative of quantum confinement effects. While electrokinetic measurements suggested moderate colloidal stability (zeta potential near 0 mV), the nanoparticles exhibited potent, strain-dependent antimicrobial activity. Notably, they demonstrated superior efficacy against Gram-positive Staphylococcus epidermidis (32 mm inhibition zone) compared to Gram-negative Escherichia coli (21 mm inhibition zone). This green synthesis route presents a sustainable strategy for producing antibacterial nanoparticles with enhanced activity against Gram-positive pathogens.