Biofunctionalized Ag-TiO₂-NiO-CeO₂-g-C₃N₄/carbon dot nanocomposite: A green multifunctional platform for accelerated photocatalytic wastewater remediation and antibacterial activity

A new green and sustainable Ag-TiO₂-NiO-CeO₂-g-C₃N₄/carbon dot (CD) multifunctional nanocomposite was successfully fabricated based on a renewable carbon source and surface-functionalizing agent derived from Aloe vera. The presence of bio-derived CDs enhanced the visible-light absorption ability, the charge transfer process at interfaces, and the surface reactivity in the multicomponent heterojunction. The structural and morphological characterizations verify the success in forming the nanocomposite and revealing intimate interfacial interactions among Ag, TiO 2 , NiO, CeO 2 , g-C₃N₄, and CDs that conduce to higher visible-light collection and a decrease in the band-gap energy. Photocatalytic properties for degradation of methyl orange (MO) under visible light demonstrate that the best sample resulted in an MO degradation efficiency of 98.2% with a rate constant of 3.243 × 10⁻¹ min⁻¹ min under pseudo-first-order kinetics, which is due to efficient charge separation, the suppression of electron-hole recombination, and the generation of hydroxyl and superoxide radicals. Furthermore, an excellent concentration-dependent antibacterial capability against Escherichia coli and Staphylococcus aureus is achieved, showing inhibition zones ranging from 8 to 9 mm to 13–14 mm at the range from 400 g mL to 1000 g mL. This improved antibacterial activity may stem from synergistic action by released Ag ions, reactive oxygen species, and facile charge separation in the heterostructure. Hence, Ag-TiO₂-NiO-CeO₂-g-C₃N₄/carbon dot (CD) nanocomposite integrating Aloe vera-derived CDs acts as a potential eco-friendly multifunctional photo catalyst in visible-light wastewater treatment and antibacterial.