Abstract
The present study highlights a simple and eco-friendly route for the synthesis of pure and nickel doped (1%-3%) tin oxide (SnO2) nanocrystals (NCs) with the use of Azadirachta indica (Neem) leaf extract. The synthesized pure and Ni-doped (1%-3%) SnO2 NCs were characterized thoroughly for their optical, structural, functional, and morphological characteristics. The results of the study revealed that the Ni2+-doped SnO2 NCs are maintaining the tetragonal crystalline phase and the Ni doping (1%-3%) caused a shift in the bandgap energy to 3.87 eV as against the pure SnO2 of 3.61 eV. Also, the photoluminescence (PL) spectrum revealed for the intrinsic defects encountered in the visible emission peaks in the range of 400-560 nm. Further, the biological activity with the help of antibacterial efficacy and in vitro toxicity was tested and the results of antibacterial studies revealed that higher concentrations of Ni doping have enhanced efficacy towards both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterias. The in vitro cytotoxicity studies on Vero (non-cancer) and HEp-2 cells (cancer) exhibited greater cytotoxicity toward Vero than HEp-2 cells at its half-maximal inhibitory concentration (IC50) associated with the cell rounding and detachment. Thus, the doping of Ni2+ metal ions in SnO2 tends to improve the photocatalytic activity, in addition to finding the extended applications in the biomedical field for the delivery of antimicrobial agents or drug molecules.