Extraction of graphene nanostructures from Colocasia esculenta and Nelumbo nucifera leaves and surface functionalization with tin oxide: Evaluation of their antibacterial properties.

Expeditious evolution of antimicrobial resistance in recent years has been identified as a growing concern by various health organizations around the world. Herein, we report a facile and environmentally benign production of highly antibacterial carbonaceous nanomaterials from Colocasia esculenta and Nelumbo nucifera leaves for the first time. After carbonization and oxidative treatment, smaller graphene domains are formed in Colocasia esculenta derivatives whereas larger sheet-like structures are spotted in the case of Nelumbo nucifera . Smaller particle size makes quantum confinement effects more prominent as evident in fine tuning of photoluminescence emission after each stage of treatment. We also demonstrate the influence of precursor materials in dictating the antibacterial properties of nano-systems. When microbicidal activity was tested against model bacteria Pseudomonas aeruginosa , nanocomposite derived from Colocasia esculenta leaves displayed higher activity than the antibiotic drug Clarithromycin (control) with a measured zone of inhibition of 40 ± 0.5 mm. This is one of the highest values reported in comparison with other plant-based carbon-silver nano-systems. From quantitative analysis, it is discerned that nanocomposite obtained from Colocasia esculenta leaves has antimicrobial efficacy equivalent to commercial antibiotic drugs and is able to eradicate bacteria at much lower concentrations when compared to those from Nelumbo nucifera leaves.