Green Synthesis of Coconut Shell-based Nanobiochar and Its Antibacterial Activity against Pathogenic Bacteria

The development of sustainable nanomaterials from renewable biomass has gained attention in environmental nanotechnology. This is due to their low-cost production, functional surface properties, and potential biological and environmental applications. In the present study, coconut shell, an abundant lignocellulosic agro waste, was utilized as a precursor for the green synthesis of nanobiochar with antibacterial potential against selected pathogenic microorganisms. Coconut shell-derived biochar was produced through controlled pyrolysis, followed by chemical activation, acid purification, mechanical ball milling, ultrasonication, and particle-size fractionation to obtain nanobiochar. The synthesized nanomaterial was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS), X-ray Diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive X-ray analysis (SEM-EDAX). The FTIR analysis confirmed the presence of hydroxyl, carbonyl, aromatic, phenolic, and C–O functional groups, indicating chemically active surface moieties. The DLS analysis showed an average particle size of 308 nm, confirming the nanoscale formation. While the XRD revealed a predominantly amorphous to semi-amorphous carbon structure with limited graphitic ordering, the SEM–EDAX demonstrated rough, irregular, flake-like morphology with mineral-associated elemental composition. The antibacterial activity of nanobiochar was evaluated using agar well diffusion method against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa. A dose-dependent increase in inhibition zones was observed from 25 µL to 100 µL, with the highest activity against Staphylococcus aureus. The findings suggest that coconut shell-derived nanobiochar is a promising green nanomaterial for microbial control, supporting its relevance in environmental, biological, and sustainable nanotechnology applications.