Ecofriendly synthesis and characterization of CuO nanoparticles from Blighia sapida pods for antimicrobial applications

Abstract The increasing interest in green nanotechnology has driven research into environmentally sustainable methods for nanoparticles synthesis. In this study, Blighia sapida (ackee) seed pod extract was employed as a bio-reductant and stabilizing agent for the green synthesis of copper oxide (CuO) nanoparticles (NPs). The biosynthesis was indicated by a colour change during reaction and confirmed through multiple characterization techniques including UV–Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The nanoparticles exhibited strong absorbance at 333 nm. FTIR analysis confirmed the presence of functional groups such as O–H, C = O, C–O–C, and Cu–O bonds. XRD and TEM analyses revealed monoclinic CuO nanoparticles with crystallite sizes of 6.21 nm and 3.51 nm, respectively, while DLS revealed a hydrodynamic size of 57.38 nm with a PDI of 0.471, indicating moderate polydispersity. The biosynthesized CuO nanoparticles displayed significant antibacterial activity against both Gram-negative ( Escherichia coli , Pseudomonas aeruginosa , Klebsiella pneumoniae , Proteus penneri ) and Gram-positive ( Staphylococcus aureus , Streptococcus pyogenes ) bacteria. Notably, Gram-negative strains showed greater susceptibility, attributed to their thinner and more permeable cell walls. This study demonstrates the viability of using B. sapida seed pods—an agricultural waste product—for eco-friendly CuO nanoparticles synthesis, highlighting its potential for sustainable antimicrobial applications.