Phytogenic NiO Nanoparticles Derived from Syzygium cumini Seeds for Efficient Photocatalytic Dye Degradation and Antimicrobial Applications

Although integrated optimization and multifunctional validation are still lacking, green production of metal oxide nanoparticles presents a viable substitute for traditional techniques. This work describes an environmentally friendly production of NiO nanoparticles utilizing seed extract from Syzygium cumini, which was followed by a thorough physicochemical, photocatalytic, and biological assessment. In order to achieve stable nanostructures, key parameters such as precursor concentration, extract volume, pH, temperature, and reaction time were tuned during the preparation of the nanoparticles using a phytochemical-mediated reduction method. Nanoparticle production was validated by UV-Vis spectroscopy, which showed a distinctive absorption peak at 330 nm. A crystalline cubic NiO phase was discovered by XRD analysis, and well-dispersed spherical particles with an average size of 15–25 nm were observed by HRTEM. TGA showed excellent thermal stability, VSM verified weak ferromagnetic behavior, and FTIR revealed phytochemical-mediated capping. According to pseudo-first-order kinetics, photocatalytic tests employing methylene blue demonstrated 78% degradation under natural sunshine and 91% degradation under UV irradiation in 90 minutes, with preserved activity throughout five reuse cycles. In terms of biology, the NiO NPs demonstrated concentration-dependent antibacterial activity at MIC levels of ≥70% growth inhibition, up to 78% antibiofilm inhibition, and inhibition zones as large as 27 mm for E. Coli and 23 mm for S. aureus. They also shown significant antioxidant activity. Overall, the multifunctional performance of S. cumini-mediated NiO nanoparticles shows promise for antibacterial surface applications and sustainable wastewater remediation.