Biogenic nickel oxide nanoparticles derived from Herdmania pallida : Characterization and investigation of antioxidant, antibacterial, antidiabetic, and dye degradation properties

Nickel oxide (NiO) nanoparticles were biosynthesized using a crude extract of the marine tunicate Herdmania pallida by an eco-friendly and cost-effective method. The synthesized nanoparticles were characterized by UV–visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), Zeta Potential (ZP) and cyclic voltammetry (CV). UV–visible spectroscopy showed an absorption peak at 272 nm and an estimated optical band gap of 3.65 eV. X-ray diffraction (XRD) analysis confirmed face-centered cubic NiO with an average crystallite size of 5.68 nm. Fourier transform infrared spectroscopy (FTIR) spectra indicated the presence of bioactive functional groups from the extract, suggesting their involvement in nanoparticle reduction and stabilization. SEM, EDX, DLS and ZP measurements verified the nanoscale morphology, elemental composition, and particle size distribution, respectively. The biosynthesized NiO nanoparticles exhibited multifunctional properties. Photocatalytic experiments under solar irradiation achieved 69.55% degradation of methylene blue within 80 min. Kinetic analysis using pseudo-zero-order, pseudo-first-order, and pseudo-second-order models revealed that the degradation process best followed a pseudo-first-order kinetic model, consistent with previous reports on NiO-based photocatalysts. The nanoparticles also showed notable antioxidant activity in DPPH and hydrogen peroxide scavenging assays, significant antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, and moderate α-amylase inhibitory activity indicative of potential antidiabetic effects. These results suggest that Herdmania pallida-mediated NiO nanoparticles are promising candidates for environmental remediation and biomedical applications, and demonstrate the viability of a sustainable biosynthetic route to functional nanomaterials.