Plant-Derived NiO Nanoparticles with Enhanced UV Absorption and Photocatalytic Efficiency for Sustainable Dye Degradation

Ramalakshmi et al.,

Nanoparticles | Dye

Vol: 11; Iss. 5; May. 25 | ISSN: 2454-5422

The UV–Visible absorption analysis of synthesized nickel oxide (NiO) nanoparticles through Emblicaofficinalis plant extracts confirms their successful formation and notable optical characteristics. A dominant absorption peak at 250.01 nm is attributed to charge transfer transitions between oxygen 2p and nickel 3d orbitals, reflecting the material’s semiconductor nature and high photoactivity. Additional peaks at 296.71 nm and 370.05 nm likely arise from interband transitions or structural defects, such as oxygen vacancies, common in nanostructured systems. The shoulder near 370.05 nm may indicate plasmonic resonance or scattering effects influenced by particle size. Mie theory, which relates light scattering to particle size and refractive index, can be applied to the absorption data for nanoparticle size estimation, suggesting sizes within the 10–100 nm range. Broad absorption from 200 to 400 nm and the absence of peaks beyond 400 nm underscore the wide bandgap and strong UV absorption, making NiO suitable for applications in UV shielding, photocatalysis, and energy devices. Complementary UV–Vis spectra of Bismarck brown dye show a strong peak between 400–500 nm, linked to π→π* transitions in azo and aromatic groups, with minor UV peaks from n→π* transitions. Upon visible light irradiation in the presence of NiO, a steady decline in absorbance over 48 hours indicates effective photocatalytic degradation. The fading of both major and minor peaks suggests full mineralization without stable intermediates. This confirms the efficiency of NiO nanoparticles in breaking down complex dye molecules, reinforcing their potential in treating dye-laden wastewater and advancing sustainable environmental remediation technologies.

Dr. A.Sabaridasan, PG & Research Department of Biotechnology, Sri Vinayaga College of Arts & Science, Ulundurpet, Kallakurichi (Dt), India.