Biosynthesis of Zinc Oxide Nanoparticles from Scent Leaf (Ocimum gratissimum) and Evaluation of its Antioxidant and Photocatalytic Activities

Abstract

Green synthesis of nanoparticles for several applications has gained attention in the field of science because of its cost-effectiveness and eco-friendliness. In this work, we synthesized zinc oxide nanoparticles (ZnO NPs) from scent leaf, characterized the synthesized nanoparticles and established its antioxidant and photocatalytic activities. The biosynthesized O. gratissimum zinc oxide nanoparticles (OgZnO NPs) were analyzed. Thermal gravimetric analysis transition shows a loss of 12.65% up to 650°C, indicating that the OgZnO NPs is thermally stable after 650°C. The patterns indicated crystalline orthogonal shape with a particle size of 15.5 nm. The Fourier transform infra-red spectroscopy of the synthesized OgZnO NPs revealed different bands. The peak in the region of 650 cm⁻¹ is assigned to Zn-O stretching vibration confirming formation of ZnO NPs. scanning electron microscope coupled with energy dispersive x-ray images and spectra revealed triangular crystalline shapes and presence of carbon and oxygen respectively. The percentage elemental compositions of the synthesized nanoparticles were 17.86%, 21.75%, 58.28%, 0.62% and 0.48% for carbon, oxygen, zinc, silver and nitrogen respectively. Strong absorption bands of the biosynthesized samples observed from UV-visible spectra at 350–400nm was characteristic band of ZnO nanoparticles. Free radical scavenging activity of the synthesized OgZnO NPs revealed that it possesses high antioxidant property in a concentration dependent manner. The photocatalytic activity of OgZnO NPs had absorbance degradation at 600 nm for methylene blue dye discoloration after 1 h, with a degradation maximum of 85%. In conclusion, the synthesized OgZnO NPs could be used in several pharmaceutical and biotechnological applications.