GREEN SYNTHESIS OF COBALT OXIDE (𝑪𝒐𝟑𝑶𝟒 ) NANOPARTICLES BY USING CITRUS SINENSIS PEEL EXTRACT FOR ANTIBACTERIAL TREATMENT

Abstract In this study, cobalt oxide nanoparticles were synthesized through green method using 0.25𝑀 cobalt nitrate hexahydrate as a precursor salt and peel waste extract of citrus sinensis as a reducing and capping agent. The synthesis process of 𝐶𝑜3𝑂4 NPs were performed with in three various volume ratios of the precursor salt and the extract of the peel waste citrus sinensis as 1 ∶ 2 ( 33.3𝑚𝑙 solution of 0.25M cobalt nitrate hexahydrate ∶ 66.7𝑚𝑙 of 30g peel extract), 1 ∶ 1 ( 50𝑚𝑙 solution of 0.25M cobalt nitrate hexahydrate ∶ 50𝑚𝑙 of 30g peel extract), and 2 ∶ 1 ( 66.7𝑚𝑙 solution of 0.25M cobalt nitrate hex hydrate ∶ 33.3𝑚𝑙 of 30g peel extract).The synthesized 𝐶𝑜3𝑂4 NPs were characterized using X-Ray diffraction, scanning electron microscope, Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. The average crystal size and purity of the green formed 𝐶𝑜3𝑂4 NPs were found to be 22.14 𝑛𝑚,11.19 𝑛𝑚, and 14.58 𝑛𝑚, respectively for the 2 ∶ 1 , 1 ∶ 1 and 1 ∶ 2, respectively. The band gap energy was 3.77𝑒𝑉,3.70𝑒𝑉 and 3.55𝑒𝑉 for the 1 ∶ 1,1 ∶ 2, and 2 ∶ 1, respectively. The Fourier transform infrared spectroscopy study proves the presence of different functional groups and bioactive capping and reducing. The antibacterial efficiency of synthesized 𝐶𝑜3𝑂4 NPs was tested for antibacterial test Staphylococci Aureus and Escherichia coli using 50𝜇𝑔/𝑚𝑙,75𝜇𝑔/𝑚𝑙, and 100𝜇𝑔/𝑚𝑙 concentration. 𝐶𝑜3𝑂4 (2 ∶ 1) shows zone of inhibition of 8, 9,10 and 9, 10 and 11 𝑚𝑚 for Escherichia coli and Staphylococci Aureus, respectively. 𝐼𝑓 𝐶𝑜3𝑂4 (1: 1) shows zone of inhibition of 7, 13, 15 and 7, 14 and 17𝑚𝑚 against Escherichia coli and Staphylococci Aureus. Finally, 𝐶𝑜3𝑂4 ( 1 ∶ 2 ) with the same concentration showed zone of inhibition of 9, 11, 12 and 9, 11, 13𝑚𝑚 against Escherichia coli and Staphylococci Aureus, respectively