Comparative Study of Green and Sol-Gel Synthesis of CaO NPs and Evaluation of Their Antibacterial Activities

Abstract

Synthesis of metal oxide nanoparticles by utilizing traditional medicinal plant extract is the promising alternative to the convectional chemical methods. This work aimed to synthesize calcium oxide nanoparticles through green approach using indigenous Moringa stenopetala leaf extracts as compared to sol-gel synthetic methods. The basic properties of green synthesized CaO NPs using Moringa stenopetala leaf extract and sol-gel method of CaO NPs has been studied by XRD, UV- Vis, PL, TGA, FTIR, and SEM. The XRD spectra showed that the synthesized CaO NPs via green approach were more crystalline and contained good purity as compared XRD patterns that obtained from the sol-gel synthesized CaO NPs. The average crystallite of CaO NPs obtained from XRD spectra using green synthesis method was found to be 13.59 nm. UV-Vis absorption spectra showed that the energy band gap of green synthesized and CaO NPs sol-gel which was found to 3.85 eV, and 3.78 eV respectively. The green synthesized CaO NPs lead to wide energy band gap as compared to sol-gel method synthesis due to the confirmation of small sized CaO NPs. Photoluminescence spectra analysis, the emission peak around 418.64 nm revealed that the green synthesized calcium oxide nanoparticles which are attributed to the radiative recombination of excitons. FT-IR analysis indicated that the presence of the functional group attached to the green synthesized of CaO NPs and sol-gel synthesis. The TGA analysis showed that the evaporation of water contents from the nanoparticles were at 400 and decomposition temperature of the dried gel occurred between 550 750 where the CaO NPs was synthesized. The total percentage weight loss of sample from 100 oC to 750 oC accounts for 16.471%. SEM analysis showed surface nature of green synthesized CaO NPs appeared as spherical shape and the average particles size found to be 24.15 nm. Similarly, the average size and shapes of particles observed using the sol-gel synthesized were recorded 90-110 nm and cubic phase nature respectively. The synthesized of CaO NPs via the green synthesis methods were applied on the gram positive bacteria (S. aureus, S. pyogenes) and gram negative bacteria (E. coli, P. aeruginosa) of 50mg/mL concentration, showed the inhibition zones (15.67 0.69 mm, 17.3 3.055 mm) and (20.75 1.56 mm, 19.6 2.460 mm) respectively.