Effect of annealing temperature on antibacterial, antifungal and structural properties of bio-synthesized Co3O4 nanoparticles using Hibiscus Rosa-sinensis

Abstract

This work states a new holistic approach for a biological synthesis of Co3O4 NPs employing aquatic flower extract of Hibiscus Rosa-sinensis. The red color petal extract was used as the green reduction catalyst and stabilizing agent for synthesizing cobalt oxide NPs from Cobalt (II) chloride hexahydrate (CoCl2. 6H2O), and it was calcined at a different annealing temperature, such as room temperature, 600 °C, 700 °C and 800 °C for 2 h. The synthesized Co3O4 NPs were characterized using XRD, FESEM, EDX, PL, FTIR and UV-visible techniques. XRD spectrum exhibited the samples having the shape of a cubical spinel structure with average grain size of 61.32, 57.302, 50.57 and 40.05 nm. Different surface structures and morphologies for Co3O4 NPs obtained at different annealing temperatures were confirmed by FESEM images. Furthermore, the biosynthesized NPs displayed proficient antibacterial activity against gram positive and gram negative bacteria like Staphylococcus aureus, Streptococcus mutans, Klebsilla pneumonia, E. coli and antifungal activity against Aspergillus flavus, Aspergillus niger. It was shown that the biosynthesized Co3O4 NPs exhibited the antibacterial activity against all analyzed bacterial strains with efficient antifungal potential which was reported in this study. These results witness that the Hibiscus flower extract was an efficient response medium to formulate Co3O4 NPs related to bio-medical products due to low toxic chemicals used in metal oxide NPs fabrication.