Green synthesis of Bi2O3, MnO2 and their nanocomposite (Bi2O3/MnO2) for efficient photodegradation and antimicrobial activity

An eco-friendly green synthesis approach was used to synthesize Bi2O3, MnO2, and Bi2O3/MnO2 nanocomposite in order to comprehend the effect of nanocomposite on the photocatalytic and antibacterial activity. The structural parameters of as prepared samples were confirmed using X-ray diffraction analysis (XRD). Scherrer formula was applied to find out crystallite size, which ranged from 8 nm to 13 nm. XRD confirmed the geometrical structure of Bi2O3, MnO2 and Bi2O3/MnO2 nanocomposite showing monoclinic structure. The FTIR peaks also confirm the successful synthesis of Bi2O3/MnO2 nanocomposite. SEM of Bi2O3/MnO2 nanocomposite revealed that nanoparticles of Bi2O3 are developed on MnO2 granules. In UV–Vis spectroscopy, absorption maxima showed in the range of 200 nm to 400 nm and band gap ranging from 2.4 eV to 3.4 eV. The antibacterial activity of Bi2O3, MnO2, and Bi2O3/MnO2 nanocomposite was investigated against two gram negative-bacteria (Pseudomonas and Escherichia coli) at 10 mg and 20 mg concentration using disk diffusion method. The zone of inhibitions against Escherichia coli at 10 mg and 20mgl were 22 mm and 26 mm while against Pseudomonas were 28 mm and 33 mm for Bi2O3/MnO2 nanocomposite. Bi2O3/MnO2 composite shows better result as compared to Bi2O3 and MnO2. Photocatalytic activity was carried out using Bi2O3, MnO2, and Bi2O3/MnO2 as photocatalyst for the removal of malachite green (MG) and methylene blue (MB). For Malachite Green (MG), the maximum degradation efficiency of Bi2O3, MnO2, and Bi2O3/MnO2 nanocomposite was 96%, 97% and 98% respectively. For methylene blue (MB), the maximum degradation efficiency of Bi2O3, MnO2, and Bi2O3/MnO2 nanocomposite was 95%, 97% and 98% respectively. This work concludes that Bi2O3/MnO2 nanocomposite enhances the degradation efficiency and antibacterial potential.