The effect of shape and size of ZnO nanoparticles on their antimicrobial and photocatalytic activities: a green approach

In this paper, ZnO nanoparticles (NPs) having potent photocatalytic and antimicrobial activities have been synthesized by using the aloe vera plant extract. The ZnO NPs have been synthesized using $$(\hbox {Zn}(\hbox {CH}_3\hbox {COO})₂{\cdot } 2\hbox {H}₂\hbox {O})$$ (5, 10 and $$50\,\hbox {mmol}\, \hbox {kg}^-1$$ ), at temperature $$70{^\circ }\hbox {C}$$ and pH 11.5. The synthesized NPs were examined using UV–Visible, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM) characterization techniques. TEM analysis confirms the synthesis of ZnO NPs with hexagonal, spherical, cylindrical and cuboidal shapes decorated under different concentrations of precursor metal salt. UV–Visible studies revealed that ZnO NPs have a wide energy band gap varying from 3.36 to 3.43 eV. The synthesized ZnO NPs were examined for the photocatalytic degradation of methyl orange dye which resulted in up to 95% degradation. ZnO NPs are also inspected for the antibacterial activity against Bacillus subtilis (MTCC 441), Staphylococcus aureus (MTCC 737) and Escherichia coli (MTCC 739) pathogenic bacteria.