Green Synthesis of Triangular ZnO Nanoparticles Using Azadirachta indica Leaf Extract and Its Shape Dependency for Significant Antimicrobial Activity: Joint Experimental and Theoretical Investigation

The present study reports the green synthesis of triangular ZnO nanoparticles (G-ZnO NPs) using Azadirachta indica leaves extract, and a shape dependent density functional investigation for ZnO NPs on their antimicrobial activity. The X-ray diffraction (XRD) analysis shows the synthesized G-ZnO NPs are well crystalline in nature and calculated grain size is found to be 60–65 nm. The Fourier transforms infrared spectroscopy (FT-IR) represents that the functional group and capping agents are well attached to the nanoparticles, and the bands located near 500.8 cm −1 , 459.07 cm −1 and 418.57 cm −1 represents G-ZnO NPs. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS) confirmed the presence of the synthesized G-ZnO nanoparticles with an average size range 100–200 nm. The synthesized G-ZnO NPs are found to be in the triangular shape. A detail theoretical investigation under density functional framework shows that our synthesized triangular ZnO nanoparticles are better candidate for biological interactions compared to the prototypical spherical counterpart. The synthesized G-ZnO nanoparticles using A. indica leaves extract in triangular shape are found to show significant antimicrobial activity against Escherichia coli and Bacillus subtilis indicating a better alternative to the typical chemical methods. Graphic Abstract