Biosynthesized zinc oxide nanoparticles using seed and bark extract of Azadirachta indica for antibacterial, photocatalytic and supercapacitor applications

•The paper demonstrates the biosynthesis of block-/bar-shaped ZnO nanoparticles (NPs -S3/B3) using aqueous extract of seeds/barks of Azadirachta indica, respectively.•Biosynthesized ZnO NPs (S3) have shown promising antibacterial activity against Escherichia Coli, Pseudomonas aeruginosa, Streptococcus pneumonia and Staphylococcus aureus.•Photocatalytic activity of ZnO NPs (B3) has been investigated and observed 84.62% of degradation of methyl orange dye within 180 min under UV–Visible light.•This article also includes the comparative electrochemical study of ZnO NPs (S3 and B3) for supercapacitor applications.