In this study, ZnO nanoparticles were green-synthesized from Acalypha indica leaf extract using zinc acetate as a precursor. The prepared ZnO nanoparticles were calcined at three different temperatures, namely 100, 300, and 600 degrees C. The structure/morphology of the green-synthesized ZnO nanoparticles was ascertained through X-ray diffraction, particle size analysis, scanning electron microscopy, transmission electron microscopy, and surface area analysis techniques. It was observed from the physico-chemical and biological characterization studies that ZnO nanoparticles calcined at high temperature (600 degrees C) exhibit high surface area (230 m(2) g(-1)) and small particle size (20 nm) with good antibacterial activity against Escherichia coli (22.89 +/- 0.06 mm) and Staphylococcus aureus (24.62 +/- 0.08 mm). In addition, cotton fabrics coated with these nanoparticles showed higher UV-protection (87.8 UPF), hydrophobicity (155 degrees), and maximum zone of bacterial inhibition against E. coli and S. aureus (25.13 +/- 0.05 mm and 30.17 +/- 0.03 mm) than those coated with particles calcined at 100 degrees C and 300 degrees C. High temperature calcination has a vital role in the crystallization of the particles towards nanoscale with increased resistivity to UV exposure, washing treatments, and microbial infection in fabrics. Thus, the cost-effective ZnO nanoparticles obtained through green synthesis method proves their potential applications in the field of biomedical, textile, and cosmetic applications. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.