Development of green technology is generating interest of researchers towards eco-friendly and low cost method for bio synthesis of nanoparticles. 0.1 M copper acetate solution and neem extract was made into bulk. 50 mL of copper acetate and 150 mL of neem extract were taken and mixed in a beaker. It was observed that the Azardiachta indica leaf extract can reduce copper ions into copper nano particles within 5 minutes of reaction time and brown coloured precipitate settling down. The biosynthesized nanoparticles of copper oxide are characterized through UV-Vis spectra, FT-IR, AFM and XRD. In UV-Vis spectra a peak was obtained at 346 nm due to inter band transition of core electrons and band gap energy of 2.65 eV was observed through tauc plot. Sharp peak at 480.42 and 538.80 cm^-1 in FT-IR spectrum is due to Cu-O bond. CuO Nano particle is crystalline and identical to simple cubic. The particle sizes of CuO NPs are found in different sizes range of 49 nm, 87 nm, 120 nm and 324 nm.

Keywords: Green synthesis; Copper Oxide Nanoparticles; Azardiachta indica (Neem)