Abstract

• The synthesis of the cubic-like CuO nanoparticles was achieved by a green method using starch as the capping agent. Starch was extracted from avocado seed, and pH and moisture content of the extracted starch were determined. The extracted starch was then used to prepare CuO- starch composites by using a facile process. The aqueous solutions of 10, 20, and 30 % (w/v) CuCl2 were used not only as a precursor solution for the formation of CuO- starch composites but also as a solvent. The method involves first dissolving the starch in the three different concentrations of CuCl2 aqueous solutions, then adding NaOH to achieve a final pH value of 8.4. When the prepared composites were calcined at 500 °C for 4 h, CuO nanoparticles (CuO NP1, CuO NP2, and CuO NP3) were obtained. The prepared CuO nanoparticles were characterized by different techniques, including XRD, SEM, and FT IR. The average crystallite sizes of CuO nanoparticles were in the range of 33-42 nm. FT IR spectra exhibited only the Cu-O stretching vibrational mode. The CuO nanoparticles were used to investigate the optical property by UV-vis spectrophotometry. According to the UV-Vis spectra of the prepared CuO nanoparticles, the optical band gaps were found to be 3.8 eV for CuO NP1, 3.4 eV for CuO NP2, and 3.3 eV for CuO NP3.