Funct. Mater. 2022; 29 (3): 443-450.

Nanocrystalline Cu₂O powders were synthesized through a facile and swift one pot synthesis in the presence of surfactant polyvinylpyrrolidone (PVP). The PVP solution molarity was varied from 0.4-0.8 mmol before mixing the precursors to investigate its effect on the structure, morphology, and optical properties of Cu₂O nano-crystallites. The XRD analysis confirms the formation of the cubic phase of nanocrystalline Cu₂O by diffraction peaks associated with (110), (111), (200), (220), (311) and (222) crystal planes. The average crystallite size decreases from 23 nm to 14 nm due to an increase in the PVP molarity. In X-ray phase analysis of nanocrystalline powders obtained using solutions of PVP 0.4 mmol and 0.8 mmol, negligible traces of Cu and CuO were found. SEM analysis shows the formation of nanoparticles with decreasing size due to an increase in the PVP molarity. The FTIR spectra show characteristic bands related to molecular vibrations of H-OH stretching, H-OH bending and Cu-O vibration. UV-VIS spectra show an absorption peak around λ = 470 nm for nano-Cu₂O. The absorption peak shows a blue shift from λ = 472 nm to λ = 462 nm with a decrease in the crystallite size due to an increase in PVP concentration. The optical bandgap energy increases from 2.248 eV to 2.519 to 2.772 eV with an increase in the PVP molarity mainly due quantum confinement effects arising from the reduction in crystallite size.