Synthesis of CuO hollow nanoparticles using laser ablation: effect of fluence and solvents

Nanosecond laser pulses (1064 nm, 8 ns and 10 Hz) were employed to ablate a Cu target immersed in deionized water (DI) and ethylene glycol (EG). The ablation process was carried out for 60 min for two different laser fluences, i.e., 27J/cm2 and 80J/cm(2), which resulted in the formation of Cu/CuO nanoparticles (NPs) in both the media. The effects of laser fluence and solvents on the morphology of NPs were investigated using structural and optical characterization techniques (such as TEM, HRTEM, XRD, UV-visible and PL spectroscopy). The colloidal solution synthesized at the low fluence of 27J/cm2 in DI illustrated the presence of hollow structured CuO NPs and has been attributed to the Kirkendall effect. At the high fluence of 80J/cm2, porous NPs were seen which has been attributed to the dissolution of H2 molecules. In EG, no signature of hollow or porous NPs was seen and this has been accredited to its oxygen deficiency and viscous nature. Additionally, the growth kinematics involved in the transformation of morphology are elaborately discussed.