Tuning the Optical, Structural, and Photocatalytic Properties of Copper Oxide Nanoparticles Synthesized via Pulsed Laser Ablation in Liquid for Environmental and Optoelectronic Applications

Copper oxide nanoparticles were synthesized by pulsed laser ablation in deionized water at different laser pulse energies. The optical response was examined for samples prepared at 600, 800, 1000, and 1200 mJ, while selected samples were further evaluated for structural, photocatalytic, and photodetector performance. XRD analysis confirmed the formation of monoclinic CuO, with an average crystallite size of approximately 47.31 nm for the 1200 mJ sample. TEM observation showed nearly spherical primary nanoparticles with an average size of about 16 nm, whereas FESEM analysis of CuO deposited on porous silicon showed larger surface features of about 40 nm, indicating that the measured size depends on the characterization method and sample form. UV-Vis analysis showed an increase in absorption intensity with laser energy, and the apparent optical bandgap estimated from Tauc plots decreased from 3.55 ± 0.03 eV to 3.16 ± 0.03 eV as the laser energy increased from 600 to 1200 mJ. Photoluminescence analysis of the 1200 mJ sample showed emission components near 428, 486, and 590 nm, suggesting contributions from near-band-edge, radiative recombination, and defect-related transitions. For photocatalysis, CuO nanoparticles prepared at 600, 1000, and 1200 mJ degraded methylene blue by 89.9%, 91.2%, and 92.3%, respectively, after 120 min under UV irradiation. The CuO/porous-Si photodetector showed increased photocurrent and responsivity compared with bare porous silicon, with the 1200 mJ sample giving a responsivity of 0.136 A W -1 at 450 nm under the reported measurement conditions. These results indicate that laser pulse energy influences the structural and optical properties of PLAL-synthesized CuO nanoparticles and their potential use in photocatalytic and photodetection applications.