This study presents the synthesis and characterisation of zinc oxide (ZnO), copper oxide (CuO), and titanium dioxide (TiO₂) nanoparticles fabricated through Pulsed Laser Ablation in Liquid (PLAIL). A Q-switched Nd: YAG laser was utilised at wavelengths of 532 nm and 1064 nm for ablating high-purity metallic targets. Different analysis methods, UV–Vis spectroscopy, Tauc plot analysis, Energy-Dispersive X-ray Spectroscopy (EDX), and Transmission Electron Microscopy (TEM) for analysing the generated nanoparticles’ structural and optical features. The results confirmed that the laser wavelength affects the nanoparticle properties directly. The optimally synthesised nanoparticles were obtained at 532 nm, which demonstrated stronger optical absorption, wider band gaps, smaller particle sizes, and well-dispersed quasi-spherical morphologies because of the effect of quantum confinement. While the obtained nanoparticles at 1064 nm were larger size with reduced absorption. The uniform distribution of the produced nanoparticles at 532 nm corresponds to increased band gaps of ZnO (3.45 eV) and CuO (1.90 eV), which was confirmed by TEM imaging. Furthermore, the purification and accuracy of the nanoparticles’ elemental compositions were further verified by EDX analysis. The current findings highlight the PLAIL potential as a clean and without any additional additives method for customising nanostructures that suit the applications of photocatalytic self-cleaning surfaces and other environmentally sustainable applications.