Zinc oxide nanoparticles were for the first time produced by laser ablation of a solid zinc target in 35% liquid hydrogen peroxide. As-produced nanoparticle-based films on Si substrates were visualized by scanning electron microscopy (SEM) and energy-dispersion x-ray micro-spectroscopy (EDX) as amorphous, containing highly defective mixed oxide/hydroxide structures and crystallization-water molecules. Specific structural defects, damping the photoluminescence band of the nanoparticles peaked near 550 nm for the 488 nm pump laser wavelength, were annealed in air at temperatures 200-400 °C over 1-2 hours, with the accompanying strong photoluminescence yield and the appearance of the absorption cut-off near 350 nm. However, the following annealing at higher temperatures up to 1200 °C for time periods variable in the range of 1-3 hours, resulted in the damping of the photoluminescence. According to x-ray diffraction (XRD) characterization of the nanoparticle-based films on fluorite substrates, high-temperature annealing at 800 C for 1 hour induce crystallization of the common hexagonal ZnO phase (wurzite structure) via loss of peroxide bridges, crystallization water molecules and other structural defects. Meanwhile, annealing at 1200 °C yields in another distinct crystalline phase of ZnO, which appears to be a sphalerite.