Structural, Phonon Vibrational, and Catalytic Properties of High-Energy Ground ZnO Nanoparticles

This work has used thermal decomposition and high-energy grinding to fabricate ZnO nanoparticles. The grinding time (t_m) for up to 120 min reduced the average crystallite size (d) from 97 nm of the initial material to ~ 28 nm. Apart from Zn and O, no impurity related to the grinding was found in the fabricated nanoparticles. X-ray diffraction and Raman scattering data showed a single phase of the fabricated samples, crystallizing in the wurtzite hexagonal structure. With decreasing d, the lattice parameters gradually increased while more Zn- and O-related defects and structural distortions were created in the ZnO host lattice, which enhanced the lattice strain. These phenomena rapidly reduced excitonic emissions, enhanced the relative intensity of visible photoluminescence, widened asymmetrically and red-shifted the Raman modes, and stimulated vibration modes at wavenumbers of 500~620 cm⁻¹. Using the spatial correlation model, the spatial correlation length characteristic for structural disorders decreased as d reduced. In particular, the study of the photocatalytic degradation of rhodamine-B under UV-light proved that lattice defects generated by the grinding reduced the degradation efficiency.