Laser spectroscopic study of acetate-capped colloidal ZnO nanoparticles

We report here the micro-Raman and photoluminescence studies of acetate-capped colloidal ZnO nanoparticles synthesized by a low-cost hydrothermal synthesis method. The ZnO nanoparticles synthesized by this method exhibited a uniform particle size distribution, averaging from 3 to 5 nm in diameter. The visible Raman spectroscopy data show the presence of the wurtzite E2 phonon mode around 438 cm-1 and UV Raman spectra show longitudinal optical (LO) phonon modes up to the third order. Apart from the strong band-edge UV emission at around 3.28 eV in the photoluminescence spectra, a broad defect-induced emission at around 2.05 eV was also observed. However, the defectinduced emission was much weaker than the band-edge emission, suggesting that surface states of ZnO had been reduced by the adsorption of acetate molecules. Development of this synthesis method would not only be useful for improved device performance, but also for cost-saving measures in the optoelectronics industry.