Zinc oxide (ZnO) has a wide direct band gap of 3.37 eV at room temperature and a large excitonic binding energy of 60
meV. In this work, ZnO nanoparticles had been successfully fabricated at low temperature (60 °C). The structures,
morphologies and optical properties of ZnO nanoparticles were investigated by X-ray diffraction (XRD), a scanning
electron microscope (SEM), UV-Visible absorption and photoluminescence (PL) spectra, respectively. Measurement
results of XRD showed that the as-prepared ZnO nanoparticles are a random orientation. The nanoparticles are
approximately particle shape with an average size of about 50 nm by SEM observation, UV-Vis absorption spectrum
indicated that the as-prepared ZnO nanoparticles dispersed in chloroform are highly transparent in the visible region and
have a strong absorption band in the UV region, at the same time, we found a sharp absorption edge at near 370 nm. In
addition, in the as-prepared ZnO nanoparticles/chloroform solution, both a near band edge (NBE) ultraviolet
photoluminescence peak at 372 nm and a defect related deep level emission (DLE) green peak at 513 nm were observed.
It suggested that the NBE photoluminescence peak should be attributed to free excitons transition, the DLE green peak
should be ascribed to intrinsic defects of the single ionized oxygen vacancy (Vo
*) through our research results.
Furthermore, we obtained R (R=INBE/IDLE) value as 0.91. This indicates that there are a large amount of single ionized
oxygen vacancies in as-prepared ZnO nanoparticles, which results in poor crystalline quality of ZnO nanoparticles.