Preparation and Luminescent Properties of ZnO Microrods and Microtubes

Hexagonal ZnO microrods and sub-microrods have been prepared through thermal decomposition of an equimolar (0.1 M) aqueous solution of Zn(NO₃)₂.4H₂O and (CH₂)₆N₄ at 90°C for different times (10-46 h). The microrods were transformed into hollow hexagonal ZnO microtubes when the growth time reached 46 h. The Raman spectra and the photoluminescent (PL) spectra were measured. The PL spectra of microrods consist of two strong narrow near-UV bands at 380 nm and 400 nm assigned to free exciton emission and exciton--exciton collision, respectively. The PL spectrum of ZnO microtubes show only one peak in the near-UV region with peak located at 380 nm with FWHM of about 20 nm assigned to free exciton emission. When the growth time increased, the peak intensity of near-UV band decreased.