Control of ZnO shape using sonochemical synthetic method and its photocatalytic activity

ZnO nanocrystals were synthesized by a simple sonochemical method from a zinc precursor (zinc chloride, zinc acetate, or zinc nitrate) and hexamethylenetetramine. The length of the ZnO nanorods (NRs) obtained from the zinc acetate precursor could be controlled by altering the solvent ratio (water/methanol), with the length being inversely proportional to the methanol concentration. Although most samples were indexed to hexagonal wurtzite ZnO (JCPDS 36-1451), simonkolleite was obtained from the zinc chloride precursor in 50% methanol. The photocatalytic activities of the ZnO NRs for methylene blue degradation were good, with the NRs from zinc acetate and zinc nitrate obtained in deionized water giving rate constants of 0.0007 and 0.0006 s^-1, respectively. The photocatalytic efficiencies of the samples prepared from the acetate precursor decreased with increasing methanol concentration, and the rate constant was 0.00004 s^-1 for the NRs obtained in 50% methanol solution.