ZnO nanomaterials with different morphologies such as nanoflakes, spherical nanoparticles (SNPs), and nanorods have been synthesized via a simple low temperature coprecipitation method. The concentration of the capping agent is a key factor in the morphological control of ZnO nanostructures. Triton X-100 micelles were found to be single molecules at low concentration but spherical and rod-like shaped micellar aggregation at higher concentrations. The formation of different morphologies of ZnO was confirmed by HR-SEM and HR-TEM. XRD data showed the formation of single-phase ZnO with the wurtzite crystal structure. The influence of Zr contents on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO SNPs was investigated systematically. The influence of the ZnO morphologies on the photocatalytic degradation (PCD) of resorcinol as a model reaction is evaluated and discussed in terms of particle size, surface area, crystal growth habits, and oxygen defects. The results indicated that the particle size is an important factor for the PCD, and thus, the 1.5 wt % Zrdoped ZnO SNPs show superior performance toward PCD of resorcinol than other samples due to the small particle size distribution. Furthermore, the effect of different photocatalytic reaction parameters on the resulting PCD efficiency of ZnO SNPs was investigated.
■ INTRODUCTIONThe shape control of semiconductor nanostructures has attracted considerable attention due to the fact that they play very important roles in determining their physical and chemical properties. 1−4 Nanostrucutured zinc oxide (ZnO) is a versatile and interesting semiconductor material to study because it possesses very attractive physical properties such as a wide direct band gap (3.37 eV), a large exciton binding energy of 60 meV at room temperature, and unique electronic, catalytic, optoelectronic, and photocatalytic properties. 5−9 A wide variety of synthetic routes have thus been proposed to prepare specific nanostructures of ZnO, including nanorods, 10 nanowires, 11 nanobelts, 12 tetrapods, 13 and many other anisotropic prototypes in order to further the development of ZnO nanostructures. Among the many synthetic approaches, wet chemistry is an effective way for the production of ZnO nanostructures. In wet-chemistry processes, capping reagents are often required to control the crystal growth of the materials to enable the formation of nanostructures. Meanwhile, by suitably modulating the reactant concentrations, 14 reaction temperature, solvent, 15 organic additives, 16 and quenching treatments 17 during the reaction, ZnO nanostructures, with controllable dimensions, have been obtained. Most of the above operations, however, involve complicated synthetic procedures, which may hinder the applicability of the products. Therefore, development of a simple, environmentally friendly method to prepare ZnO nanostructures with controllable morphology is crucial to their practical applications and has thus become an important topic of investigation. The precipitat...