Controlled synthesis of ZnO nanostructures with different morphologies in microemulsions

ZnO nanostructures with different morphologies were prepared in microemulsions with ZnSO4 and ammonia as raw materials. The effects of microemulsion types, concentration of reactants, W values, co-surfactants, surfactants, oil phases and calcination temperatures were systematically studied. The products were characterized by X-ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC-TG), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and photoluminescence (PL) spectrum. Results show that ZnO nanoparticles were obtained in water-in-oil microemulsions while ZnO nanorods are gained in bicontinuous microemulsions. Water-in-oil microemulsions and long carbon chains of surfactants can prevent the preferential growth of ZnO. The particle size of the products increased with the increase of W values, calcination temperatures and the concentration of reactants but decreased with the increase of the carbon chain length of surfactants, co-surfactants and oil phases. PL spectrums show that the UV emission peak weakened and visible emission peak increased with the decrease of particle size. Meanwhile, the PL spectrums have a little red-shifted.