Control of ZnO morphologies via surfactants assisted route in the subcritical water

ZnO micromaterials were fabricated from the decomposition of soluble [Zn(OH)4]2− precursor in subcritical water at 280 °C and 7.5 MPa in the presence of cetyltrimethylammonium bromide (CTAB), EO17-PO60-EO17 (P103), and their mixture, respectively. The morphology and structure of the resultant materials were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electronic diffraction (SAED), energy dispersive X-ray analysis (EDXA), and high-resolution electron microscopy (HRTEM). The results demonstrated that ZnO microflowers with an average size of about 1.7 μm were fabricated as the CTAB/P103 mixture was used as the structure-directing agents, while nanorods and microrods were synthesized in the presence of CTAB and P103 under similar conditions, respectively. Based on our serials of experimental results, surfactant-assisted growth mechanisms are responsible for the shape evolution of ZnO morphologies. The photoluminescence (PL) spectra of the samples were determined, and the catalytic activity of the ZnO flowers and rods for Friedel-Crafts acylation of anisole and benzoyl chloride were tested. The results showed that ZnO flowers had more intense emission and higher catalytic activity for Friedel-Crafts acylation than the rods.