Facile Synthesis of Monodisperse Porous ZnO Spheres by a Soluble Starch-Assisted Method and Their Photocatalytic Activity

In this study, monodisperse porous ZnO spheres were fabricated by a facile and low-cost soluble-starch-assisted method. The as-obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV−vis diffuse reflectance spectroscopy (DRS), thermogravimetric and differential scanning calorimetry (TG−DSC), Fourier transform infrared (FTIR) spectroscopy, and Brunauer−Emmett−Teller (BET) analysis. The Raman spectra revealed that the uncalcined powders were composed of ZnO and starch. The BET analysis showed that mesopores (25 nm) and macropores (180 nm) coexisted in the typical porous ZnO spheres. The photocatalytic activities of the as-obtained ZnO samples were evaluated in the photocatalytic degradations of aqueous solutions of rhodamine B (RhB) and 4-nitrophenol (4-NP) at room temperature. A possible growth mechanism of the as-obtained porous ZnO spheres is also discussed.