Controlled synthesis of double-shelled CeO2 hollow spheres and enzyme-free electrochemical bio-sensing properties for uric acid

A simple solvothermal method has been used to synthesize novel double-shelled CeO2 hollow spheres (HSs) in a mixed solvent of PEG-400 and H2O. The structure and morphology of the CeO2 HSs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption isotherms. The SEM and TEM images indicated that the as-prepared double-shelled CeO2 (about 400-500 nm in diameter) were aggregates of nanoparticles with sizes of about 15 nm. The shape and composition of the as-obtained products could be controlled by adjusting the ratio of PEG-400 and H2O in the solvothermal process. The effects of PEG-400/H2O ratio, solvothermal temperature and reaction time on the morphology evolution of as-prepared products were investigated, and the possible formation mechanism was proposed based on nucleation and the Ostwald ripening process as well as the soft-template function of PEG-400. In addition, the double-shelled CeO2 HSs show high electrocatalytic activity towards uric acid (UA) oxidation and thus exhibit good biosensor activities toward the detection of trace amounts of UA.