Preparation and photocatalytic ability of ordered hollow Ag/TiO_2 spheres with square array

At low temperature,colloidal crystal template was prepared by one-substrate vertical deposition.In the formed colloidal crystal,large areas of square array were observed,because thermal motion of particles was inhibited at low temperature and dislocation was happened.Subsequently,Ag nanoparticles and titania were deposited one by one on the PS spheres by an electroless plating method and sol-gel technology.Finally the sample was calcined to remove the colloidal crystal template and the ordered hollow Ag/TiO2 spheres with square array were successfully prepared.The sample was characterized by scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that the sample clearly retains its original square array of the colloidal crystal template and possesses highly ordered nanostructure.We chose photodegradation of methyl orange to evaluate the photocatalytic ability of square ordered hollow Ag/TiO2 spheres.For comparison,we also evaluated the photocatalytic activity of flat TiO2 film and square ordered hollow TiO2 spheres.The results show that the as-prepared ordered hollow Ag/TiO2 sphere exhibits the most efficient photocatalytic activity.The long-range ordering porosity and the addition of Ag nanoparticles are the main factors leading to the improved photocatalytic activity.