Preparation of three-dimensional inverse opal SnO2/graphene composite microspheres and their enhanced photocatalytic activitiesElectronic supplementary information (ESI) available: Preparation of GO, XRD spectra of IO-SnO2/graphene composite microspheres, XPS, XRD and Raman spectroscopy of GO after the heat treatment, and TGA analysis of GO, rGO and PS microspheres. See DOI: 10.1039/c4ta05898d

Three-dimensional inverse opal SnO 2 /graphene (IO-SnO 2 /graphene) microspheres with a size of several tens of microns are first prepared by a well-designed two-step calcination of polystyrene (PS) colloidal crystal template balls infiltrated with the sol precursors of SnO 2 and graphene oxide. The polystyrene colloidal crystal template balls are formed by the self-assembly of monodispersed PS microspheres confined in water droplets of an inverse emulsion induced by the slow evaporation of water. Characterization with scanning electronic microscopy, Raman spectra, X-ray diffraction and X-ray photoelectron spectroscopy proved the ordered macroporous inverse opal composed of crystalline SnO 2 and in situ reduced GO during the calcination. The pore size depends on the PS microspheres. The UV-vis diffusive reflectance spectra show that the light absorption edge of the prepared IO-SnO 2 /graphene microspheres can shift more than 400 nm. The photoluminescence spectra indicates that the IO structure and the introduction of rGO make the charge carriers transfer fast and retard the hole/electron recombination in the IO-SnO 2 /graphene microspheres so that their photocatalytic performance on the UV photolysis of methyl orange is considerably better than that of commercial SnO 2 nanoparticles. However, the photocatalytic performance also depends on the content of GO. The addition of 0.06 wt% of GO achieves the best photocatalytic effect. Excessive GO will result in a diminished catalytic activity. This work provides a way to fabricate a new morphological SnO 2 based materials with enhanced photocatalytic activity, which helps in the exploration of new photocatalysts with high performance. 3D inverse opal SnO 2 /graphene composite microspheres with enhanced photocatalytic activities were first prepared using polystyrene colloidal crystal balls as a template.