Selective adsorption of glucose-derived carbon precursor on amino-functionalized porous silica for fabrication of hollow carbon spheres with porous walls

Coating of polysuccharide (PS) generated by hydrothermal treatment of glucose on Stöber's silica particles was examined. Uniform surface coverage of PS was achieved when the silica particles, the surfaces of which had been modified with amino groups, were mixed during the hydrothermal reaction of glucose. On the other hand, bare silica could not be coated with PS upon addition to the hydrothermal reaction solution; instead, this produced spherical PS particles with diameters of a few tens of nanometers beside silica particles. The significant effect of surface amino-functionalization of silica particles on the coverage of PS is attributable to induction of an electrostatic attraction between the positively charged amino-functionalized silica surface and negatively charged PS. When silica (core)-porous silica (shell) spheres were used instead of Stöber's silica, efficient filling of the pores of the silica shell with PS could also be achieved by amino-functionalization of the surface of the porous silica shell. The silica (core)-PS (shell) materials as-obtained were converted into isolated hollow carbon spheres with well-developed porous shell structures by heat treatment under a vacuum followed by treatment with aqueous hydrofluoric acid.