Silica Hollow Spheres with Ordered and Radially Oriented Amino-Functionalized Mesochannels

Using anionic surfactant as templates, ordered mesoporous silica hollow spheres (MSHSs) with radially oriented mesochannels were synthesized with the aid of ultrasonic irradiation. The product was consisted of intact and dispersed hollow spheres with the diameter mostly in the range of 100−500 nm. The hollow spheres possessed uniform shell with the thickness of 35−40 nm, and the shell with radially oriented mesopores exhibited well-ordered structure as confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. After extraction of the anionic surfactant templates by solvent, silica hollow spheres with ordered and radially oriented amino-functionalized mesochannels were obtained. Moreover, by adjustment of the sonochemical processing time, the shell thickness, mesostructure (hexagonal, radial, or disordered), and shape of the inner cavity (hexagonal or spherical shape) of the hollow spheres could be facilely tuned. The formation process of the radially ordered mesostructure could be attributed to a relatively slow cooperative realignment process of the silica/surfactant hybrid mesophase in this anionic surfactant templating system. The effectiveness of the radially aligned mesopores was validated by a drug (flurbiprofen) release experiment, in which the hollow spheres exhibited relatively high drug storage capacity (>1000 mg g−1) and much faster drug release rate than that of the flakelike mesoporous SBA-15 particles.