Effect of pentanol on morphologies and pore structure of mesoporous silica

Using wormlike micelles of cetyltrimethylammonium bromide (CTAB) and nitric acid as templates, fibrous mesoporous silica was synthesized and the effects of pentanol on the morphologies and ordered pore structure of mesoporous silica were studied. The resulting mesoporous silica was characterized by small-angle X-ray diffraction, nitrogen adsorption-desorption measurements, and scanning electron microscopy. Results showed that the amount of mesoporous silica with fibrous shapes decreased with the decrease of the molar ratio of CTAB to pentanol and that mesoporous silica with a spherical appearance only was obtained at a molar ratio of 1:3 (CTAB to pentanol). The pore structure of mesoporous silica was more ordered when the molar ratio of CTAB to pentanol was between 1:1 and 1:2, and distances between centers of two adjacent pores increased with the decrease of the molar ratio of CTAB to pentanol. There existed a type IV adsorption isotherm and an H1 hysteresis loop in N2 adsorption-desorption curves; total pore volume and most probable pore size with Barrett-Joyner-Halenda diameter increased with the decrease of the molar ratio of CTAB to pentanol. The result was in agreement with that of small-angle X-ray diffraction.