Effect of Synthesis Time on Morphology of Hollow Porous Silica Microspheres

Hollow porous silica microspheres may be applicable as containers for the controlled release in drug delivery systems (DDS), foods, cosmetics, agrochemical, textile industry, and in other technological encapsulation use. In order to control the surface morphological properties of the silica microspheres, the effect of synthesis time on their formation was studied by a method of water-in-oil (W/O) emulsion mediated sol-gel techniques. An aqueous phase of water, ammonium hydroxide and a surfactant Tween 20 was emulsified in an oil phase of I-octanol with a stabilizer, hydroxypropyl cellulose (HPC), and a surfactant, sorbitan monooleate (Span 80) with low hydrophile-lipophile balance (HLB) value. Tetraethyl orthosilicate (TEOS) as a silica precursor was added to the emulsion. The resulting silica particles at different synthesis time 24, 48, and 72 hours were air-dried at room temperature and calcinated at 773 K for 3 hours. The morphology of the particles was characterized by scanning electron microscopy and the particle size distribution was measured by laser diffraction. The specific surface areas were studied by 1-point BET method, and pore sizes were measured by Image Tool Software. Both dense and porous silica microspheres were observed after all three syntheses. Hollow porous silica microspheres were formed at 24 and 48 hours synthesis time. Under base catalyzed sol-gel solution, the size of silica particles was in the range of 5.4 mu m to 8.2 mu m, and the particles had surface area of 111 m(2)/g-380 m(2)/g. The longer synthesis time produced denser silica spheres with decreased pore sizes.