Release kinetics of tebuconazole from porous hollow silica nanospheres prepared by miniemulsion method

Triazole fungicide tebuconazole was incorporated in porous hollow silica nanospheres (PHSNs) by the miniemulsion method to obtain controlled release properties. PHSNs were fabricated using tetraethyl orthosilicate (TEOS) as the silica source and an ethyl acetate as droplet templates. The tebuconazole was dissolved in droplet templates and wrapped into PHSNs as the volatilization of droplet templates, instead of a loading procedure such as the simple immersing loading method or supercritical fluids technology. The factors related to loading efficiency and controlled release behaviors of free tebuconazole from tebu-PHSNs were investigated. Results showed that the loading efficiency could reach about 45% (w/w) by changing the concentration of hexadecyl trimethyl ammonium bromide (CTAB) and the ratio of TEOS to ethyl acetate. The values for the diffusion exponent n were in the range of 0.29-0.61, which indicated that the release of tebuconazole was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, T-50, was also calculated for the comparison of formulation in different conditions. The results showed that the formulation with the lower temperature, pH value, and larger particle size had lower values of T-50, which meant a slower release of the active ingredient. (C) 2012 Elsevier Inc. All rights reserved.