Effects of surface properties and textures of imprinted silica on recognition of bisphenol A

In this study, we have successfully prepared organically modified silica imprinted with bisphenol A though an acidic catalyzed sol-gel method. To understand the effects of surface interactions and diffusion on the recognition ability of the imprinted gels toward bisphenol A, the adsorption capacity and selectivity with respect to the surface functional groups, iso-electric points, pore sizes and porosity of the silica were investigated. We used phenyltrimethoxysilane (PTMOS) and 3-aminopropyl trirthoxysilane(APTES) as functional monomers and tetraethoxysilane (TEOS) and methyltrimehoxysilane (MTMOS) as cross linkers in the sol-gel process. Relative to the hydroxyl and amine groups, phenyl groups exhibited stronger □-stacking interaction with bisphenol A and higher improvement on the adsorption capacity of the imprinted silica. However, they resulted in lower recognition ability of the imprinted gels for similar aromatic compounds. The porosity, average pore sizes as well as the adsorption capacity of the gels increased in the presence of MTMOS. Since the structures of silica gels are rigid, methyl groups expanded the pore channels thus facilitated the diffusion of target compounds the inorganic matrix to the imprinted sites. The optimal gels performed a linear adsorption of 0.03-4.36 mg/g when initial concentrations of bisphenol A were 4-400 ppm. The saturated capacity was 151.5 mg/g. This value was 4.4 times higher than the maximal capacity of non-imprinted silica (34.7mg/g). In addition, the selectivity of bisphenol A was 5.3 time higher relative to phenol. These results indicate that the imprinted silica is highly promising to be used as the advanced sensing materials for detection of bisphenol A.