A highly selective SBA-15 supported fluorescent turn-on sensor for the fluoride anion

In an effort to improve the performance of organic-based F- receptors, organo-silica receptors are being developed taking advantage of the large surface area that mesoporous silica offers. In this work, we investigated the possibility of using a simple piece-wise assembly method to immobilize silyl-ether protected fluorescein isothiocyanate (FITC) molecules (receptor 1) on the surface of 3-aminopropyl-trimethoxysilane (APTES) and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (APAEAETMS) modified SBA-15 to form sensors ASBA and TSBA, respectively. We showed that aqueous solutions of TSBA (or ASBA) produce distinct changes in absorption and emission spectra upon F- addition due to the F- directed cleavage of Si-O bonds on receptor 1. TSBA (or ASBA) remained stable upon prolonged exposure to UV light (losing similar to 0.12% of its fluorescence intensity), and was highly selective towards F- over other common anions (Cl-, Br-, I- HPO42-, ACO(-), and NO3-). Furthermore, the sensitivity of this type of sensor architecture followed a dependence on the kind of amino-silane compound used, which opens up the possibility of synthesizing sensors with tailored detection limits. The detection limit of TSBA and ASBA was 0.02 mu M and 0.5 mu M, respectively.