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

Abstract

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-aminopropyltrimethoxysilane (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 ∼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 μM and 0.5 μM, respectively.