Gelation–based visual detection of fluoride ion: Strategic use of silyl protection–deprotection chemistry

Abstract

• A gelation-based visual detection of fluoride ion is reported. • Fluoride ion converted a triphenylsilyl group-containing gelator (gel) into a nongelator (gel degradation). • Quantitative and semi-quantitative detection methods are reported. • Fluoride ion detection limit is considerably better than many existing gelation-based methods. We describe the design, synthesis, and visual fluoride ion detection by a new small-molecule gelator in this work. This gelator contains a triphenylsilyl group which is easily removed in the presence of fluoride ion. The strategic use of silyl group protection-deprotection chemistry enabled the detection of fluoride ion visually. We investigated two different routes for this purpose. In the first route, gels were responsive to fluoride ion and degraded in its presence. Gels degraded faster with an increase in fluoride ion concentration. Fluoride ion quantification was possible by correlating fluoride ion concentrations with gel-degradation times. In the second route, when gelation tests were performed in the presence of fluoride ion, gel formation was suppressed, and multiple visually distinguishable states were obtained. A semi-quantitative analysis for fluoride ion was achieved in this case. The performance and detection limit of this new gelator is superior to many existing gelation-based methods. Furthermore, the gels were fully characterized using SEM, TEM, FTIR, XRD, contact angle, fluorescence, and UV–vis spectroscopy techniques.