Incorporation of the fluoride induced Si[sbnd]O bond cleavage and functionalized gold nanoparticle aggregation into one colorimetric probe for highly specific and sensitive detection of fluoride

Abstract

A highly selective and sensitive probe was developed for the field test of F− in environmental waters. The probe was fabricated by anchoring 4-mercaptopyridine (MPD) on AuNPs via Au–S interaction to form MPD-AuNPs, and further assembling 3-aminopropyltrimethoxysilane (APTMS) on the surface of MPD-AuNPs. The hydrolysis and cross-link of APTMS resulted in a thin monolayer of Si–O–Si protecting layer to encapsulated MPD-AuNPs. In the assay, F− reacted with SiO bond and thus destroyed the outer protecting layer of the probe, and further triggered the aggregation of internal MPD-AuNPs by forming NHF hydrogen bond. The F− induced aggregation of functionalized AuNPs gave rise to significant solution color switch from red to blue, which facilitated visual assay of F− in the range of 1.0–7.0μgmL−1 by naked eyes. The probe is able to discriminate F− from a wide range of environmentally dominant ions, thus it can be applied to detect F− in drinkable water with satisfactory results that is agreed well with that of using ion chromatography.