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

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 Si-O bond and thus destroyed the outer protecting layer of the probe, and further triggered the aggregation of internal MPD-AuNPs by forming N-H-F 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 1.0-7.0 mu g mL(-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. (C) 2014 Elsevier B.V. All rights reserved.