A Simple Strategy for Prompt Visual Sensing by Gold Nanoparticles: General Applications of Interparticle Hydrogen Bonds

摘要

Visual sensing based on gold nanoparticles (GNPs) is important and attractive because the intense red color arisingfrom surface plasmon (SP) absorption[1] allows the outcome of analytical measurements to be read with the naked eye. The typical mechanism for such colorimetric sensing involves a color change from red to blue through the analyte-triggeredaggregation of GNPs.[2–5] Herein, we report an opposite transformation in which the GNPs are initially aggregatedand promptly become dispersive in response to an analyte. Toachieve the goal of rapid sensing, the interparticle attraction for the initial aggregation should be easily weakened by the analyte–GNP interactions. Scheme 1 illustrates the proposed concept. The GNPs are bifunctionalized by ([15]crown-5)CH2O(CH2)4SH (denoted 15c5-C4-SH) and thioctic acid (TA), which are responsible for recognition and GNP aggregation, respectively. PbII, a common environmental contaminant that is detrimental to human health, is selected as the target ion for this model ystem because its association constants with 15c5 and acetic acid are 3630[6] and 500,[7] respectively, which are considerably higher than those of most metal ions. The affinity of PbII toward the functionalities imposes positive electrostatics on the GNPs and leads to a very fast aggregation-to-dispersion transformation. Herein, we show that this methodology offers a rapid, highly selective, and sensitive PbII sensor.