Rational Calibration Strategy for Accurate and Sensitive Colorimetric Detection of Iodide and <scp>l</scp>-Thyroxine Based on Gold Triangular Nanoplates

Abstract

We developed a sensitive and accurate colorimetric method to detect iodide (I–) and l-thyroxine by etching gold triangular nanoplates (AuTNPs) in the presence of H2O2. The morphological changes of AuTNPs resulted in vivid color variations of the nanoprism dispersion, accompanied by a blue shift of the in-plane localized surface plasmon resonance (LSPR) peak, enabling visual and photometric sensing. To improve the accuracy and the linear range, the overlapping out-of-plane and in-plane LSPR peaks of the AuTNPs were deconvoluted, and a new calibration model was established by plotting the square of the in-plane LSPR wavelength shift against the concentration of the analytes. Under optimum conditions, the limits of detection (LODs) for iodide reached 1 μM and 50 nM by the naked eye and photometry, respectively, and the corresponding LODs for l-thyroxine were 200 and 13.7 nM. Importantly, improved accuracy and linear range were obtained by the new data processing strategy. The method was applied in detecting iodide in tap and drinking water samples and l-thyroxine in pharmaceutical tablets, indicating its potential for real sample analysis.