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.

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Gold nanomaterials have been used extensively in colorimetric detection of mercuric ions (Hg 2+ ) due to their shape-and size-dependent, ultrastrong localized surface plasmon resonance (LSPR). Conventional detection was performed by first synthesizing the nanomaterials, and then applying them to signal-transducing reactions. We herein report a convenient method for detecting Hg 2+ based on gold triangular nanoprisms (AuTNPs). During the seeding-growth process, Hg 2+ added to the growth solution was co-reduced and deposited on the high-energy facets of the gold seeds, affecting the deposition patterns of the subsequently generated Au 0 and ultimately leading to the formation of defective AuTNPs. Morphological changes were reflected by the in-plane dipole LSPR wavelength shift, which was proportionally related to the concentration of Hg 2+ . To improve the selectivity, the interference from Ag + was eliminated by a stepwise preparation-selective precipitation approach. Under the optimized conditions, Hg 2+ could be selectively detected with 20 min, with a detection limit of 0.12 nM. Finally, the method was successfully applied to detecting trace Hg 2+ in fortified drinking, mineral and rain water samples, with recoveries ranging from 95.17% to 110.6%.

A multi-logic gate platform was designed based on morphological changes of gold nanorods (AuNRs) resulted from the iodine-mediated etching. By utilizing the anti-etching effects of mercapto compounds and Au-Hg amalgams as well as the etch-promoting effect of Cu2+, we successfully built five logic gates, namely, AND, NOR, XNOR, YES and IMPLY, along with a three-input combinational logic gate XNOR-IMPLY. The platform was versatile and easy to use, did not require complex surface modification or separation/purification steps as the conventional AuNR-based logic gates did. The logic operations, accompanied by distinct color changes, enabled multi-task detection by naked-eye for ‘have’ or ‘none’ discrimination or highly sensitive and selective analysis by spectroscopy with wide linear ranges.