Label-free, sensitive colorimetric detection of mercury(II) by target-disturbed in-situ seeding growth of gold triangular nanoprisms

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%.