A colorimetric probe for the rapid and selective determination of mercury(II) based on the disassembly of gold nanorods

We report on a novel mercury(II)-controlled approach for the disassembly of gold nanorods (AuNRs) that has led to a detection system for Hg(II). The modified AuNRs were fabricated by functionalizing AuNRs with L-cysteine via a thiol group chemisorption-type of interaction. L-cysteine induces the assembly of AuNRs through cooperative electrostatic interaction upon which the color of the solution of the AuNRs changes from blue-green to gray dark. The addition of Hg(II), in turn, causes the disassembly of the modified AuNRs and the color of the solution returns to blue-green. This effect enables the optical determination of Hg(II) in aqueous solution, with a linear response in the 0.5 to 250 mu M Hg(II) concentration range, an excellent selectivity for Hg(II), and with recoveries ranging from 99 % to 106 % in spiked environmental water samples.