Aggregation induced photoacoustic detection of mercury (Ⅱ) ions using quaternary ammonium group-capped gold nanorods.

Photoacoustic imaging is an emerging detection tool of metal ions. Mercury is a typical heavy metal pollutant that can cause severe water and soil pollution. Therefore, it is particularly meaningful to develop a photoacoustic probe with excellent selectivity and sensitivity for the detection of mercury ions. In this study, gold nanorods modified with (11-mercapto-undecyl)-trimethylammonium (MTA) molecules containing sulfydryl groups were designed and synthesized for the photoacoustic detection of mercury ions (Hg). In the present of Hg, MTA molecules would be displaced quickly from the surface of gold nanorods due to the high affinity of Hg toward sulfydryl group. Then gold nanorods were aggregated due to the loss of ligand protection on their surface, resulting in the enhancement of photoacoustic signals. In addition, this work showed a good linear relationship between the change of photoacoustic signal at 780 nm and the concentrations of Hg (0-10 µM). More importantly, the devised photoacoustic detection system performs good stability and anti-interference compared to the traditional colorimetric detection system, making it possible to apply to the actual Hg-contaminated water samples.