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 (Hg2+). In the present of Hg2+, MTA molecules would be displaced quickly from the surface of gold nanorods due to the high affinity of Hg2+ 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 Hg2+ (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 Hg2+-contaminated water samples.