Detecting trace of mercury ions in water using photoacoustic method enhanced by gold nanospheres

A gold nanospheres (Au NSs)-enhanced photoacoustic (PA) system has been developed to detect parts per trillion (ppt)-level mercury ion (Hg 2+ ) in aqueous environments, which combines the advantages of the high sensitivity of PA detection and high extinction coefficient of Au NSs. 4-mercaptophenylboronic acid (MPBA) is used as the aggregation agent to detect Hg 2+ by a designed PA system. Experimental results demonstrate a linear relationship between the amplitude of PA signals and logarithmic concentration of Hg 2+ in the range of 10 pM-1 μM (R=0.994). The detection limit of this Au NSs-enhanced PA system is 78 pM (16 ppt, S/N=3) with a quick response time of 1 min. This method has excellent selectivity for Hg 2+ over other heavy metal ions , alkali, and alkaline earth metal ions . The system is cost-effective and shows a great potential for quick detection of Hg 2+ trace in water with very high sensitivity.