Colorimetric mercury detection with enhanced sensitivity using magnetic-Au hybrid nanoparticles

Due to the neural toxicity of mercury, there is a need for the development of on-site detection systems for Hg(2+) monitoring. To this end, a new colorimetric mercury detection probe, Fe(3)O(4)@SiO(2)@Au (magnetic-Au; Mag-Au) hybrid nanoparticles, has been developed. The Au on the surface of Mag-Au is an indicator of Hg(2+), which forms an AuHg alloy (amalgam) on their surface (Mag-Au@Hg), with excellent peroxidase-like activity. The oxidation of 3,3′,5,5′-tetramethylbenzidine by Mag-Au@Hg resulted in a color change of the indicator solution, which was enhanced with increasing Hg(2+) concentration. Mag-Au can be used to detect Hg(2+) at nanomolar concentrations. Additionally, magnetic separation can be used to easily purify and concentrate the Mag-Au@Hg from samples, and thus avoid interference from unwanted residues or colored samples. The feasibility of Mag-Au for Hg(2+) detection was tested with an artificial urine solution and it can be used to detect Hg(2+) in various real samples, such as river water, seawater, food, and biological samples.