A Simple Paper-Based Colorimetric Device for Rapid Mercury(II) Assay

Contamination of the environment by mercury(II) ions (Hg2+) poses a serious threat to human health and ecosystems. Up to now, many reported Hg2+ sensors require complex procedures, long measurement times and sophisticated instrumentation. We have developed a simple, rapid, low cost and naked-eye quantitative method for Hg2+ environmental analysis using a paper-based colorimetric device (PCD). The sample solution to which platinum nanoparticles (PtNPs) have been added is dispensed to the detection zone on the PCD, where the 3,3,5,5-tetramethylbenzidine (TMB) substrate has been pre-loaded. The PtNPs effect a rapid oxidization of TMB, inducing blue colorization on the PCD. However, Hg2+ in the solution rapidly interact with the PtNPs, suppressing the oxidation capacity and hence causing a decrease in blue intensity, which can be observed directly by the naked eye. Moreover, Hg2+ at concentrations as low as 0.01 uM, can be successfully monitored using a fiber optic device, which gives a digital readout proportional to the intensity of the blue color change. This paperbased colorimetric device (PCD) shows great potential for field measurement of Hg2+.