Colorimetric biosensing of Mercury (Ⅱ) ion using the novel aptamer modified gold nanoparticles as a probe

A simple and rapid colorimetric method was developed for the detection of Hg2+based on the specific thymine T-Hg2+-T structure and gold nanoparticles (Au NPs) in the presence of a given high concentration of salt. The gold nanoparticles were prepared by the Na BH4 reduction method. Transmission electron microscopy, laser particles size analyzer, and UV-vis spectroscopy were used to characterize the samples. The aptamer was designed to attach to Au NPs and effectively prevent Au NPs from salt induced aggregation. While the presence of Hg2+ions, the Au NPs were less well-protected thus aggregated at the salt concentration, resulting into a color change. It could be colorimetric quantitative analysis of the concentration of Hg2 +. The results showed that the product with good stability and good distribution could be obtained with taking sodium borohydride as reductant Au NPs had a mean diameter of 27 nm. It was observed that the aptamer-stabilized Au NPs solution showed a color change from red- to- blue when Hg2 +was added into the solution. The aptamer- Au NPs exhibited strong fluorescence emission, while upon addition Hg2 +, the solution showed a dramatic increase of the fluorescence intensity as a result of the aggregation behavior of the Au NPs. The paper based sensor showed high selectivity for 8 kinds of metal ions.