Surface plasmon resonance sensor for Hg(II) detection by binding interactions with polypyrrole and 2-mercaptobenzothiazole

A SPReeta sensor was developed for Hg(II) detection by monitoring the binding interactions with polypyrrole (PPy) and 2-mercaptobenzothiazole (2-MBT). Chemical binding of Hg2+ ions in water with a PPy thin film immobilized on the gold surface could be monitored by surface plasmon resonance (SPR). The SPR angle was found to be a useful analytical signal for monitoring the binding interaction. An increase in SPR angle of 780±10 RU (1 RU=1×10−4°) was obtained for 10 ppm Hg2+ biding with PPy film, and a linear dynamic range was observed between 0.1 and 10 ppm. After Hg2+ absorption into the polymer, enhancement of the SPR detection sensitivity was achieved by adding 2-MBT to the injected solution. This produced further binding interaction with the Hg2+ bound on PPy. The detection limit was improved down to 0.01 ppm with a SPR angle increase of 20±10 RU. It should be recognized that both 2-MBT and PPy worked together in the present SPReeta method to enhance the specificity of Hg2+ determination.