Ultrasensitive and selective gold film-based detection of mercury (II) in tap water using a laser scanning confocal imaging-surface plasmon resonance system in real time

•We reported an ultrasensitive and selective detection for Hg2+ ions using LSCI-SPR.•The principle of the LSCI-SPR sensor is the specific coordination between Hg2+ and thymine bases.•The fluorescence quenching for rhodamine-labeled ssDNA fitted well with the changes in SPR.•The detection limit was as low as 0.01 ng/ml for Hg2+ ions in ultrapure and tap water.•This LSCI-SPR sensor showed excellent selectivity over a spectrum of interference metal ions.

An ultrasensitive and selective detection of mercury (II) was investigated using a laser scanning confocal imaging-surface plasmon resonance system (LSCI-SPR). The detection limit was as low as 0.01 ng/ml for Hg2+ ions in ultrapure and tap water based on a T-rich, single-stranded DNA (ssDNA)-modified gold film, which can be individually manipulated using specific T–Hg2+–T complex formation. The quenching intensity of the fluorescence images for rhodamine-labeled ssDNA fitted well with the changes in SPR. The changes varied with the Hg2+ ion concentration, which is unaffected by the presence of other metal ions. The coefficients obtained for ultrapure and tap water were 0.99902 and 0.99512, respectively, for the linear part over a range of 0.01–100 ng/ml. The results show that the double-effect sensor has potential for practical applications with ultra sensitivity and selectivity, especially in online or real-time monitoring of Hg2+ ions pollution in tap water with the further improvement of portable LSCI-SPR instrument.