Novel Hg(2+)-Selective Signaling Probe Based on Resorufin Thionocarbonate and its μPAD Application

In this study, a novel resorufin thionocarbonate-based Hg(2+)-selective signaling probe (RT) for microfluidic paper-based analytical device (μPAD) applications is reported. The designed probe, RT, was readily synthesized by the one-step reaction of resorufin with phenyl thionochloroformate. The RT probe displayed a prominent color change from yellow to pink and a marked turn-on fluorescence signaling behavior exclusively toward the Hg(2+) ion. The signaling of RT was due to Hg(2+)-induced hydrolysis of the phenyl thionocarbonate moiety to form the parent resorufin dye, which restored its spectroscopic properties. In addition, RT exhibited the Hg(2+)-selective signaling behavior without interference by coexisting environmentally relevant metal ions. The detection limit for Hg(2+) in simulated wastewater samples was estimated to be 5.8 × 10(−8) M. In particular, an RT-equipped μPAD prepared using a wax printing technique enabled simple and convenient determination of Hg(2+) ions in simulated wastewater samples, with a detection limit of 5.9 × 10(−6) M.