A polymer membrane tethered with a cycloruthenated complex for colorimetric detection of Hg²⁺ ions

A new cyclometallated ruthenium complex (Ru1) involving a 2-(2-thienyl)pyridine and a benzo[e]indolium block connected with a hexanoic acid was successfully synthesized and characterized, which exhibited the high sensitivity and selectivity to Hg²⁺ over other common metal ions with the detection limit of as low as 0.053 μM in aqueous system. Then, it was grafted onto a polymer membrane to afford a Hg²⁺-sensitive membrane (sensor 1), which was characterized by FT-IR, SEM and XPS spectra, respectively. When sensor 1 was dipped into the aqueous solution of Hg²⁺ ions, the color of the membrane changed from dark-red to yellow, which could be observed by naked eyes easily. It should be noted that the membrane can absorb Hg²⁺ ions well in aqueous solution and the adsorption capacity of this polymer membrane for Hg²⁺ ions was determined by atomic absorption spectroscopy, indicating that it also could be used as a potential material for removal of Hg²⁺ ions.