Coordination-driven reversible supramolecular assembly formation at biological pH: Trace-level detection of Hg2+ and I− ions in real life samples

Pyridine coupled bisbenzimidazole probe has been developed for colorimetric sensing of heavy metal pollutants in the aqueous medium. Mechanistic investigation indicates that Hg2+ ions (detection limit: 7.5 ppb) bind to the pyridyl nitrogen ends and form linear supramolecular assembly. Red-shifted absorption and fluorescence maxima upon addition of Hg2+ ions were observed, presumably caused by charge transfer interaction and coordination-driven planarization of the biphenyl backbone. Additionally, the in-situ formed mercury complex was utilized for selective recognition of iodide ion (detection limit: 20.2 ppb). Considering its high sensitivity, the present system was utilized in analysing Hg2+ in natural water and in presence of albumin protein. The high recovery values ranging from 95 to 98% with substantially low relative standard deviation (<4%) confirm the suitability of the present method in estimating trace-level of Hg2+ even in real-life samples. Imaging of intracellular Hg2+ ion was also achieved in cervical cancer cells. Low-cost paper strips are designed for rapid, on-site detection of Hg2+ without engaging any sophisticated analytical tools or trained personnel.