Low-Molecular-Weight Gelators as Dual-Responsive Chemosensors for the Naked-Eye Detection of Mercury(II) and Copper(II) Ions and Molecular Logic Gates

Three quinoline-based Low Molecular Weight Gelators (LMWG's), containing benzimidazole and long alkyl chain moieties, with excellent gelation abilities have been designed and synthesized. The gel properties were studied by IR and NMR spectroscopies, scanning electron microscopy (SEM) and rheological measurements. The gelators showed excellent ability as efficient colorimetric and fluorescent sensors for detection of Hg2+ and Cu2+ ions in aqueous media. The supramolecular gel was selectively transformed into solution in the presence of Hg2+ ion alongside complete quenching of its fluorescence intensity. In the presence of Cu2+ ion, the gelator exhibited a significant color change from white to dark pink and its fluorescence intensity was substantially reduced in gel-gel state. Other competing ions such as Mn2+, Zn2+, Pb2+, Cd2+, Mg2+, Ni(2+)and Al3+, induced no change under the same conditions. The gel function as molecular logic gate was also investigated and found that, the gelators implement the functions of INH and NOT gates with water and Hg2+ ion as inputs and gel formation and fluorescence intensity as outputs.