A novel chemosensor for sensitive and facile detection of strontium ions based on ion-imprinted hydrogels modified with guanosine derivatives

A novel chemosensor is developed for the sensitive and facile detection of trace strontium ions (Sr 2+ ) based on the ion-imprinted hydrogels. With Sr 2+ as the templates, the ion-imprinted hydrogels are synthesized by copolymerizing the ion-responsive units 5'-O-acryloyl-2',3'-O-isopropylidene guanosine (APG) and the thermo-responsive units N -isopropylacrylamide (NIPAM). In the presence of Sr 2+ , APG units can self-assemble to form planar G-quartets via the complexation with Sr 2+ , which are introduced into the gel network during polymerization. Then Sr 2+ templates can be removed by multiple repeated washing. When re-exposed to Sr 2+ , the relaxed G-quartets can recognize Sr 2+ , leading to the weakening of electrostatic repulsion between the four oxygen atoms in the G-quartets and inducing the shrinkage of the hydrogels. In this work, the Sr 2+ -imprinted chemosensors are designed as the grating systems for detecting trace Sr 2+ . Based on the array of hydrogel strings synthesized on a nano-scale, the smart grating systems thus constructed can convert and amplify the Sr 2+ concentration signals to the easily-measurable optical signals . With the Sr 2+ -imprinted hydrogel gratings, trace Sr 2+ (10 -11 M) in an aqueous solution can be detected sensitively. Moreover, the proposed Sr 2+ -imprinted chemosensors can be integrated with other smart systems for developing various detectors with high performance.