Ionic liquid-grafted probe for selective detection and individual identification of different metal ions in 100% aqueous solutions

Multi-ion-responsive probes are particularly attractive due to their high detection efficiencies and potential cost reductions, while there still remains the formidable challenge of discriminating different metal ions in pure aqueous media. Herein, a novel imidazolium chloride ionic liquid-grafted rhodamine B salicylaldehyde hydrazone (IMI-SARhBH) was rationally designed and developed as a promising multi-ion-responsive probe for the colorimetric detections and individual identifications of Cu 2+ and Al 3+ in 100% aqueous solutions. Benefitting from the remarkably hydrophilic nature of the grafted ionic liquid , the IMI-SARhBH was highly water-soluble, and showed excellent sensing performances for detections of Cu 2+ and Al 3+ under pure aqueous conditions in terms of high sensitivity, satisfactory selectivity, and strong anti-disturbance ability. More importantly, dissociation of the grafted ionic liquid in water made the probe positively charged, which caused electrostatic repulsion between itself and metal ions and thus offered the chance to differentially recognize Cu 2+ and Al 3+ . The Cu 2+ was repelled relatively weakly by IMI-SARhBH and thus identified quickly (<1 min), while the sensing detection of Al 3+ required a longer time (5 h) due to the relatively stronger electrostatic repulsion. Accordingly, a new and convenient method for individual identifications of Cu 2+ and Al 3+ from Cu 2+ –Al 3+ -coexisted solution was also successfully established.