Amrita Chatterjee, Mithun Santra, Nayoun Won, Sungjee Kim, Jae Kyung Kim, Seung Bin Kim and Kyo Han Ahn*

Department of Chemistry and the Center for Electro-Photo Behaviors in Advanced Molecular Systems, POSTECH, San 31, Hyoja-dong, Pohang, 790-784, Republic of Korea

Abstract
A novel rhodamine-based fluorogenic and chromogenic probe for Ag⁺ ions in aqueous media is developed, which can be also used for the detection of AgNPs. The sensing mechanism is based on irreversible tandem ring-opening and -forming processes promoted by Ag⁺-coordination to the iodide of the probe, which is accompanied by both color and turn-on type fluorescence changes. The probe shows remarkably high selectivity over other metal ions and detects silver ions up to 14 ppb.