A Cu2+ chemodosimeter based on amplified fluorescence in the red region

A new chemodosimeter based on the spirolactam form of rhodamine 101 hydrazide (I) has been synthesized. This chemodosimeter is found to exhibit an irreversible colorimetric and fluorogenic response toward Cu2+ in aqueous solution in a highly selective, sensitive and rapid manner. The dominating fluorescence maximum is red-shifted to 600 nm. Such a red region is reported uniquely among the rhodamine chemodosimeters on Cu2+. The colorimetric and fluorogenic response of I toward Cu2+ is proposed to be attributed to Cu2+-promoted redox hydrolysis of I.