A highly sensitive and selective colorimetric “Off-On” chemosensor for Cu2+ in aqueous media based on a rhodamine derivative bearing thiophene group

A new colorimetric “off-on” chemosensor based on rhodamine derivative bearing thiophene group has been synthesized. The chemosensor shows an excellent sensitivity and selectivity for Cu2+ over competing metal ions (Pb2+, Hg2+, Fe3+, Fe2+, Zn2+ Cd2+, Mn2+, Ba2+, Ag+ and Cr3+) in H2O-EtOH solution (1/4, v/v). A distinctive peak at 561 nm appears in the UV-vis absorption upon the addition of Cu2+ in the rhodamine derivative solution and an obvious color change to be pink from colorless. The interaction of Cu2+ and the chemosensor are proven to adopt a 1:1 binding stoichiometry, and the recognition process is expected to be completed within 1 min. With a detection limit of 1.7 × 10−7 mol/L, the chemosensor shows great potential to monitor Cu2+ in environmental analysis systems.