A novel rhodamine B-based "off-on'' fluorescent sensor for selective recognition of copper (II) ions.

A novel rhodamine based sensor RBH was developed and synthesized by rhodamine B with 3-methyl-2-benzothiazolinone hydrazone, which exhibited high selectivity and sensitivity for sensing Cu2+ ions in the presence of other important relevant metal ions in aqueous acetonitrile. As an "off-on" fluorescent sensor, RBH exhibited a UV-vis absorption increase at 570 nm and a 132-fold significant fluorescence enhancement at 580 nm with a distinct color change from colorless to purple upon the addition of Cu2+ ions. The fluorescence intensity of RBH is linear with the Cu2+ ions concentration with low limit of detection. Furthermore, the sensor RBH has been successfully utilized for fluorescence imaging of Cu2+ ions in living cells. The sensor could potentially recognize Cu2+ ions in biological system.