Sensitive and rapid detection of Cr³⁺ in live cells by a red turn-on fluorescent probe

A new probe RB-CR for the detection of Cr³⁺ was constructed based on the conjugation between rhodamine B and phenylthiourea. The Cr³⁺ could trigger opening of the rhodamine spirolactam of RB-CR upon complexation selectively, sensitively and rapidly, resulting in a pronounced enhancement of absorption and fluorescence signal. Further fluorescence imaging study has suggested that RB-CR could be applied as a probe for Cr³⁺ surveillance in living HepG2 cells with low cytotoxicity, which provide us the feasibility of exploring the Cr³⁺ recognition process by the turn-on fluorescence response.