A Novel Rhodamine B Derivative as a “Turn-on” Fluorescent Probe for Cu 2+ with High Selectivity and Sensitivity

Abstract The quantity of “turn-on” probes for Cu²⁺ is relatively small, and the interference of other metal cations is obvious. In this research, a rhodamine B-based probe, 1-phenyl-3-methyl-5-hydroxypyrazole-4-benzoyl(rhodamine B) hydrazone (RBHP), was synthesized and characterized by ¹H NMR, electrospray ionization mass spectrum, elemental analyses, and X-ray single crystal diffraction. Selectivity studies on RBHP to metal cations, and fluorescence and UV–vis absorption spectra titrations of Cu²⁺ were also conducted. RBHP showed an extremely low fluorescence background signal in acetonitrile and could produce a “turn-on” fluorescent response to Cu²⁺. While, Na⁺, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Cr³⁺, Al³⁺ and Fe³⁺ induced no interference or very weak interference for the detection of Cu²⁺. RBHP could recognize Cu²⁺ with a low limit of quantification at 15 µM (~ 0.95 mg/L). RBHP revealed a possibility as a “turn-on” fluorescent probe for Cu²⁺ with high selectivity and sensitivity.