A Novel Rhodamine B Derivative as a “Turn-on” Fluorescent Sensor for Cu2+ 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.