In vitro sensing of Cu(+) through a green fluorescence rise of pyranine

Pyranine as a new class of fluorescent chemosensor for the Cu(+) ion is reported. The probe is capable of discriminating ranges of cations from the Cu(+) ion, even in competing environment. The dye displayed a rapid fluorescence response (t1/2 = 1.66 min) towards the Cu(+) ion, and the micromolar detection limit enabled the detection of the ion in environmental samples. The observed stoichiometry of complexation between pyranine and Cu(+) was 2 : 1. Interestingly, the sensing characteristic was specific to only neutral pH. A metal-to-ligand charge-transfer (MLCT)-based mechanism of sensing was proposed based on electron spin resonance (EPR), Raman spectroscopic and cyclic voltammetric studies.