Pyranine (Solvent Green 7) is reported as a new class of fluorescent chemosensor for the Cu+ ion.

Pyranine (Py) is a fluorescence probe[3] and is capable of discriminating ranges of cations from the Cu+ ion, even in competing environment. Pyranine displays a rapid fluorescence response (t1/2=1.66 min) towards the Cu+ ion, and the micromolar detection limit enables the detection of the ion in environmental samples. The observed stoichiometry of complexation between Pyranine and Cu+ is 2:1[1]. The pH is calculated by measuring the ratio of fluorescent intensity at two excitation wavelengths, I463/I404, which is dependent on pH but independent of the concentration of the fluorophore and other variables which can alter the intensity. In the rabbit eye, Pyranine in the cornea and anterior chamber is observed to undergo easily measurable changes in fluorescent ratios associated with lid closure and contact lens wear, indicating its sensitivity to mild changes in pH[2].