An anionic fluorescent dye; ex/em spectra = 425/503 nm, respectively; forms a ground state complex with viologen-type quenchers, inducing a red-shift in the absorbance spectrum from 425 to 464 nm; pH insensitive over the pH range of 4-10; can be used in solution or immobilized through attachment of an aldehyde functionalized monomer by reductive amination; has been used as a reporter for glucose sensing and for the detection of other saccharides