Photoluminescence quenching of water-soluble conjugated macromolecule by bipyridinium derivatives

Quenching of the photoluminescence (PL) from the water soluble conjugated m acromolecule, poly[5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene], MBL- PPV, by 4,4'-dipyridyl, Dpy, and by six bipyridinium derivatives with diffe rent charges was studied. The linear Stern-Volmer constant (K-sv) was 1-2x1 0(5) M-1 for the neutral quenchers. For the charged quenchers, K-sv increas es when the charge on the quencher is increased, from 1-3x10(6) M-1 for sin gly charged quenchers to 2x10(7) M-1 for bipyridinium derivatives with char ge +2 and +4. A modified Stern-Volmer equation, including the sphere-of-act ion contribution, is used to discuss the upward curvature observed in the S tern-Volmer plots for the charged quenchers at higher concentrations.