PH-DEPENDENT FLUORESCENCE OF MEROCYANINE EOSIN-LABELED WATER-SOLUBLE POLYMERS

The pH-dependent fluorescence and energy-transfer properties of water-soluble polymers labeled with both a donor (eosin) and acceptor (merocyanine) were studied. Eosin emission intensity increased with pH increases. This observation conflicted with the expectation that the fluorescence intensity of eosin should diminish with pH increases resulting from increased spectral overlap between the dyes. The diminished fluorescence intensity at low pH is attributed to strong electrostatic attraction bringing the two chromophores into proximity and resulting in efficient energy transfer even at very low polymer concentrations. © 1990, American Chemical Society. All rights reserved.