Fluorescent chemosensors facilitate the characterization of materials and biological systems. Cyclodextrin (CD), a conical sugar oligomer with a hydrophobic interior and exterior hydroxyl groups, is water-soluble and presents a binding site for fluorescent probes such as PRODAN (6-propionyl-2-dimethylaminonaphthalene). The quenching of PRODAN-based probes occurs as their environment is better able to donate hydrogen bonds, an effect which is enhanced by a twisted conformation of the carbonyl group of the probe. After titrating six structurally distinct probes with beta-CD, emission spectra were analyzed for binding constants, maximum increase of fluorescence quantum yield, and effective solvent acidity of the beta-CD environment. Probes with twisted conformations gave an approximately twenty-fold increase in maximum quantum yield and may bind more strongly to cyclodextrin. While the ideal sensor for microacidity should have increased response to changing environment, the increase should not come at the expense of the range of detectable solvent acidities
