Structure and aggregation of β-cyclodextrin-pyrene-analyte supramolecular sensor: Absorption/emission spectra and simulations

The possibility of using pyrene as a fluorescent probe in a model chemosensor composed of β-cyclodextrin-pyrene (Py-βCD) complex in aqueous solution was studied in the presence of several analytes (A) of different polarity. Absorption bands that prove the formation of the aggregated Py-βCD complex were found in the UV-VIS spectra of aqueous solution of pyrene with added βCD. The aggregate size as measured by dynamic light scattering was found to have a value of 3.2-3.6 nm. The aggregate was identified as a 1:2 complex of Py with βCD (Py@2βCD) surrounded by two empty βCD molecules. The ratio I3/I1 of intensity I3 of the third vibronic band at ~26,000 cm−1 in the fluorescence spectrum to intensity I1 of the 0-0 transition at ~26,800 cm−1 was used as an analytical characteristic of the fluorescent probe. The value of I3/I1 for Py@2βCD is highly sensitive to the presence of several μM of analyte in aqueous solution, and this value is markedly higher than that for pyrene in solution.