DODCI molecules incorporated in sol–gel glasses: the interaction with the silica matrix

The optical properties of the dye DODCI (3,3′-diethyloxadicarbocyanine iodide) incorporated in sol–gel silica-glass matrices have been investigated with regard to interaction with the surrounding silica cage. The absorption and emission spectra have been measured in silica-glass samples with different pore sizes and compared with the spectra obtained in liquid solutions that simulate different environments for the dye molecule. Measurements of a DODCI-derivative molecular structure have been performed by NMR spectroscopy in dimethyl sulfoxide. The results suggest that new electronic states are produced in the trapped molecule, for glass-pore sizes in the range of 2.5–3.5 nm, as a result of the attack of Si–O− groups on the conjugate chain and the protonation to the dicationic form.