Steady State and Time Resolved Fluorescence Studies of Azadioxatriangulenium (ADOTA) Fluorophore in Silica and PVA Thin Films.

A cationic azadioxatriangulenium (ADOTA) dye was entrapped in silica thin films obtained by the sol-gel process and in poly (vinyl) alcohol (PVA) thin films. Azadioxatriangulenium is a red emitting fluorophore with a long fluorescence lifetime of ~20 ns. The fluorescent properties of azadioxatriangulenium in silica thin films and PVA films were studied by means of steady-state and time resolved fluorescence techniques. We have found that the azadioxatriangulenium entrapped in silica thin film has a wider fluorescence lifetime distribution (Lorentzian distribution), lower fluorescence efficiencies, shorter lifetimes compared to Azadioxatriangulenium in a PVA film. The local environment of azadioxatriangulenium molecules in the silica thin film is rich with water and ethanol, which creates the possibility of forming excited state aggregates due to high concentration of dye within a small confined area. In contrast to the PVA matrices, the porous silica films allow restricted rotations of Azadioxatriangulenium molecules, which result in faster and complex fluorescence anisotropy decays suggesting energy migration among dye molecules.