Selective Formation of a Novel Dequenched Aggregates of Rhodamines: Comparison with J- and H-Aggregates

Abstract

Self-organized rhodamine aggregates prepared by wetting/dewetting process of an ethanol solution on a hydrophilic glass surface consistently exhibited fluorescence without quenching. Upon annealing, the aggregates exhibited an irreversible transition to quenched state, like H-aggregate, whereas the fluorescence spectrum was unchanged. The as grown fluorescent aggregate is a novel aggregate, neither a J-aggregate nor an H-aggregate, showing a blue-shifted excitation spectrum whereas the emission spectrum is similar to that of molecularly dispersed solution. This fluorescent aggregate was only realized in nonequilibrium by the rapid dewetting process.