Aggregation of azamethine dyes on hydrated glass surfaces: An evanescent wave-induced fluorescence study

The formation of luminescent aggregates of two pyrazolotriazole azamethine dyes in bulk solutions and at hydrated glass surfaces has been investigated using steady-state and time-resolved fluorescence spectroscopy as well as evanescent wave-induced fluorescence spectroscopy (EWIFS). Bulk measurements of dye A in methylcyclohexane, acetonitrile and dibutyl phthalate show that it exists as a molecular entity with fluorescence decay times in the sub-picosecond regime. However, in methylcyclohexane, dye B forms aggregates that possess fluorescence decay times in the nanosecond regime. Nevertheless, EWIF studies show that both dyes form luminescent aggregates at the interface between hydrated fused silica and methylcyclohexane, and hydrated flint glass (LASF3) and dibutyl phthalate.