Figure 9: Changes of fluorescent spectra (A) and fluorescence decay (C) of 1 (1.0 μM) with the variation of solution viscosity (methanol glycerol system). Relationship of the I516/I427 ratio (B) and fluorescence lifetime (D) with solution viscosity. Upon excitation at 375 nm, the fluorescence lifetime was measured on a Fluo time 200 single-photon counting equipment. Inset in A, colour and fluorescence changes for 10 (1.0 μM) in mixed solvents (methanol-glycerol) with various viscosities under sunlight and a UV lamp (365 nm excitation). Reprinted with permission from reference 30. Copyright (2013) American Chemical Society.