Emission factors saturation concentration

Figure 9-9. (A) Fluorescence emission spectra of 7-azaindole (7AI) in different solvents acetonitrile ( - ), diethyl ether (A-A), -propanol (0-0), water-saturated diethyl ether (A-A), and deionized water ( - ). The emission of 7AI in -propanol is multiplied by 20-fold. Inset, fluorescence spectra of 7AI in diethyl ether (A-A) and water-saturated diethyl ether (A-A) expanded by a factor of 80 to show the growth of the second band at -520 nm in organic-water solution. All spectra were recorded at 25°C and 2- xM 7AI, by exciting the samples at 280nm. (B) Consensus scheme explaining the emission properties of 7AI in alcohol (R = alkyl) or water solution (R = -H). The polyhydrated species in water are more populated and emit radiation at 400nm. In water-restricted environments (e.g., water-saturated diethyl ether), the concentration of the normal monohydrated species increases, and upon excitation, it is converted into the tautomer form, which is responsible for the longer wavelength emission at -520 nm (Inset to panel A) [90].

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