Photophysics of lumichrome on cellulose

Lumichrome samples were prepared by depositing lumichrome on cellulose from methanol solutions. Diffuse reflectance absorption bands at 354 and 388 nm (shoulder) and the fluorescence band at 460 nm similar to those observed in polar solvents were attributed to a π→π∗ transition. The emission decay has a complex kinetics similar to that found in alloxazines, suggesting at least three emitting species with the respective lifetimes of about 0.95, 1.4 and 2.5 ns. Diffuse reflectance laser flash photolysis experiments provided the decay kinetics of the triplet state with the lifetime on the microsecond time scale and of the longer-lived semi-reduced radical absorbing in the 500–600 nm range with 0.24 ms lifetime.