STUDY ON THE PHOTODEGRADATION MECHANISM OF CYANINE DYES AND MEROCYANINE DYES SOLUTION

The photodegradation kinetics of cyanine dyes and merocyanine dyes were studied by UV Vis absorption spectroscopy. The results show that the rate of the photofading reactions of the dyes follow quasi first order or zero order kinetics in acetonitrile. The main photodegradation products of the dyes were identified by GC/MS spectrometry. Those cyanine dyes holding a positive charge have relative good photostability comparing with merocyanines. The experimental results imply that the photodegradation intermediates for the cyanine dyes may be the semi oxide state of dye, Dye +. The transient absorption spectra of Dye + were measured by nanosecond laser flash photolysis.