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PHTHALOCYANINE FLUORESCENCE AT HIGH CONCENTRATION: DIMERS OR REABSORPTION EFFECT?
Author(s) -
Dhami S.,
Mello A. J. De,
Rumbles G.,
Bishop S. M.,
Phillips D.,
Beeby A.
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb08619.x
Subject(s) - fluorescence , photochemistry , phthalocyanine , dimer , chemistry , absorption spectroscopy , absorption (acoustics) , emission spectrum , spectroscopy , fluorescence spectroscopy , analytical chemistry (journal) , reabsorption , spectral line , materials science , sodium , optics , organic chemistry , physics , quantum mechanics , astronomy , composite material
— For tetrasulfonated aluminum phthalocyanine (AlPcS 4 ), dimer formation is characterized in the absorption spectrum by a broadening of the Q‐band and the appearance of a new band at the red edge of the spectrum. The high concentrations required to produce dimers, however, often leads to anomalous observations in fluorescence spectroscopy. In the present study, we have examined the photophysical characteristics of two dye systems; AlPcS 4 in a 66% ethanol/water mixture and disulfonated aluminum phthalocyanine in methanol. Using absorption spectroscopy, the formation of dimers is shown to be prevalent only in the case of AlPcS 4 . The fluorescence emission spectra in both cases, however, exhibit similar spectral changes with increasing dye concentration. The measured fluorescence decay profiles for both dyes also show similar trends: They are monoexponential, invariant with emission wavelength and have decay times that increase with dye concentration. These distortions are sometimes incorrectly attributed to dimer fluorescence. We find no evidence for the existence of dimer fluorescence and demonstrate that these data can be readily explained, by taking into consideration the effects of reabsorption of fluorescence.