THE PHOTOPHYSICAL CONSTANTS OF SEVERAL FLUORESCENT DYES PERTAINING TOULTRASENSITIVE FLUORESCENCE SPECTROSCOPY

The successful implementation of ultrasensitive fluorescence spectrosc opy of biological and chemical species depends upon certain photophysi cal parameters associated with the fluorescent dye used in the investi gation. These parameters include the fluorescence quantum efficiency, photodestruction quantum efficiency, absorption cross section and fluo rescence lifetime. These photophysical constants were measured for sev eral fluorescent dyes that are used for the tagging of biological spec ies. Three different solvents, ethanol, water and a cationic surfactan t used above its critical micelle concentration, were studied. The eff ective photon yield (ratio of the fluorescence quantum yield to the ph otodestruction quantum efficiency) for the dyes is nearly 100 times gr eater in ethanol than it is in water because of the superior photostab ilities of these dyes in ethanol solvents. The implications of these p arameters for the design of an ultrasensitive fluorescence experiment are discussed.