Spectral properties of single BODIPY dyes in polystyrene microspheres and in solutions

The absorption, fluorescence, fluorescence quantum yield, and photostabilit y of five BODIPY dyes are characterized and compared as single dyes in two environments, in 40-nm polystyrene spheres and in solution. The absorption and fluorescence spectra of the dyes in spheres are similar in profile but shifted to lower energies compared to those in solution. All the dyes are h ighly fluorescent, with three having fluorescence quantum yields of 1.0. Fo r three of the five dyes, the yields were the same in spheres as in solutio n (1.00, 1.00, and 0.73). The high concentration of these dyes in spheres d oes not quench their fluorescence. For two other dyes the yields dropped, f rom 1.00 to 0.55 in one case and 0.83 to 0.50 in another, comparing the dye s in solution versus in spheres. The photodegradation of the dyes decreases in spheres compared to in solution in all but one case. For one dye, it de creases as much as 800-fold. Dyes overlooked because of low fluorescence or stability in solution could become useful fluorescent materials in the mic rosphere environment.