DELAYED FLUORESCENCE OF NAPHTHALOCYANINES SENSITIZED BY SINGLET OXYGEN - TIME-RESOLVED SPECTRAL MEASUREMENTS WITH LASER EXCITATION

Sensitization of the delayed fluorescence of naphthalocyanines [tetra( 6-tert-butyl)-2,3-naphthalocyanine (TBNC) and bis(tri-n-hexylsiloxy)de rivative of silicon-2,3-naphthalocyanine (SNC)I and tetra(4-tert-butyl )phthalocyaninc (TBPC) by singlet oxygen was studied in aerated hexafl uorobenzene using instruments with laser Bash excitation and time-reso lved multichannel photon counting. It was shown that two molecules of singlet oxygen participate in the excitation event of dye molecules. A t a laser excitation energy fluence of 0.6 mJ/cm(2) and naphthalocyani ne and phthalocyanine concentrations of 5 x 10(-8) mol/l, the relative initial intensity of the emission was 1, 1.6, 7.2, and 0.45 for the d elayed fluorescence of TBPC, SNC, TBNC, and 1270-nm phosphorescence, r espectively, The ratio of the delayed fluorescence intensity of the dy es to the phosphorescence intensity of singlet oxygen increased propor tionally to laser excitation energy fluence and dye concentration. It was concluded that the measurement of the naphthalocyanine delayed flu orescence can be used as a very sensitive photophysical method of sing let oxygen detection in solutions, the naphthalocyanines being more ef ficient emitters of this radiation than the phthalocyanine.