Photostability of pyrromethene 567 laser dye solutions via photoluminescence measurements

摘要

The effects of antioxidant addition and concentration on the photostability of methanol solutions of the pyrro-methene laser dye 1,3,5,7,8,-pentamethyl-2,6-diethylpyrromethene-difluoroborate complex (PM-567) were investigated. Specifically, methanol solutions of PM-567 were irradiated with 532 nm Nd:YAG laser pulses (2nd harmonic), and the photoluminescence measured as a function of accumulated laser pulses. The decrease in the photoluminescence-to-initial photoluminescence ratio with accumulated laser pulses was measure as a function of antioxidant addition and dye concentration. The addition of antioxidants, 1,4-diazabicyclo[2.2.2] octane (DABCO) and sodium azide (NaN_3), resulted in dramatic enhancement of photostability, whereas only nominal enhancement was observed upon n-propyl gallate addition. Over the concentration range 6 X 10~5 to 5 X 10~4 M, dye-photostability was virtually concentration independent, with only a small enhancement at lower concentrations. The normalized photostability, the half-life of accumulated energy per mole of dye, could not explain the concentration dependence of photostability. Reasons why the normalized photostability fails to explain the concentration trends are discussed.