Table 2. Fluorescence lifetime data for coumarin dyes in different mediaa

 

 Dye

medium

t(ns)

kf 108 s-1

knrad, 108 s-1

1

30% EtOH

2.4

2.17

2.00

 

30% EtOH (H+)b

0.5

5.21

15.6

 

PMAA (H+)c

3.9

0.85

1.72

2

30% EtOH

1.3

1.92

5.77

 

30% EtOH (H+)b

0.3

3.94

26.4

 

PMAA (H+)c

3.9

1.10

1.46

3

30% EtOH

2.1

1.67

3.10

 

30% EtOH (H+)b

0.4

2.44

22.0

 

PMAA (H+)c

3.6

1.61

1.17

 

a[dye] = 5.0 mM; lexc = 450 nm (1); 430 nm (2); 460 nm (3)

b30 % (v/v) EtOH in H2O with 1.7 M trifluoroacetic acid (TFA).

cPMAA in H2O, pH 3.0; R/D 1000.