Time-resolved phosphorescence

Fig. 28. Time-resolved phosphorescence spectra of quinoxaline in durene host observed at 1.38 K and at (a) 30 msec, (b) 450 msec, and (c) 1500 msec after excitation cutoff. The ordinate scale is normalized with respect to the 0 - 0" band. The numbers shown in (c) represent the vibrational frequencies (in wavenumber unit) measured from the 0 - 0" band (21639 cm r). The arrows indicate the bands whose relative intensities are remarkably enhanced at later times after the excitation cutoff. (From Yamauchi and Azumi, Ref. >)...

Time-resolved phosphorescence detection (TRPD) was employed to check the yields obtained with the 1,3-diphenylisobenzofuran (DPBF) bleaching procedure for some oligothiophene (94JPP(A)(83)1). 

Time resolved phosphorescence spectra of vitreous benzophenone... 

Figure 2. Time resolved phosphorescence spectra of PVCA in solution at 77 K using a monochromator band pass of 2 nm. Delay times of 400 msec (upper) and 800 msec (lower) were used.

Further confirmation of this assignment comes from time-resolved phosphorescence measurements. Figure 11.10 shows the phosphorescence decay curves of the PtOEP in MeLPPP, without and with benzil codoped at a concentration of 20 wt.%. In both cases, fast and slow components are observed. The decay time of the fast component agrees with the intrinsic lifetime of the triplet state of PtOEP (70-100 p,s). Obviously, the fast component is due to porphyrin molecules excited as a result of the singlet-singlet energy transfer from the polymer. 

Fluorescence applied to oil identification has been an active field, with 17 papers presented on the subject at the last three Pittsburgh Conferences. A number of interesting developments for fluorescence and low-temperature luminescence (LTL) are described by Eastwood et al. (58). These include synchronous scanning, difference spectrofluorometry, synchronous difference spectroscopy, derivative spectroscopy, and total luminescence (or contour) spectroscopy and combinations of these techniques. In a recent presentation, Eastwood and Hendrick (59) reported an extension of their low-temperature luminescence studies to include polarized excitation and emission spectroscopy, and time-resolved phosphorescence. Preliminary studies of polarization effects indicate that differences exist in low-temperature polarized luminescence spectra of oils, which may aid in oil identification. In the time-resolved phosphorescence spectra of oils, the most significant difference observed was enhancement of the vanadyl porphyrin signal at approximately 700 nm for short delay times (20 fxsec). 

For example, the Agilent Cary Eclipse spectrophotometer is a versatile instrument that allows fluorescence, phosphorescence, chemiluminescence, bioluminescence, and time-resolved phosphorescence measurements. It uses a xenon flash lamp, red-sensitive PMT, captures a data point every... 

In Section 2.5 we described the use of time-resolved fluorescence anisotropy for monitoring protein motion on the nanosecond timescale. For motion on much longer timescales, time-resolved phosphorescence anisotropy can be used instead. The latter technique has been employed, for example, to examine the rotational motion of membrane-boimd proteins labelled with the triplet probe eosin (57, 58). Prior to making the measurements, the protein is labelled with eosine-maleimide as described in Protocol 2. 

Eosine labelling of proteins for time-resolved phosphorescence measurements... 

Time resolved phosphorescence of PAcN (At = 0, 1.0, 3.0 sec), P2VN ( At = 0, 0.5, 1.0 sec) plus biacetyl (left) (from ref. C.3, Table 2) and PVCz plus biacetyl (right) (from ref. f. Table 2), with time increments indicated (bottom-most spectrum is for At = 0). 

Lettinga MP, van Kats CM, Philipse AP (2000) Rotational diffusion of tracer spheres in packings and dispersions of colloidal spheres studied with time-resolved phosphorescence anisotropy. Langmuir 16 6166-6172... 

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