Horiba Scientific Quanta-phi F-3029, Operation Manual

Page: 18 / 98

Quanta-
φ
rev. C (23 Apr 2010) Theory of Operation
1-4
Caution:
Always attenuate or adjust the signal intensities to prevent satu-
ration of the detector. Saturated signals can seriously deteriorate the
measurement precision and accuracy, and possibly damage the detec-
tion electronics.
where L
b
is the integrated excitation profile when the sample is diffusely illuminated by
the integrating sphere’s surface; and L
c
is the integrated excitation profile when the
sample is directly excited by the incident beam.
The quantum yield,
υ
, is, by definition, photons emitted to photons absorbed:
 
1
c b
c a
a a c
E A E
E E
L A L L

  

 
 
(8)
where
E
c
is the integrated luminescence of the film caused by direct excitation, and E
b
is the integrated luminescence of the film caused by indirect illumination from the
sphere. The term
L
a
is the integrated excitation profile from an empty integrating sphere
(without the sample, only a blank). Here E
a
is the integrated luminescence from an
empty integrating sphere (only a blank).
For integration of function
L over the wavelength,
λ
, the integration limits can be from
10 nm below the excitation wavelength to 10 nm above the excitation wavelength.
The spectra recorded must be background corrected, using a blank sample holder, and
corrected for wavelength dependence of the spectrofluorometer, sampling optics, and
integrating sphere.
Example
An example is given for rhodamine 101 (see right) in anhydrous ethanol (with a peak
absorbance value of OD = 0.063 at 563 nm) excited
using 545-nm light (OD = 0.035) using 1 nm bandpass
for both excitation and emission.
Using a CCD detector, the scattered 545 nm excitation spectra were recorded for both
the blank cuvette containing only ethanol (red,
L
a
), and the sample cuvette (black, L
c
).
Integration of the instrument-corrected incident beam’s signal intensities I was per-
formed from 535 to 553 nm for 0.5 s (20 summed accumulations).