Horiba Scientific Quanta-phi F-3029, Operation Manual

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Quanta-
φ
rev. C (23 Apr 2010) Theory of Operation
1-8
will be directly related to the measured

values. For samples with high quantum
yields (like rhodamine 101), however, or with large Stokes shifts between excita-
tion and emission spectra (like quinine sulfate), re-absorbance effects are signifi-
cantly smaller.
The following figures provide examples how increasing concentration and absorbance
affect emission spectra of rhodamine 101 in anhydrous ethanol, and quinine sulfate in
0.1
N H
2
SO
4
, as measured in the Quanta-
υ
. The top plots (A) for both figures exhibit
the normalized excitation (black) and emission (red) spectra to illustrate the overlap-
ping regions responsible for self-absorption. Clearly the overlap is much larger in rho-
damine 101 than in quinine sulfate. The middle plots (B) show the normalized emission
spectra at particular ODs, revealing self-absorption. Again, the rhodamine 101 spectra
are systematically red-shifted as OD increases (from self-absorption). Qunine sulfate,
however, shows little or no change in the emission spectrum as the OD changes. The
lower plots (C) reinforce the visual observations in plots A and B, by showing the rela-
tive area. Integrals decrease as OD rises for rhodamine 101, but there is no change in
quinine sulfate.
Influence of OD on fluorescence emission of rhodamine 101 dissolved in anhydrous
ethanol.