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a function of quencher concentration [
Q
] was carried out by the
Stern-Volmer equation as follows:
I
/
I =
1
+
K
[
Q
]
0
SV
where
are the intensities of fluorescence in the absence and
in the presence of the quencher, respectively. The equation reveals
that
I
and
I
0
increase in direct proportion to the concentration of the
quencher.
I
/
I
0
K
is the Stern-Volmer constant.
SV
The Stern-Volmer constant (
K
) in this case was calculated to be
SV
4
-1
1.32 × 10
M
(Fig. 9.20).
Figure 9.20
Stern-Volmer plot for the titration of
12
with TNT (1.0
×
10
-6
M) in CHCl
.
3
9.4.2
Nitroaromatic Sensing by the Supramolecular
Prisms
In the assemblies
Pt-ethynyl functionality was
introduced to make the assemblies fluorescent and
17
,
18
,
21
, and
23
-electron rich.
The open space in the large cages are suitable to accommodate
electron-deficient small nitroaromatic compounds, and also the
bulky PEt
π
groups help to avoid intermolecular stacking and
thus prevent the chance of self-quenching of fluorescence. The
fluorescence of supramolecular prism
3
at 546 nm was quenched
by the trinitrotoluene (TNT) solution (Fig. 9.21). From the plot of
normalized fluorescence intensity (
17
I
/
I
) as a function of increasing
0
quencher concentration ([
]), a linear fit was obtained, which was
thus well described by the Stern-Volmer equation
Q
].
Linear Stern-Volmer behavior was consistent with the quenching
that is dominated by a dynamic process. The Stern-Volmer constant
I
/
I
= 1 +
K
[
Q
0
SV
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