Biology Reference
In-Depth Information
-6
M solution in DMF was titrated
with a TNT solution (Fig. 9.23) and showed quenching of the
fluorescence intensity. The Stern-Volmer plot (Fig. 9.23) gave a
quenching constant of
In case of prism
23
, a 3
×
10
±
-1
K
= 13.04
0.62 M
.
SV
Figure 9.23
Fluorescence quenching of
23
by TNT (left) and Stern-
Volmer plot (right).
TNT absorbs irradiation below 300 nm. However, the emissions
of the supramolecules
are far above 350 nm. The
lack of overlap between the emission of supramolecular cages and
the absorption of TNT ruled out the possibility of energy transfer
from the excited cages to the explosives quencher. Hence the
observed fluorescence quenching in the present study is presumably
due to the photoinduced electron transfer from the excited state of
the cages to the ground state of the TNT. This facile electron transfer
was expected owing to the strong oxidation potential of TNT and the
presence of conjugated labile
17
,
18
,
21
,
and
23
π
-electrons in the fluorophores.
9.4.3
TNT Vapor Quenches the Fluorescence of
Compound 21 in Solid State
A thin film of the prism
21
was made by spin coating a solution of 3
×
quartz plate. The fluorescence response of
this film to the vapor of TNT was ascertained by inserting the film in
a sealed vial containing solid TNT and cotton gauze separating the
film from direct contact with the TNT. The film was exposed to the
vapor of TNT and the fluorescence was quenched gradually and 80%
quenching was found after 8 min exposure [24].
10
-5
M in DMF on 1 cm
2
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