Chemistry Reference
In-Depth Information
35
000
30
000
25
000
20
000
15
000
10
000
5000
0
2
4
6
8
10
12
Number of carbon in perfluoroalkyl chain
Figure 15.14 Variation of fluorescence intensity of rhodamine B in silylated GO containing
n-hexadecylamine as a function of perluoroalkyl chain length. The n-hexadecylamine/GO unit
ratio was 3.0. (unpublished data)
15.3.3
Photochemical Properties
The photochemical dimerization behaviour of acenaphthylene included in perfluoroalk-
ylamine-intercalated graphite oxide has been investigated in comparison with that in
intercalation compounds without perfluoroalkyl groups [85, 86]. Upon UV irradiation
(high pressure UV lamp, l
>
340 nm), two types of dimers of acenaphthylene as shown in
Figure 15.15 can be formed in the film of intercalation compound. It has been reported that
more than 95 % and about 50 % of acenahthylene molecules in the singlet and triplet
excited states, respectively provide syn-isomer [87, 88]. As the result, syn/anti ratios of the
dimers are more than 19 and about 1 when they are exclusively formed from the singlet and
triplet excited states, respectively. In octylamine-intercalated graphite oxide without
perfluoroalkyl groups, the syn/anti ratio increased with the increase of the amount of
included acenaphthylene and reached 9 [84]. As the increase of the alkyl chain length of
alkyl amines, the syn/anti ratio decreased. At high concentrations, the distance between
adjacent acenaphthylene molecules decreases, therefore, excited acenaphthylene mole-
cules readily react with the adjacent molecule before converting to the triplet state. When
the alkyl chain length becomes shorter a similar effect is expected. On the other hand, in
(C
7
F
15
CH
2
NH
2
)
0.38
GO with short perfluorolaky chains, the syn/anti ratio was only 1.2
h
ν
+
λ
> 340 nm
2
acenaphthylene
syn-dimer
anti-dimer
Figure 15.15 Photochemical dimerization of acenaphthylene
