190
S. Cerveny and J. Swenson
3
4
5
6
7
8
-14
-12
-10
-8
-6
-4
-2
0
2
3
4
5
6
7
8
-14
-12
-10
-8
-6
-4
-2
0
2
BDS-MCM-41
NMR-MCM-41
log (τ [s])
1000/T [K
-1
]
(a)
water
(b)
Water in MCM-41 and SBA-15
log (τ [s])
1000/T [K
-1
]
ice
Fig. 18 a Temperature dependence of relaxation times determined from BDS [54] and NMR[33]
of amorphous water confined in MCM-41 of the same pore diameter. b Temperature dependence
of relaxation times for partially crystallized water confined in MCM-41 of different sizes. The two
lines represent the results of the experiment on D 2 O in MCM-41 with various pore diameters (2.1–
6 nm). The fast relaxation represents the rotational motion of confined water (orange line) whereas
the slow relaxation (grey line) represents the relaxation times of the ice phase
The dynamics of amorphous water confined in MCM-41 has been studied by both
BDS [54, 55] and nuclear magnetic resonance [31, 32, 56] (NMR). The relaxation
times of water exhibit a dynamic crossover at about 180 K, similar to that previously
discussed for water solutions in Sect. 5 (see Fig. 18a).
If the pore diameter is ~2 nm or smaller, water remains amorphous for all temperatures. However, using a wider pore, a fraction of water crystallizes, as in the case of
the water solutions analyzed in Sect. 2. Weigler et al. [33] explore the dynamics of
water confined in MCM-41 of different sizes from 2.1 to 3.3 nm. The calorimetric
response showed that crystallization of water confined in 2.1 nm is fully suppressed,
but water confined in pore sizes of 3.3, 2.8 and even in 2.4 nm present crystallization
on the cooling cycle. Increasing the pore size, a more pronounced freezing peak is
shown and therefore more ice is produced in each sample. Thus, by increasing the
pore size, it is possible to study the dynamics of amorphous water in samples of
an increasing amount of ice. In particular, it was of interest [32, 33] to elucidate
whether the dynamic crossover of the confined supercooled water is affected by
crystallization.
The dynamics of such partially crystallized D 2 O confined in MCM-41 of different
pore sizes has been studied by 2H SLR and STE experiments. Figure 18b shows the
relaxation times for these samples of different pore sizes and different levels of ice.
As can be seen in the figure, the relaxation time is basically independent of the pore
size and the level of crystallization. This result contrasts that previously obtained in
ordinary solutions, as discussed in Sect. 6, but is similar to what was observed for
S. Cerveny and J. Swenson
3
4
5
6
7
8
-14
-12
-10
-8
-6
-4
-2
0
2
3
4
5
6
7
8
-14
-12
-10
-8
-6
-4
-2
0
2
BDS-MCM-41
NMR-MCM-41
log (τ [s])
1000/T [K
-1
]
(a)
water
(b)
Water in MCM-41 and SBA-15
log (τ [s])
1000/T [K
-1
]
ice
Fig. 18 a Temperature dependence of relaxation times determined from BDS [54] and NMR[33]
of amorphous water confined in MCM-41 of the same pore diameter. b Temperature dependence
of relaxation times for partially crystallized water confined in MCM-41 of different sizes. The two
lines represent the results of the experiment on D 2 O in MCM-41 with various pore diameters (2.1–
6 nm). The fast relaxation represents the rotational motion of confined water (orange line) whereas
the slow relaxation (grey line) represents the relaxation times of the ice phase
The dynamics of amorphous water confined in MCM-41 has been studied by both
BDS [54, 55] and nuclear magnetic resonance [31, 32, 56] (NMR). The relaxation
times of water exhibit a dynamic crossover at about 180 K, similar to that previously
discussed for water solutions in Sect. 5 (see Fig. 18a).
If the pore diameter is ~2 nm or smaller, water remains amorphous for all temperatures. However, using a wider pore, a fraction of water crystallizes, as in the case of
the water solutions analyzed in Sect. 2. Weigler et al. [33] explore the dynamics of
water confined in MCM-41 of different sizes from 2.1 to 3.3 nm. The calorimetric
response showed that crystallization of water confined in 2.1 nm is fully suppressed,
but water confined in pore sizes of 3.3, 2.8 and even in 2.4 nm present crystallization
on the cooling cycle. Increasing the pore size, a more pronounced freezing peak is
shown and therefore more ice is produced in each sample. Thus, by increasing the
pore size, it is possible to study the dynamics of amorphous water in samples of
an increasing amount of ice. In particular, it was of interest [32, 33] to elucidate
whether the dynamic crossover of the confined supercooled water is affected by
crystallization.
The dynamics of such partially crystallized D 2 O confined in MCM-41 of different
pore sizes has been studied by 2H SLR and STE experiments. Figure 18b shows the
relaxation times for these samples of different pore sizes and different levels of ice.
As can be seen in the figure, the relaxation time is basically independent of the pore
size and the level of crystallization. This result contrasts that previously obtained in
ordinary solutions, as discussed in Sect. 6, but is similar to what was observed for