Perturbation mechanism and phase transition of AOT aggregates in the Fe(II)[batho(SO3)2]3 - catalyzed aqueous Belousov-Zhabotinsky reaction

Article abstract of DOI:10.1016/j.cplett.2009.12.050

Surfactant AOT (sodium bis(2-ethylhexyl)sulfosuccinate) was introduced up to 200 mmol L^-1 in the aqueous Belousov-Zhabotinsky (BZ) medium. Both the induction period (IP) and the oscillation period (τ) of the BZ waves decreased significantly, whereas the wave velocity (v) increased with the concentration of AOT. These tendencies were explained in terms of the perturbations to the FKN mechanism through the uptake of Br₂ and BrO₂^· into the hydrophobic core of AOT aggregates. In addition, the structures and the phase transition of AOT aggregates were suggested based on the measurement of surface tension and the correlation analysis of the IP, τ and v values.

Full text of DOI:10.1016/j.cplett.2009.12.050

Chemical Physics Letters 485 (2010) 304–308
Contents lists available at ScienceDirect
Chemical Physics Letters
journal homepage: www.elsevier.com/locate/cplett
Perturbation mechanism and phase transition of AOT aggregates in the
Fe(II)[batho(SO ) ] – catalyzed aqueous Belousov–Zhabotinsky reaction
3
2 3
Rumana A. Jahanca,b, Kosuke Suzuki a,b, Hitoshi Mahara , Satoshi Nishimura , Takashi Iwatsubo ,
a
a
a
b
a,
*
Akiko Kaminaga , Yasuhiko Yamamoto , Tomohiko Yamaguchi
a
National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba 305-8565, Japan
Department of Chemistry, Graduate School of Pure and Applied Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan
Department of Chemistry and Bioscience, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan
b
c
a r t i c l e i n f o
a b s t r a c t
Surfactant AOT (sodium bis(2-ethylhexyl)sulfosuccinate) was introduced up to 200 mmol Lꢀ1 in the
aqueous Belousov–Zhabotinsky (BZ) medium. Both the induction period (IP) and the oscillation period
(s) of the BZ waves decreased significantly, whereas the wave velocity (v) increased with the concentra-
Article history:
Received 1 November 2009
In final form 15 December 2009
Available online 21 December 2009
tion of AOT. These tendencies were explained in terms of the perturbations to the FKN mechanism
ꢁ
through the uptake of Br
2
and BrO2 into the hydrophobic core of AOT aggregates. In addition, the struc-
tures and the phase transition of AOT aggregates were suggested based on the measurement of surface
tension and the correlation analysis of the IP, and values.
s
v
Ó 2009 Elsevier B.V. All rights reserved.
1
. Introduction
been used successfully for constructing the reverse-micelles BZ
systems in octane [17–19]. In an aqueous system, contrarily, it
self-assembles into hydrophobic aggregates that may work as a
pool to accumulate hydrophobic intermediates in the BZ reaction.
It is also noteworthy that AOT in water forms different kinds of
self-assembled structures depending on its concentration [20,21].
Such morphological changes are reasonably expected to affect
the BZ patterns if the hydrophobicity of AOT aggregates becomes
varied with their shape and size.
The Belousov–Zhabotinsky (BZ) reaction is the most famous and
thoroughly studied nonlinear reaction that produces temporal
oscillations and a variety of spatio-temporal patterns in laboratory
experiments [1,2]. These patterns include concentric and spiral
travelling chemical waves and Turing patterns. The BZ reaction
generally represents the catalytic oxidation of an organic substrate
by bromate (BrO ) in the presence of metal catalyst in a strongly
ꢀ
3
acidic aqueous solution, and it is often regarded as a chemical
model of biological pattern dynamics [3,4].
A perturbation given to the system often brings about macro-
scopic changes in the spatio-temporal behaviors of the BZ reaction
In the present work, we vary the concentration of AOT up to
200 mmol L in an aqueous BZ system, and attempt to deduce
the perturbation mechanism of AOT through the experimental re-
ꢀ1
sults on the induction period (IP), the oscillation period ( ), and the
s
[
5]. Light [6–11] and oxygen [12] directly interact with the chem-
velocity normal to the wave front of the BZ patterns (v). In the
ical species in the BZ reaction to inhibit the reaction. Even an addi-
tion of non-reacting chemical species induces effective changes in
the pattern dynamics. For example, self-assembled aggregates of
surfactants have been employed to compartmentalize crucial
intermediates to affect the temporal dynamics of the BZ reaction
present system, the induction period is defined as the time re-
quired for the waves to emerge after mixing all the chemicals. It
is known that the dynamics of BZ patterns is well-described by
the reaction–diffusion mechanism [22], where the diffusion obeys
Fick’s second law and the reaction does the so-called FKN mecha-
nism [23]. We follow the original FKN mechanism but introduce a
slight change in Process A so that the three processes proceed
sequentially with time:
[
13–16]. These perturbation experiments often give us a new in-
sight about the reaction mechanism in addition to the controllabil-
ity of the pattern dynamics.
Here, we investigate the pattern dynamics of an aqueous BZ
system perturbed by introducing a strong surfactant: AOT (sodium
ꢀ
Process Aꢂ: reducing the concentration of Br to produce Br
2
bis(2-ethylhexyl)sulfosuccinate). AOT is composed of an anionic
2
and the necessary amount of autocatalytic species HBrO for
ꢀ
headgroup (—SO ) and two hydrocarbon tails (Fig. 1a), and has
kicking off the next process. In addition to the reactions in the
original Process A of FKN mechanism, the present process
Aꢂincludes the bromination reaction of malonic acid (MA) by
3
Br
2
. This reaction takes place instantaneously to produce bro-
*
Corresponding author. Fax: +81 29 861 6236.
E-mail address: tomo.yamaguchi@aist.go.jp (T. Yamaguchi).
momalonic acid (BrMA).
0
009-2614/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.cplett.2009.12.050

R.A. Jahan et al. / Chemical Physics Letters 485 (2010) 304–308
305
3 2 3
Fig. 1. Chemical structure of (a) AOT (sodium bis(2-ethylhexyl)sulfosuccinate); (b) Fe(II)[bathophen(SO ) ] , abbreviated as bathoferroin in this work.
Process B: autocatalytic production of HBrO
2
by reduction of
The values of s and v of the BZ waves were determined by con-
ꢀ
BrO . Since this autocatalytic step is accompanied by the pro-
structing the space–time diagrams from the sequential images of
travelling waves. Experiments were conducted five times for each
condition.
3
ꢁ
duction of radical BrO , oxidation of metal catalyst takes place
2
by single electron transfer.
Process C: oxidation of MA and BrMA by the oxidized catalyst,
which eventually turns back to its reduced state. This redox
reaction is associated with reproduction of Br .
The values of critical micelles concentration (CMC) of AOT in
pure water and in the BZ solutions were determined by the surface
tension (c) measurements. This was conducted by applying the
ꢀ
Wilhelmy plate method at 24 ± 1 °C using an electro surface bal-
ance (Model ESB-V, Kyowa Scientific Co., Ltd.) equipped with a
platinum plate.
Process Aꢂ determines the IP; Process B is related to the
also a function of diffusion coefficient of HBrO ; Process C is the
most responsible for the oscillation period [24].
v that is
2
s
2
. Experimental
3. Results
Malonic acid (MA), sodium bromate (NaBrO
were of reagent grade purchased from Wako Pure Chem. Ind. Ltd.
Bathoferroin hexasulfonate (Fe(II)[batho(SO ) (Fig. 1b), called
bathoferroin hereafter, were prepared by stoichiometric mixing of
,7-diphenyl-1,10-phenanthroline disulfonic acid sodium salt
Nacalai Tesque Inc.) with ferrous sulfateꢁ7H O (Wako) in 3:1 molar
ratio in water to yield the complex at the concentration of
3
) and sulfuric acid
The replacement of the classical BZ catalyst Fe(II)(phen)
3
(i.e.,
ferroin) by Fe(II)[batho(SO (bathoferroin) [25] proved to be
3 2 3
) ]
3
)
2
]
3
an effective substitution for our experimental system. The major
reason for using bathoferroin instead of ferroin in this work is that
the positively-charged ferroin interacts with the anionic surfactant
to result in the formation of adducts especially at high concentra-
tion of AOT (Fig. 2g). The BZ waves observed were in good contrast
by use of bathoferroin. The wavelength of the BZ patterns became
substantially shorter with increasing concentration of AOT
(Fig. 2a–f).
4
(
2
ꢀ1
2
5 mmol L of the catalyst. Sodium bis(2-ethylhexyl)sulfosucci-
nate (AOT; Sigma–Aldrich) was of the highest purity available and
used without further purification. It was stored sealed by parafilm
in a desiccator since the reagent is highly hygroscopic.
Three characteristic measures of the BZ waves were determined
ꢀ
1
+
ꢀ1
ꢀ1
The BZ solutions ([MA]: 0.25 mol L , [H ]: 0.20 mol L , [NaB-
in the presence of AOT up to 200 mmol L : the induction period IP
ꢀ1
ꢀ1
rO
3
]: 0.18 mol L , [bathoferroin]: 4 mmol L ) were prepared
from the aqueous stock solutions of 2 mol L MA (malonic acid),
(Fig. 3a), the normal velocity of the propagating BZ waves
v
ꢀ
1
(Fig. 3b), and the period of oscillations (Fig. 3c). The results ob-
s
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
5
mol L
2
H SO
4
, 1 mol L NaBrO
3
and 25 mmol L of bathoferro-
tained at low concentrations of AOT (0–25 mmol L ), given as in-
in. An aqueous solution of the anionic surfactant AOT
sets, illustrate that IP decreased only slightly with the
ꢀ1
(
400 mmol L ) was used as a stock solution. Milli-Q doubly dis-
tilled water was used to prepare all the aqueous solutions in the
present work. A fixed volume (30 L) of reaction medium was
concentration of AOT;
v increased slightly, and s decreased gradu-
ally. On the other hand, at high concentrations of AOT
ꢀ1
l
(ꢃ200 mmol L ), sharp decreases were observed in both values
of IP and , whereas the profile of did not show such clear ten-
dency. The present tendency in is different from that reported
placed between two glass plates spaced by 0.8 mm. This uniform
geometrical condition was achieved by using commercially avail-
able glass plates (UR-137-S) purchased from Sekisui Chemicals
Co., Ltd. The experiments were performed at room temperature,
s
v
v
[15] in the case of another anionic surfactant: sodium dodecyl sul-
fate (SDS).
2
4 ± 1 °C.
The CMC value of AOT in the presence of BZ reactants was
ꢀ1
The time evolution of BZ patterns was monitored under micro-
0.68 mmol L (Fig. 4), whereas the value in pure water was ob-
ꢀ
1
scope (Leica WILD MZ8) equipped with a spatially-homogeneous
cold backlight (metal halide lamp, PCS-UMX350, Nippon P.I Co.,
Ltd. with flat light guide PLG-B100X) and a CCD camera (SONY
XC-77, driven by an image controller HAMAMATSU C-2400). The
images were digitized on a PC and processed for further analysis.
tained as 2.3 mmol L . The latter is in good agreement with the
ꢀ1
known value of 2.5 mmol L [21]. The lower value of CMC in the
BZ solution is due to the high ionic strength [26,27]. Further mea-
ꢀ
1
surement at AOT concentration much higher than 60 mmol L
was practically difficult by the present Wilhelmy plate method.

3
06
R.A. Jahan et al. / Chemical Physics Letters 485 (2010) 304–308
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
ꢀ1
Fig. 2. Patterns without (a) and with 25 mmol L (b), 75 mmol L (c), 125 mmol L (d), 150 mmol L (e), and 175 mmol L (f) of AOT in the aqueous BZ system where
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
[
MA] = 0.25 mol L , [H
2 4 3
SO ] = 0.2 mol L , [NaBrO ] = 0.18 mol L , and [bathoferroin] = 4.0 mmol L ; (g) Hairy adducts formed at the interface of waxy AOT in contact with
the BZ reactants containing ferroin. The white bars correspond to 1 mm. Temperature: 24 ± 1 °C.
a
400
b
0.09
0.06
4
3
2
1
00
00
00
00
0
2
00
0
0
10
20
30
-
1
[
AOT] (mmol L
)
0
.06
v
0.03
0
0
.03
0
v
0
10
20
30
-
1
[
AOT] (mmol L )
0
50
100
AOT] (mmol L-1
150
200
0
50
100
[AOT] (mmol L-1
)
150
200
[
)
c
120
150
d
1.2
75
τ
0
8
0
0
0
0
0
.8
0
10
20
30
-
1
[
AOT] (mmol L
)
τ
τ
4
.4
0
0
50
100
150
200
0
0.25
0.5
0.75
1
[
AOT] (mmol L-1
)
φ
(a.u.)
Fig. 3. Influence of AOT concentration on: (a) the induction period IP, (b) the wave velocity
v
, and (c) the oscillation period
expansion of each trend at low concentrations below 25 mmol L . The lines are just for readers’ guide. The profile (d) represents the simulated oscillation period (
reaction as a function of u (a parameter proportional to the volume ratio of the hydrophobic subphase and aqueous phase), where the axes are given in arbitrary units.
s
of the BZ reaction. Each inset in (a)ꢀ(c) shows the
ꢀ
1
s
of the BZ
ꢀ
þ
4
. Discussion
Br þ HOBr þ H ꢀ Br
2
þ H
2
O;
ð1Þ
ð2Þ
2
Br ꢄ AOTðagÞ
þ AOTðagÞ ꢀ Br
2
4.1. Perturbation mechanism of AOT aggregates
The induction period IP is under the control of Process Aꢂ in the
Here AOT(ag) stands for the aggregated phase of AOT. Eq. (2)
ꢀ
FKN mechanism. The major role of Process Aꢂ is to decrease the
accelerates the decreasing rate of Br concentration due to the
mass action law in Eq. (1), and consequently decreases the induc-
tion time. According to this perturbation mechanism, the induction
time decreases almost proportionally to the amount of AOT aggre-
gates. This tendency has been confirmed by numerical calculations
of Process Aꢂ (data not shown).
ꢀ
concentration of inhibitor Br to produce Br
2
, HOBr and HBrO
2
according to the reactions R1 (Eq. (1) below), R2, and R3 in the clas-
sical FKN mechanism [23], respectively. Since Br is highly hydro-
phobic, it is absorbed into the hydrophobic core of AOT aggregates
Eq. (2)).
2
(

R.A. Jahan et al. / Chemical Physics Letters 485 (2010) 304–308
307
3
5
5
4
3
2
0
0
0
Finally, we deal with the change in the wave velocity
tightly related to the autocatalytic Process B. There is a well-known
relation about the velocity of the BZ wave:
v
that is
28
28
00 00
v
p
/ ðkDÞ0:5;
ð7Þ
21
21
3
5
00 00
where
v
p
is the velocity of the planar BZ wave, and v =
v
p
when the
14
4
17.55
0
curvature of the wave front is small enough; k is the rate constant of
the following autocatalytic reaction, and D is the apparent diffusion
coefficient of autocatalytic species [29,30]:
γ
γ
1
00
7
0
2
4
[
AOT] (mmol L-1
)
[
AOT] (mmol L-1
)
ꢀ
þ
ꢈ
HBrO
2
þ BrO þ H ꢀ 2BrO þ H
2
O
ð8Þ
e
3
2
0
0
0
0
10
10
20
20
30
30
40
40
50
50
60
60
Here, k is little influenced by AOT because of the small value of
-
1
[
AOT] (mmol L )
in Eq. (3), whereas D may change with u. As mentioned above, the
ꢁ
autocatalytic species BrO is accumulated in the hydrophobic core
2
Fig. 4. Influence of AOT concentration on surface tension
c (closed circle) and the
ꢀ
1
of AOT aggregates to decrease the values of
simultaneously contributes to lessen the necessary amount of
HBrO that diffuses in front of the oxidative wave to sustain the
wave propagation. Alternatively, the influence of HBrO reaches
s. This accumulation
induction period IP (open circle). Arrows A and B at 0.68 and 6.0 mmol L indicate
the phase transition points in the surface tension (CMC) and the induction period,
respectively. The inset expands the results of surface tension measurement at low
concentrations of AOT.
2
2
to a longer distance by diffusion. In this way, even if the value of
diffusion coefficient remains the same, the apparent value of D
Next, in order to corroborate the effect of the hydrophobic
phase on the oscillation period s, we conduct numerical calcula-
tions of oscillatory medium by using the two-variable Rovinsky–
may increase and result in the linear increase in
of AOT.
v with the amount
Zhabotinsky (RZ) model [28] that is known as a good model for
4.2. Phase transition of AOT aggregates
the ferroin-catalyzed BZ system. After Vanag and Epstein [19],
ꢁ
we include the concentration of hydrophobic intermediate BrO
2
Fig. 4 shows the dependence of the values of the surface tension
and the induction period IP on the concentration of AOT. The
as the third variable s to take the autocatalytic process into account
in the hydrophobic subphase:
c
ꢀ1
wide plateau of the
c values above the CMC (0.68 mmol L ) indi-
ꢃ
ꢀ
ꢁꢂ
dx
dt
dz
dt
ds
z
x ꢀ
l
l
cates that the concentration of free AOT is constant, and above
CMC, the amount of AOT aggregates (spherical micelles) increases
with the increase in AOT. Therefore, one can reasonably say that
the decrease in the IP value is caused by the increase in the concen-
¼
xð1 ꢀ xÞ ꢀ 2q
a
=e
ꢀ k
f
x þ k
b
s;
ð3Þ
1 ꢀ z x þ
z
¼
¼
x ꢀ
a
;
ð4Þ
ð5Þ
1 ꢀ z
tration of AOT micelles, and the change in the slope around
k
f
x ꢀ k
b
s þ / s;
ꢀ1
6
mmol L
suggests the phase transition associated with the
dt
structural change of AOT micelles. As X-ray diffraction analysis re-
vealed no lamellar structures (data not shown), this is most prob-
ably due to the phase transition from spherical micelles to rod-like
3
3
ꢀ
ꢁ
where x = [HBrO
A/k C,
¼ k
2
], z ¼ ½FeðIIIÞ½bathoðSO
3
Þ ꢅ ꢅ, and s = [BrO ];
e
=
],
2
2
2
1
2
2
0
k
1
4
a
4
k
8
B=k A h , and
l
= 2k
4
k
7
/k
1 5 3
k , where A = [HBrO
B = [BrMA], C is the total concentration of catalyst; k (i = 1–8) is
i
micelles [20]. At AOT concentrations much higher than
the rate constant; h
etric factor; k and k
backward reaction of BrO production in an aqueous phase, respec-
0
is the acidity function and q is the stoichiom-
ꢀ1
6
0 mmol L , IP decreases very sharply (Fig. 3a). It suggests the
f
b
are the rate constants of the forward and the
appearance of new phases, which can be depicted by the following
correlation analysis.
ꢁ
2
tively. The influence of AOT aggregate is represented by u, which is
regarded as proportional to the volume ratio of AOT to water. In the
present model, the rate constant of the autocatalytic process is writ-
The correlation between the IP and
s values appears as a mono-
tonically increasing line with two kinks (Fig. 5a). This diagram
illustrates the strong positive correlation between the lengths of
Process Aꢂ and Process C in the FKN mechanism. The tri-phase line
in Fig. 5a suggests the existence of at least three phases in AOT
aggregates that correspond to the concentrations of 0–
ten as k
As shown in Fig. 3d, a decrease similar to the experimental re-
sults in Fig. 3c is observed in the profile of oscillation period . This
1
(see Ref. [28]).
s
good agreement is qualitatively explained as follows. By applica-
tion of the quasi-steady state assumption to Eqs. (3) and (5) in Pro-
ꢀ1
ꢀ1
ꢀ1
6
0 mmol L , 60–100 mmol L and above 100 mmol L . The for-
mer two are also noticeable in Fig. 3a, but the third one becomes
cess C, where x is sufficiently smaller than
reduction rate of oxidized catalyst as a function of z and s:
l
(ꢆ 1), we obtain the
clear from this correlation plots. The linear correlation in 0–
ꢀ1
6
0 mmol L implies only little change in the hydrophobicity of
ꢀ
ꢁ
ꢄ
ꢅ
AOT aggregates, which supports the phase transition from spheri-
dz
dt
z
ꢀ1
ꢀ1
ꢀ
ꢇ
að1 þ 2qÞ
þ
e/s
ð6Þ
cal to rod-like micelles at 6.0 mmol L . Above 100 mmol L , the
BZ medium scattered a laser beam due to the emergence of macro-
scopic AOT aggregates which was visible under optical microscope.
If the size of these macroscopic aggregates becomes large enough,
they may trigger the BZ waves [31,32] to lessen both the values of
1 ꢀ z
C
The first term on the right-hand side arises from the original RZ
model, and the second term from Eq. (5), where us represents the
ꢁ
autocatalytic production of BrO2 in the presence of hydrophobic
subphase. Eq. (6) means that the rate – (dz/dt)
C
increases linearly
IP and
s.
with the value of u, and consequently, the period of Process C de-
creases with u. Since the value of the oscillation period is mainly
The plots of
v against IP appear as a broken line with a negative
slope (Fig. 5b), suggesting the negative correlation between Pro-
determined by the duration time of Process C [24],
with u. In this way, the decrease in the oscillation period is ex-
plained by the increase in the reduction rate of Process C, which
is brought about by the distribution of hydrophobic BrO into
s
decreases
cess B and Process Aꢂ. The disorder in the middle region corre-
ꢀ
1
sponds to the AOT concentration of 60–100 mmol L . As there is
no disorder in the correlation plots between Process Aꢂ and Process
C (Fig. 5a), this disorder is induced something influential only to
the wave velocity. The most probable reason is the increase in
ꢁ
2
AOT aggregates.

3
08
R.A. Jahan et al. / Chemical Physics Letters 485 (2010) 304–308
0.09
0.06
0.03
0
1
20
Low
[AOT]
8
0
0
0
High
4
High
[
AOT]
Low
0
100
200
300
400
0
100
200
300
400
Induction Period (s)
Induction Period (s)
Fig. 5. Correlations: (a) between
s and IP; (b) between v and IP of the BZ–AOT aqueous system. The lines drawn along the points are just for readers’ guide to trail the
existence of phase transitions in the system.
apparent diffusion due to the fluctuation (or disorder) of AOT
aggregates, though little evidence is presently at hand.
Ministry of Education, Culture, Sports, Science and Technology
(MEXT).
In summary, AOT in the present BZ medium seems to exist in
ꢀ
1
five states; free molecules at 0–0.68 mmol L , spherical micelles
References
ꢀ1
ꢀ1
at 0.68–6 mmol L , rod-like micelles at 6–60 mmol L , a tran-
ꢀ
1
[1] A.N. Zaikin, A.M. Zhabotinsky, Nature 225 (1970) 535.
sient disordered state at 60–100 mmol L , and coexistence of
[
2] R. Kapral, K. Showalter, Chemical Waves and Patterns, Kluwer Academic,
Dordrecht, 1995.
ꢀ
1
macroscopic aggregates above 100 mmol L
.
[
[
[
[
3] S. Kondo, R. Asai, Nature 376 (1995) 765.
4] J.D. Lechleiter, L.M. John, P. Camacho, Biophys. Chem. 72 (1998) 123.
5] M. Yoneyama, Chem. Phys. Lett. 254 (1996) 191.
6] F. Bolletta, V. Balzani, J. Am. Chem. Soc. 104 (1984) 4250.
5
. Concluding remarks
Perturbation has been achieved to the aqueous BZ reaction sys-
tem by introducing the anionic surfactant AOT. The values of
induction period IP, oscillation period and wave velocity of
the BZ patterns are changed significantly, and the extent of the
change depends on the amount of AOT. We consider that the over-
all dynamics of the BZ reaction represented by the FKN mechanism
[7] I. Hanazaki, Y. Mori, T. Sekiguchi, G. Rabai, Physica D 84 (1995) 228.
[
[
8] I. Hanazaki, J. Phys. Chem. 96 (13) (1992) 5652.
9] V. Gaspar, G. Bazsa, M. Beck, Z. Phys. Chem. (Leipzig) 264 (1983) 43.
s
v
[
[
[
10] T. Amemiya, S. Kadar, P. Kettunen, K. Showalter, Phys. Rev. Lett. 77 (1996)
3244.
11] R. Toth, V. Gaspar, A. Belmonte, M.C. O’Connell, A. Taylor, S.K. Scott, Phys.
Chem. Chem. Phys. 2 (2000) 413.
12] A.F. Taylor, B.R. Johnson, S.K. Scott, Phys. Chem. Chem. Phys. 1 (1999) 807.
is perturbed mainly through the hydrophobicity of AOT aggregates.
[13] A. Paul, J. Phys. Chem. B 109 (2005) 9639.
[14] L. Sciascia, R. Lombardo, M.L.T. Liveri, J. Phys. Chem. B 111 (2007) 1354.
ꢁ
The aggregates allow the distribution of Br
hydrophobic cores and decrease both IP and
2
and BrO2 into their
values, and increase
[
15] F. Rossi, R. Lombardo, L. Sciascia, C. Sbriziolo, M.L.T. Liveri, J. Phys. Chem. B 112
2008) 7244.
[16] F. Rossi, R. Varsalona, M.L.T. Liveri, Chem. Phys. Lett. 463 (2008) 378.
s
(
the
v value.
[
[
[
17] I.R. Epstein, V.K. Vanag, CHAOS 15 (2005) 047510.
18] A. Kaminaga, V.K. Vanag, I.R. Epstein, J. Chem. Phys. 122 (2005) 174706.
19] V.K. Vanag, I.R. Epstein, Phys. Rev. Lett. 87 (2001) 228301.
As a future study remains the concrete study on the structural
transition of AOT aggregates associated with the change in their
hydrophobicity, which has been suggested phenomenologically
by the correlation analysis (Fig. 5). Electrostatic interaction be-
tween the charged BZ species and the surfactant aggregates may
be another remaining issue to be addressed, though we consider
it less influential than the hydrophobic interaction.
[20] E.Y. Sheu, S.-H. Chen, J.S. Huang, J. Phys. Chem. 91 (1987) 3306.
[
[
[
21] E.F. Williams, N.T. Woodberry, J.K. Dixon, J. Colloid Sci. 12 (1957) 452.
22] J.D. Murray, Mathematical Biology, Springer-Verlag, Berlin, 2002.
23] R.J. Field, E. Koros, R.M. Noyes, J. Am. Chem. Soc. 94 (25) (1972) 8649.
[24] J.J. Tyson, in: R.J. Field, M. Burger (Eds.), Oscillations and Travelling Waves in
Chemical Systems, Wiley-Interscience, New York, 1985, p. 93.
[
25] T. Yamaguchi, L. Kuhnert, Zs. Nagy-Ungvarai, S.C. Müller, B. Hess, J. Phys.
Chem. 95 (1991) 5831.
Acknowledgments
[
[
[
[
[
26] S.S. Rawat, S. Mukherjee, A. Chattopadhyay, J. Phys. Chem. B 101 (1997) 1922.
27] I.M. Umlong, K. Ismail, J. Colloid Interface Sci. 291 (2005) 529.
28] A.B. Rovinsky, A.M. Zhabotinsky, J. Phys. Chem. 88 (1984) 6081.
29] R.J. Field, R.M. Noyes, J. Am. Chem. Soc. 96 (1974) 2001.
30] R. Luther, R. Arnold, K. Showalter, J. Tyson, J. Chem. Educ. 64 (1987) 740.
R.A.J and T.Y. are grateful to Dr. H. Hashimoto for providing the
image processing software, to Dr. D. Kitamoto for assisting the sur-
face tension measurement, and especially to Dr. V.K. Vanag for use-
ful discussions and suggestions. This work was partly supported by
a Grant-in-Aid for Scientific Research on Innovative Areas from the
[31] E. Mori, J. Ross, J. Phys. Chem. 96 (1992) 8053.
32] P. Foerster, S. Müller, B. Hess, Proc. Natl. Acad. Sci. USA 86 (1989) 6831.
[