Light-Responsive, Reversible Emulsification and Demulsification of Oil-in-Water Pickering Emulsions for Catalysis

Article abstract of DOI:10.1002/anie.202010750

Pickering emulsions are an excellent platform for interfacial catalysis. However, developing simple and efficient strategies to achieve product separation and catalyst and emulsifier recovery is still a challenge. Herein, we report the reversible transition between emulsification and demulsification of a light-responsive Pickering emulsion, triggered by alternating between UV and visible light irradiation. The Pickering emulsion is fabricated from Pd-supported silica nanoparticles, azobenzene ionic liquid surfactant, n-octane, and water. This phase behavior is attributed to the adsorption of azobenzene ionic liquid surfactant on the surface of the nanoparticles and the light-responsive activity of ionic liquid surfactant. The Pickering emulsion can be used as a microreactor that enables catalytic reaction, product separation as well as emulsifier and catalyst recycling. Catalytic hydrogenation of unsaturated hydrocarbons at room temperature and atmospheric pressure has been performed in this system to demonstrate product separation and emulsifier and catalyst re-use.

Full text of DOI:10.1002/anie.202010750

A Journal of the Gesellschaft Deutscher Chemiker
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International Edition Chemie
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Accepted Article
Title: Light-switched reversible emulsification and demulsification of oil-
in-water Pickering emulsions
Authors: Zhiyong Li, Yunlei Shi, Anlian Zhu, Yuling Zhao, Huiyong
Wang, Bernard P. Binks, and Jian Wang
This manuscript has been accepted after peer review and appears as an
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202010750
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COMMUNICATION
Light-switched reversible emulsification and demulsification of
oil-in-water Pickering emulsions
[a]
[a]
[a]
[a]
[a]
[b],
Zhiyong Li, Yunlei Shi, Anlian Zhu, Yuling Zhao, Huiyong Wang, Bernard P. Binks * and Jianji
[
a],
Wang *
Abstract: Pickering emulsions have been shown to be an excellent
platform for interfacial catalysis. However, developing simple and
efficient strategies to achieve the goal of product separation and
catalyst and emulsifier recovery is still a challenge. Herein, we report
for the first time the switchable transition between emulsification and
demulsification triggered by UV and visible light in a novel class of
light-responsive Pickering emulsions fabricated from Pd supported
silica nanoparticles, azobenzene ionic liquid surfactant, n-octane and
water. It is shown that light-switchable emulsification and
demulsification of the Pickering emulsions is attributed to the
adsorption of azobenzene ionic liquid surfactant on the surface of the
nanoparticles and the light switched surface activity of the ionic liquid
surfactant. This feature enables the Pickering emulsion to be used as
an easily controlled micro-reactor with the functions of catalytic
reaction, product separation as well as emulsifier and catalyst
recycling. As an example, highly efficient catalytic hydrogenation of
some unsaturated hydrocarbons at room temperature and
atmospheric pressure has been performed in this system, with
product separation and emulsifier and catalyst re-use achievable in a
simple way.
been widely used in the separation of catalysts from reaction
systems, they are challenging when the catalyst particle size is
sub-micrometer. Catalyst loss, filter blocking, long time and high
energy consumption are inevitable, and there is a risk of oxidation
in catalyst transport.[8] Moreover, product separation and
emulsion recycling are still a problem. Thus, these methods
cannot meet the principles of green chemistry and a sustainable
process. To solve these problems, it is necessary to develop new
strategies which can be used to integrate chemical reaction,
product separation, catalyst recovery and emulsion recycling into
a sustainable process.
In recent years, much effort has been made to develop stimuli-
responsive Pickering emulsions and great progress has been
achieved in this area. Generally, temperature , CO
2
bubbling[10],
[
9]
pH[
8b, 11]
, magnetic field[12], redox[13], ionic strength[14], light
irradiation[ or their combinations
15]
[16]
can be used to tune and
control the microstructure and stability of Pickering emulsions.
Therefore, stimuli-responsive Pickering emulsions are capable of
on-demand demulsification or phase inversion (change in
emulsion type)[ , which facilitates catalyst recovery. However, if
product separation, catalyst recovery and emulsion recycling are
simultaneously required, the stimulus response must be
reversible so as to switch between emulsification and
demulsification or between oil-in-water (O/W) and water-in-oil
17]
Pickering emulsions stabilized by colloid particles of suitable
wettability[1] have been known for more than a century[2].
Compared with conventional emulsions stabilized by surfactant or
polymer, Pickering emulsions possess many advantages such as
better stability against coalescence, biological compatibility and
environmental friendliness, and have proven to be useful
alternatives to conventional emulsions in food, pharmaceuticals,
(W/O) emulsion types.
Of the triggers mentioned above, light has clean and non-
invasive characteristics and can be delivered remotely and
[18]
precisely in time and space . Some valuable work has been
reported on light-responsive Pickering emulsions in recent years.
In this context, a light-responsive Pickering emulsion stabilized by
[
3]
emulsion polymerization, drug delivery and cosmetics . Due to
the unique interfacial properties, Pickering emulsions have also
been successfully applied in various interfacial catalytic reactions
in recent years.[4]
titania nanoparticles with tailored wettability was reported by Bai
[15a]
et al.
Demulsification was observed under UV light irradiation
[15b]
but the light response was not reversible. Chen et al.
used
Frequently, Pickering emulsions are ultra-stable as their oil-
water interfaces contain a dense layer of particles,[5] which is
critical for their stability. However, this feature is not conducive to
their demulsification for catalyst recovery and product separation
after the reaction, and this obstacle has not been solved
satisfactorily so far.[6] In general, centrifugation and filtration are
common methods to destroy a stable Pickering emulsion in a
continuous reaction process.[7] Although these methods have
Stenhouse adduct-functionalized silica to prepare photo-
responsive Pickering emulsions capable of phase inversion upon
visible light irradiation. By tuning the hydrophobicity of the
functionalised silica particles with visible light, phase inversion
was easily achieved from W/O to O/W. However, an irreversible
transition was also observed in this system[15b]. Chen et al.[15c]
designed and prepared functional nanoparticles grafted with
photochromic spiropyrans, and used them to achieve reversible
phase inversion of a light-triggered Pickering emulsion for
biphasic enantioselective biocatalysis. Interestingly, based on the
reversible phase inversion of the Pickering emulsion, product
separation and catalyst and emulsifier recycling was
simultaneously realized. This is a significant progress in the
sustainable chemical process mentioned above. However, no
light switched reversible emulsification and demulsification of
Pickering emulsions has been reported so far.
[
a]
Dr. Z. Li, Dr. Y. Shi, Dr. A. Zhu, Dr. Y. Zhao, Dr. H. Wang, Prof. J.
Wang
Collaborative Innovation Center of Henan Province for Green
Manufacturing of Fine Chemicals, Key Laboratory of Green
Chemical Media and Reactions, Ministry of Education, School of
Chemistry and Chemical Engineering, Henan Normal University,
Xinxiang, Henan 453007, P.R. China
E-mail: jwang@htu.cn
[
b]
Prof. B.P. Binks
Herein, for the first time, we report on the switchable transition
between emulsification and demulsification triggered by UV and
visible light in a novel class of light-responsive Pickering
Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
E-mail: b.p.binks@hull.ac.uk
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Angewandte Chemie International Edition
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COMMUNICATION
emulsions stabilized by silica microspheres (SM) functionalized
with surface-loaded metal Pd (Pd@SM) and water-soluble
form
a
stable Pickering emulsion within the investigated
concentration range (Pd@SM 0.0001-0.5 wt.%, Figure S5). The
air-water contact angle on Pd@SM was determined to be 16°,
indicating a very hydrophilic material. It is this strong hydrophilic
property that prevents Pd@SM from emulsifying n-octane and
azobenzene-based
ionic
liquid
surfactant
(ILS)
[
[
C
C
4
AzoC
AzoC
2
DMEA]Br, [C
DMEA]Br (see chemical structures in Figure 1a). It was
4
AzoC
4
DMEA]Br, [C
4
AzoC DMEA]Br or
6
4
8
found that stable Pickering emulsions were destabilized resulting
in complete phase separation of water and oil upon UV irradiation
with stirring, but could be restored by subsequent irradiation with
visible light after homogenisation. Thus the system could be
reversibly switched between emulsified and demulsified by
alternate irradiation with UV and visible light (Figure 1b). We show
that the light-switchable emulsification and demulsification is
attributed to the light switched surface activity of the ILS. As an
example of applications, highly efficient catalytic hydrogenation of
several unsaturated hydrocarbons was carried out in the
Pickering emulsion at ambient conditions coupled with product
separation and emulsifier and catalyst recycling.
4 2
water. However, addition of aqueous [C AzoC DMEA]Br into n-
octane in the presence of Pd@SM results in a more or less stable
O/W Pickering emulsion depending on the concentration of
[C
4
AzoC
2
DMEA]Br. According to orthogonal experiments, the
AzoC DMEA]Br and
effects of the concentration of both [C
4
2
Pd@SM on Pickering emulsion stability were studied, and the
results are shown in Table S1. It is noted that when the
DMEA]Br was 1x10-3 mol/kg, the
4 2
concentration of [C AzoC
required minimum content of Pd@SM for the formation of a stable
Pickering emulsion was 0.5 wt.%. However, as the concentration
4 2
of [C AzoC
DMEA]Br increased to 3x10-3 mol/kg, as little as 10
-4
wt.% of Pd@SM was enough to form a stable Pickering emulsion.
AzoC DMEA]Br alone forms a stable O/W emulsion with n-
octane and water without particles, which means that it is also
surface-active. Thus [C AzoC DMEA]Br and Pd@SM exhibit a
[
C
4
2
4
2
synergistic effect in Pickering emulsion stabilisation. The droplet
test[15b, 21] was used to determine the type of emulsion formed. For
this purpose,
a
drop of emulsion in the system
was added
[
C
4
AzoC DMEA]Br/Pd@SM/n-octane/water
2
separately to water and n-octane, and the results are shown in
Figure S6. An O/W emulsion was clearly confirmed, backed up by
fluorescence microscopy images with sodium fluorescein dyeing
(
Figure S7). Moreover, the optical microscope image in Figure 3a
indicates that the droplets are polydisperse with diameters
between 5 and 30 μm.
Figure 1. (a) Chemical structure of azobenzene-based ILS; (b) photo’ of the
reversible light-induced transition between complete phase separation and
emulsification of a Pickering emulsion containing ILS.
1
The synthesis and H NMR characterization of the azobenzene-
based ILS are described in the Supporting Information.
Dibromoalkanes were used in the synthesis of the ILS to shorten
the reaction time and enhance the yield of the product. The
palladium-containing silica microspheres, Pd@SM, were
[
19]
prepared according to the Stꢀber method . For metal Pd support,
the silica surface was first modified by N-(2-aminoethyl)-3-
aminopropyltriethoxysilane to obtain amino-functionalized silica
(
2
SM-NH ), and the detailed procedures are provided in the
Supporting Information. The structure and morphology of the as-
prepared Pd@SM were characterized by transmission electron
microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and
X-ray diffraction (XRD), and the results are shown in Figure 2 and
Figures S1-S4. TEM results showed that the SM and Pd@SM
particles were spherical with diameters of about 200 nm (Figure
Figure 2. (a) TEM image of SM; (b) TEM image of Pd@SM; (c) Magnified TEM
image of Pd@SM; (d) XPS spectrum of Pd@SM; (e) elemental distribution on
SM and Pd@SM.
2a and 2b), and Pd was coated on the surface of the silica to a
thickness of 3-5 nm (Figure 2c). The XPS spectrum (Figure 2d)
confirmed that the Pd content was 1.21 wt.%. XRD results (Figure
S1) indicated that after Pd loading, a new diffraction peak
appeared near 40° which is characteristic of the (111) crystal
To evaluate the influence of the chemical structure of the ILS
4 4
on the formation of Pickering emulsions, [C AzoC DMEA]Br,
[C AzoC DMEA]Br and [C AzoC DMEA]Br, where the
4
6
4
8
hydrophilicity of them decreases with increasing chain length but
all remain water soluble and octane-insoluble, were used
separately with Pd@SM for emulsification and the results are
given in Tables S2-S4. Similarly, they could emulsify n-octane and
plane of Pd(0)[20]
.
It was found experimentally that Pd@SM alone could not
emulsify a mixture of n-octane and water (oil:water ratio of 1:1) to
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COMMUNICATION
water in the presence of Pd@SM to fabricate O/W emulsions, but
speed up the demulsification and re-emulsification. For example,
as shown in Table S6, decreasing the thickness of the emulsion
from 2.70 cm to 0.75 cm caused the demulsification time to
decrease from 30 min to 10 min. Increasing the irradiated area of
the system from 0.28 cm to 0.84 cm caused the demulsification
time to be reduced to 5 min, while the re-emulsification time was
shortened from 60 min to 8 min by decreasing the thickness of the
emulsion and simultaneous increasing the irradiated area and
light intensity.
in
a much wider concentration range. A photograph of
representative stable Pickering emulsions is shown in Figure S8,
and the minimum content of ILS and Pd@SM for the formation of
a stable Pickering emulsion in the different systems is listed in
Table S5, together with the critical aggregate concentration (CAC)
of the ILS determined in water. It can be seen that for a given
amount of Pd@SM, the concentration of ILS in water required to
form a stable Pickering emulsion is gradually reduced in the order:
2
2
[
[
C
C
4
AzoC
AzoC
2
DMEA]Br > [C
DMEA]Br. For example, when the content of Pd@SM
AzoC DMEA]Br,
AzoC DMEA]Br is
4
AzoC
4
DMEA]Br > [C
4
AzoC
6
DMEA]Br >
To understand the reversible transition of the Pickering
emulsion, the zeta potentials of Pd@SM in water, the adsorption
4
8
was 0.5 wt.%, the minimum concentration of [C
[
1
4
2
isotherm of [C
water surface tension of [C
determined. The zeta potentials of SM, SM-NH
2
4
AzoC
2
DMEA]Br onto these particles and the air-
AzoC DMEA]Br solutions were
and Pd@SM (0.5
C
4
AzoC
4
DMEA]Br, [C
4
AzoC
6
DMEA]Br and [C
4
8
4
2
-3
-4
-4
-5
x10 , 3x10 , 1x10 and 3x10 mol/kg, respectively. This result
shows that increasing the alkyl spacer length between the
azobenzene group and the cationic head group significantly
reduced the concentration of ILS required for the formation of a
stable Pickering O/W emulsion. Actually, this concentration is
lower than the CACs of the ILS in water. This implies that in the
presence of Pd@SM, only a small fraction of the ILS is sufficient
to emulsify n-octane and water.
wt.%) in pure water were -34.0, +9.1 and +28.9 mV respectively,
indicating that modification of SM with amine and then Pd led to
an increase in the zeta potential. On the other hand, the zeta
potential of Pd@SM increases with an increase in the
concentration of [C
at a concentration of 1x10 mol/kg (Table S7), and the dispersion
of Pd@SM in aqueous [C AzoC DMEA]Br became more
stable.[22] This result suggests that [C
AzoC DMEA]Br was
adsorbed onto the surface of Pd@SM. In order to understand how
AzoC DMEA]Br adsorbs onto the surface of Pd@SM, 4-((4-
butylphenyl)diazenyl)phenol (C AzoOH) which is an important
structural segment in cations of our ILS, was used as an
adsorption dye on the surface of SM, SM-NH and Pd@SM. It is
shown that Pd@SM has significant absorption of C AzoOH (see
Figure S9), but SM and SM-NH do not. This provides evidence
4 2
AzoC DMEA]Br in water. It reached +46.8 mV
-3
4
2
4
2
[
C
4
2
4
2
4
2
that the coordination interaction of Pd on the surface of Pd@SM
with -OH group and delocalized π electrons of the azobenzene
functional group may be the main driving force for the adsorbtion
of [C
The adsorption isotherm of [C
was also determined. It can be seen from Figure 3c that the
adsorbed amount initially increased rapidly with
AzoC
4
AzoC
2
DMEA]Br onto particles.
4
AzoC
2
DMEA]Br onto Pd@SM
Figure 3. Optical micrographs of [C
emulsion droplets (a) before light irradiation and (b) after the fifth cycle of UV
and visible light irradiation; (c) adsorbed amount of [C
surface of Pd@SM vs equilibrium concentration of [C
and after UV irradiation at 25 °C.
4 2
AzoC DMEA]Br/Pd@SM n-octane-in-water
4
AzoC
2
DMEA]Br on the
4
AzoC
2
DMEA]Br before
[
C
4
2
DMEA]Br concentration and then reached a plateau of
-3
0
.036 mmol/g at 1x10 mol/kg, corresponding to a molecular area
2
Interestingly, a stable Pickering emulsion could be demulsified
resulting in complete phase separation of oil and water upon UV
irradiation for 30 min at 25 °C with stirring. Subsequently, using
visible light to irradiate the system for 60 min at the same
temperature with stirring, a stable Pickering emulsion was re-
formed after homogenisation. Therefore, we could achieve
reversible switching between a stable Pickering emulsion and
complete demulsification by alternate exposure to UV and visible
light with stirring. Moreover, this demulsification and re-
emulsification process did not have any significant effect on the
microstructure and morphology of the emulsion after 5 cycles
of 0.34 nm /molecule.For comparison, we also determined the
4 2
surface tension of aqueous [C AzoC DMEA]Br solutions as a
function of concentration. The minimum area per molecule (Amin
0.51 nm /molecule) at the air-water interface was estimated using
the Gibbs adsorption isotherm.[10b] Clearly, the molecular area of
=
2
[C
4
AzoC
2
DMEA]Br adsorbed on Pd@SM is less than that at the
AzoC DMEA]Br on the
air-water interface. This adsorption of [C
4
2
surface of nanoparticles enhanced the surface activity of Pd@SM
at the oil-water interface.[5a]
Moreover, it is noted from Table S7 that after UV irradiation,
there was no obvious change in the zeta potential of Pd@SM in
the presence of 1x10-3 mol/kg [C
(
Figure 3b). Similar switchable transitions between stable and
unstable Pickering emulsions fabricated by [C AzoC DMEA]Br,
AzoC DMEA]Br or [C AzoC DMEA]Br was also observed. It
4 2
AzoC DMEA]Br in water,
implying that light irradiation has no effect on the particle charge
at the studied concentration. However, the adsorbed amount of
4
4
[
C
4
6
4
8
should be noted that turbidity of the Pickering emulsion can
prevent the transmission of light and reduce the speed of
demulsification and re-emulsification. Thus, stirring was used to
reduce the effect of turbidity on the demulsification and re-
emulsification. Moreover, reducing the thickness of the sample
and increasing the light intensity and irradiation area could all
4 2
[C AzoC DMEA]Br on the surface of Pd@SM significantly
decreased after UV irradiation (Figure 3c). This decrease
weakens the emulsifying ability of the nanoparticles, resulting in
demulsification of the Pickering emulsion.
It is known that the configuration of the azobenzene-based
compound cation can be changed from trans- to cis- isomer under
UV irradiation in water (Figure S10), leading to a significant
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Angewandte Chemie International Edition
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COMMUNICATION
enhancement of the hydrophilicity of the ILS,[23] increase of the
surface tension of an aqueous solution and reduction of its
surface activity. For example, after UV irradiation, the surface
other four reactants achieved quantitative conversion within 90
min, indicating the excellent reaction efficiency in the Pickering
emulsion. As an example, the catalytic hydrogenation of styrene
was used to evaluate the cycling performance of the light-
responsive Pickering emulsion, and the results are shown in
Figure S12. As can be seen, there was no clear decrease in
catalytic activity after 6 cycles of emulsification and phase
separation, indicating that the Pickering emulsion reported here
has good recyclable performance for efficient catalytic
-3
tension of 1x10 mol/kg [C
from 49.6 mN/m to 56.3 mN/m, and its CAC increased from
.3x10-3 to 1.3x10-2 mol/kg (Figure S11). The decrease in surface
activity of [C AzoC DMEA]Br is not beneficial for the formation of
a Pickering emulsion. On the other hand, by further irradiation with
visible light, the reverse isomerization of [C AzoC DMEA]Br
4 2
AzoC DMEA]Br in water increased
2
4
2
4
2
cation from cis- to trans- isomer was observed. Therefore, the
reversible switching between demulsification and emulsification of
the Pickering emulsion originates from the change in the
amphiphilic character of the azobenzene-based ILS after
isomerisation of the azobenzene groups[18b].
The above reversibly switched Pickering emulsions may be of
great importance for the design of efficient and recyclable reaction
systems. As a proof of concept, our light-switchable Pickering
emulsions were used as a micro-reactor for the highly efficient
catalytic hydrogenation of several unsaturated hydrocarbons at
4 2
hydrogenation, and [C AzoC DMEA]Br is stable in this process
(as confirmed by UV-vis spectra in Figure S13). In addition, highly
efficient catalytic hydrogenation was performed at room
temperature and atmospheric pressure which reduces the risk
caused by high pressure and temperature in the hydrogenation
reaction. Therefore, the Pickering emulsions designed in this work
are an efficient, safe and recyclable catalytic hydrogenation
vehicle. By using these novel Pickering emulsions, the limitations
caused by conventional Pickering emulsions can be overcome.
Table 1. Conversion of catalytic hydrogenation in an O/W Pickering
2
25 °C and atmospheric pressure (see Figure 4a), where H was
emulsion at 25 °C and 101 kPa.
bubbled into the emulsion and Pd@SM was used as catalyst in
the reaction. In addition to its own scientific significance, catalytic
hydrogenation of unsaturated hydrocarbons in gasoline is also an
important method to produce high quality gasoline and to resolve
the environmental problems caused by incomplete combustion of
gasoline and discharge of particulate pollutants into the
atmosphere. Since the emulsion is O/W, unsaturated
hydrocarbons such as styrene could diffuse into the center of the
oil dispersed phase with stirring to take part in the reaction. After
the reaction was complete, the system was irradiated by UV light
and the stable Pickering emulsion was destroyed to give complete
phase separation of n-octane and water (residual n-octane in
water was ~ 5 ppm). After separation of the product, the two-
phase system could reform into a stable Pickering emulsion using
visible light irradiation and homogenisation again. In this way, the
ILS and catalyst could be recycled simply.
Substrate
Product
Reaction time (min)
40
Conversion (%)
＞99
90
80
80
94
＞99
＞99
＞99
30
CILS = 9x10-3 mol/kg, CPd@SM = 1 wt.%, 1.5 mL n-octane and 1.5 mL water
were used to form the Pickering emulsion. The conversion of the reaction
1
were determined by H NMR.
In conclusion, we designed and prepared a novel class of light-
responsive Pickering emulsion. It was found that water and n-
octane could be emulsified using a mixture of Pd@SM and
azobenzene-based ILS as stabiliser, and the Pickering emulsions
could be reversibly switched between stable and unstable by
alternate irradiation with UV and visible light. Adsorption of the
azobenzene-based ILS cation on the surface of Pd@SM is the
main reason why synergism is observed. UV irradiation results in
a decrease in the surface activity of the azobenzene-based ILS
and leads to demulsification/complete phase separation of the
Pickering emulsions. However, visible light irradiation enables re-
emulsification to a stable Pickering emulsion again with stirring.
Considering the fact that light is a non-invasive, clean and
remotely controlled stimulus, these light-switchable Pickering
emulsions are clean and easily controllable micro-reactors for
chemical reaction, separation and recycling. As a result, these
light-switchable Pickering emulsions were used for the highly
efficient catalytic hydrogenation of several unsaturated
hydrocarbons at room temperature and atmospheric pressure. It
was found that the conversion was above 94%. In the light-
Figure 4. (a) Catalytic hydrogenation of styrene in O/W Pickering emulsion at
25
°C and atmospheric pressure; (b) schematic illustration of the light-
switchable emulsification and complete phase separation of Pickering
a
emulsion for catalytic hydrogenation, product separation and recycling of the
ILS and catalyst.
Based on the above strategy, the catalytic hydrogenation of
styrene, phenylpropene, α-methylstyrene, phenylacetylene and
methyl acrylate in [C AzoC DMEA]Br/Pd@SM n-octane-in-water
4 2
Pickering emulsions was investigated, and the results are shown
in Table 1. It is clearly noted that except for phenylpropene, the
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COMMUNICATION
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4062-4068.
switchable process within
a
Pickering emulsion, the
hydrogenation reaction, product separation and emulsifier and
catalyst recycling were well integrated in a simple way. The
strategy developed in this work opens a new pathway for the
development of sustainable chemical processes.
[
[
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Acknowledgements
The authors gratefully acknowledge financial support from the
National Natural Science Foundation of China (No. 21803017,
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11 project (No.D17007). BPB kindly acknowledges funding from
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Keywords: Pickering emulsion ·light switchable ·ionic liquid
surfactant ·reversible emulsification/demulsification ·catalytic
hydrogenation
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This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.202010750
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Zhiyong Li, Yunlei Shi, Anlian Zhu,
Yuling Zhao, Huiyong Wang, Bernard P.
Binks* and Jianji Wang*
Page No.1 – Page No. 5
Light-switched
reversible
emulsification and demulsification
of oil-in-water Pickering emulsions
A novel class of light-switchable Pickering emulsion was designed and prepared,
which could be reversibly switched between stable and unstable by alternately using
UV and visible light. By utilizing this novel phase behavior of the Pickering emulsion,
highly efficient catalytic hydrogenation, product separation and emulsifier and
catalyst recycling was achieved.
This article is protected by copyright. All rights reserved.