U.S. patent application number 13/996783 was filed with the patent office on 2014-01-30 for dissymmetric particles (janus particles), and method for synthesizing same by means of bipolar electrochemistry.
This patent application is currently assigned to UNIVERSITE BORDEAUX 1. The applicant listed for this patent is Alexander Kuhn, Gabriel Michel Pierre Loget. Invention is credited to Alexander Kuhn, Gabriel Michel Pierre Loget.
Application Number | 20140030527 13/996783 |
Document ID | / |
Family ID | 44351666 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140030527 |
Kind Code |
A1 |
Loget; Gabriel Michel Pierre ;
et al. |
January 30, 2014 |
DISSYMMETRIC PARTICLES (JANUS PARTICLES), AND METHOD FOR
SYNTHESIZING SAME BY MEANS OF BIPOLAR ELECTROCHEMISTRY
Abstract
Dissymmetric particles also called Janus particles of micron or
submicron size and methods of synthesis of Janus particles by
bipolar electrochemistry, based on substrates of isotropic or
anisotropic shape. The particles include an electrically conductive
substrate having at least a chemically and/or physically modified
part by deposit of a layer of electrochemically depositable
material, and a non-modified part. The particles are of isotropic
shape, and the layer of electrochemically depositable material has
a specific shape delimited by a precise contour.
Inventors: |
Loget; Gabriel Michel Pierre;
(Bordeaux, FR) ; Kuhn; Alexander; (Guillac,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Loget; Gabriel Michel Pierre
Kuhn; Alexander |
Bordeaux
Guillac |
|
FR
FR |
|
|
Assignee: |
UNIVERSITE BORDEAUX 1
Talence Cedex
FR
|
Family ID: |
44351666 |
Appl. No.: |
13/996783 |
Filed: |
December 15, 2011 |
PCT Filed: |
December 15, 2011 |
PCT NO: |
PCT/FR2011/053001 |
371 Date: |
October 15, 2013 |
Current U.S.
Class: |
428/403 ;
204/471; 204/622 |
Current CPC
Class: |
C25D 13/12 20130101;
B01J 13/04 20130101; Y10T 428/2991 20150115; C25D 5/02
20130101 |
Class at
Publication: |
428/403 ;
204/471; 204/622 |
International
Class: |
C25D 13/12 20060101
C25D013/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2010 |
FR |
1061031 |
Claims
1. Janus particles of micron or submicron size, each particle
comprising: an electrically conductive substrate having at least
one chemically and/or physically modified part by deposit of a
layer of electrochemically depositable material, and an unmodified
part, wherein said particles are of isotropic shape, and wherein
the layer of electrochemically depositable material has a specific
shape delimited by a precise contour.
2. The particles according to claim 1, wherein the particles
exhibit at least two chemically and/or physically modified
parts.
3. The particles according to claim 2, wherein one of said at least
two modified parts is covered with a layer of a first
electrochemically depositable material, and the other part of said
at least two modified parts is covered with a layer of a second
electrochemically depositable material different from said first
material.
4. The particles according to claim 3, wherein said first and
second materials are electrically conductive materials.
5. The particles according to claim 3, wherein said first and
second materials are insulating materials.
6. The particles according to claim 3, wherein said first material
is an electrically conductive material and said second material is
an insulating material.
7. The particles according to claim 1, wherein the shape of the
layer of electrochemically depositable material is a circular line
of variable diameter, a point, a hemisphere, or a portion of a
hemisphere.
8. The particles according to claim 1, wherein electrically
conductive materials forming the substrate of the particles
comprise metals or semi-conductive metals.
9. The particle according to claim 8, wherein the material
comprises a metal selected from the group consisting of gold,
copper, zinc, silver, platinum and nickel.
10. The particles according to claim 8, wherein the material
comprises a semi-conductive metal, selected from the group
consisting of ZnO, CdS, CdSe and TiO.sub.2.
11. The particles according to claim 3, wherein the insulating
materials are polymeric materials, organic molecules, silica-based
sol-gel materials, metal oxides or metal salts.
12. The particles according to claim 11, wherein the polymeric
material are chosen from among the families of polypyrroles,
polyanilines and polythiophenes.
13. The particles according to claim 1, wherein the substrate is a
bead of a conductive or semi-conductive material.
14. The particles according to claim 13, wherein the substrate is a
bead of carbon or metal or metal alloy.
15. An electrochemical method of synthesis of Janus particles based
on submicron or micron electrically conductive substrates, the
method comprising: A. introducing said substrates and at least one
source of electrochemically depositable material in an electrolytic
solution contained in an electrodeposition cell defined by two
separators, said cell being positioned between two electrodes; and
B. applying a potential difference E between the two electrodes
such as to create a sufficiently strong electric field E and for a
sufficiently long period of time for forming Janus particles.
16. The method according to claim 15, wherein the separators are
not permeable to the substrates, and are placed in a same reactor
of electrodeposition containing the electrolytic solution and the
electrodes, by being positioned between said electrodes such as to
define: the electrodeposition cell wherein the substrates and the
source(s) of electrically conductive material are put in solution,
a cathodic compartment, incorporating the electrode serving as
cathode and adjacent to one of said separators, and an anodic
compartment, incorporating the electrode serving as anode and
adjacent to the other separator.
17. The method according to claim 15, wherein the separators of the
electrodeposition cell are in a waterproof material.
18. The method according to claim 15, wherein the at least one
source of electrochemically depositable material is selected from
the group consisting of metal ions, semi-conductors formed from
metal salts, electro-polymerizable monomers, organic
electro-crystallizable salts, inorganic electro-crystallizable
salts, organic electro-graftable molecules, electrophoretic paints
and precursors of silica-based sol-gel materials.
19. The method according to claim 15, wherein the at least one
source of electrochemically depositable material is selected from
the group consisting of monomers derived from pyrrole, aniline and
thiophene.
20. The method according to claim 15, wherein the at least one
source of the material is selected from the group consisting of
precursors of alkoxysilane type which are selected from methyl
trimethoxysilane (MTMS), tetraethoxysilane (TEOS),
methyltriethoxylsilane (MTES) dimethyldiethoxysilane, and
combinations thereof.
21. The method according to claim 15, wherein the at least one
source of the material is selected from the group consisting of
metal ions of gold, copper, zinc, silver, platinum and nickel.
22. The method according to claim 15, wherein before application of
the potential difference E between the two electrodes, a shape of
the layer of the electrochemically depositable material is
defined.
23. The method according to claim 15, wherein the electrolytic
solution is an aqueous solution.
24. The method according to claim 15, wherein the electrolytic
solution is an aqueous solution, a non-aqueous solvent solution, or
a combination thereof.
25. The method according to claim 15, wherein the substrates are
particles of isotropic shape.
26. The method according to claim 15, wherein the substrates are
particles of anisotropic shape.
27. The method according to claim 15, wherein the substrates are
beads or nanotubes of carbon or metal.
28. The method according to claim 25, wherein the electrolytic
solution is in the form of a gel.
29. The method according to claim 28, wherein the electrolytic
solution is a hydrogel.
30. A device for implementing the method according to claim 16,
wherein the device comprises: an electrodeposition cell containing
the electrolytic solution, said cell being bounded by separators
into a sealing material, outside which electrodes are positioned
contiguously.
Description
PRIORITY
[0001] The present application is a National Phase entry of PCT
Application No. PCT/FR2011/053001, filed Dec. 15, 2011, which
claims priority from FR Patent Application No. 1061031, filed Dec.
22, 2010, which applications are hereby incorporated by reference
in their entireties.
FIELD OF THE INVENTION
[0002] The present invention generally relates to dissymmetric
particles, also called Janus particles of micron or submicron size,
as well as a method of synthesis of such particles by bipolar
electrochemistry.
REFERENCES
[0003] In the description below, the references in exponent
position refer to the list of references given after the
examples.
BACKGROUND OF THE INVENTION
[0004] In Roman mythology, Janus is a god with a head but with two
opposite faces. By analogy, the term "Janus" qualifies any
dissymmetric object, such as a spherical particle whereof the two
hemispheres would be physically and/or chemically different.
[0005] In embodiments of the present invention, by the term Janus
particles, is meant dissymmetric particles of micron or submicron
size having two parts that are chemically different and/or have
different polarities.sup.1.2. Due to these properties, these
particles constitute a unique category of materials that have a
growing interest to both the industry and the scientific community.
In fact, such particles can be used in a large number of
applications ranging from catalysis.sup.3 fields to therapeutic
treatments.sup.4. Until now, most of the techniques and methods
used to generate such objects required to break the symmetry by
introducing an interface.sup.2,5,6,7. However, this has the
disadvantage of making the preparation of large quantities of
particles rather difficult in as far as most techniques usually
lead to equivalents of a monolayer of materials, since the particle
modifications take place in a two-dimensional reaction space.
[0006] As a consequence, there is thus an increasing need in the
development of alternative techniques and methods for replacing the
two-dimensional approaches with real three-dimensional techniques,
which allow for an extrapolation (in the sense of a change of
scale) of a small scale production of Janus particles (typically at
a laboratory scale) towards a large-scale production of industrial
type.
[0007] Currently, there are only three really specific
three-dimensional methods, but which do not allow a fine adjusting
of the drive force of the modification.sup.8,9,10. For example, one
possible approach is based on the generation of charge carriers on
semiconductors using light.sup.8 or antenna.sup.9 effects. Another
interesting method is that described by Banin et al.sup.10 which
consists in using the HAuCI.sub.4 compound to make a material grow
on gold tubes or on cadmium selenide nanotubes.
[0008] Within this context, bipolar electrochemistry represents
another attractive possibility of selectively modifying particles
in a three-dimensional reaction medium. This concept, which was
first described by Fleischmann et al..sup.11 in 1986, is based on
the fact that when placing a conductive object in an electric field
of high intensity between two electrodes, a polarization which is
proportional to the electric field as well as to the characteristic
dimensions of the object, appears. If the polarization is strong
enough, the oxidation-reduction reactions can occur at the opposite
ends of the object.
[0009] There are recent applications of this concept as a drive
force in the electrochemiluminescence reactions.sup.12 as detection
modes in capillary electrophoresis.sup.13, for the preparation of
structured surfaces.sup.14, for the functionalization of membrane
pores.sup.15, for the creation of electrical contacts.sup.16 and as
a mechanism for moving micro-objects.sup.17.
[0010] The potential value V created between the two ends of a
conductive substrate placed in an electric field is given by the
equation (1) herebelow:
V=E d (1)
with E defining the overall electric field and d defining the size
of the particle.
[0011] It results that when an electric field of appropriate
intensity is used, the drive force which constitutes the potential
difference V can be used to carry out oxidation reduction reactions
at the two ends of the substrate, thus leading to dissymmetrization
of the particles as is illustrated on FIG. 1 attached to the
present application. On this figure, "+" indicates the oxidation
site and "-" the reduction site.
[0012] In order to achieve the two oxidation-reduction reactions at
the opposite sides of an object, the potential difference V must be
in first approximation at least equal to the difference between the
formal potentials of the two oxidation-reduction pairs involved.
For example, if one wishes to carry out dissymmetric
functionalization with gold at the negatively charged ends by means
of tetrachloroaurate, the following reaction must be carried
out:
[Au.sup.IIICl.sub.4].sup.-+3e.sup.-.fwdarw.Au.sup.0.sub.(s)+4Cl.sup.-E.s-
up.0=0.99 V vs NHE (2)
with NHE being the normal hydrogen electrode serving as
reference.
[0013] In order to be able to balance the consumption of fillers,
an oxidation reaction must take place at the opposite end assuming
that it is consists in the oxidation of water:
2H.sub.2O.sub.(1).fwdarw.4H.sup.+.sub.(1)O.sub.2(g)+4e.sup.-E.sup.0=1.23
V vs NHE (3)
[0014] It immediately ensues that, in this case, a minimal
potential difference of approximately:
.DELTA. V min = ? ? ? ? = 0.24 V ? indicates text missing or
illegible when filed ( 4 ) ##EQU00001##
is required to trigger the reaction.
[0015] This becomes a problem inherent to this approach when the
objects to be functionalized are of micro- or nanometric size,
since E must then reach values of the order of MV m.sup.-1. This is
not compatible with a conventional industrial environment, and
particularly when using aqueous solutions, due to intrinsic
parasitic reactions, which are accompanied by the formation of
macroscopic gas bubbles at each electrode, such that it disrupts
the orientation of objects in the electric field.
[0016] This problem was partly resolved by Bradley et al. using
organic solvents, such as to enlarge the potential window of the
electrolyte, and thereby making it possible to generate metal
deposits dissymmetrically on different objects of micron or
submicron size.sup.18,19. However, the technique used by Bradley et
al. has the disadvantage of requiring the need to immobilize the
objects on a surface such as to prevent them from rotating, meaning
that the technique developed by Bradley et al. is in fact still a
two-dimensional method and not a real three dimensional method
taking place in the entire volume of the reactor.
[0017] It has recently been demonstrated that it was possible to
overcome these drawbacks by a method of capillary electrophoresis
implemented such as to be able to apply a high electric
field.sup.20,21. However, considering that the modification of the
particles is carried out in a capillary whereof the internal
diameter cannot exceed a few hundred microns, the production of
Janus particles is very slow, making this method unprofitable for
industrial application.
SUMMARY OF THE INVENTION
[0018] Hence, a purpose of embodiments of the present invention is
to overcome all or part of the disadvantages of the prior art, by
implementing a truly three-dimensional method exhibiting a high
flexibility of use, which makes the formation of a broad range of
Janus particles possible in terms of material, size, shape and
nature of the modification. Thus, the method developed by the
applicants allows for the formation of Janus particles of micron or
submicron size exhibiting an isotropic or anisotropic shape and
whereof the modified part has a specific shape delimited by a
precise outline.
[0019] Particularly, embodiments of the present invention relate to
Janus particles of micron or submicron size comprising an
electrically conductive substrate exhibiting an at least chemically
and/or physically modified part by deposit of a layer of
electrochemically depositable material and an unmodified part.
[0020] According to embodiments of the invention, these Janus
particles are of isotropic shape, and the layer of
electro-chemically depositable material has a specific shape
delimited by a precise contour.
[0021] By specific shape delimited by a precise contour is meant
according to embodiments of the present invention, a predefined
shape with precise contours, which is not a coincidence but a
choice motivated by the concerned application.
[0022] By way of shape delimited by a precise contour, it may be
particularly mentioned a circular line, point, or hemisphere or
part of a hemisphere, as is shown in the examples 5A to 5C.
[0023] Janus particles may have one or several chemically and/or
physically modified parts.
[0024] Thus, according to a particular embodiment of the present
invention, the Janus particles have two chemically and/or
physically modified parts, which can be identical or different.
[0025] For example, a particularly interesting configuration of the
particles according to an embodiment of the invention can for
example be the following: one of the parts is covered with a layer
of a first electrochemically depositable material, and the other
part is covered with a layer of a second electrochemically
depositable material different from said first material. For such a
configuration (two areas modified by covering with different
materials), several alternatives are possible depending on the
required application:
[0026] the first and second materials are electrically conductive
materials;
[0027] the first and second materials are insulating materials;
[0028] the first material is an electrically conductive material
and the second material is an insulating material.
[0029] By way of electrically conductive materials that can be used
within the framework of embodiments of the present invention, it
can be particularly cited metals and semiconductors.
[0030] Among the metals that can be used within the framework of
embodiments of the present invention it can more particularly be
cited gold, copper, zinc, silver, platinum and nickel.
[0031] Among the semiconductors that can be used within the
framework of embodiments of the present invention, it can be more
particularly cited ZnO, CdS, CdSe and Ti0.sub.2.
[0032] By way of an insulating material that can be used within the
framework of embodiments of the present invention, it may be
particularly cited polymeric materials, organic molecules
(particularly electrophoretic paint), silica-based sol-gel
materials, metal oxides or metal salts.
[0033] Among the polymeric material that can be used within the
framework of embodiments of the present invention, one may
particularly cite the polymers selected from the families of
polypyrroles, polyanilines and polythiophenes.
[0034] The substrate of the Janus particles must necessarily be an
electrically conductive substrate so that the polarization can take
place when the substrate is placed in the electric field between
two electrodes according to a method of the invention.
[0035] It may consist of a substrate in a conductive or
semi-conductive material, for example beads of carbon or of a metal
or a metal alloy.
[0036] Embodiments of the present invention also relate to an
electrochemical method for the synthesis of Janus particles based
on electrically conductive submicron or micron substrates, wherein
it comprises the following steps: [0037] A. said substrates and at
least one source of an electrochemically depositable material are
introduced into an electrolytic solution contained in an
electrodeposition cell defined by two separators, said cell being
arranged between two electrodes; [0038] B. a potential difference E
is applied between the two electrodes such as to create a
sufficiently strong electric field E and during a sufficiently long
period in order to form Janus particles.
[0039] The method according to embodiments of the invention is
applicable to particulate substrates of isotropic shape (in
particular beads), as well as to substrates of anisotropic shape
(for example, nanotubes or disks).
[0040] Particularly, the substrates are carbon or metal beads or
nanotubes.
[0041] In order to achieve, using the method according to
embodiments of the invention, Janus particles having two modified
parts, one proceeds as follows: [0042] in the case where there are
two materials of different nature, a material is generated by
reduction on one side (for example reduction of a metal cation),
and the other material by oxidation on the other side (for example
pyrrole oxidation) simultaneously; [0043] in the case where there
are two identical materials, voltage pulses can be imposed to allow
the particles to rotate during the method. It can also proceed with
a polarity reversal of the electrodes, which makes it possible to
switch the anodic and cathodic poles of the substrates during the
method.
[0044] According to a first particular embodiment of the method
according to the invention, the separators are not permeable to the
substrates and are placed in a same reactor of electrodeposition
containing the electrolytic solution and the electrodes, by being
arranged between said electrodes such as to define:
[0045] the electrodeposition cell wherein the substrates and the
source(s) of electrically conductive material are put in
solution,
[0046] a cathodic compartment, incorporating the electrode serving
as cathode and adjacent to one of said separators, and
[0047] an anodic compartment, incorporating the electrode serving
as anode and adjacent to the other separator.
[0048] In this embodiment, the separators, while being
non-permeable to substrates are still permeable to ions. For
example, it can consist in membranes that are non-permeable to
substrates as well to the source of electrodepositable material, or
it can also consist in frit materials, which are impermeable to
substrates, but let the material source through.
[0049] In this embodiment, the electric field intensity will be of
the order of 1 Kv/m to 1 MV/m, and its duration of application
ranging between 10 seconds and 10 minutes, either continuously or
intermittently and/or in an alternating manner.
[0050] According to a second embodiment of the method according to
the invention, the separators are in a sealing material. For
example, it may consist in thin glass walls or in plastic material
such as PLEXIGLAS.RTM.. In this embodiment, the intensity of the
electric field will be of the order of 1 Kv/m to 1000 MV/m, and its
application duration ranging between 10 seconds and several
hours.
[0051] As regards the source of electrochemically depositable
material which is introduced into the cell, the latter can be
selected from metal ions, metal salts (which form during the
implementation of the method according to embodiments of the
invention, first a hydroxide precipitating on the surface of the
substrate to then be transformed into an oxide), the
electro-polymerizable monomers, the organic electro-crystallizable
salts, inorganic electro-crystallizable salts, organic
electro-graftable molecules, electrophoretic paints and precursors
of silica-based sol-gel materials.
[0052] By way of electro-polymerizable monomers, it may be
particularly cited monomers derived from pyrrole, aniline and
thiophene.
[0053] By way of precursors of silica-based sol-gel materials, it
can also be cited precursors of alkoxysilane type which are
selected from methyl trimethoxysilane (MTMS), tetraethoxysilane
(TEOS), methyltriethoxylsilane (MTES) dimethyldiethoxysilane, and
combinations thereof.
[0054] By way of metal ions, it can be particularly cited metal
ions of gold, copper, zinc, silver, platinum and nickel.
[0055] Particularly, the shape of the layer of electrochemically
depositable material is defined by acting on the concentration of
the precursor filler and the electrodepositable material as well as
on the applied electric field, as the shape of the layer depends on
the competition between the direction of migration of the ions and
the kinetics of electrodeposition, which substantially depends on
the concentration of the precursor and the field applied.
[0056] The electrolytic solution implemented in the method
according to the invention may be an aqueous solution or a
non-aqueous solvent solution, for example toluene, acetonitrile, or
combinations thereof.
[0057] If Janus particles of isotropic shape are realized using the
method according to embodiments of the invention, it is important
that the electrolytic solution has a viscosity that is sufficient
to prevent or inhibit the particle from rotating. In a particular
embodiment, the electrolyte solution is gelled.
[0058] When the substrates are of anisotropic shape, it is not
necessary to increase the viscosity, but the viscosity can be
increased to ensure that the deposit has a specific shape.
[0059] Finally, embodiments of the present invention also relate to
a device for implementing the method according to embodiments of
the invention, wherein the device comprises an electrodeposition
cell containing the electrolytic solution, said cell being bounded
by separators into a sealed material outside which electrodes are
arranged in a contiguous manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] Other advantages and features of the present invention will
become apparent from the following description given by way of
non-limiting example and made with reference to the accompanying
drawings:
[0061] FIG. 1 represents a block diagram of the bipolar
electrodeposition used to form Janus particles,
[0062] FIG. 2 represents a block diagram of an example of
electrodeposition cell for implementing the method according to a
first embodiment;
[0063] FIG. 3 represents a block diagram f an electrodeposition
device for implementing the method according to a second
embodiment;
[0064] FIG. 4 schematically represents a Janus particle according
to the invention, of isotropic shape (in this instance a bead),
which has two modified areas.
[0065] FIGS. 5A to 5C correspond to three images of scanning
electron microscopy (SEM) of three examples of Janus particles
(carbon beads) according to embodiments of the invention of
isotropic shape,
[0066] FIG. 6 shows: [0067] a first set of four images A1 to A4 of
scanning electron microscopy (SEM) of substrates of micron size and
of anisotropic shape, before (image A1) and after bipolar
electrodeposition (images A2 to A4), and [0068] a second set of
four images B1 to B4 of scanning electron microscopy (SEM) of
substrates of micron size and of isotropic shape, before (image B1)
and after bipolar electrodeposition (images B2 to B4);
[0069] FIG. 7 shows two images A and B of scanning electron
microscopy (SEM) of substrates of submicron size and of isotropic
shape, before (image A) and after bipolar electrodeposition (image
B), the modified part corresponding to the small white dot;
[0070] FIG. 8 shows four images (a, b, c, d) of optical microscopy
in transmission of bi-functionalized copper/copper carbon tubes, by
means of the method according to an embodiment of the invention by
imposing voltage pulses;
[0071] FIG. 9a shows an image of scanning electron microscopy (SEM)
of a bi-functionalized copper/copper carbon tube by means of the
process according to an embodiment of the invention,
[0072] FIG. 9b shows an image of scanning electron microscopy (SEM)
of a bi-functionalized copper/polypyrrole carbon tube by means of
the method according to the invention,
[0073] FIG. 10 shows an image of scanning electron microscopy (SEM)
of a single crystal localized deposit of a platinum salt (white
part on FIG. 10) on a carbon bead by bipolar electrochemistry in
accordance with the method according to an embodiment of the
invention.
[0074] The identical elements represented on FIGS. 2 to 9 are
identified by identical numerical references.
DETAILED DESCRIPTION
[0075] FIG. 1, which is discussed in the description of the prior
art, represents a block diagram of an example of a device for
implementing the method according to a first embodiment of the
invention. This figure particularly shows that sufficient
polarization of a conductive particle makes it possible to break
the symmetry.
[0076] FIGS. 2 and 3 represent block diagrams of an
electrodeposition device for implementing the method according to
embodiments of the invention, each corresponding to a different
embodiment. These figures show that the electrodeposition device
comprises an electrodeposition cell 3, defined by two separators
31, 32, and is arranged between two electrodes 21, 22.
[0077] The operating principle for the two embodiments of the
electrodeposition device, which is the same one, comprises the
following steps: [0078] A. micron or submicron substrates 1 are
introduced and at least one source 41 of an electrochemically
material depositable in an electrolytic solution 40 contained in
the cell 3; [0079] B. a potential difference E is applied between
the two electrodes 21, 22 such as to create a sufficiently strong
electric field E and during a sufficiently long period for forming
Janus particles.
[0080] FIG. 3 more particularly represents an electrodeposition
device 3, which comprises an electrodeposition reactor 5 containing
the electrolytic solution 40, the electrodes 21 and 22 which are
immersed into the electrolytic solution, and the separators 31, 32
which consist of membranes or plates which are non-permeable to the
substrates. These membranes 31, 32 are arranged between the
electrodes 21, 22 such as to define: [0081] the electrodeposition
cell 3 itself, wherein the substrates 1 of an electrically
conductive material and the source 41 are introduced in order to
put them in solution, [0082] a cathodic compartment 51, which
includes the electrode serving as cathode 21 and is adjacent to one
of the membranes 31, and [0083] an anodic compartment 52, which
includes the electrode serving as anode 22 and is adjacent to the
other membrane 32.
[0084] FIG. 4 more particularly represents an electrodeposition
device 3 wherein the separators 31, 32 are in watertight material
(glass or PLEXIGLAS.RTM.). They delimit the electrodeposition cell
3 containing the electrolytic solution 40 and outside which 3 the
electrodes 21,22 are contiguously arranged.
[0085] The following examples illustrate the invention without
however limiting its scope.
EXAMPLES
Example 1
[0086] Synthesis of micron Janus particles according to an
embodiment of the invention, monofunctionnalized using the device
represented in FIG. 2
[0087] Monofunctionnalized Janus particles were synthesized in
accordance with the method according to an embodiment of the
invention by using the electrodeposition device represented on FIG.
2 wherein: [0088] a potential difference E of the order of 2 kV is
imposed between the electrodes, resulting in an electric field E of
100 kVm.sup.-1 in the electrodeposition cell, [0089] the separators
are proton exchange membranes or sintered glass plates, and [0090]
the electrodes 21, 22 are immersed in ethanol at -100.degree. C.
(to compensate for the effects of ohmic heating in the reactor) and
at a distance of the order of 2 cm from each other.
[0091] The substrates 1 used are either carbon tubes (images 6A1,
6A2 and 6A3) or vitreous carbon beads (images 6B1, 6B2 and 6B3),
the electrolytic solutions 40 are aqueous solutions which, as a
source of electrodepositable material, contain the following metal
salts:
AuCl.sub.4.sup.- at 1 mM (images 6A2 and 6B2), or PtCl.sub.6.sup.2-
at 10 mM (image 6A3), or Silver nitrate AgNO.sub.31 mM (image
6B3).
[0092] In the particular case of the use of substrates of vitreous
carbon beads, the electrolytic solution 40 is a hydrogel agar.
[0093] It was observed by scanning electron microscopy (SEM) the
substrates before (images 6A1 and 6B1) and after synthesis by
electrodeposition(images 6A2, 6A3, 6B2, 6B3). On FIGS. 6A1 to 6A3
and 6B1 to 6B3, the visible scale (white line) is of 5 m. The
results of these observations are summarized in table 1 below.
Example 2
[0094] Synthesis of micron Janus particles according to an
embodiment of the invention, monofunctionnalized using the device
represented on FIG. 3
[0095] Monofunctionnalized Janus particles were synthesized in
accordance with the method according to an embodiment of the
invention by using the electrodeposition device represented on FIG.
3 wherein: [0096] a potential difference E of the order of 6 kV is
imposed between the electrodes, resulting in an electric field E of
20 MV m.sup.-1 in the electrodeposition cell, [0097] the separators
are thin glass walls of 100 m and separated from each other also by
100 m; [0098] the substrates 1 used are either 1 carbon tubes
(images 6A1 and 6A4) or vitreous carbon beads (images 6B1 and 6B4),
[0099] the electrolytic solution 40 is a hydrogel of agar, which
contains, as a source of electrodepositable material, the gold
chloride AuCl.sub.4.sup.- at 10 mM (image 6A4) and gold chloride
AuCl.sub.4.sup.- at 1 mM (image 6B4).
[0100] It was observed by scanning electron microscopy (SEM) the
substrates before (images 6A1 and 6B1) and after the synthesis by
electrodeposition (images 6A4 and 6B4). On FIGS. 6A4 and 6B4, the
visible scale (white line) is also of 5 m. Results of these
observations are summarized in table 1 below.
TABLE-US-00001 TABLE 1 FIGS. Substrate Device Embodiment Shape of
deposit 6A1 C tubes -- -- 6A3 C tubes A (FIG. 2) point 6A3 C tubes
A (FIG. 2) cluster 6A4 C tubes B (FIG. 3) cluster 6B1 Vitreous C
beads -- -- 6B2 Vitreous C beads A (FIG. 2) Hemisphere dense
deposit 6B3 Vitreous C beads A (FIG. 2) point 6B4 Vitreous C beads
B (FIG. 3) Hemisphere non dense deposit
Example 3
Synthesis of submicron Janus particles according to embodiments of
the invention, monofunctionnalized by using the device represented
on FIG. 2:
[0101] Monofunctionnalized Janus particles were synthesized in
accordance with the method according to an embodiment of the
invention by using the electrodeposition device represented on FIG.
2 wherein: [0102] a potential difference E of the order of 2 kV is
imposed between the electrodes, resulting in an electric field of
100 kV m.sup.-1 in the electrodeposition cell; [0103] the
separators are proton exchange membranes or sintered glass plates;
[0104] the electrodes 21, 22 are immersed in ethanol at
-100.degree. C. (to compensate for the effects of ohmic heating in
the reactor) and at a distance of the order of 2 cm from each
other; [0105] the substrates 1 used are vitreous carbon beads; and
[0106] the electrolytic solution 40 is a hydrogel of agar, which
contains, as a source of electrodepositable material, gold chloride
AuCl.sub.4.sup.- at 10 mM.
[0107] It was observed by scanning electron microscopy (SEM) the
substrates before (images 7A) and after the synthesis by
electrodeposition (images 7B). On FIGS. 7A and 7B, the visible
scale (black line) is of 1 m.
Example 4
[0108] Synthesis of micron Janus particles according to embodiments
of the invention, copper/polypyrrole bi-functionalized by using the
device represented on FIG. 2:
Bi-functionalized copper/polypyrrole Janus particles were
synthesized in accordance with the method according to an
embodiment of the invention by using the electrodeposition device
represented on FIG. 2 wherein: [0109] a first electrolytic solution
40 consisting of a suspension of Cu.sup.I in acetonitrile at the
rate of 10 mM of Cu.sup.I is prepared, wherein carbon nanotubes are
introduced at the rate of 0.1 mg into the suspension; [0110] a
second electrolytic solution 40 is prepared comprising 10 mM of
Cu.sup.I and 50 mM of pyrrole, [0111] a sonication of these two
solutions is carried out during one minute, [0112] these two
suspensions 40 are introduced into the electrodeposition cell 3;
[0113] a potential difference of the order of 2 kV is imposed
between the electrodes; [0114] the separators are proton exchange
membranes; and [0115] the formation of a copper deposit is
generated on one of the ends of the tubes by reduction of cation
Cu.sup.+, and the formation of a deposit of pyrrole is generated on
the other side by oxidation of the pyrrole.
[0116] The thus obtained dissymmetrical copper/polypyrrole carbon
tubes were observed by scanning electron microscopy (SEM): FIG. 9b,
the visible scale (white line) is of 10 m. The deposits were
characterized by energy dispersive analysis (EDS)(FIG. 9c).
Example 5
[0117] Synthesis of micron Janus particles according to the
invention copper/copper bi-functionalized using the device shown on
FIG. 2
[0118] Bi-functionalized Janus particles were synthesized in
accordance with the method according to an embodiment of the
invention by using the electrodeposition device represented on FIG.
2 wherein: [0119] an electrolytic solution 40 consisting of a
suspension of Cu.sup.I in acetonitrile at the rate of 10 mM of
Cu.sup.I is prepared, wherein carbon nanotubes are introduced at
the rate of 0.1 mg into the suspension; [0120] then a sonication of
this solution is carried out during one minute, [0121] it is
introduced into the electrodeposition cell 3; [0122] a potential
difference is imposed in pulsed regime with an electric field of
125 MV m.sup.-1 in the electrodeposition cell: according to the
tested pulses varying between 12 s and 30 s, variations are
observed at the deposits, with a time interval between the pulses
(relaxation time) of 1 s or 5 minutes; [0123] the separators are
proton exchange membranes; and [0124] the formation of a copper
deposit is generated on each of the ends of the tubes.
[0125] The thus obtained modified bi-functionalized copper/copper
carbon nanotubes were observed by optical transmission microscopy:
on FIGS. 8a to 8d, the visible scale (black lines) is of 20 m.
FIGS. 8a (with a pulse interval of 5 minutes) and 8b (with a pulse
interval of 10 s) correspond to a pulse of 12 s, whereas FIGS. 8c
(with a pulse interval of 5 minutes) and 8d (with a pulse interval
of 10 s) correspond to a pulse of 30 s. The obtained particles were
also observed with a scanning electron microscope (SEM) (FIG.
9a).
[0126] When the relaxation time (time between pulse potentials
where the potential is stopped) is sufficiently long, symmetrically
modified tubes (FIGS. 8a and 8c) are obtained, whereas when this
time is short, the particles are only modified at one end (FIGS. 8b
and 8d). The imposition time of the electric field also makes it
possible to control the size of the deposit.
Example 6
[0127] Synthesis of micron Janus particles according to embodiments
of the invention, monofunctionnalized, using the device represented
on FIG. 2
[0128] Monofunctionnalized Janus particles were synthesized in
accordance with the method according to an embodiment of the
invention by using the electrodeposition device represented on FIG.
2 wherein: [0129] a potential difference E of the order of 1 kV is
imposed between the electrodes, resulting in an electric field of
25 kV m.sup.-1 in the electrodeposition cell; [0130] the separators
are sintered glass plates; [0131] the electrodes 21, 22 are
immersed in ethanol at -100.degree. C. (to compensate for the
effects of ohmic heating in the reactor) and at a distance of the
order of 4 cm from each other; [0132] the substrates 1 used are
vitreous carbon beads; and [0133] the electrolytic solution 40 is a
hydrogel of ethylcellulose in ethanol, which contains, as a source
of electrodepositable material, platinum chloride in the form of
acid H.sub.2PtCl.sub.6.sup.2- at 5 mM.
[0134] It was observed by scanning electron microscopy (SEM) the
nanoparticle thus obtained after synthesis by electrodeposition
(FIG. 10).
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