Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
  • C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/02—Making microcapsules or microballoons
  • B01J13/04—Making microcapsules or microballoons by physical processes, e.g. drying, spraying
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/02—Electroplating of selected surface areas
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated

Definitions

• the present invention generally relates to dissymmetric particles, also called submicron or micron size Janus particles, as well as a process for synthesizing such particles by bipolar electrochemistry.
• Janus is a god with one head but with two opposing faces.
• the term "Janus” qualifies any dissymmetrical object, such as a spherical particle whose two hemispheres are physically and / or chemically different.
• Janus particles are understood to mean asymmetric particles of submicron or micron size having two chemically and / or of different polarity 1,2 parts . Because of these properties, these particles are a unique class of materials that are of increasing interest to both industry and the scientific community. Indeed, such particles can be used in a large number of applications, ranging from the fields of catalysis 3 to therapeutic treatments 4 . Until now, most of the methods or methods used to generate such objects have required breaking the symmetry by introducing an interface 2,5,6,7 . However, this has the disadvantage of making it difficult to prepare large quantities of particles, since most of the techniques usually lead to equivalents of a monolayer of materials, since the modifications of the particles take place in a space.
• 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. 11 in 1986, is based on the fact that when a conductive object is placed in an electric field of high intensity between two electrodes, a polarization appears which is proportional to the electric field and the characteristic dimensions of the object. If the polarization is strong enough, oxidation-reduction reactions can occur at opposite ends of the object.
• Recent applications of this concept are found as a driving force in electrochemiluminescence reactions 12 , as a capillary electrophoresis detection mode 13 , for the preparation of structured surfaces 14 , for the functionalization of the pores of membranes, for the creation of electrical contacts and as a mechanism for moving micro-objects 17 .
• V E d (1) with E defining the global electric field and d defining the size of the particle.
• the potential difference V In order to be able to carry out two oxidation-reduction reactions at the opposite faces 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 couples engaged. For example, if it is desired to achieve asymmetric functionalization with gold at the negatively charged ends using tetrachloroaurate, the following reaction must be carried out:
• the object of the present invention is therefore to overcome all or part of the disadvantages of the prior art, by implementing a truly three-dimensional process and having a great flexibility of use, which makes possible the formation of a wide Janus particle range in terms of material, size, shape and nature of the modification.
• the process developed by the applicants allows the formation of Janus particles of micron or submicron size having an isotropic or anisotropic form and whose modified part has a specific shape delimited by a precise contour.
• the present invention relates to Janus particles of submicron or micron size comprising an electrically conductive substrate having at least a chemically and / or physically modified part by depositing a layer of electro-chemically removable material, and a non-electrically conductive part. changed.
• these Janus particles are of isotropic form, and the layer of electro-chemically removable material has a specific shape delimited by a precise contour.
• Janus particles may have one or more chemically and / or physically modified moieties.
• Janus particles have two chemically and / or physically modified portions, which may be the same or different.
• a particularly advantageous configuration of the particles according to the invention may for example be the following: one of the parts is covered with a layer of a first electro-chemically removable material, and the other part is covered with a layer of a second electro-chemically removable material different from said first material.
• a configuration two areas modified by overlapping with different materials
• several alternatives are possible depending on the application sought:
• the first and second materials are electrically conductive materials
• the first and second materials are insulating materials
• the first material is an electrically conductive material and the second material is an insulating material.
• electrically conductive materials usable in the context of the present invention, it is possible to include metals and semiconductors.
• metals that can be used in the context of the present invention, mention will be made more particularly of gold, copper, zinc, silver, platinum and nickel.
• insulating materials that may be used in the context of the present invention, there may be mentioned in particular polymeric materials, organic molecules (especially electrophoretic paints), sol-gel silica-based materials, metal oxides or salts. metal.
• polymeric materials that can be used in the context of the present invention, mention will be made more particularly of polymers chosen from the families of polypyrroles, polyanilines and polythiophenes.
• the Janus particle substrate must necessarily be an electrically conductive substrate for polarization to take place when the substrate is placed in the electric field between two electrodes in accordance with the method of the invention.
• It may be a substrate of conductive or semiconductor material, for example a carbon ball or a metal or a metal alloy.
• the present invention also relates to an electrochemical method for synthesizing Janus particles from electrically conductive submicron or micron substrates, characterized in that it comprises the following steps:
• the process according to the invention is applicable both to particulate substrates of isotropic form (in particular beads) and to substrates of anisotropic form (for example nanotubes or disks).
• the substrates (1) are balls or nanotubes of carbon or metal.
• a material is generated by reduction of one side (for example reduction of a metal cation), and the other material by oxidation on the other side (for example pyrrole oxidation) simultaneously;
• the separators are not permeable to the substrates and are placed in the same electrodeposition reactor containing the electrolytic solution and the electrodes, being arranged between said electrodes to define : o the electrodeposition cell in which the substrates and the source (s) of electrically conductive material are dissolved,
• a cathode compartment integrating the electrode serving as a cathode and adjacent to one of said separators, and an anode compartment, integrating the electrode serving as anode and adjacent to the other separator.
• the separators while not permeable to the substrates, are still ion permeable.
• they may be membranes impermeable to both the substrates and the source of electrocomposable material, or they may also be sintered, which are impervious to substrates, but allow the source of material to pass through. .
• the intensity of the electric field is advantageously of the order of lkV / m to lMV / m, and its duration of application advantageously between 10 seconds and 10 minutes, either continuously or intermittently and / or alternating.
• the separators are made of a waterproof material.
• it may be thin walls of glass or a plastic such as PLEXIGLAS®.
• the intensity of the electric field is advantageously of the order of lkV / m at 1000 MV / m, and its duration of application advantageously between 10 seconds and several hours.
• the source of electrochemically removable material which is introduced into the cell it is advantageously chosen from metal ions, metal salts (which form, when implementing the method according to the invention , in the first place a precipitant hydroxide on the surface of the substrate, to be subsequently transformed into an oxide), electropolymerizable monomers, electro-crystallizable organic salts, electrocrystallizable inorganic salts, electro-graftable organic molecules, electrophoretic paints and precursors of materials sol-gel based on silica.
• metal ions metal salts (which form, when implementing the method according to the invention , in the first place a precipitant hydroxide on the surface of the substrate, to be subsequently transformed into an oxide)
• electropolymerizable monomers electro-crystallizable organic salts, electrocrystallizable inorganic salts, electro-graftable organic molecules, electrophoretic paints and precursors of materials sol-gel based on silica.
• electropolymerizable monomers there may be mentioned monomers derived from pyrrole, aniline and thiophene.
• alkoxysilane precursors are selected from methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof .
• metal ions there may be mentioned metal ions of gold, copper, zinc, silver, platinum and nickel.
• the shape of the layer of electro-chemically removable material is defined by acting on the concentration and the charge of the precursor of the electrodepositable material as well as on the applied electric field, since the shape of the layer depends on the competition between the direction ion migration and electrodeposition kinetics, which is significantly dependent on the precursor concentration and the applied field.
• the electrolytic solution used in the process according to the invention may be an aqueous solution or a solution of non-aqueous solvent, for example toluene, acetonitrile, or mixtures thereof.
• the electrolytic solution has a sufficient viscosity which prevents the particle from rotating. Ideally, the solution electrolytic is gelified.
• the substrates are of anisotropic form, it is not necessary to increase the viscosity, but the viscosity can be increased to ensure a specific form of the deposit.
• the present invention also relates to a device for implementing the method according to the invention, characterized in that it comprises an electrodeposition cell containing the electrolytic solution, said cell being delimited by separators of a material sealed outside of which are arranged contiguously electrodes.
• FIG. 1 represents a schematic diagram of the bipolar electroplating used to form Janus particles
• FIG. 2 represents a schematic diagram of an exemplary electrodeposition cell for implementing the method according to the invention according to a first embodiment
• FIG. 3 represents a block diagram of an electrodeposition device for implementing the method according to the invention according to a second embodiment
• FIG. 4 schematically represents a Janus particle according to the invention, of isotropic form (in this case a ball), which has two modified zones.
• FIGS. 5A to 5C correspond to three images of scanning electron microscopy (SEM) of three examples of Janus particles (carbon beads) according to the invention of isotropic form,
• FIG. 7 shows two scanning electron microscopy (SEM) images A and B of substrates of submicron size and isotropic shape, before (image A) and after bipolar electroplating (image B), the modified part corresponding to the small point White ;
• FIG. 8 shows four images (a, b, c, d) of transmission optical microscopy of bifunctionalized copper / copper carbon tubes, obtained by means of the method according to the invention by imposing crenals of potentials;
• FIG. 9a shows a scanning electron microscopy (SEM) image of a bifunctionalized copper / copper carbon tube using the method according to the invention
• FIG. 9b shows a scanning electron microscopy (SEM) image of a bifunctionalized copper / polypyrrole carbon tube using the method according to the invention
• Figure 10 shows a microscopy image scanning electron (SEM) of a localized and monocrystalline deposit of a platinum salt (white part in Figure 10) on a carbon ball by bipolar electrochemistry according to the method according to the invention.
• SEM microscopy image scanning electron
• FIGS. 2 to 9 are identical elements shown in FIGS. 2 to 9 are identified by identical reference numerals.
• Figure 1 which is commented in the description of the prior art, shows a block diagram of an exemplary device for implementing the method according to the invention according to a first embodiment. This figure shows in particular that a sufficient polarization of a conductive particle makes it possible to break the symmetry.
• FIGS 2 and 3 show schematic diagrams of an electrodeposition device for implementing the method according to the invention, each corresponding to a different embodiment. These figures show that the electroplating device comprises an electrodeposition cell 3, defined by two separators 31, 32, is disposed between two electrodes 21, 22.
• the operating principle for the two embodiments of the electroplating device comprises the following steps:
• A. submicron or micron substrates 1 and at least one source 41 of electro-chemically settable material are introduced into an electrolytic solution 40 contained in the cell 3;
• FIG. 3 represents more particularly a device electrodeposition apparatus 3, which comprises an electroplating reactor containing the electrolytic solution 40, the electrodes 21, 22 which dive into the electrolytic solution, and the separators 31, 32 which consist of non-permeable membranes or plates to the substrates. These membranes 31, 32 are arranged between the electrodes 21, 22 so as to define:
• the electroplating cell 3 itself, into which the substrates 1 of an electrically conductive material and the source 41 are introduced to put them in solution,
• a cathode compartment 51 which integrates the electrode serving as cathode 21 and is adjacent to one of the membranes 31, and
• An anode compartment 52 which integrates the electrode serving as anode 22 and is adjacent to the other membrane 32.
• FIG. 4 shows more particularly an electrodeposition device 3, in which the separators 31, 32 are made of a tight material (glass or PLEXIGLAS®). They delimit the electrodeposition cell 3 containing the electrolytic solution 40 and outside of which 3 are disposed contiguously the electrodes 21,22.
• a tight material glass or PLEXIGLAS®
• a difference of potential E of the order of 2 kV between the electrodes is imposed, leading to an electric field E of 100 kVm -1 in the electroplating cell,
• Separators are proton exchange membranes or sintered glass plates.
• the electrodes 21, 22 are immersed in ethanol at -100 ° C. (to compensate for the effects of ohmic heating in the reactor) and at a distance from each other of the order of 2 cm.
• the substrates 1 used are either carbon tubes (images 6A2, 6A2 and 6A3) or vitreous carbon beads (images 6B1, 6B2 and 6B3),
• Electrolytic solutions 40 are aqueous solutions which contain, as a source of electrodepositable material, the following metal salts:
• the electrolyte solution 40 is an agar-agar hydrogel.
• the front substrates (images 6A1 and 6B1) and after electrodeposition synthesis (images 6A2, 6A3, 6B2, 6B3) were observed by scanning electron microscopy (SEM).
• SEM scanning electron microscopy
• Janus monofunctionalized particles were synthesized according to the process of the invention using the electrodeposition device shown in FIG. 3, wherein:
• a difference of potential E of the order of 6 kV is imposed between the electrodes, leading to an electric field E of 20 MV m -1 in the electroplating cell,
• the separators are thin glass walls of 100 m, and separated from each other also by 100 m;
• the substrates 1 used are either carbon tubes
• the electrolytic solution 40 is a hydrogel of agar, which contains as a source of material electrodepositable gold chloride AuCl 4 ⁇ 10 mM (picture
• the separators are proton exchange membranes or sintered glass plates
• the electrodes 21, 22 are immersed in ethanol at -100 ° C. (to compensate for the effects of ohmic heating in the reactor) and at a distance from each other of the order of 2 cm;
• the substrates 1 used are vitreous carbon balls.
• the electrolytic solution 40 is a hydrogel of agar, which contains as a source of material electrodepositable gold chloride AuCl 4 ⁇ 1 mM.
• a first electrolytic solution 40 is prepared consisting of a suspension of Cu 1 in acetonitrile at a rate of 10 mM Cu 1 , into which 0.1 mg carbon tubes are introduced into the suspension;
• a second electrolytic solution 40 comprising 10 mM Cu 1 and 50 mM pyrrole is prepared,
• a potential difference of about 2 kV between the electrodes is imposed;
• Separators are proton exchange membranes
• the formation of a copper deposit on one end of the tubes is generated by reduction of the Cu + cation and the formation of a pyrrole deposit on the other side by oxidation of the pyrrole.
• An electrolytic solution 40 is prepared consisting of a suspension of Cu 1 in acetonitrile at a rate of 10 mM Cu 1 , into which carbon tubes at a rate of 0.1 mg are introduced into the suspension;
• a potential difference is imposed in a pulsed regime with an electric field of 125 MV m -1 in the electroplating cell: depending on the impulses tested varying between 12 s and 30 s, variations in the deposits are observed, with a time interval between the pulses (time of relaxation) of 1 s or 5 minutes;
• Separators are proton exchange membranes
• FIGS. 8a to 8d The bifunctionalized copper / copper modified carbon tubes thus obtained were observed by transmission optical microscopy: in FIGS. 8a to 8d, the visible scale (black lines) is 20 m.
• Figures 8a (with a pulse interval of 5 minutes) and 8b (with a pulse interval of 10s) correspond to a pulse of 12s, while Figures 8c (with a pulse interval of 5 minutes) and 8d (with a pulse interval of 10 s) correspond to a pulse of 30s.
• the particles obtained were also observed using a scanning electron microscope (SEM) (FIG. 9a).
• the separators are sintered glass plates
• the electrodes 21, 22 are immersed in ethanol at -100 ° C. (to compensate for the effects of ohmic heating in the reactor) and at a distance from each other of the order of 4 cm;
• the substrates 1 used are vitreous carbon balls.
• the electrolytic solution 40 is a hydrogel of ethylcellulose in ethanol, which contains as a source of material electrodepositable platinum chloride acid form H 2 PtCl 6 2 ⁇ 5 mM.

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• Chemical & Material Sciences (AREA)
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• Materials Engineering (AREA)
• Metallurgy (AREA)
• Engineering & Computer Science (AREA)
• Dispersion Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
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• Physical Or Chemical Processes And Apparatus (AREA)
• Carbon And Carbon Compounds (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2010
  • 2010-12-22 FR FR1061031A patent/FR2969508B1/fr not_active Expired - Fee Related
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