Diamond electrode for electrochemical applications equipped with a connection element for an electronic board

Abstract

The invention relates to an electrode (10) for electrochemical analysis, comprising: an electrically conductive support (2) bearing a diamond layer (3) intended to be in contact, during the use of the electrode, with an analytical medium; a metallic element (4, 40) having a front portion for receiving the electrically conductive support and a rear portion for electrical interfacing with an electronic board; a sheath (6) made of a chemically inert material, the sheath enclosing the sides of a front portion of the electrode so as to isolate, during the use of the electrode, the electrically conductive support (2) and the front portion of the metallic element (40) from the analytical medium. Figure 3B

Description

Title of the invention: Diamond electrode for electrochemical applications equipped with a connection element for an electronic board. Technical field

[0001] The field of the invention is that of electrochemical analysis. The invention relates more particularly to a diamond electrode intended for use in an electrochemical analysis probe. Previous technique

[0002] There is a growing interest in the use of synthetic diamond electrodes for electrochemical applications. Indeed, when doped with boron, synthetic diamond exhibits remarkable electrochemical properties, including: i. high chemical stability and high corrosion resistance, allowing operation in hostile environments and / or offering a long service life; ii. a large potential window in aqueous medium (>3V), allowing for example to oxidize or reduce a wider range of chemical species than with other electrode materials, for the purpose of detecting or destroying them in the case of pollution control; iii. and finally, a low double-layer capacitance allowing higher signal-to-noise ratios, for example in the case of amperometric detection of chemical species.

[0003] Synthetic diamond is manufactured in the laboratory by chemical vapor deposition via epitaxy, in a plasma containing hydrogen and most often methane as a carbon source. In the case of electrodes, this diamond is doped with boron by the addition, during growth, of diborane or trimethylbore in the gas phase, for example. Two growth methods are possible: the so-called "hot-filament chemical vapor deposition" (HF-CVD) method or the microwave plasma-assisted chemical vapor deposition (MP-CVD) method.

[0004] Polycrystalline diamond is generally preferred for electrochemical applications because it is easier and less expensive to produce than monocrystalline diamond. In particular, it is possible to deposit polycrystalline diamond onto certain substrates over areas of several tens or even hundreds of square centimeters. To achieve this, a substrate is generally seeded with diamond nanoparticles. These diamond particles will grow until they form a continuous film (or coating) on ​​the surface of the substrate.

[0005] The substrate used for growth must meet certain criteria, in particular: - It must be able to withstand the high temperatures to which it is exposed during diamond growth, on the order of 600-1200°C. - It must allow for good adhesion of the diamond film to the surface. Generally, this is promoted by the formation of a carbide at the interface, enabling a covalent chemical bond between the diamond and the substrate. Adhesion can also be enhanced by a high substrate roughness. - It must have a coefficient of thermal expansion relatively close to that of diamond, otherwise the variations in thermal expansion, in particular during the cooling of the substrate after growth, induce stresses which can lead to the detachment of the diamond layer.

[0006] Traditionally, in most academic laboratories, polycrystalline diamond is deposited on a silicon substrate which meets the above criteria relatively well.

[0007] The chosen silicon substrate can itself be heavily doped (N or P), to allow the diamond electrode to re-establish contact via the back face of the silicon substrate, or undoped, which necessitates re-establishing contact via the top of the diamond layer. The latter case is less favorable because diamond, even heavily doped, exhibits significant foil resistance, which adds a series resistance and therefore an ohmic drop phenomenon in the final electrochemical measurement device. Contact via the back face on a highly conductive substrate is therefore preferred.

[0008] The thesis by Raphaël Kiran. Diamond electrodes for the fabrication of microelectrochemical systems for biological applications. Other. University of Grenoble, 2012. French. NNT: 2012GRENI077. tel-00872085 reports a method for manufacturing such a diamond electrode.

[0009] According to this method, the diamond is deposited on a conductive silicon substrate. The back face of the silicon is scraped using a metal rod previously moistened with a eutectic metal (indium / gallium). A copper adhesive is glued to a glass slide and also scraped with the same metal rod. The piece of silicon is then placed on the copper adhesive so that the two silicon and copper surfaces moistened with the indium / gallium come into contact to form an electrical contact. This operation eliminates the electrical insulation of the back face due to the presence of a native oxide on the silicon back face. Next, the electrode is encapsulated in an epoxy resin to prevent any contact between the copper and the analytical medium. Contact can then be made on the side opposite the diamond electrode via a "crocodile clip" type connector. The electrode can then be immersed in the analysis medium.

[0010] Such a method is not suitable for industrialization because it is not very robust and requires significant manual assembly. It is also not suitable for a simple electrical connection on an electronic circuit.

[0011] Furthermore, silicon substrates present a number of difficulties when it comes to integrating electrodes into a measurement device. Integration refers to connecting the electrode to an electronic measurement acquisition board (or possibly a control board for another electrochemical process). i. First, because silicon is a crystalline material, cutting the substrate into specific shapes (e.g., circular disks) can be complex. Silicon is not easily machined, even by laser cutting. To obtain small custom silicon geometries, it is generally necessary to use photolithography / etching techniques. ii. Silicon cannot be soldered. Furthermore, the formation of a native oxide (SiOx) on the back side (a natural phenomenon) passivates the surface, making it insulating. Connecting a silicon substrate to an electrical contact (for example, a metal pad on a printed circuit board) therefore requires, firstly, the removal of the native oxide beforehand (most often by etching in HF acid) and, secondly, bonding this substrate to the metal pad using, for example, a conductive resin (gold or silver paste, eutectic liquid, etc.). Optionally, after removing the oxide with HF, a metallic coating can be applied (for example, Cr / Au, Ti / Au) to solder the substrate to the metal contact.

[0012] Alternative substrates have been used, in particular metallic substrates. These substrates must withstand the same constraints as those mentioned previously (temperature resistance, surface carbide formation, thermal expansion close to that of diamond, etc.). Among the potentially suitable metals, refractory metals such as tungsten, niobium, tantalum, and molybdenum are generally cited in the literature. However, experience shows that diamond adhesion to such substrates is not trivial, and pretreatments (carburizing, deposition of intermediate adhesion layers, etc.) are therefore also necessary.

[0013] Some commercially available diamond electrodes are deposited on metals. These are generally very large surface area electrodes for water treatment or electrochemical chemical synthesis applications. It is the large size of the electrodes that justifies the choice of substrate.

[0014] Thus, the companies Diaccon and Boromond market macroscopic diamond electrodes which consist of metallic plates, grids, etc. (Niobium being the most common material) coated with diamond. These electrodes are not suitable for integration into an electronic circuit. The electrodes are generally immersed by the end user, who also performs the connection and insulation.

[0015] Origalys, for its part, markets diamond electrodes in the form of pellets that must be assembled in a dedicated sample holder. Again, these electrodes are not suitable for integration onto electronic boards. They are intended primarily for research and development purposes and are typically designed to be immersed in a beaker or a laboratory electrochemical cell.

[0016] Other diamond electrodes are commercially available, for example from the company Biologie, also for laboratory applications. These generally consist of a rod several centimeters long with a diamond pellet on one end and a connector plug on the other. This type of device is not miniaturized and cannot be connected in a standard way to an electronic circuit. Description of the invention

[0017] The problem that the present invention seeks to solve is to be able to have a diamond electrode that can be easily integrated into an electrochemical analysis instrument.

[0018] To solve this problem, the invention proposes an electrode for electrochemical analysis, comprising:

[0019] - an electrically conductive support carrying a diamond layer intended to be in contact, during the use of the electrode, with an analysis medium;

[0020] - a metallic component having a front portion for receiving the support electrical conductor and a rear electrical interface part to an electronic board;

[0021] - a sheath made of a chemically inert material, the sheath enclosing the sides of a front part of the electrode so as to isolate, when using the electrode, the electrically conductive support and the front part of the metallic component from the analysis medium.

[0022] Some preferred but not limiting aspects of this electrode are as follows:

[0023] - the electrically conductive support is made of a refractory metal, for example in tungsten, or silicon doped with boron or phosphorus;

[0024] - the electrically conductive support is welded to the front part of the metal component through a weld layer;

[0025] - the front part of the metal component includes a cavity for receiving the support;

[0026] - the rear part of the metal component is suitable for being skewered or plugged into the electronic card;

[0027] - the rear part of the metal component is suitable for being welded to the electronic board;

[0028] - the chemically inert material is a polymer;

[0029] - the sheath includes a covering portion which covers an area peripheral to the diamond layer.

[0030] Another object relates to a probe for electrochemical analysis comprising at least one electrode as described above, at least one electrode being able to be connected to an electronic board via the rear electrical interface part of its metallic element.

[0031] Said probe may further include the electronic board connected to at least one electrode.

[0032] Another object relates to a method for manufacturing an electrode for electrochemical analysis, comprising: - the formation of a diamond layer on an electrically conductive support; - the reception of the electrical conductive support on a front part of a metallic component, the metallic component having a rear part for electrical interface to an electronic board; - the positioning of a sheath made of a chemically inert material so that the sheath encloses the sides of a front part of the electrode and allows the electrically conductive support and the front part of the metallic element to be isolated, when using the electrode, from an analysis medium in contact with the diamond layer.

[0033] Some preferred but not limiting aspects of this process are as follows:

[0034] - the formation of the diamond layer on the support comprises in succession: • a deposit of the diamond layer over the entire surface of a substrate; • a cutting of a portion of the substrate. • it includes pre-cutting pellets of the substrate before depositing the diamond layer over the entire surface of a substrate, for example by waterjet cutting or chemical etching; • it further includes, after the deposition of the diamond layer over the entire surface of a substrate and before cutting the portion of the substrate, the formation of a weld layer on a back face of the substrate; • the positioning of the sheath includes crimping or hot deposition. Brief description of the drawings

[0035] Other aspects, objects, advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0036] - [Fig.1] is a diagram of an electrode according to the invention;

[0037] - [Fig. 2] is a diagram illustrating the use of an electrode according to the invention and the role of the sheath in a chemically inert material;

[0038] - [Fig. 3A] is a diagram of a possible embodiment of a metallic component for an electrode conforming to the invention;

[0039] - [Fig. 3B] is a diagram of an electrode according to the invention using the organ metallic of the [Fig.3A];

[0040] - [Fig. 4A] is a cross-sectional and side view of a probe equipped with two electrodes conforming to the invention;

[0041] - Figures 4B and 4C are top views of the probe of [Fig.4A] respectively without and with probe housing;

[0042] - [Fig. 5] is a diagram of a pre-cut substrate that can be used in the manufacturing of electrodes conforming to the invention;

[0043] - Figure 6 illustrates different stages of a manufacturing process for an electrode according to the invention.

[0044] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0045] The invention relates to a diamond electrode for electrochemical applications. The electrode is more particularly intended to be integrated into a measuring probe of an electrochemical analysis device.

[0046] With reference to [Fig. 1], the electrode 1 according to the invention comprises an electrically conductive support 2 carrying a diamond layer 3 intended to be in contact, during the use of the electrode, with an analytical medium (electrolytic solution such as, for example, a biological fluid). The diamond layer 3 is typically a thin layer of boron-doped polycrystalline diamond. The diamond layer typically has a thickness of between 200 nm and 100 pm. The boron doping level is typically between 10 and 3 x 10 at.cm. The support 2 and the diamond layer 3 preferably have a circular geometry when viewed from above, although this is not a limitation; a hexagonal or square shape could also be used, for example.

[0047] The electrically conductive support 2 may have served as a growth support, by chemical vapor deposition (typically by MP-CVD or HF-CVD), for the diamond layer 3. The support 2 is preferably a metallic support, even more preferably a support made of a refractory material such as, for example, tungsten, niobium, tantalum, molybdenum or rhenium, or any alloy with The base of these same metals or an alloy containing more than 50% of these same metals (example: tungsten 66% / copper 44%). Support 2 can also be made of silicon, preferably heavily doped (conductivity typically < 100 Ω·cm), for example with boron or phosphorus.

[0048] The electrode 1 further comprises a metallic element 4 having a front portion for receiving the support 2 and a rear portion for electrical interfacing with an electronic board. The metallic element may be made of brass, copper, or any other metal meeting the specifications of an electrical connector as known to those skilled in the art (gold-plated brass, etc.).

[0049] The front portion of the metal member 4 preferably comprises a planar surface for welding the support 2 to the metal member 4. In one embodiment, the support 2 is welded to the front portion of the metal member 4 via a weld layer 5. This weld layer 5 may consist of a metallic layer deposited on the rear face of the support (i.e., the face of the support opposite the front face of the support bearing the diamond layer 3). This metallic layer may be composed of gold and optionally include a chromium or titanium sublayer to promote the adhesion of the gold to the support. These Cr / Au, Ti / Au, etc. layers may be deposited, for example, by evaporation or by radio-frequency plasma-assisted sputtering.In the case where the support 2 is made of silicon, it is necessary, before depositing this solder layer 5, to remove the native oxide layer SiOx on the back face of the silicon, for example by exposure to hydrofluoric acid (HF).

[0050] In a preferred embodiment illustrated in Figures 3A, 3B and 4A, the front part of the metallic member 4 includes a cavity for receiving the support. This cavity is preferably centered so that the diamond layer is aligned with the center of the electrode.

[0051] The rear portion of the metal member 4 can be adapted to be inserted or plugged into the electronic board, taking the form of a pin or an electrical connection plug. As shown in [Fig. 4A], the rear portion of the metal member can take the form of a male plug adapted to be received in a female connector of the electronic board.

[0052] Alternatively, the rear part of the metal component 4 can take the form of an electrical connection pad suitable for being soldered to the electronic board or connected to it by spring contact.

[0053] With further reference to [Fig. 1], the electrode also comprises a sheath 6 made of a chemically inert material. The sheath 6 encloses the sides of a front portion of the electrode 1 so as to isolate, during the use of the electrode, the support 2 and the front portion of the metallic element 4 from the analytical medium.

[0054] The sleeve 6 has a geometry that conforms to that of the front part of the electrode. Thus, when the electrode has a circular geometry, the sleeve takes the form of a cylindrical tube that encloses the front part of the electrode. The positioning of the sleeve on the front part of the electrode can involve crimping (using a press, for example) or hot deposition.

[0055] The chemically inert material can be a polymer, for example PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy), PEEK (polyetheretherketone), polyimide or any other material compatible with the conditions of use.

[0056] Figure 2 shows a diagram illustrating the use of an electrode according to the invention and the role of the sheath made of a chemically inert material.

[0057] The electrode is connected here, by means of the rear portion of the metallic member 4, to an electronic circuit board 7 of a measuring probe in an electrochemical analysis device. It passes through the surface 8 of a probe housing such that its front portion, and in particular the diamond layer 3, is in contact with the analysis medium MA, while its rear portion is in the air contained within the housing. As shown, the sheath 6 isolates any non-diamond conductive part(s) from the analysis medium MA. Indeed, if another electrically conductive material (metal, silicon) were to come into contact with the analysis medium, it would itself constitute an electrode that could potentially induce parasitic currents that would interfere with the measurement or cause premature degradation of the device.On the other hand, the sheath 6 also ensures insulation between the front part of the electrode and the rear part of the metallic component, thus preventing the introduction of liquid into the electrochemical analysis device in contact with or near the electronic elements (in particular the electronic board 7).

[0058] Figure 3A shows a cross-sectional diagram of a possible embodiment of a metallic element 40 for an electrode according to the invention. This metallic element comprises a rear portion BP for electrical interfacing, here in the form of a cylindrical male plug (diameter 2.2 mm and height 2.2 mm), and a front portion FP, here having a cavity for receiving the support carrying the diamond layer. The front portion FP also has a cylindrical geometry (diameter 4.4 mm and height 2.2 mm), with a cylindrical cavity of 3.1 mm diameter and 0.5 mm height.

[0059] Figure 3B shows a cross-sectional view of an electrode 10 according to the invention using the metal element 40 of Figure 3A. The support 2 for the diamond layer 3 is housed in the cavity and welded to the front part of the metal element by means of the weld layer 5. In this embodiment, the sleeve 6 includes not only a portion 61 covering the lateral sides of the front part of the electrode (in this case, the sides of the part before FP of organ 40) but also a portion 62 covering a peripheral area of ​​the surface of the diamond layer 3 which can typically cover up to 1 / 3 of this surface. The sheath 6 therefore takes the form of a cap with an opening on its upper face, an opening allowing access from the surface of the diamond layer 3 to the analysis medium.

[0060] The invention finds application in a probe for electrochemical analysis comprising at least one electrode according to the invention, adapted to be connected to the electronic board via the rear electrical interface portion of its metallic component. The probe may include the electronic board, the latter being connected to at least one electrode via the rear electrical interface portion of said at least one electrode. In particular, the probe may include two electrodes according to the invention, each adapted to be connected to the electronic board via the rear electrical interface portion of its respective metallic component.

[0061] An example of an embodiment of such a probe is shown in Figures 4A-4C. In this example, the probe 20 comprises a housing 8 inside which is housed an electronic board 7 on the surface of which extend two metal tracks 9. Each of the metal tracks joins a female connector 11 configured to receive the rear interface part in the form of a male plug of a metal element of an electrode 10 according to the invention.

[0062] Thus, two diamond electrodes are plugged onto the electronic board 7 located inside the housing 8. The sheath 6 makes the probe watertight at the housing when the lower part of the probe is immersed in the analysis medium.

[0063] This embodiment is advantageously applied to automated chemical analysis using a sample changer (or carousel). The aim here is to automatically transport two diamond electrodes (a working electrode and a counter electrode) and sequentially immerse them in different samples to be analyzed. These electrodes are miniaturized to allow the analysis of small sample volumes. It should be noted that the integration of two diamond electrodes onto a probe is greatly facilitated by the possibility of interfacing these two electrodes on an electronic board.

[0064] The invention also relates to a method for manufacturing an electrode according to the invention. This method comprises: - the formation of a diamond layer on a substrate; - the reception of the support on a front part of a metallic component, the component metallic having a rear part for electrical interfacing to an electronic board; - the positioning of a sheath made of a chemically inert material so that the sheath encloses the sides of a front part of the electrode and allows the metallic support and the front part of the metallic element to be isolated from an analysis medium in contact with the diamond layer when using the electrode.

[0065] In one possible embodiment, the formation of the diamond layer on the support comprises, in succession, a full plate deposition (i.e. over the entire surface of the substrate) of a diamond layer on a substrate and the cutting of a pellet consisting of a portion of the substrate coated with the diamond layer.

[0066] As exemplified below, the process may include pre-cutting pellets of the substrate before depositing the diamond layer over the entire surface of a substrate, for example by waterjet cutting or chemical etching.

[0067] The process may also include, after the deposition of the diamond layer over the entire surface of the substrate and before cutting the portion of the substrate, the formation of a weld layer on a back face of the substrate.

[0068] Finally, the positioning of the sheath includes crimping or hot deposition.

[0069] A first example of an embodiment of this process uses a 0.5 mm thick tungsten plate as a substrate, the cut pellet being, for example, a circular disc 3 mm in diameter. This pellet can thus be positioned in the cavity of the metallic element of [Fig. 3A].

[0070] Tungsten is chosen here because after various tests it proves to be the material on which diamond adheres best among the materials tested (Titanium, Niobium, Tantalum) under the conditions used in the example presented here and in the absence of any specific pretreatment aimed at improving adhesion.

[0071] The invention extends however to the implementation of such pretreatment as for example a plasma treatment of the substrate and / or a roughening of the surface of the substrate and / or the deposition of an intermediate adhesion layer on the surface of the substrate.

[0072] In the example shown, the substrate is cleaned in an ultrasonic bath successively in acetone, isopropanol, and then deionized water, and then dried with a stream of nitrogen or compressed air. The substrate is then placed in an MP-CVD diamond growth reactor and subjected to a plasma containing 5% methane in hydrogen for one hour under the following conditions: gas pressure 40 Torr, microwave plasma power 4 kW. This pretreatment allows for carburization of the substrate and thus strengthens the adhesion of the diamond to the support after the growth step.

[0073] Then this same substrate is seeded with diamond nanoparticles with an average size of 30 nm. This step is carried out according to a process known to those skilled in the art, consisting of successive baths first in a solution containing a A loaded polymer (polyelectrolyte) is then rinsed in a colloidal solution of nano-diamonds with a surface charge opposite to that of the polyelectrolyte. The nano-diamonds then attach to the support via electrostatic interactions.

[0074] The substrate is then placed back in the same growth reactor in which a thin layer of boron-doped diamond (doping ~2x2021 at.B.cm3) of about 2 microns thickness is grown on the same substrate.

[0075] In one possible embodiment, the process may include, after full-plate deposition of the diamond layer on the substrate and before cutting the pellet, the formation of a solder layer on a rear face of the substrate. For this purpose, the substrate may be placed in an RF plasma-assisted magnetron sputtering apparatus in which 30 nm chromium and then 100 nm gold metallic layers are deposited on the rear face not containing diamond.

[0076] In a preferred embodiment, the diamond layer is grown on a pre-machined substrate to allow for the easy extraction of individual pellets after growth, thus enabling mass production of the electrodes. As shown in [Fig. 5], the process then includes pre-cutting pellets P from the substrate before the full-plate deposition of the diamond layer, for example by laser cutting or waterjet cutting. This pre-cutting preserves detachable holding zones Z which will be cut, for example by laser cutting or waterjet cutting, during the final pellet cutting.

[0077] Another embodiment of this process, illustrated in [Fig. 6], uses a silicon wafer as a substrate. A first step (a) of this process consists of supplying this silicon wafer 1, for example, a circular wafer with a diameter of 10 cm and a thickness typically between 350 µm and 1000 µm. A second step (b) of this process consists of pre-cutting the silicon wafer 1 by photolithography and chemical etching methods (for example, DRIE, an acronym for "Deep Reactive Ion Etching") to form cavities 31 extending deep into the wafer 1, for example, to half the thickness of the wafer 30. The cavities 31 define silicon pads 32, which take, for example, the form of circular pads with a diameter of 3 mm.

[0078] Then, during a third operation (c) of this process, a full-plate diamond layer 33 is deposited on a front face of the plate 30. To do this, the plate can be seeded with diamond nanoparticles having, for example, an average size of 30 nm. This seeding is carried out according to a process known to those skilled in the art, consisting of successive baths first in a solution containing a charged polymer (polyelectrolyte) and then after The plate is rinsed in a colloidal solution of nano-diamonds having a surface charge opposite to that of the polyelectrolyte. The nano-diamonds then attach to the support via electrostatic interactions. The plate 1 is then placed back in the growth reactor where a thin layer of diamond 33 is grown, for example, a boron-doped diamond thin layer (doping ~2 x 2021 at.B.cm3) approximately 2 microns thick. It should be noted that the diamond layer 33 covers the sides of the pads 32, so that it will ultimately be found, see [Fig. 3B], on the sides of the support 2 of the diamond layer 3 of an electrode according to the invention. This results in improved resistance of the diamond layer to detachment. The plate 30 is then subjected to an HF treatment to remove the native silicon oxide layer present on the back face of the plate.

[0079] During a fourth operation (d), the process includes the formation of a weld layer 34 on the back face of the plate 30. The weld layer preferably comprises a layer of a corrosion-resistant noble metal (e.g., gold or platinum) associated with a layer of a metal (e.g., chromium or titanium) facilitating the adhesion of the noble metal layer to the plate 30.

[0080] This fourth operation (d) preferably comprises the formation of a structured solder layer 34 on the rear face of the plate 30. The structured solder layer consists of portions aligned vertically with the silicon pads 32 covered by the diamond layer 33. For this purpose, the plate 30 can be placed in an RF plasma-assisted magnetron sputtering device in which, for example, a 30 nm metallic layer of chromium followed by a 100 nm layer of gold are deposited on the rear face of the plate. The structuring, carried out by photolithography, can thus consist of forming Cr / Au disks with a diameter of 3 mm aligned vertically with the silicon pads 32.

[0081] During a fifth operation (e), the rear face of the plate 30 is subjected to an etching, for example a DRIE etching, aimed at separating the diamond electrode 33 / silicon 30 / weld 34 pellets. The structured weld layer 34 is used here to serve as a mask for the etching, allowing only the unmasked silicon areas exposed to the etching plasma to be etched.

[0082] In parallel with this process, the metal component is manufactured. For example, it is a cylindrical brass component machined in such a way that a cavity slightly larger than the diameter of the electrode pad (tungsten / diamond / solder or silicon / diamond / solder) is present on the upper part to accommodate this pad centered with respect to the vertical axis of the metal component. The pad can then be soldered into the upper cavity of the metal component using solder paste and annealing.

[0083] Finally, a sheath, for example made of Teflon™, is crimped onto the upper part of the electrode using a press in order to achieve electrical insulation between the measuring solution and the metallic part under the diamond layer, and possibly facilitate the sealing of a device using such electrodes.

Claims

Demands

1. Electrode (1, 10) for electrochemical analysis, comprising: - an electrically conductive support (2) carrying a diamond layer (3) intended to be in contact, during the use of the electrode, with an analysis medium (MA); - a metallic member (4, 40) having a front part (FP) for receiving the electrically conductive support and a rear part (BP) for electrical interfacing with an electronic board; - a sheath (6) of a chemically inert material, the sheath enclosing sides of a front part of the electrode so as to isolate, during the use of the electrode, the electrically conductive support (2) and the front part (FP) of the metallic member (4, 40) from the analysis medium.

2. Electrode according to claim 1, wherein the electrically conductive support (2) is made of a refractory metal, for example tungsten, or silicon doped with boron or phosphorus.

3. Electrode according to claim 2, wherein the electrically conductive support (2) is welded to the front part (FP) of the metallic member (4, 40) via a weld layer (5).

4. Electrode according to any one of claims 1 to 3, wherein the front part (FP) of the metallic member (4, 40) comprises a cavity for receiving the electrically conductive support.

5. Electrode according to any one of claims 1 to 4, wherein the rear part (BP) of the metallic member (4, 40) is suitable for being plugged or inserted into the electronic board (7).

6. Electrode according to any one of claims 1 to 4, wherein the rear part (BP) of the metallic member (4, 40) is suitable for being welded to the electronic board (7).

7. Electrode according to any one of claims 1 to 6, wherein the chemically inert material is a polymer.

8. Electrode according to any one of claims 1 to 7, wherein the sheath (6) includes a cover portion (62) which covers a peripheral area of ​​the diamond layer (3).

9. Electrochemical analysis probe (20) comprising at least one electrode (1, 10) according to any one of claims 1 to 8, at least one electrode being able to be connected to an electronic board via the rear (BP) electrical interface part of its metallic member (4, 40).

10. Probe according to claim 9, further comprising an electronic card (7) connected to at least one electrode (1, 10) by the rear (BP) electrical interface part of said at least one electrode.

11. Method of manufacturing an electrode (1) for electrochemical analysis, comprising: - the formation of a diamond layer (3) on an electrically conductive support (2); - the reception of the electrically conductive support (2) on a front part (FP) of a metallic element (4, 40), the metallic element having a rear part (BP) for electrical interfacing to an electronic board; - the positioning of a sleeve (6) of a chemically inert material so that the sleeve encloses the sides of a front part of the electrode and allows the electrically conductive support and the front part of the metallic element to be isolated, during the use of the electrode, from an analysis medium (MA) in contact with the diamond layer.

12. A method according to claim 11, wherein the formation of the diamond layer on the support comprises successively: - a deposition of the diamond layer over the entire surface of a substrate; - a cutting of a portion of the substrate.

13. A method according to claim 12, comprising pre-cutting pellets of the substrate before depositing the diamond layer over the entire surface of a substrate, for example by waterjet cutting or chemical etching.

14. A method according to any one of claims 12 and 13, further comprising, after the deposition of the diamond layer over the entire surface of a substrate and before cutting the portion of the substrate, the formation of a weld layer on a back face of the substrate.

15. A method according to any one of claims 11 to 14, wherein the positioning of the sheath comprises crimping or hot deposition.

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