Diamond electrode for electrochemical applications and provided with a member for connecting to 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 use of the electrode, with an analysis medium; - a metal member (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 flanks of a front portion of the electrode so as to isolate, during use of the electrode, the electrically conductive support (2) and the front portion of the metal member (40) from the analysis medium.

Description

[0001] DESCRIPTION

[0002] TITLE: Diamond electrode for electrochemical applications with a connection element for an electronic board

[0003] TECHNICAL FIELD

[0004] 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.

[0005] PREVIOUS TECHNIQUE

[0006] 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:

[0007] (i) high chemical stability and high corrosion resistance, allowing operation in hostile environments and / or offering a long service life;

[0008] (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;

[0009] (iii) and finally, a low double-layer capacitance enabling higher signal-to-noise ratios, for example in the case of amperometric detection of chemical species.

[0010] Synthetic diamond is manufactured in the laboratory by chemical vapor deposition (CVD) 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 adding diborane or trimethylbore to the gas phase during growth, 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.

[0011] 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 surfaces of several tens or even hundreds of square centimeters. 2To achieve this, a substrate is typically seeded with diamond nanoparticles. These diamond particles will grow until they form a continuous film (or coating) on ​​the surface of the substrate.

[0012] 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, in the range of 600-1200°C.

[0013] It must ensure 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.

[0014] It must have a coefficient of thermal expansion relatively close to that of diamond, otherwise the variations in thermal expansion, particularly during the cooling of the substrate after growth, induce stresses that can lead to the detachment of the diamond layer.

[0015] Traditionally, in most academic laboratories, polycrystalline diamond is deposited on a silicon substrate which meets the above criteria relatively well.

[0016] The chosen silicon substrate can be itself heavily doped (N or P), to allow the diamond electrode to re-establish contact through the back face of the silicon substrate, or undoped, which necessitates re-establishing contact through 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 through the back face on a highly conductive substrate is thus preferred. The thesis by Raphael Kiran, "Diamond Electrodes for the Fabrication of Electrochemical Microsystems for Biological Applications," published by the University of Grenoble in 2012, in French (NNT: 2012GRENI077, tel-00872085), reports a method for fabricating such a diamond electrode.

[0017] According to this method, the diamond is deposited onto a conductive silicon substrate. The back side of the silicon is scraped using a metal rod previously moistened with a eutectic metal (indium / gallium). A copper adhesive is affixed 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 indium / gallium, come into contact to form an electrical connection. This operation eliminates the electrical insulation of the back side due to the presence of a native oxide on the silicon back. Next, the electrode is encapsulated in an epoxy resin to prevent any contact between the copper and the analytical medium. A connection can then be made on the side opposite the diamond electrode using a crocodile clip connector. The electrode can then be immersed in the analytical medium.

[0018] This method is not suitable for industrial production because it is not very robust and requires significant manual assembly. It is also unsuitable for simple electrical connections on electronic circuits.

[0019] Furthermore, silicon substrates present several challenges 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 board for controlling another electrochemical process).

[0020] (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.

[0021] (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 HF acid removal of the oxide, a metallic coating can be applied (for example, Cr / Au, Ti / Au) to solder the substrate to the metal contact.

[0022] Alternative substrates have been used, particularly 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 straightforward, and pretreatments (carburization, deposition of intermediate adhesion layers, etc.) are therefore also necessary.

[0023] Some commercially available diamond electrodes are deposited on metals. These are generally very large surface area electrodes used in water treatment or electrochemical synthesis applications. The large size of the electrodes is what dictates the choice of substrate.

[0024] Thus, Diaccon and Boromond market macroscopic diamond electrodes consisting of metallic plates, grids, etc. (the most common material being niobium) 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.

[0025] 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. Other diamond electrodes are marketed, for example by the company Biologie, also for laboratory applications. These are generally rods 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 to an electronic circuit in the standard way.

[0026] DESCRIPTION OF THE INVENTION

[0027] The problem that the present invention seeks to solve is to have a diamond electrode that can be easily integrated into an electrochemical analysis instrument.

[0028] To solve this problem, the invention proposes an electrode for electrochemical analysis, comprising:

[0029] - an electrically conductive support bearing a layer of diamond intended to be in contact, during the use of the electrode, with an analysis medium;

[0030] - a metallic component having a front part for receiving the electrically conductive support and a rear part for electrical interfacing with an electronic board;

[0031] - 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.

[0032] Some preferred but not limiting aspects of this electrode are the following: - the electrically conductive support is made of a refractory metal, for example tungsten, or silicon doped with boron or phosphorus;

[0033] - the electrically conductive support is welded to the front part of the metal component via a layer of weld;

[0034] - the front part of the metal component includes a cavity for receiving the support;

[0035] - the rear part of the metal component is suitable for being plugged or inserted into the electronic board; - the rear part of the metal component is suitable for being soldered to the electronic board;

[0036] - the chemically inert material is a polymer;

[0037] - the sheath includes a covering portion which covers a peripheral area of ​​the diamond layer.

[0038] Another object relates to a probe for electrochemical analysis comprising at least one electrode as described above, at least one electrode being suitable for connection to an electronic board via the rear electrical interface part of its metallic component.

[0039] The said probe may further include the electronic board connected to at least one electrode.

[0040] Another object concerns a process for manufacturing an electrode for electrochemical analysis, comprising:

[0041] the formation of a diamond layer on an electrically conductive support; the reception of the electrically conductive support on a front part of a metallic component, the metallic component having a rear part for electrical interfacing to an electronic board;

[0042] 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.

[0043] Some preferred, but not exhaustive, aspects of this process are as follows:

[0044] - The formation of the diamond layer on the substrate comprises the following successive steps:

[0045] o a deposit of the diamond layer over the entire surface of a substrate;

[0046] o a cutting of a portion of the substrate. It includes a pre-cutting of pellets of the substrate before the deposition of the diamond layer on the entire surface of a substrate, for example by water cutting or by chemical etching;

[0047] It also 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;

[0048] The positioning of the sheath involves crimping or hot deposition.

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Other aspects, objectives, advantages, and features of the invention will become clearer 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:

[0051] - Figure 1 is a diagram of an electrode according to the invention;

[0052] - Figure 2 is a diagram illustrating the use of an electrode according to the invention and the role of the sheath made of a chemically inert material;

[0053] - Figure 3A is a diagram of a possible embodiment of a metallic component for an electrode according to the invention;

[0054] - Figure 3B is a diagram of an electrode according to the invention using the metallic element of Figure 3A;

[0055] - Figure 4A is a cross-sectional and profile view of a probe equipped with two electrodes according to the invention;

[0056] - Figures 4B and 4C are top views of the probe in Figure 4A, respectively without and with probe housing;

[0057] - Figure 5 is a diagram of a pre-cut substrate that can be used in the manufacture of electrodes according to the invention;

[0058] Figure 6 illustrates different stages of a manufacturing process for an electrode according to the invention. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0059] 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.

[0060] With reference to Figure 1, the electrode 1 according to the invention comprises 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 (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 20 and 3xlO 21 at. cm'3 . Support 2 and 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.

[0061] 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. 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 based on these same metals or an alloy containing more than 50% of these same metals (example: tungsten 66% / copper 44%). Support 2 may also be made of silicon, preferably heavily doped (conductivity typically < 100 Ω·cm), for example with boron or phosphorus.

[0062] Electrode 1 also includes 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.).

[0063] The front portion of the metal component 4 preferably includes a planar surface for welding the support 2 to the metal component 4. In one embodiment, the support 2 is welded to the front portion of the metal component 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 radiofrequency 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).

[0064] 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.

[0065] The rear portion of the metal component 4 can be adapted to be inserted or plugged into the electronic board, taking the form of a pin or an electrical connector. As shown in Figure 4A, the rear portion of the metal component can take the form of a male plug adapted to be received into a female connector on the electronic board.

[0066] 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.

[0067] Referring again to Figure 1, the electrode also includes 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.

[0068] The sleeve 6 has a geometry that matches that of the electrode's front section. Thus, when the electrode has a circular shape, the sleeve takes the form of a cylindrical tube that encloses the electrode's front section. Positioning the sleeve on the electrode's front section can involve crimping (using a press, for example) or hot deposition.

[0069] 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.

[0070] 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.

[0071] The electrode is connected, via the rear portion of the metallic component 4, to an electronic circuit board 7 of a measuring probe in an electrochemical analysis device. It passes through the surface 8 of the probe housing so that its front portion, and in particular the diamond layer 3, is in contact with the analytical medium MA, while its rear portion is in the air within the housing. As shown, the sheath 6 isolates any non-diamond conductive parts from the analytical medium MA. Indeed, if another electrically conductive material (metal, silicon) were to come into contact with the analytical medium, it would itself constitute an electrode that could potentially induce parasitic currents, impairing the measurement or causing 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).

[0072] 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 equipped with a cavity for receiving the support bearing 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.

[0073] 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 front part FP of the element 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 sleeve 6 thus takes the form of a cap having an opening on its upper face, an opening allowing access of the surface of the diamond layer 3 to the analysis medium.

[0074] The invention finds application in an electrochemical analysis probe 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. The probe may, in particular, 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.

[0075] 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.

[0076] Thus, two diamond electrodes are plugged onto the electronic board 7 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.

[0077] This design example is particularly well-suited to automated chemical analysis using a sample changer (or carousel). The goal is to automatically transport two diamond electrodes (a working electrode and a counter electrode) and sequentially immerse them in different samples for analysis. These electrodes are miniaturized to allow for the analysis of small sample volumes. It is worth noting that integrating two diamond electrodes onto a probe is greatly facilitated by the ability to interface these two electrodes on an electronic circuit board.

[0078] The invention also relates to a method for manufacturing an electrode according to the invention. This method comprises:

[0079] the formation of a diamond layer on a substrate;

[0080] the reception of the support on a front part of a metallic component, the metallic component having a rear part for electrical interface to an electronic board;

[0081] The positioning of a sheath made of a chemically inert material so that the sheath encloses the sides of a front portion of the electrode and allows, during electrode use, the isolation of the metallic support and the front portion of the metallic component from an analytical medium in contact with the diamond layer. 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.

[0082] 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.

[0083] 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.

[0084] Finally, the sheath positioning involves crimping or hot deposition. A first example of this process uses a 0.5 mm thick tungsten plate as a substrate, with the cut pellet being, for example, a circular disc 3 mm in diameter. This pellet can then be positioned in the cavity of the metallic component shown in Figure 3A.

[0085] Tungsten is chosen here because after various tests it proves to be the material to 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.

[0086] The invention extends, however, to the implementation of such pretreatment as, for example, plasma treatment of the substrate and / or roughening of the substrate surface and / or deposition of an intermediate adhesion layer on the substrate surface.

[0087] In the example shown, the substrate is cleaned in an ultrasonic bath, successively in acetone, isopropanol, and deionized water, 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 diamond's adhesion to the support after the growth stage.

[0088] This same substrate is then seeded with diamond nanoparticles with an average size of 30 nm. This step is carried out using 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 rinsing, in a colloidal solution of nanodiamonds with a surface charge opposite to that of the polyelectrolyte. The nanodiamonds then attach to the substrate through electrostatic interactions.

[0089] The substrate is then placed back into the same growth reactor in which a thin layer of boron-doped diamond (doping ~2x20) is added. 21 at.B.crrr 3 ) of approximately 2 microns thickness is raw on the same substrate.

[0090] In one possible embodiment, the process may include, after full-plate deposition of the diamond layer onto the substrate and before pellet cutting, the formation of a solder layer on one back face of the substrate. For this purpose, the substrate can 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 back face not containing diamond.

[0091] 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 Figure 5, the process then involves pre-cutting the substrate into pellets P before the full-plate deposition of the diamond layer, for example, by laser cutting or waterjet cutting. This pre-cutting retains detachable holding zones Z, which will be cut, for example, by laser cutting or waterjet cutting, during the final pellet cutting.

[0092] Another example of this process, illustrated in Figure 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.

[0093] Then, during a third operation (c) of this process, a full-plate layer of diamond 33 is deposited onto one 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), then, after rinsing, 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 by electrostatic interactions. The plate 1 is then placed back in the growth reactor, in which a thin layer of diamond 33 is grown, for example, a boron-doped diamond thin layer (doping ~2x20). 21 at.B.crrr 3) and 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, as shown in Figure 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.

[0094] In 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.

[0095] This fourth operation (d) preferably comprises the formation of a structured solder layer 34 on the back side of the wafer 30. The structured solder layer consists of portions aligned vertically with the silicon pads 32, which are coated with the diamond layer 33. For this purpose, the wafer 30 can be placed in an RF plasma-assisted magnetron sputtering apparatus in which, for example, a 30 nm metallic layer of chromium followed by a 100 nm layer of gold are deposited on the back side of the wafer. 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.

[0096] 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 pads. 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.

[0097] In parallel with this process, the metal component is manufactured. For example, this might be 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 its upper surface. This cavity allows the pad to be centered on 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 an annealing process.

[0098] Finally, a sheath, for example made of Teflon™, is pressed onto the upper part of the electrode to achieve electrical insulation between the measuring solution and the metal 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, when using the electrode, with an analysis medium (MA); a metallic element (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) made of a chemically inert material, the sheath enclosing sides of a front part of the electrode so as to isolate, when using 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 element (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 for 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 sheath (6) in 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 (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, in succession: a deposition of the diamond layer over the entire surface of a substrate; a cutting of a portion of the substrate.

13. 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.

Images