Diamond electrode

Abstract

A diamond electrode comprises: a conductive diamond element in rod form; and a metal element in rod form which is electrically connected to the conductive diamond element, wherein the diamond content of the conductive diamond element is 80 vol.% or more.

Description

Technical field

[0001] The present disclosure relates to a diamond electrode. The present application claims priority based on Japanese patent application No. 2023-115406, filed on July 13, 2023. The entire contents of the Japanese patent application are hereby incorporated by reference. State of the art

[0002] Conductive diamond possesses outstanding properties such as high electrical and thermal conductivity, high hardness, and high resistance to acids and alkalis. A technique has been considered in which conductive diamond is used as an electrode, taking advantage of these properties.

[0003] For example, PTL 1 discloses a diamond electrode in which a thin layer of fine diamond grains is applied to a base material made of a metal wire. List of cited writings Patent literature

[0004] PTL 1: Japanese Patent Publication No. 2011-174822 Overview of the invention

[0005] A diamond electrode according to the present disclosure is a diamond electrode comprising: a conductive diamond element in rod form; and a metal element in rod form that is electrically connected to the conductive diamond element, wherein The diamond content of the conductive diamond element is 80 vol.% or more. Brief description of the drawings [ Fig. 1] Fig. Figure 1 is a diagram illustrating a representative exemplary structure of a diamond electrode according to a first embodiment. [ Fig. 2A] Fig. 2A is a cross-sectional view along a line II in Fig. 1. [ Fig. 2B] Fig. Figure 2B is a side view of a diamond element of the diamond electrode according to the first embodiment. [ Fig. 3A] Fig. Figure 3A is a diagram illustrating a method for manufacturing the diamond electrode according to the first embodiment. [ Fig. 3B] Fig. Figure 3B is a diagram illustrating the method for manufacturing the diamond electrode according to the first embodiment. [ Fig. 3C] Fig. Figure 3C is a diagram illustrating the process for manufacturing the diamond electrode according to the first embodiment. [ Fig. 3D] Fig. 3D is a diagram illustrating the process for manufacturing the diamond electrode according to the first embodiment. [ Fig. 3E] Fig. Figure 3E is a diagram illustrating the method for manufacturing the diamond electrode according to the first embodiment. [ Fig. 4] Fig. Figure 4 is a diagram illustrating a representative exemplary setup of a diamond electrode according to a second embodiment. [ Fig. 5A] Fig. Figure 5A is a diagram illustrating a method for manufacturing the diamond electrode according to the second embodiment. [ Fig. 5B] Fig. Figure 5B is a diagram illustrating the method for manufacturing the diamond electrode according to the second embodiment. [ Fig. 5C] Fig. Figure 5C is a diagram illustrating the process for manufacturing the diamond electrode according to the second embodiment. [ Fig. 6] Fig. Figure 6 is a diagram illustrating a representative exemplary setup of a diamond electrode according to a third embodiment. [ Fig. 7A] Fig. Figure 7A is a diagram illustrating a method for manufacturing the diamond electrode according to the third embodiment. [ Fig. 7B] Fig. Figure 7B is a diagram illustrating the method for manufacturing the diamond electrode according to the third embodiment. [ Fig. 8] Fig. Figure 8 is a diagram illustrating a representative exemplary setup of a diamond electrode according to a fourth embodiment. [ Fig. 9A] Fig. Figure 9A is a diagram illustrating a method for manufacturing the diamond electrode according to the fourth embodiment. [ Fig. 9B] Fig. Figure 9B is a diagram illustrating the method for manufacturing the diamond electrode according to the fourth embodiment. [ Fig. 9C] Fig. Figure 9C is a diagram illustrating the process for manufacturing the diamond electrode according to the fourth embodiment. Detailed description [Problem to be solved by the present disclosure]

[0006] When a thin layer, such as in PTL 1, consists of fine diamond grains, gaps, known as pinholes, are present between the fine diamond grains. The presence of pinholes reduces the coverage of the base material by the thin layer, leading to a decrease in electrical conductivity. To reduce the pinholes and improve coverage, it is necessary to achieve smaller grain sizes for the fine diamond grains.

[0007] However, if the grain sizes of the diamond particles are made small, the proportion of SP 2 - Bonds in the thin layer are greater than the proportion of SP 3-bonds within it. Therefore, the thin layer cannot sufficiently exhibit the excellent properties of conductive diamond described above, which leads to a tendency for the cyclic voltammetry property (hereinafter also referred to as the "ZV property") of the electrode to decrease.

[0008] Therefore, one objective of the present disclosure is to provide a diamond electrode with excellent ZV properties. [Beneficial effect of the present disclosure]

[0009] According to the present disclosure, it is possible to provide a diamond electrode with excellent ZV properties. [Description of embodiments]

[0010] First, embodiments of the present disclosure are listed and described. A diamond electrode according to the present disclosure is a diamond electrode comprising: a conductive diamond element in rod form; and a metal element in rod form that is electrically connected to the conductive diamond element, wherein The diamond content of the conductive diamond element is greater than or equal to 80 vol.%.

[0011] According to the present disclosure, it is possible to provide a diamond electrode with excellent ZV properties.

[0012] (2) In (1) the conductive diamond element may comprise a first region which is exposed to the outside, wherein a maximum value D of a diameter of a circumscribing circle of a cross-section of the first region may be 0.3 mm or less, the cross-section can be a cross-section in which one direction of extension of the conductive diamond element is considered the normal direction, and The specific resistance of the conductive diamond element can be 1000 Ω·cm or less.

[0013] Because the conductive diamond element is very thin and sufficiently small, the diamond electrode incorporating this conductive diamond element can be used as a probe for a tiny area, an electrochemical biosensor, and a probe to power a cell. When the measurement is performed inside a cell using the diamond electrode, a substance can be detected in vivo with high sensitivity.

[0014] (3) In (2), the ratio L / D of the length L of the first region along the extension direction to D can be greater than or equal to 1. Therefore, the probe can be inserted deep into a sample and the contact area with the sample is increased, thereby improving the sensitivity of the diamond electrode.

[0015] (4) In one of points (1) to (3) the conductive diamond element may have a first end section on the side of the metal element and a second end section on a side opposite the first end section, wherein a diameter d2 of a maximum incircle of the conductive diamond element on the side of the second end section can be smaller than a diameter d1 of a maximum incircle of the conductive diamond element on the side of the first end section, and d2 can be 0.05 mm or less. d1 and d2 can each be measured by viewing the conductive diamond element from the side.

[0016] Since the conductive diamond element is sufficiently small, the diamond electrode containing the diamond element can be used for a probe for a tiny area, an electrochemical biosensor, and a probe to power a cell.

[0017] (5) In one of points (1) to (4) The conductive diamond element can consist of diamond, and The boron content of the diamond can be greater than or equal to 10 ppm and less than or equal to 50000 ppm.

[0018] This improves the electrical conductivity of the conductive diamond element, allowing it to function as a sensor.

[0019] (6) At one of the points (1) to (5) in a Raman spectrum of the conductive diamond element lies the percentage (I2 / I3) × 100 of a peak intensity I2 of a peak with a half-width greater than 50 cm. -1 at a wave number greater than or equal to 1545 cm -1 and less than or equal to 1600 cm -1 with respect to a peak intensity I3 of a peak with a half-width of greater than or equal to 20 cm -1 at a wave number greater than or equal to 1320 cm -1 and less than or equal to 1340 cm -1 at less than or equal to 30%.

[0020] Accordingly, in the diamond electrode containing the conductive diamond element, the leakage current is reduced, thereby improving the detection sensitivity.

[0021] (7) At any of points (1) to (6) the angle between a direction of extension of the conductive diamond element and a direction of extension of the metal element may be 5° or less, and A connecting section between the conductive diamond element and the metal element can be covered with an insulating element.

[0022] Therefore, it is only suitable for observing the electrochemical properties of diamond, since no electrochemical properties of any other material are involved.

[0023] (8) In one of the points (1) to (7), the metal element can have a tubular shape. Accordingly, the conductive diamond element can be inserted into a through-hole in the metal element to connect them. That is, the thin rod-shaped diamond and the thin rod-shaped metal can be firmly joined together.

[0024] (9) In (7) the insulating element can be composed of polyimide. Accordingly, a thin layer of the insulating element can be formed to achieve electrical insulation at a low temperature of 300 °C or less.

[0025] (10) In (7) the insulating element can be composed of a cross-linked fluorinated resin. Accordingly, the thin layer of the insulating element can be designed to provide electrical insulation at a low temperature of 300 °C or less. Furthermore, the insulating element can retain its durability even under strong acid or alkalinity.

[0026] (11) At one of points (7), (9) and (10) the average thickness of the insulating element can be greater than or equal to 5 µm and less than or equal to 50 µm. Therefore, it is possible to maintain a state with approximately the same thinness as a rod-shaped electrode not covered with an insulating element, while simultaneously ensuring electrical insulation at approximately 10 V or less.

[0027] (12) In each of points (1) to (11), the conductive diamond element can be composed of single-crystal diamond. Therefore, the electrical conductivity can be greater than that of polycrystalline diamond even if the impurity content is the same as in polycrystalline diamond. This is because, in single-crystal diamond, charge carriers supplied by acceptor and donor impurities can be prevented from disappearing due to grain boundaries, thus avoiding an increase in electrical resistance due to contact resistance.

[0028] (13) In one of points (1) to (11) the conductive diamond element is composed of polycrystalline diamond, and The average grain size of the polycrystalline diamond can be larger than the diameter d2 of a maximum inscribed circle of the conductive diamond element on a second end face of the conductive diamond element opposite the first end face of the conductive diamond element on the metal side.

[0029] Accordingly, the diamond at the tip on the side of the second end section is essentially a single crystal, which increases the electrical conductivity for the same reason as in (12) above.

[0030] (14) In one of points (1) to (11), the conductive diamond element can be composed of nanopolycrystalline diamond. Accordingly, the strength in the middle region of the rod-shaped diamond is greater than that of a single crystal, which cleaves easily, resulting in a strong rod-shaped diamond electrode that does not break even when inserted into a solid such as a cell. [Details of embodiments of the present disclosure]

[0031] The following are specific examples of the diamond electrode according to the present disclosure, illustrated with figures. In the figures of the present disclosure, identical reference numerals denote identical or corresponding parts. Furthermore, dimensional ratios such as length, width, thickness, or depth are appropriately modified for clarity and simplification of the figures and therefore do not necessarily reflect the actual dimensional ratios.

[0032] In the present description, the expression "A to B" means the lower and upper limits of a range (i.e. greater than or equal to A and less than or equal to B), and if no unit is specified for A and only a unit is specified for B, then the units of A and B are the same.

[0033] If one or more numerical values ​​are described in the present disclosure as the lower and upper limits of a range of numbers, it is assumed that a combination of any numerical value described as a lower limit and any numerical value described as an upper limit is also disclosed.For example, if greater than or equal to a1, greater than or equal to b1 and greater than or equal to c1 are each described as lower bounds and less than or equal to a2, less than or equal to b2 and less than or equal to c2 are each described as upper bounds, it is assumed that greater than or equal to a1 and less than or equal to a2, greater than or equal to a1 and less than or equal to b2, greater than or equal to a1 and less than or equal to c2, greater than or equal to b1 and less than or equal to a2, greater than or equal to b1 and less than or equal to b2, greater than or equal to b1 and less than or equal to c2, greater than or equal to c1 and less than or equal to a2, greater than or equal to c1 and less than or equal to b2 and greater than or equal to c1 and less than or equal to c2 are disclosed.

[0034] The present embodiment is described in more detail with reference to examples. However, the present embodiment is not limited to these examples. [First embodiment]

[0035] A diamond electrode according to one embodiment (hereinafter also referred to as the “first embodiment”) of the present disclosure is, with reference to Fig. 1, Fig. 2A and Fig. 2B described.

[0036] As in Fig. As shown in Figure 1, a diamond electrode 1 comprises: a conductive diamond element 2 in a rod shape; and a metal element 3 in a rod shape, which is electrically connected to the conductive diamond element 2, wherein the diamond content of the conductive diamond element 2 is greater than or equal to 80 volume percent or vol.%. The specification "greater than or equal to 80 volume percent" means that the conductive diamond element is composed substantially of conductive diamond and that the volume fraction of any other material is less than 20 volume percent. For example, if, when considering a cross-section of a rod-shaped diamond, a material other than the conductive diamond constitutes less than 20 area percent of its cross-sectional area, there is a high probability that "the diamond content of the conductive diamond element is greater than or equal to 80 volume percent." Strictly speaking, the integral of this is the volume percentage along the direction of the rod shape.If another rod-shaped material is coated with diamond, a product with a diamond content of less than 80 vol.% can be produced; however, this method cannot be used to produce the diamond electrode of the present invention, in which "the diamond content of the conductive diamond element is greater than or equal to 80 vol.%". This is because the present invention is not applied to a tiny electrode.

[0037] The diamond electrode of the present disclosure can exhibit excellent ZV properties, since the diamond content of the diamond element is greater than or equal to 80 vol.% and the diamond electrode of the present disclosure can exhibit the excellent properties of diamond. <aufbau>

[0038] The diamond electrode 1 according to the first embodiment comprises: a conductive diamond element 2 in rod form; and a metal element 3 in rod form, which is electrically connected to the conductive diamond element 2. The metal element 3 has a tubular shape with a through-hole extending from one end section to the other end section, and a section of the conductive diamond element 2 on the side of the first end section 2a is inserted into the through-hole on the side of one end section (hereinafter also referred to as the third-A end section) of the metal element 3. Because the metal element has such a tubular shape, it can be firmly connected to the conductive diamond in rod form. The strength can also be adjusted by changing the length of the connecting section. A brazing material 5 is arranged between the metal element 3 and the conductive diamond element 2.The brazing material is in contact with both the metal element 3 and the conductive diamond element 2, electrically connecting them. Because the metal element is tubular, a low-resistance electrical connection can be achieved. The contact resistance can also be minimized by adjusting the length of the connecting section. The first end section 2a of the conductive diamond element 2 and the third end section 3a of the metal element 3 can be in contact with each other. The connecting section between the conductive diamond element 2 and the metal element 3 is covered with an insulating element 4. The conductive diamond element is preferably in contact with the metal element, as this allows the entire diamond electrode to be kept thin.Although the disadvantage is that the strength of the connecting section is insufficient, the connection strength can be increased and the contact resistance reduced by cutting both rod shapes at an angle to increase the cross-sectional areas, instead of using vertical cross-sections. Here, a section referred to as a rod shape includes a needle-shaped section with a gradually tapered tip. This is because, in a real-world application, it is efficient for the conductive diamond element to have a needle shape.

[0039] An angle (hereinafter also referred to as the "connection angle") between a direction of extension of the conductive diamond element 2 and a direction of extension of the metal element 3 can be 5° or less. It is often desirable to align the diamond electrode directly with a sensor area. It is important that the path followed by the tip of the diamond electrode is also followed by the rest of the diamond electrode. Therefore, a smaller connection angle is advantageous. If the connection angle is less than or equal to 5° and the conductive diamond element has a length of 5 mm, any deviation (the difference (displacement) between the end section on the diamond element side and the end section on the metal element side, when the diamond electrode is viewed from the side of the second end section 2b of the conductive diamond element) is limited to a width of 0.43 mm or less.If the connection angle is less than or equal to 3°, the deviation is limited to a width of 0.26 mm or less. If the connection angle is less than or equal to 1°, the deviation is limited to a width of 0.087 mm or less. If the deviation is 0.5 mm or more, the diamond electrode cannot be aimed at a target location for measurement, making it difficult to perform the intended measurement. <Leitfähiges Diamantelement>

[0040] In the present disclosure, the diamond content of the conductive diamond element 2 is greater than or equal to 80 vol.%. Thus, the conductive diamond element can exhibit the excellent properties of diamond and therefore possess the excellent ZV property.

[0041] The lower limit of the diamond content of the conductive diamond element is greater than or equal to 80 vol.%, preferably greater than or equal to 85 vol.%, more preferably greater than or equal to 90 vol.%, more preferably greater than or equal to 95 vol.%, and further preferably greater than or equal to 98 vol.%. The upper limit of the diamond content of the conductive diamond component is preferably less than or equal to 100 vol.%. The diamond content of the conductive diamond element is preferably greater than or equal to 80 vol.% and less than or equal to 100 vol.%, more preferably greater than or equal to 90 vol.% and less than or equal to 100 vol.%, and further preferably greater than or equal to 98 vol.% and 100 vol.%. It has traditionally been generally proposed to grow diamond on a rod-shaped metal to produce a rod-shaped diamond; however, in this case, the diamond content is less than 80 vol.%.If the diamond content is low, a pinhole can form in a diamond-coated area, revealing properties of the metal part and thus degrading the properties of the rod-shaped diamond. This can be prevented by achieving a diamond content of 80% by volume or more.

[0042] One method for measuring the diamond content of a conductive diamond element is as follows. The conductive diamond element is cut at 10 locations, and the cross-sections at these 10 locations are subjected to elemental analysis to classify them into regions (carbon regions) composed entirely of carbon atoms and regions (other-carbon regions) containing atoms other than carbon. The percentage A of the total area of ​​the carbon regions in the cross-sections at these 10 locations, relative to the total area of ​​the cross-sections at these 10 locations, is then calculated. This percentage A represents the diamond content of the conductive diamond element. The 10 locations can be calculated by selecting cross-sectional areas obtained by substantially uniformly cutting the conductive diamond element with 10 µm sections from both ends.The cutting process uses a laser, but this results in the conversion of a diamond part into a non-diamond part. Therefore, the measurement must be performed after a treatment to remove the non-diamond part. Specifically, the removal treatment is carried out in a hot mixed acid solution obtained by heating a mixed acid solution containing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1.

[0043] The carbon regions are in most cases essentially diamond; however, if the carbon regions contain a portion that is not diamond, the diamond content of the conductive diamond element is measured, dividing the regions into a diamond region consisting of diamond and a region consisting of a material other than diamond. This measurement is performed using Raman spectroscopy instead of elemental analysis. Specifically, a cross-section of the conductive diamond element is created by laser cutting and polishing, and the Raman spectroscopy measurement is carried out such that the regions are divided into a region containing a peak of 1332 ± 2 cm. -1 The area where the peak is present is subdivided into two parts, creating a two-dimensional distribution and thus a distribution of diamond presence. The average of the area fractions (the area where diamond is present / the total area) at five different locations is calculated, thereby determining the diamond fraction (volume fraction) of the conductive diamond element.

[0044] The conductive diamond element can be composed of diamond and an unavoidable impurity. Examples of unavoidable impurities include silicon, aluminum, molybdenum, tungsten, tantalum, iron, nickel, cobalt, and the like. The concentration of the unavoidable impurity preferably corresponds to an atomic density of 100 ppm or less. The concentration or concentration of the unavoidable impurity is measured by secondary ion mass spectrometry (SIMS).

[0045] Examples of components other than diamond in the conductive diamond element include tungsten, tantalum, iron, nickel, and cobalt.

[0046] The specific resistance of the conductive diamond element is preferably less than or equal to 1000 Ω·cm. This improves the sensitivity of the diamond electrode. When the measurement is performed within a cell using the diamond electrode, a substance can be detected in vivo with high sensitivity.

[0047] The upper limit of the resistivity of the conductive diamond element is preferably less than or equal to 1000 Ω·cm, more preferably less than or equal to 100 Ω·cm, more preferably less than or equal to 10 Ω·cm, more preferably less than or equal to 1 Ω·cm, more preferably less than or equal to 0.1 Ω·cm, and further preferably less than or equal to 0.01 Ω·cm. The lower limit of the resistivity of the conductive diamond element is not particularly restricted and can, for example, be greater than or equal to 0.0001 Ω·cm. The specific resistance of the conductive diamond element is preferably greater than or equal to 0.0001 Ω·cm and less than or equal to 1000 Ω·cm, preferably greater than or equal to 0.0001 Ω·cm and less than or equal to 10 Ω·cm, preferably greater than or equal to 0.0001 Ω·cm and less than or equal to 0.1 Ω·cm and even more preferably greater than or equal to 0.0001 Ω·cm and less than or equal to 0.01 Ω·cm.

[0048] As in Fig. As shown in Figure 2A, the conductive diamond element 2 preferably has a first region 21 that is exposed to the outside, and a maximum value D of a diameter of a circumscribing circle C1 of a cross-section of the first region 21 is preferably 0.3 mm or less. Here, the cross-section is a cross-section when the first region is cut along a plane for which an extension direction of the diamond element from the first end section 2a to the second end section 2b of the conductive diamond element is considered the normal direction. Since the diamond element is sufficiently small, the diamond electrode containing the diamond element can be used for a probe for a tiny area, an electrochemical biosensor, and a probe for powering a cell.

[0049] For example, when a cell is measured with a diamond electrode, local information can be gathered without damaging the cell. Therefore, a correlation between a disease and a substance in a living organism can be accurately measured.

[0050] The upper limit of the maximum value D is preferably less than or equal to 0.3 mm, more preferably less than or equal to 0.1 mm, and further preferably less than or equal to 0.075 mm. The lower limit of the maximum value D is not particularly restricted and may, for example, be 0.01 mm or more from a manufacturing perspective. The maximum value D is preferably greater than or equal to 0.01 mm and less than or equal to 0.3 mm, more preferably greater than or equal to 0.01 mm and less than or equal to 0.1 mm, and further preferably greater than or equal to 0.01 mm and less than or equal to 0.075 mm.

[0051] The maximum value D is measured by examining the cross-section of the first region 21 with an optical microscope or a scanning electron microscope.

[0052] A ratio L / D of the length L of the first area 21 along the extension direction (that indicated by the arrow A1 in Fig. The direction (indicated by 1) to the maximum value D is preferably greater than or equal to 1. This allows the probe to be inserted deep into a sample, and the contact area with the sample is increased, thereby improving the sensitivity of the diamond electrode.

[0053] The lower limit of the L / D ratio is preferably greater than or equal to 1, more preferably greater than or equal to 3, more preferably greater than or equal to 5, more preferably greater than or equal to 8, and further preferably greater than or equal to 10. The upper limit of the L / D ratio is not particularly restricted and may, for example, be 20 or less from a manufacturing perspective. The L / D ratio is preferably greater than or equal to 1 and less than or equal to 20, more preferably greater than or equal to 3 and less than or equal to 20, more preferably greater than or equal to 5 and less than or equal to 20, and further preferably greater than or equal to 10 and less than or equal to 20.

[0054] The lower limit of the length L is preferably greater than or equal to 0.01 mm, more preferably greater than or equal to 0.1 mm, further preferably greater than or equal to 0.5 mm, and more preferably greater than or equal to 1.0 mm. The upper limit of the length L is not particularly restricted and may, for example, be 20 mm or less for manufacturing reasons. The length L is preferably greater than or equal to 0.01 mm and less than or equal to 20 mm, more preferably greater than or equal to 0.1 mm and less than or equal to 10 mm, and more preferably greater than or equal to 1.0 mm and less than or equal to 5.0 mm.

[0055] As in Fig. As shown in Figure 2B, the conductive diamond element 2 has a first end section 2a on the side of the metal element 3 and a second end section 2b on the side opposite the first end section 2a, wherein the diameter d2 of a maximum inscribed circle C2 of the conductive diamond element 2 on the side of the second end section 2b is smaller than the diameter d1 of a maximum inscribed circle or incircle C3 of the conductive diamond element 2 on the side of the first end section 2a, and wherein the diameter d2 is preferably less than or equal to 0.1 mm, more preferably less than or equal to 0.05 mm, and further preferably less than or equal to 0.03 mm. Since the diamond element is sufficiently small, the diamond electrode containing the diamond element can be used for a probe for a tiny area, an electrochemical biosensor, and a probe for powering a cell.

[0056] Here, the diameters d1 and d2 are each measured by viewing the conductive diamond element 2 from the side. The maximum incircle C2 of the conductive diamond element 2 on the side of the second end section 2b denotes a maximum circle that can be drawn within a region enclosed by the outer edge of the conductive diamond element 2 when viewed from the side of the second end section 2b of the conductive diamond element 2. The maximum incircle C3 of the conductive diamond element 2 on the side of the first end section 2a denotes a maximum circle that can be drawn within a region enclosed by the outer edge of the conductive diamond element 2 when viewed from the side of the first end section 2a of the conductive diamond element 2. If the size of the maximum inscribed circle orSince the incircle C2 differs depending on the direction in which the conductive diamond element 2 is viewed, the diameter d1 and the diameter d2 are measured in a direction in which the diameter of the maximum inscribed circle C2 is greatest.

[0057] The upper limit of the diameter d2 is preferably less than or equal to 0.05 mm, more preferably less than or equal to 0.03 mm, and further preferably less than or equal to 0.01 mm. The lower limit of the diameter d2 is not particularly restricted and can, for example, be 0.0001 mm or more from a manufacturing perspective. The diameter d2 is preferably greater than or equal to 0.0001 mm and less than or equal to 0.05 mm, more preferably greater than or equal to 0.0005 mm and less than or equal to 0.03 mm, and further preferably greater than or equal to 0.001 mm and less than or equal to 0.01 mm.

[0058] The diameter d1 is preferably greater than or equal to 0.05 mm and less than or equal to 0.3 mm, more preferably greater than or equal to 0.05 mm and less than or equal to 0.2 mm, and further preferably greater than or equal to 0.05 mm and less than or equal to 0.1 mm.

[0059] From the first end section 2a to the second end section 2b, the cross-sectional area of ​​the conductive diamond element 2 can remain unchanged or decrease monotonically. From a manufacturing perspective, it is advantageous if the cross-sectional area decreases monotonically, while from the perspective of structural strength and application, it is more advantageous if the cross-sectional area remains unchanged from the first end section 2a to a predetermined position between the first end section 2a and the second end section 2b along a length L, and then decreases monotonically from that predetermined position to 2b. Here, the cross-sectional area is the area of ​​a cross-section exposed when cut along the plane for which the direction from the first end section 2a to the second end section 2b is considered the normal line.

[0060] The shape of the conductive diamond element is not particularly restricted, as long as it can be used as an electrode. For example, the shape can be a cone, a truncated cone, an elliptical cone, a truncated elliptical cone, a pyramid, or a truncated pyramid.

[0061] The conductive diamond element is preferably composed of diamond, and the boron content of the diamond is preferably 10 ppm or more and 50,000 ppm or less. This improves the electrical conductivity of the conductive diamond element. The boron content of the diamond is preferably greater than or equal to 10 ppm and less than or equal to 50,000 ppm, more preferably greater than or equal to 200 ppm and less than or equal to 50,000 ppm, and further preferably greater than or equal to 2,000 ppm and less than or equal to 50,000 ppm. The conductive diamond element may contain an impurity other than diamond, as long as the effects of the present disclosure are not impaired.

[0062] The boron content or boron fraction of the diamond is measured using secondary ion mass spectrometry (SIMS).

[0063] The conductive diamond element can be composed primarily of diamond. In a Raman spectrum of the conductive diamond element, the percentage (I2 / I3) × 100 of the peak intensity I2 of a peak with a full width at half maximum (FWHM) of more than 50 cm⁻¹ lies within this range. -1 at a wave number of 1545 cm -1 or more and 1600 cm -1 or less in relation to a peak intensity I3 of a peak with a half-width of 20 cm -1 or less at a wavenumber of 1320 cm -1 or more and 1340 cm -1 or less, preferably at 30% or less. In the diamond electrode containing the conductive diamond element, the leakage current is low and the detection sensitivity is improved. The peak has a full width at half maximum (FWHM) of less than or equal to 20 cm. -1 at a wave number greater than or equal to 1320 cm -1 and less than or equal to 1340 cm -1 This is a peak originating from a diamond. The peak has a width at half maximum (WHM) of more than 50 cm. -1 at a wave number greater than or equal to 1545 cm -1 and less than or equal to 1600 cm -1 is considered a peak originating from a graphite-like structure. The excitation light for the Raman spectroscopy measurement is typically 530 nm, and the measurement is preferably performed under conditions such that an objective lens provides a magnification of 20x or more and a laser power density of 9×10⁻⁵. 6 W / cm 2 exhibits.

[0064] The upper limit of the percentage (I2 / I3) × 100 is preferably less than or equal to 30%, more preferably less than or equal to 20%, even more preferably less than or equal to 10%, and further preferably less than or equal to 5%. The lower limit of the percentage (I2 / I3) × 100 is not particularly restricted and can, for example, be 0% or more. The percentage (I2 / I3) × 100 is preferably greater than or equal to 0% and less than or equal to 30%, even more preferably greater than or equal to 0% and less than or equal to 10%, and further preferably greater than or equal to 0% and less than or equal to 5%.

[0065] The Raman spectrum is measured using a microscopic Raman spectrometer. The measurement is performed at room temperature (greater than or equal to 20 °C and less than or equal to 25 °C) using a laser with a wavelength of 532 nm as excitation light.

[0066] The angle between the direction of extension of the conductive diamond element 2 and the direction of extension of the metal element 3 is preferably 5° or less. That is, the diamond electrode 1 preferably has an overall rod shape. Accordingly, the diamond electrode 1 can be conveniently inserted straight into a very small area such as a cell or conveniently inserted through a narrow gap. The angle is preferably greater than or equal to 0° and less than or equal to 2°, and even more preferably greater than or equal to 0° and less than or equal to 1°.

[0067] The conductive diamond element is preferably composed of single-crystal diamond. Therefore, it is suitable for increasing electrical conductivity compared to polycrystalline diamond with the same impurity content.

[0068] The conductive diamond element can be composed of polycrystalline diamond, and the average grain size of the polycrystalline diamond can be larger than the diameter d2 of the largest inscribed circle of the conductive diamond element on the side of the second end section opposite the side of the first end section on the metal element side. Thus, the section of the conductive diamond element at its tip on side 2b of the second end section is essentially uniformly a single crystal and is suitable for increasing the electrical conductivity compared to a case in which the conductive diamond element is composed of polycrystalline diamond with the same amount of impurities and a grain size smaller than the diameter d2.

[0069] The conductive diamond element is preferably composed of nanocrystalline diamond. This makes it suitable for maintaining high mechanical strength in the thin conductive diamond element. This is because, in the case of single-crystal diamond, the thin conductive diamond element can be cleaved and therefore cannot maintain the required strength.

[0070] The average grain size of the nanopolycrystalline diamond is preferably 5 nm or more and 2000 nm or less, more preferably 10 nm or more and 500 nm or less, and further preferably 20 nm or more and 100 nm or less.

[0071] The average grain size of the nanopolycrystalline diamond can be determined by an intercept method using a scanning electron microscope (SEM). Specifically, the scanning electron microscope is first used to observe the nanopolycrystalline diamond at a magnification of 1000x to 100,000x to obtain an SEM image.

[0072] Next, a circle is drawn on the SEM image, and then eight straight lines are drawn radially from the center of the circle to its outer circumference (so that the angles of intersection between the straight lines are essentially equal). In this case, the observation magnification and the diameter of the circle are preferably set so that the number of diamond grains (crystal grains) on each straight line is approximately 10 to 50.

[0073] Then, the number of intersections of each of the straight lines with the crystal grain boundaries of the diamond grains is counted. The length of the straight line is divided by the number of intersections of the straight line with the crystal grain boundaries to determine an average section length, and a numerical value obtained by multiplying the average section length by 1.128 is considered the first average grain size. It should be noted that the first average grain size is determined for each of the five SEM images in the above procedure, and the average of these first average grain sizes is considered the average grain size. <metallelement>

[0074] In the present disclosure, the metal element 3 is electrically connected to the conductive diamond element 2. The metal element 3 and the conductive diamond element 2 can be in contact with each other or electrically connected to each other via a soldering material 5. For example, silver paste, solder, silver wax, or the like can be used as the soldering material.

[0075] The material of the metal element 3 is preferably a material that has sufficient strength even at a diameter of 0.1 mm, does not corrode and is easy to process, such as a stainless steel wire or a tungsten wire.

[0076] The metal element 3 of the first embodiment has the shape of a tube. Accordingly, the conductive diamond element 2 can be inserted into the through-bore of the metal element 3. The shape of the metal element is not limited to a tube shape. For example, only one end of the metal element 3 has a hollow structure with a bore into which the conductive diamond element can be inserted, while the other end can have a solid structure. The external shape of the metal element is not limited to a cylindrical shape. For example, the external shape can be a truncated cone, an elliptical cone, a truncated elliptical cone, a pyramid, or a truncated pyramid.

[0077] The height difference at the connection point between the metal element 3 and the conductive diamond element 2 is preferably less than or equal to 100 µm, more preferably less than or equal to 75 µm, and further preferably less than or equal to 50 µm. This makes it possible to achieve an effect in which the metal element 3 and the conductive diamond element 2 are smoothly connected to form a rod shape, i.e., an effect in which insertion is possible without resistance due to snagging at the height difference when inserting into a cell or the like. Here, the height difference corresponds to half the difference between the outer diameter of the metal element 3 and the outer diameter of the conductive diamond element 2. As long as the height difference is within the aforementioned range, the insulating element 4 can be connected without obstruction or interruption. <isolierelement>

[0078] The connecting section between the conductive diamond element 2 and the metal element 3 is covered by the insulating element 4. Here, the connecting section is the area where the height difference described above between the conductive diamond element 2 and the metal element 3 is created. This ensures that the metal element 3 is not exposed and no electrochemical current is generated within it. Furthermore, the insulating element creates a smooth connection between the conductive diamond element 2 and the metal element 3 at the point of height difference, resulting in a smooth connecting section.The insulating element can cover half or more of the conductive diamond element 2 from the connection section at the height difference in the direction of extension of the conductive diamond element 2, or it can cover half or more of the metal element 3 from the connection section at the height difference in the direction of extension of the metal element 3. The length of the insulating element can be appropriately determined according to the design of a measuring device, provided that the structure is such that only the conductive diamond element 2 is in contact with an electrolyte to be measured, and the metal element 3 is not in direct contact with it and is in an insulated state.

[0079] Examples of insulating element materials include polyimide, cross-linked fluoropolymer resin, and Teflon (registered trademark)-based resin. One of these materials can be used, or two or more can be used.

[0080] The insulating element is preferably made of polyimide. This allows the insulating element to be formed at a lower temperature, and the remaining area that cannot be covered can be reduced even if the insulating element is thin. The insulating element is preferably composed of a cross-linked fluoropolymer resin. This allows the insulating element to be formed at a higher temperature, provides more voluminous coverage, and offers advantages in terms of acid and alkali resistance. The cross-linked fluoropolymer resin is a resin obtained by improving the adhesion of a fluoropolymer through the application of an electron beam or the like, or a resin in which a molecular chain of CF is branched / cross-linked within the fluoropolymer.

[0081] The average thickness of the insulating element is preferably greater than or equal to 5 µm and less than or equal to 50 µm. This makes it possible to ensure insulation at a voltage of 10 V and to uniformly compensate for the height difference between the conductive diamond element 2 and the metal element 3. The average thickness of the insulating element is preferably greater than or equal to 10 µm and less than or equal to 40 µm, and even more preferably greater than or equal to 10 µm and less than or equal to 30 µm.

[0082] A method for measuring the average thickness of the insulating element is as follows. In a cross-section obtained by cutting along an imaginary plane, for which the extension direction of the metal element is considered the normal, in the area where the metal element of the diamond electrode and the insulating element covering the metal element are present, the outer diameter of the entire insulating element covering the metal element 3 and the outer diameter of the metal element 3 are observed with a micrometer or a microscope, and the average thickness of the insulating element is calculated from half the difference between these values. <Verfahren zur Herstellung einer Diamantelektrode>

[0083] A method for producing the diamond electrode according to the first embodiment is described with reference to Fig. 1 and 3A to 3E described.

[0084] A diamond plate 20 is manufactured from conductive diamond (see Fig. 3A). The diamond plate 20 can be produced, for example, as follows: a boron-doped polycrystalline diamond with a thickness of 50 µm or more and 500 µm or less is synthesized on a silicon substrate by a general CVD process, and the silicon substrate is subsequently removed. Furthermore, the diamond plate 20 can also be produced as follows: Ir or Pt is epitaxially grown on a single-crystal sapphire or single-crystal MgO substrate, a heterojunction boron-doped single-crystal diamond is synthesized on this substrate, and the heterogeneous substrate is removed. Additionally, the diamond plate 20 can also be produced as follows: a boron-doped single-crystal diamond is homoepitaxially grown on a single-crystal diamond substrate with insulating properties, and the single-crystal diamond of the seed substrate is removed by laser. The diamond content of the diamond plate thus obtained is 100 vol.-%. The average thickness of the diamond plate is preferably 50 µm or more and 500 µm or less. The diamond plate can be a homoepitaxial single-crystal diamond, a heteroepitaxial diamond, or a polycrystalline diamond. It should be noted that the diamond content of the diamond plate is not limited to 100 vol.%, but can, for example, be greater than or equal to 80 vol.%. In this case, examples of constituents other than diamond in the diamond plate are tungsten, tantalum, iron, nickel, cobalt, and silicon.

[0085] In the CVD process, the diamond content of the diamond plate can be 100 vol.%, whereas in a diamond obtained by sintering, the diamond content can be 80 vol.% because a metal is used as a binder. In both cases, the diamond is the main component, and the diamond's bonding state is dominant, resulting in high bond strength. The binder metal can undergo a surface treatment to prevent it from being exposed. However, when the diamond is synthesized using the CVD process with a metal wire in the center, the diamond content is typically less than 80 vol.%. The bond of diamond deposited by the CVD process is not necessarily strong. Because the metal is exposed at a weak point, the electrochemical properties deteriorate with prolonged use.

[0086] Next, the diamond plate 20 is cut by laser processing, resulting in a conductive diamond element 2 in rod form (see Fig. 3B). The laser application conditions can be, for example, as follows: a focal point diameter of 3 to 50 µm and a pulse energy of 10 to 50 µJ.

[0087] Metal element 3 is being prepared (see Fig. 3C). In the manufacturing process of the first embodiment, the metal element 3 has the form of a tube.

[0088] Next, the brazing material 5 is inserted into the through-hole of the metal element 3 on the side of one end (see Fig. 3D). The solder can be introduced into the bore on the opposite side. Alternatively, the solder can be extracted from the bore on the opposite side using a suction device. Any solder remaining outside the bore, which was not introduced into the bore, is preferably wiped away.

[0089] Next, the conductive diamond element 2 is inserted into the end section of the metal element 3, onto which the solder material 5 has been applied. In this way, the conductive diamond element 2 and the metal element 3 are electrically connected via the solder material 5, and the conductive diamond element 2 is attached to the metal element 3. By heating the solder material to a predetermined temperature, the solder material melts and firmly bonds the conductive diamond element 2 and the metal element 3 together. The solder material can be an active silver wax. This is because a titanium activator strengthens the bond between the two parts. Alternatively, the solder material can be an silver or copper powder. This is because such a powder is not melted but sintered at a predetermined temperature to bond the two parts together.It should be noted that it is essential that the predetermined temperature is equal to or less than the melting point of metal element 3.

[0090] Next, the connecting section between the metal element 3 and the conductive diamond element 2 is covered with the insulating element 4, thereby obtaining the diamond electrode 1 of the first embodiment (see Fig. 1).

[0091] The insulating element 4 is preferably formed by spray coating. Even more preferably, the insulating element formed by the spray coating is subjected to heat treatment at 100 °C or higher. [Second embodiment]

[0092] A diamond electrode according to one embodiment (hereinafter also referred to as the “second embodiment”) of the present disclosure is described with reference to Fig. 4 described. As in Fig. Figure 4 shows a diamond electrode 1 comprising: a conductive diamond element 2 in rod form; and a metal element 3 in rod form, which is electrically connected to the conductive diamond element 2, wherein the diamond content of the conductive diamond element 2 is 80 vol.% or higher.

[0093] The diamond electrode 1 of the second embodiment can have essentially the same structure as that of the first embodiment, with the exception of the structure of the metal element 3 and the method for connecting the conductive diamond element 2 and the metal element 3. The differences from the first embodiment are described below.

[0094] In the diamond electrode 1 of the second embodiment, the metal element 3 has the form of a solid rod and has a third-A end section 3a, which is arranged on the side of the conductive diamond element 2, and a third-B end section 3b on the side opposite the third-A end section 3a. The first end section 2a of the conductive diamond component 2 and the third-A end section 3a of the metal component 3 are opposite each other. The soldering material 5 is arranged between the first end section 2a of the conductive diamond component 2 and the third-A end section 3a of the metal component 3. The soldering material 5 is in contact with both the metal element 3 and the conductive diamond element 2 and electrically connects the metal element 3 and the conductive diamond element 2. A portion of the first end section 2a of the conductive diamond element 2 and a portion of the third end section 3a of the metal element 3 can be in contact with each other. Fig. Figure 4 shows the conductive diamond element 2 and the metal element 3 joined at their surfaces, which are substantially perpendicular to the axial direction. However, both can have axially inclined surfaces and be joined at these inclined surfaces. This is preferable because the joining area can be large, resulting in high joint strength and high electrical conductivity. Even if the surfaces to be joined are inclined with respect to the axial direction, it is advantageous if the axial direction of the diamond element 2 and the axial direction of the metal element 3 form an angle of 5° or less at the time of joining and are essentially straight lines.

[0095] The diameter of the metal element 3 can be determined according to its intended use. For example, the thickness is preferably greater than or equal to 0.01 mm and less than or equal to 0.3 mm, more preferably greater than or equal to 0.02 mm and less than or equal to 0.2 mm, and further preferably greater than or equal to 0.03 mm and greater than or equal to 0.1 mm. If the thickness is less than 0.01 mm, the inherent stiffness of the metal element 3 becomes too low, and the diamond element 2 cannot be pushed from back to front, which is undesirable. If the thickness is greater than 0.3 mm, inserting it into a gap in a very small area, such as a cell, becomes difficult.

[0096] The angle between the direction of extension of the conductive diamond element 2 and the direction of extension of the metal element 3 is 5° or less.

[0097] The soldering material 5 can further cover the outer circumferential surface of the conductive diamond element 2 near the first end section 2a and the outer circumferential surface of the metal element 3 near the third end section 3a. Here, the outer circumferential surface near the first end section 2a denotes a region on the outer circumferential surface of the conductive diamond element 2 in which the distance from the first end section 2a is less than or equal to 0.9 times, preferably less than or equal to 0.3 times, and even more preferably less than or equal to 0.1 times the length of the conductive diamond element 2. The region around the third end section 3a denotes a region on the outer circumferential surface of the metal element 3 in which the distance from the third end section 3a is 0.9 times or less, preferably 0.3 times or less, and even more preferably 0.1 times or less, than the length of the metal element 3.

[0098] The diamond electrode 1 according to the second embodiment can further comprise an insulating element 4 that covers the connection section between the conductive diamond element 2 and the metal element 3. Fig. 4 completely covers the insulating element 4 and the solder material 5. <Verfahren zur Herstellung einer Diamantelektrode>

[0099] A method for producing the diamond electrode according to the second embodiment is described with reference to Fig. 4 and 5A to 5C described.

[0100] The conductive diamond element 2, the metal element 3 and a connecting aid device 8 are prepared (see Fig. 5A). The conductive diamond element 2 is produced according to the method described in the manufacturing process of the first embodiment. A solid rod-shaped element made of a metal is prepared as the metal element 3.

[0101] The joining device 8 has a tubular shape and is provided with a through-hole extending from one end section to the other. The material of the joining device 8 can be, for example, Teflon (registered trademark), resin, or Aron ceramic. This is because the diamond element and the metal element can be removed from it in a subsequent step without damaging them. The size of the cross-section of the through-hole, when cut along a plane for which the direction of extension of the through-hole is considered normal, is not particularly limited as long as the conductive diamond element 2 and the metal element 3 can be inserted and the solder material 5 can be provided on the outer circumferential surface of the conductive diamond element 2 and the metal element 3, respectively.The size of the cross-sectional area of ​​the through-hole is preferably, for example, greater than or equal to 1.1 times and less than or equal to 1.5 times the larger of the cross-sectional areas of the first end section 2a of the conductive diamond element 2 and the cross-sectional area of ​​the third end section 3a of the metal element 3. The soldering material 5 is introduced into the through-hole of the joining aid device 8.

[0102] Next, the conductive diamond element 2 is inserted into the through-hole on one end of the joining aid 8, which is provided with solder material 5. The metal element 3 is inserted into the through-hole on the other end of the joining aid 8 (see Fig. 5B). It is advantageous to remove the solder material 5 that has been pushed out of the through-hole.

[0103] After the solder material 5 has solidified or has undergone heat treatment to solidify it, the joining aid device 8 is removed (see Fig. 5C). The joining aid 8 can be removed, for example, by physical displacement when using a material that does not adhere to the joining aid. Alternatively, the joining aid 8 can be removed by burning it in oxygen. Alternatively, the joining aid 8 can be removed by immersion in water.

[0104] The solder material 5 is covered with the insulating element 4, thereby obtaining the diamond electrode 1 of the second embodiment (see Fig. 4). [Third embodiment]

[0105] A diamond electrode according to one embodiment (hereinafter also referred to as the “third embodiment”) of the present disclosure is described with reference to Fig. 6 described. As in Fig. Figure 6 shows a diamond electrode 1 comprising: a conductive diamond element 2 in rod form; and a metal element 3 in rod form, which is electrically connected to the conductive diamond element 2, wherein the diamond content of the conductive diamond element 2 is 80 vol.% or more.

[0106] The diamond electrode 1 of the third embodiment can have essentially the same structure as that of the second embodiment. <Verfahren zur Herstellung einer Diamantelektrode>

[0107] A method for producing the diamond electrode according to the third embodiment is described with reference to Fig. 6, Fig. 7A and Fig. 7B described.

[0108] The conductive diamond element 2, the metal element 3 and the soldering material 5 are prepared (see Fig. 7A). The first end section 2a of the conductive diamond element and the third end section 3a of the metal element 3 are opposite each other, with the solder material 5 positioned between them. Both the first end section 2a and the third end section 3a are brought into contact with the solder material 5.

[0109] The solder material 5 is subjected to an electrical discharge treatment to join the conductive diamond element 2 and the metal element 3 together (see Fig. 7B). The electrical discharge is generated between the conductive diamond element 2 and the metal element 3. The soldering material 5 is covered with an insulating element 4, thereby obtaining the diamond electrode 1 of the third embodiment (see Fig. 6). [Fourth embodiment]

[0110] A diamond electrode according to one embodiment (hereinafter also referred to as the “fourth embodiment”) of the present disclosure is described with reference to Fig. 8 described. As in Fig. Figure 8 shows a diamond electrode 1 comprising: a conductive diamond element 2 in rod form; and a metal element 3 in rod form, which is electrically connected to the conductive diamond element 2, wherein the diamond content of the conductive diamond element 2 is 80 vol.% or more.

[0111] The diamond electrode 1 of the fourth embodiment can have the same structure as that of the first embodiment, with the exception of the structure of the metal element 3 and the method for connecting the conductive diamond element 2 and the metal element 3. The differences from the first embodiment are described below.

[0112] In the diamond electrode 1 of the fourth embodiment, the metal element 3 has a solid rod shape and comprises a third-A end section 3a, which is arranged on the side of the conductive diamond element 2, and a third-B end section 3b on a side opposite the third-A end section 3a. The first end section 2a of the conductive diamond element 2 and the third-A end section 3a of the metal element 3 are opposite each other. An adhesive 6 is arranged between the first end section 2a of the conductive diamond element 2 and the third-A end section 3a of the metal element 3. The adhesive 6 is in contact with both the metal element 3 and the conductive diamond element 2 and physically connects the metal element 3 and the conductive diamond element 2. A portion of the first end section 2a of the conductive diamond element 2 and a portion of the third-A end section 3a of the metal element 3 may be in contact with each other.

[0113] The adhesive 6 can further cover the outer circumferential surface of the conductive diamond element 2 near the first end section 2a and the outer circumferential surface of the metal element 3 near the third end section 3a. Here, the outer circumferential surface near the first end section 2a means a region on the outer circumferential surface of the conductive diamond element 2 in which the distance from the first end section 2a is less than or equal to 0.9 times, preferably less than or equal to 0.3 times, and even more preferably less than or equal to 0.1 times the length of the conductive diamond element 2. The area surrounding the third-A end section 3a defines a region on the outer circumferential surface of the metal element 3 in which the distance from the third-A end section 3a is less than or equal to 0.9 times, preferably less than or equal to 0.3 times and preferably less than or equal to 0.1 times the length of the metal element 3.

[0114] The diamond electrode 1 according to the fourth embodiment further comprises a metal coating 7 that continuously covers a portion of the conductive diamond element 2 on the side of the first end section 2a, the adhesive 6, and a portion of the metal element 3 on the side of the third end section 3a. The metal coating 7 is in contact with the conductive diamond element 2, the adhesive 6, and the metal element 3. Thus, the conductive diamond element 2 and the metal element 3 are electrically connected by the metal coating 7. Gold, platinum, titanium, zirconium, niobium, molybdenum, tungsten, or the like can be used as the metal coating 7.

[0115] The diamond electrode 1 according to the fourth embodiment can further comprise an insulating element 4 that covers the conductive diamond element 2, the adhesive 6, and the metal element 3. Fig. 8 completely covers the insulating element 4, the conductive diamond element 2, the adhesive 6 and the metal element 3. <Verfahren zur Herstellung einer Diamantelektrode>

[0116] A method for producing the diamond electrode according to the fourth embodiment is described with reference to Fig. 8 and 9A to 9C described.

[0117] The conductive diamond element 2, metal element 3 and adhesive 6 are prepared (see Fig. 9A). The first end section 2a of the conductive diamond element 2 and the third-A end section 3a of the metal element 3 are opposite each other, with the adhesive 6 positioned between them. The first end section 2a and the third-A end section 3a are each in contact with the adhesive 6 (see Figure 9A). Fig. 9B).

[0118] After the conductive diamond element 2 and the metal element 3 have been fixed by the adhesive 6, a metal coating 7 is formed which continuously covers part of the conductive diamond element 2 on the side of the first end section 2a, the adhesive 6 and part of the metal element 3 on the side of the third end section 3a (see Fig. 9C). The metal coating 7 can be formed using a sputtering process, an electron beam evaporation process, or the like. Since the formation of the metal coating 7 is for the purpose of electrical connection, it is sufficient to perform the formation on one side, but the formation can be carried out twice from the front and back or three times in three directions.

[0119] The conductive diamond element 2, the metal coating 7 and the metal element 3 are covered with an insulating element 4, thereby obtaining the diamond electrode 1 of the fourth embodiment (see Fig. 8). Examples

[0120] The following types of conductive diamond plates were fabricated. The first is a boron-containing polycrystalline diamond produced by CVD (Example 1), the second is a boron-containing single-crystal diamond produced by CVD (Example 2), and the third is a boron-containing nanopolycrystalline diamond produced by a high-pressure process (Example 3). These three conductive diamond plates were preferred because the boron could be distributed substantially uniformly within the substrate. Furthermore, a conductive diamond plate consisting of sintered diamond was fabricated (Example 4). [Example 1]

[0121] In Example 1, the conductive diamond plate was fabricated from polycrystalline diamond. As a polycrystalline diamond suitable for any sample, a self-contained boron-enriched diamond plate was prepared as follows: A boron-enriched diamond with a thickness of 50 µm to 300 µm was synthesized on a silicon substrate using the CVD method, and the silicon substrate was removed with hydrofluoric acid-nitric acid. The diamond was produced by introducing methane gas into hydrogen and decomposing it in a microwave plasma. Alternatively, the diamond could also be produced by thermal decomposition using a hot filament heated to 2000 °C. The boron impurity was added by incorporating a small amount of trimethylborane. These steps do not differ significantly from a general synthesis procedure.Since a 10 mm square substrate was used as the silicon substrate, the conductive diamond plate could be 10 mm in size. 2 to be produced. In one sample, for which "W" is indicated in the "Other Material" column of Table 1, a thin wire of W (tungsten) with a diameter of approximately 17 µm was partially embedded at the time of diamond synthesis (sample 19). Conversely, W was partially vaporized and embedded in the form of a strip 8 µm wide and 2 µm thick, and a strip 1 µm wide and 0.1 µm thick, respectively (sample 18 and sample 17). When the diamond was subsequently laser-cut into a thin needle shape, this thin wire was embedded within the needle-shaped diamond without being exposed at the surface. Such a structure can help make the diamond flexible and prevent it from breaking easily. If the W is exposed at the surface, the central velocity (CV) properties as a sensor are impaired.If the W is exposed at the surface, the exposed W could therefore be covered and completely embedded by additionally performing CVD growth of the diamond for a short time after shaping the diamond into the needle shape.

[0122] Next, a conductive diamond element in rod form was cut from the conductive diamond in plate form using a laser processing system. The conductive diamond element was cut from the 50 µm thick diamond plate to have a width of 50 µm, and the conductive diamond element was cut from the 100 µm thick diamond plate to have a width of 100 µm. At this stage, the width of the diamond to be cut is adjusted according to the plate thickness to produce a rod in the shape of a 50 µm square or a 100 µm square prism, thus allowing the length of the prism's side to be adjusted. Even if the cross-section was not exactly square but trapezoidal, there were no significant problems. The length is 10 mm, which corresponds to the length of one side of the substrate. A desired length can be achieved by laser cutting.To produce a rod with a diameter of 100 µm, a diagonal length of 100 µm was chosen when the thickness was 70 µm and the width was 70 µm, thus producing a rod circumscribed by a circle with a diameter of 100 µm.

[0123] Next, the laser cut was made obliquely from a position corresponding to one-third of the way along the rod towards its tip. The rod was then rotated 90° around its axis, and the laser cut was made again obliquely from the same position, also corresponding to one-third of the way along the rod, towards its tip. The result was a conductive diamond element with a square pyramid shape, with the tip at its apex. The tip diameter was 5 µm. A tip diameter of 5 µm or less could also be achieved by adjusting the laser cutting tolerance. Furthermore, if the needle-shaped rod with a 5 µm tip diameter was etched laterally in two directions with a 90° rotation using an ion beam, it could also be sharpened to a tip diameter of 0.7 µm.The tip diameter could be adjusted to 3 µm, 1.2 µm and 0.7 µm by changing the etching time to 20 minutes, 40 minutes and 60 minutes.

[0124] The conductive diamond element was then subjected to hot acid etching, ion beam etching, or hydrogen plasma treatment to remove any graphite residue resulting from laser processing. This was confirmed by determining the peak ratio using Raman spectroscopy.

[0125] Next, a 5 cm long SUS tube with an inner diameter matching the outer diameter of the conductive diamond was prepared. A small amount of silver paste was extracted from an opening in the tube, and the conductive diamond was inserted 2 mm into the end section where the silver paste had been applied. The tube was then dried and baked on a hot plate at 250 °C for one hour. This process securely attached the conductive diamond to the SUS tube, preventing it from easily detaching even under vibration. Electrical conductivity was also achieved without any issues.

[0126] Next, the tip of the 3 mm conductive diamond and the rear portion of the 1 cm SUS tube, where no diamond was attached, were masked off, and the remaining parts were coated by spraying with polyimide. Since both the needle-shaped conductive diamond and the SUS tube were rotated 120° during this process, their entire circumference could be coated. They were then dried in an oven at 120°C. This yielded diamond electrodes of samples 1 to 19, including the diamond elements, with the specifications described in Tables 1 and 2. [Table 1] Table 1 Leitfähiges Diamantelement Herstellungsverfahren Kristall Korndurchmesser Diamantanteil AnderesMaterial Bor-Anteil Widerstand 12 / 13 µm volume% ppm Ω·cm Probe 1 CVD Poly-Kristall 50,0 100,00 - 5500 0,002 0,020 Probe 2 CVD Poly-Kristall 40,0 100,00 - 5500 0,002 0,040 Probe 3 CVD Poly-Kristall 30,0 100,00 - 5500 0,002 0,020 Probe 4 CVD Poly-Kristall 50,0 100,00 - 5500 0,002 0,030 Probe 5 CVD Poly-Kristall 30,0 100,00 - 5500 0,002 0,040 Probe 6 CVD Poly-Kristall 60,0 100,00 - 5500 0,002 0,020 Probe 7 CVD Poly-Kristall 40,0 100,00 - 5500 0,002 0,040 Probe 8 CVD Poly-Kristall 30,0 100,00 - 5500 0,002 0,040 Probe 9 CVD Poly-Kristall 20,0 100,00 - 5500 0,002 0,020 Probe 10 CVD Poly-Kristall 40,0 100,00 - 2200 0,080 0,006 Probe 11 CVD Poly-Kristall 50,0 100,00 - 1000 0,300 0,006 Probe 12 CVD Poly-Kristall 50,0 100,00 - 250 5,000 0,004 Probe 13 CVD Poly-Kristall 60,0 100,00 - 15 50,000 0,002 Probe 14 CVD Poly-Kristall 50,0 100,00 - 9 200,000 0,002 Probe 15 CVD Poly-Kristall 0,3 100,00 - 5000 0,002 0,600 Probe 16 CVD Poly-Kristall 0,3 100,00 - 10 150,000 0,350 Probe 17 CVD Poly-Kristall 40,0 99,99 W 5500 0,002 0,020 Probe 18 CVD Poly-Kristall 50,0 98,00 W 5500 0,002 0,020 Probe 19 CVD Poly-Kristall 80,0 70,00 W 5500 0,002 0,020 [Table 2] Table 2 Leitfähiges Diamantelement Maximaler Wert desDurchmessers desUmkreises (D) Länge desersten Bereichs (L) L / D ratio Diameter of the maximum incircle on the side of the first end section (d1) Diameter of the maximum incircle on the side of the second end section (d2) mm mm mm mm Sample 1 0,05 5,0 100,00 0,05 0,01 Sample 2 0,07 5,0 71,43 0,07 0,02 Sample 3 0,10 1,0 10,00 0,10 0,03 Sample 4 0,15 1,2 8,00 0,15 0,02 Sample 5 0,20 1,0 5,00 0,20 0,03 Sample 6 0,20 0,6 3,00 0,20 0,04 Sample 7 0,30 1,0 3,33 0,30 0,05 Sample 8 0,40 1,0 2,50 0,40 0,06 Sample 9 1,50 1,0 0,67 1,50 0,10 Sample 10 0,05 5,0 100,00 0,05 0,01 Sample 11 0,05 5,0 100,00 0,05 0,01 Sample 12 0,05 5,0 100,00 0,05 0,01 Sample 13 0,05 5,0 100,00 0,05 0,01 Sample 14 0,05 5,0 100,00 0,05 0,01 Sample 15 0,07 5,0 71,43 0,07 0,02 Sample 16 0,07 5,0 71,43 0,07 0,02 Sample 17 0,05 5,0 100,00 0,05 0,01 Sample 18 0,05 5,0 100,00 0,05 0,01 Sample 19 0,05 5,0 100,00 0,05 0,01

[0127] The cyclic voltammetry properties of the finished thin, needle-shaped diamond electrodes with the conductive diamonds were evaluated. The results are listed in Table 3. In the tables of this disclosure, the term "leakage current" refers to a current value at a low potential (potential window) in the CV measurement. In the tables of this disclosure, the letters A, B, C, and D in the "Signal Detection" column of the "CV Measurement" have the following meanings. A: Signal detectable. B: Signal detectable in a subset of the species. C: Signal detectable, but not detectable at low temperatures. D: Signal not detectable.

[0128] The diamond electrode of each sample was inserted into several cells of different sizes (one mouse brain cell and one pig brain cell) to assess the ease of insertion and the state of cell damage. The results are presented in Table 3. In the tables of this disclosure, A, B, C, and D in the "Ease of Insertion" column under "Insertion into Cell" have the following meanings. A: very easy to introduce into the cell. B: easy to insert into the cell. C: can be inserted into the cell. D: Can be introduced into the cell, but difficult to introduce into small cells.

[0129] In the tables of the present disclosure, A, B and C in the column “Damage to the cell” under “Introduction into the cell” mean the following. A: Cell not damaged. B: Cell partially damaged. C: Cell completely damaged. [Table 3] Table 3 Introduction to Cell CV measurement simplicity Cell damage Signal detection Leakage current µA Sample 1 A A A 0,03 Sample 2 A A A 0,04 Sample 3 B B A 0,15 Sample 4 A A A 0,08 Sample 5 B B A 0,30 Sample 6 C B A 3,00 Sample 7 C B A 3,00 Sample 8 D C B 30,00 Sample 9 D C B 60,00 Sample 10 A A A 0,03 Sample 11 A A A 0,02 Sample 12 A A A 0,01 Sample 13 A A A 0,01 Sample 14 A A C <0,00001 Sample 15 A A A >10 Sample 16 A A C <0,00001 Sample 17 A A A 0,03 Sample 18 A A A 0,02 Sample 19 A A D >100 [Example 2]

[0130] In Example 2, the conductive diamond plate was produced from a single-crystal diamond. First, a type Ib diamond in the form of a 10 mm square was produced as the single-crystal diamond using a high-pressure synthesis process. Three × 10 16 cm -2 Carbon ions were implanted at 350 keV, and a 50 µm layer of undoped single-crystal diamond was synthesized onto this layer. After synthesis of the single-crystal diamond, the ion-implanted layer was removed by applying a voltage in pure water, resulting in an undoped, self-supporting single-crystal diamond plate. A boron-doped diamond with a thickness of 50 µm to 300 µm was epitaxially synthesized using the undoped single-crystal diamond as a substrate. A self-supporting boron-doped diamond was produced to which the undoped substrate is attached. The diamond was produced by introducing methane gas into hydrogen and decomposing it in a microwave plasma. Alternatively, the diamond could be produced by thermal decomposition using a hot filament heated to 2000 °C. The boron impurity was added by incorporating a small amount of trimethylborane.This does not differ significantly from a general synthesis procedure. Since a single-crystal substrate in the form of a 10 mm square was used, a plate with a size of 10 mm could also be used. 2 as a conductive diamond substrate. The undominated single-crystal diamond, although bonded, could be removed in the next laser process. In sample 25, a thin tungsten wire with a diameter of approximately 19 µm was partially embedded at the time of diamond synthesis. When the diamond was later cut into a thin needle shape with a laser, the thin wire was embedded inside the needle-shaped diamond without being exposed at the surface.

[0131] Next, a rod-shaped diamond was cut from the conductive diamond in plate form using a laser processing system. The rod-shaped diamond was cut from a diamond with a plate thickness of 50 µm, resulting in a width of 50 µm, and the rod-shaped diamond was cut from a diamond with a plate thickness of 100 µm, resulting in a width of 100 µm. However, since the undoped single-crystal diamond is initially bonded, this undoped portion must ultimately be removed with a laser. In this way, the single-crystal rod could be formed into a 50 µm square or 100 µm square prism. The width of the diamond to be cut was adjusted according to the plate thickness, thus allowing the length of the prism face to be adjusted. Even if the cross-section was not exactly square but trapezoidal, there were no significant problems.The length is 10 mm, which corresponds to the length of one side of the substrate. A desired length can be achieved by laser cutting. To produce a rod with a diameter of 100 µm, the diagonal length was 100 µm if the thickness and width were both 70 µm, thus creating a rod circumscribed by a circle with a diameter of 100 µm.

[0132] In the same manner as in Example 1, it was also possible to produce a rod with a square pyramid shape with its apex as the vertex, a rod with a tip diameter of 5 µm or less, and a rod with a tip diameter of 0.7 µm. Furthermore, a graphite component adhering to the electrode by laser processing could be removed in the same way as in Example 1. Additionally, an electrode in which the conductive diamond and the SUS tube are structurally and electrically bonded could be produced in the same manner as in Example 1, and an insulating coating was obtained in a similar way. Thus, diamond electrodes of samples 20 to 25 with the specifications described in Tables 4 and 5 were obtained. [Table 4] Table 4 Conductive diamond element Manufacturing process crystal Grain diameter Level orientation Diamond content Other material boron content Resistance 12 / 13 µm Vol. ppm Ω·cm Sample 20 CVD single crystal - (100) 100 - 3500 0,002 0,001 Sample 21 CVD single crystal - (100) 100 - 3500 0,002 0,001 Sample 22 CVD single crystal - (100) 100 - 3500 0,002 0,001 Sample 23 CVD single crystal - (110) 100 - 2000 0,003 0,001 Sample 24 CVD single crystal - (111) 100 - 5000 0,001 0,001 Sample 25 CVD single crystal - (100) 70 W 5000 0,001 0 [Table 5] Table 5 Conductive diamond element Maximum value of the diameter of the circle (D) Length of the first section (L) L / D ratio Diameter of the maximum incircle on the side of the first end section (d1) Diameter of the maximum incircle on the side of the second end section (d2) mm mm mm mm Sample 20 0,05 5 100,00 0,05 0,01 Sample 21 0,07 5 71,43 0,07 0,02 Sample 22 0,50 5 10,00 0,50 0,08 Sample 23 0,05 5 100,00 0,05 0,02 Sample 24 0,05 5 100,00 0,05 0,02 Sample 25 0,05 5 100,00 0,05 0,02

[0133] The cyclic voltammetry properties of the finished thin, needle-shaped diamond electrodes with the conductive diamonds were evaluated. The results are shown in Table 6.

[0134] The diamond electrode of each sample was inserted into several cells of different sizes (one mouse brain cell and one pig brain cell) to assess insertability and cell damage. The results are shown in Table 6. [Table 6] Table 6 Introduction to Cell CV measurement simplicity Cell damage Signal detection Leakage current µA Sample 20 A A A 0,01 Sample 21 A A A 0,01 Sample 22 D C B 50 Sample 23 A A A 0,01 Sample 24 A A A 0,01 Sample 25 A A D >100 [Example 3]

[0135] In Example 3, a conductive diamond plate was fabricated from nanocrystalline diamond. In the conductive nanocrystalline diamond produced by the high-pressure, high-temperature (HPHT) process, boron is added to graphite for direct conversion, allowing the synthesis of a fully conductive nanocrystalline diamond. The nanocrystalline diamond, formed in bulk form, was laser-cut into a plate shape, thus producing a sheet material from the conductive nanocrystalline diamond. In sample 35, a thin tungsten (W) wire with a diameter of approximately 19 µm was partially embedded at the time of diamond synthesis. When the diamond was subsequently laser-cut into a thin needle shape, this thin wire was embedded within the needle-shaped diamond without being exposed at the surface.

[0136] The diamond electrode in the form of a thin diamond needle can be prepared in the same way as in Example 1 and Example 2. Diamond electrodes of samples 30 to 35 were obtained with the specifications described in Tables 7 and 8. [Table 7] Table 7 Conductive diamond element Manufacturing process crystal Grain diameter Diamond content Other material boron content Resistance 12 / 13 µm Vol. ppm Ω·cm Sample 30 HPHT crystal 1200 100 - 3000 0,02 0,01 Sample 31 HPHT crystal 500 100 - 3000 0,04 0,02 Sample 32 HPHT crystal 100 100 - 3000 0,03 0,03 Sample 33 HPHT crystal 10 100 - 200 20 0,01 Sample 34 HPHT crystal 100 100 - 8 500 0,01 Sample 35 HPHT crystal 100 70 W 8 500 0,01 [Table 8] Table 8 Conductive diamond element Maximum value of the diameter of the circumcircle (D) Length of the first area (L) L / D ratio Diameter of the maximum incircle on the side of the first end section (d1) Diameter of the maximum incircle on the side of the second end section (d2) mm mm mm mm Sample 30 0,05 5 100,00 0,05 0,01 Sample 31 0,07 5 71,43 0,07 0,02 Sample 32 0,09 5 55,56 0,09 0,01 Sample 33 0,05 5 100,00 0,05 0,02 Sample 34 0,05 5 100,00 0,05 0,02 Sample 35 0,05 5 100,00 0,05 0,02

[0137] The cyclic voltammetry properties of the finished thin, needle-shaped diamond electrodes with the conductive diamonds were evaluated. The results are listed in Table 9.

[0138] The diamond electrode of each sample was inserted into several cells of different sizes (one mouse brain cell and one pig brain cell) to assess insertability and cell damage status. The results are shown in Table 9. [Table 9] Table 9 Introduction to Cell CV measurement simplicity Cell damage Signal detection Leakage current µA Sample 30 A A A 0,05 Sample 31 A A A 0,03 Sample 32 A A A 0,04 Sample 33 A A A 0,01 Sample 34 A A C <0,00001 Sample 35 A A D >100 [Example 4]

[0139] In Example 4, a conductive diamond plate was fabricated from sintered diamond. The sintered diamond was produced as follows: diamond powder was calcined and solidified with a co-binder using a high-pressure process. In addition to the co-binder, boron was added to and incorporated into the diamond. The sintered diamond was polished into a thin plate and thinly sliced ​​by laser, allowing a diamond electrode in the form of a thin diamond needle to be produced in the same manner as in Examples 1 to 3. The thin, needle-shaped diamond was coated with diamond on its surface by a gas-phase synthesis process to prevent the co-binder from being exposed. Diamond electrodes of samples 40 to 42 with the specifications described in Tables 10 and 11 were obtained. [Table 10] Table 10 Conductive diamond element Manufacturing process crystal Grain diameter Diamond content Other material boron content Resistance 12 / 13 µm Vol. ppm Ω·cm Sample 40 HPHT Poly-crystal 15 90 Co 5500 0,002 0,02 Sample 41 HPHT Poly-crystal 1 80 Co 5500 0,002 0,02 Sample 42 HPHT Poly-crystal 0.5 70 Co 5500 0,002 0,02 [Table 11] Table 11 Conductive Diamond Member Maximum value of the diameter of the circle (D) Length of the first area (L) L / D ratio Diameter of the maximum incircle on the side of the first end section (d1) Diameter of the maximum incircle on the side of the second end section (d2) mm mm mm mm Sample 40 0,09 5 55,56 0,09 0,03 Sample 41 0,09 5 55,56 0,09 0,03 Sample 42 0,09 5 55,56 0,09 0,03

[0140] The cyclic voltammetry properties of the finished thin, needle-shaped diamond electrodes with the conductive diamonds were evaluated. The results are shown in Table 12.

[0141] The diamond electrode of each sample was inserted into several cells of different sizes (one mouse brain cell and one pig brain cell) to assess insertability and cell damage status. The results are presented in Table 12. [Table 12] Table 12 Introduction to Cell CV measurement simplicity Cell damage Signal detection Leakage current µA Sample 40 B B A 0,50 Sample 41 B B A 4,00 Sample 42 B B D >100

[0142] Although the embodiments and examples of the present disclosure are listed as described above, it is sometimes to be expected that the configurations of the embodiments and examples described above may be combined in a suitable manner or modified in various ways.

[0143] The embodiments and examples disclosed herein are illustrative and in no way limiting. The scope of the present invention is defined by the formulation of the claims and not by the embodiments and examples described above, and is intended to include all modifications within the scope and meaning that correspond to the formulation of the claims. List of reference symbols

[0144] 1 Diamond electrode; 2 Conductive diamond element; 2a First end section; 2b Second end section; 3 Metal element; 3a Third-A end section; 3b Third-B end section; 4 Insulating element; 5 Solder material; 6 Adhesive; 7 Metal coating; 8 Joining aid; 21 First area; 20 Diamond plate; C1 Circumscribed circle; C2, C3 Largest inscribed circle. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023

[0001] JP 115406

[0001] < / isolierelement> < / metallelement> < / aufbau>

Claims

[1] Diamond electrode, comprising: a conductive diamond element in rod form; and a rod-shaped metal element electrically connected to the conductive diamond element, wherein The diamond content of the conductive diamond element is greater than or equal to 80 vol.%. [2] Diamond electrode according to claim 1, wherein the conductive diamond element has a first area that is exposed to the outside, a maximum value D of a diameter of a circumcircle of a cross-section of the first region is less than or equal to 0.3 mm, the cross-section is a cross-section in which one direction of extension of the conductive diamond element is considered the normal direction, and the specific resistance of the conductive diamond element is less than or equal to 1000 Ω·cm. [3] Diamond electrode according to claim 2, wherein the ratio L / D of the length L of the first region along the extension direction to D is greater than or equal to 1. [4] Diamond electrode according to any one of claims 1 to 3, wherein the conductive diamond element has a first end section on the side of the metal element and a second end section on a side opposite the first end section, a diameter d2 of a maximum incircle of the conductive diamond element on the side of the second end section is smaller than a diameter d1 of a maximum incircle of the conductive diamond element on the side of the first end section, where d2 is less than or equal to 0.05 mm and d1 and d2 are each measured by viewing the conductive diamond element from the side. [5] Diamond electrode according to any one of claims 1 to 4, wherein the conductive diamond element is made of diamond, and a boron content of the diamond greater than or equal to 10 ppm and less than or equal to 50000 ppm. [6] Diamond electrode according to one of claims 1 to 5, wherein in a Raman spectrum of the conductive diamond element a percentage (I2 / I3) × 100 of a peak intensity I2 of a peak with a half width of greater than 50 cm -1 at a wave number greater than or equal to 1545 cm -1 and less than or equal to 1600 cm -1 with respect to a peak intensity I3 of a peak with a half-width of less than or equal to 20 cm -1 at a wave number greater than or equal to 1320 cm -1 and less than or equal to 1340 cm -1 is less than or equal to 30%. [7] Diamond electrode according to any one of claims 1 to 6, wherein an angle between an extension direction of the conductive diamond element and an extension direction of the metal element is less than or equal to 5°, and a connecting section between the conductive diamond element and the metal element is covered with an insulating element. [8] Diamond electrode according to any one of claims 1 to 7, wherein the metal element has a tubular shape. [9] Diamond electrode according to claim 7, wherein the insulating element is made of polyimide. [10] Diamond electrode according to claim 7, wherein the insulating element is made of a cross-linked fluorinated resin. [11] Diamond electrode according to claim 7, wherein the average thickness of the insulating element is greater than or equal to 5 µm and less than or equal to 50 µm. [12] Diamond electrode according to any one of claims 1 to 11, wherein the conductive diamond element is made of single-crystal diamond. [13] Diamond electrode according to any one of claims 1 to 11, wherein the conductive diamond element is made of polycrystalline diamond, and the average grain size of the polycrystalline diamond is larger than the diameter d2 of a maximum incircle of the conductive diamond element on the side of a second end section of the conductive diamond element opposite a first end section of the conductive diamond element on the side of the metal element. [14] Diamond electrode according to any one of claims 1 to 11, wherein the conductive diamond element is made of nanopolycrystalline diamond.

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