electrode

Abstract

This electrode (1) comprises a base material (2) and a conductive carbon layer (3) in sequence toward one side in the thickness direction. The conductive carbon layer (3) contains less than 10% by atom of gold nanoparticles that are dispersed in the conductive carbon layer (3). The conductive carbon layer (3) contains atoms to be sp3-bonded and atoms to be sp2-bonded. The ratio of the atoms to be sp3-bonded to the sum of the atoms to be sp3-bonded and the atoms to be sp2-bonded ((sp3) / (sp3 + sp2)) is 0.25 or more.

Description

Technical Field

[0001] The present invention relates to an electrode.

Background Art

[0002] An electrode including a conductive carbon layer in which gold nanoparticles are dispersed is known (see Patent Document 1 below). Patent Document 1 discloses that the content of gold nanoparticles in the conductive carbon layer is from 10 atomic % to 22 atomic %. Further, in Example 2 of Patent Document 1, the content of gold nanoparticles is 17 atomic %. Further, in the conductive carbon layer of Example 2, the proportion of atoms bonded by sp 3 bonding to the total of atoms bonded by sp 2 bonding and atoms bonded by sp 3 bonding (sp 3 / (sp 3 +sp 2 )) is as low as 0.2 .

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the proportion of atoms bonded by sp 3 bonding (sp 3 / (sp 3 +sp 2 )) is relatively low at 0.2 , if the content of gold nanoparticles is 10 atomic % or more as disclosed in Patent Document 1, strong signal intensity can be obtained.

[0005] On the other hand, if the concentration of the measurement target of the electrode is low, weak signal intensity is obtained, so a high signal-to-noise ratio (S / N ratio) is required.

[0006] However, the electrode described in Patent Document 1 has the drawback that it cannot obtain the high signal-to-noise ratio mentioned above.

[0007] The present invention provides an electrode having a high signal-to-noise ratio. [Means for solving the problem]

[0008] Therefore, the inventors of this case, sp 3 The ratio of atoms that bond (sp 3 / (sp 3 +way 2 Surprisingly, we discovered that if the ratio is high, such as 0.25 or higher, a high signal-to-noise ratio can be obtained by reducing the gold nanoparticle content to less than 10 atomic percent, thus completing the present invention.

[0009] The present invention (1) comprises a substrate and a conductive carbon layer in order toward one side in the thickness direction, wherein the conductive carbon layer contains less than 10 atomic percent of gold nanoparticles dispersed in the conductive carbon layer, and the conductive carbon layer is sp 3 The atoms that bond and sp 2 It contains the atoms that bond, sp 3 Bonding atoms and sp 2 sp for the total of the atoms being bonded 3 The ratio of atoms that bond (sp 3 / (sp 3 +way 2 The electrode includes a value of 0.25 or greater.

[0010] The present invention (2) includes the electrode described in (1), wherein the content of the gold nanoparticles in the conductive carbon layer is less than 5 atomic percent. [Effects of the Invention]

[0011] The electrode of the present invention can achieve a high signal-to-noise ratio. [Brief explanation of the drawing]

[0012] [Figure 1]This is a cross-sectional view of an electrode from HMC. [Modes for carrying out the invention]

[0013] <One Embodiment> One embodiment of the electrode of the present invention will be described with reference to Figure 1.

[0014] <Electrode 1> As shown in Figure 1, the electrode 1 extends in a plane direction perpendicular to the thickness direction. The electrode 1 has one surface in the thickness direction and another surface that is spaced apart from the first surface in the thickness direction.

[0015] The electrode 1 comprises a base material 2 and a conductive carbon layer 3 disposed on one side of the base material 2 in the thickness direction. That is, the electrode 1 comprises the base material 2 and the conductive carbon layer 3 in order on one side in the thickness direction. Preferably, the electrode 1 comprises only the base material 2 and the conductive carbon layer 3.

[0016] <Base material 2> The substrate 2 forms the other surface of the electrode 1 in the thickness direction. Examples of substrate 2 include inorganic substrates and organic substrates. Examples of inorganic substrates include silicon and glass. Examples of organic substrates include polyethylene terephthalate. Other known materials can also be preferably used as the material for substrate 2. Preferably, from the viewpoint of electrode activity, an inorganic substrate is used, and more preferably, silicon is used. When the material of substrate 2 is silicon, substrate 2 is prepared, for example, as a silicon wafer.

[0017] The thickness of the base material 2 is not limited. The thickness of the base material 2 is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and also, for example, 1000 μm or less, preferably 500 μm, more preferably 100 μm or less.

[0018] <Conductive carbon layer 3> The conductive carbon layer 3 forms one surface in the thickness direction of the electrode 1. The conductive carbon layer 3 is conductive. The conductive carbon layer 3 is in contact with one surface in the thickness direction of the substrate 2.

[0019] The conductive carbon layer 3 contains a plurality of gold nanoparticles 5. The plurality of gold nanoparticles 5 are dispersed in the conductive carbon layer 3. Specifically, the conductive carbon layer 3 contains, for example, a carbon matrix 4 and a plurality of gold nanoparticles 5.

[0020] The carbon matrix 4 is the main part of the conductive carbon layer 3.

[0021] Carbon Matrix 4 is sp 2 Bonding carbon and sp 3 It contains carbon atoms with bonds. That is, the carbon matrix 4 is a microcrystalline domain having graphite-type and diamond-type structures. As a result, the conductive carbon layer 3 has good conductivity while possessing a chemically stable structure and low background noise. Consequently, the sensitivity to the object being measured is significantly improved.

[0022] In the conductive carbon layer 3, sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 )) is 0.25 or greater.

[0023] In the conductive carbon layer 3, sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 If the value is less than 0.25, the signal-to-noise ratio will be low.

[0024] In the conductive carbon layer 3, sp 3Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 )) is preferably 0.30 or higher, more preferably 0.35 or higher, and even more preferably 0.40 or higher.

[0025] In the conductive carbon layer 3, sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 )) is preferably 0.95 or less, more preferably 0.90 or less, even more preferably 0.75 or less, and particularly preferably 0.60 or less. 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 If the above-mentioned upper limit is below this value, excellent conductivity can be ensured in the conductive carbon layer 3.

[0026] sp 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 The measurement method for )) will be described in a later example.

[0027] Furthermore, the carbon matrix 4 may contain trace amounts of unavoidable impurities. Examples of unavoidable impurities include oxygen, argon, and nitrogen.

[0028] The gold nanoparticles 5 are uniformly dispersed in the carbon matrix 4. The median diameter of the gold nanoparticles 5 is, for example, 0.1 nm or more, preferably 1 nm or more, and for example, 20 nm or less, preferably 10 nm or less.

[0029] Some of the multiple gold nanoparticles 5 are exposed from one side in the thickness direction of the carbon matrix 4. In this embodiment, in the conductive carbon layer 3, the tip (one end edge) of the exposed gold nanoparticles 5 is located on the far right side in the thickness direction.

[0030] The gold nanoparticle content 5 in the conductive carbon layer 3 is less than 10 atomic percent.

[0031] In the conductive carbon layer 3, sp 3 The ratio of the number of atoms to bond (sp 3 / (sp 3 +way 2 When )) is 0.25 or higher, the signal-to-noise ratio will be lower if the content of gold nanoparticles 5 in the conductive carbon layer 3 is 10 atomic percent or higher.

[0032] The content of gold nanoparticles 5 in the conductive carbon layer 3 is preferably 9 atomic% or less, more preferably 7 atomic% or less, even more preferably 6 atomic% or less, particularly preferably 5 atomic% or less, even more preferably less than 5 atomic%, even more preferably 4 atomic% or less, and even more preferably 3 atomic% or less.

[0033] The lower limit of the gold nanoparticle content 5 in the conductive carbon layer 3 is not limited. The gold nanoparticle content 5 in the conductive carbon layer 3 is, for example, more than 0 atomic%, preferably 0.1 atomic% or more, more preferably 0.5 atomic% or more, even more preferably 1 atomic% or more, and particularly preferably 2 atomic% or more.

[0034] The proportion of gold nanoparticles 5 in the conductive carbon layer 3 will be described in a later example.

[0035] The thickness of the conductive carbon layer 3 is, for example, 0.1 nm or more, preferably 0.2 nm or more, and 100 nm or less, preferably 50 nm or less.

[0036] The surface resistance Rs on one side in the thickness direction of the conductive carbon layer 3 is, for example, 1.0 × 10⁻⁶.4 Ω / □ or less, preferably 1.0 × 10 3 It is less than or equal to Ω / □.

[0037] The thickness of electrode 1 is the total thickness of the substrate 2 and the conductive carbon layer 3, and specifically, for example, is 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less, more preferably 100 μm or less.

[0038] <Method for manufacturing electrode 1> Next, we will explain how to manufacture electrode 1.

[0039] First, in this method, base material 2 is prepared.

[0040] Next, a conductive carbon layer 3 is formed on one side of the substrate 2 in the thickness direction. A dry method is used to form the conductive carbon layer 3. Examples of dry methods include PVD (physical vapor deposition) and CVD (chemical vapor deposition). The PVD method is preferred as the dry method. Examples of PVD methods include sputtering, vacuum deposition, laser deposition, and ion plating (arc deposition). Preferably, sputtering is used.

[0041] Examples of sputtering methods include unbalanced magnetron sputtering (UBM sputtering), high-power pulsed sputtering, electron cyclotron resonance sputtering, RF sputtering, DC sputtering (DC magnetron sputtering), DC pulsed sputtering, and ion beam sputtering. More preferably, UBM sputtering is used.

[0042] Examples of targets used in sputtering include sintered carbon and gold. The targets are provided in the sputtering apparatus. Two targets are provided in the sputtering apparatus. The sputtering apparatus also includes, for example, a film-forming member. Examples of film-forming members include a film-forming plate (film-forming substrate) and a film-forming roll. The film-forming member is positioned opposite the target with a gap between them. Desired power and voltage can be applied to each of the targets and the film-forming member. The power and voltage depend on the content of gold nanoparticles 5 and the sp in the conductive carbon layer 3. 3 The voltage is set appropriately according to the ratio of these factors. The voltage applied to the film deposition material is called the ion acceleration voltage because it has the effect of accelerating the speed of sputtering gas ions that collide with the film deposition material.

[0043] Examples of sputtering gases introduced into a sputtering apparatus include inert gases. These inert gases include, for example, argon. The pressure during sputtering is, for example, 1 Pa or less.

[0044] This results in an electrode 1 having a base material 2 and a conductive carbon layer 3 arranged sequentially on one side in the thickness direction.

[0045] <Applications of Electrode 1> Electrode 1 can be used as various types of electrodes, and is preferably an electrode for electrochemical measurements to be performed using electrochemical measurement methods, specifically as a working electrode for cyclic voltammetry (CV), square wave voltammetry (SWV), anodic stripping voltammetry (ASV), and amperometry.

[0046] In particular, electrode 1 is suitably used as an electrode (working electrode) with a high signal-to-noise ratio for metal elements classified in groups 14 to 15 of the periodic table as defined by IUPAC in 2019. Electrode 1 is preferably used as an electrode (working electrode) with a high signal-to-noise ratio for metal elements of group 15, and more preferably as an electrode (working electrode) with a high signal-to-noise ratio for arsenic (specifically, trivalent arsenic ions).

[0047] <Effects of one embodiment> In this electrode 1, the conductive carbon layer 3 contains less than 10 atomic percent of gold nanoparticles 5, sp 3 The ratio of atoms that bond (sp 3 / (sp 3 +way 2 Since the value is 0.25 or higher, the signal-to-noise ratio is high.

[0048] In particular, if this electrode 1 is used as an electrode for measuring metal elements classified in groups 14 to 15, specifically arsenic, a high signal-to-noise ratio can be obtained.

[0049] <Variation> In the modified examples, components and processes similar to those in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted. Furthermore, the modified examples can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modified examples can be combined as appropriate.

[0050] As shown in Figure 1, in one embodiment, the electrode 1 comprises one substrate 2 and one conductive carbon layer 3. In a modified example, although not shown, the electrode 1 comprises one substrate 2 and multiple (specifically, two) conductive carbon layers 3. In other words, the electrode 1 can be provided with a number (specifically, two) conductive carbon layers 3 on a single substrate 2. When the electrode 1 comprises two conductive carbon layers 3, the conductive carbon layers 3, the substrate 2, and the conductive carbon layers 3 are arranged sequentially in the thickness direction. The conductive carbon layer 3 arranged on the other side of the substrate 2 in the thickness direction is formed by the same method as the conductive carbon layer 3 arranged on one side of the substrate 2 in the thickness direction.

[0051] One or more functional layers may be further provided between the substrate 2 and the conductive carbon layer 3, or on the underside of the substrate 2. Examples of functional layers include a base layer, a gas barrier layer, a conductive layer, an adhesion layer, and a surface smoothing layer. [Examples]

[0052] The present invention will be further described below with reference to examples and comparative examples. However, the present invention is not limited in any way to the examples and comparative examples. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than or equal to") of the blending ratios (content ratios), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0053] <Example 1> A substrate 2 consisting of a silicon wafer with a thickness of 280 μm was prepared.

[0054] Next, the substrate 2 was placed in the sputtering apparatus. The sputtering apparatus comprises a first target, a second target, and a deposition plate, all independently. By sputtering using this apparatus, a conductive carbon layer 3 with a target thickness of 40 nm was formed on one side of the substrate 2 in the thickness direction. This produced an electrode 1 comprising the substrate 2 and the conductive carbon layer 3 in which gold nanoparticles 5 were dispersed. The sputtering conditions were as follows.

[0055] Target 1: Sintered carbon Second target: Gold Sputtering gas: Argon Pressure: 0.6 Pa Voltage applied to the film deposition plate (ion acceleration voltage): 75V Power applied to the first target: 400W Power applied to the second target: 50W

[0056] <Examples 2 to 4, Comparative Examples 1 to 4> Electrode 1 was manufactured in the same manner as in Example 1. However, the voltage applied to the film deposition plate, the power applied to the first target, and the power applied to the second target were changed as shown in Table 1.

[0057] <Rating> The following aspects were evaluated for Electrode 1 in Examples 1 to 4 and Comparative Examples 1 to 4.

[0058] (1) The content ratio of gold nanoparticles in the conductive carbon layer 3, and sp 3 / (sp 3 +way 2 ) The content ratio of gold nanoparticles 5 in the conductive carbon layer 3, and sp 3 / (sp 3 +way 2 The results were observed using X-ray photoelectron spectroscopy (XPS, Shimadzu Corporation).

[0059] (2) Signal-to-noise ratio when measuring low-concentration arsenic ions (trivalent) A sample electrode with a known electrode area was prepared by attaching insulating tape with a 2 mm diameter hole to one side of the conductive carbon layer 3. This sample electrode was used as the working electrode and inserted into a 0.05 MH2SO4 aqueous solution, then connected to a potentiostat (CHI Instruments, ALS730C). Similarly, a reference electrode (Ag / AgCl) and a counter electrode (Pt) were also inserted into an H2SO4 solution and connected to the potentiostat.

[0060] Next, H2SO4 aqueous solutions were prepared with arsenic ion (trivalent) concentrations of 0 ppb and 100 ppb, respectively. The reduction deposition potential was set to -0.8 V and the deposition time to 120 seconds, and arsenic ions (trivalent) were reduced and deposited onto electrode 1. Subsequently, square wave voltammetry (SWV) measurements were performed for each concentration with a frequency of 50 Hz, a potential increase of 3 mV, and an amplitude of 25 mV, and SWV curves were obtained. In the obtained SWV curves, the signal-to-noise ratio (S / N ratio) was determined from the ratio of the peak response current value originating from arsenic ions (trivalent), observed around 0.2 V for the 100 ppb solution, to the current value at the same potential as that peak (noise equivalent value) for the 0 ppb solution.

[0061] [Table 1]

[0062] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims below. [Industrial applicability]

[0063] Electrodes are used, for example, as electrodes for electrochemical measurements. [Explanation of Symbols]

[0064] 1 electrode 2 Base material 3. Conductive carbon layer

Claims

1. The substrate and the conductive carbon layer are arranged sequentially toward one side in the thickness direction. The conductive carbon layer contains 9 atomic percent or less of gold nanoparticles dispersed in the conductive carbon layer. The conductive carbon layer is sp ３ The atoms that bond and sp ２ Includes atoms that bond, sp ３ Bonding atoms and sp ２ sp relative to the sum of the atoms being bonded ３ The proportion of atoms that bond (sp ３ / (sp ３ +sp ２ An electrode in which the ratio is 0.25 or higher.

2. The electrode according to claim 1, wherein the content of gold nanoparticles in the conductive carbon layer is less than 5 atomic percent.

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