JP7229520B2 - Oxygen electrode and measuring device - Google Patents

Description

The present invention relates to oxygen electrodes and measuring devices.

2. Description of the Related Art Conventionally, an oxygen electrode used for measuring dissolved oxygen concentration in a liquid is known (see, for example, Patent Document 1). In this oxygen electrode, when a voltage is applied between the cathode and anode that are in contact with the electrolyte, a current corresponding to the dissolved oxygen concentration flows through the electrolyte, so the dissolved oxygen concentration can be measured.

By the way, the oxygen electrode of Patent Document 1 evaporates the water in the electrolyte during manufacturing, so that the electrolyte is in a state where there is no water, and the dissolved oxygen concentration cannot be measured. Therefore, in order to make the oxygen electrode function, the electrolyte is activated by supplying moisture to the electrolyte through the oxygen-permeable membrane by, for example, immersing it in water at room temperature overnight.

JP-A-10-78407

However, the oxygen electrode of Patent Literature 1 has a problem that the response to the applied voltage is unstable due to evaporation of at least part of the moisture in the electrolyte after the activation of the electrolyte.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an oxygen electrode and a measuring device that have a stable response to an applied voltage.

To solve the above problems and achieve the object, an oxygen electrode according to one aspect of the present invention comprises a cathode formed on a substrate, an anode formed on the substrate, the cathode and the A sheet of paper placed over at least a portion of the anode and impregnated with an electrolyte consisting of potassium chloride (KCl), a buffer component consisting of Tris-HCl, a humectant, and polyvinylpyrrolidone. a member, a spacer having substantially the same thickness as the sheet member and disposed so as to surround an edge of the sheet member, and an oxygen-permeable membrane covering the sheet member and the spacer. .

Further, the oxygen electrode according to one aspect of the present invention is characterized in that the humectant contains at least one of sucrose, glucose, and sorbitol.

Further, a measuring device according to an aspect of the present invention is characterized by comprising an oxygen electrode and a sample injection part placed on the oxygen permeable membrane and capable of injecting a sample.

Moreover, the measuring device according to one aspect of the present invention is characterized in that a plurality of sets of the cathode and the anode are formed.

ADVANTAGE OF THE INVENTION According to this invention, the oxygen electrode and measuring device which are stable in the response with respect to the applied voltage can be implement|achieved.

FIG. 1 is an exploded perspective view showing the configuration of an oxygen electrode according to an embodiment of the invention. FIG. 2 is an A arrow view of the oxygen electrode shown in FIG. FIG. 3 is a cross-sectional view corresponding to line BB of FIG. FIG. 4 is a diagram showing changes in current over time when the time for immersion in water is changed. FIG. 5 is a diagram showing changes in current over time when the potential applied between the electrodes is changed. FIG. 6 is a diagram showing changes in current over time with and without a moisturizing agent. FIG. 7 is a cross-sectional view of an oxygen electrode according to a modification.

Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

Moreover, in the description of the drawings, the same or corresponding elements are given the same reference numerals as appropriate. Also, it should be noted that the drawings are schematic, and the relationship of dimensions of each element, the ratio of each element, and the like may differ from reality. Even between the drawings, there are cases where portions with different dimensional relationships and ratios are included.

(Embodiment)
[Structure of oxygen electrode]
FIG. 1 is an exploded perspective view showing the configuration of an oxygen electrode according to an embodiment of the invention. FIG. 2 is an A arrow view of the oxygen electrode shown in FIG. FIG. 3 is a cross-sectional view corresponding to line BB of FIG. As shown in FIGS. 1 to 3, the oxygen electrode 1 according to this embodiment includes a substrate 2, a cathode 3, a wiring 4, an electrode pad 5, an anode 6, a wiring 7, an electrode pad 8, It has an insulating layer 9 , a sheet member 10 and an oxygen permeable film 11 .

The substrate 2 is a flat substrate made of glass.

The cathode 3 is formed on the substrate 2 and has, for example, a circular shape, but the shape is not particularly limited. The cathode 3 is made of platinum (Pt), but may be gold (Au) or silver (Ag).

The wiring 4 electrically connects the cathode 3 and the electrode pad 5 .

The electrode pads 5 are electrically connected to the outside. The electrode pad 5 is used when applying a voltage between the cathode 3 and the anode 6, for example.

The anode 6 is formed on the substrate 2 and arranged concentrically around the cathode 3, but the shape is not particularly limited. The anode 6 is made of silver (Ag), but may be lead (Pb). Also, when the anode 6 is silver, when an electric current is applied, chloride ions in the electrolyte react with the anode 6 to form silver chloride (AgCl).

The wiring 7 electrically connects the anode 6 and the electrode pad 8 .

The electrode pads 8 are electrically connected to the outside. The electrode pad 8 is used when applying a voltage between the cathode 3 and the anode 6, for example.

The insulating layer 9 exposes the cathode 3 , the anode 6 and the electrode pads 5 and 8 , and covers the other portions including the wirings 4 and 7 . may In addition, when most of the anode 6 is covered with the insulating layer 9 and only the end portion on the cathode 3 side is partially exposed, silver chloride is quickly formed to stabilize the current value and to extend the service life. can be made compatible. The insulating layer 9 is made of, for example, polyimide, but any material having insulating properties may be used.

A sheet member 10 (electrolyte layer) is placed on the cathode 3 and the anode 6 and contains an electrolyte and a humectant. Specifically, the sheet member 10 is paper placed on at least part of the cathode 3 and the anode 6 . Since the sheet member 10 is in contact with both the cathode 3 and the anode 6, when a voltage is applied between the cathode 3 and the anode 6, current flows according to the conditions such as dissolved oxygen concentration. As the electrolyte layer, a liquid containing an electrolyte and a moisturizing agent may be injected into the lower layer of the oxygen permeable membrane 11 . Also, as an electrolyte layer, a paste containing an electrolyte and a moisturizing agent may be applied on the cathode 3 and the anode 6 . Since the electrolyte layer contains a humectant, evaporation of water from the electrolyte layer is suppressed, and the response of the oxygen electrode 1 is stabilized.

The sheet member 10 is, for example, paper having a circular shape with a diameter of 7.0 mm and a thickness of 20 μm. The sheet member 10 may be made of a material that has a uniform thickness and can be impregnated with a liquid containing an electrolyte and a moisturizing agent, such as cloth or non-woven fabric. Since a homogeneous electrolyte layer is formed by the uniform thickness of the sheet member 10, the response of the oxygen electrode 1 is stabilized. Furthermore, the mechanical strength is improved by using the sheet member 10, so that the response of the oxygen electrode 1 is stabilized. The thickness of the sheet member 10 can be appropriately selected depending on the material, and is, for example, 10 μm to several hundred μm, and may be any thickness that provides sufficient strength. The shape of the sheet member 10 can be changed according to the shapes of the cathode 3 and the anode 6, and it is sufficient that at least a portion of the sheet member 10 is in contact with the cathode 3 and the anode 6. FIG.

The sheet member 10 contains 2.0 M KCl as an electrolyte, 2.0 M Tris-HCl as a buffer component for adjusting pH, 5.0 wt % sorbitol as a moisturizing agent, and an adhesive to the substrate 2. These components are impregnated by soaking the paper in a solution containing 4.0 wt % polyvinylpyrrolidone as the By immersing the sheet member 10 of paper in this solution, the sheet member 10 is uniformly impregnated with the electrolyte, so that the response of the oxygen electrode 1 is stabilized. Moisturizers are not limited to sucrose, and may be, for example, glucose or sorbitol. Electrolytes, buffer components, and adhesives are also examples, and materials and amounts can be changed as appropriate.

The oxygen permeable film 11 is formed so as to cover the sheet member 10 . The oxygen permeable membrane 11 is made of silicone, for example.

[Method for producing oxygen electrode]
Next, a method for manufacturing the oxygen electrode 1 will be described.

1. Cleaning of Substrate First, the glass substrate, which is the substrate 2, is cleaned. Specifically, the substrate 2 is immersed in a boiling aqueous solution of 25 wt % ammonia water, 30 wt % hydrogen peroxide water, and pure water at a ratio of 1:1:4 for 5 minutes. . Thereafter, the substrate 2 is immersed in boiling pure water for 5 minutes and rinsed. Further, the substrate 2 is immersed in another boiling pure water for 5 minutes, rinsed, and dried naturally.

2. Formation of Cathode Subsequently, a platinum electrode is formed as the cathode 3 . First, a positive photoresist is formed on the washed substrate 2 by spin coating at 500 rpm for 5 seconds and 2000 rpm for 10 seconds. After that, it is baked in a dry oven at 80° C. for 30 minutes. Then, it is allowed to cool naturally in a dark place for 15 minutes or more.

Using a mask, exposure is performed for 40 seconds with G line (wavelength 436 nm) of a mask aligner. After that, it is immersed in toluene at 30° C. for 40 seconds, baked in a dry oven at 80° C. for 15 minutes, and allowed to cool naturally in a dark place for 15 minutes or longer. After that, it is developed with a developer for 60 seconds (with stirring), rinsed with distilled water, and dried with nitrogen gas.

After performing dry etching for 5 minutes at an output of 200 W and an argon atmosphere of about 0.55 Pa using a sputtering apparatus, chromium, which will be an adhesion layer of the platinum layer, is sputtered for 5 minutes (about 30 nm) at an output of 100 W and an argon atmosphere of about 0.35 Pa. . Subsequently, platinum is sputtered twice for 15 minutes at an output of 100 W and an argon atmosphere of about 0.35 Pa for a total of 30 minutes (about 300 nm).

After that, the substrate 2 on which platinum has been sputtered is immersed in acetone for one hour. Furthermore, unnecessary portions other than the platinum layer are peeled off using a cotton swab. The cathode 3 is then formed by rinsing with distilled water and drying with nitrogen gas.

3. Formation of Anode Subsequently, a silver electrode is formed as the anode 6 . First, a positive photoresist is formed on the washed substrate 2 by spin coating at 500 rpm for 5 seconds and 2000 rpm for 10 seconds. After that, it is baked in a dry oven at 80° C. for 30 minutes. Then, it is allowed to cool naturally in a dark place for 15 minutes or more.

Using a mask, exposure is performed for 40 seconds with G line (wavelength 436 nm) of a mask aligner. After that, it is immersed in toluene at 30° C. for 40 seconds, baked in a dry oven at 80° C. for 15 minutes, and allowed to cool naturally in a dark place for 15 minutes or more. After that, it is developed with a developer for 60 seconds (with stirring), rinsed with distilled water, and dried with nitrogen gas.

After performing dry etching for 5 minutes with a sputtering apparatus at an output of 200 W and an argon atmosphere of about 0.55 Pa, silver is sputtered twice for 15 minutes at an output of 100 W and an argon atmosphere of about 0.35 Pa for a total of 30 minutes (about 550 nm). .

Thereafter, the substrate 2 on which platinum and silver have been sputtered is immersed in acetone for 1 hour, and a cotton swab is used to remove unnecessary portions other than the silver. The anode 6 is then formed by rinsing with distilled water and drying with nitrogen gas.

4. Formation of Insulating Layer Subsequently, a polyimide layer is formed as the insulating layer 9 . First, a polyimide prepolymer is formed on the substrate 2 by spin coating at 500 rpm for 10 seconds and 2000 rpm for 5 seconds. After that, it is baked in a dry oven at 80° C. for 30 minutes.

A positive photoresist is formed on the substrate 2 on which the polyimide layer is formed by spin coating at 500 rpm for 5 seconds and 2000 rpm for 10 seconds. After that, it is baked in a dry oven at 80° C. for 30 minutes.

After baking, the substrate is cooled in a dark place for about 10 minutes, and then exposed to the G line of a mask aligner for 40 seconds using a mask.

After the exposure, the substrate 2 is immersed in the developer for 120 seconds (with stirring, about 3 rotations/second, and the temperature of the developer is adjusted to about 25° C.), and immediately after that, it is cleaned with an ultrasonic cleaner for 10 seconds. After that, the surface is rinsed with distilled water, and the size of the hole, etc. are confirmed with a microscope.

The substrate 2 is immersed in ethanol and stirred for 5 minutes to remove the resist layer. It is then rinsed with ethanol and dried with nitrogen gas. Then, by heating on a hot plate at 150° C. for 15 minutes, 250° C. for 15 minutes, and 280° C. for 30 minutes, the polyimide is denatured and the insulating layer 9 is formed. Light is blocked during heating.

5. Formation of Sheet Member Subsequently, the sheet member 10 is formed. First, a solution containing 2.0 M KCl, 2.0 M Tris-HCl, 5.0 wt % sorbitol, and 4.0 wt % polyvinylpyrrolidone is prepared. The solution is then impregnated into a 20 μm thick paper cut into a circle with a diameter of 7.0 mm. Further, the sheet member 10 is formed by placing this paper on the cathode 3 and the anode 6 and drying it naturally.

6. Formation of Oxygen Permeable Film Subsequently, the oxygen permeable film 11 is formed. Specifically, the oxygen permeable film 11 is formed by spin-coating silicone at 1500 rpm for 10 seconds.

[Activation of Electrolyte of Oxygen Electrode]
Next, the time for immersion in water for activating the electrolyte of the oxygen electrode 1 will be described. Since the oxygen permeable membrane 11 allows only gas to pass therethrough, when the oxygen electrode 1 is immersed in water, water vapor passes through the oxygen permeable membrane 11 and water is supplied to the sheet member 10 to activate the electrolyte. After the oxygen electrode 1 was immersed in water for 29 hours, 24 hours, and 5 hours, a voltage of −0.8 V was applied between the cathode 3 and the anode 6, and changes in current over time were measured.

FIG. 4 is a diagram showing changes in current over time when the time for immersion in water is changed. The vertical axis in FIG. 4 represents current, and the horizontal axis represents time. The line L1 is the measurement result when the immersion time is 29 hours, the line L2 is the measurement result when the immersion time is 24 hours, and the line L3 is the measurement result when the immersion time is 5 hours. As shown in FIG. 4, the longer the immersion time in water, the greater the power generated with respect to the applied voltage. At time zero, the oxygen electrode 1 was taken out of the water, and sodium sulfite (Na ₂ SO ₃ ), which is an oxygen scavenger, was applied. Then, as the time passed from zero, the dissolved oxygen concentration decreased due to the oxygen scavenger, and the current also decreased. .

From the above, it was shown that the longer the oxygen electrode 1 is immersed in water, the better the response to the applied voltage. However, if the oxygen electrode 1 is kept immersed in water for a long time, the sheet member 10 may be damaged. When the oxygen electrode 1 is immersed in water for about 24 hours, the electrolyte with which the sheet member 10 is impregnated is sufficiently activated, and the oxygen electrode 1 is ready to function.

[Voltage applied to oxygen electrode]
Next, the voltage applied between the cathode 3 and the anode 6 of the oxygen electrode 1 will be explained. Voltages of −0.7 V, −0.8 V, and −0.9 V were applied between the cathode 3 and the anode 6, and changes in current over time were measured.

FIG. 5 is a diagram showing changes in current over time when the potential applied between the electrodes is changed. The vertical axis in FIG. 5 represents current, and the horizontal axis represents time. Line L11 is the measurement result when the applied voltage is -0.7V, line L12 is the applied voltage of -0.8V, and line L13 is the applied voltage of -0.9V. As shown in FIG. 5, in line L13, the current does not approach zero even after a sufficient amount of time has passed since the oxygen scavenger was applied. This is the effect of the residual power associated with the reduction of protons. On the other hand, in the lines L11 and L12, the influence of the residual power is so small that it can be ignored.

From the above, the optimum voltage applied between the cathode 3 and the anode 6 is -0.8V.

[Response to Voltage Applied to Oxygen Electrode]
Next, the response of the oxygen electrode 1 to the applied voltage will be described. A voltage of −0.8 V was applied between the cathode 3 and the anode 6 in the case where the sheet member 10 contained a moisturizing agent and in the case where the sheet member 10 did not contain a moisturizing agent, and changes in the current over time were measured. .

FIG. 6 is a diagram showing changes in current over time with and without a moisturizing agent. The vertical axis in FIG. 6 represents current, and the horizontal axis represents time. The line L21 is the measurement result when the sheet member 10 contains sorbitol as a moisturizing agent, and the line L22 is the measurement result when the sheet member 10 does not contain the moisturizing agent. As shown in FIG. 6, line L21 provided a stable response over a long period of time to the applied voltage. On the other hand, in line L22, the moisture in the electrolyte evaporates over time, rendering the electrolyte inactive, and the response to the applied voltage is unstable.

As described above, according to the embodiment, by impregnating the sheet member 10 with a moisturizing agent, it is possible to realize the oxygen electrode 1 in which the response to the applied voltage is stable over a long period of time.

Further, according to the embodiment, since the sheet member 10 is impregnated with the electrolyte, the electrolyte layer can be uniformly formed. As a result, the proportion of oxygen electrodes 1 that not only have a stable response during measurement but also stably operate can be manufactured, and assembly during manufacture is easy. On the other hand, when a liquid or paste electrolyte is placed on the cathode 3 and the anode 6, the thickness of the electrolyte becomes uneven because the electrolyte under the oxygen permeable membrane 11 is in a soft state at the time of measurement. and the response is unstable.

(Modification)
FIG. 7 is a cross-sectional view of an oxygen electrode according to a modification. As shown in FIG. 7, the oxygen electrode 1A has a thickness substantially the same as that of the sheet member 10, and includes a spacer 12A arranged to surround the edge of the sheet member 10. As shown in FIG. The spacer 12A is made of resin such as polyimide, but the material is not particularly limited. In this case, since the oxygen-permeable film 11 does not have a stepped portion, it is possible to prevent the oxygen-permeable film 11 from being cut or the like during the manufacturing process, thereby preventing the operation from becoming unstable.

〔measuring device〕
A measuring device comprising the oxygen electrode 1 may be produced. Specifically, a measuring device capable of measuring the concentration of dissolved oxygen in a sample can be realized by placing a sample injection part formed with a chamber into which a sample can be injected on the oxygen permeable film 11 .

Moreover, a measuring device in which a plurality of sets of the cathode 3 and the anode 6 described above are formed may be manufactured. By providing multiple sets of cathodes 3 and anodes 6, multiple samples can be measured simultaneously.

Reference Signs List 1, 1A Oxygen electrode 2 Substrate 3 Cathode 4, 7 Wiring 5, 8 Electrode pad 6 Anode 9 Insulating layer 10 Sheet member 11 Oxygen permeable film 12A Spacer

Claims (4)

a cathode formed on a substrate;
an anode formed on the substrate;
resting on at least a portion of the cathode and the anode and impregnated with an electrolyte consisting of potassium chloride (KCl), a buffer component consisting of Tris-HCl, a humectant, and polyvinylpyrrolidone; a sheet member made of paper;
a spacer having substantially the same thickness as the sheet member and arranged to surround the edge of the sheet member;
an oxygen permeable film covering the sheet member and the spacer ;
An oxygen electrode, comprising: 2. The oxygen electrode according to claim 1 , wherein the humectant contains at least one of sucrose, glucose, or sorbitol. the oxygen electrode according to claim 1 or 2 ;
a sample injection part placed on the oxygen permeable membrane and capable of injecting a sample;
A measuring device comprising: 4. The measuring device according to claim 3 , wherein a plurality of sets of said cathode and said anode are formed.

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