Carbon dioxide partial pressure sensor and application thereof

Abstract

The invention provides a carbon dioxide partial pressure sensor and application thereof, and relates to the technical field of electrochemistry. The carbon dioxide partial pressure sensor is mainly composed of an electrode substrate, and an electrolyte layer and a breathable film layer which are sequentially loaded on the electrode substrate. Wherein a redox medium in the electrolyte layer is p-benzoquinone. The p-benzoquinone is used as a redox medium in the electrolyte layer, so that the pH change caused by the change of the concentration of carbon dioxide in a solution sample can be directly detected, and the partial pressure of carbon dioxide in the solution can be directly, quickly and accurately detected; meanwhile, on the basis that p-benzoquinone is selected as an oxidation-reduction medium, the carbon dioxide partial pressure sensor can be designed into a single electrode, and the problems that an existing carbon dioxide partial pressure sensor is usually provided with multiple electrodes, and consequently the structure is complex, the response speed is low, and the stability is poor are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a carbon dioxide partial pressure sensor and applications thereof. Background Art

[0002] Accurately measuring carbon dioxide (CO2) concentrations is crucial in environmental monitoring, medical equipment, industrial process control, and other fields. Existing CO2 sensors primarily utilize electrochemical, optical, or semiconductor principles. Electrochemical sensors are widely used due to their low cost, fast response, and ease of integration.

[0003] However, existing electrochemical CO2 sensors still have the following technical problems: 1. Complex structure: Traditional sensors usually require multiple electrodes (such as working electrode, reference electrode and counter electrode) and a complex electrolyte system, resulting in high manufacturing costs and difficulty in miniaturization.

[0004] 2. Slow response speed: Due to the low solubility of CO2 in water, the response time of traditional sensors is long, which makes it difficult to meet the needs of real-time monitoring.

[0005] 3. Poor stability: The electrolyte and electrode materials in the sensor are easily affected by environmental factors (such as temperature and humidity), causing the measurement results to drift or fail.

[0006] 4. High cost: Some sensors use expensive materials (such as ceramic substrates or precious metal electrodes), which limits their large-scale application.

[0007] Therefore, in order to solve the above problems, it is urgent to develop a CO2 sensor with simple structure, fast response speed, high stability and low cost.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The first purpose of the present invention is to provide a carbon dioxide partial pressure sensor. The carbon dioxide partial pressure sensor can directly detect the carbon dioxide partial pressure in the solution through a single-electrode design, effectively alleviating the problems of existing carbon dioxide partial pressure sensors, which are usually multi-electrode and require the measurement of parameters such as pH, resulting in complex structure, slow response speed and poor stability.

[0010] A second object of the present invention is to provide an application of a carbon dioxide partial pressure sensor.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: The present invention provides a carbon dioxide partial pressure sensor, which includes an electrode substrate and an electrolyte layer and a gas permeable membrane layer sequentially supported on the electrode substrate; Wherein: the redox medium in the electrolyte layer is p-benzoquinone.

[0012] Furthermore, the raw materials for preparing the electrolyte layer include: p-Benzoquinone, anhydrous ethanol, calcium chloride, sodium bicarbonate and purified water.

[0013] Furthermore, the raw materials for preparing the electrolyte layer include, by mass percentage: p-Benzoquinone 0.1-0.6%, anhydrous ethanol 5-15%, calcium chloride 2-3%, sodium bicarbonate 2-3%, and the balance is purified water; Preferably, the raw materials for preparing the electrolyte layer include, by mass percentage, 0.3% p-benzoquinone, 10% anhydrous ethanol, 2.5% calcium chloride, 2.2% sodium bicarbonate and 85% purified water.

[0014] Furthermore, the breathable membrane layer is mainly made of polydimethoxysiloxane and cyclohexane.

[0015] Furthermore, the mass ratio of polydimethoxysiloxane to cyclohexane in the breathable membrane layer is 1:3.5-4.5, preferably 1:4.

[0016] Furthermore, the electrode base is made of a PET substrate by sputtering gold.

[0017] The present invention provides an application of the carbon dioxide partial pressure sensor in measuring the carbon dioxide partial pressure in a solution.

[0018] Furthermore, the application is: placing a carbon dioxide partial pressure sensor in a solution to be tested, and directly calculating the carbon dioxide partial pressure in the solution to be tested from the potential signal measured by the sensor.

[0019] Furthermore, the carbon dioxide partial pressure sensor has a linear response within the CO2 partial pressure range of 20-120 mmHg, and the response time is less than 10 seconds.

[0020] The present invention provides an environmental monitoring device, a medical detection device or an industrial process control device comprising the above-mentioned carbon dioxide partial pressure sensor.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The carbon dioxide partial pressure sensor provided by the present invention is mainly composed of an electrode substrate and an electrolyte layer and a breathable membrane layer sequentially loaded on the electrode substrate; wherein: the redox medium in the electrolyte layer is p-benzoquinone. The electrolyte layer of the present application uses p-benzoquinone as a redox medium, which can directly detect the pH change caused by the change of CO2 concentration in the solution sample, and thus can directly, quickly and accurately detect the carbon dioxide partial pressure in the solution; at the same time, based on the selection of p-benzoquinone as the redox medium, the carbon dioxide partial pressure sensor of the present application can be designed with a single electrode, which also effectively alleviates the problems of the existing carbon dioxide partial pressure sensor usually having multiple electrodes, resulting in complex structure, slow response speed and poor stability.

[0022] The carbon dioxide partial pressure sensor provided in this application can be widely used in the measurement of carbon dioxide partial pressure in solutions, and has broad market prospects in the fields of environmental monitoring, medical equipment, industrial process control, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on the drawings in the following description without any creative work.

[0024] Figure 1 This is a linear relationship diagram between the potential signal measured by the carbon dioxide partial pressure sensor of Example 3 provided by the present invention and the partial pressure of dissolved carbon dioxide in the sample (P(CO2)). DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] According to one aspect of the present invention, a carbon dioxide partial pressure sensor comprises an electrode substrate and an electrolyte layer and a gas permeable membrane layer sequentially supported on the electrode substrate; Wherein: the redox medium in the electrolyte layer is p-benzoquinone.

[0027] The carbon dioxide partial pressure sensor provided by the present invention is mainly composed of an electrode substrate and an electrolyte layer and a breathable membrane layer sequentially loaded on the electrode substrate; wherein: the redox medium in the electrolyte layer is p-benzoquinone. The electrolyte layer of the present application uses p-benzoquinone as a redox medium, which can directly detect the pH change caused by the change of CO2 concentration in the solution sample, and thus can directly, quickly and accurately detect the carbon dioxide partial pressure in the solution; at the same time, based on the selection of p-benzoquinone as the redox medium, the carbon dioxide partial pressure sensor of the present application can be designed with a single electrode, which also effectively alleviates the problems of the existing carbon dioxide partial pressure sensor usually having multiple electrodes, resulting in complex structure, slow response speed and poor stability.

[0028] Specifically, the principle of the sensor of the present invention is: The dissolved CO2 in the sample passes through the membrane layer and enters the inner electrolyte layer to dissolve: CO2 + H2O = H2CO3 H2CO3= H + + HCO3 - There is enough NaHCO3 in the inner electrolyte layer, so [HCO3 - ] can be regarded as a constant. According to the pH definition formula, P(CO2) and the pH value in the inner electrolyte layer are logarithmically related.

[0029] The quinone and hydroquinone added to the inner electrolyte layer satisfy the following reaction balance: Q + 2H + + 2e = H2Q The concentrations of quinone and hydroquinone are roughly equal and the content is low, which can be converted into a proportional relationship between membrane potential E and lgPCO2.

[0030] Traditional sensors require two electrochemical sensors. The CO2 sensor includes an independent pH sensor, which detects the dissolved CO2 content, or pCO2, by detecting pH changes. The structure of the traditional sensor can be found in US6805781B2.

[0031] In a preferred embodiment of the present invention, the raw materials for preparing the electrolyte layer include: p-benzoquinone, anhydrous ethanol, calcium chloride, sodium bicarbonate and purified water.

[0032] It should be noted that the role of anhydrous ethanol in the raw materials for preparing the electrolyte layer of the present application is to assist in dissolving quinone hydroquinone, and on the other hand, to change the polarity of the solution, which can better control the consistency of solution dispensing; the role of calcium chloride in the raw materials for preparing the electrolyte layer of the present application is that after the calcium chloride is dried, the sample enters the sensor, which can promote the rapid wetting of the sensor; the excess sodium bicarbonate in the raw materials for preparing the electrolyte layer of the present application is mainly used to balance the decomposition of CO2, and is used as a constant in the CO2 dissolution calculation.

[0033] As a preferred embodiment, the electrolyte layer of the present application is made by mixing materials such as p-benzoquinone, anhydrous ethanol, purified water, calcium chloride, sodium bicarbonate in a specific proportion, which can react with CO2 to generate a measurable electrochemical signal.

[0034] In the above preferred embodiment, the raw materials for preparing the electrolyte layer include, by mass percentage: 0.1-0.6% p-benzoquinone, 5-15% anhydrous ethanol, 2-3% calcium chloride, 2-3% sodium bicarbonate, and the balance is purified water; The proportion of p-benzoquinone may be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%, or any proportion between 0.1% and 0.6%. The proportion of anhydrous ethanol may be, but is not limited to, 5%, 8%, 10%, 12%, 14%, or 15%, or any proportion between 5% and 15%. The proportion of calcium chloride may be, but is not limited to, 2%, 2.3%, 2.5%, 2.8%, or 3%, or any proportion between 2% and 3%. The proportion of sodium bicarbonate may be, but is not limited to, 2%, 2.3%, 2.5%, 2.8%, or 3%, or any proportion between 2% and 3%.

[0035] The present invention uses purified water represented by "remainder" as a necessary component to overcome the problem that the percentage range of each component in the raw material for preparing the electrolyte layer is less than 100%.

[0036] Preferably, the raw materials for preparing the electrolyte layer include, by mass percentage, 0.3% p-benzoquinone, 10% anhydrous ethanol, 2.5% calcium chloride, 2.2% sodium bicarbonate and 85% purified water.

[0037] In a preferred embodiment of the present invention, the breathable membrane layer is mainly made of polydimethoxysiloxane and cyclohexane.

[0038] As a preferred embodiment, the breathable membrane layer of the present application is made of polydimethoxysiloxane (PDMS) and cyclohexane, which has good air permeability and chemical inertness, can effectively isolate interfering substances in the external environment, and at the same time allow CO2 molecules to pass through.

[0039] Furthermore, the mass ratio of polydimethoxysiloxane to cyclohexane in the breathable membrane layer is 1:3.5-4.5, preferably 1:4.

[0040] In a preferred embodiment of the present invention, the electrode substrate is made by sputtering gold on a PET substrate.

[0041] As a preferred embodiment, the electrode substrate is made by sputtering gold on a PET substrate, which avoids the insulating oil contamination problem on a traditional PCB substrate and has good electrical conductivity and chemical stability.

[0042] According to one aspect of the present invention, the carbon dioxide partial pressure sensor is used to measure the carbon dioxide partial pressure in a solution.

[0043] The carbon dioxide partial pressure sensor provided in this application can be widely used in measuring the carbon dioxide partial pressure in a solution.

[0044] In a preferred embodiment of the present invention, the application is: placing a carbon dioxide partial pressure sensor in a solution to be tested, and directly calculating the carbon dioxide partial pressure in the solution to be tested from the potential signal measured by the sensor.

[0045] In a preferred embodiment of the present invention, the carbon dioxide partial pressure sensor has a linear response within the CO2 partial pressure range of 20-120 mmHg, and the response time is less than 10 seconds.

[0046] In summary, the advantages of the carbon dioxide partial pressure sensor of the present application over the prior art can be summarized as follows: 1. Simplified structure: Only one electrolyte layer and PDMS membrane layer are needed to measure the CO2 partial pressure. No additional pH electrode is required for joint testing, which simplifies the sensor structure and reduces manufacturing costs.

[0047] 2. High sensitivity: Using p-benzoquinone as the redox medium significantly improves the sensitivity and response speed of the sensor.

[0048] 3. Good stability: The electrode base adopts the PET substrate sputtering gold process, which avoids the insulating oil pollution problem on the traditional PCB substrate. At the same time, the PDMS film layer has good chemical inertness and can remain stable in complex environments.

[0049] 4. Low cost: PET substrate and PDMS materials are low in cost, and the preparation process is simple, suitable for large-scale production.

[0050] 5. Wide range of application scenarios: This sensor can be widely used in environmental monitoring, medical equipment, industrial process control and other fields, and has broad market prospects.

[0051] According to one aspect of the present invention, an environmental monitoring device, a medical detection device or an industrial process control device includes the above-mentioned carbon dioxide partial pressure sensor.

[0052] The carbon dioxide partial pressure sensor provided in this application can be widely used in environmental monitoring equipment, medical testing equipment or industrial process control equipment.

[0053] The technical solution of the present invention will be further described below with reference to embodiments.

[0054] Examples 1-3 A carbon dioxide partial pressure sensor comprises an electrode substrate, and an electrolyte layer and a breathable membrane layer sequentially loaded on the electrode substrate.

[0055] The preparation method of the carbon dioxide partial pressure sensor is as follows: (1) Providing an electrode substrate, wherein the electrode substrate is made by a PET substrate sputtering gold process, that is, a gold layer is deposited on the PET substrate by a sputtering process to form a conductive substrate, and the thickness of the gold layer is 20 nm; (2) Preparation of electrolyte layer: benzoquinone, anhydrous ethanol, purified water, calcium chloride and sodium bicarbonate are mixed in proportion to form an electrolyte layer slurry, stirred evenly and then coated on the electrode substrate in step (1) to form an electrolyte layer.

[0056] The composition of the electrolyte layer slurry is as follows:

[0057] (3) Preparation of PDMS membrane layer: Mix polydimethoxysiloxane (PDMS) with cyclohexane and coat it on the electrolyte layer to form a breathable membrane layer.

[0058] The mass ratio of polydimethoxysiloxane to cyclohexane in the breathable membrane layer is 1:4.

[0059] Example 4 This embodiment is the same as Example 3 except that the composition and content of the electrolyte layer slurry are different from those of Example 3.

[0060] The composition of the electrolyte layer slurry in this embodiment is as follows: 1% p-benzoquinone, 10% anhydrous ethanol, 2.5% calcium chloride, 2.2% sodium bicarbonate and 84.3% purified water.

[0061] Comparative Example 1 This comparative example is the same as Example 3 except that p-benzoquinone in the electrolyte layer slurry is replaced by an equal amount of polyaniline.

[0062] It should be noted that, in this comparative example, the polyaniline electron mediator is detected by measuring the electrical conductivity, while in the embodiment, the CO2 sensor is detected by measuring the potential of the benzoquinone.

[0063] The reaction principle of this comparative example is the resistance method: the conductivity of polyaniline depends on its protonation state (the following reaction): PANI (insulating state) + H+ ⇌ PANI+ (conductive state) PANI (insulating state) + H+ ⇌ PANI+ (conductive state); CO2 dissolves to generate H⁺, which increases the degree of protonation and significantly increases the conductivity (decreases the resistance).

[0064] Test Example 1 Performance Characterization of Carbon Dioxide Partial Pressure Sensor The carbon dioxide partial pressure sensors and reference electrodes from Examples 1-3 were placed in samples containing a certain concentration of dissolved CO₂ (aqueous solutions, serum, and real human blood samples). The potential values were then calculated. The linear correlation between the potential signal measured by the sensor and the partial pressure of dissolved carbon dioxide (P(CO₂)) in the sample was used to calculate the P(CO₂) in the sample. The accuracy deviation was then calculated compared to the theoretical value (from Libang Instruments). Each sample was tested multiple times, and the precision (CV%) was calculated from the standard deviation and the mean.

[0065] Wherein, the method for measuring the potential value includes: (1) Preparation steps of reference sensor: silver paste, electrolyte layer and selective membrane layer are applied to the gold surface of the cleaned PET sputtered gold reference electrode, wherein: The main components of the silver paste layer are Ag, AgCl, a binder, and acetone. This is a mature silver paste compound purchased from Shenzhen Yilai Technology Co., Ltd., model Elec-H230. The silver paste layer was dispensed at 800µm and 30µm thick.

[0066] b. The main components of the electrolyte layer are NaCl, KCl, and H2O. The ratio is 1%:2%:97%. The electrolyte layer is dispensed at 1000um and 20um thick.

[0067] c. The main components of the selective membrane layer are PDMS and cyclohexane, with a composition ratio of 1:4.5~1:3.5, preferably 1:4, with a dispensing thickness of 1300um and a thickness of 20nm.

[0068] (2) Preparation steps of CO2 working sensor: Electrolyte layer and selective membrane layer solution are dispensed on the cleaned PET sputtered gold working electrode surface, wherein: a. Electrolyte layer dispensing 800um, 30um thickness; b. Selective film dispensing 1300um, 20um thickness.

[0069] (3) Sample preparation: 40% O2-3% CO2, 21% O2-6% CO2, and 3% O2-17% CO2 were introduced into three venous whole blood samples from the same person, and the target dissolved CO2 values obtained were 20.5, 41.3, and 115.6 mmHg, respectively.

[0070] (4) The three samples with different CO2 dissolved concentrations are introduced into the sensor in sequence. After the samples reach the top of the sensor, a stable potential can be obtained in 8 to 10 seconds. After measuring the three corresponding potential values, the sensitivity and linearity of the CO2 sensor are obtained.

[0071] The precision and accuracy deviations of the whole blood samples with different gradients in Examples 1 to 3 are shown in Tables 1 to 3 below.

[0072] Table 1 Detection data of carbon dioxide partial pressure sensor for whole blood samples with different gradients in Example 1:

[0073] Table 2 Detection data of carbon dioxide partial pressure sensor for whole blood samples with different gradients in Example 2:

[0074] Table 3 Detection data of carbon dioxide partial pressure sensor for whole blood samples with different gradients in Example 3:

[0075] Figure 1 This is a linear relationship diagram between the potential signal measured by the carbon dioxide partial pressure sensor in Example 3 and the partial pressure of dissolved carbon dioxide in the sample (P(CO2)).

[0076] Depend on Figure 1 It can be seen that the carbon dioxide partial pressure sensor prepared in this application has a good linear relationship with the dissolved CO2 in the sample. Its linear response formula is y=43.65x-6.3143, and R2=0.9991.

[0077] Table 4 Detection data of carbon dioxide partial pressure sensor for whole blood samples with different gradients in Example 4:

[0078] In Example 4, due to the excessively high content of p-benzoquinone in the electrolyte layer slurry, the linear range of the sensor is relatively narrow, the accuracy deviation of the high and low values of the CO2 partial pressure is large, and the precision is not very good.

[0079] Table 5 Comparative Example 1 Detection data of carbon dioxide partial pressure sensor for whole blood samples with different gradients:

[0080] Since comparative example 1 uses polyaniline as the redox medium, compared with the implementation method of using para-benzoquinone in Examples 1 to 3 of the present application, polyaniline as the electron mediator of the CO2 partial pressure sensor has a certain gradient for samples with different gradient CO2 partial pressures, but the test accuracy and precision are worse than those of the examples.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carbon dioxide partial pressure sensor, characterized in that: The carbon dioxide partial pressure sensor comprises an electrode substrate and an electrolyte layer and a gas permeable membrane layer sequentially supported on the electrode substrate; Wherein: the redox medium in the electrolyte layer is p-benzoquinone.

2. The carbon dioxide partial pressure sensor according to claim 1, characterized in that The raw materials for preparing the electrolyte layer include: p-Benzoquinone, anhydrous ethanol, calcium chloride, sodium bicarbonate and purified water.

3. The carbon dioxide partial pressure sensor according to claim 2, characterized in that The raw materials for preparing the electrolyte layer include, by mass percentage: p-Benzoquinone 0.1-0.6%, anhydrous ethanol 5-15%, calcium chloride 2-3%, sodium bicarbonate 2-3%, and the balance is purified water; Preferably, the raw materials for preparing the electrolyte layer include, by mass percentage, 0.3% p-benzoquinone, 10% anhydrous ethanol, 2.5% calcium chloride, 2.2% sodium bicarbonate and 85% purified water.

4. The carbon dioxide partial pressure sensor according to claim 1, characterized in that The breathable membrane layer is mainly made of polydimethoxysiloxane and cyclohexane.

5. The carbon dioxide partial pressure sensor according to claim 4, characterized in that The mass ratio of polydimethoxysiloxane to cyclohexane in the breathable membrane layer is 1:3.5-4.5, preferably 1:

4.

6. The carbon dioxide partial pressure sensor according to claim 1, characterized in that The electrode base is made by sputtering gold on a PET substrate.

7. Use of the carbon dioxide partial pressure sensor according to any one of claims 1 to 6 in measuring the carbon dioxide partial pressure in a solution.

8. The use according to claim 7, characterized in that The applications are: The carbon dioxide partial pressure sensor is placed in the solution to be tested, and the partial pressure of carbon dioxide in the solution to be tested is directly calculated from the potential signal measured by the sensor.

9. The use according to claim 8, characterized in that The carbon dioxide partial pressure sensor has a linear response within the CO2 partial pressure range of 20-120 mmHg, and a response time of less than 10 seconds.

10. An environmental monitoring device, a medical detection device or an industrial process control device comprising the carbon dioxide partial pressure sensor according to any one of claims 1 to 6.

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