All-solid-state hydrogen ion selective electrode and preparation method and application thereof

Abstract

The invention discloses an all-solid-state hydrogen ion selective electrode as well as a preparation method and application thereof. The all-solid-state hydrogen ion selective electrode comprises a graphene conducting layer, a solid-state contact layer and a hydrogen ion sensitive film which are sequentially coated at the tip end of a micro needle, and the solid contact layer is a poly (3, 4-ethylenedioxythiophene) / poly (sodium 4-styrenesulfonate) layer. The all-solid-state ion selective electrode is prepared by modifying a multi-layer structure on the surface of a microelectrode. According to specific ions to be detected, the modification layer on the surface of the microelectrode can be selectively adjusted, so that the detection accuracy and stability of the sensor are improved, and rapid detection of the ions is realized. The invention provides a brand new thought for the design and application of the multi-parameter portable integrated sensor.

Description

Technical Field

[0001] The invention relates to an all-solid-state hydrogen ion selective electrode and a preparation method and application thereof, belonging to the field of electrochemical sensors. Background Art

[0002] Ion-selective electrodes are a type of indicator electrode that can show selectivity for specific ions. They are widely used in electrochemical sensors in many fields by converting the activity changes of the ions to be measured into electrical signals. In pH detection, glass electrodes are a common application. They are composed of an internal reference electrode, an internal reference solution, and a sensitive membrane, and have been widely used in commercial electrodes. However, traditional glass electrodes are liquid-junction ion-selective electrodes, which have disadvantages such as high internal resistance, difficulty in miniaturization, the need for internal solutions, and short service life, which limit their scope of application.

[0003] All-solid-state ion selective electrodes have developed rapidly in recent years and have been widely used in the fields of biomedicine, agriculture, environment and industrial analysis, due to their advantages of portability, fast response, low cost, easy miniaturization, simple production, and ability to achieve in vivo measurement. At present, there are few studies on all-solid-state microneedle hydrogen ion selective sensors, so the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide an all-solid-state hydrogen ion selective electrode, which realizes the miniaturization of the hydrogen ion selective electrode, makes it easy to carry, has a long service life, is low in cost, is easy to operate, simplifies the manufacturing process, is suitable for mass production, and overcomes the shortcomings of traditional hydrogen ion glass electrodes such as large size and short life.

[0005] The all-solid-state hydrogen ion selective electrode provided by the present invention comprises a graphene conductive layer, a solid contact layer and a hydrogen ion sensitive membrane sequentially coated on the tip of a microneedle; The solid contact layer is a poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrenesulfonate) layer.

[0006] Preferably, the microneedle is sleeved outside a polyimide tube, and the tip of the microneedle extends 1-2 mm outside the polyimide tube; The polyimide tube has a diameter of 0.2-0.3 mm and a thickness of 0.02-0.04 mm; The tube opening of the polyimide tube close to the tip of the microneedle is sealed by an oily original glue; The assembly process of the micro needle and the polyimide tube is as follows: The microneedle is cleaned in anhydrous ethanol using an ultrasonic cleaner; then the polyimide tube is sleeved on the tip of the microneedle so that the tip is exposed about 1-2 mm from the polyimide tube; the tube opening of the polyimide tube close to the tip of the microneedle is sealed by an oily original rubber; Preferably, the hydrogen ion sensitive membrane is made of an ion exchanger, a hydrogen ion carrier, a plasticizer and a polymer matrix material; The ion exchanger includes one or a combination of potassium tetraphenylborate, sodium tetraphenylborate, potassium tetrachlorophenylborate, and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate; The hydrogen ion carrier includes tridodecylamine, diphenylamine, triphenylamine and other various compounds (aliphatic, heteroaromatic hydrocarbons and their derivatives); The plasticizer includes one or a combination of bis(2-ethylhexyl) sebacate, o-nitrophenyl octyl ether, di-n-pentyl phthalate, dioctyl phthalate and dioctyl sebacate; The polymer matrix material includes one or a combination of polyvinyl chloride, polyurethane, polyvinyl acetate and polymethyl methacrylate.

[0007] Preferably, the mass ratio of the ion exchanger, the hydrogen ion carrier, the plasticizer and the polymer matrix material is 1:2.8-3.0:185-190:90-95.

[0008] The present invention further provides a method for preparing the all-solid-state hydrogen ion selective electrode, comprising the following steps: S1, applying a graphene water-based coating on the tip of the microneedle to obtain the graphene conductive layer; S2, using a three-electrode system, electroplating (3,4-ethylenedioxythiophene) / poly(sodium 4-styrene sulfonate) on the surface of the graphene conductive layer to obtain the poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrene sulfonate) layer; S3, using an artificial dip coating method to coat the tip of the microneedle with a hydrogen ion sensitive membrane solution to obtain the all-solid-state hydrogen ion selective microelectrode; The hydrogen ion sensitive membrane solution is prepared from the ion exchanger, the hydrogen ion carrier, the plasticizer and the polymer matrix material; S4, activating the microneedle in a hydrochloric acid solution with a concentration of 0.1 mol / L.

[0009] In step S2, the molar ratio of the 3,4-ethylenedioxythiophene to the poly(sodium 4-styrene sulfonate) is 1:10; The electroplating conditions are as follows: electroplating at a rate of 0.08-0.12 V / s using cyclic voltammetry, 8-16 cycles of scanning, and a voltage range of -0.2-1.5 V; After the electroplating is completed, the mixture is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

[0010] In step S3, the hydrogen ion sensitive membrane solution is prepared from tetrahydrofuran or cyclohexanone; After the hydrogen ion sensitive membrane is dip-coated, it is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

[0011] When the all-solid-state hydrogen ion selective electrode of the present invention is used for hydrogen ion concentration detection, the following steps are included: The all-solid-state hydrogen ion selective electrode is used to detect the voltage of the ion to be measured in the solution to be measured; the voltage of the ion to be measured is converted into the concentration of the ion to be measured by the Nernst equation.

[0012] The present invention prepares a fully solid-state ion selective electrode by modifying a multilayer structure on the surface of a microelectrode. According to the specific ions to be detected, the modified layer on the surface of the microelectrode can be selectively adjusted, thereby improving the detection accuracy and stability of the sensor and realizing rapid detection of ions. The present invention provides a new idea for the design and application of multi-parameter portable integrated sensors.

[0013] The micro all-solid-state hydrogen ion selective electrode provided by the present invention is combined with a reference electrode to form a hydrogen ion sensor, and is connected to an external measuring device to form an electrochemical cell. Since the electrode potential of the reference electrode is usually fixed and the ion concentration in the internal reference solution is known, the ion concentration in the solution to be tested can be calculated by measuring the electromotive force of the cell. The electrode of the present invention can be combined with an external reference electrode to achieve rapid and accurate hydrogen ion concentration detection.

[0014] The electrode of the present invention has the advantages of small size, high portability, simple operation, high sensitivity, good selectivity, rapid response, low production cost, etc., and is suitable for real-time and long-term monitoring of the hydrogen ion content in the solution to be tested. In addition, the electrode of the present invention does not require pretreatment before use, and can quickly detect the hydrogen ion content in the solution within a few seconds, thereby realizing a fast and convenient measurement of hydrogen ions in the solution to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of the preparation of the all-solid-state ion selective electrode for detecting hydrogen ions according to the present invention.

[0016] Figure 2 It is the response calibration curve of the all-solid-state hydrogen ion selective electrode of the present invention at different hydrogen ion concentrations. DETAILED DESCRIPTION

[0017] To more clearly illustrate the purpose, technical solution and advantages of the present invention, the technical solution of the present invention is now described in detail and completely. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0018] Combine the following Figure 1 The preparation method of the all-solid-state hydrogen ion selective electrode of the present invention is described as follows: (1) The tip diameter of the stainless steel microneedle electrode should be less than 10 µm. First, polish the electrode surface with 120-grit fine sandpaper, and then ultrasonically clean the electrode tip with 50% alcohol.

[0019] (2) After the electrode surface is dry, the microneedle is inserted into a polyimide tube with an inner diameter of 0.2 mm, a wall thickness of 0.02 mm, and a length of 0.2 cm, so that the stainless steel microneedle is exposed about 0.5 mm from the tip of the polyimide tube. Then, quick-drying glue is used to adhere the end of the polyimide tube to the stainless steel microneedle to ensure the stability and sealing of the structure.

[0020] (3) After the glue is cured, the graphene composite water-based conductive coating is evenly coated on the surface of the stainless steel microneedle electrode. Then, the coated electrode is placed in a constant temperature drying oven for 6 hours to ensure that the graphene is fully cured and firmly attached to the electrode surface.

[0021] (4) The specific steps of electroplating the conductive polymer PEDOT are as follows: First, the conductive polymer PEDOT is deposited on the graphene surface for modification by electrochemical polymerization technology. The electropolymerization process is carried out in a three-electrode system, in which a platinum sheet electrode is used as a counter electrode, an Ag / AgCl microelectrode is used as a reference electrode, and a stainless steel microneedle electrode is used as a working electrode. Before electroplating, nitrogen gas is introduced for 10 minutes to remove air from the electrolyte to ensure the accuracy of the electroplating process. Then, the electrode is scanned at a rate of 0.1 V / s in the voltage range of -0.2 V to 1.5 V using cyclic voltammetry. The thickness of the PEDOT film on the electrode surface is adjusted by controlling the number of polymerization cycles; as the number of polymerization cycles increases, the electrode current and capacitance will also increase accordingly. In this embodiment, the number of polymerization cycles is set to 10 cycles to ensure that a uniform and appropriate poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrenesulfonate) layer is formed on the electrode. After the polymerization is completed, the surface of the conductive polymer layer is carefully washed with deionized water to remove any impurities and residues. Subsequently, the electrode coated with the conductive polymer layer was placed with one end facing up in a drying oven for 12 hours to solidify the PEDOT film and ensure its stable attachment to the electrode surface.

[0022] (5) H + Selective membrane master solution formula: H + The selective membrane mother solution is prepared by dissolving ion exchanger, hydrogen ion carrier, plasticizer and polymer matrix material in anhydrous tetrahydrofuran solution (solvent). + The information of the reagent components and proportions of the selective membrane mother solution is shown in Table 1.

[0023] The amount of solvent anhydrous tetrahydrofuran (THF) used is 1mL, and the manufacturer is the Zhongnong Experimental Reagent Consumables Purchasing Platform. Weigh 3.04878mg (1 wt.%) of tri-n-dodecylamine, 1.075 mg (0.4 wt.%) of potassium tetraphenylborate, 100.7543 mg (33.0 wt.%) of polyvinyl chloride, and 200mg (65.6 wt.%) of bis(2-ethylhexyl) sebacate on the balance. Then pour the above four reagents into a small beaker respectively. Since the hydrogen ion carrier reagent to be weighed is a liquid, the small beaker needs to be placed in the balance, and the balance needs to be peeled and cleared after it stabilizes. Next, use a pipette to draw 1 µL of hydrogen ion carrier into the small beaker, repeat three times, for a total of about 3 mg. Since the amount of reagent is small, the weighing paper can be placed in the balance and peeled, and then a small amount of reagent can be taken with a micro sampler and gently poured onto the weighing paper. Next, the plasticizer DOS needs to be weighed. Since DOS is also a liquid, it is directly added to the small beaker. Place the small beaker in the balance, wait for it to stabilize, then remove the tares and zero again, and then use a pipette to draw 200µL of DOS into the small beaker. Use a pipette to add 1 mL of THF to the small beaker, and then put in a small magnetic rotor. Wrap the mouth of the small beaker with a piece of aluminum foil with a thickness of 0.15 μm to prevent the volatile carcinogen THF from volatilizing. Then, place the wrapped small beaker on the magnetic stirrer and stir at room temperature for 30 minutes. When stirring, make sure that the speed of the magnetic rotor is moderate. Too fast may cause the small beaker to tip over, and too slow may affect the dissolution rate of the reagent. The whole process needs to be carried out in a fume hood. Open the fume hood when stirring starts and close it after stirring. After stirring is over, the H+ carrier and other reagents are fully mixed, and the solution is turbid. Take out the magnetic rotor with the stirring bar recovery bar, and then wrap the small beaker as a whole with aluminum foil. Finally, place the small beaker in a refrigerator at 4°C for at least 6 hours until the turbid liquid becomes clear and transparent, ensuring that the ion-selective membrane mother liquor is further fully mixed.

[0024] (6) Solid H + The ion-selective electrode is prepared by manual dip coating technology, in which the thickness of the polymer film is precisely controlled by adjusting the withdrawal speed of the substrate after immersion in the polymer solution. After the coating operation is completed, the electrode is placed in a constant temperature box at 30°C for 6 hours of drying to ensure that the polymer film is fully cured, thereby improving the overall performance and stability of the electrode.

[0025] (7) After the electrode is dried, immerse it in a 0.1 mol / L hydrochloric acid solution for activation for 50 hours. During this process, it is necessary to ensure that only the tip membrane of the electrode is immersed in the solution. If the tip of the electrode is immersed too deeply, water may enter the interior of the electrode and affect its performance; conversely, if the tip of the electrode is not completely immersed, the electrode may not work properly. In addition, given the volatility of hydrochloric acid and the long activation time, it is necessary to regularly check whether the tip of the electrode is always completely immersed in the solution to ensure the smooth progress of the activation process and the performance of the electrode. During the entire activation process, a high degree of attention and precision of operation should be maintained.

[0026] (8) All-solid-state H + Calibration of ion selective electrodes First, the hydrogen ion activity in the solution to be tested is accurately measured using a hydrogen ion selective electrode to obtain the voltage value of the hydrogen ions. Subsequently, the measured hydrogen ion voltage value is converted into the corresponding hydrogen ion concentration based on the Nernst linear equation. This conversion process ensures the accuracy and reliability of the electrode readings, providing a solid foundation for subsequent analysis.

[0027] Test results such as Figure 2 As shown, it can be seen that H + The Nernst slope of the sensor can reach 56.24 mV / decade, and the detection limit is about 1.0×10 -11 M, linear range is 10 -11 -10 -3 M.

[0028] Table 1 H + Selective membrane components

Claims

1. An all-solid-state hydrogen ion selective electrode, comprising a graphene conductive layer, a solid contact layer and a hydrogen ion sensitive membrane sequentially coated on the tip of a microneedle; The solid contact layer is a poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrene sulfonate) layer.

2. The all-solid-state hydrogen ion selective electrode according to claim 1, characterized in that: The microneedle sleeve is disposed outside a polyimide tube, and the tip of the microneedle extends 1-2 mm outside the polyimide tube; The polyimide tube has a diameter of 0.2-0.3 mm and a thickness of 0.02-0.04 mm; The tube opening of the polyimide tube close to the tip of the micro needle is sealed by oily original glue.

3. The all-solid-state hydrogen ion selective electrode according to claim 1 or 2, characterized in that: The hydrogen ion sensitive membrane is made of an ion exchanger, a hydrogen ion carrier, a plasticizer and a polymer matrix material.

4. The all-solid-state hydrogen ion selective electrode according to claim 3, characterized in that: The ion exchanger is at least one of potassium tetraphenylborate, sodium tetraphenylborate, potassium tetrachlorophenylborate and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate; The hydrogen ion carrier is at least one of tri-n-dodecylamine, diphenylamine and triphenylamine; The plasticizer is at least one of bis(2-ethylhexyl) sebacate, o-nitrophenyl octyl ether, di-n-pentyl phthalate, dioctyl phthalate and dioctyl sebacate; The polymer matrix material is at least one of polyvinyl chloride, polyurethane, polyvinyl acetate and polymethyl methacrylate.

5. The all-solid-state hydrogen ion selective electrode according to claim 4, characterized in that: The mass ratio of the ion exchanger, the hydrogen ion carrier, the plasticizer and the polymer matrix material is 1:2.8-3.0:185-190:90-95.

6. A method for preparing the all-solid-state hydrogen ion selective electrode according to any one of claims 1 to 5, comprising the following steps: S1, applying a graphene water-based coating on the tip of the microneedle to obtain the graphene conductive layer; S2, using a three-electrode system, electroplating a poly(3,4-ethylenedioxythiophene) / poly(sodium 4-styrenesulfonate) layer on the surface of the graphene conductive layer to obtain the solid contact layer; S3, using an artificial dip coating method to coat the tip of the microneedle with a hydrogen ion sensitive membrane solution to obtain the hydrogen ion sensitive membrane; The hydrogen ion sensitive membrane solution is prepared from the ion exchanger, the hydrogen ion carrier, the plasticizer and the polymer matrix material; S4, activating the microneedles in a hydrochloric acid solution.

7. The preparation method according to claim 6, characterized in that: In step S1, the molar ratio of the 3,4-ethylenedioxythiophene to the poly(sodium 4-styrene sulfonate) is 1:10; The electroplating conditions are as follows: electroplating at a rate of 0.08-0.12 V / s using cyclic voltammetry, 8-16 cycles of scanning, and a voltage range of -0.2-1.5 V; After the electroplating is completed, the mixture is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

8. The preparation method according to claim 6 or 7, characterized in that: In step S3, the hydrogen ion sensitive membrane solution is prepared from tetrahydrofuran or cyclohexanone; After the hydrogen ion sensitive membrane is dip-coated, it is placed in a constant temperature drying oven and dried for 12-24 hours at a drying temperature of 30-40°C.

9. Use of the all-solid-state hydrogen ion selective electrode according to any one of claims 1 to 5 in detecting hydrogen ion concentration.

10. A method for detecting hydrogen ion concentration, comprising the following steps: The all-solid-state hydrogen ion selective electrode according to any one of claims 1 to 5 is used to detect the voltage of the ion to be measured in the solution to be measured; and the voltage of the ion to be measured is converted into the concentration of the ion to be measured by the Nernst equation.

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