CN107957440B - Planar ammonia selective sensing electrode and method for fabricating the same - Google Patents
Planar ammonia selective sensing electrode and method for fabricating the same Download PDFInfo
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- CN107957440B CN107957440B CN201710377336.3A CN201710377336A CN107957440B CN 107957440 B CN107957440 B CN 107957440B CN 201710377336 A CN201710377336 A CN 201710377336A CN 107957440 B CN107957440 B CN 107957440B
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/307—Disposable laminated or multilayered electrodes
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/333—Ion-selective electrodes or membranes
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/304—Gas permeable electrodes
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/48—Systems using polarography, i.e. measuring changes in current under a slowly-varying voltage
Abstract
The present disclosure relates to a planar ammonia selective sensing electrode for water quality monitoring and a method for manufacturing the same. The structure comprises an electric insulating substrate, a conductive layer, an ammonium ion sensing layer, a hydroxyl ion sensing layer and an electrolyte layer. The electrically insulating substrate has at least one planar surface. The conductive layer is disposed on at least one plane of the electrically insulating substrate. The conductive layer has at least one first conductive part and at least one second conductive part, and the first conductive part and the second conductive part are insulated and isolated from each other and are respectively provided with a first reaction area and a second reaction area. The ammonium ion sensing layer is arranged in the first reaction area of the first conductive part. The hydroxyl ion sensing layer is arranged in the second reaction area of the second conductive part. The electrolyte layer is arranged and covered on the ammonium ion sensing layer and the hydroxyl ion sensing layer. The method for manufacturing the planar ammonia selective sensing electrode can greatly reduce the volume of the sensing electrode, so that the planar ammonia selective sensing electrode has high selectivity and sensitivity.
Description
Technical Field
The present disclosure relates to sensing electrodes for water quality monitoring, and more particularly, to a planar ammonia-selective sensing electrode and a method for fabricating the same.
Background
The sampling and analysis of the traditional water quality monitoring usually consumes a lot of time and manpower, and can not effectively reflect the problems of poor wastewater treatment effect or abnormal water quality of treated water and the like immediately, so that the quality of the discharged wastewater affects the river. In order to meet the actual requirements, the water quality monitoring device must be able to analyze the water quality in real time so as to effectively control the water treatment effect and the water quality change condition, thereby improving the operation of coping with the treatment procedure. On the other hand, the requirement that the water quality monitoring device must be capable of carrying out on-line real-time monitoring is greatly improved for the requirement of water recycling.
However, the conventional water quality monitoring device uses a glass electrode as its ion sensing electrode. Although the glass electrode can stably measure the ion concentration in water, the glass electrode has a complicated structure and high cost, and is not favorable for miniaturization. In addition, the sensitivity of sensing cannot be effectively improved due to the structure of the glass electrode and the reference electrode of the water quality monitoring device.
In view of the foregoing needs and problems, there is a need for a planar ammonia-selective sensing electrode and a method for fabricating the same for use in water quality monitoring.
Disclosure of Invention
The present disclosure is directed to a planar ammonia-selective sensing electrode and a method for fabricating the same. The ammonium ion sensing layer and the hydroxyl ion sensing layer are planarly arranged on a conductive layer by a liquid drop coating method, a sputtering method, an electrodeposition method or a screen printing thick film technology so as to improve the accuracy and greatly reduce the volume of the sensing electrode. Meanwhile, the planar ammonia selective sensing electrode has high selectivity and sensitivity, and can be applied to the fields of medicine, biochemistry, chemistry, agriculture, environment and the like, such as monitoring the ammonia nitrogen concentration change in the water plant cultivation process, the ammonia nitrogen concentration change of human sweat, the water quality monitoring of aquaculture, or monitoring specific biological indexes (such as creatine) by combining with specific enzymes.
Another object of the present disclosure is to provide a planar ammonia-selective sensing electrode and a method for fabricating the same. The structure is small and compact, the manufacturing process is simple, the cost is low, and the purpose of providing a disposable sensing electrode is more favorably realized.
To achieve the aforesaid objective, the present disclosure provides a planar ammonia-selective sensing electrode, which includes an electrically insulating substrate, a conductive layer, an ammonium ion sensing layer, a hydroxyl ion sensing layer, and an electrolyte layer. The electrically insulating substrate has at least one planar surface. The conductive layer is disposed on at least one plane of the electrically insulating substrate. The conductive layer has at least one first conductive part and at least one second conductive part, and the first conductive part and the second conductive part are insulated and isolated from each other and are respectively provided with a first reaction area and a second reaction area. The ammonium ion sensing layer is arranged in the first reaction area of the first conductive part. The hydroxyl ion sensing layer is arranged in the second reaction area of the second conductive part. The electrolyte layer is arranged and covered on the ammonium ion sensing layer and the hydroxyl ion sensing layer.
To achieve the aforesaid objective, the present disclosure further provides a method for fabricating a planar ammonia-selective sensing electrode, comprising: (a) providing an electric insulation substrate with at least one plane, and forming a conducting layer on the at least one plane of the electric insulation substrate, wherein the conducting layer is provided with at least one first conducting part and at least one second conducting part which are insulated and isolated from each other and respectively assembled with a first reaction area and a second reaction area; (b) respectively forming an ammonium ion sensing layer and a hydroxide ion sensing layer to cover the first reaction area of the first conductive part and the second reaction area of the second conductive part; and (c) forming an electrolyte layer covering the ammonium ion sensing layer and the hydroxyl ion sensing layer.
Drawings
Fig. 1 is an exploded view of a planar ammonia-selective sensing electrode according to a preferred embodiment of the present disclosure.
Fig. 2 is an exemplary sensing voltage response curve of the planar ammonia-selective sensing electrode of the present disclosure.
FIG. 3 is a calibration curve of the relationship between the sensing data voltage and the ammonia concentration of the planar ammonia-selective sensing electrode and the conventional ammonia sensing electrode according to the preferred embodiment of the present disclosure.
Fig. 4 is a flowchart illustrating a method for fabricating a planar ammonia-selective sensing electrode according to a preferred embodiment of the present disclosure.
Description of reference numerals:
1: plane ammonia selective sensing electrode (short for sensing electrode)
10: electrically insulating substrate 11: plane surface
20: conductive layer 21: a first conductive part
22: second conductive portion 23: a first reaction zone
24: second reaction zone 25: working electrode connection area
26: counter electrode connection region 30: insulating waterproof layer
40: ammonium ion sensing layer 50: pH sensing layer
60: middle spacer 61: opening of the container
70: electrolyte layer 80: gas permeable layer
S1-S5: step (ii) of
Detailed Description
Some exemplary embodiments that incorporate the features and advantages of the present disclosure will be described in detail in the specification which follows. It is to be understood that the disclosure is capable of various modifications in various embodiments without departing from the scope of the disclosure, and that the description and drawings are to be regarded as illustrative in nature, and not as restrictive.
The present disclosure discloses a planar ammonia selective sensing electrode (planar ammonia selective sensing electrode), which mainly includes an insulating substrate (insulating base plate), a conductive layer (electric-conductive layer), an ammonium ion sensing layer (ammonium ion sensing layer), a hydroxyl ion sensing layer (hydroxyl ion sensing layer), and an electrolyte layer (electrolytic layer). In the present disclosure, the hydroxyl ion sensing layer can be, for example but not limited to, a pH sensing layer or a pH sensing layer (pH sensing layer). The conducting layer is arranged on the plane of the electric insulation substrate, wherein the conducting layer is provided with at least one first conducting part and at least one second conducting part, the first conducting part and the second conducting part are insulated and isolated from each other, and are respectively assembled with a first reaction area and a second reaction area. The ammonium ion sensing layer is arranged in the first reaction area of the first conductive part. The hydroxyl ion sensing layer is arranged in the second reaction area of the second conductive part. The electrolyte layer is arranged and covered on the ammonium ion sensing layer and the hydroxyl ion sensing layer. The planar ammonium ion sensing layer and the planar hydroxyl ion sensing layer are disposed on the conductive layer by using a droplet coating method, a sputtering method, an electrodeposition method or a screen printing thick film technology, and the volume of the planar ammonia selective sensing electrode can be greatly reduced without misalignment, so that the planar ammonia selective sensing electrode has high selectivity and sensitivity.
Please refer to fig. 1, which is an exploded view of a planar ammonia selective sensing electrode according to a preferred embodiment of the present disclosure. As shown in the drawings, the disclosed planar ammonia selective sensing electrode (hereinafter referred to as "sensing electrode") 1 includes an electrically insulating substrate 10, a conductive layer 20, an insulating and waterproof layer 30, an ammonium ion sensing layer 40, a pH sensing layer 50, a middle spacer 60, an electrolyte layer 70, and a gas permeable layer 80. Wherein the electrically insulating substrate 10 has at least one flat surface 11. The conductive layer 20 includes a first conductive portion 21 and a second conductive portion 22, which are respectively disposed on at least one plane 11 of the electrically insulating substrate 10 and are insulated and isolated from each other. In the present embodiment, the first conductive portion 21 and the second conductive portion 22 are preferably disposed on the same plane 11. The first conductive part 21 and the second conductive part 22 have a first reaction region 23 and a second reaction region 24, respectively. The insulating waterproof layer 30 is disposed on the conductive layer 20, at least partially covers the first conductive portion 21 and the second conductive portion 22 of the conductive layer 20, and the first conductive portion 21 and the second conductive portion 22 are partially exposed, wherein the portions of the first conductive portion 21 and the second conductive portion 22 exposed outside the insulating waterproof layer 30 are respectively configured as a first reaction region 23 and a second reaction region 24. Preferably, the first reaction region 23 and the second reaction region 24 of the first conductive portion 21 and the second conductive portion 22 are relatively adjacent to each other with a fine gap therebetween, thereby facilitating miniaturization of the overall structure. More preferably, the first reaction region 23 and the second reaction region 24 are respectively located at the ends of the first conductive portion 21 and the second conductive portion 22. The ammonium ion sensing layer 40 and the pH sensing layer 50 are respectively disposed on the exposed portions of the first conductive portion 21 and the second conductive portion 22, which are not covered by the insulating waterproof layer 30, that is, respectively disposed in the first reaction region 23 and the second reaction region 24. In other words, the insulating waterproof layer 30, the ammonium ion sensing layer 40 and the pH sensing layer 50 cover the conductive layer 20, wherein the insulating waterproof layer 30, the ammonium ion sensing layer 40 and the pH sensing layer 50 can be, but are not limited to, disposed in a coplanar manner. In a preferred embodiment, except that the first reaction region 23 and the second reaction region 24 are respectively located at each end of the first conductive part 21 and the second conductive part 22, the first conductive part 21 and the second conductive part 22 respectively have a working electrode connection region 25 and a pair of electrode connection regions 26 at the other end opposite to the first reaction region 23 and the second reaction region 24, which are exposed without being covered by the insulating waterproof layer 30 and connected to the measurement connection circuit (not shown) to form a sensing circuit. In addition, the electrolyte layer 70 is disposed on the ammonium ion sensing layer 40 and the pH sensing layer 50, and covers the ammonium ion sensing layer 40 and the pH sensing layer 50. In the present embodiment, the sensing electrode 1 further includes a middle spacer 60 having an opening 61, wherein the middle spacer 60 is disposed around the ammonium ion sensing layer 40, the pH sensing layer 50 and the electrolyte layer 70, so that the electrolyte layer 70 penetrates through the opening 61 and is accommodated in the inner peripheral surface of the opening 61 and contacts the ammonium ion sensing layer 40 and the pH sensing layer 50. In addition, the sensing electrode 1 further includes a gas permeable layer 80 disposed on the electrolyte layer 70 and attached to the middle spacer 60, so that the electrolyte layer 70 is held between the gas permeable layer 80 and the ammonium ion sensing layer 40 and the pH sensing layer 50, and is used for transmitting the target sensing ions generated from the gas permeable layer 80 to the ammonium ion sensing layer 40 and the pH sensing layer 50 through the electrolyte layer 70.
In the present embodiment, the target sensing ions of the ammonium ion sensing layer 40 and the pH sensing layer 50 are ammonium ions (NH) respectively4 +) And hydroxyl ion (OH)-). Ammonium ion (NH) is generated due to the dissolution of ammonia in water4 +) And hydroxide ion (OH)-) The chemical reaction formula is shown as (formula 1). The ammonia molecules in the water sample diffuse through the gas permeable layer 80 into the electrolyte layer 70 to cause ammonium ions (NH) in the electrolyte4 +) And hydroxyl ion (OH)-) The concentration changes and then is transmitted to the ammonium ion sensing layer 40 and the pH sensing layer 50, respectively. Wherein the ammonium ion (NH)4 +) The electrochemical membrane voltage changes due to the reaction with the ammonium ion reactive layer 40, and the membrane voltage generated at the ammonium ion reactive layer 40 is larger as the ammonium ion concentration in the aqueous solution is higher. On the other hand, when ammonia is dissolved in an aqueous solution, hydroxide ions (OH) are also generated-) The aqueous solution is alkaline, and the pH sensing layer 50 senses hydroxyl ions (OH)-) Is growing negatively. In other words, the more alkaline the aqueous solution itself, the more hydroxide ions (OH) are sensed by the pH sensing layer 50-) The smaller the voltage. Therefore, when ammonia exists in the aqueous solution, signals sensed at the ammonium ion sensing layer 40 and the pH sensing layer 50 are added, so that the sensing electrode 1 of the present invention can greatly improve the sensitivity of conventional electrochemical measurement of ammonia concentration.
Fig. 2 is an exemplary sensing voltage response curve of the planar ammonia-selective sensing electrode of the present disclosure. FIG. 3 is a calibration curve of the relationship between the sensing data voltage and the ammonia concentration of the planar ammonia-selective sensing electrode and the conventional ammonia sensing electrode according to the preferred embodiment of the present disclosure. As shown, when the ammonia/ammonium concentration in aqueous solution increases, the conventional way of measuring the membrane potential is to sense the voltage E only with respect to the reference electrode silver/silver chloride, i.e., the ammonia/ammonium concentrationNH4+＝EWorking(NH4+)-EReference. Sensing voltage E relative to the ammonia/ammonium concentration of silver/silver chloride of the reference electrode as the ammonia/ammonium concentration is higherNH4+The higher the change, and the change can only correspond to the slope change of 59.2 + -2 mV/(10 times) of the electrochemical energy equation. However, in this embodiment, since the change of the pH value in the aqueous solution is calculated at the same time, i.e. the pH sensing voltage E of silver/silver chloride relative to the reference electrode is calculated at the same timepH＝EWorking(pH)-EReferenceWhen the aqueous solution is affected by the dissolution of ammonia, a reaction occurs as shown in formula 1, resulting in the increase of the pH of the aqueous solution, i.e., the pH sensing voltage EpHThe lower will be. Therefore, in the present embodiment, the sensing electrode 1 is measured by using the ammonia/ammonium concentration sensing voltage ENH4+And pH sensing voltage EpHA difference of (i.e. E)NH4+-EpH＝EWorking(NH4+)-EWorking(pH)So that the sensitivity slope of the planar ammonia-selective sensing electrode 1 of the present disclosure varies 132 ± 3mV/(10 times), which is much higher than the sensitivity of the aforementioned conventional ammonia sensing electrode 59.2 ± 2mV/(10 times), as shown in fig. 3 and the following table 1.
Table 1: the performance of the planar ammonia selective sensing electrode of the preferred embodiment of the present disclosure is compared with that of the conventional ammonia sensing electrode.
| The disclosed planar ammonia-selective sensing electrode | Conventional ammonia sensing electrode | |
| Linear range | 0.01～1400ppm | 0.01～1400ppm |
| Degree of linearity | R2＝0.9901 | R2＝0.9954 |
| Sensitivity of the probe | 132mV/10 times | 59.2mV/10 times |
On the other hand, according to the aforementioned preferred embodiment of the planar ammonia-selective sensing electrode structure, the present disclosure also discloses a method for fabricating the planar ammonia-selective sensing electrode. Fig. 4 is a flowchart illustrating a method for fabricating a planar ammonia-selective sensing electrode according to a preferred embodiment of the present disclosure. Referring to fig. 1 and fig. 4, in step S1, an electrically insulating substrate 10 having at least one plane 11 is provided, and a conductive layer 20 is formed on the at least one plane 11 of the electrically insulating substrate 10. The conductive layer 20 includes a first conductive portion 21 and a second conductive portion 22, which are respectively disposed on at least one plane 11 of the electrically insulating substrate 10 by, for example, but not limited to, screen printing or sputtering, and are insulated and isolated from each other. The first conductive part 21 and the second conductive part 22 have a first reaction region 23 and a second reaction region 24, respectively. Next, in step S2, an insulating waterproof layer 30 is formed on the conductive layer 20, partially covering the first conductive part 21 and the second conductive part 22 of the conductive layer 20, and partially exposing the first conductive part 21 and the second conductive part 22, respectively, wherein the exposed portions of the first conductive part 21 and the second conductive part 22 outside the insulating waterproof layer 30 are respectively configured as a first reaction region 23 and a second reaction region 24. In the present embodiment, the insulating and waterproof layer 30 is covered on the conductive layer 20 by using, for example, but not limited to, screen printing or chemical vapor deposition technology, and the uncovered portion of the conductive layer 20 is assembled to form the first reaction region 23 of the first conductive part 21 and the second reaction region 24 of the second conductive part 22. The first reaction region 23 of the first conductive portion 21 and the second reaction region 24 of the second conductive portion 22 are disposed adjacent to each other with a fine gap, which is beneficial to miniaturization of the whole structure. In a preferred embodiment, except that the first reaction area 23 and the second reaction area 24 are respectively located at each end of the first conductive part 21 and the second conductive part 22, the other ends of the first conductive part 21 and the second conductive part 22 opposite to the first reaction area 23 and the second reaction area 24 are not covered by the insulating waterproof layer 30, and are respectively configured and configured as a working electrode connection area 25 and a pair of electrode connection areas 26 for forming a sensing circuit, which does not limit the necessary technical features of the present disclosure, and are not described herein again. Next, in step S3, the ammonium ion sensing layer 40 and the pH sensing layer 50 are formed on the first reaction region 23 of the first conductive part 21 and the second reaction region 24 of the second conductive part 22 of the conductive layer 20, respectively. In the embodiment, the insulating waterproof layer 30, the ammonium ion sensing layer 40 and the pH sensing layer 50 are covered on the conductive layer 20, so the sequence of the insulating waterproof layer 30, the ammonium ion sensing layer 40 and the pH sensing layer 50 formed on the conductive layer 20 is not limited, and can be optimally adjusted according to the actual application requirements, which is not described herein again. Next, in step S4, an electrolyte layer 70 is formed to cover the ammonium ion sensing layer 40 and the pH sensing layer 50. In the present embodiment, the opening 61 of the middle spacer 60 is used to define an electrolyte filling region, wherein the middle spacer 60 is disposed around the ammonium ion sensing layer 40, the pH sensing layer 50 and the electrolyte layer 70, so that the electrolyte layer 70 penetrates through the opening 61 and is accommodated in the inner circumferential surface of the opening 61 and contacts the ammonium ion sensing layer 40 and the pH sensing layer 50. The intermediate spacer 60 may be made of a material such as, but not limited to, polyethylene terephthalate (PET). The electrolyte layer 70 may be formed by, for example, but not limited to, a 0.01M tris aqueous solution filled in an electrolyte filled region defined in the inner peripheral surface of the opening 61 of the septum 60. Finally, in step S5, a gas-permeable layer 80 is formed on the electrolyte layer 70 and attached to the middle spacer 60, so that the electrolyte layer 70 is held between the gas-permeable layer 80 and the ammonium ion sensing layer 40 and the pH sensing layer 50, i.e., the electrolyte layer 70 is accommodated in the electrolyte-filled region defined in the inner peripheral surface of the opening 61 of the middle spacer 60. In the present embodiment, the gas-permeable layer 80 can be, for example, but not limited to, a polytetrafluoroethylene gas-permeable layer with a thickness of 10 μm.
In the present embodiment, the conductive layer 20 can be formed on the plane 11 of the electrically insulating substrate 10 by, for example, but not limited to, screen printing or sputtering. Wherein the first reaction region 23 and the second reaction region 24 of the conductive layer 20, which are covered by the ammonium ion sensing layer 40 and the pH sensing layer 50 respectively, are ammonium ions (NH) respectively4 +) Reaction electrode area and hydroxyl ion (OH)-) The reaction electrode area and the rest part are covered and protected by the insulating waterproof layer 30. In a preferred embodiment, the first conductive part 21 and the second conductive part 22 further have a working electrode connection region 25 and a pair of electrode connection regions 26 at the other end of the first reaction region 23 and the second reaction region 24 covered by the ammonium ion sensing layer 40 and the pH sensing layer 50, respectively, and are connected to the measurement connection lines (not shown) to form the sensing circuit. In the present embodiment, the conductive layer 20 can be, for example, but not limited to, a sputtered metal film, and the material thereof can be selected from a screen-printed silver-carbon conductive paste, gold paste, platinum paste, silver paste, conductive carbon paste, gold, palladium, platinum, gold-palladium alloy, silver, or a combination thereof. Electrically insulating substrate 10 may be comprised of, for example, but not limited to, a polyethylene terephthalate (PET) or ceramic substrate. In one embodiment, the conductive layer 20 is formed on the electrically insulating substrate 10 by printing, and then dried at 60 ℃ to 140 ℃.
In the present embodiment, the first reaction region 23 of the first conductive part 21 of the conductive layer 20 is covered by the ammonium ion sensing layer 40, and the second reaction region is covered by the ammonium ion sensing layerThe second reaction region 24 of the conductive portion 22 is covered by the pH sensing layer 50, so that ammonium ions (NH) are formed in the first reaction region 23 and the second reaction region 24 respectively4 +) And hydroxyl ion (OH)-) A reaction electrode area for transmitting the voltage variation generated by the electrochemical membrane potential measured between the ammonium ion sensing layer 40 and the pH sensing layer 50, and transmitting the electric signal to the measurement connection circuit through the working electrode connection area 25 of the first conductive part 21 and the counter electrode connection area 26 of the second conductive part 22 of the conductive layer 20, respectively. In one embodiment, the measurement connection line is further connected to a measuring instrument (not shown), which can display and calculate the ammonia concentration corresponding to the sensed voltage change, so as to be conveniently used by a subsequent user.
In addition, in the embodiment, the insulating and waterproof layer 30 may be made of, for example, but not limited to, electrically insulating and waterproof materials, such as paraxylene polymer, screen printing insulating paste, screen printing UV insulating paste, and the like. In an embodiment, the waterproof insulation layer 30 is formed by a screen printing insulation paste coating and is dried at 60 ℃ to 140 ℃, for example, the waterproof insulation layer 30 partially covers the first conductive part 21 and the second conductive part 22 of the conductive layer 20, and the first conductive part 21 and the second conductive part 22 are partially exposed to form the first reaction area 23 and the second reaction area 24, respectively, for covering the ammonium ion sensing layer 40 and the pH sensing layer 50. In a preferred embodiment, the first reaction region 23 and the second reaction region 24 covered by the ammonium ion sensing layer 40 and the pH sensing layer 50 in the first conductive part 21 and the second conductive part 22 are insulated and isolated from each other, and are disposed adjacent to each other with a small gap, so as to facilitate miniaturization of the sensing electrode 1.
In the embodiment of the present disclosure, the ammonium ion sensing layer 40 and the pH sensing layer 50 can be formed by, for example but not limited to, a droplet coating method, a sputtering method, an electrodeposition method, or a screen printing thick film technique. In the present embodiment, the ammonium ion sensing layer 40 formed on the first reaction region 23 of the first conductive portion 21 of the conductive layer 20 is an ammonium ion selective film, and the material of which includes, for example, but not limited to, an ion carrier, a plasticizer, a heat-resistant resin, or a combination thereof. In a preferred embodiment, the ammonium ion sensing layer 40 further comprises a cation exchanger, and the weight of each component of the ammonium ion sensing layer 40 can be, for example but not limited to, between 0.2 wt% and 5 wt% of an ion carrier, between 50 wt% and 70 wt% of a plasticizer, between 30 wt% and 60 wt% of a heat-resistant resin, and between 0.1 wt% and 2.5 wt% of a cation exchanger. The mixed solution of the aforementioned ionophore, plasticizer, heat-resistant resin and cation exchanger is applied to the exposed portion of the first conductive portion 21 of the conductive layer 20 to form the ammonium ion sensing layer 40 by droplet coating, wherein the volume of the droplet is between 10 μ L and 50 μ L, and the mixture is dried at 30 ℃ to 60 ℃ for 2 to 10 hours, and then dried at 40 ℃ to 60 ℃ for 6 to 18 hours under vacuum, thereby completing the fabrication of the ammonium ion sensing layer 40.
Alternatively, the pH sensing layer 50 may be formed by electrodepositing iridium oxide (IrO) using, for example, but not limited to, electrochemical amperometry or cyclic voltammetry2) And a second reaction region 24 exposed to form a pH sensing layer 50 is deposited on the second conductive portion 22 of the conductive layer 20. In one embodiment, the pH sensing layer 50 is formed by chronoamperometry with iridium oxide (IrO)2) A second reaction region 24 disposed on the second conductive part 22 of the conductive layer 20 and exposed for forming a pH sensing layer 50, wherein the current density is in the range of 0.2mA/cm2To 5mA/cm2In the meantime. In another embodiment, the pH sensing layer 50 may be formed by cyclic voltammetry of iridium oxide (IrO)2) The voltage range of the second reaction region 24 exposed to form the pH sensing layer 50 deposited on the second conductive portion 22 of the conductive layer 20 may be-0.2V to 1.3V, the scan rate may be 10mV/s to 100mV/s, and the number of scan cycles may be 10 to 100 cycles. In an embodiment, the pH sensing layer 50 after the electrodeposition may be further cleaned by deionized water, and then dried at 80 ℃ for 1 hour to dry the excess water, thereby completing the fabrication of the pH sensing layer 50. In the present embodiment, the plating solution used for forming the pH sensing layer 50 may include, for example, but not limited to, iridium chloride (IrCl)x) Wherein X is 3-4 wt% of hydrogen peroxide, 30 wt% of oxalic acid, 3M potassium carbonate and is deionizedSub-water, wherein iridium chloride (IrCl)x) The weight percentage of the oxalic acid is between 0.2 and 0.6, the weight percentage of the 3M potassium carbonate is between 6 and 12, and the weight percentage of the deionized water is between 80 and 90.
In the above embodiment, the middle partition 60 is disposed around the ammonium ion sensing layer 40 and the pH sensing layer 50, and an electrolyte filling region is defined in the inner peripheral surface of the opening 61 of the middle partition 60 to fill the electrolyte layer 70. In one embodiment, the septum 60 may be made of, for example, but not limited to, polyethylene terephthalate (PET) or polyvinyl chloride (PVC). In a preferred embodiment, the spacer 60 is made of polyethylene terephthalate (PET), has a thickness of 0.35mm, and is coated with a back adhesive on the back surface thereof, and is attached to the plane 11 of the electrically insulating substrate 10 and is disposed around the ammonium ion sensing layer 40 and the pH sensing layer 50, and then is pressed and left for 12 hours by a roller press, so that the attachment is more secure, and an electrolyte filling region is defined in the inner peripheral surface of the opening 61 of the spacer 60 to fill the electrolyte layer 70.
In the foregoing embodiment, the material of the electrolyte layer 70 is a liquid electrolyte, and may be, for example, but not limited to, an aqueous hydrochloric acid solution, an aqueous potassium chloride solution, an aqueous potassium hydroxide solution, an aqueous sodium chloride solution, an aqueous phosphate buffer solution, an aqueous Tris (hydroxymethyl) aminomethane (Tris) solution, or an aqueous ammonium chloride solution, and the concentration range is between 0.01M and 1M. In one embodiment, the electrolyte may be a solid electrolyte, such as but not limited to Agarose gel (Agarose), Polyacrylamide gel (Polyacrylamide), Gelatin (Gelatin), or Calcium alginate (Calcium alginate). In a preferred embodiment, the electrolyte layer 70 is completed by filling the opening 61 (i.e., the electrolyte filling region) of the middle spacer 60 with 0.01M tris aqueous solution and a dispensing volume of 500 μ L fixed by a dispenser.
In addition, the material of the gas-permeable layer 80 in the previous embodiments may be made of, for example, but not limited to, cellulose acetate, silicone rubber, Polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), poly-bis-methyl siloxane (PDMS), polyvinyl chloride (PVC), natural rubber, or a combination thereof. In the present embodiment, the thickness of the gas permeable layer 80 may be between 0.1 μm and 30 μm. In a preferred embodiment, the gas-permeable layer 80 is made of a teflon film with a thickness of 10 μm, the back surface thereof is coated with a back adhesive, the teflon film is attached to the middle spacer 60 by an attaching jig to cover the electrolyte layer 70, and the electrolyte layer 70 is sealed in the opening 61 of the middle spacer 60, thereby forming the sensing electrode 1 of the present disclosure.
In summary, the present disclosure provides a planar ammonia-selective sensing electrode and a method for fabricating the same. The ammonium ion sensing layer and the hydroxyl ion sensing layer are planarly arranged on a conductive layer by a liquid drop coating method, a sputtering method, an electrodeposition method or a screen printing thick film technology so as to improve the accuracy and greatly reduce the volume of the sensing electrode. Meanwhile, the planar ammonia selective sensing electrode has high selectivity and sensitivity, and can be applied to the fields of medicine, biochemistry, chemistry, agriculture, environment and the like, such as monitoring the ammonia nitrogen concentration change in the water plant cultivation process, the ammonia nitrogen concentration change of human sweat, the water quality monitoring of aquaculture, or monitoring specific biological indexes (such as creatine) by combining with specific enzymes. The structure is small and compact, the manufacturing process is simple, the cost is low, and the purpose of providing the disposable sensing electrode is more favorably realized.
Claims (11)
1. A planar ammonia-selective sensing electrode, comprising:
an electrically insulating substrate having at least one planar surface;
a conductive layer disposed on the at least one plane of the electrically insulating substrate, wherein the conductive layer has at least a first conductive part and at least a second conductive part, the first conductive part and the second conductive part are insulated and isolated from each other, and are respectively assembled with a first reaction region and a second reaction region;
an ammonium ion sensing layer disposed on the first reaction region;
a hydroxyl ion sensing layer arranged on the second reaction area; and
an electrolyte layer disposed and covering on the ammonium ion sensing layer and the hydroxyl ion sensing layer.
2. The planar ammonia-selective sensing electrode of claim 1, further comprising an insulating and waterproof layer disposed on the conductive layer, partially covering the first conductive portion and the second conductive portion, and configuring the first conductive portion and the second conductive portion to form the first reaction region and the second reaction region, respectively.
3. The planar ammonia-selective sensing electrode of claim 1, further comprising a middle spacer disposed on the at least one planar surface of the electrically insulating substrate, wherein the middle spacer has an opening, the middle spacer is disposed at the periphery of the ammonium ion sensing layer and the hydroxide ion sensing layer, and the electrolyte layer is received in the inner peripheral surface of the opening.
4. The planar ammonia-selective sensing electrode of claim 3, further comprising a gas-permeable layer disposed over and abutting the electrolyte layer and the separator, such that the electrolyte layer is retained between the gas-permeable layer and the ammonium ion sensing layer and the hydroxide ion sensing layer.
5. The planar ammonia-selective sensing electrode of claim 1, wherein the hydroxide ion sensing layer is a ph sensing layer.
6. A method for fabricating a planar ammonia-selective sensing electrode includes the steps of:
step a: providing an electric insulation substrate with at least one plane, and forming a conducting layer on the at least one plane of the electric insulation substrate, wherein the conducting layer is provided with at least one first conducting part and at least one second conducting part, the first conducting part and the second conducting part are insulated and isolated from each other and are respectively provided with a first reaction area and a second reaction area;
step b: forming an ammonium ion sensing layer and a hydroxide ion sensing layer respectively covering the first reaction region and the second reaction region; and
step c: forming an electrolyte layer covering the ammonium ion sensing layer and the hydroxyl ion sensing layer.
7. The method of claim 6, wherein the step b further comprises:
step b 1: forming an insulating waterproof layer on the conductive layer, partially covering the first conductive part and the second conductive part, and respectively assembling the first conductive part and the second conductive part to form the first reaction area and the second reaction area.
8. The method of claim 6, wherein the step c further comprises:
step c 1: providing a middle spacer with an opening, and bonding the middle spacer to the at least one plane of the electric insulation substrate, so that the middle spacer is arranged at the peripheries of the ammonium ion sensing layer and the hydroxyl ion sensing layer, and the electrolyte layer is accommodated in the inner peripheral surface of the opening.
9. The method of claim 8, further comprising:
step d: and forming a gas-permeable layer on the electrolyte layer and attaching the gas-permeable layer to the middle spacer, so that the electrolyte layer is kept in the inner peripheral surface of the opening of the middle spacer.
10. The method of claim 6, wherein the hydroxyl ion sensing layer is a pH sensing layer.
11. The method of claim 6, wherein the ammonium ion sensing layer and the hydroxide ion sensing layer in step b are formed by droplet coating, sputtering, electrodeposition or screen printing.
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| CN111855754B (en) * | 2019-04-29 | 2021-12-03 | 深圳安吉尔饮水产业集团有限公司 | Water hardness detection probe, sensor, detection method and water softener |
| CN113916954A (en) * | 2021-09-30 | 2022-01-11 | 上海交通大学 | On-chip in-situ micro silver chloride reference electrode and preparation method thereof |
| CN115739110B (en) * | 2022-11-04 | 2024-01-30 | 湖州美奇医疗器械有限公司 | Preparation method and application of platinum-based catalyst |
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| TWI631329B (en) | 2018-08-01 |
| TWI625522B (en) | 2018-06-01 |
| TW201816397A (en) | 2018-05-01 |
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| TW201816396A (en) | 2018-05-01 |
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