All-solid-state potassium ion selective electrode and method for manufacturing the same

Abstract

To provide a highly stable potassium ion selective electrode and a manufacturing method thereof.SOLUTION: The all-solid-state potassium ion selective electrode includes: a conductor; an insert material formed over the surface of the conductor; and a potassium ion-sensitive membrane covering the insert material. The insert material is a mixed material including Prussian blue analog particles and conductive material particles. The Prussian blue analog particles that are expressed by a structure formula KxFe[Fe(CN)6]y*nH2O. The Prussian blue analog particles have at least a monoclinic crystal structure, in which x is a number between 1.5 and 2, y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0.SELECTED DRAWING: Figure 1

Description

[Technical Field] 【0001】 The present invention relates to an all-solid-state potassium ion selective electrode and a method for producing the same. [Background technology] 【0002】 Ion-selective electrodes are used in devices for measuring ion concentrations in liquids and produce a change in potential in response to specific ions. They have diverse applications in environmental technologies, medical technologies, agricultural technologies, and more. 【0003】 Ion-selective electrodes that are sensitive to various types of ions are known. Patent Document 1 discloses magnesium ion-selective electrodes and calcium ion-selective electrodes containing a Prussian blue analog. [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Publication No. 2020-46364 [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 However, conventional technology had the challenge of needing to improve the stability of potassium ion-selective electrodes. 【0006】 This invention was made to solve these problems and aims to provide a potassium ion selective electrode with higher stability and a method for producing the same. [Means for solving the problem] 【0007】 An example of an all-solid-state potassium ion selective electrode according to the present invention is: A conductor and An insertion material formed on the surface of the conductor, A potassium ion-sensitive film covering the insertion material, Equipped with, The insertion material is a mixed material containing Prussian blue analog particles and conductive material particles. The aforementioned Prussian blue analog particles have structural formula K x Fe[Fe(CN)6] y Represented as nH2O, The aforementioned Prussian blue analog particles have a monoclinic crystal structure in at least part of them. x is a number between 1.5 and 2 (inclusive), y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0. 【0008】 An example of a method for producing an all-solid-state potassium ion selective electrode according to the present invention is: A conductor and An insertion material formed on the surface of the conductor, A potassium ion-sensitive film covering the insertion material, A method for manufacturing an all-solid-state potassium ion selective electrode, comprising: The insertion material is a mixed material containing Prussian blue analog particles and conductive material particles. The aforementioned Prussian blue analog particles have structural formula K x Fe[Fe(CN)6] y Represented as nH2O, The aforementioned Prussian blue analog particles have a monoclinic crystal structure in at least part of them. x is a number between 1.5 and 2 (inclusive), y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0. The aforementioned method, A step of supplying a slurry onto a conductor and drying the slurry to form a composite film on the surface of the conductor, The aforementioned mixture film is immersed in the first potassium chloride aqueous solution, and the K in the Prussian blue analog is + The process of forming an insertion material on the surface of the conductor by making the distribution uniform, A step of forming an ion-sensitive primary film on the surface of the insertion material by supplying a potassium ion-sensitive film stock solution to the surface of the insertion material and drying the potassium ion-sensitive film stock solution; A step of forming a potassium ion-sensitive film on the surface of the insertion material by immersing the ion-sensitive primary film in a second potassium chloride aqueous solution; It includes. 【0009】 In one example, The method includes a step of manufacturing the slurry, The step of manufacturing the slurry includes a step of synthesizing Prussian blue analog particles containing a cubic crystal structure in at least part by oxidizing a monoclinic Prussian blue analog. 【0010】 In one example, the method includes a step of holding the potential of the electrode at the redox potential of K2FeFe in an aqueous K2SO4 solution after the step of forming the potassium ion-sensitive film. 【0011】 In one example, The method includes a step of manufacturing the slurry, The step of manufacturing the slurry is, Prussian blue analog particles, Acetylene black or Ketjen black or multi-walled carbon nanotubes, Polyvinylidene fluoride, And a step of mixing them. 【Effect of the Invention】 【0012】 According to the all-solid-state potassium ion-selective electrode and its manufacturing method according to the present invention, the stability of the potassium ion-selective electrode can be further enhanced. 【Brief Description of the Drawings】 【0013】 [Figure 1] Configuration of the ion-selective electrode 10 according to Embodiment 1 of the present invention. [Figure 2] Part of the process for manufacturing the slurry to form the insertion material 2 shown in Figure 1. [Figure 3] An example of X-ray diffraction measurement results for a Prussian blue analog. [Figure 4] Example of particle size measurement results for a Prussian blue analog. [Figure 5] An example of a method for manufacturing an ion-selective electrode 10. [Figure 6] Example of constant current charge / discharge test results. [Figure 7] Example of results from natural potential measurement. [Figure 8] Reproducibility data of natural potential measurements, shown in Figure 7. [Figure 9] Example of long-term stability test results. [Figure 10] An example of polarization test results using chronopotentiometry. [Figure 11] A Nyquist plot as an example of the results of an AC impedance measurement test. [Figure 12] An example of how to use the ion-selective electrode 10. [Figure 13] Configuration of the electrode device 30 according to Embodiment 2. [Figure 14] An example of how to use the electrode device 30 shown in Figure 13. [Modes for carrying out the invention] 【0014】 Hereinafter, embodiments of the present invention will be described based on the attached drawings. [Embodiment 1] Figure 1 shows the configuration of an ion-selective electrode 10 according to Embodiment 1 of the present invention. The ion-selective electrode 10 is an all-solid-state potassium ion-selective electrode. Figure 1(a) is a plan view, and Figure 1(b) is a cross-sectional view taken along the line BB in Figure 1(a). 【0015】 The ion-selective electrode 10 comprises an epoxy resin 5, copper wiring 4 disposed within the epoxy resin 5, a platinum electrode 3 (conductor) connected to the copper wiring 4 and exposed on the surface of the epoxy resin 5, an insertion material 2 formed on the surface of the platinum electrode 3, and a potassium ion-sensitive film 1 covering the insertion material 2. 【0016】 Any insulator can be used instead of the epoxy resin 5, and any conductor can be used instead of the copper wiring 4 and / or platinum electrodes 3. 【0017】 Insertion material 2 is a mixed material containing Prussian blue analog particles and conductive material particles. The Prussian blue analog particles have structural formula K x Fe[Fe(CN)6] y It is represented as nH2O. Here, x is a number between 1.5 and 2, preferably close to 2. Also, y is a number greater than 0 and less than or equal to 1, preferably close to 0. n is a number greater than or equal to 0. 【0018】 Prussian blue analog particles have a monoclinic crystal structure in at least part of their structure. Prussian blue analog particles may also have a cubic crystal structure in part of their structure. 【0019】 The following describes an example of a method for manufacturing the ion-selective electrode 10. The manufacturing method includes a step of manufacturing a slurry for forming the insertion material 2, and the ion-selective electrode 10 is manufactured using the manufactured slurry. Note that K x When a substance containing FeFe is relatively close to 2, it may be written as "K2FeFe". However, this notation does not necessarily mean that the value of x is 2, nor does it limit the range of x. 【0020】 Figure 2 shows part of the process for manufacturing the slurry to form insertion material 2. The process shown in Figure 2 is, in particular, the process for synthesizing the active material contained in the slurry. 【0021】 To synthesize K2FeFe as the active material contained in the slurry, an aqueous potassium ferrocyanide solution (4 mmol K4[Fe II (CN)6]·3H2O) containing divalent iron ions and having a volume of 100 mL is stirred while dropping an aqueous iron(II) chloride solution (4 mmol Fe II Cl2) having a volume of 100 mL (Step S1). It is preferable that these solutions contain tripotassium citrate (1.0 M) for controlling the particle size of K2FeFe and functioning as a K source. The dropping is performed, for example, at 0.5 mL / min under a nitrogen atmosphere. The stirring is performed, for example, at 300 rpm using a stirring blade. 【0022】 As a result, a white precipitate of a monoclinic Prussian blue analogue is obtained from the sample solution. K2FeFe is synthesized in this way. Note that the method for synthesizing K2FeFe is not limited to that shown in FIG. 2 and can be appropriately designed by those skilled in the art. 【0023】 Next, the above white precipitate is stirred (Step S2). The stirring is performed, for example, at 300 rpm for 15 hours at room temperature under a nitrogen atmosphere using a stirring blade. Next, the white precipitate is suction filtered under a nitrogen atmosphere (Step S3). Next, the white precipitate is washed (Step S4). The washing is performed, for example, using ion-exchanged water and ethanol under a nitrogen atmosphere. Since K2FeFe is a substance that is extremely easily oxidized in the air, it is preferable that Steps S1 to S4 in the process of FIG. 2 be carried out under a nitrogen atmosphere as described above so as not to be oxidized during synthesis. 【0024】 Next, the white precipitate is dried (Step S5). The drying is performed, for example, by performing vacuum pumping at 100° C. for 24 hours. 【0025】 The powder sample obtained as a result of Step S5 is exposed to the air for several days. Thereby, a blue powder of K2FeFe is obtained. This blue powder is Prussian blue analogue particles containing at least partially a cubic crystal structure and becomes the active material of the insertion material 2. The blue powder is considered to be a two-phase coexistence of Prussian blue and Prussian white. 【0026】 Thus, the process for producing the slurry includes a step of synthesizing Prussian blue analog particles containing at least a portion of a cubic crystal structure by oxidizing a monoclinic Prussian blue analog. In the example above, oxidation was performed at room temperature by exposure to air for several days, but the oxidation method is not limited to this; it may also be oxidized electrochemically or by other methods. Furthermore, depending on the composition of K2FeFe, the oxidation step may be omitted. 【0027】 Figure 3 shows an example of X-ray diffraction measurement results for a Prussian blue analog. Figure 3(a) shows the case with x=0.36, y=0.67 as a comparative example, and Figure 3(b) shows the case with x=1.69, y=0.86 as an example of this embodiment. In the structural formula in Figure 3, "□" indicates a [Fe(CN)6] defect. 【0028】 In Embodiment 1, a value of x = 1.69 was used, but the value of x is not limited to 1.69; for example, it could be 1.65. It is considered that values ​​of x between 1.5 and 2 exhibit equivalent or similar characteristics. Similarly, in Embodiment 1, a value of y = 0.86 was used, but the value of y can be greater than 0 and less than or equal to 1. As mentioned above, it is preferable that x be close to 2 and y be close to 0. 【0029】 In the figures and this specification, "cubic" may be abbreviated as "c-" and "monoclinic" as "m-". For example, "c-KFeHCF" represents a cubic Prussian blue analog, and "m-KFeHCF" represents a monoclinic Prussian blue analog. 【0030】 As shown in Figure 3(a), compositions with low potassium content and many defects exhibit a cubic phase, while compositions with high potassium content and few defects exhibit a monoclinic phase, as shown in Figure 3(b). 【0031】 Figure 4 shows an example of particle size measurement results for a Prussian blue analog. The horizontal axis represents particle size, and the vertical axis represents volume ratio. Compared to the m-KFeHCF according to Embodiment 1, the c-KFeHCF according to the comparative example has a larger particle size because the particles are slightly aggregated. 【0032】 Figure 5 shows an example of a method for producing an ion-selective electrode 10 using the active material synthesized in this manner. The method includes a step of producing a slurry (step S11). The step of producing the slurry includes mixing the active material (Prussian blue analog particles) synthesized as described above, a conductive material, and a binder. The ratio of active material:conductive material:binder is, for example, 80:10:10 [weight%]. 【0033】 The conductive material is, for example, acetylene black, Ketjen black, or multi-walled carbon nanotubes, and in the example in Figure 5, it is acetylene black (AB). The binder in the example in Figure 5 is polyvinylidene fluoride dispersed in N-methylpyrrolidone (NMP). 【0034】 The slurry produced in this manner is dropped onto the platinum electrode 3 (see Figure 1) (step S12). The amount dropped is, for example, 1 μL. The slurry is then dried (step S13). Drying is carried out, for example, overnight at room temperature. This forms a composite film on the surface of the platinum electrode 3. Thus, the manufacturing method according to Embodiment 1 comprises the step of supplying slurry onto the platinum electrode 3 and drying the slurry to form a composite film on the surface of the platinum electrode 3. 【0035】 As mentioned above, the slurry has structural formula K x Fe[Fe(CN)6] y It contains Prussian blue analog particles represented by nH2O. These Prussian blue analog particles have a monoclinic crystal structure in at least part of them, where x is a number between 1.5 and 2, y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0. 【0036】 Subsequently, the mixture film is immersed in a 0.01 M KCl aqueous solution (first potassium chloride aqueous solution) (step S14). The immersion is carried out for, for example, 24 hours. This provides proper conditioning and K in the Prussian blue analog. + By making the distribution uniform, the insertion material 2 can be formed on the surface of the platinum electrode 3. 【0037】 Next, a potassium ion-sensitive film (K) is applied to the surface of insertion material 2. + -ISM) Add the stock solution dropwise (step S15). The amount added is, for example, 50 μL. The potassium ion-sensitive membrane stock solution contains, for example, an ionophore, a membrane matrix, a membrane solvent, and an anion eliminator. The ionophore is, for example, bis(benzo-15-crown-5), the membrane matrix is, for example, polyvinyl chloride (PVC), the membrane solvent is, for example, o-nitrophenyl octyl ether (o-NPOE), and the anion eliminator is, for example, potassium tetrakis(4-chlorophenyl)borate (K-TCPB). Tetrahydrofuran (THF) is used as the dispersion medium. 【0038】 Next, the potassium ion-sensitive film stock solution is dried (step S16). Drying is carried out, for example, at room temperature overnight. This forms the ion-sensitive film stock solution. 【0039】 Thus, the manufacturing method according to Embodiment 1 comprises the step of supplying a potassium ion-sensitive film stock solution to the surface of the insertion material 2 and drying the potassium ion-sensitive film stock solution to form an ion-sensitive film on the surface of the insertion material 2. 【0040】 Next, this ion-sensitive raw material film is immersed in a 0.01 M KCl aqueous solution (second potassium chloride aqueous solution) (step S17). The immersion is carried out for, for example, 24 hours. This provides appropriate conditioning and forms a potassium ion-sensitive film 1 on the surface of the insertion material 2. In this way, the ion-selective electrode 10 shown in Figure 1 is manufactured. 【0041】 The characteristics of the ion-selective electrode 10 will be described below. 【0042】 Figure 6 shows an example of the results of a constant current charge-discharge test. The test was performed with the following configuration. Cell...SB9 (two-chamber, three-electrode cell) Working electrode (ion-selective electrode 10): PB (Prussian blue):KB (Ketjenblack):PVdF (polyvinylidene fluoride) = 70:20:10 (weight %) Counter-electrode…AC:KB:PTFE (polytetrafluoroethylene) = 80:10:10 (weight %) Reference electrode...Ag / AgCl (saturated KCl) Electrolyte…0.5M K2SO4 aqueous solution Separator... Fiberglass filter Current density…1C (156mAg -1 ) Voltage range: -0.25V to 0.50V vs. Ag / AgCl 【0043】 In Figure 6, the horizontal axis represents the charge / discharge amount, and the vertical axis represents the potential. Figure 6(a) shows the results using the electrodes of the comparative example, with structural formula K x Fe[Fe(CN)6] y This is an example where x is less than 1.5 in nH2O. Hereafter, such a composition may be abbreviated as "c-KFeHCF". As shown in Figure 6(a), the electrode in the comparative example shows a gradient potential change, and is considered to be a single-phase reaction. 【0044】 Figure 6(b) shows the results using the electrode according to Embodiment 1, and the structural formula K x Fe[Fe(CN)6] y This is an example where x is 1.5 or greater in nH2O. Hereafter, such a composition may be abbreviated as "m-KFeHCF". As shown in Figure 6(b), a stable potential flat region is observed in the electrode according to Embodiment 1, and it is considered to be a two-phase reaction. 【0045】 Figure 7 shows an example of the results of spontaneous potential measurement. To investigate the responsiveness of the fabricated electrode to potassium ions, spontaneous potential was measured in aqueous solutions with different potassium ion concentrations. The horizontal axis represents the logarithm of the potassium ion concentration, and the vertical axis represents the potential. Note E 0 This represents the intercept of the calibration curve at a concentration of 0.01. 【0046】 There was no significant difference in sensitivity or detection limit between the electrode using c-KFeHCF in the comparative example and the electrode using m-KFeHCF in Embodiment 1. On the other hand, the absolute value of the potential was lower in Embodiment 1. This is thought to be because Embodiment 1 has a higher amount of potassium in the crystal and therefore a higher potassium ion activity, resulting in a lower membrane potential. 【0047】 Figure 8 shows the reproducibility data for the spontaneous potential measurement shown in Figure 7. Three electrodes with the same structure (shown as #1 to #3) were fabricated, and spontaneous potential measurements were performed on each. 【0048】 Figure 9 shows an example of the results of a long-term stability test. The test was conducted with the following configuration, and the potential change of the working electrode relative to the reference electrode was measured. Working electrode… Potassium ion selective electrode Reference electrode...Ag / AgCl (saturated KCl) Measurement solution…10 -2 M KCl aqueous solution Measurement temperature…room temperature 【0049】 In Figure 9, the horizontal axis represents time (days), and the vertical axis represents potential. Figure 9(a) shows the measurement results for the comparative example and Embodiment 1. The electrode using c-KFeHCF in the comparative example had the worst long-term stability. This is thought to be because the potential curve is slope-shaped, as shown in Figure 6(a), resulting in large potential fluctuations when compositional changes occur. 【0050】 As electrodes using m-KFeHCF according to Embodiment 1, measurements were performed using two types of electrodes: one in which the Prussian blue analog was oxidized at room temperature in the slurry manufacturing process, and another in which the Prussian blue analog was electrochemically oxidized in the slurry manufacturing process. For the electrochemically oxidized electrode, the potential was maintained at the redox potential of K2FeFe in an aqueous K2SO4 solution. By maintaining the potential in this way, the amount of potassium in the crystal can be adjusted, further improving long-term stability. 【0051】 When oxidized at room temperature, the potential curve exhibits a flat region, as shown in Figure 6(b), resulting in small potential fluctuations during compositional changes and high stability. Furthermore, when electrochemically oxidized, the flat region characteristic in Figure 6(b) is even more pronounced, exhibiting the highest long-term stability. 【0052】 Figure 9(b) shows the reproducibility data for the sample oxidized at room temperature in the first embodiment. Three electrodes with the same structure were fabricated, and long-term stability tests were performed on each. 【0053】 As shown in Figure 9(a), the electrode of the comparative example showed a potential fluctuation of about 20 mV on the 6th day, but as shown in Figures 9(a) and (b), the electrodes of Embodiment 1 all showed a potential fluctuation of about 10 mV or less on the 6th day. 【0054】 Thus, the all-solid-state potassium ion selective electrode according to Embodiment 1 uses K2FeFe, which is considered to be a two-phase coexistence of Prussian blue and Prussian white, as the active material, thereby suppressing potential fluctuations to about 10 mV or less, and improving the long-term stability of the electrode. 【0055】 Figure 10 shows an example of the results of a polarization test using chronopotentiometry. The test was performed with the following configuration. Working electrode… Potassium ion selective electrode Opposite pole…Pt wire Reference electrode...Ag / AgCl (saturated KCl) Electrolyte…10 -2M KCl aqueous solution Applied current: ±1nA Measurement temperature…room temperature 【0056】 In Figure 10, the horizontal axis represents time, and the vertical axis represents electric potential. The direction of the current was reversed at time 300s. The results were almost identical in the comparative example and Embodiment 1. 【0057】 Figure 11 shows a Nyquist plot as an example of the results of an AC impedance measurement test. In Figure 11, the horizontal axis represents the real part of the impedance, and the vertical axis represents the imaginary part. The test was performed with the following configuration. Working electrode… Potassium ion selective electrode Opposite pole…Pt wire Reference electrode...Ag / AgCl (saturated KCl) Electrolyte…10 -2 M KCl aqueous solution Amplitude…100mV Frequency: 100kHz~10mHz Measurement temperature…room temperature 【0058】 The results were almost the same in the comparative example and Embodiment 1, although Embodiment 1 showed slightly lower resistance. This is thought to be due to the smaller particle size, as shown in Figure 4. 【0059】 As described above, the all-solid-state potassium ion selective electrode and its manufacturing method according to Embodiment 1 can further enhance the stability of the potassium ion selective electrode. 【0060】 Figure 12 shows an example of how to use the ion-selective electrode 10. The ion-selective electrode 10 and the reference electrode 11 are immersed in the test solution 12. The ion-selective electrode 10 and the reference electrode 11 are electrically connected via a voltage measuring device 13. The voltage measuring device 13 measures the potential difference between the ion-selective electrode 10 and the reference electrode 11 and outputs a signal representing the potential difference. Since the measured potential difference changes depending on the concentration of potassium ions contained in the test solution 12, the concentration of potassium ions can be calculated based on the potential difference. 【0061】 [Embodiment 2] Embodiment 2 is a modification of Embodiment 1 in which the specific configuration of the ion-selective electrode is changed. Hereafter, descriptions of parts common to Embodiment 1 may be omitted. 【0062】 Figure 13 shows the configuration of the electrode device 30 according to Embodiment 2. The electrode device 30 comprises a substrate 21, an ion-selective electrode 20, and a reference electrode 11. The substrate 21 is made of, for example, alumina. The ion-selective electrode 20 and the reference electrode 11 are formed on the substrate 21. 【0063】 The ion-selective electrode 20 is an all-solid-state potassium ion-selective electrode and has the same configuration as the ion-selective electrode 10 of Embodiment 1 (except that the insulating part is a substrate 21 instead of epoxy resin 5). Furthermore, the ion-selective electrode 20 can be manufactured using the same manufacturing method as the ion-selective electrode 10 of Embodiment 1. 【0064】 A pair of connection portions 22 are formed on the substrate 21. The pair of connection portions 22 are connected to the ion-selective electrode 20 and the reference electrode 11, respectively, via a conductor 23. A portion of the surface of the substrate 21, including the area where the conductor 23 is formed, is covered with a protective film 24 (transparently shown by dashed lines) made of an insulator such as epoxy. The ion-selective electrode 20 and the reference electrode 11 are not covered by the protective film 24, nor are the connection portions 22 (at least a portion of them) covered by the protective film 24. 【0065】 Figure 14 shows an example of how to use the electrode device 30. The ion-selective electrode 20 and the reference electrode 11 are immersed in the test solution 12. The ion-selective electrode 20 and the reference electrode 11 are electrically connected via the voltage measuring device 13. The voltage measuring device 13 measures the potential difference between the ion-selective electrode 20 and the reference electrode 11 and outputs a signal representing the potential difference. Since the measured potential difference changes depending on the concentration of potassium ions contained in the test solution 12, the concentration of potassium ions can be calculated based on the potential difference. 【0066】 The all-solid-state potassium ion selective electrode according to Embodiment 2 has the same configuration as Embodiment 1 and is manufactured by the same manufacturing method, so, as in the embodiment, the stability of the potassium ion selective electrode can be further enhanced. [Explanation of symbols] 【0067】 1…Potassium ion-sensitive membrane 2… Insertion materials 3…Platinum electrode (conductor) 4…Copper wiring 5…Epoxy resin 10…Ion-selective electrodes (all-solid-state potassium ion-selective electrodes) 11...Reference electrode 12...Test liquid 13…Voltage measuring device 20…Ion-selective electrodes (all-solid-state potassium-ion selective electrodes) 21… Circuit board 22...Connection part 23…Conductor 24...Protective film 30...Electrode device

Claims

[Claim 1] A conductor and An insertion material formed on the surface of the conductor, A potassium ion-sensitive film covering the insertion material, Equipped with, The insertion material is a mixed material containing Prussian blue analog particles and conductive material particles. The aforementioned Prussian blue analog particles have structural formula K ｘ Fe[Fe(CN) ６ ] ｙ nH ２ Represented by O, The aforementioned Prussian blue analog particles have a monoclinic crystal structure in at least part of them. x is a number between 1.5 and 2 (inclusive), y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0. All-solid-state potassium ion selective electrode. [Claim 2] A conductor and An insertion material formed on the surface of the conductor, A potassium ion-sensitive film covering the insertion material, A method for manufacturing an all-solid-state potassium ion selective electrode, comprising: The insertion material is a mixed material containing Prussian blue analog particles and conductive material particles. The aforementioned Prussian blue analog particles have structural formula K ｘ Fe[Fe(CN) ６ ] ｙ nH ２ Represented by O, The aforementioned Prussian blue analog particles have a monoclinic crystal structure in at least part of them. x is a number between 1.5 and 2 (inclusive), y is a number greater than 0 and less than or equal to 1, and n is a number greater than or equal to 0. The aforementioned method, A step of supplying a slurry onto a conductor and drying the slurry to form a composite film on the surface of the conductor, Immerse the composite agent film in a first potassium chloride aqueous solution to make the distribution of K in the Prussian blue analog uniform, thereby forming an insertion material on the surface of the conductor; ＋ and a step of forming an insertion material on the surface of the conductor; The process involves supplying a potassium ion-sensitive film stock solution to the surface of the insertion material and drying the potassium ion-sensitive film stock solution to form an ion-sensitive film on the surface of the insertion material. The process involves immersing the ion-sensitive raw material membrane in a second potassium chloride aqueous solution to form a potassium ion-sensitive film on the surface of the insertion material, A method for manufacturing an all-solid-state potassium ion selective electrode, comprising the following: [Claim 3] The method comprises a step of manufacturing the slurry, The process for producing the slurry includes a step of synthesizing Prussian blue analog particles containing at least a portion of a cubic crystal structure by oxidizing a monoclinic Prussian blue analog. The method according to claim 2. [Claim 4] The above method involves, after the step of forming the potassium ion sensitive film, the electrode being K ２ SO ４ K in aqueous solution ２ The method according to claim 2 or 3, comprising the step of maintaining the potential at the redox potential of FeFe. [Claim 5] The method comprises a step of manufacturing the slurry, The process for manufacturing the slurry is as follows: Prussian blue analog particles and, Acetylene black or Ketjen black or multi-walled carbon nanotubes, Polyvinylidene fluoride and The method according to claim 2 or 3, comprising the step of mixing the following.

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