Quick-response ion selective liquid membrane electrode and preparation method thereof

Abstract

The invention discloses a quick-response ion selective liquid membrane electrode and a preparation method thereof. The ion selective liquid membrane electrode comprises a substrate electrode layer, the liquid film transduction and ion recognition functional layer comprises an ion selective film component and an electronegative two-dimensional conductive material doped in the ion selective film component, and the liquid film transduction and ion recognition functional layer is formed on the substrate electrode layer. The ion selective liquid membrane electrode achieves the purpose of high-sensitivity, high-stability, rapid and low-cost detection of electrolyte ions through electronegative two-dimensional conductive material doping and structure regulation and control, and can be applied to the field of ion concentration detection.

Description

Technical Field

[0001] The invention relates to the field of materials, and in particular to a fast-response ion-selective liquid membrane electrode and a preparation method thereof. Background Art

[0002] Ion Selective Electrode (ISE) is an electrochemical sensor, also known as membrane electrode, with a special electrode membrane (called sensitive membrane), which measures ion concentration by the selective response of the electrode membrane to specific ions. The ion carriers on the sensitive membrane cause changes in electrode potential by complexing with specific ions. For ions of different types and concentrations, the responsiveness of the ion selective electrode is different, and the changes in electrode potential produced are different, and the potential difference with the reference electrode is different, so the activity of a specific ion in the solution can be calculated by the electromotive force of the ion selective electrode relative to the reference electrode.

[0003] According to the different target ions, ion selective electrodes can be divided into hydrogen ion electrodes (pH glass electrodes), potassium ion electrodes, sodium ion electrodes, chloride ion electrodes, etc.; according to the different forms of sensitive membranes, ion selective electrodes can be divided into solid membrane electrodes, liquid membrane electrodes, composite membrane electrodes, etc. However, no matter which type of electrode, it has the advantages of high selectivity, rapid response, and easy operation, so it can be widely used in various fields. In environmental monitoring, it can be used to detect heavy metal ions in water bodies, such as lead, cadmium, mercury, etc.; in medical diagnosis, it can be used to measure the concentration of sodium, potassium, calcium and other ions in blood and sweat; in industrial production, it can be used to monitor the concentration of key ions in the production process.

[0004] The technical indicators of ion selective electrodes mainly include the following aspects.

[0005] Slope: According to the Nernst equation of the ion selective electrode, the electrode potential is linearly related to the logarithm of the ion activity, which is called the Nernst response. Within the linear response range, the change in the electrode potential when the slope S changes by 10 times the activity of the ion to be measured is called the step difference (mV / pa). At 25°C, S = 59.16mV / pa for monovalent ions and S = 28.58mV / pa for divalent ions. The actual response slope of the ion selective electrode often deviates from the theoretical value.

[0006] Linear response range: Ion selective electrodes have a wide linear response range, usually several orders of magnitude. The general electrode response range is 10 -1 ~10 -5 M, individual electrodes can reach 10 -7 M. The linear response range of the electrode is the basis of quantitative analysis, and a wide linear response range means that a wider range of ion activities can be detected.

[0007] Selectivity: When an ion selective electrode responds to a specific ion, it will be interfered by other ions. The selectivity coefficient K ij To express the degree of this interference, K ij The smaller the value, the higher the selectivity of the electrode for a specific ion. ij Value is 10 -3 The following indicates good selectivity.

[0008] Response time: The response time of an ion selective electrode reflects the response speed. It is generally measured by the immersion method. The measured response time refers to the time from the electrode contacting the solution to reaching the stable potential value (±1 millivolt). Generally, solid-state electrodes respond faster, as fast as a few milliseconds; liquid membrane electrodes respond slower, usually from a few seconds to a few minutes.

[0009] Stability: The stability of an ion-selective electrode refers to the change in the electrode potential over time in a test solution with a certain composition and temperature. The reference electrode potential is relatively stable, and the potential drift inside and outside the sensitive membrane causes a slight shift in the electrode standard potential. -3 The potential drift in the test solution is taken as the standard deviation. The smaller the potential drift, the better the electrode stability.

[0010] In ion-selective electrodes, the sensitive membrane is the part that recognizes and binds to specific types of ions. It is the most important component of ion-selective electrodes, and the core of the sensitive membrane lies in the selection of ion carriers. Ion carriers form charged complexes through exchange and complexation with specific ions, causing the membrane potential to change and generating response signals. For solid-state membrane electrodes, the solid-state transduction layer between the sensitive membrane and the conductive substrate converts ion signals into electrochemical signal outputs, playing an important mediating role, thereby improving the stability and response speed of ion-selective electrodes. For liquid membrane electrodes, the carrier can move freely in the liquid membrane, just like forming an ion channel to be tested to complete charge transfer, so the liquid membrane itself also plays the role of a transduction layer. However, the response time, response speed, sensitivity, stability and other aspects of existing liquid membrane electrodes need to be further improved.

[0011] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0012] In order to make up for the deficiencies of the prior art, the present invention provides a fast-response ion-selective liquid membrane electrode and a preparation method thereof.

[0013] The present invention adopts the following technical solution:

[0014] In the first aspect, a fast-response ion-selective liquid membrane electrode is provided, comprising a base electrode layer; a liquid membrane transduction and ion recognition functional layer, the liquid membrane transduction and ion recognition functional layer comprising an ion selective membrane component and a negatively charged two-dimensional conductive material doped in the ion selective membrane component, the liquid membrane transduction and ion recognition functional layer being formed on the base electrode layer.

[0015] In the second aspect, a method for preparing the ion-selective liquid membrane electrode described in the first aspect is provided, which comprises the following steps: S1, mixing a dispersion of a negatively charged two-dimensional conductive material with the ion-selective membrane component to obtain an ion-selective membrane solution; S2, forming the ion-selective membrane solution on the base electrode layer to obtain the ion-selective liquid membrane electrode.

[0016] The present invention has the following beneficial effects: The present invention provides a fast-response ion-selective liquid membrane electrode and a preparation method thereof. The ion-selective electrode achieves the purpose of high-sensitivity, high-stability, rapid and low-cost detection of electrolyte ions by doping and structural regulation of negatively charged two-dimensional conductive materials, and can be applied to the field of ion concentration detection. The ion-selective liquid membrane electrode of the present invention can achieve high sensitivity, short response time and high stability in the field of ion concentration monitoring, effectively solving the problems of long response time and poor stability of traditional ion-selective liquid membrane electrodes. At the same time, negatively charged two-dimensional conductive materials are unprecedentedly added to the ion-selective membrane to achieve repeatable ultra-high sensitive response. Based on the above optimization and expansion of the existing structure, the present invention can achieve high-sensitivity and rapid detection of a variety of positively charged electrolyte ions, and provide faster and more accurate results for detecting the concentration level and change of each electrolyte ion in the liquid components of the human body, thereby providing precise assistance for the real-time monitoring of human health data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the preparation of an ion-selective liquid membrane electrode (MX-ISE) in a specific embodiment of the present invention;

[0018] Figure 2 MX-Na prepared in Example 1 of the present invention + Open circuit potential-time cycle test diagram of ISE for different concentrations of NaCl solution;

[0019] Figure 3 MX-Na prepared in Example 1 of the present invention + Linear relationship curve between open circuit potential and logarithm of concentration of ISE for NaCl solutions of different concentrations;

[0020] Figure 4 MX-Na prepared in Example 1 of the present invention + ISE at 10 -5 -10-1 Open circuit potential-time cycle test diagram under a wide mM NaCl concentration range;

[0021] Figure 5 MX-Na prepared in Example 1 of the present invention + Open circuit potential-time cycle test diagram of ISE for different concentrations of NaCl solution after preparation and first test 336h;

[0022] Figure 6 MX-Na prepared in Example 1 of the present invention + ISE for Na + And the open circuit potential-time test diagram of each interfering ion;

[0023] Figure 7 MX-K prepared in Example 2 of the present invention + Open circuit potential-time cycle test diagram of ISE for different concentrations of KCl solution. DETAILED DESCRIPTION

[0024] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention. In the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0025] A specific embodiment of the present invention provides a fast-response ion-selective liquid membrane electrode, which includes: a base electrode layer; a liquid membrane transduction and ion recognition functional layer, which contains an ion-selective membrane component and a negatively charged two-dimensional conductive material doped in the ion-selective membrane component, and the liquid membrane transduction and ion recognition functional layer is formed on the base electrode layer and exposed to an electrolyte liquid environment when used.

[0026] The ion-selective liquid membrane electrode is an electrochemical sensing membrane with a sandwich-like structure. The liquid membrane transduction function in the liquid membrane transduction and ion recognition functional layers can build a charge transfer path between the charge functional layer and the base electrode layer. The ion recognition function can change the electrode potential of the device. The base electrode layer receives electrical signals and outputs potential changes. The thickness of the ion-selective liquid membrane electrode is micrometer-level, and it can produce voltage changes for certain ion concentration signals, realizing highly sensitive detection of specific ion concentrations in the solution.

[0027] In some embodiments, the base electrode layer is one of a gold base electrode layer, a platinum electrode layer, a glassy carbon electrode layer, and a graphite electrode layer.

[0028] In some embodiments, the base electrode layer is a gold base electrode layer, which includes a silicon base and a gold layer formed on the silicon base; the thickness of the gold layer is 50-500 nm; and the thickness of the silicon base is 100-1000 μm.

[0029] In some embodiments, the negatively charged two-dimensional conductive material is one of MXene, graphene, and graphene oxide; the mass fraction of the negatively charged two-dimensional conductive material in the liquid film transduction and ion recognition functional layer is 1%-10%; preferably, the MXene is one of TiVC, Ti3CN, V2C, Mo2Ti2C3, Nb2C, and Ti3C2. Further preferably, the liquid film transduction and ion recognition functional layer is doped with titanium carbide (Ti3C2) MXene.

[0030] In some embodiments, the ion selective membrane composition includes the following components in mass percentage: ion carrier: 0.5-5wt%; ion additive: 0.1-2wt%; polymer matrix: 20-50wt%; plasticizer: 45-75wt%. The ion carrier interacts with the ion to be detected through coordination bonds to form a charged complex, and moves freely in the liquid membrane to form an ion channel to be detected to complete the transfer of charge.

[0031] In some embodiments, the ion carrier is one of a potassium ion carrier and a sodium ion carrier.

[0032] In some embodiments, the potassium ion carrier is one of valinomycin, bis[(benzo-15-crown-4)-4'-ylmethyl] heptanoate, 2-dodecyl-2-methyl-1,3-propanediylbis[N-[5'-nitro(benzo-15-crown-5)-4'-yl]carbamate], and the sodium ion carrier is one of 4-tert-butylcalix[4]arene-tetraethyltetraacetate, N,N'-dibenzyl-N,N'-diphenyl-1,2-benzenedioxydiethylamide, and N,N,N',N'-tetracyclohexyl-1,2-benzenedioxydiethylamide.

[0033] In some embodiments, the thickness of the liquid membrane transduction and ion recognition functional layer is 10-1000 μm.

[0034] The specific embodiment of the present invention also provides a method for preparing the ion-selective liquid membrane electrode (MX-ISE), which comprises the following steps:

[0035] S1, mixing a dispersion of a negatively charged two-dimensional conductive material with the ion selective membrane component to obtain an ion selective membrane solution;

[0036] S2. Forming the ion selective membrane solution on the base electrode layer to obtain the ion selective liquid membrane electrode.

[0037] In some embodiments, the method for preparing the ion-selective liquid membrane electrode comprises the following steps:

[0038] (1) using thermal evaporation technology, electron beam evaporation technology or magnetron sputtering technology to plate a layer of gold film on a silicon wafer with a thickness of 100-1000 μm to obtain a gold base electrode layer, wherein the thickness of the gold layer is 50-500 nm;

[0039] (2) preparing a dispersion of a negatively charged two-dimensional conductive material, wherein the mass fraction of the negatively charged two-dimensional conductive material in the dispersion is 0.1-5%; wherein the solvent used in the dispersion is a volatile solvent, such as tetrahydrofuran or cyclohexanone;

[0040] (3) Weighing 0.5-5.0 mg of ion carrier, 0.1-2.0 mg of ion additive, 20.0-50.0 mg of polymer matrix, and 45.0-75.0 mg of plasticizer into a centrifuge tube, adding 500-5000 μL of the dispersion obtained in step (2) dropwise, and shaking for 0.5-1 h to form a uniform dispersion to obtain an ion selective membrane solution;

[0041] (4) Take 10-1000 μL of the ion selective membrane solution and evenly drop or spin coat it on the gold base electrode layer to evaporate the solvent in the ion selective membrane solution to obtain a liquid membrane transduction and ion recognition functional layer with a thickness of 10-1000 μm, and attach it to the gold base electrode layer to obtain the ion selective liquid membrane electrode.

[0042] like Figure 1 As shown, in an example using titanium carbide (Ti3C2) MXene as a negatively charged two-dimensional conductive material, the preparation method of the ion-selective liquid membrane electrode includes the following steps:

[0043] (1) Preparing a gold base electrode layer: A gold film is plated on a silicon wafer with a thickness of 100-1000 μm using thermal evaporation technology, electron beam evaporation technology or magnetron sputtering technology to obtain a gold base electrode layer, wherein the thickness of the gold layer is 50-500 nm. Furthermore, the size of the gold-plated electrode is 1-4 cm in length and 0.5-2 cm in width.

[0044] (2) Preparation of tetrahydrofuran dispersion of MXene:

[0045] (2.1) Add 15-30 mL of concentrated hydrochloric acid to 5-10 mL of deionized water and stir for 5-10 min to dilute to obtain 9 mol / L hydrochloric acid, weigh 1.6-3.2 g of LiF and slowly add it to 9 mol / L hydrochloric acid, stir for 10-15 min to obtain a hydrofluoric acid etching solution; weigh 1.0-2.0 g of titanium aluminum carbide (Ti3AlC2) MAX raw material, slowly add it to the hydrofluoric acid etching solution in batches in small amounts for 5-10 min, react in a 30-50 ° C water bath for 12-48 h, and etch to obtain a mixed solution containing the product titanium carbide (Ti3C2) MXene;

[0046] (2.2) Collect the obtained mixed solution containing MXene product, add deionized water for washing, centrifuge at 3500-7000 rpm for 5-10 min multiple times, collect the lower precipitate and discard the supernatant, wash and centrifuge repeatedly until the pH of the solution is neutral;

[0047] (2.3) Collect the neutral lower precipitate and add 150-250 mL of deionized water to disperse it. Ultrasonicate at 15-25° C. for 30-60 min. Centrifuge the obtained ultrasonic dispersion at 3500-7000 rpm for 15-60 min. Collect the upper black liquid as the product MXene. Freeze-dry for 12-48 h to obtain MXene flaky solid. Store the MXene flaky solid in a cool and dry place isolated from air for future use.

[0048] (2.4) Weigh 5-50 mg of MXene flake solid and add it to a centrifuge tube, take 1-5 mL of tetrahydrofuran (THF) liquid and add it to the centrifuge tube, ultrasonicate for 30-60 min and oscillate at 15-25 °C to obtain a tetrahydrofuran (THF) dispersion with a MXene mass fraction of 0.1-5%;

[0049] (3) preparing an ion selective membrane solution: weighing 0.5-5.0 mg of an ion carrier (e.g., valinomycin or 4-tert-butylcalix[4]arene-tetraethyl acetate), 0.1-2.0 mg of an ion additive (e.g., potassium tetrakis(4-chlorophenyl)borate), 20.0-50.0 mg of a polymer matrix (e.g., high molecular weight polyvinyl chloride), and 45.0-75.0 mg of a plasticizer (e.g., 2-nitrophenyl octyl ether) into a centrifuge tube, adding 500-5000 μL of a THF dispersion containing MXene dropwise, and shaking for 0.5-1 h until a uniform dispersion is formed to obtain an ion selective membrane solution;

[0050] (4) Preparation of ion-selective liquid membrane electrode: 10-1000 μL of ion-selective membrane solution is uniformly drop-coated or spin-coated on the gold base electrode layer (for example, drop-coated on a 1 cm×1 cm square area at the end of the evaporated gold electrode), tetrahydrofuran is evaporated at 4-25°C for 2-12 h, and a liquid membrane transduction and ion recognition functional layer with a thickness of 10-1000 μm is obtained, and attached to the gold base electrode layer (for example, an area of ​​1 cm 2 , a square liquid membrane transduction and ion recognition functional layer with a thickness of 10-1000 μm) to obtain the ion-selective liquid membrane electrode (MX-ISE).

[0051] Further, taking sodium ion carrier or potassium ion carrier as an example, the following steps are also included:

[0052] (5) The prepared ion-selective liquid membrane electrode (MX-ISE) was connected to an alligator clip to form a three-electrode system with a platinum counter electrode, silver / silver chloride or saturated calomel reference electrode. The three-electrode system was used to measure 10 -5 -Open circuit potential corresponding to sodium chloride / potassium chloride solutions in the concentration range of 1 mol / L.

[0053] (6) The open circuit potential-time curve (OCP-t diagram) of the ion-selective liquid membrane electrode (MX-ISE) was plotted with time as the horizontal axis instead of concentration (one concentration gradient per 50 s) and open circuit potential as the vertical axis. The open circuit potential-concentration relationship curve of the electrode was plotted with ion concentration as the horizontal axis and the open circuit potential corresponding to each concentration as the vertical axis. The least squares method was used for linear regression to evaluate its accuracy, sensitivity, linear response range, response time and other parameters.

[0054] The specific embodiments of the present invention are further described below.

[0055] Example 1

[0056] The embodiment of the present invention includes the following steps:

[0057] (1) A gold film is deposited on a silicon wafer with a thickness of 1000 μm by electron beam evaporation technology to obtain a gold base electrode layer. The thickness of the gold layer is 100 nm. The length of the gold base electrode layer is 2 cm and the width is 1 cm.

[0058] (2) Add 15 mL of concentrated hydrochloric acid to 5 mL of deionized water and stir for 10 min to dilute to obtain 9 mol / L hydrochloric acid. Weigh 1.6 g of LiF and slowly add it to 9 mol / L hydrochloric acid and stir for 10 min to obtain a hydrofluoric acid etching solution. Weigh 1.0 g of titanium aluminum carbide (Ti3AlC2) MAX raw material and slowly add it to the hydrofluoric acid etching solution in batches in small amounts for 10 min. React in a 40 ° C water bath for 24 h to etch to obtain a mixed solution containing the product titanium carbide (Ti3C2) MXene.

[0059] (3) The obtained mixed solution containing the MXene product was collected, washed with deionized water, centrifuged at 4000 rpm for 5 min multiple times, the lower precipitate was collected and the supernatant was discarded, and the washing and centrifugation were repeated multiple times until the pH of the solution was neutral.

[0060] (4) Collect the neutral lower precipitate and add 200 mL of deionized water to disperse it. Ultrasonicate it at 20°C for 60 min. Centrifuge the obtained ultrasonic dispersion at 3500 rpm for 60 min, and collect the upper black liquid (i.e., the dispersion of the product MXene). The MXene dispersion is freeze-dried for 36 h to obtain MXene flake solids (MXene nanosheets). Store it in a cool and dry place away from air.

[0061] (5) Weigh 10 mg of MXene flake solid and add it to a centrifuge tube. Use a pipette to transfer 1 mL of tetrahydrofuran (THF) liquid into the centrifuge tube. Ultrasonicate and oscillate at 20°C for 30 min to obtain a THF dispersion with a MXene mass fraction of 1%.

[0062] (6) Weigh 2.0 mg of sodium ion carrier X (4-tert-butylcalix[4]arene-tetraethyltetraacetate), 1.0 mg of potassium tetrakis(4-chlorophenyl)borate, 32.5 mg of high molecular weight polyvinyl chloride (model P815909), and 64.5 mg of 2-nitrophenyl octyl ether into a centrifuge tube, add 660 μL of the above-mentioned tetrahydrofuran dispersion containing MXene, and shake for 0.5 h to form a uniform dispersion to obtain an ion selective membrane solution.

[0063] (7) Take 50 μL of the ion selective membrane solution and evenly apply it on a 1 cm × 1 cm square area at one end of the gold substrate electrode layer. Allow tetrahydrofuran to evaporate at 20 °C for 12 h to obtain a 1 cm square area. 2 , a square ion-selective liquid membrane with a thickness of 50 μm, and attached to the gold substrate electrode layer to obtain a MXene-doped ion-selective liquid membrane electrode (MX-ISE), which can be denoted as MXene Na + ISE, abbreviated as MX-Na + ISE, where the MX-Na+ During ISE, the ion carrier 4-tert-butylcalix[4]arene-tetraethyltetraacetate interacts with the sodium ions to be measured through coordination bonds to form a charged complex, which moves freely in the liquid membrane to form a channel for the sample to be measured to complete the charge transfer.

[0064] (8) The MX-Na prepared above + The ISE was connected to an alligator clip to form a three-electrode system with a platinum counter electrode and a silver / silver chloride reference electrode. This three-electrode system was used to measure 10 -5 -Open circuit potential of sodium chloride solution in the concentration range of 1 mol / L.

[0065] (9) Using time instead of concentration as the horizontal axis (one concentration gradient per 50 s), and open circuit potential as the vertical axis, plot the MX-Na + The open circuit potential-time curve (OCP-t graph) of ISE. Then take the ion concentration as the horizontal axis and the open circuit potential corresponding to each concentration as the vertical axis to draw the open circuit potential-concentration relationship curve of the electrode, and use the least squares method for linear regression to evaluate its accuracy, sensitivity, linear response range, response time and other parameters.

[0066] The test results of this embodiment are as follows Figure 2-6 shown.

[0067] Figure 2 In the experiment, an electrochemical workstation was connected to a three-electrode system, and the open circuit voltage-time (OCP-t) mode was selected to test the sodium ion selective liquid membrane electrode (MX-Na) doped with MXene prepared in the present invention. + ISE) For the open circuit potential of NaCl solution with different concentrations, the NaCl concentration was changed every 50 seconds, and the NaCl concentration range was 2.5-160mmol / L. The operation time was about 10 seconds, without incubation or pre-activation time. The open circuit potential of the system with different concentrations (times) was measured, 3 cycles were performed, and the graph was drawn.

[0068] Figure 3 In, take Figure 2 In any cycle of the test, the logarithm of the concentration (unit: mmol / L) is used as the horizontal coordinate, and the average value of the positive / negative scan process is used as the vertical coordinate of the open circuit potential. A linear regression curve of the open circuit potential-logarithm of the concentration is drawn. The slope is the sensitivity, which can reach 85-100mV / pa. The linear correlation coefficient is 0.9995.

[0069] Figure 4 The NaCl concentration range is 10 -5 -10 -1 mmol / L, repeated Figure 2 Test and evaluate wide range sensing capability and linear response range.

[0070] Figure 5 Repeat 336h after preparation and first test Figure 2 The sensing performance test evaluates electrode stability.

[0071] Figure 6 In the experiment, 100 mmol / L MgCl2, CaCl2, LiCl, KCl, and NH4Cl were used as interfering ion solutions to evaluate the sodium ion selective liquid membrane electrode doped with MXene (MX-Na + ISE) anti-interference performance.

[0072] MXene is a transition metal carbide or nitride, which is prepared by etching the A element (IIIA, IVA group, mostly Al, Si) in the MAX compound. It has a two-dimensional layered structure similar to graphene. MXene is naturally hydrophilic because during the preparation of MXene, due to the etching effect of HF, hydrophilic groups such as -F and -OH are introduced on its surface or edge, which strengthens the interaction with water or other components without changing the conductivity of the material itself, thereby improving compatibility and enhancing the conductivity of the material. The above method combines the liquid film transduction layer doped with MXene and the ion recognition functional layer into one layer on the base electrode layer, while not changing the electrode's selectivity for specific ions (such as Figure 6 As shown), it accelerates the transfer efficiency of electrons on the electrode surface and thus shortens the response time (as shown Figure 2 At the same time, the introduction of negatively charged MXene on the electrode surface strengthens the attraction of positively charged ions, so the electrode has a higher sensitivity to cations (as shown in Figure 3 As shown). The present invention has found in the research that by using MXene as the liquid membrane transduction layer, its good conductivity can be used to form a conductive path to accelerate electron transfer, shorten response time and improve stability. After further research, it was unexpectedly found that after MXene is directly incorporated into the ion recognition functional layer (including ion selective membrane components), the negative charge of MXene itself can be used to improve the recognition sensitivity of cations without affecting the selectivity, so that the embodiment of the present invention achieves the purpose of high sensitivity, high stability, rapid and low cost detection of electrolyte ions.

[0073] Example 2

[0074] The difference from Example 1 is that the sodium ion carrier is replaced by the potassium ion carrier valinomycin. The other steps are the same as in Example 1 to prepare the MXene-doped ion selective liquid membrane electrode (MX-ISE), which can be denoted as MXene K + ISE, abbreviated as MX-K + ISE. Figure 7 The figure shows a potassium ion selective liquid membrane electrode (MX-K) doped with MXene. +The open circuit potential of ISE for different concentrations of KCl solutions, the KCl concentration range is 0.5-32mmol / L.

[0075] The method of the present invention is based on an ion-selective liquid membrane electrode. Ions are identified and bound by ion carriers in the electrode membrane component that have a complexing ability for specific ions. Different ion concentrations result in different electrode surface potentials after binding, so the concentration of specific ions can be determined based on the open circuit potential of the ion-selective electrode and the reference electrode. Compared with traditional ion-selective liquid membrane electrodes, the embodiment of the present invention dopes MXene with excellent conductive properties in the electrode component, increases the conductive path between the solid-liquid contact layer and the metal electrode surface of the ion-selective electrode, accelerates charge transfer, and thus shortens the response time of the electrode to ions. At the same time, the MXene with negative charge on the surface enhances the binding ability of the ion-selective liquid membrane with positively charged ions through electrostatic action, thereby improving the sensitivity of the electrode.

[0076] Compared with the prior art, the present invention realizes the direct doping of negatively charged two-dimensional conductive materials for the first time, which provides abundant conductive pathways for the membrane electrode as an electrochemical functional layer, greatly improving the efficiency and stability of charge transfer. The membrane electrode exhibits good electrochemical stability and extremely fast response time, solving the problems of slow response time and long pre-activation time required before use of existing ion-selective electrodes.

[0077] In the above embodiment, as a two-dimensional material with a negative charge on the surface, the doping of MXene makes MX-ISE have a higher affinity for positively charged ions (such as sodium ions and potassium ions), accelerates the enrichment of positive ions to the electrode surface and enhances the binding of positive ions to the electrode surface, so that the ion selective electrode disclosed in the present invention has a shorter response time and higher sensitivity, and the slope can reach 85-100mV / pa.

[0078] Compared with the prior art, the MXene-doped ion selective liquid membrane electrode (MX-ISE) disclosed in the embodiment of the present invention does not require the aid of large-scale experimental equipment, is easy to operate, and has obvious effects: the MXene-doped ion selective electrode is used as an electrochemical sensitive element in 10 -4 -10 -1 It has extremely high linear responsiveness in a wide range of mol / L, and the linear correlation coefficient can reach 0.999. While shortening the response time and having a wide linear response range, the stability of the ion selective electrode is improved, and it still has high linear response capability 14 days after preparation.

[0079] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A fast-response ion-selective liquid membrane electrode, characterized in that: include: Base electrode layer; The liquid membrane transduction and ion recognition functional layer comprises an ion selective membrane component and a negatively charged two-dimensional conductive material doped in the ion selective membrane component. The liquid membrane transduction and ion recognition functional layer is formed on the base electrode layer.

2. The ion-selective liquid membrane electrode according to claim 1, characterized in that: The base electrode layer is one of a gold base electrode layer, a platinum electrode layer, a glassy carbon electrode layer, and a graphite electrode layer.

3. The ion-selective liquid membrane electrode according to claim 2, characterized in that: The substrate electrode layer is a gold substrate electrode layer, which comprises a silicon substrate and a gold layer formed on the silicon substrate; the thickness of the gold layer is 50-500 nm; the thickness of the silicon substrate is 100-1000 μm.

4. The ion-selective liquid membrane electrode according to claim 1, characterized in that: The negatively charged two-dimensional conductive material is one of MXene, graphene, and graphene oxide; the mass fraction of the negatively charged two-dimensional conductive material in the liquid film transduction and ion recognition functional layer is 1%-10%; preferably, the MXene is one of TiVC, Ti3CN, V2C, Mo2Ti2C3, Nb2C, and Ti3C2.

5. The ion-selective liquid membrane electrode according to claim 1, characterized in that: The ion selective membrane composition includes the following components in mass percentage: Ion carrier: 0.5-5wt%; Ionic additives: 0.1-2wt%; Polymer matrix: 20-50wt%; Plasticizer: 45-75wt%.

6. The ion-selective liquid membrane electrode according to claim 5, characterized in that: The ion carrier is one of a potassium ion carrier and a sodium ion carrier.

7. The ion-selective liquid membrane electrode according to claim 6, characterized in that: The potassium ion carrier is one of valinomycin, bis[(benzo-15-crown-4)-4'-ylmethyl] heptanoate, 2-dodecyl-2-methyl-1,3-propanediyl bis[N-[5'-nitro(benzo-15-crown-5)-4'-yl] carbamate], and the sodium ion carrier is one of 4-tert-butylcalix[4]arene-tetraethyltetraacetate, N,N'-dibenzyl-N,N'-diphenyl-1,2-benzenedioxy diethylamide, and N,N,N',N'-tetracyclohexyl-1,2-benzenedioxy diethylamide.

8. The ion-selective liquid membrane electrode according to claim 1, characterized in that: The thickness of the liquid membrane transduction and ion recognition functional layer is 10-1000 μm.

9. A method for preparing the ion-selective liquid membrane electrode according to any one of claims 1 to 8, characterized in that: The steps include: S1, mixing a dispersion of a negatively charged two-dimensional conductive material with the ion selective membrane component to obtain an ion selective membrane solution; S2. Forming the ion selective membrane solution on the base electrode layer to obtain the ion selective liquid membrane electrode.

10. The method for preparing an ion-selective liquid membrane electrode according to claim 9, characterized in that: The steps include: (1) using thermal evaporation technology, electron beam evaporation technology or magnetron sputtering technology to plate a layer of gold film on a silicon wafer with a thickness of 100-1000 μm to obtain a gold base electrode layer, wherein the thickness of the gold layer is 50-500 nm; (2) preparing a dispersion of a negatively charged two-dimensional conductive material, wherein the mass fraction of the negatively charged two-dimensional conductive material in the dispersion is 0.1-5%; (3) Weighing 0.5-5.0 mg of ion carrier, 0.1-2.0 mg of ion additive, 20.0-50.0 mg of polymer matrix, and 45.0-75.0 mg of plasticizer into a centrifuge tube, adding 500-5000 μL of the dispersion obtained in step (2) dropwise, and shaking for 0.5-1 h to form a uniform dispersion to obtain an ion selective membrane solution; (4) Take 10-1000 μL of the ion selective membrane solution and evenly drop or spin coat it on the gold base electrode layer to evaporate the solvent in the ion selective membrane solution to obtain a liquid membrane transduction and ion recognition functional layer with a thickness of 10-1000 μm, and attach it to the gold base electrode layer to obtain the ion selective liquid membrane electrode.

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