CN102980931B - All-solid-state selective electrode based on functional ion liquid and preparation method of all-solid-state selective electrode - Google Patents

Abstract

The invention discloses a functional ionic liquid-based all-solid-state ion selective electrode and a preparation method thereof. The selective electrode comprises a substrate, an internal reference electrode, a solid-state ion layer and an ion-sensitive membrane. The solid-state ion layer is composed of a functional ionic liquid Composition, the cation of the functional ionic liquid has a redox group, and the anion is a hydrophobic group. The invention utilizes the hydrophobicity and light insensitivity of the functional ionic liquid to reduce the influence of environmental factors such as water layer and light on the all-solid-state ion-selective electrode, thereby improving the operability and stability of the electrode in practical applications.

Description

An all-solid-state ion-selective electrode based on functional ionic liquid and its preparation method

technical field

The invention relates to the technical field of electrochemical sensors, in particular to a functional ionic liquid-based all-solid-state ion-selective electrode and a preparation method thereof.

Background technique

Ion-selective electrode is an indicator electrode for measuring the concentration of certain ions in solution by potentiometric method. It has the characteristics of high sensitivity, good selectivity, wide measurement range, convenient operation, and low cost, so it is widely used in the fields of environment, food, medicine, industry, and biology.

A common ion selective electrode is composed of an ion sensitive membrane, an internal reference electrode and an internal filling liquid. When measuring, the internal reference electrode and the external reference electrode are used to form an ion sensor, and these two electrodes are inserted into the solution to be tested at the same time, and connected with an external measuring device to form an electrochemical cell, and the electromotive force of the electrochemical cell is measured. The ion concentration in the solution to be measured can be calculated according to the Nernst equation. However, the use of filling liquid makes the structure of the electrode complicated, the preparation process is cumbersome, and the electrode cannot be miniaturized and integrated, thus limiting the application of ion-selective electrodes in on-site detection and in vivo monitoring.

The all-solid-state ion-selective electrode removes the liquid-filled layer in the traditional ion-selective electrode and replaces it with a solid-state intermediate layer. When the electrode is made, the solid intermediate layer is sandwiched between the internal reference electrode and the ion-sensitive membrane, which plays the role of signal transduction, that is, the ion signal in the ion-sensitive membrane is converted into an electronic signal on the electrode conductor. The preparation process of this electrode is very simple, easy to miniaturize, and has the same potential analysis performance as the traditional ion-selective electrode. In such ion-selective electrodes, the choice of solid interlayer is critical. In the existing literature reports, self-assembled monolayers, conductive polymers, carbon nanomaterials, and gold nanomaterials have been used as solid-state interlayers for the development of all-solid-state ion-selective electrodes.

Ionic liquid is a kind of green reagent, the structure is composed of positive and negative ions, it has high ionic conductivity, good physical and chemical stability, wide electrochemical window, stable electrochemical properties, good biocompatibility Features. At the same time, the performance of ionic liquids is adjustable, that is, the composition of its anions and cations can be designed and its substituents can be changed according to needs, thereby changing its performance. Functional ionic liquids are ionic liquids with special functional groups or substituents designed for a certain performance or application. Therefore, some ionic liquids with special properties can be designed to serve as solid-state interlayers for the development of all-solid-state ion-selective electrodes.

The literature (Cecylia Wardak.A highly selective lead-sensitive electrode with solid contact based on ionic liquid.Journal of Hazardous Materials 186(2011)1131-1135) reported a lead ion selective electrode based on ionic liquid. A mixture of liquid and polymer-polyvinyl chloride acts as a solid intermediate layer. The ionic liquids used are just some ionic liquids that are insoluble in water but soluble in tetrahydrofuran solvents, and act as a binder inside. Due to no redox activity, the The solid intermediate layer cannot effectively transmit the membrane potential signal, which is not conducive to the stable operation of the ion-selective electrode.

Patent CN101852761A discloses an all-solid sodium ion selective electrode, including a substrate, an electrode base system, a solid electrolyte layer, a sodium ion sensitive film and an insulating layer. The conductive lead wire of two electrodes is composed of the solid electrolyte layer on the reaction electrode, the solid electrolyte layer is covered with a sodium ion sensitive film, the insulating layer surrounds the sodium ion sensitive film, and is provided with an opening for exposing the sodium ion sensitive film. The solid electrolyte layer of the selective electrode disclosed in the patent is composed of a conductive polymer, and a water layer is prone to appear in the electrode film, and is easily disturbed by dissolved oxygen, and the stability of the electrode is poor.

Contents of the invention

The invention provides an all-solid-state ion selective electrode based on functional ionic liquid, which solves the problem of poor stability and repeatability of the existing selective electrode.

An all-solid-state ion-selective electrode based on a functional ionic liquid, comprising a substrate, an internal reference electrode, a solid-state ionic layer, and an ion-sensitive membrane, the solid-state ionic layer is composed of a functional ionic liquid, and the cations of the functional ionic liquid have redox properties group, anion is a hydrophobic group.

The anion of the functional ionic liquid of the present invention has strong hydrophobicity, and the cation has a redox group, so that the functional ionic liquid has hydrophobicity and light insensitivity, can reduce the influence of water layer, light, etc. on the all-solid-state ion selective electrode, and improve the electrode performance. Operability and stability in practical applications.

Preferably, the cation is trimethylanilinium ion, N-methyltetrahydrothiophene ion or 1-ethylferrocenyl-3 methylimidazolium ion; the anion is hexafluorophosphate ion, bistrifluoro Methanesulfonylimide ion.

The functional ionic liquid is insoluble in water and is solid at room temperature, most preferably trimethylaniline hexafluorophosphate, N-methyltetrahydrothiophene bistrifluoromethanesulfonyl imide salt, or 1-ethyl dichloromethane Iron-3-methylimidazolium hexafluorophosphate.

In order to ensure that the solid-state ion layer plays a good role in signal conversion in the electrode, the thickness of the solid-state ion layer is preferably 1-5 μm, most preferably 3 μm.

The all-solid-state ion-selective electrode of the present invention can detect cations and anions, such as potassium ions, sodium ions, calcium ions, chloride ions, nitrate ions, sulfate ions, etc. membrane, calcium ion sensitive membrane, chloride ion sensitive membrane, nitrate ion sensitive membrane, sulfate ion sensitive membrane, etc.

The internal reference electrode is arranged on the substrate, the solid-state ion layer is arranged above the internal reference electrode, and the ion-sensitive film is covered on the solid-state ion layer. Generally, the all-solid-state ion-selective electrode also includes an electrode connected to the internal reference electrode Lead wire, when in use, the movable end of the electrode lead wire is connected with the external reference electrode. The electrode leads are generally copper wires.

Preferably, the reference electrode is a gold electrode, a platinum electrode or a carbon electrode, all of which are commonly used electrodes.

The substrate is made of organic polymer materials, such as PE, PVC and the like.

The present invention also provides the preparation method of the all-solid-state ion-selective electrode based on the functional ionic liquid, comprising the following steps:

An internal reference electrode is set on the substrate; the functional ionic liquid solution is uniformly drip-coated on the surface of the internal reference electrode, and the solvent is dried and evaporated to obtain a solid ion layer; the ion-sensitive membrane solution is drip-coated on the surface of the solid ion layer, and dried to obtain an ion layer. Sensitive membrane; the functional ionic liquid is a solid ionic liquid at room temperature, the cation has a redox group, and the anion is a hydrophobic group.

Before setting the reference electrode, the surface of the internal reference electrode and the substrate can be pretreated with absolute ethanol to remove the floating dust on the surface, so that the surface is clean, consistent and fully dry.

The solvent selected for the functional ionic liquid solution is an organic solvent, such as acetone.

The ion-sensitive membrane solution is prepared by conventional methods, generally by uniformly mixing ionophores, polymers (PVC, etc.), plasticizers, lipophilic macromolecules, and solvents.

Compared with prior art, the beneficial effects of the present invention are:

In the present invention, the ionic liquid with special functions is introduced into the all-solid-state ion-selective electrode as a signal transduction layer, and the ion signal in the ion-sensitive membrane is converted into an electronic signal by utilizing the high ion conductivity and electron conductivity of the functional ionic liquid , and transmit the electronic signal to the electrode substrate to realize the transmission of the electrode response signal, and eliminate the problem of unstable potential response caused by the signal transmission blocking layer existing in the traditional all-solid-state ion-selective electrode.

The invention utilizes the hydrophobicity and light insensitivity of the functional ionic liquid to reduce the influence of environmental factors such as water layer and light on the all-solid-state ion-selective electrode, thereby improving the operability and stability of the electrode in practical applications.

Description of drawings

Fig. 1 is the structural representation of electrode of the present invention;

Fig. 2 is the potential response calibration curve of the all-solid-state potassium ion selective electrode based on trimethylaniline hexafluorophosphate in Example 1 of the present invention;

Fig. 3 is the relationship curve of the response slope of the all-solid-state potassium ion selective electrode based on trimethylaniline hexafluorophosphate in Example 1 of the present invention as a function of time;

Fig. 4 is the potential response calibration curve of the all-solid-state calcium ion selective electrode based on N-methyltetrahydrothiophene bistrifluoromethanesulfonimide salt in Example 2 of the present invention;

5 is a potential response calibration curve obtained when the all-solid-state calcium ion selective electrode based on N-methyltetrahydrothiophene bistrifluoromethanesulfonimide salt in Example 2 of the present invention detects calcium ions in milk.

Detailed ways

As shown in Figure 1, a kind of all-solid-state ion-selective electrode based on functional ionic liquid comprises internal reference electrode 3, substrate 4, solid-state ion layer 2, ion-sensitive mold 1 and electrode lead 5;

The internal reference electrode 3 is set on the substrate 4, the electrode lead 5 is connected to the internal reference electrode 3, the internal reference electrode 3 is covered with a solid ion layer 2, and the solid ion layer 2 is covered with an ion sensitive mold 1, and the electrode lead 5 passes through the substrate 4. The following is that the present invention provides two kinds of all-solid-state ion-selective electrodes according to the different materials of the solid-state ion layer 2:

Example 1

(1) An internal reference electrode is set on the substrate, and the internal reference electrode is connected to the electrode lead;

(2) Pretreat the internal reference electrode and the surface of the substrate with absolute ethanol to remove the floating dust on the surface, make the surface clean, consistent in state, and fully dry;

(3) Weigh 40mg of trimethylaniline hexafluorophosphate, and dissolve it in 1mL of organic solvent acetone to obtain an ionic liquid solution;

(4) Weigh 33mg of polyvinyl chloride (polymer), 0.4mg of potassium tetrachlorophenylboride (lipophilic macromolecule) and 1.6mg of valinomycin (potassium ionophore), dissolve it in 1.5mL of organic solvent tetrahydrofuran , then drop 65 μL of dinitrophenyloctyl ether (plasticizer), and mix thoroughly to obtain a potassium ion-sensitive mold solution;

(5) Take an appropriate amount of functional ionic liquid solution, drop it on the surface of the clean electrode substrate, and then place the electrode at room temperature until the solvent acetone evaporates to obtain a solid ionic layer;

(6) Take an appropriate amount of potassium ion-sensitive membrane solution, drop it on the surface of the functional ionic liquid layer, and then place the electrode at room temperature until the organic solvent THF volatilizes completely to prepare the ion-sensitive membrane.

The prepared all-solid-state potassium ion selective electrode is placed in the solution to be tested containing a certain concentration of potassium ions, and an external reference electrode (Ag/AgCl, 3.3mol/L KCl solution) is inserted, and the ion selective electrode is measured by an external instrument The electrode potential relative to the external reference electrode.

Fig. 2 is the potential response correction curve of the all-solid-state potassium ion selective electrode prepared in the present embodiment, and its correction equation is EMF (mV)=59.2Ln (C)+482.6, and wherein EMF is potential value (mV), and C is Potassium ion concentration (mol/L), the correlation coefficient is 0.9918.

The all-solid-state potassium ion-selective electrode prepared in the present embodiment is stored continuously for 30 days at normal temperature and normal state, and its response characteristics are detected every two days, as shown in Fig. 3, the change of its response slope with the storage time, from Fig. 3 It can be seen that the response slope of the all-solid-state potassium ion selective electrode based on the functional ionic liquid is basically maintained at 59.2mv/decade, indicating that the ion selective electrode of the present invention has good working stability.

Example 2

(1) An internal reference electrode is set on the substrate, and the internal reference electrode is connected to the electrode lead;

(2) Pretreat the internal reference electrode and the surface of the substrate with absolute ethanol to remove the floating dust on the surface, make the surface clean, consistent in state, and fully dry;

(3) Weigh 40mg of N-methyltetrahydrothiophene bistrifluoromethanesulfonimide salt, and dissolve it in 1mL of organic solvent acetone to obtain an ionic liquid solution;

(4) Weigh 33mg of polyvinyl chloride (polymer), 0.2mg of sodium tetraphenylborate (lipophilic macromolecule) and 1.8mg of 10,19-bis[(octadecylcarbamoyl)methoxyacetyl] -1, 4, 7, 13, 16-pentoxa-10, 19-diazacycline hexacane (calcium ionophore), which was dissolved in 1.2 mL of organic solvent tetrahydrofuran, and then dropped into 65 μL of hexadiene Acid dioctyl ester (plasticizer), fully mix;

(5) Take an appropriate amount of functional ionic liquid solution, drop it on the surface of the clean electrode substrate, and then place the electrode at room temperature until the solvent acetone evaporates to obtain a solid ionic layer;

(6) Take an appropriate amount of calcium ion-sensitive membrane solution, drop it on the surface of the functional ionic liquid layer, and then place the electrode at room temperature until the solvent tetrahydrofuran evaporates to prepare the ion-sensitive membrane.

Place the prepared all-solid-state calcium ion selective electrode in the solution to be tested containing a certain concentration of calcium ions, and insert an external reference electrode (Ag/AgCl, 3.3mol/L KCl solution), and measure the ion selective electrode through an external instrument The electrode potential relative to the external reference electrode.

Fig. 4 is the potential response correction curve of the all-solid-state calcium ion selective electrode prepared in the present embodiment, and its correction equation is EMF (mV)=29.4Ln (C)+397.7, and wherein EMF is potential value (mV), and C is Calcium ion concentration (mol/L), the correlation coefficient is 0.9927.

The all-solid-state calcium ion selective electrode prepared in this example was used for the detection of calcium ions in milk. Fig. 5 is the calibration curve obtained when the all-solid-state calcium ion selective electrode detects calcium ions in milk, and its calibration equation is EMF (mV) = 29.1Ln (C) + 394.5, wherein EMF (mV) is the potential value, and C is calcium Ion concentration (mol/L), the correlation coefficient is 0.9908.

The above-mentioned embodiments are used to illustrate the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (8)

1. all solid state ion-selective electrode based on functional ion liquid, comprise substrate (4), internal reference electrode (3), solid ionic layer (2) and ion sensitive membrane (1), it is characterized in that: described solid ionic layer (2) is made up of functional ion liquid, the cationic-charge of functional ion liquid has oxidation-reduction quality group, and negative ion is hydrophobic group; Described kation is trimethylaniline ion, N-methyl thiophane ion or 1-ethyl dicyclopentadienyl iron base-3 methylimidazole ion; Described negative ion is hexafluorophosphoricacid acid ions or two fluoroform sulfimide ion.

2. all solid state ion-selective electrode according to claim 1, is characterized in that: described functional ion liquid is room temperature solid ionic liquid.

3. all solid state ion-selective electrode according to claim 1, is characterized in that: described functional ion liquid is trimethylaniline hexafluorophosphate, the two fluoroform sulfimide salt of N-methyl thiophane or 1-ethyl dicyclopentadienyl iron base-3 methylimidazole hexafluorophosphate.

4. all solid state ion-selective electrode according to claim 1, is characterized in that: the thickness of described solid ionic layer (2) is 1 ~ 5 μm.

5. all solid state ion-selective electrode according to claim 4, is characterized in that: the thickness of described solid ionic layer (2) is 3 μm.

6. all solid state ion-selective electrode according to claim 1, is characterized in that: described internal reference electrode is gold electrode, platinum electrode or carbon electrode.

7. all solid state ion-selective electrode according to claim 1, is characterized in that: comprise the contact conductor (5) be connected with internal reference electrode (3).

8. a preparation method for all solid state ion-selective electrode based on functional ion liquid according to claim 1, comprises the following steps:

Substrate arranges internal reference electrode; Dripped by functional ion liquid dissolution homogeneity and be coated in internal reference electrode surface, drying volatilizes solvent, obtained solid ionic layer; Ion-sensitive coating solution is dripped and is coated in solid ionic layer surface, dry obtained ion sensitive membrane; Functional ion liquid is room temperature solid ionic liquid, and cationic-charge has oxidation-reduction quality group, and negative ion is hydrophobic group; Described kation is trimethylaniline ion, N-methyl thiophane ion or 1-ethyl dicyclopentadienyl iron base-3 methylimidazole ion; Described negative ion is hexafluorophosphoricacid acid ions or two fluoroform sulfimide ion.