CN111007121A - Electrochemical sensor, conductive layer thereof and preparation method - Google Patents

Abstract

The invention relates to an electrochemical sensor, a conducting layer thereof and a preparation method thereof. According to the conductive layer of the electrochemical sensor, the carbon nano tubes and/or nano silicon dioxide are doped in the traditional carbon layer, wherein the carbon nano tubes can be effectively combined with substances such as an electronic mediator in the reaction reagent layer, and the electronic mediator can effectively react with a reactant to be detected by utilizing the characteristic of the high specific surface area of the carbon nano tubes, so that the accuracy and the repeatability of a detection result can be improved; the nano silicon dioxide has a three-dimensional network structure, has a large specific surface area, has many surface active centers, shows great activity, and can play a role in improving the catalytic effect when a reaction reagent layer reacts with a target object to be detected, so that the accuracy and the repeatability of a detection result can be effectively improved.

Description

Electrochemical sensor, conductive layer thereof and preparation method

Technical Field

The invention relates to the technical field of electrochemical biochemical detection, in particular to an electrochemical sensor, a conducting layer and a preparation method thereof.

Background

In recent years, attention has been paid to the detection of the content of substances such as blood sugar, uric acid, and lactic acid in blood. The detection method mainly comprises a gravimetric method, a titration method, a phosphotungstic acid reduction method, a high performance liquid chromatography, an enzyme-linked photometric method, an enzyme-linked colorimetric method, an electrochemical method and the like.

The gravimetric method and the titration method have the advantages of long operation time, large error and low accuracy. The phosphotungstic acid reduction method is poor in specificity for detecting uric acid, ascorbic acid contained in a blood sample greatly interferes with the uric acid, and the test error is large. The high performance liquid chromatography has higher sensitivity, but needs large instruments and special devices during detection, needs more blood volume for testing, has longer time and high price, is only suitable for hospitals and is inconvenient for patients to use at home. Clinically, enzyme-linked colorimetry and enzyme-linked photometry are mostly adopted to measure the concentration of uric acid in body fluid, but the requirements on instruments are high, professional operators and special reagents are required, and the enzyme-linked colorimetry and the enzyme-linked photometry are generally influenced by enzyme activity and are not suitable for being used in families. The electrochemical detection method is suitable for occasions such as families and the like, is very convenient to use, but the detection accuracy and the repeatability of the traditional electrochemical detection sensor are still to be improved.

Disclosure of Invention

In view of the above, there is a need for an electrochemical sensor, a conductive layer thereof and a method for manufacturing the same, which can improve detection accuracy and repeatability.

A conductive layer of an electrochemical sensor is a carbon layer doped with carbon nanotubes and/or nanosilica.

In one embodiment, the conductive layer is formed by mixing carbon nanotubes and/or nano silicon dioxide with conductive carbon ink to form a mixed raw material coating and then drying the mixed raw material coating.

In one embodiment, the conductive layer is formed by coating and drying a mixed raw material containing conductive carbon ink, carbon nanotubes and nano silicon dioxide.

In one embodiment, 3 to 8 parts by weight of the carbon nanotubes are added to 1000 parts by weight of the conductive carbon ink in the mixed raw material;

preferably, 4-6 parts by weight of the carbon nanotubes are added to 1000 parts by weight of the conductive carbon ink in the mixed raw materials;

further preferably, 5 parts by weight of the carbon nanotubes are added per 1000 parts by weight of the conductive carbon ink in the mixed raw materials.

In one embodiment, the carbon nanotubes are multi-walled carbon nanotubes.

In one embodiment, the carbon nanotube is selected from at least one of a hydroxyl-modified carbon nanotube, an aldehyde-modified carbon nanotube, and a carboxyl-modified carbon nanotube;

preferably, the carbon nanotube is a carboxyl-modified carbon nanotube.

In one embodiment, 0.5 to 8 parts by weight of the nano silica is added to 1000 parts by weight of the conductive carbon ink in the mixed raw material;

preferably, 1-5 parts by weight of the nano silica is added in every 1000 parts by weight of the conductive carbon ink in the mixed raw materials;

further, it is preferable that the nano silica is added in an amount of 3 to 5 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw material.

In one embodiment thereof, the nanosilica has a specification of SP15, SP30, or SP 50;

preferably, the nanosilica has a specification SP 30.

A preparation method of a conductive layer of an electrochemical sensor comprises the following steps:

fully and uniformly mixing the mixed raw materials used by the conductive layer;

and coating the uniformly mixed raw materials on a corresponding substrate, and drying to obtain the conductive layer.

In one embodiment, the mixing of the mixed raw materials is performed by stirring, before stirring, the conductive carbon ink in the container is controlled not to exceed two thirds of the container capacity, and the stirring speed is controlled to be 1000-3000 r/min.

In one embodiment, the preparation method further comprises the step of performing refrigerated fermentation on the uniformly mixed raw materials in an environment of 2-8 ℃ for 10-30 days before coating the uniformly mixed raw materials on the corresponding substrate.

In one embodiment, the mixed raw materials are coated on the corresponding substrate by adopting a screen printing mode.

In one embodiment, the drying is carried out at 80-120 ℃ for 15-25 min;

preferably, the drying is baking at 100 ℃ for 20 min.

An electrochemical sensor is provided with a reaction cell and a sample feeding flow channel, wherein the sample feeding flow channel is communicated with the reaction cell; a working electrode and a reference electrode are arranged in the reaction tank, a conductive layer covering the working electrode and the reference electrode is further arranged in the reaction tank, the conductive layer is the conductive layer in any embodiment or the conductive layer prepared by the preparation method in any embodiment, a reaction reagent layer for reacting with a target detection object is arranged on the conductive layer, and the reaction reagent layer is exposed in the reaction tank; the electrochemical sensor is also provided with an electrode joint for connecting with external detection equipment, and the electrode joint is electrically connected with the working electrode and the reference electrode.

In one embodiment, the reactive agent layer has a strongly oxidizing electron mediator, or the conductive layer is doped with a strongly oxidizing electron mediator.

In one embodiment, the electron mediator is selected from at least one of potassium ferricyanide, potassium ferrocyanide, ruthenium salt, and ruthenium salt.

In one embodiment, the electrochemical sensor comprises a substrate, a spacer layer and a surface layer, wherein the spacer layer is located between the substrate and the surface layer, and the substrate, the spacer layer and the surface layer cooperate to enclose the reaction cell and the sample injection flow channel; the working electrode, the reference electrode and the electrode joint are arranged on the substrate.

In one embodiment, the spacing layer is a patterned double-sided adhesive layer provided with openings corresponding to the reaction cell and the sample injection flow channel; and/or

The surface layer is a hydrophilic film.

In one embodiment, the substrate is provided with an insulating protection layer in a region outside the reaction cell and the sample injection flow channel, and the insulating protection layer at least surrounds the reaction cell and covers the conductive structure layer in the region where the insulating protection layer is located.

In one embodiment, the reaction cells are multiple, the sample injection channel comprises a main channel and a plurality of branch channels communicated with the main channel, and the plurality of branch channels are respectively communicated with the plurality of reaction cells.

According to the conductive layer of the electrochemical sensor, the carbon nano tubes and/or the nano silicon dioxide are doped in the traditional carbon layer, wherein the carbon nano tubes can be effectively combined with substances such as an electronic mediator in the reaction reagent layer, and the electronic mediator can effectively react with a reactant to be detected by utilizing the characteristic of the high specific surface area of the carbon nano tubes, so that the accuracy and the repeatability of a detection result can be improved; nanometer silica has three-dimensional network structure, possess huge specific surface area, surface active center is many, show very big activity, when the reaction reagent layer reacts with the target object that awaits measuring, can play the effect that improves catalytic effect, and then can effectively improve the accuracy of testing result, and nanometer silica has fine adsorption property, utilize its network structure, can play the effect on restriction reaction reagent layer, prevent to cause the detection reagent flow in the reaction reagent layer because of the flow of the solution that awaits measuring and appear the phenomenon of maldistribution, and then can also improve electrochemical sensor's repeatability.

Drawings

FIG. 1 is a schematic structural diagram of an electrochemical detection sensor according to an embodiment of the present invention;

FIG. 2 is a schematic perspective view of the electrochemical detection sensor of FIG. 1;

fig. 3 is an exploded view of the electrochemical detection sensor shown in fig. 1.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, fig. 2 and fig. 3, an embodiment of the present invention provides anelectrochemical sensor 10 having asample injection channel 11 and areaction cell 12. The sampleintroduction flow channel 11 is communicated with thereaction cell 12. Thereaction cell 12 is provided with a workingelectrode 110 and areference electrode 120. Also disposed inreaction cell 12 is aconductive layer 130 that covers workingelectrode 110 andreference electrode 120. Theconductive layer 130 is provided with a reagent layer (not shown) for reacting with a target analyte. The reactive agent layer is exposed in thereaction cell 12. Theelectrochemical sensor 10 further has anelectrode connector 140 for connecting with an external detection device, and theelectrode connector 140 is electrically connected with the workingelectrode 110 and thereference electrode 120.

In the present embodiment, theconductive layer 130 is a carbon layer doped with carbon nanotubes and/or nano-silica. The carbon nano tube can be effectively combined with substances such as an electron mediator in the reaction reagent layer, and the electron mediator can effectively react with a reactant to be detected by utilizing the characteristic of the high specific surface area of the carbon nano tube, so that the accuracy and the repeatability of a detection result can be improved. Nanometer silica has three-dimensional network structure, possess huge specific surface area, surface active center is many, show very big activity, when the reaction reagent layer reacts with the target object that awaits measuring, can play the effect that improves catalytic effect, and then can effectively improve the accuracy of testing result, and nanometer silica has fine adsorption property, utilize its network structure, can play the effect on restriction reaction reagent layer, prevent to cause the detection reagent flow in the reaction reagent layer because of the flow of the solution that awaits measuring and appear the phenomenon of maldistribution, and then can also improve electrochemical sensor's repeatability.

In one specific example, theconductive layer 130 is formed by mixing carbon nanotubes and/or nano-silica with a conductive carbon ink to form a mixed raw material coating layer and then drying the mixed raw material coating layer. The coating may be of various types of coating techniques, such as but not limited to screen printing techniques. In an alternative example, theconductive layer 130 is formed by coating a mixed raw material including conductive carbon ink, carbon nanotubes, and nano-silica and then drying the coated mixed raw material.

More specifically, in one example, the carbon nanotubes are added in an amount of 3 to 8 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw material. Preferably, the carbon nanotubes are added in an amount of 4 to 6 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw materials. Further preferably, in the mixed raw materials, 5 parts by weight of the carbon nanotubes are added per 1000 parts by weight of the conductive carbon ink.

The carbon nano tube can be various carbon nano tubes, preferably a multi-wall carbon nano tube, can introduce more modifying groups, is convenient for modifying the modifying groups according to the property of an electronic mediator, and improves the detection performance of the product.

Further, the carbon nanotube is selected from at least one of a hydroxyl-modified carbon nanotube, an aldehyde-modified carbon nanotube, and a carboxyl-modified carbon nanotube. Preferably, the carbon nanotubes are carboxyl-modified carbon nanotubes. The carbon nano tube modified by carboxyl has high oxidation degree, and can avoid the further oxidation of the electron mediator which possibly contains strong oxidation in the reaction reagent layer, thereby improving the time stability of the whole conducting layer. It is understood that for electron mediators with weak oxidation, the carbon nanotubes can be modified by hydroxyl or aldehyde group.

In a specific example, 0.5 to 8 parts by weight of nano silica is added per 1000 parts by weight of the conductive carbon ink in the mixed raw material. Preferably, the nano silica is added in an amount of 1-5 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw materials. Further, it is preferable that the nano silica is added in an amount of 3 to 5 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw materials. Research shows that the amount of the nano silicon dioxide added into the conductive carbon ink cannot be too much or too little, if the amount is too little, the nano silicon dioxide does not play a role in testing, and if the amount is too much, the nano silicon dioxide occupies a larger specific surface area, so that the amount of the electron mediator which effectively reacts is reduced. When nano silica is mixed with carbon nanotubes, 1/5, which is a greater amount of nano silica than carbon nanotubes, is effective.

Further, the specification of the nano silicon dioxide is SP15, SP30 or SP 50; preferably, the nanosilica has a specification SP 30. It has been found that, when the particle size of the nano-silica is too small, the nano-silica drops preferentially when the conductive layer is manufactured by a screen printing process or the like, the three-dimensional network structure of the nano-silica in the formed conductive layer does not work, and if the particle size of the nano-silica is relatively large, the nano-silica is difficult to form a uniform phase with conductive carbon ink or the like, and the relatively large nano-silica particles do not exceed the mesh size of the screen printing process, and the silica stays on the screen relatively more.

Theconductive layer 130 may be prepared by, but is not limited to, the following steps:

mixing the raw materials used for theconductive layer 130;

and coating the uniformly mixed raw materials on a corresponding substrate, and drying to obtain theconductive layer 130.

In a specific example, the mixing raw materials are mixed uniformly by stirring, before stirring, the conductive carbon ink in the container is controlled not to exceed two thirds of the container capacity, and the stirring speed is controlled to be 1000-3000 r/min. Preferably, the stirring time is 1 day or more to form a homogeneous phase of the mixed raw materials.

Further, the preparation method also comprises the step of placing the uniformly mixed raw materials into an environment of 2-8 ℃ for refrigeration and fermentation for 10-30 days before coating the uniformly mixed raw materials on a corresponding substrate. Researches find that the stability of the conductive carbon ink can be effectively improved through low-temperature treatment, and the uniformity of a coating can be improved.

In one specific example, the mixed raw materials are coated on the corresponding substrates by means of screen printing.

In one embodiment, the drying is baking at 80-120 ℃ for 15-25 min; preferably, the drying is baking at 100 ℃ for 20 min.

Optionally, the reactant layer of theelectrochemical sensor 10 has a strongly oxidizing electron mediator, or theconductive layer 130 is doped with a strongly oxidizing electron mediator. The strong oxidizing electron mediator is at least one selected from potassium ferricyanide, potassium ferrocyanide, ruthenium salt and ruthenium salt.

In the particular example illustrated, theelectrochemical sensor 10 includes asubstrate 100, aspacer layer 200, and asurface layer 300. Thespacer layer 200 is located between thesubstrate 100 and thesurface layer 300. Thesubstrate 100, thespacer layer 200 and thesurface layer 300 cooperate to define areaction cell 12 and asample injection channel 11, wherein thesubstrate 100 and thesurface layer 300 respectively form two side surfaces of thesample injection channel 11 and thereaction cell 12, and thespacer layer 200 forms side surfaces of thesample injection channel 11 and thereaction cell 12. Workingelectrode 110,reference electrode 120, andelectrode contact 140 are provided onsubstrate 100.

Theelectrochemical sensor 10 may be a single channel, single index detection sensor; or a multi-channel single index detection sensor, and correspondingly, the detection reagent layers in thereaction tanks 12 are the same; it is also possible to use a multi-channel multi-index detection sensor, and accordingly, the detection reagent layers in at least tworeaction cells 12 are different.

Taking the illustrated specific example as an example, thesample injection channel 11 includes amain channel 13 and twobranch channels 14. There are also tworeaction cells 12. The twobranch flow paths 14 correspond to the tworeaction cells 12 one by one. One end of thebranch flow channel 14 is communicated with themain flow channel 13, and the other end of thebranch flow channel 14 is communicated with thereaction tank 12. It is understood that the number of thebranch flow paths 14 and thereaction cells 12 may be three, four, five, etc.

Themain flow channel 13 is uniform in length and/or shape from its open end to eachreaction cell 12. As in the illustrated embodiment, for theelectrochemical sensor 10 having only twobranch flow channels 14 and tworeaction cells 12, the twobranch flow channels 14 are symmetrically disposed with respect to the tworeaction cells 12, so as to ensure that the sample loading speeds of the tworeaction cells 12 are substantially the same, ensure the synchronization of the detection reaction, and facilitate the detection by the apparatus.

Further, the opening dimension of themain flow passage 13 inwardly from the open end thereof is gradually reduced. The opening size ofsprue 13 at the open end is great, is favorable to sample solution to go up kind like this, can effectively prevent sample solution drippage when going up kind, is favorable to reducing the operation degree of difficulty of the process of going up kind, improves the operation convenience.

By arranging the plurality ofbranch flow channels 14 and thereaction cells 12, different reaction reagent layers can be set for eachreaction cell 12 in a targeted manner, and specifically, if at least two reaction reagent layers in the plurality ofreaction cells 12 are different, multi-channel multi-index detection can be simultaneously performed on one sample solution, if a blood sugar detection reagent layer is added into one of thereaction cells 12, and a uric acid detection reagent layer is added into theother reaction cell 12, blood sugar and uric acid detection can be simultaneously performed on one blood sample, and the detection efficiency is remarkably improved.

The workingelectrode 110 and thereference electrode 120 may be, but not limited to, silver layers, and may be formed on a predetermined region of thesubstrate 100 by, for example, silk screening. The workingelectrode 110 and thereference electrode 120 have a plurality of groups, which are respectively arranged corresponding to the plurality ofreaction cells 12, and eachreaction cell 12 is correspondingly provided with a group of workingelectrodes 110 andreference electrodes 120. The positions of the workingelectrode 110 and thereference electrode 120 indifferent reaction cells 12 are substantially the same to ensure the consistency of the detection results, and can be adjusted correspondingly according to different detection indexes.

Theelectrode contact 140 may be, but is not limited to, a conductive contact layer, a conductive spring, a conductive pin, etc. There are also multiple sets ofelectrode contacts 140, each set corresponding to a respective one of the multiple sets of workingelectrodes 110.

Theelectrode contacts 140 are preferably silver layers that are screen printed onto thesubstrate 100, and are highly conductive and sensitive. In a specific example, the carbon protective layer covers the silver layer of theelectrode contact 140, and the carbon protective layer covers the silver layer of theelectrode contact 140, so that the silver layer can be effectively prevented from being oxidized, and the service life of the product can be prolonged.

Preferably, the silver layers of the workingelectrode 110 and thereference electrode 120 extend from thereaction cell 12 to the conductive structure layer integrally formed with the silver layer of theelectrode contact 140, so that the manufacturing process is facilitated, and the manufacturing cost is reduced.

Further, thesubstrate 100 is provided with an insulating protective layer (not shown) in a region outside thesample inlet channel 11 and thereaction cell 12. The insulating protective layer covers the conductive structure layer of the corresponding area except the sampleinjection flow channel 11 and thereaction cell 12. The insulating protective layer is at least arranged around thereaction cell 12 to prevent the reaction liquid in thereaction cell 12 from flowing out to the electrode structure outside thereaction cell 12 to influence the detection result. Preferably, in order to ensure the attaching flatness of thespacer layer 200, the insulating protective layer covers all regions except the ends of the sampleintroduction flow channel 11, thereaction cell 12 and theelectrode connector 140. Through the arrangement of the insulating protection layer, on one hand, insulation is carried out, on the other hand, the electrode structure of the silver layer can be effectively protected, and the problem that the detection accuracy is influenced because the conductive structure layer is damaged in the subsequent manufacturing process is avoided.

In a specific example, thespacer layer 200 is a patterned double-sided adhesive layer with openings corresponding to thereaction cell 12 and thesample injection channel 11. The thickness of thespacer layer 200 may be 0.08 to 0.15mm, such as 0.08mm, 0.09mm, 0.10mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, or 0.15 mm. Thesurface layer 300 is preferably a hydrophilic film layer. Thesurface layer 300 is provided with afirst vent hole 301 communicating with thereaction chamber 12.

Further, as shown in fig. 3, alabel layer 400 is further disposed on thesurface layer 300. Thelabel layer 400 is provided with asecond vent hole 401 communicating with thefirst vent hole 301.

Thefirst vent hole 301 and thesecond vent hole 401 are both disposed above thereaction cell 12 and communicated with thereaction cell 12, so that a siphon channel is formed between themain channel 13 and thereaction cell 12, when the sample is added at the sample adding end, the sample solution can be directly sucked into thereaction cell 12 from the sample adding end by using a siphon effect, and the gas in the originalmain channel 13, thebranch channel 14 and thereaction cell 12 can be exhausted through thefirst vent hole 301 and thesecond vent hole 401.

The electrochemical sensor and the method for manufacturing the same according to the present invention will be described in further detail with reference to specific embodiments.

The following examples will be described by taking as an example the detection of lactic acid in blood using a reaction reagent layer containing lactate oxidase and a potassium ferricyanide electron mediator.

The following embodiments of the method for preparing the conductive layer and the reactive agent layer, the method for assembling the electrochemical sensor, and the method for detecting the electrochemical sensor are referred to as follows:

preparing: after stirring and mixing the mixed raw materials for forming the conductive layer, checking the mixed raw materials, wherein the mixed raw materials have the advantages of no scab, no blocking and good fluidity; stirring the mixed raw materials by using a stirrer again before screen printing to ensure that the raw materials are fully and uniformly mixed; during stirring, the amount of the conductive carbon printing ink in the container is not more than two thirds of the container capacity, and the rotating speed of the stirrer is controlled at 1000-3000 r/min; positioning the substrate at a suitable position on the printing table; mounting the screen on a screen frame of a screen printing machine, and locking and fixing the screen after aligning the positioning holes on the screen with the positioning holes of the substrate; adjusting the distance between the screen and the substrate, and requiring the screen to be parallel to the substrate;

fermentation: placing the mixed raw materials in a refrigerator at the temperature of 2-8 ℃ for refrigeration, and fermenting for 10-30 days;

and (3) silk-screen printing: screen printing the mixed raw materials to a preset position of a substrate;

baking: placing the substrate printed with the conductive layer on a drying rack, and pushing the drying rack into an oven to bake at 100 +/-20 ℃; timing after pushing, and baking for 20 minutes; the gloves are worn to avoid scalding;

assembling: dropping enzyme solution containing lactate oxidase and potassium ferricyanide electronic mediator on the dried conductive layer, drying, sticking the substrate and the surface layer by using a double-sided adhesive spacing layer, punching to manufacture test paper, and inserting the test paper on a testing instrument;

and (3) testing: respectively preparing 3 different lactic acid solutions, wherein the three solutions are whole blood samples with lactic acid contents of 0.5-2mmol/l, 6-10mmol/l and 12-20mmol/l respectively, and the Hematocrit (HCT) is adjusted to be 40% -42%; the real value of the lactic acid of the whole blood sample refers to the detection result of the ABL800 instrument; the electrochemical sensor can test voltage within the range of 100-1000 MV, and measure the content of specific components in a sample in a room temperature environment; the electrochemical sensors of the following embodiments all adopt 300MV voltage, the voltage of the working electrode relative to the reference electrode is 300MV which is positive, and the content of the lactic acid component in the whole blood sample is detected under the condition of room temperature; the whole blood samples at each concentration were subjected to 20 replicates, and the results were averaged.

Stability test: the electrochemical sensor just manufactured and the electrochemical sensor stored for 2 years (placed for 2 years at normal temperature or accelerated treatment, for example, placed for 2 weeks in an environment at 65 ℃ or placed for 1 month in an environment at 55 ℃) are respectively used for testing under the test voltage of 300MV, the sample to be tested is a whole blood sample with the lactic acid content of 0.5-2mol/l, 6-10mol/l and 12-20mol/l, the hematocrit is adjusted to 40-42%, the real value of the whole blood sample refers to the detection result of an ABL800 instrument, 20 times of repeated experiments are respectively carried out on the whole blood sample with each concentration, and the result is averaged.

The conductive carbon ink in each of the following examples is a carbon ink available from dupont, carbon nanotubes are available from Nanjing Xiancheng nanomaterial science and technology, Inc., and nano silica is available from Beijing Deke island gold science and technology, Inc.

The following examples are illustrative in all terms of the particular materials and amounts used, and it is to be understood that the invention is not limited in this regard to other examples, as specifically exemplified by the particular materials and ranges of data set forth above (e.g., in the claims).

Comparative example

The conductive layer was formed using conductive carbon ink as a raw material, and the results are shown in table 1 below.

TABLE 1

	0.5-2mol/l	6-10mol/l	15-20mol/l
				ABL800	0.9	7.1	18.9
Electrochemical sensor	1.71	7.06	13.35
				SD	0.53	0.81	1.6
CV	30.99％	11.47％	11.99％
				BIAS	0.81	-1％	-29％

Example 1

The mixed raw materials for forming the conductive layer were 1000g of conductive carbon ink + 5g of carbon nanotubes, and the results are shown in tables 2 to 8 below.

TABLE 2

TABLE 3

TABLE 4

TABLE 5

TABLE 6

TABLE 7

TABLE 8

The result shows that compared with the comparative case, the carbon nano tube containing different groups is added, the detection accuracy and the repeatability of the electrochemical sensor are improved, and the sensitivity is improved.

When the carbon nano-tube containing different groups is added for real stability test, the observation shows that when the added carbon nano-tube contains carboxyl, the stability is better than that of the carbon nano-tube containing hydroxyl or aldehyde group after the carbon nano-tube is placed for 2 years.

And (4) analyzing results: the potassium ferricyanide has stronger oxidizability and can partially oxidize hydroxyl or aldehyde groups in the carbon nanotube material, experiments prove that the stable carbon nanotube material test paper containing carboxyl is added in the formula to be more stable, and the blank contrast only added with the conductive carbon ink is observed to find that when the potassium ferricyanide is used as an electronic medium, the difference of the stability deviation percentage of the carbon nanotube material with or without the carboxyl is not large, which indicates that the potassium ferricyanide has less oxidation on the carbon nanotube material containing the carboxyl.

Example 2

The mixed raw materials for forming the conductive layer were 1000g of conductive carbon ink + 3g of nano silica, and the results are shown in tables 9 to 12 below.

TABLE 9

Watch 10

TABLE 11

TABLE 12

The result shows that compared with the comparative case, the nano silicon dioxide with different specifications is added, the detection accuracy and the repeatability of the electrochemical sensor are improved, and the sensitivity is improved.

Embodiment 3

The mixed raw materials for forming the conductive layer were 1000g of conductive carbon ink, 5g of carbon nanotubes and 3g of nanosilica, and the results are shown in tables 13 to 16 below.

Watch 13

TABLE 14

Watch 15

TABLE 16

Concentration of lactic acid	Determination of lactic acid concentration at the completion of production	The concentration of lactic acid was measured after 2 years of standing
			1.2	1.3	1.4
7.3	7.2	7.3
			17.5	17.3	16.9

The results show that: after the nano silicon dioxide is further added on the basis of adding the carbon nano tubes, the repeatability and the accuracy of the result are improved (partial results are reduced compared with the single addition of the nano silicon dioxide and mainly relate to the selection of material specifications, and the selection of the nano silicon dioxide and the carbon nano tubes can also be seen to be a process with a complex mechanism), especially for the nano silicon dioxide with the specification of SP 30.

The nano silicon dioxide has a three-dimensional network structure, has a large specific surface area, shows great activity and can form a network structure, and the nano silicon dioxide has the advantages of large specific surface area, more surface active centers and capability of improving the catalytic effect. The nano silicon oxide has good adsorption property and good stability, can be used as a material in carbon printing ink of a novel sensor, and achieves better effect.

Silica is mainly divided into three types: SP15, SP30 and SP50, wherein the test results show that the effect of the nano silica SP30 added to the conductive carbon ink is better.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (20)

1. The conductive layer of the electrochemical sensor is characterized in that the conductive layer is a carbon layer doped with carbon nanotubes and/or nano silicon dioxide.

2. The conductive layer according to claim 1, wherein the conductive layer is formed by coating a mixed raw material formed by mixing carbon nanotubes and/or nanosilica with a conductive carbon ink and then drying the coated layer.

3. The conductive layer of claim 1, wherein the conductive layer is formed by coating a mixed raw material comprising conductive carbon ink, carbon nanotubes and nano silica and then drying the coated mixed raw material.

4. The conductive layer according to claim 2 or 3, wherein 3 to 8 parts by weight of the carbon nanotubes are added per 1000 parts by weight of the conductive carbon ink in the mixed raw material;

preferably, 4-6 parts by weight of the carbon nanotubes are added to 1000 parts by weight of the conductive carbon ink in the mixed raw materials;

further preferably, 5 parts by weight of the carbon nanotubes are added per 1000 parts by weight of the conductive carbon ink in the mixed raw materials.

5. The conductive layer of claim 2 or 3, wherein the carbon nanotubes are multi-walled carbon nanotubes.

6. The conductive layer according to claim 2 or 3, wherein the carbon nanotube is selected from at least one of a hydroxyl group-modified carbon nanotube, an aldehyde group-modified carbon nanotube, and a carboxyl group-modified carbon nanotube;

preferably, the carbon nanotube is a carboxyl-modified carbon nanotube.

7. The conductive layer according to claim 2 or 3, wherein 0.5 to 8 parts by weight of the nano silica is added per 1000 parts by weight of the conductive carbon ink in the mixed raw material;

preferably, 1-5 parts by weight of the nano silica is added in every 1000 parts by weight of the conductive carbon ink in the mixed raw materials;

further, it is preferable that the nano silica is added in an amount of 3 to 5 parts by weight per 1000 parts by weight of the conductive carbon ink in the mixed raw material.

8. The conductive layer of claim 2 or 3, wherein the nanosilica has a specification of SP15, SP30, or SP 50;

preferably, the nanosilica has a specification SP 30.

9. A preparation method of a conductive layer of an electrochemical sensor is characterized by comprising the following steps:

fully and uniformly mixing the mixed raw materials used for the conductive layer according to any one of claims 2 to 8;

and coating the uniformly mixed raw materials on a corresponding substrate, and drying to obtain the conductive layer.

10. The preparation method according to claim 9, wherein the raw materials are mixed by stirring, the conductive carbon ink in the container is controlled not to exceed two thirds of the container capacity before stirring, and the stirring speed is controlled to be 1000 to 3000 r/min.

11. The method according to claim 9, further comprising the step of subjecting the uniformly mixed raw materials to cold storage fermentation at 2 to 8 ℃ for 10 to 30 days before applying the uniformly mixed raw materials to the corresponding substrate.

12. The method of claim 9, wherein the mixed raw materials are coated on the corresponding substrate by screen printing.

13. The method according to any one of claims 9 to 12, wherein the drying is carried out at 80 to 120 ℃ for 15 to 25 min;

preferably, the drying is baking at 100 ℃ for 20 min.

14. An electrochemical sensor is characterized by comprising a reaction cell and a sample injection flow channel, wherein the sample injection flow channel is communicated with the reaction cell; a working electrode and a reference electrode are arranged in the reaction tank, a conductive layer covering the working electrode and the reference electrode is further arranged in the reaction tank, the conductive layer is the conductive layer according to any one of claims 1 to 8 or the conductive layer prepared by the preparation method according to any one of claims 9 to 13, a reaction reagent layer for reacting with a target detection object is arranged on the conductive layer, and the reaction reagent layer is exposed in the reaction tank; the electrochemical sensor is also provided with an electrode joint for connecting with external detection equipment, and the electrode joint is electrically connected with the working electrode and the reference electrode.

15. The electrochemical sensor of claim 14, wherein the reactive agent layer has a strongly oxidizing electron mediator or the conductive layer is doped with a strongly oxidizing electron mediator.

16. The electrochemical sensor of claim 15, wherein the electron mediator is selected from at least one of potassium ferricyanide, potassium ferrocyanide, ruthenium salt, and ruthenium salt.

17. The electrochemical sensor of claim 14, wherein the electrochemical sensor comprises a substrate, a spacer layer, and a surface layer, the spacer layer being located between the substrate and the surface layer, the substrate, the spacer layer, and the surface layer cooperating to define the reaction cell and the sample injection flow channel; the working electrode, the reference electrode and the electrode joint are arranged on the substrate.

18. The electrochemical sensor of claim 15, wherein the spacer layer is a patterned double-sided adhesive layer having openings corresponding to the reaction cell and the sample injection flow channel; and/or

The surface layer is a hydrophilic film.

19. The electrochemical sensor of claim 14, wherein the substrate is provided with an insulating protective layer in a region outside the reaction cell and the sample inlet channel, the insulating protective layer at least surrounding the reaction cell and covering the conductive structure layer in the region.

20. The electrochemical sensor according to any one of claims 14 to 19, wherein the reaction cells are plural, the sample injection channel includes a main channel and a plurality of branch channels communicated with the main channel, and the plurality of branch channels are respectively communicated with the plurality of reaction cells.

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