A high-sensitivity flexible electrochemical sensor and a preparation method and application thereof

Abstract

The present application relates to a high-sensitivity flexible electrochemical sensor and its preparation method and application, the preparation method comprises the following steps: step S1: preparation of NS-TiO2@M-HG composite material; step S2: preparation of rGO modified silk screen printing electrode rGSPE; step S3: NS-TiO2@M-HG composite material is modified on the working electrode of rGSPE, and NS-TiO2@M-HG / SPE is obtained. Compared with the prior art, the sensor array has a wide detection range, low detection limit and high sensitivity, while maintaining mechanical flexibility, anti-interference ability and repeatability. Through in-situ sweat biomarker detection during exercise, the sensor effectively tracked the fluctuations of ascorbic acid (AA), dopamine (DA) and uric acid (UA) levels in the volunteers. This practical application highlights the potential of the sensor in continuous health monitoring, early disease detection and personalized medical monitoring, making it a promising tool in the field of modern healthcare.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biosensors, and relates to a flexible electrochemical sensor with high sensitivity and a preparation method and application thereof. BACKGROUND

[0002] Wearable biosensors show great potential in continuous and real-time monitoring of physiological parameters, enabling health assessment to break through the limitations of traditional cumbersome equipment. These flexible wearable devices, as a major advance over traditional rigid instruments, provide on-site analysis functions to meet the growing demand for portable health monitoring solutions. For flexible sensors, choosing the right material is crucial, and substrates with superior mechanical properties play a key role in ensuring comfortable fit and seamless adaptation to skin contours.

[0003] Various flexible wearable chemical sensors have been developed for the detection of biological fluids such as sweat, tears, and saliva, enabling direct monitoring of electrolytes, metabolites, and heavy metals. Among them, sweat is particularly prominent, as a rich source of biomarkers, it is very suitable for non-invasive monitoring due to its easy access to the skin surface. The composition of sweat is closely related to the composition of plasma, providing valuable insights into individual health status. Key metabolites in sweat, such as potassium ions and other electrolytes, are key indicators of hydration status and play an important role in the diagnosis and monitoring of diseases such as cystic fibrosis and electrolyte imbalance. Ascorbic acid (AA), also known as vitamin C, is an essential nutrient involved in tissue growth and repair, collagen synthesis, and immune function. Dopamine (DA) as an important neurotransmitter plays a crucial role in the central nervous system and is closely related to neurological diseases such as Parkinson's disease and Alzheimer's disease. Uric acid (UA) is the final product of purine metabolism, which helps in energy metabolism and antioxidant activity, and abnormal levels are associated with diseases such as gout, hyperuricemia, and metabolic syndrome.

[0004] Effective detection of these biomarkers in sweat is crucial for disease monitoring and prevention. However, given that the concentration of such markers is usually at a low level, the sensor must have high sensitivity to achieve accurate detection.

[0005] Two-dimensional transition metal carbide MXene is a class of two-dimensional material with excellent properties, with high electrical conductivity, and electrons can be efficiently transmitted within the material, greatly facilitating the conduction of electrochemical signals.

[0006] Hollow graphene (HGO) as a derivative material of graphene has a rich pore structure, these pores not only increase the specific surface area of the material, allowing more reactants to be adsorbed and reacted on the material surface, but also effectively shorten the path of mass transport, accelerating the rate of electrochemical reactions.

[0007] At present, although the research group in the related field has published the results of the design and application of flexible sweat electrochemical sensors, these results still have many defects, such as complicated manufacturing process and high cost, only single component detection can be achieved, and during the detection process, sweat is easy to accumulate on the surface of the sensor, which makes it impossible to monitor fresh sweat in real time. In view of this, in-depth research on flexible sweat multi-marker electrochemical sensors has become an urgent need of the times.

[0008] Chinese patent application CN 116337964 A discloses a preparation method of an electrochemical sensor, which specifically comprises: using high-energy laser to induce a three-dimensional porous graphene pattern (including three electrodes) on the surface of a clean polyimide film, insulating the three-electrode lead-out part and the area outside the reaction cell to obtain a sensing layer. Using high-energy laser to engrave a sample inlet and a microchannel on the upper and lower PDMS films respectively, after cleaning and removing impurities, dipping and adhering the unsolidified PDMS to obtain a PDMS layer. The PDMS layer and the sensing layer are adhered by double-sided tape, the holes of the double-sided tape are aligned with the reaction cell, so that the sample inlet, the microchannel and the reaction cell are connected, and the sensor is obtained. The sensor can simultaneously detect three components of uric acid, tyrosine and potassium chloride in sweat, detect uric acid and tyrosine in the differential pulse voltammetry mode, and detect potassium chloride in the electrochemical impedance spectroscopy mode. It should be pointed out that the technical scheme uses high-energy laser for pattern induction and engraving, which has high equipment cost, large energy consumption and high overall production cost, and is not conducive to large-scale production and popularization.

[0009] Chinese patent application CN 114813868 A discloses an environmental humidity power generation device and a preparation method thereof, which specifically comprises: a sensor composed of a flexible substrate, an electrode array and a paper-based microfluidic device, which are bonded by medical tape. The electrode array includes a sodium ion working electrode, a potassium ion working electrode, a glucose working electrode and a reference electrode. The sodium ion working electrode is composed of a printed carbon electrode, a gold nanoparticle / metal organic framework derivative composite layer and a sodium ion selective membrane; the potassium ion working electrode is similar, containing a potassium ion selective membrane; the glucose working electrode is composed of a printed carbon electrode, a gold nanoparticle / metal organic framework derivative composite layer and a glucose dehydrogenase layer; and the reference electrode is composed of a printed silver-silver chloride electrode and a polyvinyl butyral layer. The paper-based microfluidic device is formed by wax printing and folding in independent areas on the paper substrate, and is used for collecting and guiding sweat to prevent sweat accumulation and rapid evaporation. It should be pointed out that the preparation process of the technical scheme needs oxygen plasma treatment and sodium dodecyl sulfate (SDS) treatment, which has high requirements for the operating environment, increases the complexity of the process, and the gold nanoparticles required are relatively expensive raw materials. The production of the paper-based microfluidic device requires special wax printing equipment and hot pressing equipment, which further increases the manufacturing cost. SUMMARY

[0010] The present application aims to provide a flexible electrochemical sensor with high sensitivity and a preparation method and application thereof, and the obtained electrochemical sensor has the advantages of wide detection range, low detection limit and high sensitivity, while maintaining mechanical flexibility, anti-interference ability and repeatability.

[0011] The purpose of the present application can be achieved by the following technical solutions:

[0012] In the first aspect, the present application provides a preparation method of a flexible electrochemical sensor with high sensitivity, comprising the following steps:

[0013] S1, ultrasonically mix HGO solution and MXene solution, then add thiourea powder, continue to ultrasonic, and then transfer into a reaction kettle for hydrothermal reaction, centrifugal washing, and then re-disperse in deionized water to obtain NS-TiO2@MX-HG solution;

[0014] S2, mix rGO powder and carbon ink (i.e. carbon paste ink) to obtain chemically reduced graphene oxide modified ink material, and then coat the ink material on a PET substrate by silk screen printing technology to prepare a working electrode, and dry to obtain a chemically reduced graphene oxide modified silk screen printed electrode rGSPE;

[0015] S3, coat the NS-TiO2@MX-HG solution obtained in S1 on the composite electrode NS-TiO2@M-HG / SPE obtained in S2 to obtain a flexible electrochemical sensor.

[0016] Further, in S1, the MXene solution is prepared by liquid etching method.

[0017] The HGO solution is prepared by first preparing GO by Hammer method, and then etching GO by H2O2.

[0018] Further, in S2, the mass ratio of HGO, MXene and thiourea is 1:(0.5-3):(1-10).

[0019] Further, in S2, the temperature of the hydrothermal reaction is (150-250)℃, and the time is (8-16)h.

[0020] Further, in S3, the addition ratio of rGO powder to carbon paste ink is (1-3):5

[0021] Further, in S5, the concentration of the NS-TiO2@MX-HG solution is 1.2-1.8mg / mL, and the coating amount is (3-12)μL / 6mm 2 .

[0022] It should be noted that the in-situ growth of TiO2 nanoparticles on the surface of MXene material provides advantages for sensor design. From a synergistic perspective, MXene, with its high conductivity, forms a conductive scaffold, ensuring rapid electron flow and laying the foundation for electrochemical signal transmission. Simultaneously, the TiO2 nanoparticles, through their structure and activity, enhance electrocatalytic capabilities, improving detection sensitivity and response speed. The porous HGO network, as a key component, can both capture and adsorb ions and shorten electron transfer paths, achieving highly efficient promotion of ion and electron transfer. Furthermore, the introduction of additional elements through specific doping creates more active sites both inside and outside the material.

[0023] In a second aspect, the present invention provides a highly sensitive flexible electrochemical sensor, which is prepared using the preparation method described above.

[0024] In a third aspect, the present invention provides an application of a highly sensitive flexible electrochemical sensor in the in-situ detection of biomarkers in sweat.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The sensor array of the present invention has the characteristics of wide detection range, low detection limit and high sensitivity, while maintaining mechanical flexibility, anti-interference ability and repeatability.

[0027] (2) The highly sensitive flexible electrochemical sensor prepared by the present invention was verified by in-situ sweat biomarker detection during exercise. The sensor effectively tracked the fluctuations of AA, DA and UA levels in volunteers. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the flexible electrochemical sensor prepared according to the present invention;

[0029] Figure 2 SEM image of NS-TiO2@M-HG composite material required for the flexible electrochemical sensor prepared in this invention;

[0030] Figure 3 Electrochemical performance of the flexible electrochemical sensor prepared in this invention;

[0031] Figure 4 The flexible electrochemical sensor prepared for this invention is based on AA / UA / DA sensing; Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0033] In the following examples, the specific sources of each raw material are as follows:

[0034] Preparation of MXene solution: Take concentrated HCL solution (10M, 30mL) and LiF (3.5g) and stir to react (37℃, 45min), then add MAX original phase (Ti3AlC 2， 2.5g) to the mixture and stir to react in a water bath (40℃, 28h). After the reaction is completed, transfer it to a centrifuge tube and centrifuge to wash until the final supernatant pH is stable at 6.0. Add an appropriate amount of ethanol to the washed precipitate and ultrasonic for 70min. Finally, centrifuge to retain the supernatant to obtain MXene.

[0035] Preparation of HGO solution: Take pure GO solution (3.5mg / mL, 50mL), add 10mL H2O2 as reducing agent, and mix well. Then, immerse in an oil bath at high temperature (180℃, 2h) to obtain HGO.

[0036] The slurry used is a commercial carbon slurry ink (Shanghai Baoyin Electronic Material Co., Ltd., BY-2085) and silver chloride slurry (Suzhou Yituo Sensor Technology Co., Ltd., YTXD-5020).

[0037] Preparation of flexible three-electrode sensor: Use screen printing process, and polyethylene terephthalate (PET) is selected as the flexible substrate for the flexible electrode. Screen printing is performed on a screen printing machine by pre-setting the screen pattern. First, use carbon slurry ink to print the working electrode and counter electrode through the screen. After printing, place it in an oven for drying at about 40℃ for about 2h to ensure complete drying of the carbon slurry ink. Then, use silver chloride slurry to print the reference electrode through the screen. After printing the reference electrode, place it in an oven for complete drying at 50℃.

[0038] Here, the electrochemical three-electrode system includes the working electrode, the reference electrode, and the counter electrode. The working electrode and the counter electrode of the sensor are printed with carbon slurry ink, and the reference electrode is printed with silver chloride. The working electrode is the site where the target electrochemical reaction occurs. By measuring and controlling the current and potential of the working electrode, the process and characteristics of the electrochemical reaction can be studied. The reference electrode provides a stable and known potential reference for the working electrode, ensuring the accuracy and repeatability of the measurement results. The counter electrode forms a current loop with the working electrode, sharing the charge transfer, reducing the polarization of the working electrode, ensuring the accuracy of the potential control, and improving the precision and reliability of the electrochemical measurement. In addition, the coating amount of the working electrode, the counter electrode, and the reference electrode (the substrate of the three electrodes is polyethylene terephthalate (PET)) is 5mL / cm 2 .

[0039] The rGO powder was prepared according to the reference (Zhang Y, Wu C, Zhang J, et al. Mass Transport Effect on Graphene Based Enzyme Electrochemical Biosensor for Oxalic Acid Detection [J]. Journal of The Electrochemical Society, 2017, 164(2): B29.).

[0040] The rest of the raw materials or processing techniques, if not specifically stated, are all conventional commercially available raw materials or conventional processing techniques in the art.

[0041] Example 1

[0042] A method for preparing a flexible electrochemical sensor with high sensitivity, the specific steps are as follows:

[0043] (1) MXene solution was prepared by liquid etching method.

[0044] (2) GO was prepared by Hammer method. Take pure GO solution, add H2O2 as reducing agent, after mixing evenly, high temperature reaction in oil bath, soaking, get HGO solution.

[0045] (3) Take HGO solution and MXene solution, ultrasonic mixing, control the mass ratio of HGO and MXene to be 1:0.5, take thiourea powder and put it into the mixed solution, control the mass ratio of thiourea NS and HGO to be 1:1, continue to ultrasonic. Put the mixed solution into a polytetrafluoroethylene reaction kettle, hydrothermal reaction at 150℃ for 16h, centrifugal washing, then disperse in deionized water to get NS-TiO2@MX-HG solution, its concentration is 1.5mg / mL;

[0046] (4) Mix rGO and carbon ink (according to the mass ratio 1:5) to form a composite material of chemically reduced graphene oxide modified ink, then use screen printing technology to coat the chemically reduced graphene oxide modified ink on the PET substrate to get the working electrode, the coating amount is 5mL ink / cm 2 , then dry thoroughly. This produces a chemically reduced graphene oxide modified screen printed electrode (rGSPE);

[0047] (5) Accurately dispense 12μL of NS-TiO2@MX-HG solution (1.5mg / mL) prepared in step (3) to the center point of the rGSPE electrode (coated area 6mm 2) on the rGSPE. The modified electrode was then dried under vacuum conditions to obtain the NS-TiO2@M-HG / SPE.

[0048] Example 2

[0049] A method for preparing a flexible electrochemical sensor with high sensitivity includes the following specific steps:

[0050] (1) MXene solution was prepared by liquid etching method. Concentrated HCL solution was stirred with LiF, and then MAX original phase was added and stirred in a water bath at constant temperature. Finally, MXene was obtained by centrifugal washing and ultrasonic etching.

[0051] (2) GO was prepared by Hammer method. Pure GO solution was taken, H2O2 was added as reducing agent, and then mixed uniformly. HGO was obtained by high-temperature reaction in oil bath and soaking.

[0052] (3) HGO solution and MXene solution were taken and ultrasonically mixed. The mass ratio of HGO to MXene was controlled to be 1:3. Thiourea powder was weighed and put into the mixed solution. The mass ratio of NS thiourea to HGO was controlled to be 10:1, and ultrasonic was continued. The mixed solution was transferred into a polytetrafluoroethylene reaction kettle, and hydrothermal reaction was carried out at 200℃ for 12h. After centrifugal washing, the solution was dispersed in deionized water to obtain NS-TiO2@MX-HG solution 1.5mg / mL.

[0053] (4) rGO was mixed with carbon ink (mass ratio 2:5) to form a composite material of chemically reduced graphene oxide modified ink. Then, the chemically reduced graphene oxide modified ink was coated on the PET substrate using screen printing technology to prepare a working electrode. The coating amount was 5mL of ink / cm 2 , and then thorough drying was carried out. This produced a chemically reduced graphene oxide modified screen printed electrode (rGSPE);

[0054] (5) 6μL of NS-TiO2@MX-HG solution (1.5mg / mL) was accurately dispensed onto the center point (coated area 6mm 2 ) of the rGSPE electrode. Then the modified electrode was dried under vacuum conditions to obtain the NS-TiO2@M-HG / SPE.

[0055] Example 3

[0056] A method for preparing a flexible electrochemical sensor with high sensitivity includes the following specific steps:

[0057] (1) MXene solution was prepared by liquid etching method. Concentrated HCL solution was taken and reacted with LiF by stirring, then MAX phase was added and reacted in a water bath by constant temperature stirring, and finally MXene was obtained by centrifugal washing and ultrasonic etching.

[0058] (2) GO was prepared by Hammer method. Pure GO solution was taken and mixed with H2O2 as reducing agent, then high temperature reaction and soaking were carried out in oil bath, and HGO was obtained.

[0059] (4) rGO was mixed with carbon ink (mass ratio 3:5) to form a composite material of chemically reduced graphene oxide modified ink, and then the chemically reduced graphene oxide modified ink was coated on the PET substrate by screen printing technology to obtain a working electrode, and the coating amount was 5 mL of ink / cm 2 , and then thorough drying was carried out. This produced a chemically reduced graphene oxide modified screen printed electrode (rGSPE);

[0060] (5) 4 μL of NS-TiO2@MX-HG solution (1.5 mg / mL) was accurately dispensed on the center point (coated area 6 mm 2 ) of the rGSPE electrode. Then the modified electrode was dried under vacuum conditions to obtain NS-TiO2@M-HG / SPE.

[0061] Example 4

[0062] A method for preparing a high-sensitivity flexible electrochemical sensor, the specific steps of which are as follows:

[0063] (1) MXene solution was prepared by liquid etching method. Concentrated HCL solution was taken and reacted with LiF by stirring, then MAX phase was added and reacted in a water bath by constant temperature stirring, and finally MXene was obtained by centrifugal washing and ultrasonic etching.

[0064] (2) GO was prepared by Hammer method. Pure GO solution was taken and mixed with H2O2 as reducing agent, then high temperature reaction and soaking were carried out in oil bath, and HGO was obtained.

[0065] (3) Take HGO solution and MXene solution, ultrasonic mixing, control the mass ratio of HGO and MXene is 1:3, take thiourea powder into the mixed solution, control the mass ratio of thiourea NS and HGO is 8:1, continue to ultrasonic. The mixed solution is transferred into a polytetrafluoroethylene reaction kettle, hydrothermal reaction at 250℃ for 8h, centrifugal washing, then dispersed in solvent deionized water, to get NS-TiO2@MX-HG solution 1.5mg / mL;

[0066] (4) Mix rGO with carbon ink (mass ratio 1:2) to form a composite chemical reduced graphene oxide modified ink, then use screen printing technology to coat the chemical reduced graphene oxide modified ink on the PET substrate to obtain a working electrode, the coating amount is 5mL ink / cm 2 , then dry thoroughly. This produces a chemical reduced graphene oxide modified screen printed electrode (rGSPE);

[0067] (5) Accurately dispense 3μL of NS-TiO2@MX-HG solution (1.5mg / mL) on the center point (coated area 6mm 2 ) of the rGSPE electrode. Then dry the modified electrode under vacuum conditions to obtain NS-TiO2@M-HG / SPE.

[0068] Comparative Example 1

[0069] Compared with Example 4, the provided electrochemical sensor is a graphene oxide modified screen printed electrode (rGSPE), and the modification of NS-TiO2@MX-HG is omitted.

[0070] Comparative Example 2

[0071] Compared with Example 4, the introduction of MXene is omitted, and the specific process is as follows:

[0072] (1) Prepare GO by Hammer method. Take pure GO solution, add H2O2 as reducing agent, after mixing evenly, high temperature reaction in oil bath, soaking, get HGO.

[0073] (2) Take HGO solution, control the mass ratio of thiourea NS and HGO is 8:1, continue to ultrasonic. The mixed solution is transferred into a polytetrafluoroethylene reaction kettle, hydrothermal reaction at 250℃ for 8h, centrifugal washing, then dispersed in solvent deionized water, to get NS-HG solution 1.5mg / mL;

[0074] (3) rGO was mixed with carbon ink (mass ratio 1:2) to form a composite chemical reduced graphene oxide modified ink, and then the chemical reduced graphene oxide modified ink was coated on a PET substrate using a screen printing technique to obtain a working electrode, with a coating amount of 5 mL of ink / cm 2 and then thoroughly dried. This resulted in a chemical reduced graphene oxide modified screen printed electrode (rGSPE);

[0075] (4) 3 μL of the NS-HG solution (1.5 mg / mL) described in step (3) was accurately dispensed onto the center point of the rGSPE electrode (coated area of 6 mm 2 in diameter). The modified electrode was then dried under vacuum conditions to obtain an NS-HG / rGSPE.

[0076] Comparative Example 3

[0077] Compared with Example 4, the addition of HGO was omitted, and the specific process was as follows:

[0078] (1) A MXene solution was prepared using a liquid etching method. Concentrated HCL solution was stirred with LiF, and then MAX phase was added to the mixture for constant temperature stirring in a water bath. Finally, MXene was obtained by centrifugal washing and ultrasonic etching.

[0079] (2) The MXene solution was taken, and the mass ratio of thiourea NS to MXene was controlled to be 8:3, and ultrasonic was continued. The mixed solution was transferred into a polytetrafluoroethylene reaction kettle, and hydrothermal reaction was carried out at 250°C for 8 hours. After centrifugal washing, the NS-MXene solution 1.5 mg / mL was obtained by dispersing in deionized water.

[0080] (3) rGO was mixed with carbon ink (1:2) to form a composite chemical reduced graphene oxide modified ink, and then the chemical reduced graphene oxide modified ink was coated on a PET substrate using a screen printing technique to obtain a working electrode, with a coating amount of 5 mL of ink / cm 2 and then thoroughly dried. This resulted in a chemical reduced graphene oxide modified screen printed electrode (rGSPE);

[0081] (4) 3 μL of the NS-MXene solution (1.5 mg / mL) described in step (3) was accurately dispensed onto the center point of the rGSPE electrode (coated area of 6 mm 2 in diameter). The modified electrode was then dried under vacuum conditions to obtain an NS-MXene / rGSPE.

[0082] The flexible electrochemical sensor prepared in the example was tested as follows:

[0083] Figure 1Schematic diagram of the flexible electrochemical sensor prepared for the present application.

[0084] The sensor utilizes reduced graphene oxide (rGO) ink to screen print electrodes on a PET substrate (rGSPE), which is then modified with NS-TiO2@M-HG hybrid material to form NS-TiO2@M-HG / rGSPE, allowing simultaneous detection of ascorbic acid (AA), uric acid (UA) and dopamine (DA).

[0085] Figure 2 SEM image of the composite material NS-TiO2@M-HG required for the flexible electrochemical sensor prepared for the present application.

[0086] The morphological characteristics of the samples were analyzed using a scanning electron microscope (SEM, Zeiss Ultra 550, EDS super-X), such as Figure 2 As shown in FIG. 5, the NS-TiO2@M-HG composite material presents a layered structure. Figure 3 Electrochemical performance of the flexible electrochemical sensor prepared for the present application. The cyclic voltammetry of the flexible electrodes with different modifications was tested using a 1 mM K3[Fe(CN)6] / K4[Fe(CN)6] solution as a probe. As shown in FIG. 6, Figure 3 As shown in FIG. 6, NS-MXene / rGSPE exhibits smaller ΔE p and lower Rct than rGSPE and NS-HG / rGSPE, due to the excellent conductivity of MXene, which enhances electron transfer. Compared with NS-MXene / rGSPE, NS-TiO2@MX-HG / rGSPE shows significantly higher peak current, indicating an increase in the number of electrochemically active sites. Among the different electrodes, NS-TiO2@MX-HG / rGSPE has the smallest ΔE p and the highest peak current, indicating the fastest electron transfer rate and the highest active site density.

[0087] Figure 4 Based on the AA / UA / DA sensing of the flexible electrochemical sensor prepared for the present application, the electrochemical performance of the rGSPE electrodes modified with different materials for detecting AA, UA and DA was evaluated using cyclic voltammetry. As shown in FIG. 7, Figure 4As shown, in the mixture containing 25 μM AA, 10 μM UA and 15 μM DA, neither rGSPE nor NS-M / rGSPE has obvious peaks. The NS-HG / SPE detects a peak at 0.02 V, corresponding to AA, with a current of 11.6 μA. Notably, NS-TiO2@M-HG / rGSPE exhibits three obvious peaks at -0.048, 0.1 and 0.3 V, corresponding to AA, UA and DA, respectively, with peak currents significantly higher than those of other electrodes. This result demonstrates the excellent electrocatalytic performance of NS-TiO2@M-HG / rGSPE and its ability to effectively distinguish between the three.

[0088] The electrochemical performance of the devices prepared above was tested using an electrochemical station CHI650E (Shanghai Chenhua Instrument Co., Ltd.), and the relevant data are shown in Table 1.

[0089] Table 1

[0090]

[0091] Comparing the experimental results of Examples 1-4, it can be seen that Example 4 has the smallest potential difference, with a potential difference of 0.088 V, which is much lower than the potential differences of other materials, indicating better electron transfer performance. The electrode has the largest k0, which has better electron transfer performance. And it has good selectivity for AA, UA and DA.

[0092] Comparing the experimental results of Example 4 and Comparative Example 1, it can be seen that MXene has high conductivity to ensure fast electron flow. At the same time, TiO2 nanoparticles enhance the electrocatalytic ability by virtue of their own structure and activity, improving the detection sensitivity and response speed. Porous HGO can not only capture and adsorb ions, but also shorten the electron transfer path, achieving efficient promotion of ion and electron transfer. In addition, the introduction of additional elements N and S through special doping creates more active sites inside and outside the material. Without the addition of Mxene, HGO, N and S, the potential difference of the sensor is large, the electron transfer rate is small, and it has no selectivity for AA, UA and DA.

[0093] Comparing the experimental results of Example 4 and Comparative Example 2, it can be seen that porous HGO can not only capture and adsorb ions, but also shorten the electron transfer path, achieving efficient promotion of ion and electron transfer. Doping introduces additional elements N and S, creating more active sites inside and outside the material. Without the addition of Mxene, the sensor has no selectivity for AA, DA and UA, the potential difference increases, but the conductivity is small.

[0094] Comparing the experimental results of Example 4 and Comparative Example 3, it can be seen that MXene has high conductivity to ensure fast electron circulation. At the same time, additional elements N and S are introduced by doping to create more active sites inside and outside the material. Without the addition of HGO, the electron transfer path is increased, and the sensor only responds to AA.

[0095] It should be noted that the scope of protection of the present application is not limited to the embodiments given in the present application file, and all prior art, including but not limited to prior patent documents, prior published publications, prior public use, etc., which are not contradictory to the scheme of the present application, can be included in the scope of protection of the present application.

[0096] In addition, the combination of various technical features in the present case is not limited to the combination mode recorded in the claims of the present case or the combination mode recorded in the specific embodiments. All technical features recorded in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0097] The above description of the embodiments is for the convenience of the ordinary skilled person in the art to understand and use the application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art within the scope of the present application should be within the scope of protection of the present application.

Claims

1. Use of a high-sensitivity flexible electrochemical sensor for in situ detection of biomarkers in sweat, characterized in that, The biomarkers are ascorbic acid, uric acid and dopamine; The flexible electrochemical sensor is prepared by the following steps: S1, ultrasonic mix HGO solution and MXene solution sufficiently, then add thiourea powder, continue ultrasonic, then transfer into a reaction kettle to carry out hydrothermal reaction, centrifugal washing, then re-disperse into deionized water to obtain NS-TiO2@MX-HG solution; S2, mix rGO powder and carbon ink to obtain chemically reduced graphene oxide modified ink material, then prepare working electrode on PET substrate by silk screen printing technology, dry to obtain chemically reduced graphene oxide modified silk screen printed electrode rGSPE; S3, coat NS-TiO2@MX-HG solution obtained in S1 on the silk screen printed electrode rGSPE in S2 to obtain composite electrode NS-TiO2@M-HG / SPE, which is the flexible electrochemical sensor; In S1, the mass ratio of HGO, MXene and thiourea is 1:(0.5-3):(1-10). In S1, the temperature of hydrothermal reaction is (150-250) ℃, and the time is (8-16) h.

2. The use of a high sensitivity flexible electrochemical sensor according to claim 1, characterized in that, In S1, the MXene solution is prepared by liquid etching method; the HGO solution is prepared by first preparing GO by Hammer method, and then etching GO by H2O2.

3. The use of a high sensitivity flexible electrochemical sensor according to claim 1, characterized in that, In S2, the mass ratio of rGO powder and carbon ink is (1-3):

5.

4. The use of a high sensitivity flexible electrochemical sensor according to claim 1, characterized in that, In S3, the concentration of the NS-TiO2@MX-HG solution is 1.2-1.8 mg / mL, and the coating amount thereof is (3-12) μL / 6 mm 2 .

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