A composite material, electrochemical sensor, method of preparation and use

Abstract

The application belongs to the technical field of electrochemical detection, and relates to a composite material, an electrochemical sensor, a preparation method and application. The application provides a multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material which is composed of carboxylated multi-walled carbon nanotubes, polyvinyl alcohol and phosphotungstic acid. In the composite material, the phosphotungstic acid is complexed with the polyvinyl alcohol through hydrogen bond action to form a stable hydrogel framework, and important problems such as poor film adhesion and unstable sensing characteristics of the multi-walled carbon nanotube / polyvinyl alcohol composite material are solved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical detection technology, and relates to a composite material, an electrochemical sensor, a preparation method, and its application. Background Technology

[0002] In the biomedical field, particularly for the rapid detection of pathogens, the development of efficient, sensitive, and easy-to-use detection technologies is crucial. Pseudomonas aeruginosa (PA), a common Gram-negative pathogen, frequently infects patients with diabetic foot fibrosis (DFT), diabetic foot, and immunocompromised patients, posing a serious threat to public health. Pseudomonas aeruginosa (PCN), a characteristic biomarker of PA secretion, is essential for timely diagnosis and infection control. However, traditional detection methods such as high-performance liquid chromatography (HPLC) and spectrophotometry, while accurate, are complex and time-consuming, failing to meet the needs of rapid clinical and field testing.

[0003] In recent years, electrochemical sensors have shown great potential in the field of biosensing due to their advantages such as fast response, high sensitivity, and low cost. Carbon nanotubes (CNTs), especially multi-walled carbon nanotubes (MWCNTs), have become ideal materials for constructing high-performance electrochemical sensing interfaces due to their excellent electronic conductivity and large specific surface area. MWCNTs / PVA composites formed by combining CNTs and polyvinyl alcohol (PVA) not only inherit the conductivity and stability of MWCNTs, but also further broaden their application range in biosensing through the excellent film-forming properties and biocompatibility of PVA. However, the application of MWCNTs / PVA in electrochemical sensors still faces many challenges. Stability issues: MWCNTs are not firmly fixed on conductive substrates and are prone to detachment, leading to unstable sensor performance and affecting long-term reliability. Insufficient adhesion: Although PVA hydrogel has good biocompatibility, its adhesion to smooth conductive substrates is weak, especially in humid environments, where it is prone to swelling and peeling, severely limiting the practical application of sensors. Sensing performance needs improvement: Sensors built solely using MWCNTs / PVA composite materials still have room for improvement in terms of sensitivity, detection range, and anti-interference capabilities, making it difficult to meet the high-precision detection requirements in complex biological systems. Summary of the Invention

[0004] To overcome the aforementioned challenges, this invention proposes a MWCNTs / PVA / PTA composite material, and uses this material as a conductive hydrogel coated on a conductive electrode to construct a high-performance electrochemical sensor. Phosphotungstic acid (PTA), as a polyoxometalate (POM), possesses a unique Keggin structure and abundant oxygen atom bonding, enabling it to form strong hydrogen bonds with PVA, effectively reducing the crystallinity of PVA and thus enhancing the adhesion between the hydrogel and the conductive substrate. Simultaneously, the introduction of PTA optimizes the conductive network structure, increases the number of accessible active sites, and further improves the sensor's sensitivity and stability.

[0005] On one hand, the present invention relates to a multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material, which is composed of carboxylated multi-walled carbon nanotubes, polyvinyl alcohol and phosphotungstic acid.

[0006] In the composite material method provided by this invention, the ratio of carboxylated multi-walled carbon nanotubes (MWCNTs) to polyvinyl alcohol (PVA) is not particularly limited. Depending on the electrochemical detection target, those skilled in the art can adjust the mass ratio of MCCNTs to PVA as needed to achieve suitable conductivity and mechanical strength. Generally, a mass ratio of MCCNTs to PVA of 0.01 to 0.5:1 is suitable for electrochemical detection and exhibits good conductivity and mechanical strength.

[0007] This invention improves the adhesion, sensitivity, and stability of MWCNTs / PVA composite materials in electrochemical sensors by introducing phosphotungstic acid to form a suitable structure with polyvinyl alcohol. Those skilled in the art can select an appropriate mass ratio of carboxylated multi-walled carbon nanotubes to polyvinyl alcohol based on the different electrochemical detection targets, and then add phosphotungstic acid to achieve a mass ratio of 10-60% for polyvinyl alcohol to phosphotungstic acid, thus obtaining a suitable multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material.

[0008] Furthermore, in the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material provided by the present invention, the mass ratio of carboxylated multi-walled carbon nanotubes, polyvinyl alcohol and phosphotungstic acid is 0.2:1:1~5.

[0009] On the other hand, the present invention relates to a method for preparing the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material, comprising: dispersing carboxylated multi-walled carbon nanotubes in an aqueous solution containing SDS, adding polyvinyl alcohol and heating to dissolve to form a solution, and adding phosphotungstic acid after cooling to form a composite hydrogel.

[0010] On the other hand, the present invention relates to the application of the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material in improving the performance of electrochemical sensors, wherein the performance is at least one of sensitivity, anti-interference, stability and reproducibility.

[0011] Furthermore, in the applications provided by this invention, the anti-interference capability refers to the ability of the electrochemical sensor to operate stably in various complex electrolyte environments.

[0012] Furthermore, in the applications provided by this invention, the various complex electrolyte environments include PBS, LB broth, and artificial saliva.

[0013] On the other hand, the present invention relates to an electrochemical sensor including a working electrode, the surface of which is coated with the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material.

[0014] On the other hand, the present invention relates to an electrochemical sensor for the detection of pyocyanin, comprising a working electrode, the surface of which is coated with the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite material.

[0015] Furthermore, in the electrochemical sensor for Pseudomonas aeruginosa detection provided by the present invention, the electrochemical sensor for Pseudomonas aeruginosa detection has a linear detection range of 5~100 μM / L for Pseudomonas aeruginosa, and a detection limit as low as 1.63 μM / L.

[0016] On the other hand, the present invention relates to the application of phosphotungstic acid in improving the properties of multi-walled carbon nanotube / polyvinyl alcohol composite hydrogels, wherein the mass ratio of polyvinyl alcohol to phosphotungstic acid is 1:1 to 5; the incorporation of phosphotungstic acid improves at least one of the following in the multi-walled carbon nanotube / polyvinyl alcohol composite hydrogel: crystallinity of polyvinyl alcohol, adhesion ability, and number of accessible active sites.

[0017] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0018] The adhesiveness of hydrogels can be improved through surface modification, bridging polymers, topological adhesion, and the incorporation of nanomaterials. The first three methods involve inserting an interlayer between the hydrogel and the substrate, forming a strong adhesive sandwich structure through the interlayer's action. However, this does not improve the direct adhesion ability of the hydrogel, and the addition of the interlayer material reduces biocompatibility and limits the application environment (such as pH and temperature). In contrast, nanoparticles work by complexing their surface functional groups with polymers, altering the polymer structure and fragment dynamics, such as reducing the crystallinity of the hydrogel, thus achieving a tight bond with the substrate. Furthermore, nanoparticle-composite hydrogels can improve conductivity, magnetic properties, and antibacterial properties, expanding the application of hydrogels in sensing. Polyoxometalates (POMs) are nanoscale metal oxide clusters. Phosphotungstic acid (PTA) has a typical Keggin structure, where oxygen atoms have various bonding modes. It can form hydrogen bonds with polyvinyl alcohol (PVA), an ideal hydrogel material, reducing PVA crystallinity, weakening the internal stress during film curing, and promoting a strong adhesive structure with the substrate. Therefore, this invention solves the above problems by constructing a self-assembled MWCNTs / PVA / PTA composite material, which acts as a conductive hydrogel, and an electrochemical sensor based on this material was prepared. The MWCNTs / PVA / PTA sensor can achieve linear detection of PCN concentrations in the range of 5-100 μM / L in various electrolyte environments, with a detection limit (LOD) as low as 1.67 μM / L. Furthermore, the sensor exhibits certain anti-interference properties, stability, and reproducibility. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 SEM images and elemental distribution maps of different composite materials are shown. AB represents the SEM image of MWCNTs; CD represents the SEM image of MWCNTs / PVA; EF represents the SEM image of MWCNTs / PVA / PTA4; GH represents the SEM image of MWCNTs / PVA / PTA8; and I represents the elemental mapping image of MWCNTs / PVA / PTA4.

[0021] Figure 2 These are three-dimensional and two-dimensional AFM images of the electrochemical sensor. In this image, A represents MWCNTs / PVA; B represents MWCNTs / PVA / PTA4; and C represents MWCNTs / PVA / PTA8.

[0022] Figure 3 These are the FT-IR test results for the electrochemical sensor. Where A represents the FTIR of the electrochemical sensor; B represents the WAXS of the electrochemical sensor; and C represents the I(q) of the electrochemical sensor. 1 / 2 -q 2 Curve; D is the C 1s XPS spectrum of MWCNTs / PVA; E is the O 1s XPS spectrum of MWCNTs / PVA; F is the W 4f XPS spectrum of MWCNTs / PVA; G is the C 1s XPS spectrum of MWCNTs / PVA4; H is the O 1s XPS spectrum of MWCNTs / PVA4; I is the W 4f XPS spectrum of MWCNTs / PVA4.

[0023] Figure 4 Square wave voltammetry (SWV) was used to evaluate the sensor's performance in measuring PCN concentration in different electrolyte environments. A represents the SWV current response of PCN in PBS medium (5-100 μM); B represents the SWV current response of PCN in LB medium (10-100 μM); C represents the SWV current response of PCN in artificial saliva medium (10-100 μM); D represents the calibration curves for the three media, with error bars indicating the standard deviation between three repeated measurements; E represents the SWV current response and peak potential of PCN in PBS at different pH values; and F represents the SWV current response of PA medium supernatant (including PCN).

[0024] Figure 5 Stability testing of MWCNTs / PVA / PTA composites. A represents the selective SWV reaction of MWCNTs / PVA / PTA4 to 50 µM PCN under the same concentration of interference; B represents the stability of MWCNTs / PVA / PTA4 with 50 µM PCN; and C represents the reproducibility of MWCNTs / PVA / PTA4 prepared from different batches of hydrogel.

[0025] Figure 6 This section compares the peak current of electrochemical sensors with different modified materials. Where A represents MWCNTs; B represents MWCNTs / PVA; and C represents MWCNTs / PVA / PTA4.

[0026] Figure 7OM images of the electrochemical sensor surface were prepared after different time periods. A represents MWCNTs modification for 1 day; B represents MWCNTs / PVA modification for 1 day; C represents MWCNTs / PVA / PTA4 modification for 1 day; D represents MWCNTs / PVA / PTA4 modification for 2 days; E represents MWCNTs / PVA / PTA4 modification for 3 days; and F represents MWCNTs / PVA / PTA4 modification for 4 days. Detailed Implementation

[0027] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially. Unless otherwise specified, the percentages in the following embodiments refer to mass percentages.

[0028] Example 1

[0029] This embodiment provides the fabrication of MWCNTs / PVA / PTA composite materials and electrochemical sensors.

[0030] Raw materials: Carboxylated multi-walled carbon nanotubes, purchased from Jiangsu Xianfeng Nanotechnology Co., Ltd., China; sodium decaalkyl sulfate (SDS), polyvinyl alcohol (PVA, degree of hydrolysis 99%), phosphotungstic acid hydrate (PTA, H3O) 40 PW 12 xH2O and pyocyanin (PCN, CRS) were purchased from Aladdin Chemical Reagent Co., Ltd., China. All solutions were prepared using Milli-Q grade water (Z18 MΩ, Milli-Q, Millipore, Billerica, MA) for a water purification system.

[0031] 0.01-0.5 g of carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs) were dispersed in 10 mL of LDS aqueous solution. After high-speed stirring for 30 min and ultrasonic treatment, a series of uniformly dispersed MWCNTs of varying concentrations were prepared. Then, 0.02-1 g of PVA was added to the dispersion, and the mixture was stirred in a water bath at 95 °C for 1 h to ensure complete dissolution of PVA. PTA was then added, and the mixture was stirred continuously at the same speed for 30-180 min. MWCNTs / PVA / PTA composite hydrogels with different PTA ratios were successfully prepared according to the amount of PTA added. With increasing PTA content, the prepared samples were labeled MWCNTs / PVA / PTA2, MWCNTs / PVA / PTA4, MWCNTs / PVA / PTA8, and MWCNTs / PVA / PTA10, respectively. The mass ratios of carboxyl polar group-functionalized MWCNTs, polyvinyl alcohol, and phosphotungstic acid are 0.2:1:1, 0.2:1:2, 0.2:1:4, and 0.2:1:5, respectively. In the following examples, unless otherwise stated, MWCNTs / PVA / PTA composite materials refer to MWCNTs / PVA / PTA4 composite materials.

[0032] Electrochemical performance measurements were performed on the CHI660E electrochemical workstation (China Chenhua Instrument Co., Ltd.). The traditional three-electrode battery contained 1 voltammetric phosphate buffer (PBS, pH 7.3), Ag / AgCl as the reference electrode, and a platinum electrode as the counter electrode.

[0033] Take 5 μL of the above composite hydrogel and drop it onto the pre-cleaned 0.5 cm × 0.5 cm ITO working electrode surface. After natural drying at room temperature, perform a freeze-thaw cycle. The resulting sensor can be used for the next electrochemical test.

[0034] Example 2

[0035] This embodiment provides a performance comparison of three composite materials—MWCNTs, MWCNTs / PVA, and MWCNTs / PVA / PTA—in electrochemical sensors.

[0036] Raw material: Pseudomonas aeruginosa (PCN) is purified from Pseudomonas aeruginosa (PA).

[0037] Sensors prepared with MWCNT dispersions exhibited uneven, blocky material detachment during testing; MWCNTs / PVA sensors also showed detachment after the composite membrane absorbed water and swelled. For example... Figure 6 As shown, neither of these two sensors can achieve accurate detection of PCN.

[0038] Two important issues were identified regarding the prepared MWCNTs / PVA / PTA hydrogels. Firstly, the hydrogel film state showed a significant correlation with the number of days it was left to stand. Omnimetry revealed that films prepared by drop-casting hydrogels left to stand for one and two days exhibited significant aggregation; however, the aggregation was significantly improved after standing for more than three days. Figure 7 Secondly, the stability of the MWCNTs / PVA / PTA hydrogel film is closely related to the PTA content. Based on the above phenomena, this study first investigated the effects of the hydrogel's settling days, the introduction of PTA stabilizer, and the number of freeze-thaw cycles on the sensor and their related mechanisms. Figure 7 As shown in Figure A, the response current of the sensor prepared by hydrogel after standing for 4 days or more tends to be stable, and no aggregation is observed on the surface.

[0039] Example 3

[0040] This embodiment provides an analysis of the electrode adhesion mechanism of three composite materials: MWCNTs, MWCNTs / PVA, and MWCNTs / PVA / PTA.

[0041] SEM observations of electrode surface morphology for different material systems are as follows: Figure 1 As shown. Figure 1 C and Figure 1 As shown in D, compared to MWCNTs, whose surface is composed of a large number of aggregated and intertwined strip-shaped carbon nanotubes ( Figure 1 A and Figure 1 (B) The MWCNTs / PVA surface is smooth, and film formation is clearly observed, proving that PVA physically crosslinks to form a hydrogel during freeze-thaw cycles. Furthermore, the number of CNTs observable on the surface decreases at the same scale, possibly because most CNTs are encapsulated within the hydrogel. Adding different proportions of PTA to the system actually increases the number of surface-growing CNTs. Figure 1 E and Figure 1 F, the film quality on the MWCNTs / PVA / PTA4 surface decreases, with more CNTs exposed on the surface, increasing the number of accessible active sites. From Figure 1 In study I, it was found that CNTs, PTA, and SDS dispersants in the hydrogel were relatively uniformly distributed on the electrode surface. Further increasing the PTA content in the system, such as... Figure 1 G and Figure 1 As shown in H, the CNTs on the surface of MWCNTs / PVA / PTA8 did not continue to increase in the same trend as MWCNTs / PVA / PTA4. Instead, regional aggregation occurred. It is speculated that after the PTA content increased, PTA itself became enriched, causing CNTs to aggregate in this area, resulting in poor surface material uniformity.

[0042] The results of atomic force microscopy (AFM) tests also confirm the above analysis. Figure 2 A shows the surface morphology of MWCNTs / PVA with an Rq of 30.6 nm. The 2D morphology reveals CNTs embedded within the hydrogel. The surface roughness of the materials increased to varying degrees after the addition of PTA. Figure 2 As shown in Figure B, the Rq of MWCNTs / PVA / PTA4 increases to 38.5 nm. The 3D morphology image clearly shows a sharper peak, unlike that of MWCNTs / PVA, while the 2D morphology image shows an increased degree of surface graininess. This is likely due to the reduced crystallinity of PVA after the addition of PTA, which re-exposes the CNTs. Figure 2 C shows the surface morphology of MWCNTs / PVA / PTA8. With the addition of h to PTA, the content doubled, and its Rq increased from 38.5 nm to 50.8 nm. In the 3D morphology image, the sharp small peaks in MWCNTs / PVA / PTA4 were replaced by smooth large peaks. In the 2D morphology image, no exposed CNTs were clearly observed. This is consistent with the phenomenon that PTA itself is enriched in the SEM and causes CNTs to aggregate in this region.

[0043] To better understand the internal state of the three hydrogel systems, FT-IR technology was used. For example... Figure 3 As shown in Figure A, after the introduction of PTA, the infrared spectrum shows 981 and 896 cm⁻¹. -1 W=O appears at this point d Tensile vibration and WO b The two peaks of the -W tensile vibration demonstrate that PTA was successfully introduced into the hydrogel system. The 1215 cm⁻¹ peak... -1 The asymmetric stretching vibration peak belonging to CO gradually decreased with the addition of PTA, proving that PTA hindered the crystallization of PVA during the physical cross-linking process, thus reducing the amount of CO in the conductive hydrogel network.

[0044] The phase separation morphology of the blended films was analyzed using WAXS technology. For example... Figure 3 As shown in Figure B, the characteristic peaks broaden after the addition of PTA. The characteristic scattering peak of MWCNTs / PVA / PTA4 shifts towards the larger q region, indicating that the phase separation size of PTA and PVA decreases after blending, forming a homogeneous blend phase. However, in the MWCNTs / PVA / PTA8 system, the characteristic peaks shift towards the smaller q region, indicating that the phase separation size of PTA and PVA increases, and the two are not well integrated, which is consistent with the SEM findings.

[0045] XPS was used to analyze the surface chemical bond state of electrodes modified with different hydrogel systems. Figure 3The O1s spectrum of E-3H shows typical O=C bonds from the carboxyl group, typical OC bonds from PVA, and typical O=W bonds from PTA appear in the O1s spectrum of MWCNTs / PVA / PTA4. Figure 3 In the W4f spectrum shown in F-3I, no W-related bonding was observed in MWCNTs / PVA. MWCNTs / PVA / PTA4 showed a binding energy peak for WO3 self-orbit splitting, as well as typical WC bonds, indicating that some of the PTA was loaded onto the carbon nanotubes during the PTA anchoring process. This also explains the phenomenon in the AFM results where the PTA self-enrichment process leads to the aggregation of CNTs in its vicinity.

[0046] Example 3

[0047] This embodiment uses square wave voltammetry (SWV) to characterize the sensing performance of an electrochemical sensor made of MWCNTs / PVA / PTA composite material in measuring PCN concentration under different electrolyte environments.

[0048] like Figure 4 As shown in Figure A, when tested in PBS, an oxidation peak appeared at 0.34 V, and its oxidation peak current gradually increased with increasing concentration. Within the ranges of 5 μM to 50 μM and 50 μM to 100 μM, its peak current showed a good linear relationship with the PCN concentration. Figure 4 D), correlation coefficient R 2 The values ​​were 0.997 and 0.999, respectively. The sensor had a LOD of 1.67 µM in PBS, covering a PCN concentration range of 5–100 µM in clinical infections. The standard curve showed a smaller slope at higher concentrations than at lower concentrations, indicating decreased detection sensitivity at high concentrations. PCN is a marker secretion of PA, therefore the same test was performed in the commonly used PA medium, LB broth. Figure 4 As shown in Figure B, the test results in LB broth showed the same trend as those in PBS. The oxidation behavior of PCN was determined at 0.384 V, and the oxidation peak current increased with increasing concentration. The fitting equation was I = 0.13 (C / µM) + 0.7, R0 2 The value was 0.996, and the LOD was 2.71 µM. Since PA colonization is frequently found in sputum due to lung infections, and artificial saliva is the closest sample to sputum, sensing tests were also performed in an artificial saliva environment. Figure 4As shown in Figure C, a PCN oxidation peak was observed at 0.354 V, with a concentration standard curve R² of 0.995 and a LOD of 3.63 µM. However, the sensitivity in LB broth and artificial saliva was lower than that in the PBS environment. This may be because the electrolytes in these two solutions contain proteins and peptides in addition to ions. These biomolecules can affect the adsorption of analytes. Furthermore, the viscosity of artificial saliva is higher than that of the other two electrolytes, which hinders the diffusion of PCN from the electrolyte to the electrode surface. Therefore, saliva has the lowest sensitivity.

[0049] Further testing of MWCNTs / PVA / PTA4 in Na + K + The selectivity of PCN in the presence of various organic and inorganic substances such as AA, Urea, and glucose. Figure 5 As shown in Figure A, when the same concentration of interfering substance is added to a solution containing PCN, the current deviation caused by any interfering substance does not exceed ±10%. This indicates that the developed sensor has good anti-interference capability. To verify the stability and reproducibility of the sensor, sensors prepared on the same day were stored in air for different numbers of days and then tested. On the sixth day, the electrode retained 88.44% of its initial value, indicating that the sensor has long-term stability. Figure 5 B). Sensor reproducibility was investigated using different batches of hydrogels, such as... Figure 5 C. The current response deviation of the hydrogels from five different batches under the same conditions does not exceed ±5%. MWCNTs, PVA, and PTA in the hydrogel system all exhibit high stability in air and are not easily volatilized, resulting in good stability and reproducibility of the sensor.

[0050] This invention provides a MWCNTs / PVA / PTA hydrogel and, for the first time, applies it to the field of biosensing. This invention discloses the mechanism by which PTA modulates the adhesion and sensing sensitivity of the hydrogel. Using the constructed sensor, PCN was detected in various electrolyte environments including PBS, LB, and artificial saliva, with a linear detection range of 5-100 μM / L and a limit of detection of 1.67 μM / L. More importantly, it was found that PTA suppresses the low adhesion of PVA caused by internal stress, promotes the proton transport efficiency in the conductive network, and broadens the application range of the MWCNTs / PVA / PTA sensor for stable testing in various solution environments. Therefore, the MWCNTs / PVA / PTA sensor prepared in this invention has broad application potential for PCN detection, and the proposed mechanism of PVA-PTA composite action opens up more avenues for further in-depth research on composite hydrogel sensing films.

[0051] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite hydrogel, characterized in that, It is composed of carboxylated multi-walled carbon nanotubes, polyvinyl alcohol, and phosphotungstic acid; The mass ratio of carboxylated multi-walled carbon nanotubes, polyvinyl alcohol, and phosphotungstic acid is 0.2:1:1~5.

2. A method for preparing the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite hydrogel as described in claim 1, characterized in that, include: Carboxylated multi-walled carbon nanotubes were dispersed in an aqueous solution containing SDS, polyvinyl alcohol was added and heated to dissolve and form a solution, and phosphotungstic acid was added after cooling to form a composite hydrogel.

3. The application of the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite hydrogel according to claim 1 in improving the performance of electrochemical sensors, characterized in that, The performance is at least one of sensitivity, anti-interference, stability and reproducibility.

4. The application according to claim 3, characterized in that, The anti-interference capability refers to the ability of the electrochemical sensor to operate stably in various complex electrolyte environments.

5. The application according to claim 4, characterized in that, The various complex electrolyte environments include PBS, LB broth, and artificial saliva.

6. An electrochemical sensor, comprising a working electrode, characterized in that, The surface of the working electrode is coated with the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite hydrogel as described in claim 1.

7. An electrochemical sensor for the detection of pyocyanin, comprising a working electrode, characterized in that, The surface of the working electrode is coated with the multi-walled carbon nanotube / polyvinyl alcohol / phosphotungstic acid composite hydrogel as described in claim 1.

8. The electrochemical sensor for Pseudomonas aeruginosa detection according to claim 7, characterized in that, The electrochemical sensor for the detection of pyocyanin has a linear detection range of 5~100 μM / L and a detection limit as low as 1.63 μM / L.

9. The application of phosphotungstic acid in improving the properties of carboxylated multi-walled carbon nanotube / polyvinyl alcohol composite hydrogels, characterized in that, The mass ratio of polyvinyl alcohol to phosphotungstic acid is 1:1~5; the incorporation of phosphotungstic acid improves at least one of the following in the carboxylated multi-walled carbon nanotube / polyvinyl alcohol composite hydrogel: crystallinity of polyvinyl alcohol, adhesion ability, and number of accessible active sites.

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