Cu-BTC / CNT-cellulose conductive hydrogel for ascorbic acid detection and its preparation method

Abstract

This invention relates to the field of sensing materials technology, specifically disclosing a cellulose-based conductive hydrogel material for ascorbic acid detection, its preparation method, and its applications. This hydrogel uses TEMPO oxidized cellulose nanofibers (TOCNF) as a biocompatible matrix. By introducing Cu-BTC / CNT composite nanoparticles, a three-dimensional conductive network with both high electrochemical activity and structural stability is constructed. While retaining the biocompatibility and flexibility of cellulose, it exhibits particularly high sensitivity and selectivity in detecting small biomolecules such as ascorbic acid, with short response time and good stability. This method achieves synergistic optimization of the composite material's structural uniformity and functionality without relying on complex molding processes. Experimental results show that the conductive hydrogel prepared by this invention possesses good mechanical properties and biocompatibility, exhibiting high sensitivity and stability in biosensing fields such as ascorbic acid detection, providing a novel high-performance material basis for flexible biosensors.

Description

Technical Field

[0001] This invention belongs to the field of cellulose functionalization, specifically relating to a Cu-BTC / CNT-cellulose conductive hydrogel material for ascorbic acid detection and its preparation method. Background Technology

[0002] With the advancement of flexible electronics and bioelectronics technologies, the demand for sensing materials in the field of biosensing is becoming increasingly urgent, as they combine high sensitivity, excellent biocompatibility, and good mechanical flexibility. Traditional conductive hydrogels often struggle to strike a balance between electrochemical activity, structural stability, and biocompatibility.

[0003] Cellulose, as a renewable and biocompatible natural polymer, is an ideal substrate for constructing biosensing platforms. However, pure cellulose hydrogels suffer from poor conductivity due to the lack of conductive active sites, making efficient signal transmission difficult. Although TEMPO oxidized cellulose nanofibers (TOCNF) improve the stability of the material, the introduction of a single conductive filler often results in uneven dispersion and limited functionality. Therefore, developing a cellulose-based sensing hydrogel material with a highly efficient electron transport network and a simple preparation process is of significant technical importance. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a cellulose-based biosensing hydrogel material and its preparation method, aiming to optimize the conductive network and sensing performance of the hydrogel by introducing a Cu-BTC / CNT composite system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of this invention is to provide a method for preparing a cellulose-based biosensing hydrogel material, comprising the following steps:

[0007] S1. Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol to obtain solution A; trimellitic acid was dissolved in anhydrous methanol to obtain solution B; carbon nanotubes were dispersed in deionized water to obtain solution C; solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 24-48 h; the reaction product was washed and dried to obtain Cu-BTC / CNT composite nanoparticles;

[0008] S2. Preparation of nanocellulose suspension: Dilute TOCNF suspension gel with deionized water to obtain a diluted solution of 1 mg / ml to 8 mg / ml, sonicate for 15 min to 30 min, and stir at 500 rpm to 800 rpm for 18 h to 24 h to obtain a uniformly dispersed nanocellulose suspension solution D.

[0009] S3. Preparation of composite solution: Add the Cu-BTC / CNT composite nanoparticles obtained in step S1 to the solution D obtained in step S2, and disperse by ultrasonication to obtain composite solution E;

[0010] S4. Initiate cross-linking: Add acrylamide and potassium persulfate sequentially to solution E obtained in step S3, and sonicate at room temperature for 30-50 seconds to obtain cross-linked mixed solution F;

[0011] S5. Degassing treatment: The composite solution F obtained in step S4 is placed in a vacuum drying oven to remove air bubbles and oxygen, and a uniform precursor liquid G is obtained.

[0012] S6. Thermal polymerization: The uniform precursor liquid G obtained in step S5 is placed in an oven at 60℃~80℃ for 10min~30min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0013] Furthermore, in step S1, the mass ratio of copper nitrate trihydrate to polyvinylpyrrolidone is 2:1, and the concentration is 10 mg / ml to 60 mg / ml.

[0014] Furthermore, the concentration of pyromellitic acid is 5 mg / ml to 12 mg / ml.

[0015] Furthermore, the amount of carbon nanotubes added is 2.5% to 10% of the mass of copper nitrate trihydrate.

[0016] Furthermore, in step S3, the amount of acrylamide added is 10% to 30% of the TOCNF suspension.

[0017] Furthermore, in step S4, the amount of Cu-BTC / CNT composite nanoparticles added is 1% to 5% of the TOCNF suspension.

[0018] Furthermore, the amount of potassium persulfate added is 0.5% to 5% of the TOCNF suspension.

[0019] A second aspect of the present invention is to provide a cellulose-based biosensing hydrogel material prepared by the above method.

[0020] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0021] (1) This invention relates to the field of sensing materials technology, specifically disclosing a Cu-BTC / CNT-cellulose conductive hydrogel material for ascorbic acid detection, its preparation method, and its application. This hydrogel uses TEMPO oxidized cellulose nanofibers (TOCNF) as a biocompatible matrix. By introducing in-situ synthesized Cu-BTC / CNT composite nanoparticles, a three-dimensional conductive network with both high electrochemical activity and structural stability is constructed. While retaining the biocompatibility and flexibility of cellulose, the electrochemical activity and sensing sensitivity of the material are significantly improved. In particular, it exhibits high sensitivity and high selectivity in detecting small biological molecules such as ascorbic acid, with a short response time and good stability.

[0022] (2) The electrocatalytic redox reaction between Cu-BTC and ascorbic acid is the core chemical mechanism for the sensor to generate the detection signal. The chemical oxidation reaction of ascorbic acid (AA), which is difficult to measure directly and efficiently, is transformed into an easily occurring Cu(I) electrooxidation reaction, thus achieving highly sensitive, selective, and rapid electrochemical detection of ascorbic acid. Ascorbic acid molecules in solution rapidly diffuse and penetrate into the material through the hydrophilic network of the hydrogel. Due to its porosity and high specific surface area, ascorbic acid molecules are efficiently adsorbed onto the copper active sites of Cu-BTC, especially with… They interact with each other.

[0023] (3) The adsorbed ascorbic acid undergoes chemical oxidation on the Cu-BTC surface. Cu(II), acting as an electron acceptor, directly strips electrons from the enediol structure of the ascorbic acid molecule, oxidizing it to dehydroascorbic acid, while Cu(II) itself is reduced to Cu(I). The chemical equation can be simplified to: Cu(II)-BTC + ascorbic acid → Cu(I)-BTC + dehydroascorbic acid + H+ + This is the chemical trigger point for signal generation. Under the applied detection potential, Cu(I)-BTC generated inside the material undergoes electrochemical oxidation at the hydrogel interface, reverting to Cu(II)-BTC and releasing an electron. The electrode reaction is: Cu(I)-BTC → Cu(II)-BTC + e - The released electron (e - The CNTs are the direct source of detectable electrical signals. The released electrons do not "stay in place." They are immediately captured by the CNT network, which is in close contact with the Cu-BTC. As excellent conductors, the CNTs transmit these electrons at high speed and without loss to the external electrodes and the workstation.

[0024] (4) The preparation method of this invention uses water as the main solvent system in key steps. By rationally controlling the organic solvent, the emission of volatile organic compounds and the burden of waste liquid treatment during the production process are significantly reduced. This method significantly reduces the environmental impact of the process while ensuring controllable synthesis of material properties, reflecting the technical characteristics of green preparation. Attached Figure Description

[0026] Figure 1 The images show SEM images of the Cu-BTC / CNT composite nanoparticles prepared in Examples 1-4 of this invention.

[0027] Figure 2 SEM image of the cellulose-based biosensing hydrogel prepared in Example 1 of the present invention.

[0028] Figure 3 This is a comparison chart of the impedance value and ionic conductivity of the hydrogels prepared in Examples 1 to 4 of the present invention.

[0029] Figure 4 This is a comparison chart of the impedance value and ionic conductivity of the hydrogels prepared in Examples 5 to 7 of the present invention.

[0030] Figure 5 The linear relationship between the impedance value and ascorbic acid concentration of the hydrogel prepared in Example 7 of the present invention under various mixed electrolytes. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments and accompanying drawings are described in further detail below. Where specific test methods, instruments, or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0033] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, the preparation method of which includes the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 1 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 2.5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0035] Example 2: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, prepared by the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 2.5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0036] Example 3: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, prepared by the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 3 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 2.5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0037] Example 4: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, the preparation method of which includes the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 4 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 2.5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0038] Example 5: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, prepared by the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 1.25% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0039] Example 6: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, the preparation method of which includes the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 3.74% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0040] Example 7: A Cu-BTC / CNT-cellulose conductive hydrogel (Cu-MOF / CNT@TOCNF) for ascorbic acid detection, the preparation method of which includes the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution D obtained in step (2) and dispersed by ultrasonication to obtain composite solution E; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution E obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution F; (5) Degassing treatment: The composite solution F obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid G is obtained. (6) Thermal polymerization: The uniform precursor liquid G obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

[0041] Comparative Example 1: A cellulose-based hydrogel (Cu-MOF@TOCNF), prepared by the following steps: (1) Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol at a mass ratio of 2:1 to prepare a solution A of 24 mg / ml; Tristyric acid was dissolved in anhydrous methanol to prepare a solution B of 8.8 mg / ml; 0.15 g of carbon nanotubes were dispersed in deionized water to obtain solution C; Solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 48 h. The mixture was washed 2 to 3 times with deionized water, and the washed product was dried in a vacuum oven at 60 °C for 12 h to obtain Cu-BTC / CNT composite nanoparticles; (2) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution A. (3) Preparation of composite solution: Cu-BTC / CNT composite nanoparticles obtained in step (1) are added to solution A obtained in step (2) and dispersed by ultrasonication to obtain composite solution B; wherein the amount of Cu-BTC / CNT composite nanoparticles added is 5% of the TOCNF suspension; (4) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution B obtained in step (3) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution C; (5) Degassing treatment: The composite solution C obtained in step (4) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid D is obtained. (6) Thermal polymerization: The uniform precursor liquid D obtained in step (5) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain Cu-MOF@TOCNF hydrogel.

[0042] Comparative Example 2: A cellulose-based hydrogel (CNT@TOCNF), prepared by the following steps: (1) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution A; (2) Preparation of composite solution: Carbon nanotubes (CNTs) are added to solution A obtained in step (1) and dispersed by ultrasonication to obtain composite solution B; wherein the amount of carbon nanotubes added is 5% of the TOCNF suspension; (3) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution B obtained in step (2) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution C; (4) Degassing treatment: The composite solution C obtained in step (3) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid D is obtained. (5) Thermal polymerization: The uniform precursor liquid D obtained in step (4) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain CNT@TOCNF hydrogel.

[0043] Comparative Example 3: A cellulose-based hydrogel (TOCNF), prepared by the following steps: (1) Preparation of nanocellulose suspension: TOCNF suspension gel was diluted with deionized water to obtain a 2 mg / ml diluted solution, which was ultrasonicated for 15 min and stirred at 500 rpm for 24 h to obtain a uniformly dispersed nanocellulose suspension solution A. (2) Initiating cross-linking: Add 20% acrylamide and 0.6% potassium persulfate of TOCNF suspension to solution A obtained in step (1) in sequence, and sonicate at room temperature for 50s to obtain cross-linked mixed solution C; (3) Degassing treatment: The composite solution C obtained in step (2) is placed in a vacuum drying oven to remove bubbles and oxygen, and a uniform precursor liquid D is obtained; (4) Thermal polymerization: The uniform precursor liquid D obtained in step (3) is placed in an oven at 60°C for 20 min for thermal polymerization reaction to obtain pure TOCNF hydrogel.

[0044] The microstructure of the Cu-BTC / CNT composite nanoparticles prepared in Examples 1-7 was characterized using scanning electron microscopy (SEM).

[0045] refer to Figure 1 The figures show the Cu-BTC / CNT composite nanoparticles prepared in Examples 1-4. As can be seen from the figures, Cu-BTC in the Cu-BTC / CNT composite nanoparticles exhibits an octahedral structure, and carbon nanotubes are wrapped around the surface of Cu-BTC.

[0046] refer to Figure 2 The hydrogel prepared in Example 1 was cut after being cooled and dried, and its surface morphology was observed using a scanning electron microscope. The figure shows that the hydrogel prepared in Example 1 has a uniform and dense pore size.

[0047] refer to Figure 3 The figures show the hydrogels prepared in Examples 1-4; as can be seen from the figures, the hydrogels prepared using a 1 mg / ml TOCNF suspension have an ionic conductivity of 4.87 mS / cm. -1 The hydrogel prepared using a 2 mg / ml TOCNF suspension had an ionic conductivity of 6.36 mS / cm. -1 The hydrogel prepared using a 3 mg / ml TOCNF suspension had an ionic conductivity of 3.46 mS / cm. -1 The hydrogel prepared using a 4 mg / ml TOCNF suspension had an ionic conductivity of 0.97 mS / cm. -1 The hydrogel prepared using a 2 mg / ml TOCNF suspension exhibited the highest ionic conductivity, significantly higher than the other three materials.

[0048] refer to Figure 4 The figures show the hydrogels prepared in Examples 5-7. As can be seen from the figures, when using a 2 mg / ml TOCNF suspension, the hydrogel prepared with Cu-BTC / CNT composite nanoparticles at 1.25% of the TOCNF suspension exhibits an ionic conductivity of 5.26 mS / cm. -1 A hydrogel prepared by adding Cu-BTC / CNT composite nanoparticles at 2.5% of the TOCNF suspension had an ionic conductivity of 6.34 mS / cm. -1 A hydrogel prepared by adding Cu-BTC / CNT composite nanoparticles at 3.74% of the TOCNF suspension had an ionic conductivity of 4.87 mS / cm. -1A hydrogel prepared by adding Cu-BTC / CNT composite nanoparticles at 5% of the TOCNF suspension had an ionic conductivity of 11.48 mS / cm. -1 The hydrogel prepared by adding Cu-BTC / CNT composite nanoparticles at 5% of the TOCNF suspension exhibited the highest ionic conductivity, significantly higher than the other three materials.

[0049] refer to Figure 5 The samples were hydrogels prepared in Example 7. The phosphate buffer solution concentration in each electrolyte sample was 0.1 mol / L, while the ascorbic acid solution concentrations were 20 μmol / L, 40 μmol / L, 60 μmol / L, 80 μmol / L, and 100 μmol / L, respectively. The linear relationship between the impedance value of the hydrogel and the ascorbic acid concentration under each mixed electrolyte was obtained.

Claims

1. A method for preparing a Cu-BTC / CNT-cellulose conductive hydrogel material for ascorbic acid detection, characterized in that, Includes the following steps: S1. Preparation of Cu-BTC / CNT composite nanoparticles: Copper nitrate trihydrate and polyvinylpyrrolidone were dissolved in anhydrous methanol to obtain solution A; trimellitic acid was dissolved in anhydrous methanol to obtain solution B; carbon nanotubes were dispersed in deionized water to obtain solution C; solution A and solution C were mixed and stirred, and then solution B was added dropwise to the mixture and stirred at room temperature for 24-48 h; the reaction product was washed and dried to obtain Cu-BTC / CNT composite nanoparticles; S2. Preparation of nanocellulose suspension: Dilute TOCNF suspension gel with deionized water to obtain a diluted solution of 1 mg / ml to 8 mg / ml, sonicate for 15 min to 30 min, and stir at 500 rpm to 800 rpm for 18 h to 24 h to obtain a uniformly dispersed nanocellulose suspension solution D. S3. Preparation of composite solution: Add the Cu-BTC / CNT composite nanoparticles obtained in step S1 to the solution D obtained in step S2, and disperse by ultrasonication to obtain composite solution E; S4. Initiate cross-linking: Add acrylamide and potassium persulfate sequentially to solution E obtained in step S3, and sonicate at room temperature for 30-50 seconds to obtain cross-linked mixed solution F; S5. Degassing treatment: The composite solution F obtained in step S4 is placed in a vacuum drying oven to remove air bubbles and oxygen, and a uniform precursor liquid G is obtained. S6. Thermal polymerization: The uniform precursor liquid G obtained in step S5 is placed in an oven at 60℃~80℃ for 10min~30min for thermal polymerization reaction to obtain the cellulose-based biosensing hydrogel material.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of copper nitrate trihydrate to polyvinylpyrrolidone is 2:1, and the concentration is 10 mg / ml to 60 mg / ml.

3. The preparation method according to claim 2, characterized in that, The concentration of the pyromellitic acid is 5 mg / ml to 12 mg / ml.

4. The preparation method according to claim 3, characterized in that, The amount of carbon nanotubes added is 2.5% to 10% of the mass of copper nitrate trihydrate.

5. The preparation method according to claim 4, characterized in that, In step S3, the amount of acrylamide added is 10% to 30% of the TOCNF suspension.

6. The preparation method according to claim 4, characterized in that, In step S4, the amount of Cu-BTC / CNT composite nanoparticles added is 1% to 5% of the TOCNF suspension.

7. The preparation method according to claim 8, characterized in that, The amount of potassium persulfate added is 0.5% to 5% of the TOCNF suspension.

8. A cellulose-based biosensing hydrogel material, characterized in that, It is prepared according to any one of claims 1-9.

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