An ag / UiO-66(zr) composite electrode, a preparation method and application thereof, and an electrochemical system for detecting ascorbic acid

Abstract

This invention provides an Ag / UiO-66(Zr) composite electrode, its preparation method, and applications, as well as an electrochemical system for detecting ascorbic acid, belonging to the field of analytical detection technology. The Ag / UiO-66(Zr) composite electrode provided by this invention includes an electrode substrate and Ag / UiO-66(Zr) coated on the surface of the electrode substrate. In this invention, AgNPs possess high conductivity and electrocatalytic activity, while the UiO-66(Zr) metal-organic framework has high specific surface area and high porosity. By loading AgNPs onto the UiO-66(Zr) surface, this invention overcomes the shortcomings of AgNPs, such as easy aggregation, easy dissolution, and poor adhesion, thereby improving the conductivity and electrocatalytic activity of the composite electrode. Using the Ag / UiO-66(Zr) composite electrode as the working electrode for the electrochemical detection of ascorbic acid in sweat has the advantages of low detection limit and strong anti-interference ability.

Description

Technical Field

[0001] This invention belongs to the field of analytical detection technology, specifically relating to an Ag / UiO-66(Zr) composite electrode, its preparation method and application, and an electrochemical system for detecting ascorbic acid. Background Technology

[0002] Ascorbic acid, also known as vitamin C, is a water-soluble organic compound essential for human metabolism. It cannot be synthesized by the human body and must be obtained from external sources to maintain normal bodily functions. This substance plays a crucial role in human physiological activities, not only promoting bone development and tissue wound healing, but also effectively scavenging free radicals, inhibiting oxidative damage to biomolecules, and maintaining the body's redox balance. Long-term deficiency of ascorbic acid can lead to various health problems such as weakened immunity, slowed tissue repair, and scurvy, seriously affecting physical health and physiological function. Therefore, developing a high-efficiency, real-time, continuous, and non-invasive detection technology for ascorbic acid concentration has significant research value and application prospects for clinical disease monitoring, daily health care, and physiological status assessment.

[0003] Currently, the mainstream methods for detecting ascorbic acid are mainly optical detection techniques such as colorimetry and spectrofluorescence. However, these traditional detection methods have many inherent defects, which greatly limit their accuracy and field application capabilities. First, optical detection equipment is precise and expensive, resulting in high detection costs and cumbersome detection procedures. These typically require complex sample pretreatment, reagent preparation, and spectral calibration steps, making rapid batch detection and real-time dynamic monitoring difficult. Second, both methods generally suffer from high detection limits and insufficient sensitivity. They are only suitable for detecting high-concentration ascorbic acid samples and cannot accurately identify trace or minor concentration changes in human body fluids (such as sweat), failing to meet the high-precision requirements of human physiological monitoring. Furthermore, optical detection systems are easily interfered with by pigments, reducing impurities, and biomolecules in the sample, exhibiting poor anti-interference capabilities and specificity. Summary of the Invention

[0004] The purpose of this invention is to provide an Ag / UiO-66(Zr) composite electrode, its preparation method and application, and an electrochemical system for detecting ascorbic acid. The Ag / UiO-66(Zr) composite electrode provided by this invention has the advantages of low detection limit and strong anti-interference ability for detecting ascorbic acid.

[0005] To achieve the objectives of this invention, the following technical solutions are provided: An Ag / UiO-66(Zr) composite electrode includes an electrode substrate and Ag / UiO-66(Zr) coated on the surface of the electrode substrate; the Ag / UiO-66(Zr) includes a UiO-66(Zr) carrier and Ag nanoparticles loaded on the surface of the UiO-66(Zr).

[0006] Preferably, the electrode substrate is stainless steel.

[0007] This invention also provides a method for preparing the Ag / UiO-66(Zr) composite electrode described in the above technical solution, comprising the following steps: An Ag nanoparticle solution and a UiO-66(Zr) solution were coated on the surface of an electrode substrate, and the Ag / UiO-66(Zr) composite electrode was obtained after curing. The Ag nanoparticle solution includes Ag nanoparticles and film-forming aids; The UiO-66(Zr) solution comprises UiO-66(Zr), an alcohol-water solvent, and a film-forming aid.

[0008] Preferably, the Ag nanoparticles are prepared by reducing soluble silver salts with a reducing agent; the soluble silver salts include silver nitrate; and the reducing agent is red glue.

[0009] Preferably, the film-forming aid is a perfluorosulfonic acid polymer solution.

[0010] Preferably, the curing temperature is 40~80℃ and the time is 10~30min.

[0011] This invention also provides the application of the Ag / UiO-66(Zr) composite electrode described in the above technical solution or the Ag / UiO-66(Zr) composite electrode prepared by the preparation method described in the above technical solution in the electrochemical detection of ascorbic acid.

[0012] Preferably, the detection of ascorbic acid is the detection of ascorbic acid in sweat.

[0013] The present invention also provides an electrochemical system for detecting ascorbic acid, comprising a three-electrode reactor and an electrolyte, wherein the three-electrode reactor is provided with a counter electrode, a working electrode, a reference electrode and an electrochemical workstation; characterized in that the working electrode is the Ag / UiO-66(Zr) composite electrode described in the above technical solution.

[0014] Preferably, the detection limit of the electrochemical system for detecting ascorbic acid is 0.08 μM.

[0015] This invention provides an Ag / UiO-66(Zr) composite electrode, comprising an electrode substrate and Ag / UiO-66(Zr) coated on the surface of the electrode substrate; the Ag / UiO-66(Zr) comprises a UiO-66(Zr) support and Ag nanoparticles loaded on the surface of the UiO-66(Zr). In this invention, silver nanoparticles (AgNPs) possess high conductivity and electrocatalytic activity, while the UiO-66(Zr) metal-organic framework possesses high specific surface area and high porosity. By loading AgNPs onto the UiO-66(Zr) surface, this invention overcomes the shortcomings of AgNPs, such as easy aggregation, easy dissolution, and poor adhesion, thereby improving the conductivity and electrocatalytic activity of the composite electrode. This invention uses the Ag / UiO-66(Zr) composite electrode as a working electrode for the electrochemical detection of ascorbic acid in sweat, exhibiting advantages such as low detection limit and strong anti-interference ability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0017] Figure 1 SEM images of AgNPs / SS obtained in Comparative Example 1 and AgNPs / UiO-66(Zr) / SS obtained in Example 1 of this invention; Figure 2 The N2 adsorption / desorption isotherm of UiO-66(Zr) in Example 1 of this invention; Figure 3 Comparison of cyclic voltammetry curves of AgNPs / SS obtained in Comparative Example 1 and AgNPs / UiO-66(Zr) / SS obtained in Example 1 with and without 10 μM ascorbic acid; Figure 4 The effect of scanning amplitude on the oxidation current of ascorbic acid (10 μM) in SWV detection is shown in the figure. Figure 5 The results and performance of AgNPs / UiO-66(Zr) / SS ascorbic acid obtained in Example 1 of this invention are shown in Figure 1. (a) is the ascorbic acid concentration calibration curve; (b) is the effect of the concentration of interfering substances at 100mM on the oxidation current of ascorbic acid (10μM). Detailed Implementation

[0018] The present invention provides an Ag / UiO-66(Zr) composite electrode, comprising an electrode substrate and Ag / UiO-66(Zr) coated on the surface of the electrode substrate; the Ag / UiO-66(Zr) comprises a UiO-66(Zr) carrier and Ag nanoparticles loaded on the surface of the UiO-66(Zr).

[0019] In this invention, the electrode substrate is stainless steel, specifically 316 stainless steel.

[0020] This invention also provides a method for preparing the Ag / UiO-66(Zr) composite electrode described in the above technical solution, comprising the following steps: An Ag nanoparticle solution and a UiO-66(Zr) solution were coated on the surface of an electrode substrate, and the Ag / UiO-66(Zr) composite electrode was obtained after curing. The Ag nanoparticle solution includes Ag nanoparticles and film-forming aids; The UiO-66(Zr) solution comprises UiO-66(Zr), an alcohol-water solvent, and a film-forming aid.

[0021] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0022] Before use, the electrode substrate of this invention is ultrasonically cleaned with anhydrous ethanol and rinsed with distilled water.

[0023] In this invention, the Ag nanoparticles are prepared by reducing soluble silver salts with a reducing agent; the soluble silver salts include silver nitrate; the reducing agent is red glue; the red glue is used in the form of an aqueous solution; the concentration of the aqueous solution is 0.01~0.03 g / mL; the reduction temperature is 40~60℃, and the time is 5~10 min; the reduction is carried out under water bath conditions; the film-forming aid is a perfluorosulfonic acid polymer solution (Nafion).

[0024] In this invention, the UiO-66(Zr) is commercially available or prepared using the following method: The product is obtained by mixing zirconium oxychloride octahydrate (ZrOCl2·8H2O) and 1,4-phthalic acid (BDC) and then subjecting them to heat treatment and activation; the mass ratio of ZrOCl2·8H2O to BDC is 1:1~1.5; the heat treatment temperature is 120~150℃ and the time is 1~3h; the activation temperature is 150~170℃ and the time is 12~24h; the heat treatment is followed by alcohol washing; the alcohol washing temperature is 60~80℃.

[0025] In this invention, the alcohol-water solvent can specifically be a mixture of ethanol and water; the volume ratio of ethanol to water is 1:1~2.

[0026] In this invention, the volume ratio of the alcohol-water solvent to the film-forming aid is 10:1~2.

[0027] In this invention, the curing temperature is 40~80℃, and in a specific embodiment it can be 60 or 70℃; the time is 10~30min.

[0028] The present invention also provides an electrochemical system for detecting ascorbic acid, comprising a three-electrode reactor and an electrolyte, wherein the three-electrode reactor is provided with a counter electrode, a working electrode, a reference electrode and an electrochemical workstation; characterized in that the working electrode is the Ag / UiO-66(Zr) composite electrode described in the above technical solution.

[0029] In this invention, the detection limit of the electrochemical system for detecting ascorbic acid is 0.08 μM.

[0030] To further illustrate the present invention, the Ag / UiO-66(Zr) composite electrode, its preparation method and application, and the electrochemical system for detecting ascorbic acid provided by the present invention are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0031] Example 1 Weigh 0.5g of red glue, grind it, and dissolve it in 50 mL of deionized water to prepare a red glue solution. Measure 15 mL of the red glue solution and mix it with 20 mL of 5 mM AgNO3 solution. Heat the mixture in a 45℃ water bath for 5 min to obtain solution A.

[0032] Weigh 1.5 mmol ZrOCl2·8H2O and 1.5 mmol 1,4-phthalic acid, grind them thoroughly, transfer them to a stainless steel autoclave lined with polytetrafluoroethylene, and heat at 130 °C. After cooling to room temperature, collect the resulting white powder and wash it with ethanol at 70 °C for 3 h. Dry the resulting solid under vacuum at 150 °C and activate it for 24 h to obtain solid UiO-66.

[0033] Weigh 50 mg of the above UiO-66 powder and disperse it in a mixture of 10 mL of water-ethanol solution (water / ethanol = 1:1, v / v) and 1 mL of Nafion. Sonicate for 15 min to obtain solution C.

[0034] A 1cm×1cm, 0.2mm thick 316 stainless steel electrode was ultrasonically cleaned with anhydrous ethanol and rinsed with distilled water. 100μL of solution C was added dropwise to the surface of the stainless steel electrode. Then, a mixture of 100μL of solution A and Nafion solution (solution A / Nafion solution = 9:1, v / v) was added dropwise to the electrode surface. The electrode was heated at 50℃ for 10min to obtain a silver-zirconium-based metal-organic framework composite electrode, denoted as AgNPs / UiO-66(Zr) / SS.

[0035] Comparative Example 1 Weigh 0.5g of red glue, grind it, and dissolve it in 50 mL of deionized water to prepare a red glue solution. Measure 15 mL of the red glue solution and mix it with 20 mL of 5 mM AgNO3 solution. Heat the mixture in a 45℃ water bath for 5 min to obtain solution A.

[0036] A 1cm×1cm, 0.2mm thick 316 stainless steel electrode was ultrasonically cleaned with anhydrous ethanol and rinsed with distilled water. 100μL of solution A was added dropwise to the surface of the stainless steel electrode. Then, a mixture of 100μL of solution A and Nafion solution (solution A / Nafion solution = 9:1, v / v) was added dropwise to the surface of the electrode and heated at 50℃ for 10min to obtain a silver-based electrode, denoted as AgNPs / SS.

[0037] Figure 1 SEM images of AgNPs / SS obtained in Comparative Example 1 and AgNPs / UiO-66(Zr) / SS obtained in Example 1 of this invention; Figure 2 This is the N2 adsorption / desorption isotherm of UiO-66(Zr) in Example 1 of this invention. (From...) Figures 1-2 The results show that both spherical AgNPs and AgNPs / UiO-66(Zr) are fixed on the stainless steel surface; and Figure 2 The typical type I isotherm of UiO-66(Zr) is shown, demonstrating its high surface area and significant microporosity.

[0038] Application examples A standard three-electrode system was constructed using a CHI 760e electrochemical workstation. The electrodes prepared in Example 1 and Comparative Example 1 were used as working electrodes, the Ag / AgCl electrode as the reference electrode, and the Pt wire as the counter electrode.

[0039] Sodium chloride, glucose, lactic acid, urea, and cortisol were added to a 10 μM ascorbic acid solution, each at a concentration of 100 mM. The AgNPs / UiO-66(Zr) / SS obtained in Example 1 was subjected to square wave voltammetry (SWV) electrochemical detection at a scan rate of 0.04 V / s, a step potential of 0.004 V, a frequency of 10 Hz, and an amplitude of 0.05 V.

[0040] The AgNPs / UiO-66(Zr) / SS obtained in Example 1 and the AgNPs / SS obtained in Comparative Example 1 were subjected to cyclic voltammetry (CV) electrochemical detection in solutions with and without 10 μM ascorbic acid, respectively, at a scan rate of 0.04 V / s and a scan range of 0-0.7 V.

[0041] A calibration curve was plotted between the SWV oxidation current and the concentration of ascorbic acid in the range of 10 μM to 400 μM; the detection limit was calculated according to the formula LOD = 3σ / S (where σ is the standard deviation of the background current and S is the slope of the calibration curve).

[0042] Artificial sweat was prepared by adding 10 μM, 100 μM, and 150 μM ascorbic acid solutions, respectively. Electrode B was subjected to SWV testing in artificial sweat with different ascorbic acid concentrations to determine its concentration and calculate the recovery rate (measured concentration / added concentration × 100%).

[0043] CV data showed that the ascorbic acid oxidation potentials of AgNPs / UiO-66(Zr) / SS and AgNPs / SS shifted positively to 0.43V and 0.48V, respectively. The UiO-66(Zr) layer inhibited the dissolution of AgNPs and improved the ascorbic acid oxidation current.

[0044] Depend on Figure 3 and Figure 4 The results showed that the ascorbic acid oxidation current increased from 1.0 to 8.0 μA. The increase in the ascorbic acid oxidation current at AgNPs / UiO-66(Zr) / SS was attributed to the increased surface area of ​​AgNPs and UiO-66(Zr), the stability of UiO-66(Zr), and the high electrocatalytic activity brought about by the high conductivity of AgNPs.

[0045] Depend on Figure 5 The results show that, according to the formula, the detection limit of this composite electrode for ascorbic acid is as low as 0.08 μM. Figure 5 The results show that even with concentration differences of tens of thousands of times, the change in the oxidation signal of the target ascorbic acid did not exceed 5%. This signal deviation demonstrates that the sensor has excellent anti-interference ability and high selectivity for other metabolites. As shown in Table 1, the recovery values ​​at the three concentration gradients are all within a highly acceptable range.

[0046] Table 1 Recovery rate of ascorbic acid in artificial sweat

[0047] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An Ag / UiO-66(Zr) composite electrode, characterized in that, It includes an electrode substrate and Ag / UiO-66(Zr) coating the surface of the electrode substrate; The Ag / UiO-66(Zr) comprises a UiO-66(Zr) carrier and Ag nanoparticles loaded on the surface of the UiO-66(Zr).

2. The Ag / UiO-66(Zr) composite electrode according to claim 1, characterized in that, The electrode substrate is made of stainless steel.

3. The method for preparing the Ag / UiO-66(Zr) composite electrode according to claim 1 or 2, characterized in that, Includes the following steps: An Ag nanoparticle solution and a UiO-66(Zr) solution were coated on the surface of an electrode substrate, and the Ag / UiO-66(Zr) composite electrode was obtained after curing. The Ag nanoparticle solution includes Ag nanoparticles and film-forming aids; The UiO-66(Zr) solution comprises UiO-66(Zr), an alcohol-water solvent, and a film-forming aid.

4. The preparation method according to claim 3, characterized in that, The Ag nanoparticles were prepared by reducing soluble silver salts with a reducing agent. The soluble silver salt includes silver nitrate; the reducing agent is red glue.

5. The preparation method according to claim 3, characterized in that, The film-forming aid is a perfluorosulfonic acid polymer solution.

6. The preparation method according to claim 3, characterized in that, The curing temperature is 40~80℃ and the time is 10~30min.

7. The application of the Ag / UiO-66(Zr) composite electrode according to claim 1 or 2 or the Ag / UiO-66(Zr) composite electrode prepared by the preparation method according to any one of claims 3 to 6 in the electrochemical detection of ascorbic acid.

8. The application according to claim 7, characterized in that, The detection of ascorbic acid refers to the detection of ascorbic acid in sweat.

9. An electrochemical system for detecting ascorbic acid, comprising a three-electrode reactor and an electrolyte, wherein the three-electrode reactor is provided with a counter electrode, a working electrode, a reference electrode, and an electrochemical workstation; characterized in that, The working electrode is the Ag / UiO-66(Zr) composite electrode as described in claim 1 or 2.

10. The electrochemical system for detecting ascorbic acid according to claim 9, characterized in that, The detection limit of the electrochemical system used to detect ascorbic acid is 0.08 μM.

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