CN103076375A - Preparation method and application of coaxial solid/nanoporous gold/Co3O4 composite electrode material - Google Patents

Abstract

The invention relates to a preparation method and application of a coaxial solid/nanoporous gold/Co ₃ O ₄ composite electrode material, which uses electrochemical alloying/dealloying in-situ etching technology to prepare a self-supporting coaxial solid/nanoporous gold Electrode material, and Co ₃ O ₄ nanoparticles modified by hydrothermal synthesis on the outer porous gold of the material as a preparation method and application of a metal/oxide composite electrode for a new type of biosensor. The present invention is based on a three-electrode electrochemical system, and prepares a self-supporting coaxial entity/nanoporous gold electrode material by electrochemical alloying/dealloying on a gold wire. A self-supported coaxial entity/nanoporous gold/Co ₃ O ₄ composite nanostructure was fabricated from ammonium chloride solution through a hydrothermal synthesis process, and the material was used for the electrochemical detection of glucose. The results show that the material is highly sensitive to glucose due to the interaction of Au and Co ₃ O ₄ and the common effect of the unique microstructure.

Description

Preparation method and application of coaxial solid/nanoporous gold/Co3O4 composite electrode material

Technical field:

The invention relates to the technical field of nanometer metal/oxide structure preparation and chemical analysis and detection. the

Background technique:

Biosensors for glucose detection need to have the characteristics of high sensitivity, good reliability, rapid response, good selectivity and low cost. At present, the methods mainly used for detection are: optical method, colorimetric method, electrochemical method and electrochemiluminescence method. Among them, the electrochemical method is simple, high sensitivity, and low cost, and has attracted widespread attention. the

Typically, enzyme-based electrochemical sensors for glucose utilize the biocatalysts glucose dehydrogenase (GDH) and glucose oxidase (GOx). The GDH-based glucose biosensor produces nicotinamide adenine dinucleotide (NADH) through the electrochemical oxidation reaction catalyzed by the GDH enzyme, but due to the slow electron transfer kinetics in NADH, its electrochemical oxidation requires a higher potential of 0.7 ~1.0V (vs. SCE). The GOx-based glucose biosensor generates H ₂ O ₂ by catalyzing the oxidation of glucose, which also requires a high potential exceeding 0.6 V (vs. SCE). At such a high potential, a variety of electrochemically active species coexist in biological fluids, such as ascorbic acid, microbial C, uric acid, etc., will also be oxidized, thereby generating interference signals. Moreover, enzyme-based sensors have the following disadvantages: (1) lack of long-term stability, which is an inherent characteristic of enzymes; (2) enzymes, including GOx, are very expensive and costly; (3) enzymes Its activity is extremely susceptible to temperature, solution pH, humidity and other impurities such as precious metals. Moreover, glucose oxidase is easily soluble in water, unstable in nature, and the active center of the enzyme is deeply buried inside the protein. These factors affect the sensitivity, stability and reproducibility of the glucose biosensor, and also limit its industrial development.

In view of the problems faced by the above-mentioned biological enzyme catalysts, non-enzyme catalysts have a huge development space in the application of glucose detection. Recently, nanostructured metal oxides have attracted extensive attention due to their low price, high biocompatibility and electrocatalytic activity, as well as enhanced electron transfer and adsorption capabilities. New electrode materials were introduced for sensor applications, providing new opportunities for improving non-enzymatic glucose biosensors. However, the ultra-low conductivity of metal oxide nanostructures, for example, the conductivity of Co ₃ O ₄ at room temperature is only 10 ^-5 S m ^-1 , severely limits their application in highly sensitive and reliable, fast-response electrochemical biological Wide range of applications in sensors. One of the approaches to enhance the electron transport capability in electrochemical biosensing is to design composite materials with high catalytic activity and high conductivity. Although the current research is mainly based on zero-dimensional, one-dimensional or two-dimensional nanostructured carbon materials or metal nanoparticles, preliminary progress has been made. However, the electron transmission distance in these low-dimensional nanostructures is limited, and the integration between each structure and the current collector will generate high contact resistance. Therefore, the modification of the electrical conductivity of monolithic electrodes assembled from these low-dimensional nanostructures is still limited, limiting their wide application in electrochemical sensors with high sensitivity, low detection concentration limit, and fast response.

Invention content:

The purpose of the present invention is to provide a preparation method and application of a self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ composite electrode material with high mechanical stability, especially in the detection of trace glucose. The invention combines metal oxides in the metal channels of the three-dimensional nanoporous structure by combining in-situ electrochemical alloying/dealloying with hydrothermal synthesis, and integrates the nanoporous structure into the current collector to achieve improved Electrocatalytic activity while minimizing the contact resistance between the active material and the current collector. The composite nanostructure has unique double-connected nanopores and metal ligaments, which can simultaneously enhance the transport of analytes and electrons, and the ultra-high specific surface area provided by the nanoporous structure can effectively and fully utilize metal/oxide composites Enhanced electrocatalytic activity.

The present invention realizes through the technical scheme of yoxi amount:

A method for preparing a coaxial solid/nanoporous gold/Co ₃ O ₄ composite electrode material, comprising the following steps:

a. In a water bath at 60°C, fully dissolve anhydrous ZnCl2 with a purity of 99.9% in benzyl alcohol (BA99%) through magnetic stirring to obtain a _ZnCl2 /BA electrolyte with a concentration of 1-2M;

b. A gold wire with a diameter of 0.01 to 0.2 mm is used as the working electrode, a Zn plate is used as the counter electrode, and a Zn wire is used as the reference electrode to assemble a three-electrode electrochemical system. The above mixed organic solution is used as the electrolytic liquid, heated in an oil bath and Maintain at 100～120℃;

c. In the range of -0.8 to 1.9V, the electrochemical scanning rate is 5 to 50mV/s scanning cycle, and after 20 to 50 alloying/dealloying cycles, a self-supporting coaxial entity/nanoporous structure is obtained gold electrode material. the

In the preparation method of a coaxial entity/nanoporous gold/Co ₃ O ₄ composite electrode material, after the gold wire in the step b is polished, it is washed with acetone, ethanol and high-purity water in sequence, and finally dried, as working electrode.

The preparation method of a coaxial solid/nanoporous gold/Co ₃ O ₄ composite electrode material prepares a self-supporting coaxial solid/nanoporous structure, and produces a self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ Composite electrode materials, comprising the following steps:

a. Put Co(NO ₃ ) ₂ and CTAB (cetyltrimethylammonium bromide) with a concentration ratio of 3:1 in ethanol and water with a ratio of 6:1 and stir well;

B, the sample of claim 1, that is, the gold electrode material of coaxial solid/nanoporous structure is clamped and erected in the center of the configuration solution with support clips, so that it can fully contact the solution around it;

c. Put the prepared sample and solution in the reaction kettle, set the temperature at 180° C., and obtain a self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ composite electrode material after 60 to 120 minutes.

Described a kind of self-supporting coaxial entity/nanoporous gold/Co _{3 O} The composite electrode material is directly used in the electrochemical test to glucose concentration, comprises the following steps:

a, using the sample as a working electrode, Pt as a counter electrode, and Ag/AgCl as a reference electrode to form a three-electrode system;

b. When using the sample as the working electrode for electrochemical measurement, the range of the cyclic voltammetry characteristic curve is determined as -0.8～0.6V for cyclic voltammetry scanning; the voltage of the current-time curve is set as 0.26V, when After the background current reaches a steady state (1-2min), record the time-current curve segment (1-2min), and use a micro-sampler to add glucose solution samples while stirring (1-2min), and measure at different glucose solution concentrations to obtain The current response value of the sensor to glucose is within the range of 5nM to 70mM, and the linear relationship between current and glucose concentration is obtained;

c. The linear relationship between the current of the sample used as the working electrode and the glucose concentration changes with different concentrations. the

The structure of the present invention is used as an electrode as a new type of electrochemical glucose sensor, which is directly used for fast ultra-low concentration electrochemical determination of glucose, self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material As an electrode, it has the advantages of high catalytic performance, good stability, strong anti-interference, etc., and has high detection efficiency and high accuracy for glucose.

Description of drawings:

Figure 1. Schematic diagram of the fabrication process of a self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material, in which:

(a) physical gold wire;

(b) coaxial solid/nanoporous gold wire;

(c) Coaxial solid/nanoporous/cobalt oxide composite structure. the

Figure 2. Scanning electron microscope (SEM) characterization of self-supporting coaxial solid/nanoporous gold wires, where:

(a) Low-magnification SEM characterization of coaxial solid/nanoporous gold wire;

(b) SEM characterization diagram of the cross-section of the coaxial solid/nanoporous gold wire;

(c) Top-view SEM characterization of coaxial solid/nanoporous gold wires. the

Fig. 3. Scanning electron microscopy (SEM) characterization of self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode materials.

Fig. 4. Transmission electron microscopy (TEM) characterization of self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode materials.

Fig. 5. Raman spectra of the self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material.

Fig. 6. XRD spectrum of self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material.

Figure 7. Comparison of self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode materials and 20 μm thick porous gold toughness experiments, in which:

(a) pure nanoporous gold;

(b) Coaxial solid/nanoporous gold. the

Figure 8. Cyclic voltammetry characteristic curves of the self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material in 0.5M KOH solution (a) containing (b) excluding 10mM glucose, in:

(a) contains (b) does not contain the cyclic voltammetry characteristic curve in 10mM glucose;

(b) Cyclic voltammetry curve without 10 mM glucose. the

Figure 9. The self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material as the fast response curve of the electrode for glucose detection, where:

(a) Fast response curve,

(b) Standard curve. the

Figure 10. The _detection limit and anti-interference performance of the self-supporting coaxial solid/nanoporous gold/ _Co3O4 nanoparticle composite electrode material as an electrode, where:

(a) the detection limit of the electrode,

(b) Anti-interference of electrodes. the

Detailed ways:

The specific content and implementation mode of the present invention will be further described below in conjunction with the examples. the

Example

The preparation process and steps in this embodiment are as follows:

(1) In a water bath at 60°C, fully dissolve ZnCl ₂ with a purity of 99.9% in benzyl alcohol (BA99%) through magnetic stirring to obtain a ZnCl ₂ /BA electrolyte with a concentration of 1.5M and a diameter of 0.2mm , a gold wire with a length of 1.5 cm was polished, then washed with acetone, ethanol and high-purity water in sequence, and finally dried, and used as a working electrode. A zinc wire with a width of 1 mm and a length of 4 cm is used as a reference electrode, and a zinc plate with a width of 5 mm and a length of 4 cm is used as a counter electrode. The three electrodes are placed in the above-mentioned preparation solution without setting a salt bridge connection, and the electrochemical alloying/dealloying process is carried out by using a three-electrode system to scan and cycle on the gold electrode at 120°C. The scanning voltage range is -0.72 ~ 1.88V (vs. Zn), and the scanning rate of multiple cycles is selected as 10mV/S. After 50 cycles, the gold electrode is sequentially placed in benzyl alcohol, ethanol and deionized water. cleaning.

(2) Put 6mM Co(NO ₃ ) ₂ and 2mM CTAB (cetyltrimethylammonium bromide) in 30mL ethanol and 5mL water and stir well; clamp the porous gold-wrapped gold wire with a support clamp Stand upright in the center of the configuration solution, so that the surroundings of the self-supporting porous gold-wrapped gold wire structure can fully contact the solution, put the prepared sample and solution in the reaction kettle, set the temperature at 180°C, and react for 90 minutes to obtain a self-supporting coaxial entity /Nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material.

(3) During electrochemical measurement, set the range of the cyclic voltammetry characteristic curve to -0.8～0.6V for cyclic voltammetry scanning, set the voltage of the current-time curve to 0.26V, when the background current reaches a steady state (2min), record the time current curve segment (2min), and add the glucose solution sample with a micro-injector and stir simultaneously (2min), the current response value of the sensor measured under different glucose solution concentrations to glucose, in 5nM～ In the range of 70mM, the linear relationship between the current and the glucose concentration is obtained; the linear relationship between the current and the glucose concentration changes with the different linear slopes of the concentration; the interfering substances UA (uric acid), AP (acetaminophen), and AA (ascorbic acid) are added Go to the three-electrode test system for interference detection, which is the same as the glucose detection step, and finally drop glucose for anti-interference comparison. the

A self-supporting coaxial entity/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material as a glucose sensor uses and method as an electrode, and its use is directly used for the electrochemical determination of glucose concentration; the use method is as follows: During the electrochemical measurement, the range of the cyclic voltammetry characteristic curve was set as -0.8～0.6V for cyclic voltammetry scanning, and the voltage of the current-time curve was set as 0.26V. When the background current reached a steady state (1～ 2min), record the time-current curve segment (1-2min), and add the glucose solution sample with a micro-sampler while stirring (1-2min), and measure the current response value of the sensor to glucose under different glucose solution concentrations, In the range of 5nM to 70mM, the linear relationship between the current and the glucose concentration is obtained; the linear relationship between the current and the glucose concentration changes with the different concentration of the linear slope

Characterization of a self-supporting coaxial solid/nanoporous gold/ _Co3O4 nanoparticle composite electrode material as a glucose sensor _:

The surface morphology of the self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material was observed by scanning electron microscopy (SEM), see Fig. 2 and Fig. 3 . It can be seen from the figure that the three-dimensional bicontinuous porous structure on the surface of the coaxial solid/nanoporous gold wire is uniform, which effectively improves the specific surface area of the material, and the self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nano The surface of the particle composite electrode material is evenly covered and wrapped by Co ₃ O ₄ nanoparticles. In the case of high conductivity, the specific surface area of the composite structure is further increased, and at the same time, the characteristics of Co ₃ O ₄ particles can be effectively utilized, resulting in The sensor produces a highly sensitive current response. Referring to Figures 5 and 6, a core-shell structure in which self-supporting porous gold-wrapped gold wires and self-supporting porous gold-wrapped gold wires are rewrapped by Co ₃ O ₄ particles has been characterized by XRD and DES, proving that the preparation process of the structure is accurate. The product is indeed Co ₃ O ₄ particles.

Toughness measurement:

The electrode material of the present invention and the porous gold with a thickness of 20um were respectively tested for toughness, and the maximum bending degree was tracked in real time, and it was found that the self-supporting coaxial entity/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material of the present invention It can be bent into any shape without breaking.

Electrochemical determination:

Under the optimal test conditions, the cyclic voltammetry and chronoamperometric responses of the self-supporting coaxial solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material to glucose are shown in Fig. 8 . This electrode material has a higher current density than the self-supporting coaxial solid/nanoporous gold wire, and see Figure 10 for its very short current response time when detecting glucose, which is mainly due to the self-supporting coaxial The solid/nanoporous gold/Co ₃ O ₄ nanoparticle composite electrode material has good biocompatibility, porosity and ultrahigh conductivity. Figure 9 shows that as the glucose concentration increases, the sensor's response to glucose gradually increases, and the current has a linear relationship with the glucose concentration.

The electrode prepared by the present invention, referring to Fig. 10, has a very short current response time when detecting glucose, less than 1 s. The sensitivity to glucose detection is high, the minimum glucose concentration for detection is 5nM, and the resistance to interfering substances UA (uric acid), AP (acetaminophen) and AA (ascorbic acid) is high. the

Claims (4)

1. coaxial entity/nano-porous gold/Co ₃O ₄The preparation method of combination electrode material may further comprise the steps:

A, in 60 ℃ of water-baths, with the anhydrous ZnCl of purity 99.9% ₂Stirring fully is dissolved in the phenmethylol (BA99%) and obtains ZnCl through magneton ₂/ BA electrolytic solution, concentration of electrolyte are 1～2M;

B, with diameter be the gold thread of 0.01～0.2mm as working electrode, the Zn plate is as to electrode, the Zn line is assembled into the three-electrode electro Chemical system as contrast electrode, above mixed organic solvents is that electrolyte heats in oil bath and maintains 100～120 ℃;

C, in the scope of-0.8～1.9V take Electrochemical Scanning speed as 5～50mV/s scan cycle, through behind 20～50 alloys/go the alloy cyclic process, obtain the gold electrode material of the coaxial entity/nano-porous structure of self-supporting.

2. according to a kind of coaxial entity/nano-porous gold claimed in claim 1/Co ₃O ₄The preparation method of combination electrode material, the gold thread among the described step b utilizes acetone, ethanol and high purity water to clean after polishing successively, and at last oven dry is as working electrode.

3. according to a kind of coaxial entity/nano-porous gold claimed in claim 1/Co ₃O ₄The preparation method of combination electrode material prepares the coaxial entity/nano-porous structure of self-supporting, produces the coaxial entity/nano-porous gold of self-supporting/Co ₃O ₄Combination electrode material may further comprise the steps:

A, be the Co (NO of 3:1 with concentration ratio ₃) ₂And CTAB (cetyl trimethyl ammonium bromide) ratio of being placed on is to stir in the second alcohol and water of 6:1;

B, be that the gold electrode material of coaxial entity/nano-porous structure picks up with propclip and stands upright on configuration solution central authorities with the sample of claim 1, can both fully contact solution around making it;

C, ready sample and solution are placed in the reactor, temperature setting is set to 180 ℃, obtains the coaxial entity/nano-porous gold of self-supporting/Co behind 60～120min ₃O ₄Combination electrode material.

4. according to the coaxial entity/nano-porous gold of a kind of self-supporting claimed in claim 3/Co ₃O ₄Combination electrode material is directly used in the electro-chemical test to concentration of glucose, may further comprise the steps:

A, with described sample as working electrode, Pt is as to electrode, Ag/AgCl forms three-electrode system as contrast electrode;

B,, the characteristic scope of cyclic voltammetric is decided to be during as the working electrode electrochemical gaging with described sample-0.8～0.6V carries out cyclic voltammetry scanning; The voltage of electric current-time curve is set as 0.26V, after background current reaches stable state (1～2min), writing time, the current curve section (1～2min), and add the glucose solution sample with microsyringe and stir simultaneously (1～2min), the sensor that will measure under different glucose solution concentration is to the current-responsive value of glucose, in 5nM～70mM scope, obtain the linear relationship of electric current and concentration of glucose;

C, described sample change as the linear relationship of the electric current of working electrode and the concentration of glucose slope with the not collinearity of concentration.

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