CN109668951B - Based on MoS2Electrochemical sensing method for enzyme-free detection of glucose by using AuNPs-PPY composite material - Google Patents
Based on MoS2Electrochemical sensing method for enzyme-free detection of glucose by using AuNPs-PPY composite material Download PDFInfo
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Abstract
Based on MoS2The electrochemical sensing method for detecting the glucose by the AuNPs-PPY composite material without enzyme is characterized in that the AuNPs are modified on the surface of the GCE by an electrodeposition method, so that the conductivity of the electrode is improved; then the MoS is dripped2Nanosheet dispersion to prepare MoS2-AuNPs/GCE electrodes; then the pyrrole is modified in MoS by electric polymerization method2AuNPs/GCE surface, increasing electron transport rate of system, providing support for Cu (II) recombination, and finally placing electrode in CuCl2Culturing in solution for 1h to obtain MoS2-AuNPs-PPY-Cu (II)/GCE electrode. MoS of the invention2The AuNPs-PPY based electrochemical sensing method can realize the linear detection range of 0.1 nM-80 nM for glucose, the detection limit can reach 0.085nM, and has higher sensitivity.
Description
Technical Field
The invention belongs to the technical field of material science and electrochemistry, and relates to a method based on MoS2An electrochemical sensing method for detecting glucose by using AuNPs-PPY composite material without enzyme.
Background
Glucose is widely distributed in nature, is the main energy substance of organisms, and has irreplaceable effect on metabolism. The method has great significance for the accurate analysis and the rapid detection of the glucose in the fields of food industry, biochemistry, environmental monitoring, medicine and the like. Therefore, the development of a rapid and accurate glucose concentration detection technique has attracted extensive attention of researchers.
At present, methods for detecting glucose mainly include high performance liquid chromatography, spectrometry, colorimetry, spectrophotometry and the like. Although the method can realize the quantitative detection of the glucose, the method has the problems of high instrument price, high operation cost, complicated detection process and the like. In addition, the problems of low detection sensitivity, poor accuracy and the like of part of methods limit the application of the methods to a certain extent. Therefore, electrochemical sensing is a new detection method, and has attracted attention because of its advantages of simple and convenient operation, rapid detection, easy miniaturization, high sensitivity, etc.
Glucose electrochemical sensors are largely classified into two types, enzyme glucose sensors and enzyme-free glucose sensors, according to whether glucose oxidase (GOx) is contained or not. The enzyme electrochemical glucose sensor is characterized in that glucose oxidase (GOx) is fixed on the surface of an electrode, glucose and the GOx generate a specific catalytic reaction, and a reaction signal is collected in the form of an electric signal, so that the concentration of a corresponding substrate is detected. However, the enzyme is unstable, easily affected by factors such as environment, temperature and pH, and has poor reproducibility and complex process due to high price, complex manufacturing process and the like, and the application of the enzyme is limited to a certain extent, so that the enzyme-free electrochemical sensing technology is developed.
The main reason influencing the sensitivity of the enzyme-free electrochemical sensor is the excellent degree of the electrocatalytic activity of the nano material on the surface of the electrode, so the selection of the material is particularly important. In recent years, molybdenum disulfide nano materials are applied to the preparation of glucose sensors due to unique properties, such as large specific surface area, good biocompatibility, sensitive surface state and high catalytic activity. The sensor shows excellent electrocatalytic performance, but the molybdenum disulfide has general conductivity and a lamellar structure is easy to gather, so that the sensitivity of the sensor needs to be improved. While the use of metal nanoparticles in glucose sensors, while providing some improvement in sensitivity of detection, is susceptible to other ions, particularly Cl-The noble metal is poisoned and loses catalytic activity, and the noble metal is expensive and has poor selectivity.
In conclusion, there is a need for improvements in electrochemical enzyme-free glucose sensors that result in new enzyme-free glucose electrochemical sensors with higher sensitivity and better selectivity.
Disclosure of Invention
The invention aims to realize the detection of glucose by constructing an electrochemical sensing system by jointly modifying molybdenum disulfide nanosheets with gold nanoparticles AuNPs and polypyrrole PPY. The invention utilizes MoS2As an electrode material, the AuNPs are further electrodeposited to play a role in improving the conductivity, the polypyrrole is used for further improving the electron conduction rate of the electrode, and a support is provided for the compounding of Cu (II), and finally the electrode material is based on MoS2The electrochemical biosensing system constructed by the AuNPs-PPY composite material can realize sensitive, rapid and specific detection on glucose.
The technical scheme of the invention is as follows:
based on MoS2The electrochemical sensing method for detecting glucose by the AuNPs-PPY composite material without enzyme comprises the following steps:
(1) immersing a glassy carbon electrode GCE with a polished surface into a solution with a molar ratio of 1: 10:10 HAuCl4、H2SO4And Na2SO4Mixing the solution with HAuCl4、H2SO4And Na2SO4The total molar concentration of the glass carbon electrode is controlled to be 0.1-2mM, scanning is carried out at 50mV/s within the range of-0.2V-1V through cyclic voltammetry, at the moment, reduction reaction of Au occurs on the surface of the glass carbon electrode, AuNPs are modified to the surface of the glass carbon electrode through an electrodeposition method, and the modified electrode is called AuNPs/GCE;
(2) preparation of MoS by ultrasonic exfoliation2Nanosheet: mixing MoS2Mixing the powder and a DMF solution according to a molar ratio of 1:1, and carrying out ultrasonic treatment for 10h-20h to obtain a uniform suspension; then centrifuging the prepared suspension at low speed of 1000rpm-3000rpm, then centrifuging at high speed of 10000rpm-13000rpm, and finally obtaining MoS by vacuum freeze drying2Nanosheets;
(3) MoS obtained in the step (2)2Dispersing the nanosheets in high-purity water to obtain a uniform suspension liquid with the concentration of 0.1-2 mg/mL; dropping the suspension on the surface of AuNPs/GCE with a dropping amount of 142 mug/cm2And standing at room temperature until a uniform film is formed, thus obtaining the MoS2-AuNPs/GCE；
(4) MoS obtained in the step (3)2-AuNPs/GCE infusion molar ratio 1: pyrrole of 1 and H2SO4In the mixture, pyrrole and H2SO4The total molar concentration of the mixed solution is controlled to be 0.1M, the mixed solution is scanned within the range of 0.3-0.6V by a current-time method, the scanning time is 200s-1000s, and MoS is obtained2-AuNPs-PPY/GCE；
(5) The MoS obtained in the step (4) is treated2-AuNPs-PPY/GCE electrode immersion in 0.01-0.2M CuCl2Culturing in solution for 1-2h to obtain MoS2-AuNPs-PPY-Cu(II)/GCE；
(6) Preparing a NaOH buffer solution with the molar concentration of 0.001-0.1M, and mixing the MoS obtained in the step (5)2-AuNPs-PPY-Cu (II)/GCE is placed in a mixed solution of glucose and NaOH, and the result is tested and analyzed by using differential pulse voltammetry; the test parameters are: the potential range is 0.1V-0.8V, the potential increment is 4mV, the amplitude is 25mV, and the frequency is 25 Hz.
The invention has the beneficial effects that:
(1) the sensitivity is high, and the detection limit can reach 0.085nM (S/N is 3);
(2) the selectivity is high, and the noise value is low;
(3) the cost is low, and the gold electrode which is expensive in manufacturing cost and easy to consume is effectively replaced.
Drawings
FIG. 1 shows MoS2Scanning electron micrographs of products at different stages in the synthesis process of the AuNPs-PPY composite material, wherein A is the electron micrograph of a molybdenum disulfide nanosheet, and B is MoS2Electron micrograph of AuNPs Material, C MoS2-electron microscopy of AuNPs-PPY;
FIG. 2 shows MoS2-AC impedance diagram in AuNPs-PPY/GCE electrode modification process, wherein a is GCE and b is MoS2(GCE, c is MoS)2PPY/GCE, d is MoS2-AuNPs-PPY/GCE；
FIG. 3 shows a MoS for glucose assay according to the present invention2-a schematic detection process for AuNPs-PPY based electrochemical sensing method;
FIG. 4(A) is a differential pulse voltammogram of glucose obtained by the method of the present invention;
FIG. 4(B) is a graph showing the linear relationship between the peak current value of glucose and the glucose concentration obtained by the method of the present invention.
Detailed Description
The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.
The invention relates to a MoS for detecting glucose2-AuNPs-PPY based electrochemical sensing method. The method synthesizes MoS2The nano-sheets and the electrodeposited AuNPs are used as electrode materials, so that the conductivity of the glassy carbon electrode is effectively improved; the PPY is used for further modifying the electrode, and plays a role of compounding Cu (II); based on MoS2An electrochemical sensing system constructed by the AuNPs-PPY composite material converts glucose into gluconolactone in NaOH alkaline medium by using a Cu (II)/Cu (III) redox couple as a catalytic center at an oxidation potential of + 0.45V.
The technical solution of the present invention is described in detail below, but the scope of the present invention is not limited to the embodiments.
Example 1: MoS for glucose detection2-AuNPs-PPY based electrochemical sensing method.
(1) Respectively mixing 30mg of MoS2The powder was mixed with 30mL of N, N-Dimethylformamide (DMF) solution as an exfoliation and dispersing solvent and sonicated for 12 hours to obtain a homogeneous suspension. The prepared suspension was then centrifuged at 1000rpm for 5 minutes, 13000rpm for 10 minutes and finally MoS was obtained by vacuum freeze-drying2Nanosheet powder; the morphology structure is shown in FIG. 1A, and the two-dimensional lamellar structure is good and has a large contactable surface area.
(2) Grinding a GCE electrode in alpha-alumina polishing powder suspension with the particle sizes of 1 mu m, 0.3 mu m and 50nm for 2 minutes in sequence, then placing the GCE electrode in absolute ethyl alcohol and high-purity water respectively for 5 minutes by ultrasonic treatment to remove alumina powder and organic matters adsorbed on the surface of the electrode, washing the electrode by high-purity water, and introducing N2Drying; the GCE electrode was immersed in 1mM HAuCl4Solution (containing 0.01 MH)2SO4And 0.01MNa2SO4) In the electrodeposition of AuNPs by cyclic voltammetry, potentialThe range is-0.2V-1V, the scanning speed is 50mV/s, the number of scanning turns is 5 turns, the electrode is washed by high-purity water and then N is introduced2Blow-drying, and marking the modified electrode as AuNPs/GCE.
(3) 1mg of MoS2And ultrasonically dispersing the nano-sheet powder into 1mL of high-purity water to obtain a uniform suspension with the concentration of 1 mg/mL. Spreading 10 μ L of the solution on the surface of AuNPs/GCE electrode, drying at room temperature until a uniform film is formed on the surface, wherein the electrode is marked as MoS2-AuNPs/GCE; the morphology is shown in fig. 1B, and granular AuNPs can be seen between lamellar structures, with a particle size of about 100 nm.
(4) Mixing MoS2Immersion of the AuNPs/GCE electrode in a 0.1M pyrrole solution (containing 0.1M H)2SO4) In the method, pyrrole is electropolymerized by a current-time method, the potential is 0.5V, the scanning time is 600s, the electrode is washed by high-purity water and then N is introduced2Blow-drying, the modified electrode is marked as MoS2-AuNPs-PPY/GCE; the morphology structure is shown in figure 1C, and spherical polypyrrole is modified on MoS2Surface and interlayer.
(5) Immersing the electrode in 0.1M CuCl2Incubate in solution for 1h, then rinse with high purity water and let in N2Blow drying, in which the Cu (II) has self-assembled to the surface of the electrode by complexation with polypyrrole, the electrode being labelled MoS2-AuNPs-PPY-Cu(II)/GCE。
Meanwhile, the electrode modification process between the step (2) and the step (4) is characterized by using an alternating current impedance method, and the result is shown in fig. 2. The semi-circle of the high frequency region in the AC impedance spectrum represents the electron transport confinement process, with larger semi-circle diameter indicating electron transport resistance (R) at the electrode/solution interfacect) The larger, the MoS2The semi-circle diameter of the modified electrode is increased, which shows that the electron transfer rate is slow, the electron transfer resistance is gradually reduced along with the sequential modification of PPY and AuNPs on the surface of the electrode, which shows that the electron transfer rate at the interface of the electrode/solution is accelerated, and the results prove that the conductivity of the sensing system is improved by the gold nanoparticles and the polypyrrole-modified molybdenum disulfide nanosheets.
(6) Placing the above-mentioned electrode inGlucose was detected in 0.1M NaOH buffer, and in alkaline medium Cu (II) was oxidized to Cu (III), which is very oxidizing, converting glucose to gluconolactone. The detection method is Differential Pulse Voltammetry (DPV), the detection process is carried out on a CHI660D electrochemical workstation, and MoS before and after reaction2the-AuNPs-PPY-Cu (II)/GCE electrode is used as a working electrode, a platinum wire electrode is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, the detection solution is 0.1M NaOH buffer solution, and the detection parameters are as follows: the potential range is 0.1V-0.8V, the potential increment is 4mV, the amplitude is 25mV, and the frequency is 25 Hz. As shown in FIG. 4A, the peak current value gradually increased as the glucose concentration increased in the range of 0.1nM to 80 nM. Fig. 4B further reveals the relationship between the peak current change and the glucose concentration, and it can be seen that the method can achieve sensitive detection of glucose in the range of 0.1nM to 80nM, the detection limit of the method is 0.085nM calculated from the triple signal-to-noise ratio (S/N ═ 3), and the peak current and the glucose concentration in the linear range satisfy the following fitting equation:
I(μA)＝2.6142[glucose，nM]+3.6688
the correlation coefficient was 0.998.
Example 2: an N-CNF/AuNPs-based electrochemical sensing method for glucose detection.
1) 50mg of MoS are added separately2The powder was mixed with 50mL of N, N-Dimethylformamide (DMF) solution as an exfoliation and dispersing solvent and sonicated for 15 hours to obtain a homogeneous suspension. The prepared suspension was then centrifuged at 2000rpm for 5 minutes, then 12000rpm for 10 minutes, and finally MoS was obtained by vacuum freeze-drying2Nanosheet powder.
(2) Grinding a GCE electrode in alpha-alumina polishing powder suspension with the particle sizes of 1 mu m, 0.3 mu m and 50nm for 2 minutes in sequence, then placing the GCE electrode in absolute ethyl alcohol and high-purity water respectively for 5 minutes by ultrasonic treatment to remove alumina powder and organic matters adsorbed on the surface of the electrode, washing the electrode by high-purity water, and introducing N2Drying; the GCE electrode was immersed in 5mM HAuCl4Solution (containing 0.05 MH)2SO4And 0.05MNa2SO4) Middle passing circulation voltageThe AuNPs are electrodeposited by an ampere method, the potential range is-0.2V-1V, the scanning speed is 50mV/s, the number of scanning circles is 3, the electrode is washed by high-purity water and then N is introduced2Blow-drying, and marking the modified electrode as AuNPs/GCE.
(3) 5mg of MoS2And ultrasonically dispersing the nano-sheet powder into 10mL of high-purity water to obtain a uniform suspension liquid with the concentration of 0.5 mg/mL. Applying 20 μ L of the solution to the surface of AuNPs/GCE electrode, drying at room temperature until a uniform film is formed on the surface, wherein the electrode is marked as MoS2-AuNPs/GCE。
(4) Mixing MoS2Immersion of the-AuNPs/GCE electrode in a 0.2M pyrrole solution (containing 0.2M H)2SO4) In the method, pyrrole is electropolymerized by a current-time method, the potential is 0.5V, the scanning time is 400s, the electrode is washed by high-purity water and then N is introduced2Blow-drying, the modified electrode is marked as MoS2-AuNPs-PPY/GCE。
(5) Immersing the electrode in 0.2M CuCl2Incubate in solution for 0.5h, then rinse with high purity water and let in N2Blow drying, in which the Cu (II) has self-assembled to the surface of the electrode by complexation with polypyrrole, the electrode being labelled MoS2-AuNPs-PPY-Cu(II)/GCE。
(6) The electrode is placed in 0.1M NaOH buffer solution for detecting glucose, Cu (II) is oxidized into Cu (III) in an alkaline medium, and the Cu (III) has strong oxidizing property and converts the glucose into gluconolactone, so that the high-sensitivity detection of the glucose is realized, and the schematic diagram of the detection process is shown in figure 3. The detection method is Differential Pulse Voltammetry (DPV), the detection process is carried out on a CHI660D electrochemical workstation, and MoS before and after reaction2the-AuNPs-PPY-Cu (II)/GCE electrode is used as a working electrode, a platinum wire electrode is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, the detection solution is 0.1M NaOH buffer solution, and the detection parameters are as follows: the potential range is 0.1V-0.8V, the potential increment is 4mV, the amplitude is 25mV, and the frequency is 25 Hz.
Claims (2)
1. Based on MoS2The electrochemical sensing method for the enzyme-free detection of glucose by using the AuNPs-PPY composite material is characterized by comprising the following stepsThe following:
(1) immersing a glassy carbon electrode GCE with a polished surface into a solution with a molar ratio of 1: 10:10 HAuCl4、H2SO4And Na2SO4Mixing the solution with HAuCl4、H2SO4And Na2SO4The total molar concentration of the glass carbon electrode is controlled to be 0.1-2mM, scanning is carried out at 50mV/s within the range of-0.2V-1V through cyclic voltammetry, at the moment, reduction reaction of Au occurs on the surface of the glass carbon electrode, AuNPs are modified to the surface of the glass carbon electrode through an electrodeposition method, and the modified electrode is called AuNPs/GCE;
(2) preparation of MoS by ultrasonic exfoliation2Nanosheet: mixing MoS2Mixing the powder and a DMF solution according to a molar ratio of 1:1, and carrying out ultrasonic treatment for 10h-20h to obtain a uniform suspension; then centrifuging the prepared suspension at low speed of 1000rpm-3000rpm, then centrifuging at high speed of 10000rpm-13000rpm, and finally obtaining MoS by vacuum freeze drying2Nanosheets;
(3) MoS obtained in the step (2)2Dispersing the nanosheets in high-purity water to obtain a uniform suspension liquid with the concentration of 0.1-2 mg/mL; dropping the suspension on the surface of AuNPs/GCE with a dropping amount of 142 mug/cm2And standing at room temperature until a uniform film is formed, thus obtaining the MoS2-AuNPs/GCE；
(4) MoS obtained in the step (3)2-AuNPs/GCE infusion molar ratio 1: pyrrole of 1 and H2SO4In the mixture, pyrrole and H2SO4The total molar concentration of the mixed solution is controlled to be 0.1M, the mixed solution is scanned within the range of 0.3-0.6V by a current-time method, the scanning time is 200s-1000s, and MoS is obtained2-AuNPs-PPY/GCE；
(5) The MoS obtained in the step (4) is treated2-AuNPs-PPY/GCE electrode immersion in 0.01-0.2M CuCl2Culturing in solution for 1-2h to obtain MoS2-AuNPs-PPY-Cu(II)/GCE；
(6) Preparing a NaOH buffer solution with the molar concentration of 0.001-0.1M, and mixing the MoS obtained in the step (5)2-AuNPs-PPY-Cu (II)/GCE is placed in a mixed solution of glucose and NaOH, and the result is tested and analyzed by using differential pulse voltammetry; the test parameters are: electric potentialThe range is 0.1V-0.8V, the potential increment is 4mV, the amplitude is 25mV, and the frequency is 25 Hz.
2. MoS-based according to claim 12The electrochemical sensing method for enzyme-free detection of glucose by using the AuNPs-PPY composite material is characterized in that the ultrasonic treatment in the step (2) is controlled to be 25 ℃, and the freeze drying time is controlled to be 12 h.
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