CN108037167A - A kind of flexibility electrochemical glucose sensor - Google Patents

Abstract

This divisional application discloses a flexible glucose electrochemical sensor, which belongs to the technical field of electrochemical sensors. The substrate of the flexible electrode is PDMS, and there is a layer of dendritic nano-silver conductive layer on the PDMS substrate. The preparation method includes: self-assembly of ITO glass, electrochemical deposition of a dendritic nano-silver film layer on the ITO glass, placing the ITO glass with a nano-silver conductive layer in a PDMS solution for curing, and after curing, the PDMS film is removed from the ITO glass. The flexible glucose electrochemical sensor based on the dendritic nano-silver structure is obtained. The flexible glucose electrochemical sensor of the present invention has a good response to glucose and has a simple preparation method and is easy to carry out quantitative production. It is expected to be widely used in industry, agricultural production and life science research, especially in the field of wearable medical equipment.

Description

A flexible electrochemical sensor for glucose

The present invention is a divisional application with the application number 2017107651280, the application date of August 30, 2017, and the title of the invention "a flexible glucose electrochemical sensor based on a dendritic nano-silver structure".

technical field

The invention relates to the field of electrochemical sensors, in particular to a flexible glucose electrochemical sensor based on a dendritic nano-silver structure.

Background technique

Glucose is the most important substance in living organisms. Glucose metabolism is the most basic energy conversion pathway in organisms and the cornerstone of normal metabolism, growth and development of organisms. Glucose metabolism in animals will be affected by blood sugar concentration and insulin content. When blood sugar concentration is too high or insulin is lacking in the body, glucose metabolism disorder will occur and cause diabetes. Wide fluctuations in blood sugar lead to chronic complications of diabetes such as blindness, kidney failure, heart attack and stroke. Therefore, the monitoring of blood sugar has vital significance for evaluating people's health status.

At present, the methods for detecting glucose at home and abroad mainly include high performance liquid chromatography and spectrophotometry. Although these methods have high accuracy, the instruments used are expensive, the operation is complicated, and professional operators are required, which is time-consuming and labor-intensive. Electrochemical methods have aroused extensive interest of researchers due to their advantages of high sensitivity, easy operation, fast analysis speed and low cost. For example, a continuous glucose monitoring system (CGMS) is a successful application example of an electrochemical glucose sensor. The emergence of continuous blood glucose monitoring system (CGMS) provides complete trend information for blood glucose monitoring, and can provide high and low blood sugar alarm function, which can reduce the number of daily finger blood measurements of patients to 1-2 times, or even Calibration without finger blood is another important invention after finger blood glucose meter. At present, this type of sensor is usually based on a flexible polymer film, on which carbon electrodes or sputtered gold electrodes are printed, and an electrochemical three-electrode system is formed by layer-by-layer assembly or planar dislocation arrangement of electrodes; The working electrode and the reference electrode are separated by the insulating layer on the surface of the metal wire to form a two-electrode system. However, the sensor materials made by these methods are high in material cost, complex in process, and low in scale, which makes the production cost of such products high and expensive, which restricts the popularization and application of CGMS systems.

At present, the industrial blood glucose meter adopts the method of laboratory measurement after acupuncture blood collection. Although this measurement method is more accurate, it will cause some pain to the patient, and this method is intermittent to the measurement of blood sugar. The data can only provide the concentration of blood sugar at the time of measurement, and cannot give accurate guidance on the dosage of insulin each time. It is very important to continuously measure the concentration of glucose in the body. The current glucose sensor cannot be applied to the clinic. Continuously measuring the concentration of glucose in the system is one of the problems that researchers are currently facing. One of the main reasons is its rigidity. The structure makes the biocompatibility of the glucose sensor poor, so it is of great significance to construct a flexible electrochemical biosensor for glucose.

The key to the construction of a flexible glucose electrochemical biosensor is the flexible electrode material. The development of electrodes with the characteristics of simple manufacturing process, good glucose detection performance and flexibility (bending resistance) has a strong practical application prospect.

Contents of the invention

To solve the above problems, the object of the present invention is to provide a sensor with simple manufacturing process and good electrochemical response to glucose. A layer of nano-silver with a dendritic structure is deposited on the modified ITO glass by electrochemical deposition, and this layer of nano-silver is solidified on the PDMS flexible substrate, thereby preparing a new sensor with a dendritic structure of nano-silver . This sensor has a good electrochemical response to glucose.

The preparation method of the sensor is as follows:

1) The ITO glass is self-assembled layer by layer. Electrochemical deposition was carried out on the assembled ITO glass by chronoamperometry, the electrolyte used was a mixed solution of AgNO ₃ and NaNO ₃ , the reference electrode was a saturated mercurous sulfate electrode, the counter electrode was platinum wire, and the working electrode was an assembled ITO glass. After electrochemical deposition, a layer of white dendritic nano-silver will be deposited on the ITO glass, which is called ITO-Ag;

2) Immerse ITO-Ag into PDMS (polydimethylsiloxane), the volume ratio of PDMS stock solution and curing agent is 10:1, heat and cure, gently remove the cured PDMS flexible substrate from the ITO-Ag When it is peeled off, the white dendritic nano-silver is attached to the PDMS flexible substrate, which can be called PDMS-Ag. The PDMS-Ag is a sensor based on a dendritic nano-silver structure;

The response conditions of the sensor to glucose are as follows: the concentration of glucose is 5mM, the bottom solution is 5mM NaOH solution, the scanning range is -0.2-1.0V, and the scanning speed is 50mV/s.

Preferably, the number of self-assembled layers in the step (1) is 4-10 layers.

Preferably, the electrochemical deposition time in the step (1) is 400-1600s, and the potential range of the electrochemical deposition is (-0.6)-(-0.3)V.

Preferably, the AgNO ₃ concentration in the step (1) is 0.005-0.015 mol/L, and the NaNO ₃ concentration is 0.01-0.12 mol/L.

Preferably, the volume ratio of the PDMS stock solution to the curing agent in the step (2) is 10:1.

Preferably, the curing temperature in the step (2) is 50-100° C., and the curing time is 2-10 hours.

Significant advantages of the present invention: the present invention provides a light and durable sensor with excellent electrical conductivity. The preparation process of the electrode is simple, easy to achieve mass production and has good electrochemical response to glucose.

The key point of the invention lies in the electrochemical deposition of nano-silver with a dendritic structure on the ITO glass. This is because the dendritic nanostructure has many bifurcated structures, which increases the contact area between nano-silver branches, which is conducive to increasing electron transmission and reducing electrode resistance. Good electrical conductivity is the guarantee for the preparation of high-sensitivity electrochemical sensors. However, the electrochemical deposition method for the preparation of nano-silver conductive layer adopted by the present invention has the biggest advantage of being simple, easy to implement, good in repeatability, does not require synthesis and preparation, avoids the difficulties encountered in the synthesis and separation of nano-silver, and can solve the problem of nano-silver at the same time. Difficulties encountered in silver coating.

Description of drawings

Fig. 1 is the preparation method flowchart of sensor of the present invention;

Figure 2 is a microscope image of a sensor fabricated in accordance with the present invention;

Fig. 3 is the cyclic voltammetry curve of sensor according to the present invention to glucose response;

Fig. 4 is the test result of the bending resistance test of the sensor of the embodiment of the present invention;

Fig. 5 is the test result of the durability test of the sensor of the embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to the content of the embodiments in any form. Unless otherwise specified, the experimental methods described in the examples are conventional methods; unless otherwise specified, the experimental reagents and materials can be obtained from commercial sources.

Example 1

The ITO glass is self-assembled in 6 layers, and the ITO glass needs to be cleaned before assembly. The cleaning process is to ultrasonically clean the ITO glass with deionized water, acetone and ethanol for 30 minutes, respectively. After cleaning, put it into an ozone cleaner for surface hydroxylation. Then the ITO glass was self-assembled layer by layer in PDDA (polydiallyl dimethyl ammonium chloride) and PSS (polystyrene sodium sulfonate) solutions.

Deposit dendritic nano-silver on the assembled ITO glass, the method adopted is chronoamperometry, the reference electrode is a saturated mercurous sulfate electrode, the counter electrode is a platinum wire, the working electrode is an assembled ITO glass, and the electrolyte is AgNO ₃ and NaNO ₃ mixed solution, the deposition time is 400s, the concentration of AgNO ₃ is 0.008mol/L, the concentration of NaNO ₃ is 0.1mol/L, and the set potential is -0.3V. Through electrochemical deposition, a white nano-silver conductive layer is prepared on the surface of ITO glass, and its dendritic microscopic structure can be observed through a microscope or scanning electron microscope.

Put the silver-deposited ITO glass into the PDMS solution and put it into an oven for curing. The curing temperature is 70° C. and the curing time is 5 hours. The cured PDMS is peeled off from the ITO glass, and the dendritic nano-silver film will be fixed on the PDMS substrate, and the dendritic structure of the nano-silver conductive layer on the PDMS surface can be observed through a microscope. The obtained PDMS film with dendritic nano-silver can be used as the required flexible glucose electrochemical sensor.

Example 2

6-layer self-assembly of ITO glass. ITO glass needs to be cleaned before assembly. The cleaning process is to ultrasonically clean the ITO glass with deionized water, acetone and ethanol for 30 minutes, respectively. After cleaning, put it into an ozone cleaner for surface hydroxylation. Then the ITO glass was self-assembled layer by layer in PDDA and PSS solution.

Deposit dendritic nano-silver on the assembled ITO glass, the method adopted is chronoamperometry, the reference electrode is a saturated mercurous sulfate electrode, the counter electrode is a platinum wire, the working electrode is an assembled ITO glass, and the electrolyte is AgNO ₃ and NaNO ₃ mixed solution, the deposition time is 700s, the concentration of AgNO ₃ is 0.008mol/L, the concentration of NaNO ₃ is 0.1mol/L, and the set potential is -0.3V.

Put the silver-deposited ITO glass into the PDMS solution and put it into an oven for curing. The curing temperature is 70° C. and the curing time is 5 hours. The cured PDMS is peeled off from the ITO glass, and the dendritic nano-silver film will be fixed on the PDMS substrate, and the obtained PDMS film with dendritic nano-silver is a flexible electrochemical sensor for glucose.

Example 3

6-layer self-assembly of ITO glass. ITO glass needs to be cleaned before assembly. The cleaning process is to ultrasonically clean the ITO glass with deionized water, acetone and ethanol for 30 minutes, respectively. After cleaning, put it into an ozone cleaner for surface hydroxylation. Then the ITO glass was self-assembled layer by layer in PDDA and PSS solution.

Deposit dendritic nano-silver on the assembled ITO glass, the method adopted is chronoamperometry, the reference electrode is a saturated mercurous sulfate electrode, the counter electrode is a platinum wire, the working electrode is the previously assembled ITO glass, and the electrolyte is AgNO ₃ and NaNO ₃ mixed solution, the deposition time is 800s, the concentration of AgNO ₃ is 0.008mol/L, the concentration of NaNO ₃ is 0.1mol/L, and the set potential is -0.3V.

Put the silver-deposited ITO glass into the PDMS solution and put it into an oven for curing. The curing temperature is 70° C. and the curing time is 5 hours. The cured PDMS is peeled off from the ITO glass, and the dendritic nano-silver film will be fixed on the PDMS substrate, and the obtained PDMS film with dendritic nano-silver is a flexible electrochemical sensor for glucose.

Example 4

The ITO glass was self-assembled with 10 layers. The ITO glass was ultrasonically cleaned with deionized water, acetone, and ethanol for 40 minutes before assembly. After cleaning, put it into an ozone cleaner for surface hydroxylation. Then the ITO glass was self-assembled layer by layer in PDDA and PSS solution.

Deposit dendritic nano-silver on the assembled ITO glass, the method adopted is chronoamperometry, the reference electrode is a saturated mercurous sulfate electrode, the counter electrode is a platinum wire, the working electrode is the previously assembled ITO glass, and the electrolyte is AgNO ₃ and NaNO ₃ mixed solution, the deposition time is 1600s, the concentration of AgNO ₃ is 0.005mol/L, the concentration of NaNO ₃ is 0.12mol/L, and the set potential is -0.6V.

Put the silver-deposited ITO glass into the PDMS solution and put it into an oven for curing. The curing temperature is 100° C. and the curing time is 10 hours. The cured PDMS is peeled off from the ITO glass, and the dendritic nano-silver film will be fixed on the PDMS substrate, and the obtained PDMS film with dendritic nano-silver can be used as a flexible glucose electrochemical sensor.

Example 5

4-layer self-assembly of ITO glass. The ITO glass was ultrasonically cleaned with deionized water, acetone, and ethanol for 20 min, respectively, before assembly. After cleaning, put it into an ozone cleaner for surface hydroxylation. Then the ITO glass was self-assembled layer by layer in PDDA and PSS solution.

Deposit dendritic nano-silver on the assembled ITO glass, the method adopted is chronoamperometry, the reference electrode is a saturated mercurous sulfate electrode, the counter electrode is a platinum wire, the working electrode is the previously assembled ITO glass, and the electrolyte is The mixed solution of AgNO ₃ and NaNO3, the deposition time is 400s, the concentration of AgNO ₃ is 0.015mol/L, the concentration of NaNO ₃ is 0.01mol/L, and the set potential is -0.5V.

Put the silver-deposited ITO glass into the PDMS solution, put it into an oven for curing, the curing temperature is 50°C, and the curing time is 2 hours. The cured PDMS is peeled off from the ITO glass, and the dendritic nano-silver film will be fixed on the PDMS substrate, and the obtained PDMS film with dendritic nano-silver can be used as a flexible glucose electrochemical sensor.

Performance tests were performed on the samples obtained in Examples 1-5. After testing, the parameters of conductivity, bending resistance and sticking resistance of the samples in Examples 1-5 are shown in Table 1, Figure 4 and Figure 5 respectively.

Table 1: Conductive Properties of Sensors

sample Example 1 Example 2 Example 3 Example 4 Example 5 Square resistance (ohm/sq) 0.48 0.99 1.80 13.10 25.3

It can be seen from the data in Table 1 that the sheet resistance of the sensor increases with the increase of silver deposition time. Figure 4 shows the change in resistance of the sensor after 500 times of bending, and Figure 5 shows the change in resistance of the sensor after 500 times of tape sticking. From Figure 4 and Figure 5, it can be seen that the bending resistance and sticking resistance of the sensor also increase with the deposition time increased and enhanced.

Embodiment 6 glucose response experiment

The glucose response experiment was carried out on Chenhua CHI660 electrochemical workstation and three-electrode system. The reference electrode was a saturated mercurous sulfate electrode, the counter electrode was a platinum wire electrode, and the working electrode was the flexible glucose electrochemical sensor prepared in Example 2 of the present invention. For PDMS-Ag, use 0.2M NaOH solution as the base solution to prepare 5mM grape solution. The cyclic voltammetry curves of pure NaOH bottom solution and 5mM glucose solution with NaOH as bottom solution were made respectively, the scanning range was -0.2-1.0V, and the scanning speed was 50mV/s. The experimental results are shown in Figure 3. Compared with the cyclic voltammetry curve of pure NaOH bottom solution, two oxidation peaks appeared in the cyclic voltammetry curve of 5mM grape solution at potentials of 0.49V and 0.56V respectively, indicating that the electrode Good electrochemical response to glucose.

Claims (1)

1. a kind of flexibility electrochemical glucose sensor, it is characterised in that the flexible electrode includes flexible substrates PDMS and its table The embedding attached nano-silver conductive layer with dendritic structure in face；

The preparation method of the sensor comprises the following steps：

(1) by ito glass LBL self-assembly, electrochemical deposition silver is carried out on the ito glass assembled, obtains ITO-Ag；Institute It is AgNO with electrolyte₃And NaNO₃Mixed solution, reference electrode are saturation Mercurous sulfate electrode, are platinum filament to electrode, work electricity The ito glass extremely assembled；

(2) ITO-Ag is immersed in the PDMS solution containing curing agent, is heating and curing, by the PDMS flexible substrates being cured from Taken off on ITO-Ag, it is flexible electrochemical glucose sensor to obtain PDMS-Ag；

The sensor is to the response condition of glucose：The concentration of glucose is 5mM, and bottom liquid is the NaOH solution of 5mM, is scanned Scope -0.2-1.0V, it is 50mV/s to sweep speed；

The self assembly number of plies is 4~10 layers in the step (1)；

The electrochemical deposition time is 400~1600s in the step (1), the potential range that electrochemical deposition is set as (- 0.6)- (-0.3)V；

AgNO in the step (1)₃Concentration is 0.005-0.015mol/L, NaNO₃Concentration is 0.01-0.12mol/L；

PDMS stostes and the volume ratio of curing agent are 10 in the step (2)：1；

Solidification temperature described in the step (2) is 50-100 DEG C, when hardening time is 2-10 small.