CN114367672B - Silver-gold core-shell nanowire, enzyme-free glucose sensor electrode, preparation and detection - Google Patents
Silver-gold core-shell nanowire, enzyme-free glucose sensor electrode, preparation and detection Download PDFInfo
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Abstract
The invention relates to a silver-gold core-shell nanowire, an enzyme-free glucose sensor electrode, preparation and detection, wherein the enzyme-free glucose sensor uses the silver-gold core-shell nanowire as a working electrode, and the pre-strain and release treatment of a flexible substrate endows the silver-gold core-shell nanowire with large tensile and bending properties to ensure that the conductivity of the flexible working electrode prepared by the method can be effectively ensured in the bending and stretching states, and the catalytic performance of the flexible working electrode on glucose cannot be greatly reduced when the flexible working electrode is used for the enzyme-free glucose sensor electrode; the silver-gold core-shell nanowire electrode has good response to electrical analysis and detection of glucose, can bear deformation such as bending, stretching and the like, and is used for an enzyme-free glucose biosensor, so that the sensitivity of the sensor can reach 967 muA mM ‑1 cm ‑2 The linear range is 0.6-16mM, the detection limit is 125 mu M, and the anti-interference capacity on ascorbic acid, uric acid, dopamine and sodium chloride is excellent.
Description
Technical Field
The invention relates to the field of electrochemical sensors, in particular to a silver-gold core-shell nanowire, an enzyme-free glucose sensor electrode, preparation and detection.
Background
Diabetes is a common metabolic disorder complex disease, can cause various complications such as stroke in the brain, blindness, renal failure, coronary heart disease, lower limb necrosis and the like without being controlled, and seriously threatens the health of people. The complications can greatly reduce the morbidity degree of the human body by accurately controlling the blood sugar concentration of the human body, and even can not cause the disease. Therefore, the detection of glucose levels in blood is of paramount importance as the only standard for clinical diagnosis of diabetes. Among many methods for detecting glucose content, such as chromatography, spectrophotometry, and electrochemical methods, electrochemical glucose sensors have been widely studied for their advantages of accuracy, high reliability, ease of operation, and low cost. At present, electrochemical glucose sensors can be classified into enzymatic glucose sensors and non-enzymatic glucose sensors according to whether the working electrode contains an enzyme or not. The enzyme-free glucose sensor is not interfered by the temperature, humidity and pH of the environment and can maintain excellent stability and high sensitivity, so that the enzyme-free glucose sensor is widely concerned by a large number of researchers.
Currently, most commercially available blood glucose meters adopt an invasive measurement method, namely, blood sampling by needle stick, which brings pain and infection risks to patients and cannot monitor blood glucose concentration in real time. Research has shown that there is a relationship between sweat glucose content and blood glucose content, allowing flexible glucose sensors to be worn on the surface of the body to detect glucose content in real time with sweat. The flexible wearable glucose sensor is used for non-invasive detection, can adapt to human joint deformation to realize real-time continuous monitoring, and is a research hotspot in the field of current enzyme-free glucose sensing.
The core of a flexible enzyme-free glucose sensor is a flexible working electrode, usually consisting of a flexible substrate and an electrically conductive material. However, in the electrode of the existing flexible glucose sensor, the conductivity of the electrode is still difficult to effectively ensure under the bending and stretching states, and the catalytic performance of the electrode on glucose is greatly reduced.
Disclosure of Invention
The invention aims to solve the defects that the conductivity of a flexible enzyme-free glucose sensor electrode in a bent and stretched state is difficult to effectively ensure and the catalytic performance of the flexible enzyme-free glucose sensor electrode on glucose is greatly reduced in the prior art, and provides a silver-gold core-shell nanowire, an enzyme-free glucose sensor electrode, and preparation and detection methods thereof. The silver-gold core-shell nanowire flexible electrode has the advantages of simplicity in preparation, high sensitivity, wide linear range, good selectivity, flexibility, stretching and the like.
The above technical object of the present invention will be achieved by the following technical means.
A preparation method of silver-gold core-shell nanowires comprises the following steps:
s1: dissolving tetrachloroauric acid trihydrate, sodium sulfite and sodium hydroxide in deionized water to serve as a growth solution, and standing for later use;
s2: dissolving polyvinylpyrrolidone, sodium hydroxide, ascorbic acid and sodium sulfite in another deionized water, and adding the silver nanowire dispersion liquid as a main solution for later use;
s3: and injecting the growth solution of the S1 into the main body solution of the S2 to prepare the silver-gold core-shell nanowire.
There is further provided in accordance with the above-mentioned aspect and any possible implementation manner an implementation manner, in S1, the molar ratio of tetrachloroauric acid trihydrate, sodium sulfite, and sodium hydroxide is 1.
The aspect described above and any possible implementation manner further provide an implementation manner, in the S2, a molar ratio of sodium hydroxide, ascorbic acid and sodium sulfite is 1.01 to 0.1, a mass fraction of the polyvinylpyrrolidone is 2 to 8wt%, and a concentration of the silver nanowire dispersion is 0.05 to 1.0mg/mL.
In the above aspect and any possible implementation manner, there is further provided an implementation manner, in S3, the injection speed is 0.01 to 0.5mL/min, the reaction temperature is 50 to 80 ℃, and sodium hydroxide is continuously added at the same time, so as to adjust the pH of the silver-gold core-shell nanowire suspension to 9 to 10.
The invention also provides a silver-gold core-shell nanowire prepared by the preparation method.
The above aspects and any possible implementations further provide an implementation where the silver-gold core-shell nanowire has a diameter of 20 to 30nm and a length of about 20 μm.
The invention also provides a flexible enzyme-free glucose sensor electrode of the silver-gold core-shell nanowire, which is prepared by the following steps:
(1) Washing the silver-gold core-shell nanowire with ethanol and water for multiple times, and then re-dispersing in the water to obtain a silver-gold core-shell nanowire suspension;
(2) Filtering the silver-gold core-shell nanowire suspension obtained in the step (1) through a filter membrane to obtain a silver-gold core-shell nanowire network taking the filter membrane as a substrate, and transferring the silver-gold core-shell nanowire network from the filter membrane to a pre-strained flexible substrate to obtain a flexible electrode;
(3) And treating the flexible electrode by mixed steam to enable the silver-gold core-shell nano network in the flexible electrode to be subjected to induced welding, and slowly releasing the pre-strain of the flexible substrate to obtain the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode.
As to the above-mentioned aspect and any possible implementation manner, there is further provided an implementation manner, in which the flexible substrate in the step (2) is an elastomer film, and the pre-strain of the flexible substrate is 50% to 300%.
The above aspect and any possible implementation manner further provide an implementation manner, in the step (3), the mixed steam is a mixture of the water and the methanol, the volume ratio of the water to the methanol is 5.
The invention also provides a detection method of the enzyme-free glucose sensor electrode, which comprises the following steps:
step (1): taking the enzyme-free glucose sensor electrode as a working electrode, taking saturated silver | silver chloride as a reference electrode, taking a platinum sheet as a counter electrode, and inserting the working electrode, the reference electrode and the counter electrode into a sodium hydroxide solution with the concentration of 0.05-0.5M;
step (2): continuously adding a glucose solution into the sodium hydroxide solution in the step (1) to form a mixed solution, and detecting the mixed solution by adopting a current-voltage cyclic voltammetry to carry out glucose electrocatalytic oxidation;
and (3): and (3) carrying out data processing on the electric signal detection result obtained by the detection in the step (2) and the glucose concentration to obtain the corresponding relation between the electric signal and the glucose concentration.
The invention has the beneficial technical effects
(1) The invention uses the silver-gold core-shell nanowire as the working electrode, does not use the traditional GCE and ITO conductive substrate, and reduces the cost of raw materials.
(2) The silver-gold core-shell nanowire is used as the working electrode, and the silver-gold core-shell nanowire is tightly attached to the flexible substrate through the strong adhesion of the flexible substrate, so that the fixation operation of an adhesive is avoided, the cost is reduced, and the operation steps are reduced.
(3) The silver-gold core-shell nanowire is used as a working electrode, the buckling structure silver-gold core-shell nanowire flexible electrode is endowed with large stretching and bending properties through the pre-straining and releasing treatment of the flexible substrate, and the resistance of the prepared flexible electrode is kept unchanged in various bending and stretching states. The conductivity of the flexible working electrode prepared by the method can be effectively ensured in the bending and stretching states, and the catalytic performance of the flexible working electrode on glucose can not be greatly reduced when the flexible working electrode is used for an enzyme-free glucose sensor electrode.
(4) The silver-gold core-shell nanowire electrode prepared by the invention has good response to the electrical analysis and detection of glucose, can bear deformation such as bending, stretching and the like, is used for an enzyme-free glucose biosensor, and has the sensitivity of 967 muA mM -1 cm -2 The linear range is 0.6-16mM, the detection limit is 125 mu M, and the anti-interference capacity to ascorbic acid, uric acid, dopamine and sodium chloride is excellent.
Drawings
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a schematic flow chart of the preparation of a silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode in an embodiment of the present invention;
FIG. 2 is a scanning electron micrograph of silver-gold core-shell nanowires prepared in the present invention;
FIG. 3 is a scanning electron microscope image of the silver-gold core-shell nanowires obtained by the present invention, which are subjected to capillary force induced welding;
FIG. 4 (a) is a cyclic voltammogram of the silver-gold core-shell nanowires of the present invention used as an enzyme-free glucose sensor electrode upon dropping glucose of different concentrations,
FIG. 4 (b) is a graph of the linear relationship between the response current and the glucose concentration of the silver-gold core-shell nanowire of the present invention used as an electrode of an enzyme-free glucose sensor;
FIG. 5 is a schematic diagram of the anti-interference performance of the flexible enzyme-free glucose sensor electrode of the silver-gold core-shell nanowire of the present invention for glucose detection;
FIG. 6 is a graph of resistance of a silver-gold core-shell nanowire flexible electrode of the present invention as a function of uniaxial tension;
FIG. 7 is a plot of cyclic voltammetry for glucose for a prior art unbent flexible enzyme-free glucose electrochemical sensor and a curved flexible enzyme-free glucose electrochemical sensor with a radius of curvature of 0.637 mm;
FIG. 8 is a plot of cyclic voltammetry for glucose for an unstretched flexible enzyme-free glucose electrochemical sensor and a flexible enzyme-free glucose electrochemical sensor under different stretching conditions.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description is made with reference to the accompanying drawings and specific examples, but the embodiments of the present invention are not limited thereto.
A preparation method of a silver-gold core-shell nanowire flexible electrode comprises the following steps:
s1: dissolving tetrachloroauric acid trihydrate, sodium sulfite and sodium hydroxide in deionized water to serve as a growth solution, and standing for later use;
s2: dissolving polyvinylpyrrolidone, sodium hydroxide, ascorbic acid and sodium sulfite in another deionized water, and adding the silver nanowire dispersion liquid as a main solution for later use;
s3: and injecting the growth solution of the S1 into the main body solution of the S2 to prepare the silver-gold core-shell nanowire.
Preferably, in the S1, the molar ratio of the tetrachloroauric acid trihydrate, the sodium sulfite and the sodium hydroxide is 1.
Preferably, in S2, the molar ratio of sodium hydroxide, ascorbic acid and sodium sulfite is 1.
Preferably, in the step S3, the injection speed is 0.01 to 0.5mL/min, the silver-gold core-shell nanowire with a smooth and flat surface is ensured to be obtained within the injection speed range, the reaction temperature is 50 to 80 ℃, the reaction rate is accelerated within the temperature range, sodium hydroxide is continuously added, the pH value of the silver-gold core-shell nanowire suspension is adjusted to be 9 to 10, and the agglomeration of the silver-gold core-shell nanowire is avoided within the pH range.
Preferably, the invention also provides a silver-gold core-shell nanowire prepared by the preparation method.
Preferably, the invention also provides a flexible enzyme-free glucose sensor electrode of the silver-gold core-shell nanowire, which is prepared by adopting the silver-gold core-shell nanowire, and comprises the following steps:
(1) Washing the silver-gold core-shell nanowire with ethanol and water for multiple times, and then re-dispersing in the water to obtain a silver-gold core-shell nanowire suspension;
(2) Filtering the silver-gold core-shell nanowire suspension obtained in the step (1) through a filter membrane to obtain a silver-gold core-shell nanowire network taking the filter membrane as a substrate, and transferring the silver-gold core-shell nanowire network from the filter membrane to a pre-strained flexible substrate to obtain a flexible electrode;
(3) And treating the flexible electrode by mixed steam to enable the silver-gold core-shell nano network in the flexible electrode to be subjected to induced welding, and slowly releasing the pre-strain of the flexible substrate to obtain the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode.
Preferably, in the step (2), the flexible substrate is an elastomer film and has a very strong adhesive force, and the pre-strain of the flexible substrate is 50% to 300%, and in this strain range, the flexible electrode is endowed with a large tensile bending performance.
Preferably, in the step (3), the mixed vapor is a mixture of the water and the methanol, the volume ratio of the water to the methanol is 5-1, and in the volume ratio range, the effects of removing the polyvinylpyrrolidone on the surface of the silver-gold core-shell nanowire and welding the nanowire can be achieved simultaneously; the methanol can dissolve the polyvinylpyrrolidone, the processing time is 5-60 min, and the excellent nanowire welding effect can be achieved within the processing time range without damaging the structure of the silver-gold core-shell nanowire.
Preferably, the filter membrane in the step (2) is a mixed cellulose membrane or a polytetrafluoroethylene membrane, the pore diameter is 0.20-0.25 μm, the diameter is 40-60mm, and the silver-gold core-shell nanowire network obtained by filtration is compact and uniform within the range of the pore diameter and the diameter.
Preferably, the invention also provides a detection method of the enzyme-free glucose sensor electrode, which comprises the following steps:
step (1): taking the enzyme-free glucose sensor electrode as a working electrode, taking saturated silver | silver chloride as a reference electrode and a platinum sheet as a counter electrode, and inserting the working electrode, the reference electrode and the counter electrode into a sodium hydroxide solution with the concentration of 0.05-0.5M;
step (2): continuously adding a glucose solution into the sodium hydroxide solution in the step (1), and detecting the electrocatalytic oxidation of glucose by adopting a current-voltage cyclic voltammetry testing technology;
and (3): and (3) carrying out data processing on the electric signal detection result obtained in the step (2) and the glucose concentration to obtain the corresponding relation between the electric signal and the glucose concentration.
Specifically, the preparation of the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode comprises two steps: the preparation of the silver-gold core-shell nanowire and the suspension and the preparation of the flexible enzyme-free glucose sensor electrode comprise the following detailed preparation processes:
1. preparation of silver-gold core-shell nanowires and suspensions
Preparation of silver-gold core-shell nanowires
Step 1: dissolving tetrachloroauric acid trihydrate, sodium sulfite and sodium hydroxide in deionized water to serve as a growth solution, standing for 3-8 hours for later use, and in the step, converting the tetrachloroauric acid trihydrate into a sodium gold sulfite complex;
and 2, step: dissolving polyvinylpyrrolidone, sodium hydroxide, ascorbic acid and sodium sulfite in another deionized water, and adding the silver nanowire dispersion liquid as a main solution for later use; in the step, under an alkaline condition, the ascorbic acid and sodium sulfite act synergistically to reduce the gold sodium sulfite complex obtained in the step 1 into gold nanoparticles, and the silver nanowires are uniformly dispersed in the main body solution;
and 3, step 3: injecting the growth solution of the step 1 into the main body solution of the step 2 by using a syringe pump; in the step, the growth solution is slowly injected into the main solution, so that the growth solution and the main solution react to generate the silver-gold core-shell nanowire with a smooth and flat surface.
Preferably, the present invention may further include step 4: continuously adding sodium hydroxide, adjusting the pH value of the silver-gold core-shell nanowire system to be about 9-10, and obtaining the silver-gold core-shell nanowire; in the step, the pH value is adjusted to be kept between 9 and 10, and the prepared silver-gold core-shell nanowire is prevented from being agglomerated;
preparation of silver-gold core-shell nanowire suspension
And 5: washing the silver-gold core-shell nanowire obtained in the step 3 or 4 with ethanol and water for multiple times, and then re-dispersing in the water to obtain a silver-gold core-shell nanowire suspension; in the step, redundant impurities are washed away by ethanol and water, so that the silver-gold core-shell nanowire suspension is purer.
In the step 1, the molar ratio of the tetrachloroauric acid trihydrate, sodium sulfite and sodium hydroxide is 1.
In the step 2, the molar ratio of sodium hydroxide, ascorbic acid and sodium sulfite is 1; the mass fraction of the polyvinylpyrrolidone is 2-8 wt%, and in the proportion range, the gold nanoparticles are induced to grow on the surface of the silver nanowire, and a layer of polyvinylpyrrolidone protective shell is generated on the surface of the silver-gold core-shell nanowire; the concentration of the silver nanowire dispersion liquid is 0.05-1.0 mg/mL, and in the proportion range, the silver nanowires are spread as far as possible, so that the bent part is prevented from cracking.
In the step 3, the injection speed is 0.01-0.5 mL/min, the silver-gold core-shell nanowire with a smooth and flat surface is ensured to be obtained within the injection speed range, the reaction temperature is 50-80 ℃, and the reaction rate can be accelerated within the temperature range.
In the step 5, the diameter of the obtained silver-gold core-shell nanowire is 20-30 nm, and the length of the obtained silver-gold core-shell nanowire is about 20 microns, and in the step, the prepared silver-gold core-shell nanowire is uniform in diameter and length and can be used as a subsequent flexible enzyme-free glucose sensor electrode.
2. Preparation of silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode
And (2) filtering the silver-gold core-shell nanowire suspension in the step (1) through a filter membrane to obtain a silver-gold core-shell nanowire network taking the filter membrane as a substrate, and transferring the silver-gold core-shell nanowire network from the filter membrane to a pre-strained flexible substrate to obtain a flexible electrode. The flexible electrode is treated with a mixed vapor containing water and methanol and then dried at room temperature, allowing the nano-network to induce soldering under the capillary force generated during evaporation of the mixed vapor. In the process, the modulus of the silver-gold core-shell nanowire is several orders of magnitude greater than that of the flexible substrate, so that when the pre-strained flexible substrate is released, the flexible substrate retracts, and the silver-gold core-shell nanowire has the tendency of maintaining the original shape so as to inhibit the deformation of the silver-gold core-shell nanowire, thereby forming the flexible electrode with the buckling structure.
The concentration of the suspension of the silver-gold core-shell nanowire is 0.05-0.5 mg/mL, and in the concentration range, the prepared flexible electrode shows excellent conductivity and electrocatalysis performance on glucose.
The filter membrane is a mixed cellulose membrane or a polytetrafluoroethylene membrane, the experimental effect of the invention can be realized by the two filter membranes with the aperture of 0.22 mu m and the diameter of 50mm, and the silver-gold core-shell nanowire network obtained by filtering is compact and uniform within the range of the aperture and the diameter.
The flexible substrate is a polyacrylate elastomer VHB or silicone rubber (comprising polydimethylsiloxane PDMS and copolyester Ecoflex) and has strong adhesion.
The pre-strain of the flexible substrate is 50% -300%, and in the strain range, the flexible electrode is endowed with large tensile bending performance.
The volume ratio of the mixed steam of the water and the methanol is 5-1, and in the volume ratio range, the effects of removing the polyvinylpyrrolidone layer on the surface of the silver-gold core-shell nanowire and welding the nanowire can be achieved simultaneously; the methanol can dissolve the polyvinylpyrrolidone, the processing time is 5-60 min, and the excellent nanowire welding effect can be achieved within the processing time range without damaging the structure of the silver-gold core-shell nanowire.
Preferably, the invention also provides a detection method of the flexible enzyme-free glucose electrochemical sensor based on the silver-gold core-shell nanowire electrode, which comprises the following steps:
step (1): adopting a three-electrode system, taking the prepared silver-gold core-shell nanowire flexible electrode as a working electrode, taking saturated silver | silver chloride as a reference electrode and a platinum sheet as a counter electrode, and inserting the three electrodes, namely the working electrode, the reference electrode and the counter electrode, into a sodium hydroxide solution with the concentration of 0.05-0.5M;
step (2): continuously adding a glucose solution into the sodium hydroxide solution in the step (1), and detecting the electrocatalytic oxidation of glucose by adopting a current-voltage cyclic voltammetry testing technology;
and (3): and (3) carrying out data processing on the electric signals of the series of cyclic voltammetry curves measured in the step (2) and the glucose concentration to obtain a corresponding table or a functional relation of the electric signals and the glucose concentration.
Preferably, step (4) may also be included: and (3) respectively bending and stretching the working electrode of the silver-gold core-shell nanowire flexible electrode in the step (1), and continuing to perform the cyclic voltammetry test in the step (2), so that an electrocatalysis test curve of the working electrode to glucose in a bent and stretched state can be obtained.
In the step (1), the size of the working electrode is about 0.4cm multiplied by 0.5cm, the working electrode is simple to prepare within the size range, and the sample is saved.
In the step (2), the voltage range during the potential sweeping is-0.75V-1.0V, and all peak potentials in the glucose electrocatalytic oxidation cyclic voltammetry curve are included in the voltage range.
In the step (2), the sweep rate during potential sweeping is 10-50mV/s, and within the sweep rate range, the obtained cyclic voltammetry curve is smooth and flat, and the peak current signal is obvious.
In the step (2), the working temperature is preferably 25-30 ℃, and the glucose electrocatalytic oxidation detection system stably works in the temperature range.
The detection result in the step (3) shows that the response current has an ascending trend along with the increase of the glucose concentration and has a linear relation in the range of 0.6-16mM, and the sensitivity of the sensor can reach 967 muA mM -1 cm -2 Compared with the prior art, the sensitivity is obviously improved.
The detection result in the step (4) shows that the catalytic performance of the flexible electrode of the silver-gold core-shell nanowire on glucose is not influenced when the flexible electrode bears deformation such as bending, stretching and the like, is obviously enhanced compared with the prior art, and the problem provided by the invention is solved.
Example 1:
the preparation method of the silver-gold core-shell nanowire glucose sensor electrode material comprises the following steps:
1) Mixing 0.14mL of 0.25M (wherein M represents mol/L, international general Unit) tetrachloroauric acid trihydrate, 0.86mL of 0.2M sodium hydroxide, 1.05mL of 0.1M sodium sulfite, and 7.95mL of water to prepare a growth solution, and standing for 5 hours;
2) 32mL of water, 7mL of 5wt% polyvinylpyrrolidone (weight average molecular weight 40,000), 1.4mL of 0.5M sodium hydroxide, 1.4mL of 0.5M ascorbic acid, 0.35mL of 0.1M sodium sulfite, and 10mL (1.0 mg/mL) of silver nanowires were mixed to prepare a bulk solution;
3) Adding the growth solution in the step 1) into the main solution in the step 2) at 60 ℃ by using a syringe pump at an injection rate of 0.02mL/min until the growth solution is completely added into the main solution;
4) Simultaneously continuously adding 0.5M sodium hydroxide into the main solution, and adjusting the pH value of the silver-gold core-shell nanowire suspension to be about 9-10;
5) Washing the obtained silver-gold core-shell nanowire with ethanol and water for multiple times, and then re-dispersing the silver-gold core-shell nanowire in 40mL of water to obtain a silver-gold core-shell nanowire suspension, as shown in FIG. 2;
the average diameter of the silver-gold core-shell nanowire is 27.5nm, and the length of the silver-gold core-shell nanowire is about 20 mu m.
The concentration of the dispersion liquid of the silver-gold core-shell nanowire is 0.1mg/mL.
6) Dispersing 4mL of the silver-gold core-shell nanowire suspension in the step 5) in 16mL of water, and performing vacuum filtration through a filter membrane;
the filter membrane is a mixed cellulose membrane, the aperture is 0.22 mu m, and the diameter is 50mm.
7) Transferring the silver-gold core-shell nanowire network in the step 6) from the filter membrane to a pre-strained flexible substrate to obtain a flexible electrode;
the flexible substrate is VHB 4910 and has extremely strong adhesion.
The pre-strain of the flexible substrate is 200%.
8) Treating the flexible electrode in the step 7) by mixed steam containing water and methanol for 15min, and then drying at room temperature, thereby allowing the nano network to induce welding under the action of capillary force generated in the evaporation process of the mixed steam, as shown in fig. 3;
the volume ratio of the mixed steam of water and methanol is 3.
9) And slowly releasing the pre-strained flexible substrate to obtain the flexible enzyme-free glucose sensor electrode with the silver-gold core-shell nanowire in the buckling structure.
Example 2:
the silver-gold core-shell nanowire electrode prepared in example 1 is considered to be applied to the reaction of glucose catalytic oxidation in the electrical analysis, and the experimental process comprises the following steps:
1) Weighing 0.1600g of sodium hydroxide, dissolving in 40mL of water, and preparing into 0.1M sodium hydroxide solution;
2) Weighing 1.0809g of glucose, dissolving in 30mL of water, and preparing into a 0.2M glucose solution as a target object;
3) Electrochemical tests were performed using an electrochemical workstation (CS 310) and a three-electrode system: taking saturated silver | silver chloride as a reference electrode, a platinum sheet as a counter electrode, and the silver-gold core-shell nanowire electrode prepared in example 1 as a working electrode, wherein the detection range of electrochemical cyclic voltammetry detection is-0.75-1.0V, and the scanning rate is 30mV/s;
4) Performing linear sweep voltammetry testing by using the electrochemical workstation (CS 310), the three-electrode system and the testing parameters established in the step 3), taking 10mL of the sodium hydroxide solution prepared in the step 1), transferring the sodium hydroxide solution into a 50mL detection bottle to be used as an electrolyte solution, and performing electrochemical cyclic voltammetry scanning after the working electrode is stabilized to obtain a Cyclic Voltammogram (CV) with the glucose concentration of 0; a further addition of 0.2M glucose solution with stirring resulted in a linear current versus glucose concentration curve in the glucose concentration range from 0.6 to 16mM, as shown in FIG. 4.
As can be seen from fig. 4 (a), when cyclic voltammetry scans were performed on glucose solutions of different concentrations by using the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode prepared in example 1, two distinct glucose oxidation peaks appeared at-0.25V and 0.28-0.4V in the positive direction scan, and a third glucose oxidation peak appeared at 0.11V in the negative direction scan. As shown in FIG. 4 (b), the peak current corresponding to the third oxidation peak was taken as the lineThe peak current signal of the linear regression equation has a linear relation with the glucose concentration within the range of 0.6-16mM of the glucose concentration, and the linear equation is as follows: y =0.9674x-1.1007, R =0.9991 (y: peak current; x: glucose concentration; R: standard deviation), and the sensitivity of the sensor can reach 967 muA mM -1 cm -2 Compared with the prior art, the sensitivity is obviously improved. Therefore, the flexible enzyme-free glucose sensor electrode prepared by the method has high sensitivity and wide detection range for detecting the oxidation reaction of glucose by electroanalysis.
Example 3:
human blood contains some reducing carbohydrates, such as ascorbic acid, uric acid, dopamine, sodium chloride and the like, which may interfere with the detection of glucose, and the detection method examines whether the substances interfere with the detection of glucose or not under the condition that the concentrations of the ascorbic acid, the uric acid and the dopamine are all 0.1mM and the concentration of the sodium chloride is 0.1M by referring to normal human physiological levels, and comprises the following steps:
1) The experiment adopts an I-t method, and utilizes an electrochemical workstation (CS 310) and a three-electrode system to carry out electrochemical test: the silver-gold core-shell nanowire prepared in example 1 was used as a working electrode with a scanning rate of 30mV/s, with saturated silver | silver chloride as a reference electrode and a platinum sheet as a counter electrode;
2) Respectively preparing 0.1M sodium hydroxide solution, 0.1M ascorbic acid solution, 0.1M dopamine solution, 0.1M uric acid solution, 100M sodium chloride solution and 0.2M glucose solution for later use;
3) The electrochemical workstation (CS 310), the three-electrode system and the test parameters established in the step 1) are used for testing, firstly, 2mL of 0.1M NaOH solution is added into a reaction bottle, the experiment is started, 10 muL of glucose solution, 20 muL of glucose solution, 2 muL of ascorbic acid solution, 2 muL of uric acid solution, 2 muL of dopamine solution and 2 muL of sodium chloride solution prepared in the step 2) are sequentially added, the timing current detection is carried out, and the test result is shown in figure 5.
In fig. 5, ascorbic acid, uric acid, dopamine, sodium chloride and Glucose are labeled AA, UA, DA, naCl and Glucose, respectively. As can be seen from figure 5, the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode has great current response to glucose, and has only small current response after AA, UA, DA and NaCl are added, and the current response is almost negligible, so that the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode is proved to have excellent anti-interference performance.
Example 4:
in order to investigate the possibility of the silver-gold core-shell nanowire electrode prepared in example 1 on a flexible enzyme-free glucose sensor, the flexible enzyme-free glucose sensor electrode prepared by the above preparation method was subjected to a tensile conductivity test, and the conductivity of the electrode in different tensile states when the electrode was released by stretching was tested, and the following steps were performed:
1) Cutting the flexible electrode obtained in the embodiment 1 into a strip sample of about 0.5 multiplied by 0.4cm to be measured;
2) The samples of 1) were tested for resistance under tension by a universal tensile machine and a Keithley 2450 power supply.
The drawing rate was 13mm/min.
The results are shown in fig. 6, and it can be seen from the test results that the flexible enzyme-free glucose sensor electrode prepared by the invention can still maintain excellent conductivity when being stretched to 150%, which means that the flexible enzyme-free glucose sensor electrode has great application potential in the development of flexible devices.
To further explore the utility of the silver-gold core-shell nanowire electrode prepared in example 1 on a flexible enzyme-free glucose sensor, we performed glucose response tests on the flexible enzyme-free glucose sensor electrode in a natural state, a bent state, and a stretched state based on the silver-gold core-shell nanowire electrode prepared in example 1 as a working electrode. The glucose response test adopts cyclic voltammetry, and comprises the following steps:
3) Weighing 0.1600g of sodium hydroxide, dissolving in 40mL of water, and preparing into 0.1M sodium hydroxide solution;
4) Weighing 1.0809g of glucose, dissolving in 30mL of water, and preparing into a 0.2M glucose solution as a target object;
5) Electrochemical tests were performed using an electrochemical workstation (CS 310) and a three-electrode system: taking saturated silver | silver chloride as a reference electrode and a platinum sheet as a counter electrode, taking the silver-gold core-shell nanowire electrode obtained in the step 1) as a working electrode, and carrying out electrochemical cyclic voltammetry detection with the detection range of-0.75-0.75V and the scanning rate of 30mV/s;
6) Performing linear sweep voltammetry testing by using the electrochemical workstation (CS 310), the three-electrode system and the testing parameters established in the step 5), taking 10mL of the sodium hydroxide solution prepared in the step 3) and 100 μ L of the glucose solution prepared in the step 4), adding the sodium hydroxide solution and the glucose solution into a 50mL detection bottle to serve as electrolyte solutions, and performing electrochemical cyclic voltammetry scanning after the working electrode is stabilized to obtain a CV diagram in a natural state;
7) Bending the working electrode in the step 6) to the curvature radius of 0.637mm, and continuing to perform electrochemical cyclic voltammetry scanning to obtain a CV diagram in a once-bent state;
8) Bending the working electrode in the step 6) to the curvature radius of 0.637mm, repeatedly bending for 100 times, and continuously performing electrochemical cyclic voltammetry scanning to obtain a CV diagram in a state of bending for 100 times;
as shown in FIG. 7, the current response of the electrode to glucose before and after bending is basically not deviated, and after 100 times of bending, the current response is still almost unchanged, and the repeated flexibility of the flexible enzyme-free glucose electrochemical sensor with the silver-gold core-shell nanowire electrode is proved.
Further, we performed a current response test of the silver-gold core-shell nanowire electrode on the flexible enzyme-free glucose sensor in a tensile state.
9) Performing linear sweep voltammetry testing by using the electrochemical workstation (CS 310), the three-electrode system and the testing parameters established in the step 5), taking 10mL of the sodium hydroxide solution prepared in the step 3) and 250 μ L of the glucose solution prepared in the step 4), adding the sodium hydroxide solution and the glucose solution into a 50mL detection bottle to serve as electrolyte solutions, and performing electrochemical cyclic voltammetry scanning after the working electrode is stabilized to obtain a CV diagram in a natural state;
10 The working electrode is stretched, and electrochemical cyclic voltammetry scanning is continued to obtain CV diagrams under different stretching states.
As shown in FIG. 8, the flexible electrochemical glucose sensor electrode has only a small current response loss when being stretched to 50%, and the 50% value meets the wearable deformation of a human body. Until it is stretched to 100%, the current response is lost. This demonstrates the excellent tensile resistance of the flexible electrochemical glucose sensor electrode.
While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not intended to be exhaustive or to exclude other embodiments and may be used in various other combinations, modifications, and environments and is capable of changes within the scope of the invention as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. The preparation method of the silver-gold core-shell nanowire is characterized by comprising the following steps:
s1: dissolving tetrachloroauric acid trihydrate, sodium sulfite and sodium hydroxide in deionized water to serve as a growth solution, and standing for later use, wherein the molar ratio of the tetrachloroauric acid trihydrate, the sodium sulfite and the sodium hydroxide is 1;
s2: dissolving polyvinylpyrrolidone, sodium hydroxide, ascorbic acid and sodium sulfite in another deionized water, and adding a silver nanowire dispersion as a main solution for standby, wherein the molar ratio of the sodium hydroxide to the ascorbic acid to the sodium sulfite is 1.01-0.1, the mass fraction of the polyvinylpyrrolidone is 2-8 wt%, and the concentration of the silver nanowire dispersion is 0.05-1.0 mg/mL, in the step, under an alkaline condition, the ascorbic acid and the sodium sulfite act synergistically to reduce the gold sodium sulfite complex obtained in the step S1 into gold nanoparticles, and the silver nanowires are uniformly dispersed in the main solution;
s3: and (3) injecting the growth solution of the S1 into the main body solution of the S2 at the injection speed of 0.01-0.5 mL/min and the reaction temperature of 50-80 ℃, continuously adding sodium hydroxide, adjusting the pH value of the silver-gold core-shell nanowire suspension to be 9-10, and preparing the silver-gold core-shell nanowire with the end convex morphology.
2. A silver-gold core-shell nanowire with a tip-protruding morphology, characterized in that the silver-gold core-shell nanowire is prepared by the preparation method of claim 1.
3. The silver-gold core-shell nanowire according to claim 2, wherein the silver-gold core-shell nanowire has a diameter of 20 to 30nm and a length of about 20 μm.
4. The flexible enzyme-free glucose sensor electrode with the silver-gold core-shell nanowires is characterized by being prepared by the following steps:
(1) Washing the silver-gold core-shell nanowires of any one of claims 2 to 3 with ethanol and water several times, and then re-dispersing in water to obtain a silver-gold core-shell nanowire suspension;
(2) Filtering the silver-gold core-shell nanowire suspension obtained in the step (1) through a filter membrane to obtain a silver-gold core-shell nanowire network with the filter membrane as a substrate, and transferring the silver-gold core-shell nanowire network from the filter membrane to a pre-strained flexible substrate to obtain a flexible electrode; the flexible substrate is an elastomer film, and the prestrain of the flexible substrate is 50-300%;
(3) Carrying out capillary force welding treatment on the flexible electrode through mixed steam, so that a silver-gold core-shell nano network in the flexible electrode is subjected to induced welding, slowly releasing the prestrain on the flexible substrate to obtain the silver-gold core-shell nanowire flexible enzyme-free glucose sensor electrode, wherein the mixed steam is mixed with water and methanol, the volume ratio of the water to the methanol is 5-1, and the treatment time is 5-60 min.
5. The detection method of the enzyme-free glucose sensor electrode is characterized by comprising the following steps of:
step (1): taking the enzyme-free glucose sensor electrode of claim 4 as a working electrode, the saturated silver | silver chloride as a reference electrode, the platinum sheet as a counter electrode, and inserting the working electrode, the reference electrode and the counter electrode into a sodium hydroxide solution with a concentration of 0.05-0.5M;
step (2): continuously adding a glucose solution into the sodium hydroxide solution in the step (1) to form a mixed solution, and detecting the mixed solution by adopting a current-voltage cyclic voltammetry to carry out glucose electrocatalytic oxidation;
and (3): and (3) carrying out data processing on the electric signal detection result obtained by the detection in the step (2) and the glucose concentration to obtain the corresponding relation between the electric signal and the glucose concentration.
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