Preparation and Application of a Self-Supported Flexible Electrochemical Sensor Electrode Material

Abstract

The present invention discloses the preparation and application of a self-supporting flexible electrochemical sensor electrode material, belonging to the technical field of electrochemical sensor electrode materials. In the present invention, Co3O4 is in-situ grown on the surface of a self-made self-supporting flexible film of nitrogen and sulfur co-doped reduced graphene oxide-carbon nanotubes (NS-rGO-CNT) by a hydrothermal method to obtain the self-supporting flexible electrode material Co3O4 / NS-rGO-CNT. Quantitative analysis of hydrogen peroxide is carried out through a time-current curve. The results show that the present invention has the advantages of excellent anti-deformation ability, good selectivity, high sensitivity, and wide detection range of the sensor electrode material. The detection range of hydrogen peroxide is 50 nmol·L ‑1 ~10 mmol·L ‑1 , the detection limit is 16.7 nmol·L ‑1 , and the sensitivity is 10053.1 μA·mmol ‑1 ·cm ‑2 . It has good application prospects in the fields of clinical diagnosis, wearable devices, etc.

Description

Technical Field

[0001] The present invention belongs to the field of electrode materials for electrochemical sensors, and particularly relates to a self-supporting flexible electrode material for an electrochemical sensor and its application. Background Art

[0002] In recent years, with the development of medicine and the increasing attention of people to their own health conditions, flexible electrochemical sensors capable of real-time continuous monitoring of human life and health have attracted great attention from researchers due to their advantages such as light weight, good ductility, high adaptability, and arbitrary deformability to achieve skin fitting. However, most current flexible sensors rely on additional flexible substrates, and sensors are constructed on the flexible substrate through techniques such as laser engraving. On the one hand, their mechanical properties and flexibility are poor. On the other hand, during repeated folding or bending, the conductive material and the flexible substrate are prone to peeling or delamination, seriously reducing their stability and durability. Therefore, the development of flexible self-supporting electrochemical sensors has become one of the research hotspots today.

[0003] As is well known, the key to flexible self-supporting electrochemical sensors lies in highly active sensing materials and flexible self-supporting electrode materials with excellent performance. Among many active materials, transition metal compounds have attracted much attention due to their low cost, rich reserves, and low toxicity. In particular, transition metal oxides, such as Co 3 O 4 etc., with their rich variable valence states, exhibit good electrochemical catalytic activity towards hydrogen peroxide. However, few Co 3 O 4 are applied alone to flexible sensors, and currently there is no report on applying Co 3 O 4 to flexible sensing electrodes for hydrogen peroxide.

[0004] Due to its large specific surface area, fast electron transfer ability, high mechanical strength, good biocompatibility, and easy functionalization, etc., graphene oxide has played an excellent role in fields such as flexible sensors and has become an ideal candidate material for constructing self-supporting flexible sensors. However, graphene oxide has poor conductivity and is prone to interlayer stacking, which hinders its further application in the research of flexible electrochemical sensors. Partially reducing graphene oxide and introducing carbon nanotubes with excellent conductivity as an interlayer support can obtain reduced graphene with stable performance and higher conductivity. In addition, nitrogen and sulfur co-doping of graphene oxide can further effectively regulate the electrochemical properties of graphene oxide.

[0005] In summary, the present invention breaks through the bottleneck that traditional flexible electrodes require elastic substrates and conductive additives, and uses the hydrothermal method to make the active sensing material Co 3 O 4A self-supporting flexible electrochemical sensor electrode material, namely Co, was in-situ grown on the surface of a self-supporting flexible film NS-rGO-CNT. 3 O 4 / NS-rGO-CNT. This electrode material has excellent flexibility, shows excellent electrocatalytic activity towards hydrogen peroxide, and can be used for real-time in-situ detection of hydrogen peroxide released by living cells. SUMMARY OF THE INVENTION

[0006] Aiming at the deficiencies of the prior art, the present invention provides a preparation method and application of a self-supporting flexible electrochemical sensor electrode material, effectively solving the problems of poor stability and weak anti-mechanical deformation ability of traditional electrodes. The specific invention content is as follows:

[0007] The preparation of a self-supporting flexible electrochemical sensor electrode material, in which nano-spherical Co with a diameter of about 150 nm 3 O 4 was in-situ grown on the NS-rGO-CNT film to form a self-supporting flexible electrode material. The preparation method is as follows: A mixed solution of cetyltrimethylammonium bromide, glutamic acid and cobalt nitrate and the self-made self-supporting flexible composite film NS-rGO-CNT were placed in a reaction kettle for hydrothermal reaction. After the reaction, it was naturally cooled to room temperature, and the product was centrifuged, separated, washed and dried to obtain the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT. When preparing Co 3 O 4 / NS-rGO-CNT by the hydrothermal method, the mass-volume concentration ratio of cetyltrimethylammonium bromide, glutamic acid, and cobalt nitrate is 1:0.6:(1.2 - 3.6), the reaction time is 4 - 10 h, and the reaction temperature is 140 - 200 °C.

[0008] The application of a self-supporting flexible electrochemical sensor electrode material. Using an electrochemical workstation, with the obtained self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT as the working electrode, a platinum wire electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, adopting a three-electrode system. Under stirring, in a 0.2 M PBS solution (pH = 7.4), the working potential was controlled at -0.75 V. After the background current was stable, the current-time curve (i-t) after adding hydrogen peroxide at different concentrations was tested, and its detection range, detection limit, and sensitivity were obtained by calculation. This electrode material has a good response to hydrogen peroxide, with a detection limit as low as 16.7 nmol·L -1 , and a detection range as wide as 50 nmol·L -1 ~10 mmol·L -1, with a sensitivity as high as 10053.1 μA·mmol -1 ·cm -2 , and has strong anti-interference ability, good stability, reproducibility and repeatability, and excellent anti-deformation ability, and can be used for real-time detection of hydrogen peroxide released by living cells.

[0009] The preparation and application of a self-supporting flexible electrochemical sensor electrode material disclosed by the present invention have the following advantages compared with the prior art:

[0010] (1) By a one-step hydrothermal method, the present invention in-situ grows nano-spherical Co with a diameter of about 150 nm 3 O 4 on the NS-rGO-CNT film to form a novel self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT. This method is simple, controllable, low-cost, does not require binders and conductive agents, and has good repeatability.

[0011] (2) The electrode material prepared by the present invention can be directly used as a working electrode. Compared with traditional glassy carbon electrodes, gold electrodes, etc., it has excellent self-supporting property and flexibility, and can better realize the bending and folding of the electrode.

[0012] (3) The electrode material Co 3 O 4 / NS-rGO-CNT prepared by the present invention exhibits excellent electrocatalytic performance for hydrogen peroxide. On the one hand, Co 3 O 4 has a special morphology, presenting a nano-spherical shape with a porous surface, which makes the electrode material have a super-large surface area, providing sites for catalyzing hydrogen peroxide. On the other hand, there are various ions with different valence states in Co 3 O 4 , providing a large number of electrons for catalyzing hydrogen peroxide. Experiments show that when using this electrode material to detect hydrogen peroxide, the detection limit for hydrogen peroxide can reach 16.7 nmol·L -1 , the detection range can reach 50 nmol·L -1 ~10 mmol·L -1 , and the sensitivity can reach 10053.1 μA·mmol -1 ·cm -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the XRD pattern of the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT prepared in Example 1;

[0014] Figure 2 The SEM image of the self - supported flexible electrochemical sensor electrode material Co 3 O 4 / NS - rGO - CNT prepared in Example 2;

[0015] Figure 3 The current - time response curve of the self - supported flexible electrochemical sensor electrode material Co 3 O 4 / NS - rGO - CNT prepared in Example 3 to hydrogen peroxide;

[0016] Figure 4 The current - time response curves of the self - supported flexible electrochemical sensor electrode material Co 3 O 4 / NS - rGO - CNT prepared in Example 3 to hydrogen peroxide and interfering substances ascorbic acid (AA), dopamine (DA), glucose, and sodium chloride (NaCl);

[0017] Figure 5 The current response of the self - supported flexible electrochemical sensor electrode material Co 3 O 4 / NS - rGO - CNT to hydrogen peroxide before and after bending 100 times;

[0018] Figure 6 The current response of the self - supported flexible electrochemical sensor electrode material Co 3 O 4 / NS - rGO - CNT in 0.2 M PBS (pH = 7.4) solution containing 200 mg mL -1 AA with and without MCF - 7 cells; Detailed implementation manners

[0019] The following further elaborates on the present invention in conjunction with specific embodiments, but these embodiments do not limit the scope of the present invention in any way.

[0020] Example 1

[0021] (1) Place the self - made rGO - CNT self - supported flexible film and thiourea in a tube furnace. Under an argon atmosphere, heat it at a heating rate of 5 °C / min to 800 °C, then keep it warm for 40 min, and then naturally cool it to room temperature. Wash and dry to obtain the self - supported flexible composite film NS - rGO - CNT;

[0022] (2) Weigh 0.5 g of cetyltrimethylammonium bromide, 0.3 g of L-glutamic acid and 1.2 g of cobalt nitrate and dissolve them in 15 mL of ethanol. After complete dissolution, transfer it to a reaction kettle, and place the NS-rGO-CNT self-supporting flexible composite film obtained in step (1) in the above solution. Carry out hydrothermal reaction at 180 °C for 6 h, then wash and dry to obtain the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT. Its XRD pattern is shown in the appendix Figure 1 . The characteristic peaks at 2θ = 36.9°, 38.6°, 44.9° and 65.4° respectively correspond to the crystal planes of Co 3 O 4 (311), (222), (400) and (440) (JCPDF#74-1656), indicating that the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT has been successfully prepared.

[0023] Example 2

[0024] Weigh 0.5 g of cetyltrimethylammonium bromide, 0.3 g of L-glutamic acid and 1.8 g of cobalt nitrate and dissolve them in 15 mL of ethanol. After complete dissolution, transfer it to a reaction kettle, and place the self-made NS-rGO-CNT self-supporting flexible composite film in the above solution. Carry out hydrothermal reaction at 200 °C for 10 h, then wash and dry to obtain the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT. Its SEM image is shown in the appendix Figure 2 , Co 3 O 4 is spherical and evenly distributed on the surface of NS-rGO-CNT. The diameter of Co 3 O 4 nano-spheres is about 150 nm, and the surface is uneven.

[0025] Example 3

[0026] Electrochemical test.

[0027] (1) Using the self-supporting flexible electrode material Co 3 O 4 / NS-rGO-CNT obtained in Example 1 as the working electrode, saturated calomel electrode as the reference electrode, and platinum wire electrode as the counter electrode. Under stirring, in a 0.2 M PBS (pH = 7.4) solution, control the working potential to be -0.75 V. After the background current is stable, measure Co 3 O 4Current-time curves of CoO / NS-rGO-CNT in response to hydrogen peroxide at different concentrations. The results are shown in the appendix Figure 3 As can be seen from the appendix Figure 3 It can be seen that Co 3 O 4 / NS-rGO-CNT responds rapidly to hydrogen peroxide and reaches current equilibrium in a very short time after the addition of hydrogen peroxide. Co 3 O 4 / NS-rGO-CNT has a detection limit of 16.7 nmol·L -1 for hydrogen peroxide, a detection range of 50 nmol·L -1 to 10 mmol·L -1 , and a sensitivity of 10053.1 μA·mmol -1 ·cm -2 .

[0028] (2) Using the self-supporting flexible electrode material Co 3 O 4 / NS-rGO-CNT as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum wire electrode as the counter electrode, under stirring, in a 0.2 M PBS (pH = 7.4) solution, controlling the working potential to be -0.75 V, after the background current is stable, the current-time curves of Co 3 O 4 / NS-rGO-CNT in response to hydrogen peroxide and interfering substances ascorbic acid (AA), dopamine (DA), glucose, and sodium chloride (NaCl) are measured. The results are shown in the appendix Figure 4 As can be seen from the appendix Figure 4 It can be seen that Co 3 O 4 / NS-rGO-CNT has good selectivity for hydrogen peroxide.

[0029] (3) Using the self-supporting flexible electrode material Co 3 O 4 / NS-rGO-CNT before and after being bent 180° and continuously bent 100 times as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum wire electrode as the counter electrode, under stirring, in a 0.2 M PBS (pH = 7.4) solution, controlling the working potential to be -0.75 V, after the background current is stable, the current-time curves of Co 3 O 4 / NS-rGO-CNT in response to hydrogen peroxide are measured. The results are shown in the appendix Figure 5 As can be seen from the appendix Figure 5 It can be seen that after being bent 100 times, the current response of Co 3 O 4 / NS-rGO-CNT to hydrogen peroxide remains almost unchanged, indicating that Co3 O 4 / NS-rGO-CNT has good flexibility.

[0030] (4) Using the self-supporting flexible electrode material Co 3 O 4 / NS-rGO-CNT as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum wire electrode as the counter electrode, in a 0.2 M PBS (pH = 7.4) solution containing 4 × 10 6 MCF-7 cells, add the stimulant AA, control the working potential to -0.75 V, and after the background current is stable, measure the current-time curve of the response of Co 3 O 4 / NS-rGO-CNT to the hydrogen peroxide released by MCF-7 cells. At the same time, a comparative experiment was carried out under the same conditions. The results are shown in the appendix Figure 6 . From the appendix Figure 6 It can be seen that in a 0.2 M PBS (pH = 7.4) solution without MCF-7 cells, when AA is added, there is no change in the current response. In a 0.2 M PBS (pH = 7.4) solution containing MCF-7 cells, when AA is added, there is an obvious change in the current response, indicating that Co 3 O 4 / NS-rGO-CNT can be used to real-time monitor the hydrogen peroxide released by cancer cells.

Claims

1. Preparation of a self - supporting flexible electrochemical sensor electrode material, characterized in that, Nano-spherical Co with a diameter of about 150 nm 3 O 4 In-situ grown on the nitrogen and sulfur co-doped reduced graphene oxide-carbon nanotube (NS-rGO-CNT) film to form a self-supporting flexible electrode material. The preparation method is as follows: A mixed solution of cetyltrimethylammonium bromide, glutamic acid, and cobalt nitrate and the self-made self-supporting flexible composite film NS-rGO-CNT are placed in a reaction kettle for hydrothermal reaction. After the reaction is completed, it is naturally cooled to room temperature, and the product is centrifuged, separated, washed, and dried to obtain the self-supporting flexible electrochemical sensor electrode material Co 3 O 4 / NS-rGO-CNT; When preparing Co 3 O 4 / NS-rGO-CNT, the mass-volume concentration ratio of cetyltrimethylammonium bromide, glutamic acid, and cobalt nitrate is 1:0.6:(1.2 - 3.6), the reaction time is 4 - 10 h, and the reaction temperature is 140 - 200 °C.

2. Application of a self - supporting flexible electrochemical sensor electrode material, characterized in that, The electrode material has a good response to hydrogen peroxide, with a detection limit as low as 16.7 nmol·L -1 , and a detection range as wide as 50 nmol·L -1 ~10 mmol·L -1 , a sensitivity as high as 10053.1 μA·mmol -1 ·cm -2 , and has strong anti-interference ability, good stability, reproducibility and repeatability, and excellent anti-deformation ability, and can be used for the real-time detection of hydrogen peroxide released by living cells.

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