CN111537575A - Preparation method of self-heating laser-induced graphene flexible NO2 gas sensor - Google Patents

Abstract

The invention is a preparation method of a self-heating laser-induced graphene flexible NO2 gas sensor. The present invention includes an insulating area, an electrode area, a silver coating area and a gas sensing area, the insulating area is arranged at the bottom end, the electrode area and the gas sensing area are arranged on the upper surface of the insulating area, and the silver coating area The electrode connection areas arranged at both ends of the electrode area are three-dimensional porous graphene patterns with a larger porosity structure prepared by the high-energy one-step induction of laser light. Due to its unique three-dimensional structure size of graphene, the gas-sensing region can save the step of adding additional gas-sensing materials, and achieve the same or better gas adsorption. The method is conducive to the rapid desorption of NO2 gas molecules, improves the repeatability of the sensor, reduces the manufacturing cost, has a short manufacturing cycle, high sensitivity, and a detection limit of 10ppb, which has broad application prospects in environmental monitoring and medical diagnosis.

Description

Preparation method of self-heating laser-induced graphene flexible NO2 gas sensor

technical field

The invention relates to the field of sensors, in particular to a preparation method of a self-heating laser-induced graphene flexible NO2 gas sensor.

Background technique

Nitrogen dioxide (NO2) is a volatile and irritating toxic gas. According to the national standard "Occupational Exposure Limits for Hazardous Factors in the Workplace (GBZ2-2007)", the exposure limit of human NO2 is 5mg/m ³ (2.54PPM). Lung function can be impaired even for short periods of exposure to nitrogen dioxide; prolonged exposure to nitrogen dioxide increases the chance of respiratory infections and can lead to permanent organic lung disease. Human exhaled air condensate also contains NO2, and studies have found that the higher the NO2 concentration in exhaled air condensate, the higher the probability of acute bronchial asthma. Therefore, a NO2 gas sensor with high sensitivity, flexibility and low detection limit is urgently needed in the current environmental monitoring and medical diagnosis industries, and it is helpful to realize highly reliable real-time monitoring of NO2.

Graphene has excellent chemical and physical properties. Graphene with a three-dimensional porous structure has great advantages in gas sensors due to its high specific surface area, high electron mobility, and mechanical stability. Laser-induced graphene (LIG) uses the high energy of laser to destroy the structure of the original carbon source to form short-chain carbon or amorphous carbon, and then performs two-dimensional reconstruction on the surface of the substrate to form a three-dimensional porous graphene film. This technology can simultaneously realize the in-situ preparation and high-precision patterned assembly of three-dimensional graphene materials in one step, without the need for wet chemical steps, the fabrication process is simple, and the material morphology is controllable.

Most high-sensitivity gas sensors have small response and slow response/recovery process at room temperature, and need to increase the temperature to accelerate the adsorption and desorption process of gas molecules, so additional micro heaters need to be configured. The gas sensor designed by the invention can realize the self-heating function, greatly improve the sensitivity and recovery speed of the gas sensor, and realize fast gas sensing with low power consumption.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a self-heating laser-induced graphene flexible NO2 gas sensor and a preparation method. The method generates graphene as both an electrode area and a gas-sensing area by one-step laser induction, so as to improve the NO2 gas detection sensitivity; The barbell-shaped graphene structure is more beneficial to the sensor array, and the linewidth of the gas-sensing region obtained by the Ultraviolet Laser (UV) is thinner, which facilitates the self-heating effect.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of a self-heating laser-induced graphene flexible NO2 gas sensor, the method comprises the following steps:

(1) Cut the polyimide (PI) tape to a rectangular shape of the desired size (it is better to completely cover the surface of the glass slide in step (2));

(2) stick the PI tape obtained through step (1) to the glass slide surface by hydrosol;

(3) using the PI tape obtained in step (2) to induce a three-dimensional graphene pattern with a high-energy laser, the three-dimensional graphene pattern includes electrode connection regions at both ends and a single-line graphene region connecting the two-electrode connection regions, and the single-line graphene region It plays the role of connecting the connection areas of the two electrodes, forming a conductive path, and at the same time, it can be directly used as a gas sensing area; the width of the single-line graphene is 40-90 μm;

(4) the electrode connection area obtained through step (3) is completely coated on its upper surface with conductive silver ink to make a silver coating area;

(5) After the silver-coated assembly is separated from the glass slide, it is transferred to a flexible and stretchable substrate through a thermal release adhesive tape to make a flexible gas sensor.

The flexible and stretchable substrate is PDMS or the like, which is flexible, can be bent, stretched, and is attached along the surface of the object to be attached.

The laser is a UV laser with a wavelength of 355 nm, and the parameters of the high-energy laser are: laser power 1.0-1.5 W, defocusing distance 4.5-5.5 mm, and scanning speed 70-200 mm/s.

A self-heating laser-induced graphene flexible NO2 gas sensor, comprising an insulating area, an electrode area, a silver coating area and a gas sensing area, the insulating area is arranged at the bottom end, and the electrode area is arranged on the insulating area On the surface, the left and right ends of the electrode area are provided with two electrode connection areas formed by laser-induced graphene, and the two electrode connection areas are connected together by a single-line graphene formed by laser-induced graphene; the area where the single-line graphene is located is the gas sensor The surface of the electrode connection area is coated with a silver coating to form a silver coating area; the width of the single-line graphene is 40-100 μm, and the two electrode connection regions and the single-line graphene form a barbell-shaped structure.

Further, the insulating region is a flexible substrate PDMS with a high resistivity in a rectangular structure.

Further, the electrode connection area is a square, a rectangle, a circle, or any other irregular shape with an aspect ratio close to 0.5-1.5.

Further, the gas sensing area is a single-line structure, the length of the gas sensing area 4 is 1 cm-1.5 cm, and the width is generally 40 μm-80 μm.

Compared with the prior art, the sensor prepared based on the laser-induced graphene technology of the present invention has the following advantages:

1) The preparation method of the present invention does not require drop coating of gas-sensitive materials (high-sensitivity nanomaterials such as MoS2 and rGO/MoS2), directly uses laser-induced graphene, and prepares three-dimensional porous graphene by one-step laser-induced graphene technology. As the electrode material and the gas sensor material, the detection of NO2 gas can be realized and the complexity of the process is reduced, and the sensor prepared by the invention is convenient for the attachment of NO2 gas molecules due to the high specific surface area of the three-dimensional porous graphene. Due to its unique size structure, the gas sensing area locally increases the resistance of the gas sensing area. The self-heating function can be realized through the Joule heating effect, which is more conducive to the rapid desorption of NO2 gas molecules and improves the repeatability of the sensor. The gas sensor prepared by the invention can realize laser one-step preparation, the method is simple, the manufacturing period is short, the sensitivity is high, the detection limit can reach 10ppb, the self-heating function greatly improves the desorption speed of NO2 gas molecules, and accelerates the gas response/ Recovery speed.

2) The method of the present invention prepares a barbell-shaped three-dimensional porous graphene on a PI film in one step by a laser-induced graphene technology (Fig. 2), the nanomaterial has a controllable morphology, a simple method, a short manufacturing period, a low cost, and a better barbell-shaped structure. Useful for sensor arrays.

3) The sensor prepared by the present invention has a relatively wide detection range for NO2 (Fig. 6), which can meet the requirements of air quality monitoring and exhalation detection, and the minimum detection limit of the sensor can reach 10ppb (the exposure limit of human NO2 is 2.54ppm). ).

4) The sensor of the present invention is affected by the two factors of LIG specific surface area and self-heating temperature, and integrates the self-heating function (Fig. 3), which simplifies the device structure, reduces the energy consumption of the device, improves the gas response sensitivity, and improves the gas response. Response/recovery speed. The sensor uses a flexible substrate with low cost, and can be worn on the body or clothing of the human body for environmental detection.

5) The laser used in the preparation method of the present invention is an ultraviolet laser. Selecting an ultraviolet laser can obtain a gas sensitive area with a smaller width, so that the line width of the gas sensitive area is thinner, the size and shape of the LIG are more accurate, the formed LIG is more stable, and it is not easy to produce wrinkles , improve the resistance value of the gas sensing area, which is more conducive to the self-heating effect. The ultraviolet laser combined with the specific laser parameter setting and the size of the gas sensing area enables it to realize the simplified process conditions as possible, and broaden the accuracy range of gas detection. . The preparation method adopts the above laser parameter range, resulting in a larger porosity of the graphene microstructure and a good response to NO2 (Figure 5). Distortion, can not meet the requirements as a NO2 gas sensor (Figure 4).

6) In summary, the preparation method of the present invention can perform high-precision NO2 detection without adding gas-sensitive materials, simplifying the process, and in addition, compared with the preparation of existing sensors, it is easier, more convenient, and faster, and does not require the addition of other two-dimensional materials. High sensitivity and detection limit can be achieved, the process is simple, the production cost is low, and the lowest detection limit of ppb level can be achieved. It has a wide application prospect in the future sensor market, especially in environmental monitoring and medical diagnosis.

Description of drawings

Fig. 1 is the structural schematic diagram of the flexible NO2 gas sensor of the present invention;

2 is a schematic top view of the flexible NO2 gas sensor of the present invention;

Fig. 3 is the temperature space distribution of the self-heating temperature rise of the LIG electrode under different currents of the present invention. In Example 1, the gas-sensing responses were carried out at 20, 40, 60, and 80 degrees Celsius, respectively, and the gas-sensing response was the best at 40 degrees Celsius;

FIG. 4 is the response curve of the flexible gas sensor gas sensing area 4 prepared by using laser parameters outside the stated range to 0.8ppm NO2 at 40°C; the laser power is 1.0-1.5W, the defocusing distance is 4.5-5.5mm, The scanning speed is 500mm/s, and the signal-to-noise ratio is low.

Fig. 5 is the response curve of the flexible gas sensor gas sensing region 4 prepared by the present invention to 0.8ppm NO2 at 40°C;

FIG. 6 is the response curve of the flexible gas sensor gas sensing region 4 prepared by the present invention to different concentrations of NO2 at 40°C.

Description of reference numerals: 1. Insulation area; 2. Electrode area; 3. Silver coating area; 4. Gas sensing area.

Detailed ways

In order to describe in more detail a self-heating laser-induced graphene flexible NO2 gas sensor of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

As shown in Figure 1, a schematic structural diagram of a self-heating laser-induced graphene flexible NO2 gas sensor, including an insulating area 1, an electrode area 2, a silver coating area 3 and a gas sensing area 4, and the insulating area 1 is arranged on the At the bottom end, the electrode area 2 is arranged on the upper surface of the insulating area 1, and electrode connection areas are arranged at both ends of the electrode area 2, and the two electrode connection areas are connected by the gas sensing area 4, which is arranged on the upper surface of the electrode connection area. In the silver-coated area 3, the gas-sensing area 4 not only serves as a bridge between the two electrode connection areas but also serves as a gas-sensing area directly. The silver-coated area is only filled and coated on both ends of the electrode area The electrode connection area at both ends of the area 2 (the electrode connection area is the two squares referred to by 2 in FIG. 1) have a square structure with a length and a width of 0.5cm-1.5cm, and the gas-sensing area 4 has a length of 1cm-1.5cm, The width is 40μm-90μm. The insulating region 1 is a commercial flexible substrate PDMS with high resistivity, the electrode region 2 and the gas sensing region 4 are three-dimensional porous graphene patterns produced by high-energy laser-induced PI film, and the PI tape is a good carbon front. It has low cost and can produce graphene with three-dimensional structure under laser induction, which is conducive to the adhesion of NO2 gas molecules and can reduce contact resistance. The silver coating area 3 is prepared by coating with conductive silver ink. The laser Provided by a VU laser with a wavelength of 355nm.

Graphene is a P-type semiconductor. When the gas sensing area 4 is in an oxidizing gas NO2 environment, the conductivity of the P-type semiconductor will increase and the resistance will decrease. It is used for NO2 gas detection. When the NO2 gas sensor returns to the normal air environment Resistance recovery.

The preparation method of the above-mentioned self-heating laser-induced graphene flexible NO2 gas sensor, the method steps are as follows:

(1) The polyimide (Polyimide, PI) tape is cut into a rectangular shape of an appropriate size (it is better to completely cover the surface of the glass slide in step (2));

(2) Through hydrosols (such as common ones containing PVA (polyvinyl alcohol), PVP (polyvinyl pyrrolidone), CMC (sodium carboxymethyl cellulose), low modulus sodium silicate and cationic gum arabic, etc. PI tape obtained through step (1) is adhered to the surface of the glass slide;

(3) The PI tape obtained in step (2) is used to induce a three-dimensional graphene pattern with a high-energy laser, wherein the square graphene pattern at both ends is an electrode connection area, and the single-line graphene area is used as a bridge for the electrode connection area and as a gas. Sensitive area; the laser is a VU laser with a wavelength of 355nm, and the high-energy laser parameters are: laser power 1.0-1.5W, defocus distance 4.5-5.5mm, scanning speed 70-200mm/s; preferably scanning speed is 100-150mm/ s;

(4) the electrode connection area obtained through step (3) is completely coated on its upper surface with conductive silver ink to make a silver coating area;

(5) After the silver-coated assembly is released from the glass slide, it is transferred to the flexible substrate PDMS through a thermal release adhesive tape to make a flexible gas sensor.

Example 1

The self-heating laser-induced graphene flexible NO2 gas sensor in this embodiment includes an insulating area, an electrode area, a silver coating area, and a gas sensing area. The insulating area is arranged at the bottom end, and the electrode area is arranged at the insulating area. On the upper surface, the left and right ends of the electrode area are provided with two electrode connection areas formed by laser-induced graphene, and the upper surface of the electrode connection area is coated with a silver coating to form a silver coating area,

The two electrode connection regions are connected together by the single-line graphene formed by laser-induced graphene; the region where the single-line graphene is located is directly the gas sensing region; the width of the single-line graphene is 60 μm; the two electrode connection regions and the single-line graphene form a barbell shape structure. The electrode connection area is a square structure with a length and a width of 1 cm; the gas sensing area 4 has a length of 1.2 cm and a width of 60 μm.

When laser-induced graphene is used, the laser is a VU laser with a wavelength of 355 nm, and the high-energy laser parameters are: laser power 1.1 W, defocusing distance 4.5-5.5 mm, and scanning speed 140 mm/s.

The prepared flexible NO2 gas sensor is connected to an external measuring instrument, and the self-heating ability of the gas sensing layer is realized by giving different currents, and the gas sensing response test of 1ppm NO2 is carried out at 20 ℃ - 80 ℃, and it is found that the gas sensing The gas-sensing response of the zone is best at 40°C.

Example 2

The difference between the technical solution of this embodiment and Embodiment 1 is that the test gas concentration is different. This embodiment only describes the different parts, and the same parts will not be repeated. The test gas in this embodiment is NO2, the test temperature of the gas sensitive area is 40°C, and the test concentration is 0.2ppm, 0.4ppm, 0.6ppm, 0.8ppm, 1ppm, 2ppm, 5ppm, and it is found that the detection range of NO2 is relatively wide, and the resolution High rate and obvious response can meet the requirements of air quality monitoring and breath detection.

Comparative ratio

This comparative example is the same as Example 1, the difference is that the laser parameters are set as: laser power 1.0-1.5W, defocus distance 4.5-5.5mm, scanning speed 500mm/s, the obtained response to 0.8ppmNO2 at 40℃ The curve is shown in Figure 4, and the signal-to-noise ratio is low.

If the scanning speed is too fast, less graphene is generated, and the porosity of the graphene structure is too small to form a honeycomb hexagonal structure. If the scanning speed is too slow, the substrate will be easily burned out.

What is not described in the present invention applies to the prior art.

Claims (6)

1. a kind of self-heating laser-induced graphene flexible NO The preparation method of gas sensor, the method comprises the steps: (1) the polyimide PI tape is cut to the rectangular shape of the required size; (2) stick the PI tape obtained through step (1) to the glass slide surface by hydrosol; (3) using the PI tape obtained in step (2) to induce a three-dimensional graphene pattern with a high-energy laser, the three-dimensional graphene pattern includes electrode connection regions at both ends and a single-line graphene region connecting the two-electrode connection regions, and the single-line graphene region It plays the role of connecting the connection areas of the two electrodes, forming a conductive path, and at the same time, it can be directly used as a gas sensing area; the width of the single-line graphene is 40-90 μm; (4) the electrode connection area obtained through step (3) is completely coated on its upper surface with conductive silver ink to make a silver coating area; (5) After the silver-coated assembly is separated from the glass slide, it is transferred to a flexible and stretchable substrate through a thermal release adhesive tape to make a flexible gas sensor. 2 . The preparation method according to claim 1 , wherein the flexible and stretchable substrate is a material that can be bent, stretched, and can be attached along the surface of the object to be pasted, preferably a PDMS material. 3 . 3. The preparation method according to claim 1, wherein the laser is a UV laser with a wavelength of 355 nm, and the high-energy laser parameters are: laser power 1.0-1.5W, defocusing distance 4.5-5.5mm, scanning The speed is 70-200mm/s; the graphene microstructure with greater porosity can be obtained. 4. A self-heating laser-induced graphene flexible NO gas sensor, comprising an insulating area, an electrode area, a silver coating area and a gas-sensing area, the insulating area is arranged on the bottom end, and the electrode area is arranged on the insulating area. On the upper surface of the region, the left and right ends of the electrode region are provided with two electrode connection regions formed by laser-induced graphene, and the upper surface of the electrode connection region is coated with a silver coating to form a silver coating region, characterized in that: The two electrode connection regions are connected together by single-line graphene formed by laser-induced graphene; the region where the single-line graphene is located is directly the gas sensing region; the width of the single-line graphene is 40-100 μm; the two electrode connection regions and the single-line graphene are composed Barbell-shaped structure. 5 . The NO2 gas sensor according to claim 4 , wherein the electrode connection area is a square, a rectangle, a circle, or any other irregular shape with an aspect ratio of 0.5-1.5. 6 . 6 . The NO2 gas sensor according to claim 4 , wherein the gas sensing region has a single-wire structure, the length of the gas sensing region is 1 cm-1.5 cm, and the width is 40 μm-80 μm. 7 .

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