阅读说明：本技术 可自加热的激光诱导石墨烯柔性no2气体传感器的制备方法 (Self-heatable laser-induced graphene flexible NO2Preparation method of gas sensor ) 是由 杨丽 郑广浩 姬华东 王宏丽 于 2020-08-14 设计创作，主要内容包括：本发明为可自加热的激光诱导石墨烯柔性NO2气体传感器的制备方法。本发明包括绝缘区域、电极区域、银涂层区域与气敏区域,所述绝缘区域设置于底端,所述电极区域与所述气敏区域设置于绝缘区域上表面,所述银涂层区域设置于电极区域两端的电极连接区域,所述电极区域与气敏区域为通过激光的高能量一步诱导制备的具有更大孔隙率结构的三维多孔石墨烯图案。气敏区域由于其独特石墨烯三维结构尺寸,可省去额外添加气敏材料的步骤,达到同样甚至更好效果的气体吸附。该方法利于NO2气体分子快速脱附,提高传感器使用重复性,降低制造成本,制造周期短,灵敏度高,检测限可以达到10ppb,在环境监测和医疗诊断方面有广阔的应用前景。(The invention relates to a preparation method of a self-heating laser-induced graphene flexible NO2 gas sensor. The graphene electrode comprises an insulation area, an electrode area, a silver coating area and a gas-sensitive area, wherein the insulation area is arranged at the bottom end, the electrode area and the gas-sensitive area are arranged on the upper surface of the insulation area, the silver coating area is arranged in electrode connection areas at two ends of the electrode area, and the electrode area and the gas-sensitive area are three-dimensional porous graphene patterns with larger porosity structures and prepared through high-energy one-step induction of laser. Due to the unique three-dimensional structure size of graphene, the gas-sensitive area can save the step of additionally adding gas-sensitive materials, and gas adsorption with the same or even better effect is achieved. The method is beneficial to quick desorption of NO2 gas molecules, improves the use repeatability of the sensor, reduces the manufacturing cost, has short manufacturing period and high sensitivity, has the detection limit of 10ppb, and has wide application prospect in the aspects of environmental monitoring and medical diagnosis.)

1. A preparation method of a self-heatable laser-induced graphene flexible NO2 gas sensor comprises the following steps:

(1) cutting the polyimide PI adhesive tape into a rectangular shape with a required size;

(2) adhering the PI adhesive tape obtained in the step (1) to the surface of the glass slide through hydrosol;

(3) inducing a three-dimensional graphene pattern by using high-energy laser on the PI adhesive tape obtained in the step (2), wherein the three-dimensional graphene pattern comprises electrode connection areas at two ends and a single-line graphene area for connecting the two electrode connection areas, and the single-line graphene area plays a role in connecting the two electrode connection areas to form a conductive path and can be directly used as a gas-sensitive area; the width of the single-line graphene is 40-90 mu m;

(4) completely coating the upper surface of the electrode connecting area obtained in the step (3) with conductive silver ink to prepare a silver coating area;

(5) and (3) separating the assembly coated with the silver coating from the glass slide, and transferring the assembly to a flexible stretchable substrate through a heat release adhesive tape to manufacture the flexible gas sensor.

2. The method for preparing the flexible stretchable substrate according to claim 1, wherein the flexible stretchable substrate is a material capable of bending, stretching and conforming along the surface of an object to be pasted, and is preferably a PDMS material.

3. The method for preparing a composite material according to claim 1, wherein the laser is a UV laser with a wavelength of 355nm, and the high-energy laser parameters are as follows: the laser power is 1.0-1.5W, the defocusing distance is 4.5-5.5mm, and the scanning speed is 70-200 mm/s; a graphene microstructure with greater porosity can be obtained.

4. A self-heatable laser-induced graphene flexible NO2 gas sensor comprises an insulation area, an electrode area, a silver coating area and a gas-sensitive area, wherein the insulation area is arranged at the bottom end, the electrode area is arranged on the upper surface of the insulation area, two electrode connection areas formed by laser-induced graphene are arranged at the left end and the right end of the electrode area, and a silver coating is coated on the upper surface of the electrode connection areas to form the silver coating area, and the self-heatable laser-induced graphene flexible NO2 gas sensor is characterized in that:

the two electrode connection areas are connected together through single-line graphene formed by laser-induced graphene; the area where the single-line graphene is located is directly a gas-sensitive area; the width of the single-line graphene is 40-100 mu m; two electrode connection regions and single line graphite alkene constitute barbell type structure.

5. The NO2 gas sensor according to claim 4, wherein the electrode connection area is square, rectangular, circular, or any other irregular shape with an aspect ratio of 0.5-1.5.

6. The NO2 gas sensor according to claim 4, wherein the gas sensing region is a single line structure, and has a length of 1cm to 1.5cm and a width of 40 μm to 80 μm.

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

Nitrogen dioxide (NO2) is a volatile, irritating, toxic gas. According to the regulation of national standard 'workplace harmful factor occupational contact limit (GBZ 2-2007)', the contact limit of human NO2 is 5mg/m³(2.54 PPM). Lung function is impaired even when the human body is exposed to nitrogen dioxide for a short period of time; if exposed to nitrogen dioxide for a prolonged period of time, the chance of respiratory tract infections increases and may lead to permanent organic lesions in the lungs. Human exhaled breath condensate also contains NO2, and it has been found through studies that the higher the concentration of NO2 in exhaled breath condensate, the higher the chance of acute episodes of bronchial asthma. Therefore, an NO2 gas sensor with high sensitivity, flexibility and low detection limit is urgently needed by the current environmental monitoring and medical diagnosis industry, and is helpful for realizing high-reliability real-time monitoring of NO 2.

Graphene has excellent chemical and physical properties, and the graphene with a three-dimensional porous structure plays a great advantage in the aspect of gas sensors due to high specific surface area, high electron mobility and mechanical stability. Laser Induced Graphene (LIG) is a three-dimensional porous Graphene film formed by utilizing the high energy of laser to destroy the structure of an original carbon source to form short chain carbon or amorphous carbon and then performing two-dimensional reconstruction on the surface of a substrate.

Most high-sensitivity gas sensors have small response when working at room temperature, slow response/recovery process, and need to be heated to accelerate the adsorption and desorption process of gas molecules, so that an additional micro-heater needs to be configured. The gas sensor designed by the invention can realize a self-heating function, greatly improves the sensitivity and recovery speed of the gas sensor, and realizes low-power-consumption and rapid gas sensing.

Disclosure of Invention

The invention aims to provide a self-heating laser-induced graphene flexible NO2 gas sensor and a preparation method thereof, wherein the method generates graphene through laser one-step induction, and the graphene is used as an electrode area and a gas-sensitive area, so that the detection sensitivity of NO2 gas is improved; the barbell type graphene structure is more beneficial to a sensor array, and the line width of a gas-sensitive area obtained by Ultraviolet (UV) Laser is thinner, so that the self-heating effect is facilitated.

In order to achieve the purpose, the invention adopts the following technical scheme:

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

(1) cutting a Polyimide (PI) adhesive tape to a rectangular shape with a required size (preferably to completely cover the surface of the glass slide in the step (2));

(2) adhering the PI adhesive tape obtained in the step (1) to the surface of the glass slide through hydrosol;

(3) inducing a three-dimensional graphene pattern by using high-energy laser on the PI adhesive tape obtained in the step (2), wherein the three-dimensional graphene pattern comprises electrode connection areas at two ends and a single-line graphene area for connecting the two electrode connection areas, and the single-line graphene area plays a role in connecting the two electrode connection areas to form a conductive path and can be directly used as a gas-sensitive area; the width of the single-line graphene is 40-90 mu m;

(4) completely coating the upper surface of the electrode connecting area obtained in the step (3) with conductive silver ink to prepare a silver coating area;

(5) and (3) separating the assembly coated with the silver coating from the glass slide, and transferring the assembly to a flexible stretchable substrate through a heat release adhesive tape to manufacture the flexible gas sensor.

The flexible stretchable substrate is flexible such as PDMS, can be bent and stretched, and is attached along the surface of an object to be adhered.

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

A self-heating laser-induced graphene flexible NO2 gas sensor comprises an insulation area, an electrode area, a silver coating area and a gas-sensitive area, wherein the insulation area is arranged at the bottom end, the electrode area is arranged on the upper surface of the insulation area, two electrode connection areas formed by laser-induced graphene are arranged at the left end and the right end of the electrode area, and the two electrode connection areas are connected together through single-line graphene formed by the laser-induced graphene; the area where the single-line graphene is located is a gas sensitive area, and a silver coating is coated on the upper surface of the electrode connection area to form a silver coating area; the width of the single-wire graphene is 40-100 mu m, and the two electrode connection areas and the single-wire graphene form a barbell-shaped structure.

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

Further, the electrode connection area is square, rectangular, circular, or any other irregular shape having an aspect ratio of approximately 0.5 to 1.5.

Furthermore, the gas-sensitive area is of a single-line structure, the length of the gas-sensitive 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 has the following advantages:

1) according to the preparation method, gas-sensitive materials (high-sensitivity nano materials such as MoS2 and rGO/MoS 2) do not need to be dripped, laser-induced graphene is directly used, three-dimensional porous graphene is prepared by a one-step method through a laser-induced graphene technology, the prepared graphene is used as an electrode material and a gas-sensitive material, detection of NO2 gas can be achieved, process complexity is reduced, and the sensor prepared by the method is convenient for attachment of NO2 gas molecules due to the high specific surface area of the three-dimensional porous graphene. The gas-sensitive area has locally increased resistance due to the unique size structure, can realize self-heating function through the joule heat effect, is more beneficial to quick desorption of NO2 gas molecules, and improves the use repeatability of the sensor. The gas sensor prepared by the invention can realize one-step laser preparation, has the advantages of simple method, short manufacturing period, high sensitivity and detection limit of 10ppb, greatly improves the desorption speed of NO2 gas molecules due to the self-heating function, and accelerates the response/recovery speed of the gas.

2) According to the method, the barbell type three-dimensional porous graphene (shown in figure 2) is prepared on the PI film in one step through the laser-induced graphene technology, the shape of the nano material is controllable, the method is simple, the manufacturing period is short, the cost is low, and the barbell type structure is more beneficial to a sensor array.

3) The sensor prepared by the invention has a relatively wide detection range of NO2 (figure 6), can meet the requirements of air quality monitoring and expiration detection, and has a minimum detection limit of 10ppb (the contact limit of human NO2 is 2.54 ppm).

4) The sensor is influenced by two factors of the LIG specific surface area and the self-heating temperature, integrates the self-heating function (figure 3), simplifies the structure of the device, reduces the working energy consumption of the device, improves the gas response sensitivity and promotes the gas response/recovery speed. The sensor uses a flexible substrate, is low in cost, and can be worn on the body of a human body or on clothes for environment detection.

5) The laser used in the preparation method is the ultraviolet laser, the ultraviolet laser can be selected to obtain the gas-sensitive area with smaller width, the line width of the gas-sensitive area is thinner, the size and the shape of the LIG are more accurate, the formed LIG is more stable, the wrinkles are not easy to generate, the resistance value of the gas-sensitive area is improved, the self-heating effect is more facilitated, and the ultraviolet laser is combined with the specific laser parameter setting and the size of the gas-sensitive area, so that the gas detection precision range can be widened under the process condition which is simplified as much as possible. According to the preparation method, the porosity of the microstructure of the graphene is larger by adopting the laser parameter range, the graphene has good response to NO2 (figure 5), and when the laser parameter outside the range is adopted to respond to NO2, the signal-to-noise ratio is generally low, the graphene is volatile and cannot meet the requirement of being used as a NO2 gas sensor (figure 4).

6) In conclusion, the preparation method can carry out high-precision NO2 detection without adding gas-sensitive materials, simplifies the process, is easier, more convenient and faster to prepare compared with the existing sensor, can reach higher sensitivity and detection limit without adding other two-dimensional materials, has simple process and low manufacturing cost, can realize the lowest detection limit of ppb level, and has wide application prospect in the future sensor market, especially in the aspects of environmental monitoring and medical diagnosis.

Drawings

Fig. 1 is a schematic structural view of a flexible NO2 gas sensor according to the invention;

fig. 2 is a schematic top view of a flexible NO2 gas sensor according to the invention;

fig. 3 is a temperature spatial distribution of the self-heating temperature rise of the LIG electrode under different currents, in example 1, gas-sensitive responses are respectively performed at 20, 40, 60, and 80 degrees centigrade, and the gas-sensitive response is optimal at 40 degrees centigrade;

FIG. 4 is a graph of the response of the gas sensing region 4 of a flexible gas sensor made according to the present invention using laser parameters outside the ranges described to 0.8ppmNO2 at 40 ℃; 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 a graph showing the response of the gas sensing region 4 of a flexible gas sensor prepared according to the present invention to 0.8ppm NO2 at 40 ℃;

fig. 6 is a response curve of the gas sensing area 4 of the flexible gas sensor prepared by the invention at 40 ℃ to different concentrations of NO 2.

Description of reference numerals: 1. an insulating region; 2. an electrode region; 3. a silver coating region; 4. a gas sensitive region.

Detailed Description

In order to describe the self-heatable laser-induced graphene flexible NO2 gas sensor in more detail, the invention is described in detail with reference to the accompanying drawings and examples.

As shown in fig. 1, a structural schematic diagram of a self-heatable laser-induced graphene flexible NO2 gas sensor includes an insulating region 1, an electrode region 2, a silver coating region 3 and a gas sensing region 4, where the insulating region 1 is disposed at a bottom end, the electrode region 2 is disposed on an upper surface of the insulating region 1, electrode connection regions are disposed at two ends of the electrode region 2, the two electrode connection regions are connected by the gas sensing region 4, and the silver coating region 3 is disposed on an upper surface of the electrode connection region, where the gas sensing region 4 serves as a bridge for the two electrode connection regions and also serves as a gas sensing region directly, the silver coating region is only filled on upper surfaces at two ends of the electrode region 2, and the electrode connection regions at two ends of the electrode region 2 (the electrode connection regions are two squares indicated by 2 in fig. 1) have a square structure with a length and a width of 0.5cm to 1.5cm, the length of the gas-sensitive area 4 is 1 cm-1.5 cm, and the width is 40 μm-90 μm. The insulation region 1 is commercial flexible substrate PDMS with high resistivity, the electrode region 2 and the gas sensitive region 4 are three-dimensional porous graphene patterns generated by inducing a PI film through high-energy laser, the PI tape is a good carbon precursor and is low in cost, graphene with a three-dimensional structure can be generated under the induction of the laser, the attachment of NO2 gas molecules is facilitated, and the contact resistance can be reduced, the silver coating region 3 is prepared by coating conductive silver ink, and the laser is provided by a VU laser with the wavelength of 355 nm.

The graphene is a P-type semiconductor, when the gas sensitive region 4 is in an oxidizing gas NO2 environment, the conductivity of the P-type semiconductor is increased, the resistance is reduced, the graphene is used for detecting NO2 gas, and when the NO2 gas sensor returns to a normal air environment, the resistance is recovered.

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

(1) cutting a Polyimide (PI) tape into a rectangular shape with a proper size (preferably, the surface of the glass slide in the step (2) is completely covered);

(2) adhering the PI adhesive tape obtained in the step (1) to the surface of the glass slide through hydrosol (such as common hydrosol containing PVA (polyvinyl alcohol), PVP (polyvinylpyrrolidone), CMC (sodium carboxymethylcellulose), low-modulus sodium silicate, cation Arabic gum and the like, which can be dissolved in water again and lose the adhesive property quickly);

(3) inducing a three-dimensional graphene pattern by using high-energy laser on the PI adhesive tape obtained in the step (2), wherein square graphene patterns at two ends are electrode connection areas, and a single-line graphene area is used as a bridge of the electrode connection areas and a gas-sensitive area; the laser is a VU laser with the wavelength of 355nm, and the parameters of the high-energy laser are as follows: the laser power is 1.0-1.5W, the defocusing distance is 4.5-5.5mm, and the scanning speed is 70-200 mm/s; the scanning speed is preferably 100-150 mm/s;

(4) completely coating the upper surface of the electrode connecting area obtained in the step (3) with conductive silver ink to prepare a silver coating area;

(5) and (3) separating the assembly coated with the silver coating from the glass slide, and transferring the assembly onto a flexible substrate PDMS through a heat release adhesive tape to prepare the flexible gas sensor.