Graphene sensor and preparation method thereof

Abstract

The invention discloses a graphene sensor and a preparation method thereof.The microelectrode comprises a packaging shell and a sensor body, the front end and the rear end of the sensor body extend out of the packaging shell to form a first wiring terminal and a second wiring terminal, and a graphene conducting layer is arranged in the middle of the sensor body; the two ends of the graphene conducting layer are correspondingly and electrically connected with the first wiring terminal and the second wiring terminal respectively, the graphene conducting layer is located between the first insulating layer and the second insulating layer, a window area is arranged in the middle of the top of the second insulating layer, and the area, exposed by the window area, of the graphene conducting layer is subjected to oxygen plasma treatment to form a gas sensitive area. And a plurality of air holes are formed in the top or the side of the electrode packaging shell. The micro-electrode has the advantages that the nano-scale graphene conducting layer is successfully loaded between the two insulating layers, the graphene conducting layer is treated by oxygen plasma in the middle window area to form a gas sensitive area sensitive to formaldehyde, and the micro-electrode is small in size, controllable in cost, capable of measuring low-concentration formaldehyde and good in sensitivity and specificity.

Description

Technical Field

[0001] The present invention relates to the field of indoor toxic and harmful gas detection sensors, and in particular to a graphene sensor and a preparation method thereof. Background Art

[0002] Formaldehyde is a highly toxic substance, designated by the World Health Organization as a carcinogen and teratogen. It is a recognized allergen and a potential strong mutagen. Currently, indoor formaldehyde concentrations below 0.05 ppm are generally considered safe. However, long-term exposure to low doses of formaldehyde can be extremely harmful to susceptible individuals, potentially leading to chronic respiratory diseases, nasopharyngeal cancer, colon cancer, and other health problems.

[0003] In existing formaldehyde detection technologies, sensitive materials commonly used include bismuth ruthenate powder or nanoparticles of oxides, which are capable of adsorbing gas molecules in the air. Adsorption of formaldehyde and other gas molecules by these gas-sensitive materials significantly alters their electrical conductivity, enabling qualitative or quantitative detection of formaldehyde levels in the air. However, current formaldehyde detection devices suffer from various deficiencies: low sensitivity, making it difficult to effectively detect low concentrations of formaldehyde, particularly at concentrations below 0.1 ppm, resulting in significant measurement errors; complex or bulky devices, resulting in high costs and inconvenience; and poor specificity, making them susceptible to interference from gases such as ammonia, ethanol, and sulfur dioxide. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a graphene sensor and a preparation method thereof, aiming to overcome the deficiencies in the prior art to at least a certain extent.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a graphene sensor, which includes a packaging shell and a sensor body, the front and rear ends of the sensor body extend from the packaging shell to form a first terminal and a second terminal, the middle part of the sensor body is located in the packaging shell and is provided with a graphene conductive layer, the two ends of the graphene conductive layer are respectively electrically connected to the first terminal and the second terminal, a first insulating layer is provided at the bottom of the graphene conductive layer, a second insulating layer is provided above it, a window area is provided in the middle of the top of the second insulating layer, the left and right sides of the window area are flush with the left and right sides of the graphene conductive layer, the area of ​​the graphene conductive layer exposed by the window area is treated with oxygen plasma to form a gas-sensitive area, and a plurality of air holes are provided on the top or side of the electrode packaging shell.

[0006] On the basis of the above technical solutions, the present invention may further have the following specific options or more preferred options.

[0007] Furthermore, the first terminal and the second terminal are made of platinum.

[0008] Furthermore, the thickness of the graphene conductive layer is 5-30 nm.

[0009] Furthermore, the first insulating layer and the second insulating layer are any one of PI film, PET film or Parylene film.

[0010] Furthermore, the thickness of the first insulating layer and the second insulating layer are both 1-10 μm.

[0011] Furthermore, the electrode packaging shell is made of ceramic or hard insulating plastic.

[0012] Furthermore, there are multiple air holes, and the diameter of each air hole is 1-2 mm.

[0013] The present invention also provides a method for preparing the above-mentioned graphene sensor, which comprises the following steps:

[0014] S1. Using a long, thin platinum sheet as a substrate, after cleaning and drying, a graphene conductive layer is deposited on one side of the platinum sheet using PECVD or CVD.

[0015] S2. Depositing a first insulating layer and a second insulating layer on the exposed surface of the graphene conductive layer and the other surface of the platinum sheet respectively;

[0016] S3. Reactive ion etching or laser cutting is used to remove the central region of the second insulating layer to form a window region, and the platinum sheet exposed in the window region is dissolved using aqua regia to expose the underlying graphene conductive layer. After cleaning and drying, the graphene conductive layer exposed in the window region is treated with oxygen plasma to form a gas-sensitive region.

[0017] S4. Using reactive ion etching or laser cutting, the first insulating layer and the second insulating layer are removed from the regions at both ends of the platinum sheet to expose the platinum sheet to form a first terminal and a second terminal to obtain a sensor body;

[0018] S5. Use a packaging shell to package the sensor body.

[0019] On the basis of the above preparation method, the present invention can also have the following further specific options.

[0020] Specifically, in S2, the first insulating layer and the second insulating layer are obtained by physical vapor deposition using PI, PET or Parylene as raw materials.

[0021] Specifically, the process conditions of the plasma treatment in S3 are: oxygen flow rate 80-120 mL / min, power 240-300 W, two treatments at intervals, each treatment time 5-20 s, and an interval of 60-120 s between the two treatments.

[0022] On the basis of the above technical solution, the present invention can also be improved as follows.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention first deposits a graphene conductive layer on a platinum sheet, then deposits a first and a second insulating layer, then removes part of the second insulating layer and dissolves and cuts the platinum sheet in the middle to expose the graphene conductive layer. The exposed graphene material is treated with oxygen plasma to become a gas-sensitive material with nanometer-scale thickness that is specific for formaldehyde detection. Since the platinum sheet is dissolved and cut in the middle and the remaining platinum sheets at both ends are still effectively electrically connected to the graphene conductive layer, the nanometer-scale gas-sensitive material in the gas-sensitive area becomes a sensitive area of ​​electrode resistance. The adsorption of a small amount of formaldehyde can bring about a significant resistance change, and the formaldehyde concentration in the environment can be effectively measured as low as 0.005 ppm. Experiments have confirmed that the sensitivity and specificity of the material to formaldehyde are both good, and the material is not interfered with by gases such as ammonia, ethanol and sulfur dioxide.

[0025] The present invention successfully loads a nanoscale graphene conductive layer between the first and second insulating layers and electrically connects it to the first and second terminals at both ends. At the same time, the graphene conductive layer is treated with oxygen plasma in the middle window area to form a gas-sensitive area sensitive to formaldehyde. The resulting graphene sensor is small in size and easy to industrially mass-produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a graphene sensor provided by the present invention;

[0027] Figure 2 for Figure 1 Cross-sectional view of the graphene sensor along AA (enlarged);

[0028] Figure 3 for Figure 1 Cross-sectional view of the graphene sensor along BB (enlarged);

[0029] Figure 4 This is a process flow chart of the graphene sensor preparation method provided by the present invention.

[0030] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0031] 1. Package shell; 2. First terminal; 3. Second terminal; 4. Graphene conductive layer; 5. First insulating layer; 6. Second insulating layer; 7. Window area; 8. Gas-sensitive area; 9. Air vent; 10. Platinum sheet. DETAILED DESCRIPTION

[0032] The technical solutions provided by the present invention are described clearly and completely below with reference to the accompanying drawings and specific embodiments. It is obvious that the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the description of the present invention, if terms indicating directions such as "up", "down", "left", "right", "top", "bottom", "inside" and "outside" are used, the directions or positional relationships indicated are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0034] like Figures 1 to 3 As shown, the present invention provides a graphene sensor, which includes a packaging shell 1 and a sensor body, the front and rear ends of the sensor body extend from the packaging shell 1 to form a first terminal 2 and a second terminal 3, the middle part of the sensor body is located in the packaging shell 1 and is provided with a graphene conductive layer 4, the two ends of the graphene conductive layer 4 are respectively electrically connected to the first terminal 2 and the second terminal 3, a first insulating layer 5 is provided at the bottom of the graphene conductive layer 4, and a second insulating layer 6 is provided above it, a window area 7 is provided in the middle of the top of the second insulating layer 6, the left and right sides of the window area 7 are flush with the left and right sides of the graphene conductive layer 4, the area of ​​the graphene conductive layer 4 exposed by the window area 7 is treated with oxygen plasma to form a gas sensitive area 8, and a plurality of air holes 9 are provided on the top or side of the electrode packaging shell.

[0035] It should be noted that oxygen plasma treatment can oxidatively etch the surface of the graphene conductive layer in the window area, producing graphene oxide with a large specific surface area, rich in porosity, and surface structural defects. The graphene oxide and certain structural defects can enhance the specific adsorption of formaldehyde in the sensitive area. Furthermore, the sensitive area is a composite region of graphene and graphene oxide, and its conductivity is more sensitive to the effects of adsorbed formaldehyde, thereby ensuring the sensitivity and specificity of the graphene sensor to low-concentration formaldehyde. The graphene sensor provided by the present invention can be used to measure formaldehyde by connecting a sensitive device that measures resistance or resistivity changes at its two terminals.

[0036] In one embodiment of the present invention, the first terminal 2 and the second terminal 3 are made of platinum.

[0037] It is understandable that, in addition to platinum, gold, which has good conductivity and stability, can also be used as the material of the terminal, that is, the material used for the initial deposition to form the conductive graphene layer.

[0038] In one embodiment of the present invention, the thickness of the graphene conductive layer 4 is 5-30 nm.

[0039] It is understandable that the graphene conductive layer is a multilayer graphene with good electrical conductivity. The graphene located on the surface can be further treated with plasma to form graphene oxide, thereby forming a graphene / graphene oxide composite material.

[0040] In one embodiment of the present invention, the first insulating layer 5 and the second insulating layer 6 are any one of PI film, PET film or Parylene film. The thickness of the first insulating layer 5 and the second insulating layer 6 are both 1-10 μm.

[0041] It should be noted that PI film, PET film or Parylene film can be prepared by physical vapor deposition method, and the film thickness is easy to control.

[0042] In one embodiment of the present invention, the electrode packaging shell is made of ceramic or hard insulating plastic.

[0043] In one embodiment of the present invention, there are multiple air holes 9, and the diameter of each air hole 9 is 1-2 mm.

[0044] It should be noted that the vent holes can be provided on the top or side of the electrode packaging shell; the electrode packaging shell plays a role in protecting the graphene / graphene oxide composite material exposed in the window area.

[0045] The graphene sensor provided in the above embodiment is prepared by the following method: Figure 4 As shown, the following steps are included:

[0046] S1. A long thin platinum sheet 10 is used as a substrate. The platinum sheet is preferably a rectangular sheet with uniform thickness and a flat surface. The thickness is controlled to be 0.05-0.2 mm. After cleaning and drying, a graphene conductive layer 4 is deposited on one side of the platinum sheet 10 using PECVD or CVD.

[0047] S2. A first insulating layer 5 and a second insulating layer 6 are deposited on the exposed surface of the graphene conductive layer 4 and the other surface of the platinum sheet 10, respectively. Specifically, PI, PET or Parylene can be used as a raw material by physical vapor deposition;

[0048] S3. The middle region of the second insulating layer 6 is removed by reactive ion etching or laser cutting to form a window region 7. The platinum sheet 10 exposed in the window region 7 is dissolved using aqua regia to expose the underlying graphene conductive layer 4. After cleaning and drying, the graphene conductive layer 4 exposed in the window region 7 is treated with oxygen plasma to form a gas-sensitive region 8. The plasma treatment process conditions are: oxygen flow rate 80-120 mL / min, power 240-300 W, two treatments at intervals, each treatment time 5-20 s, and an interval of 60-120 s between the two treatments.

[0049] S4. Reactive ion etching or laser cutting is used to remove the first insulating layer 5 and the second insulating layer 6 at both ends of the platinum sheet 10 so that the platinum sheet 10 is exposed to form a first terminal 2 and a second terminal 3 to obtain a sensor body;

[0050] S5. Use the packaging shell 1 to package the sensor body.

[0051] The graphene sensor prepared by the present invention is used to detect formaldehyde in the environment. Actual measurements show that it can detect formaldehyde in the environment with a concentration as low as 0.005 ppm, with good sensitivity. At the same time, when there are common interfering gases such as ammonia, ethanol or sulfur dioxide in the environment, the graphene sensor can still perform formaldehyde detection well with good specificity.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A graphene sensor, characterized in that: The invention comprises a packaging shell (1) and a sensor body, wherein the front and rear ends of the sensor body extend from the packaging shell (1) to form a first terminal (2) and a second terminal (3), the middle part of the sensor body is located in the packaging shell (1) and is provided with a graphene conductive layer (4), the two ends of the graphene conductive layer (4) are respectively electrically connected to the first terminal (2) and the second terminal (3), the bottom of the graphene conductive layer (4) is provided with a first insulating layer (5), the top is provided with a second insulating layer (6), the top of the second insulating layer (6) is provided with a window area (7), the left and right sides of the window area (7) are flush with the left and right sides of the graphene conductive layer (4), the area of ​​the graphene conductive layer (4) exposed by the window area (7) is treated with oxygen plasma to form a gas sensitive area (8), and a plurality of air holes (9) are provided on the top or side of the electrode packaging shell.

2. A graphene sensor according to claim 1, characterized in that: The first connecting terminal (2) and the second connecting terminal (3) are made of metal platinum.

3. The graphene sensor according to claim 1, characterized in that: The thickness of the graphene conductive layer (4) is 5-30 nm.

4. The graphene sensor according to claim 1, characterized in that: The first insulating layer (5) and the second insulating layer (6) are any one of a PI film, a PET film or a Parylene film.

5. The graphene sensor according to claim 1, characterized in that: The thickness of the first insulating layer (5) and the second insulating layer (6) are both 1-10 μm.

6. The graphene sensor according to claim 1, characterized in that: The electrode packaging shell is made of ceramic or hard insulating plastic.

7. A graphene sensor according to any one of claims 1 to 6, characterized in that: There are a plurality of vent holes (9), and the diameter of each vent hole (9) is 1-2 mm.

8. A method for preparing the graphene sensor according to any one of claims 1 to 7, characterized in that: The steps include: S1. Using a long thin platinum sheet (10) as a substrate, after cleaning and drying, a graphene conductive layer (4) is deposited on one surface of the platinum sheet (10) using PECVD or CVD; S2. depositing a first insulating layer (5) and a second insulating layer (6) on the exposed surface of the graphene conductive layer (4) and the other side surface of the platinum sheet (10); S3. using reactive ion etching or laser cutting to remove the middle region of the second insulating layer (6) to form a window region (7), using aqua regia to dissolve the platinum sheet (10) exposed in the window region (7) to expose the underlying graphene conductive layer (4), and after cleaning and drying, using oxygen plasma to treat the graphene conductive layer (4) exposed in the window region (7) to form a gas-sensitive region (8); S4. using a reactive ion etching method or a laser cutting method to remove the first insulating layer (5) and the second insulating layer (6) at both ends of the platinum sheet (10) so as to expose the platinum sheet (10) to form a first terminal (2) and a second terminal (3), thereby obtaining a sensor body; S5. Use the packaging shell (1) to package the sensor body.

9. The method for preparing a graphene sensor according to claim 8, wherein: In S2, the first insulating layer (5) and the second insulating layer (6) are obtained by physical vapor deposition using PI, PET or Parylene as raw materials.

10. The method for preparing a graphene sensor according to claim 8, wherein: The process conditions of plasma treatment in S3 are: oxygen flow rate 80-120 mL / min, power 240-300 W, two treatments at intervals, each treatment time 5-20 s, and an interval of 60-120 s between the two treatments.

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