GaN / PPY / graphene ammonia gas sensor and preparation method thereof
The ammonia sensor with a GaN/PPY/graphene composite structure solves the problems of insufficient sensitivity and stability of traditional sensors, and achieves high-performance room-temperature NH3 detection, which is suitable for industrial and health monitoring.
Patent Information
- Application Number
- CN202510722112.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-09-12
AI Technical Summary
Existing ammonia sensors have shortcomings in high sensitivity and long-term stability, especially traditional semiconductor metal oxide sensors have high energy consumption and poor selectivity, GaN has low sensitivity to NH3, and the long-term stability and sensitivity of single PPY materials are insufficient.
A GaN/PPY/graphene composite structure was adopted. PPY and graphene were electrically uniformly grown on the GaN epitaxial wafer by in-situ oxidative polymerization to form a surface np heterostructure. The Schottky barrier between GaN and graphene was used to promote electron mobility to prepare a GaN/PPY/graphene ammonia sensor.
It achieves high-performance NH3 detection at ppb level at room temperature, with fast response and recovery speed, good long-term stability, and low cost, making it suitable for industrial safety and human health monitoring.
Smart Images
Figure CN120629291A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of gas sensors, and specifically relates to a GaN / PPY / graphene ammonia sensor and a preparation method thereof. Background Art
[0002] Ammonia (NH3) is a colorless, toxic gas with a strong, pungent odor. It primarily originates from industrial waste, agricultural fertilizer use, and animal metabolism. It is widely used in industries such as fertilizer production and refrigerants, but exposure to high concentrations can cause damage to the skin, eyes, and respiratory system. However, it is one of the most harmful environmental pollutants generated by common industrial manufacturing processes. The explosive limits of ammonia are typically 16-25%. According to US standards, NH3 concentrations exceeding certain limits pose health risks, such as 25 ppm for exposure for no more than eight hours. Furthermore, as a natural metabolic product in the human body, measuring NH3 levels in exhaled breath is crucial for early diagnosis of diseases, particularly in monitoring liver and kidney diseases. NH3 can cause severe damage to the skin, respiratory system, nervous system, and other organs. Furthermore, as a natural metabolic byproduct of the human body, NH3 levels in exhaled breath can serve as a diagnostic indicator for liver and kidney diseases.
[0003] To effectively monitor and reduce the risk of NH3 exposure, the development of high-performance ammonia sensors is crucial. While widely used, traditional semiconductor metal oxide sensors are limited in their practical feasibility by high operating temperatures, high energy consumption, and poor selectivity. In recent years, gallium nitride (GaN) semiconductor materials, due to their excellent physical and chemical properties, have been investigated for use in gas sensors, particularly for the detection of NO2 and H2. However, their low sensitivity to NH3 requires further improvement. In contrast, semiconductor organic polymers such as polypyrrole (PPY) have become a research hotspot for the next generation of ammonia sensors due to their excellent chemical stability, low cost, and ease of synthesis and doping. They exhibit good selectivity and sensitivity for NH3 at room temperature. However, single PPY materials suffer from insufficient long-term stability and sensitivity, necessitating further improvements in their performance.
[0004] In summary, the development of highly stable, sensitive, and low-cost room-temperature ammonia sensors is of great significance for ensuring industrial safety, agricultural production, and human health monitoring. Future research should focus on exploring new materials, improving sensor structures, and increasing cost-effectiveness to address the growing environmental and health challenges. Summary of the Invention
[0005] The present invention overcomes the shortcomings of the existing technology and proposes a GaN / PPY / graphene ammonia sensor and its preparation method. By compounding GaN material with PPY and graphene, the synergistic effect between different materials is fully utilized to improve the sensitivity to NH3, which is used to achieve high-performance detection of NH3 at the ppb level at room temperature.
[0006] The present invention is achieved through the following technical solutions: A GaN / PPY / graphene ammonia sensor includes a GaN epitaxial wafer, on which graphene and P-type PPY are electrically and uniformly grown by in-situ oxidative polymerization, and Ti / Au electrodes are deposited on both sides of the surface of the GaN epitaxial wafer.
[0007] Preferably, the GaN epitaxial wafer is doped with any one of the elements silicon, magnesium, aluminum or indium during its growth process.
[0008] More preferably, the concentration of silicon doped in the GaN layer of the GaN epitaxial wafer is 1×10 18 cm -3 ~10×10 18 cm -3 ; The concentration of doped magnesium is 1×10 18 cm -3 ~5×10 18 cm -3 ; The doped aluminum or indium is 1 to 30 wt% of the mass of the Ga element, calculated as the element.
[0009] The method for preparing a GaN / PPY / graphene ammonia sensor comprises the following steps: S1. Immerse the GaN epitaxial wafer in an acidic solution of pyrrole, add a graphene dispersion, and dropwise add an ammonium persulfate solution. Use an in-situ oxidative polymerization method to composite a PPY film on the surface of the GaN epitaxial wafer to generate a GaN / PPY / graphene composite sensitive material. S2. Deposit Ti / Au electrodes at both ends of the GaN / PPY / graphene composite sensitive material.
[0010] Preferably, the method for preparing the GaN epitaxial wafer is to grow a GaN layer on a substrate by chemical vapor deposition; the GaN layer is doped with any one of the elements silicon, magnesium, aluminum or indium.
[0011] More preferably, the substrate is any one of sapphire, silicon or silicon carbide.
[0012] Preferably, the Ti / Au electrodes are deposited using magnetron sputtering or evaporation technology.
[0013] More preferably, the thickness of the deposited Ti / Au electrode is 50-100 nm.
[0014] Preferably, the acidic solution of pyrrole is a HCl solution of pyrrole.
[0015] Preferably, after step S2, the GaN / PPY / graphene composite sensitive material is washed and dried to obtain a GaN / PPY / graphene ammonia sensor.
[0016] In the preparation method of the present invention, the concentration of the ammonium persulfate solution used for in-situ oxidative polymerization to form the PPY film is preferably 0.01 to 0.05 mol / L.
[0017] More specifically, after the ammonium persulfate solution is added dropwise, the reaction solution is preferably stirred for 2 to 4 hours to form a composite PPY thin film on the surface of the GaN epitaxial wafer.
[0018] The present invention preferably cleans the prepared GaN / PPY / graphene composite sensitive material with a 0.5-2 mol / L dilute HCl solution and then dries it at 60° C. to obtain a GaN / PPY / graphene ammonia sensor.
[0019] The GaN / PPY / graphene ammonia sensor prepared by the present invention can be used as an NH3 gas concentration detection sensor and applied to NH3 concentration detection in various occasions.
[0020] The CGS-MT intelligent gas-sensitive analysis system was used to detect the gas-sensitive properties of the GaN / PPY / graphene ammonia sensor prepared in the present invention.
[0021] The beneficial effects of the present invention compared to the prior art are: Compared with traditional NH3 detection methods, the GaN / PPY / graphene ammonia sensor prepared in the present invention has many advantages such as high stability, fast response and recovery speed, and room temperature detection. In addition, the sensor is simple to prepare and low in cost.
[0022] The present invention prepares a GaN / PPY / graphene ammonia sensor by polymerizing a PPY sensitive film by in-situ oxidation polymerization of a GaN epitaxial wafer to electrically uniformly grow p-type PPY on a GaN substrate, and polymerizing the film with graphene in a solution. GaN and PPY form a surface np heterostructure, generating a Schottky barrier between GaN and graphene, promoting electron mobility, greatly improving the detection sensitivity of NH3, and having a fast response and recovery speed. It can achieve ppb-level lower limit detection of NH3 at room temperature and has good long-term stability.
[0023] The GaN / PPY / graphene ammonia sensor of the present invention can not only realize the rapid and stable monitoring of NH3 in many chemical sites, but also has important significance for the monitoring and prevention of early liver and kidney diseases in the human body. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is an SEM image of the GaN / PPY / graphene composite gas-sensitive material prepared in Example 1.
[0025] Figure 2 This is a response recovery curve of the GaN / PPY / graphene ammonia sensor prepared in Example 1 to NH3.
[0026] Figure 3 This is a response recovery curve of the GaN / PPY / graphene-2 ammonia sensor prepared in Example 2 to NH3.
[0027] Figure 4 This is a response recovery curve of the GaN / PPY / graphene-3 ammonia sensor prepared in Example 3 to NH3.
[0028] Figure 5 This is a response recovery curve of the pure PPY ammonia sensor prepared in comparative example 1 to NH3.
[0029] Figure 6 This is a response recovery curve of the pure GaN ammonia sensor prepared in comparative example 2 to NH3. DETAILED DESCRIPTION
[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The technical solutions of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings, but the scope of protection is not limited thereto. Example
[0031] This embodiment provides a GaN / PPY / graphene ammonia sensor and a preparation method thereof, which specifically includes the following steps: S1: The doped silicon prepared by MOCVD has a concentration of 5×10 18 cm -3 The GaN epitaxial wafers are cut into 3×5 mm sizes.
[0032] The GaN epitaxial wafer is obtained by epitaxially growing a GaN layer using a sapphire substrate by conventional MOCVD. During the growth of the GaN epitaxial wafer, elemental silicon is doped into the GaN layer.
[0033] S2: Add 0.5705 g of ammonium persulfate powder to 50 mL of deionized water and stir to obtain a 0.05 mol / L ammonium persulfate solution. 3 mg of graphene powder was added to 5 ml of deionized water and ultrasonicated for 30 min to obtain a graphene dispersion. Take 8.3 mL of concentrated HCl and dilute it to 100 mL with deionized water to obtain a 1 mol / L HCl solution; take 15 mL of the HCl solution and add it dropwise to 15 mL of deionized water to dilute it to obtain a 0.5 mol / L dilute HCl solution.
[0034] S3: In an ice bath, place the GaN epitaxial wafer and 0.05 mL of pyrrole in a beaker, add 20 mL of 0.5 mol / L dilute HCl solution to form a protonic acid environment, and stir magnetically for 30 min; add the graphene dispersion, and then add 20 mL of 0.01 mol / L ammonium persulfate solution dropwise, and stir magnetically for 4 h to prepare the GaN / PPY / graphene composite sensitive material (see Figure 1 ).
[0035] S4: Take out the GaN / PPY / graphene composite sensitive material, wash it with 1 mol / L dilute HCl solution, and dry it on a 60°C heating table.
[0036] S5: Using magnetron sputtering or evaporation technology, Ti / Au electrodes with a thickness of 100 nm are first deposited on both ends of the above-mentioned GaN epitaxial wafer through a mask to obtain a GaN / PPY / graphene ammonia sensor.
[0037] The gas sensing performance of the GaN / PPY / graphene ammonia sensor prepared in this example to NH3 was tested using a CGS-MT intelligent gas sensing analysis system at (25±2)°C and a relative humidity of 30%.
[0038] The size of the sensor response indicates the strength of its NH3 detection capability.
[0039] Response formula: Response (%) = (Rg - Ra) / Ra × 100%. Ra represents the baseline resistance of the sensor in air before NH3 injection, and Rg represents the real-time resistance of the sensor after NH3 injection.
[0040] The response of the GaN / PPY / graphene ammonia sensor prepared in Example 1 to different concentrations of NH3 is shown in Figure 1. Figure 2As shown, it can be seen that the GaN / PPY / graphene ammonia sensor has a fast response recovery speed to NH3, with a detection limit of 100 ppb. The sensor's response to 1000 ppm of NH3 can reach 130%. The inset shows the response of the GaN / PPY / graphene ammonia sensor to NH3 concentrations of 5 ppm, 2 ppm, 1 ppm, 500 ppb, 200 ppb and 100 ppb. Example
[0041] This embodiment provides a GaN / PPY / graphene ammonia sensor and a preparation method thereof, which specifically includes the following steps: S1: The magnesium doping concentration of 5×10 18 cm -3 The GaN epitaxial wafers are cut into 3×5 mm sizes.
[0042] The GaN epitaxial wafer is obtained by epitaxially growing a GaN layer using a sapphire substrate by conventional MOCVD. During the growth of the GaN epitaxial wafer, the GaN layer is doped with elemental magnesium.
[0043] S2: Add 0.5705 g of ammonium persulfate powder to 50 mL of deionized water and stir to obtain a 0.05 mol / L ammonium persulfate solution. 3 mg of graphene powder was added to 5 ml of deionized water and ultrasonicated for 30 min to obtain a graphene dispersion. Take 8.3 mL of concentrated HCl and dilute it to 100 mL with deionized water to obtain a 1 mol / L HCl solution; take 15 mL of the HCl solution and add it dropwise to 15 mL of deionized water to dilute it to obtain a 0.5 mol / L dilute HCl solution.
[0044] S3: In an ice bath, place the GaN epitaxial wafer and 0.1 mL of pyrrole in a beaker, add 20 mL of a 0.5 mol / L dilute HCl solution to form a protonic acid environment, and magnetically stir for 30 min. Add the graphene dispersion, and then add 20 mL of a 0.01 mol / L ammonium persulfate solution dropwise. Magnetic stirring is performed for 4 h to prepare a GaN / PPY / graphene composite sensitive material.
[0045] S4: Take out the GaN / PPY / graphene composite sensitive material, wash it with 1 mol / L HCl solution, and dry it on a heating platform at 60°C.
[0046] S5: Using magnetron sputtering or evaporation technology, Ti / Au electrodes with a thickness of 100 nm are first deposited on both ends of the above-mentioned GaN epitaxial wafer through a mask to obtain a GaN / PPY / graphene-2 ammonia sensor.
[0047] The gas sensing performance of the GaN / PPY / graphene-2 ammonia sensor prepared in this example to NH3 was tested using a CGS-MT intelligent gas sensing analysis system at (25±2)°C and a relative humidity of 30%.
[0048] The size of the sensor response indicates the strength of its NH3 detection capability.
[0049] Response formula: Response (%) = (Rg - Ra) / Ra × 100%. Ra represents the baseline resistance of the sensor in air before NH3 injection, and Rg represents the real-time resistance of the sensor after NH3 injection.
[0050] The response of GaN / PPY / graphene-2 ammonia sensor to different concentrations of NH3 is shown in the figure. Figure 3 As shown in the figure, it can be seen that the sensor has a fast response recovery speed to NH3, the detection limit is 200 ppb, and the response of the sensor to 1000 ppm NH3 can reach 66%. Example
[0051] This embodiment provides a GaN / PPY / graphene ammonia sensor and a preparation method thereof, which specifically includes the following steps: S1: The doped silicon prepared by MOCVD has a concentration of 5×10 18 cm -3 The GaN epitaxial wafers are cut into 3×5 mm sizes.
[0052] The GaN epitaxial wafer is obtained by epitaxially growing a GaN layer using a sapphire substrate by conventional MOCVD. During the growth of the GaN epitaxial wafer, elemental silicon is doped into the GaN layer.
[0053] S2: Add 0.5705 g of ammonium persulfate powder to 50 mL of deionized water and stir to obtain a 0.05 mol / L ammonium persulfate solution. 3 mg of graphene powder was added to 5 ml of deionized water and ultrasonicated for 30 min to obtain a graphene dispersion. Take 8.3 mL of concentrated HCl and dilute it to 100 mL with deionized water to obtain a 1 mol / L HCl solution. Take 15 mL of the above solution and add it dropwise to 15 mL of deionized water to dilute it to obtain a 0.5 mol / L dilute HCl solution.
[0054] S3: In an ice bath, place the epitaxial wafer and 0.02 mL of pyrrole in a beaker, add 20 mL of 0.5 mol / L dilute HCl solution to form a protonic acid environment, and magnetically stir for 30 min. Add the graphene dispersion, and then add 20 mL of 0.01 mol / L ammonium persulfate solution dropwise. Magnetically stir for 4 h to prepare the GaN / PPY / graphene composite sensitive material.
[0055] S4: Take out the GaN / PPY / graphene composite sensitive material, wash it with 1 mol / L dilute HCl solution, and dry it on a heating table at 60°C.
[0056] S5: Using magnetron sputtering or evaporation technology, Ti / Au electrodes with a thickness of 100 nm are first deposited on both ends of the above-mentioned GaN epitaxial wafer through a mask to obtain a GaN / PPY / graphene-3 ammonia sensor.
[0057] The gas sensing performance of the GaN / PPY / graphene-3 ammonia sensor prepared in this example to NH3 was tested using a CGS-MT intelligent gas sensing analysis system at (25±2)°C and a relative humidity of 30%.
[0058] The size of the sensor response indicates the strength of its NH3 detection capability.
[0059] Response formula: Response (%) = (Rg - Ra) / Ra × 100%. Ra represents the baseline resistance of the sensor in air before NH3 injection, and Rg represents the real-time resistance of the sensor after NH3 injection.
[0060] The response of GaN / PPY / graphene-3 ammonia sensor to different concentrations of NH3 is shown in the figure. Figure 4 As shown, it can be seen that the sensor has a fast response recovery speed to NH3, the detection limit is 500 ppb, and the sensor's response to 1000 ppm NH3 can reach 51%. Comparative Example 1 S1: Add 0.5705 g of ammonium persulfate powder to 50 mL of deionized water and stir to obtain a 0.05 mol / L ammonium persulfate solution. Take 8.3 mL of concentrated HCl and dilute it to 100 mL with deionized water to obtain a dilute HCl solution with a concentration of 1 mol / L. Take 15 mL of the above solution and add it dropwise to 15 mL of deionized water to dilute it to obtain a dilute HCl solution with a concentration of 0.5 mol / L.
[0061] S2: In an ice bath, place 0.05 ml of pyrrole in a beaker, add 20 ml of 0.5 mol / L dilute HCl solution to form a protonic acid environment, and stir magnetically for 30 min; then add 20 ml of 0.01 mol / L ammonium persulfate solution dropwise and stir magnetically for 4 h to prepare a ppy solution.
[0062] S4: The obtained ppy solution is centrifuged and dried in a vacuum drying oven at 60° C. The obtained powder is coated on a silver interpolation electrode to obtain a ppy ammonia sensor.
[0063] The gas sensing performance of the GaN-Au / PANI ammonia sensor prepared in this example to NH 3 was tested using a CGS-MT intelligent gas sensing analysis system at (25±2)°C and a relative humidity of 30%.
[0064] The size of the sensor response indicates the strength of its NH3 detection capability.
[0065] Response formula: Response (%) = (Rg - Ra) / Ra × 100%. Ra represents the baseline resistance of the sensor in air before NH3 injection, and Rg represents the real-time resistance of the sensor after NH3 injection.
[0066] The response of the ppy ammonia sensor to different concentrations of NH3 changes as shown in the following figure: Figure 5 As shown, it can be seen that the sensor has a low response and a slow response recovery speed to NH3. The detection limit is 10 ppm, and the sensor's response to 100 ppm NH3 is only 13%.
[0067] Comparative Example 2 S1: The doped silicon prepared by MOCVD has a concentration of 5×10 18 cm -3 The GaN epitaxial wafers are cut into 3×5 mm sizes.
[0068] The GaN epitaxial wafer is obtained by epitaxially growing a GaN layer using a sapphire substrate by conventional MOCVD. During the growth of the GaN epitaxial wafer, elemental silicon is doped into the GaN layer.
[0069] S2: Using magnetron sputtering or evaporation technology, Ti / Au electrodes with a thickness of 100 nm are first deposited on both ends of the above-mentioned GaN epitaxial wafer through a mask to obtain a GaN ammonia sensor.
[0070] The gas sensing performance of the GaN-Au / PANI ammonia sensor prepared in this example to NH 3 was tested using a CGS-MT intelligent gas sensing analysis system at (25±2)°C and a relative humidity of 30%.
[0071] The size of the sensor response indicates the strength of its NH3 detection capability.
[0072] Response formula: Response (%) = (Rg - Ra) / Ra × 100%. Ra represents the baseline resistance of the sensor in air before NH3 injection, and Rg represents the real-time resistance of the sensor after NH3 injection.
[0073] The response of GaN ammonia sensor to different concentrations of NH3 changes as shown in the figure. Figure 6 As shown, it can be seen that the sensor has a low response and a slow response recovery speed to NH3, the detection limit is 20 ppm, and the sensor's response to 100 ppm NH3 is only 6%.
[0074] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be considered that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the present invention, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.
Claims
1. A GaN / PPY / graphene ammonia sensor, characterized in that: The invention comprises a GaN epitaxial wafer, on which graphene and P-type PPY are electrically and uniformly grown through in-situ oxidation polymerization, and Ti / Au electrodes are deposited on both sides of the surface of the GaN epitaxial wafer.
2. The GaN / PPY / graphene ammonia sensor according to claim 1, characterized in that: During the growth process of the GaN epitaxial wafer, any one of silicon, magnesium, aluminum or indium is doped.
3. The GaN / PPY / graphene ammonia sensor according to claim 2, characterized in that: The concentration of silicon doped in the GaN layer of the GaN epitaxial wafer is 1×10 18 cm -3 ~10×10 18 cm -3 ; The concentration of doped magnesium is 1×10 18 cm -3 ~5×10 18 cm -3 ; The doped aluminum or indium is 1 to 30 wt% of the mass of the Ga element, calculated as the element.
4. The method for preparing a GaN / PPY / graphene ammonia sensor according to claims 1-3, characterized in that: The following steps are involved: S1. Immerse the GaN epitaxial wafer in an acidic solution of pyrrole, add a graphene dispersion, and dropwise add an ammonium persulfate solution. Use an in-situ oxidative polymerization method to composite a PPY film on the surface of the GaN epitaxial wafer to generate a GaN / PPY / graphene composite sensitive material. S2. Deposit Ti / Au electrodes at both ends of the GaN / PPY / graphene composite sensitive material.
5. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 4, wherein: The method for preparing the GaN epitaxial wafer is to grow a GaN layer on a substrate by chemical vapor deposition.
6. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 5, characterized in that: The substrate is any one of sapphire, silicon or silicon carbide.
7. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 4, characterized in that: Ti / Au electrodes were deposited using magnetron sputtering or evaporation techniques.
8. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 7, characterized in that: The thickness of the deposited Ti / Au electrode is 50-100 nm.
9. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 4, characterized in that: The acidic solution of pyrrole is a solution of pyrrole in HCl.
10. The method for preparing a GaN / PPY / graphene ammonia sensor according to claim 4, characterized in that: After step S2, the GaN / PPY / graphene composite sensitive material is washed and dried to obtain a GaN / PPY / graphene ammonia sensor.