Ammonia gas-sensitive material based on In2O3 / Pd nanoparticle assembly structure, preparation method thereof and flexible sensor device

Abstract

The invention discloses an ammonia gas-sensitive material based on an In2O3 / Pd nanoparticle assembly structure, a preparation method thereof and a flexible sensor device. The In2O3 / Pd nanoparticle assembly material of the invention is prepared by cluster beam deposition technology, and a dual-target cluster sputtering source is used to deposit In2O3 nanoparticles and Pd nanoparticles on the surface of a flexible interdigital electrode with an insulating substrate in sequence; thus, In2O3 / Pd mixed nanoparticle assembly materials with different mass ratios can be obtained. The material can be used to achieve quantitative measurement of ammonia concentration. Compared with other prior arts, the In2O3 and Pd mixed nanoparticle assembly material of the invention can provide a high-performance ammonia sensing function, and due to the chemical modification of Pd nanoparticles on In2O3 and the synergistic catalytic effect, the mixed nanoparticle assembly material has more active sites than a single In2O3, and can achieve a high-sensitivity and fast-response sensing function for ammonia at a lower temperature.

Description

Technical Field

[0001] The present invention relates to the field of gas sensing, and in particular to an ammonia gas-sensitive material based on an In2O3 / Pd nanoparticle assembly structure, a preparation method thereof, and a flexible sensor device. Background Art

[0002] Ammonia is widely used in various fields of industrial production and agriculture, such as fertilizers and industrial refrigerants. x and SO x (x = 1, 2) and other pollutants react to produce tiny particles, forming the so-called PM10 and PM2.5, which penetrate deep into the lungs through breathing and cause respiratory diseases and heart attacks in humans. In addition, ammonia is also a natural metabolite of the human body. The detection of ammonia content in human exhaled breath is of great significance for the early diagnosis of diseases. Therefore, for the health and safety of human beings, it is of great significance to develop a stable, fast-response, low-detection-limit and flexible wearable ammonia sensor.

[0003] Metal oxide semiconductor gas sensors are the most widely used ammonia sensors at present. Due to their advantages such as high sensitivity, fast response speed, long life, simple preparation and low cost, they have developed into the most practical and widely used gas sensors. Indium oxide, as a stable wide-bandgap transition metal oxide semiconductor, has excellent gas-sensitive properties and is used in sensors, energy, catalysis and other fields. However, traditional indium oxide particles and films have poor response to ammonia alcohol and high operating temperature, usually above 300°C, which limits the application of indium oxide materials in the field of ammonia sensing.

[0004] The present invention proposes to prepare a mixed film of In2O3 nanoparticles and Pd nanoparticles by physical vapor deposition and deposit it on the interdigital electrodes to realize high-performance ammonia sensing technology. In this material, the In2O3 nanoparticles play the role of ammonia gas sensing, while the Pd nanoparticles play a synergistic catalytic role to reduce the reaction activation energy, thereby enhancing the gas-sensitive performance of the ammonia sensor, and reducing the optimal operating temperature of the device to 230 ° C, significantly reducing the power consumption of the device. In addition, the PI film of the prefabricated interdigital electrodes is selected as a flexible substrate, which realizes a flexible ammonia sensor compared to the traditional hard substrate. Summary of the invention

[0005] In view of the technical problems of high working temperature and poor response performance of the current indium oxide ammonia sensor, the present invention proposes an ammonia gas-sensitive material, preparation method and flexible sensor device based on In2O3 / Pd nanoparticle assembly structure. The present invention uses physical vapor deposition technology to prepare Pd / In2O3 nanoparticle assembly materials and realize ammonia sensing by cluster beam deposition technology. Compared with the wet chemical method, the material prepared by physical vapor deposition is simpler, and complex multi-component materials can be synthesized in one step to meet the needs of micro-electromechanical system (MEMS) processing. Compared with continuous film materials, the nanoparticle assembly film prepared by cluster beam deposition has a higher specific surface area and adsorbed oxygen content, which can increase the active sites in contact with ammonia. The Pd nanoparticles loaded on the surface of the material play a synergistic catalytic role, reduce the activation energy of the reaction, improve the selectivity and sensitivity of the material to ammonia, and reduce the working temperature. The invention can greatly enhance the perception of indium oxide to ammonia and reduce the optimal working temperature to 230 ℃. In addition, the advantage of the present invention is that the granular film is coupled with a flexible substrate to construct a flexible ammonia sensor, which can be applied to the field of wearable electronics.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The ammonia gas-sensitive material based on the In2O3 / Pd nanoparticle assembly structure is characterized in that the In2O3 / Pd nanoparticle assembly material is prepared by cluster beam deposition technology, using a dual-target cluster sputtering source to successively deposit In2O3 nanoparticles and Pd nanoparticles on the surface of a flexible interdigitated electrode with an insulating substrate to obtain In2O3 / Pd mixed nanoparticle assembly materials with different mass proportions.

[0008] Furthermore, in the In2O3 / Pd mixed nanoparticles, the mass proportion of Pd nanoparticles is 0.5%~10%.

[0009] The In2O3 nanoparticles and Pd nanoparticles are combined into a disordered and uniform mixed structure to form a Pd / In2O3 mixed nanoparticle assembly material.

[0010] The method for preparing an ammonia gas-sensitive material based on an In2O3 / Pd nanoparticle assembly structure comprises the following steps:

[0011] 1) High-purity In2O3 and Pd targets were installed on two sputtering guns of a multi-target magnetron cluster source in a cluster beam deposition device, and a flexible interdigital electrode with an insulating substrate (preferably, a 0.1 mm thick polyimide (PI) film was used as a flexible substrate) was placed in the deposition chamber of the cluster beam deposition system. The entire device was evacuated until the vacuum degree of the deposition chamber reached 5×10 -5 Pa or above;

[0012] 2) Sputtering gas is introduced into the sputtering gun, and buffer gas is introduced into the sputtering chamber of the cluster beam deposition system, and the gas pressure in the sputtering chamber is in the range of 1~300 Pa;

[0013] 3) A direct current voltage is applied to sputter In2O3 and Pd targets respectively, and In2O3 nanoparticles are first deposited on the surface of the flexible interdigital electrode with an insulating substrate, and then Pd nanoparticles are deposited. The ratio of the two nanoparticles is controlled by adjusting the sputtering time and power to obtain In2O3 / Pd mixed nanoparticle assembly materials with different mass ratios. The specific process is: the In2O3 target and the Pd target are partially vaporized into gaseous molecules or atoms, and then the buffer gas collides with them to form cluster nanoparticles, and a nanoparticle beam is formed by differential gas extraction, and then the beam is directed to the deposition chamber of the cluster beam deposition equipment, and deposited on the surface of the interdigital electrode, thereby obtaining the In2O3 / Pd nanoparticle assembly material.

[0014] Furthermore, the sputtering power of the In2O3 target was set to 7~10 W, the sputtering current was 0.028~0.033 A, the sputtering voltage was 250~300 V, and the sputtering time was 1000~1500 s.

[0015] Furthermore, the sputtering power of the Pd target was set to 10-15 W, the sputtering current was 0.035-0.042 A, and the sputtering voltage was 300-360 V.

[0016] An ammonia gas-sensitive flexible sensor device comprises the In2O3 / Pd mixed nanoparticle assembly material in which In2O3 nanoparticles and Pd nanoparticles are deposited on the surface of a flexible interdigital electrode with an insulating substrate, and is used for detecting the ammonia content in a gas.

[0017] When testing the ammonia content in the gas, take out the interdigital electrode and place it in the gas-sensitive test chamber. Use the Keithley digital source meter to connect the interdigital electrode to a voltage of 1 or 2V. After the ammonia is introduced, the ammonia reacts with the oxygen anions on the surface of the material, causing the material resistance to change, thereby causing the current displayed on the source meter to change. According to the formula:

[0018] Responsiveness .

[0019] in Ia is the current value displayed on the Keithley SourceMeter before ammonia is introduced. Ig It is the current value displayed on the Keithley SourceMeter after ammonia is introduced into the material. The response performance of the material to ammonia can be obtained by calculation.

[0020] The beneficial effects of the present invention are as follows: the present invention uses vapor deposition technology to deposit nanoparticles on a PI substrate with interdigitated electrodes to construct ammonia gas-sensitive materials and sensors. Compared with the traditional wet chemical method, the prepared material is purer and compatible with the existing MEMS process. Since the nanoparticle assembly material formed by sputtering has a higher specific surface area than a thin film, it can greatly increase the contact opportunity with ammonia and create more reaction sites. Moreover, since the Pd nanoparticles loaded on the surface play a catalytic synergistic role, the selectivity and sensitivity to ammonia are enhanced, and the operating temperature is also greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the ammonia sensor made of In2O3 / Pd nanoparticle assembly material prepared by the present invention.

[0022] 1-interdigitated electrode layer, 2-In2O3 nanoparticles, 3-Pd nanoparticles, 4-PI flexible substrate.

[0023] Figure 2a It is the response curve of the nanoparticle assembly material prepared by the present invention to different ammonia concentrations at 230°C.

[0024] Figure 2b It is the relationship between the responsiveness and the ammonia concentration when the nanoparticle assembly material prepared by the present invention is tested for different ammonia concentrations at 230°C. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0026] Embodiment 1:

[0027] The preparation of an ammonia gas-sensitive In2O3 / Pd nanoparticle assembly material and a sensor device thereof comprises the following steps:

[0028] (1) Preparation of In2O3 / Pd nanoparticle assembly materials: High-purity In2O3 target and high-purity Pd target were placed on two sputtering guns of the cluster beam deposition equipment respectively. The electrode sheet (including the Ag interdigitated electrode layer 1 and the PI flexible substrate 4) was placed in the sputtering chamber of the cluster beam deposition system. The entire device was evacuated to a vacuum of 5×10 -5 Pa or above.

[0029] High-purity argon gas with a purity of more than 99.99% is used as sputtering and buffer gas.

[0030] 70 sccm of sputtering gas was introduced into the sputtering gun equipped with In2O3 target, and 60 sccm of buffer gas was introduced into the sputtering chamber. At this time, the pressure in the sputtering chamber was 122 Pa. Then, 7 W of power was introduced into the sputtering gun equipped with In2O3 target. At this time, the sputtering current was 0.028 A and the sputtering voltage was 250 V. In2O3 nanoparticles were deposited on the electrode sheet. The sputtering time was 1200 s. The sputtering gas and power were turned off.

[0031] Then, 70 sccm of sputtering gas was introduced into the sputtering gun equipped with the Pd target. At this time, the pressure in the sputtering chamber was 122 Pa. Then, 14 W of power was introduced into it. At this time, the sputtering current was 0.042 A, the sputtering voltage was 333 V, and the deposition time was 150 s, 250 s, and 450 s, respectively. Pd nanoparticles were deposited on the electrode sheet, and finally Pd / In2O3 nanoparticle assembly materials were obtained, which were placed in air for aging for 24 h. The mass proportions of Pd nanoparticles were 0.30%, 0.51%, and 1.50%, respectively. Figure 1 In2O3 nanoparticles 2 and Pd nanoparticles 3 are deposited on the surface of a flexible interdigitated electrode with an insulating substrate.

[0032] (2) The gas sensing performance of the In2O3 / Pd nanoparticle assembly material obtained above was tested:

[0033] The interdigital electrodes deposited with In2O3 / Pd nanoparticle assembly materials were placed in the test chamber, and the temperature in the test chamber was heated to 150 ℃, 170 ℃, 200 ℃, 230 ℃, 250 ℃, and 270 ℃ in sequence using a ceramic heating rod. The two ends of the electrode were connected to a Keithley digital source meter, and a stable voltage of 1 V was applied to the two ends of the interdigital electrodes using the source meter, and the current at the two ends of the assembly material was read through the source meter.

[0034] The ammonia flow rate and air flow rate were controlled by a mass flow meter. Ammonia of different concentrations was introduced into the test chamber. The current values ​​before and after ventilation were recorded. The formula was used:

[0035] Responsiveness .

[0036] in I a is the current value displayed on the source meter before ammonia is passed. I g is the current value displayed on the source meter after ammonia is passed. The quantitative response of In2O3 / Pd nanoparticle assembly material to ammonia is obtained. The response performance is best when the Pd deposition amount is 0.51% and the working temperature is 230 ℃. The measured results are shown in Figure 2a and Figure 2bAs can be seen from the figure, the detection range is 0~1000 ppm and the response time is T 90 <70 s, responsiveness is 0%~400%.

[0037] The best response temperature of In2O3 microspheres prepared by traditional chemical methods to ammonia is as high as 550°C, and the response time is T 90 >500s, the maximum response is 1000% when the ammonia concentration is 100 ppm. For example, the literature: Lei D, Liu Y, Wei M, et al. Ammonia sensing characteristics of La 10 Si5MgO 26 -based sensors using In2O3sensing electrode with different morphologies and CuO reference electrode[J].Sensors and Actuators B: Chemical, 2016, 228:716-724

[0038] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. An ammonia gas-sensitive material based on an In2O3 / Pd nanoparticle assembly structure, characterized in that The In2O3 / Pd nanoparticle assembly material is prepared by cluster beam deposition technology, using a dual-target cluster sputtering source to deposit In2O3 nanoparticles and Pd nanoparticles on the surface of a flexible interdigitated electrode with an insulating substrate, thereby obtaining an In2O3 / Pd mixed nanoparticle assembly material with different mass ratios; In the In2O3 / Pd mixed nanoparticles, the mass proportion of Pd nanoparticles is 0.5% to 10%; In2O3 nanoparticles and Pd nanoparticles are combined into a disordered and uniform mixed structure to form a Pd / In2O3 mixed nanoparticle assembly material.

2. The method for preparing an ammonia gas-sensitive material based on an In2O3 / Pd nanoparticle assembly structure as claimed in claim 1, characterized in that The following steps are involved: 1) High-purity In2O3 and Pd targets were installed on two sputtering guns of a multi-target magnetron cluster source in a cluster beam deposition device, and a flexible interdigital electrode with an insulating substrate was placed in the deposition chamber of the cluster beam deposition system. The entire device was evacuated until the vacuum degree of the deposition chamber reached 5×10 -5 Pa or above; 2) Sputtering gas is introduced into the sputtering gun, and buffer gas is introduced into the sputtering chamber of the cluster beam deposition system, and the gas pressure in the sputtering chamber is in the range of 1~300 Pa; 3) In2O3 and Pd targets were sputtered successively, and In2O3 nanoparticles were first deposited on the surface of the flexible interdigital electrode with an insulating substrate, and then Pd nanoparticles were deposited. The ratio of the two nanoparticles was controlled by adjusting the sputtering time and power to obtain In2O3 / Pd mixed nanoparticle assembly materials with different mass ratios; The sputtering power of the In2O3 target was set to 7-10 W, the sputtering current was 0.028-0.033 A, the sputtering voltage was 250-300 V, and the sputtering time was 1000-1500 s. The sputtering power of the Pd target was set to 10~15 W, the sputtering current was 0.035~0.042 A, and the sputtering voltage was 300~360 V.

3. An ammonia gas-sensitive flexible sensor device, characterized in that The In2O3 / Pd mixed nanoparticle assembly material comprises In2O3 nanoparticles and Pd nanoparticles deposited on the surface of a flexible interdigital electrode with an insulating substrate as described in claim 1, and is used to detect the ammonia content in a gas.

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