An ethanol gas-sensitive material based on a Pd / MoOx nanoparticle assembly structure, a preparation method thereof, and a sensor device

Abstract

The present invention discloses an ethanol gas-sensing material based on a Pd / MoOx nanoparticle assembly structure, a preparation method thereof, and a sensor device. The Pd / MoOx nano-assembly material of the present invention is prepared by using a cluster beam deposition technique. By using a dual-target cluster sputtering source, Mo nanoparticles and Pd nanoparticles are successively deposited on the surface of interdigital electrodes with an insulating substrate, and Pd / MoO with different mass ratios can be obtained after aging in air. x Hybrid nanoparticle assembly materials; quantitative measurement of ethanol concentration can be achieved by using this material. Compared with other existing technologies, the molybdenum oxide and palladium hybrid nanoparticle assembly material involved in the present invention has more adsorbed oxygen content properties, and due to the chemical modification and synergistic catalytic effect of Pd nanoparticles on ethanol, the hybrid nano-assembly material has x more active sites and can achieve high sensitivity and rapid response perception of ethanol at a lower temperature.

Description

Technical Field

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

[0002] Ethanol is an explosive volatile organic compound (VOCs) with application scenarios in the food industry, biomedicine, chemical engineering, and other fields. However, as a flammable and explosive volatile substance, the flammable range of ethanol in the air is 3.3% - 19%. In addition, long-term exposure to ethanol vapor can cause headaches, difficulty breathing, and damage to the central nervous system. Based on factors such as safety and health, it is very important to quickly, stably, and low-costly monitor the concentration of ethanol gas in real time.

[0003] Metal-oxide-semiconductor (MOS) has the characteristics of high stability, fast response to target gases, low cost, rich raw materials, and simple preparation process, and has become a commonly used gas sensor device at present. As a stable wide-bandgap transition metal oxide semiconductor, molybdenum oxide has excellent chemical properties and is applied in the fields of sensors, energy, catalysis, etc. Traditional molybdenum oxide thin films and bulk materials have poor response to ethanol, and the working temperature is usually above 250°C, which limits the application of molybdenum oxide materials in the field of ethanol sensing.

[0004] Using a cluster beam deposition device to prepare nanoparticle assembly materials by physical vapor deposition is a conventional existing technology (for example, see the literature: Sun L, Chen M, Peng X, et al. The effects of Ni contents on hydrogen sensing response of closely spaced Pd–Ni alloy nanoparticle films[J]. International Journal of Hydrogen Energy, 2016, 41(2): 1341-1347.). The present invention

[0005] proposes a method of depositing Pd nanoparticles on the surface of Mo nanoparticles and aging them to form Pd / MoO x nanoparticle assembly materials to achieve ethanol gas sensing technology. In this material, MoO x nanoparticles play the role of ethanol gas sensitivity, and Pd nanoparticles play a role in synergistic catalysis to reduce the activation energy and enhance the ethanol gas sensitivity performance, and the optimal working temperature of the sensor is reduced to 180°C. Summary of the Invention

[0006] Aiming at the technical problems of high operating temperature and poor response performance of current traditional molybdenum oxide ethanol sensors, the purpose of the present invention is to provide an ethanol gas-sensitive material based on a Pd / MoOx nanoparticle assembly structure, a preparation method thereof, and a sensor device. The present invention utilizes physical vapor deposition technology to prepare Pd / MoO x nanoparticle assembly materials through cluster beam deposition technology and realizes ethanol sensing. This invention can greatly improve the sensing ability of molybdenum oxide to ethanol and reduce the operating temperature to 180°C.

[0007] The advantages of the present invention are that, compared with traditional wet chemistry, the materials prepared by physical vapor deposition are simpler, can synthesize complex multi-component materials in one step, and meet the needs of micro-nano processing. The nanoparticles prepared by cluster beam deposition have higher specific surface area and adsorbed oxygen content properties compared with thin film materials, and can increase the active sites in contact with ethanol. The Pd nanoparticles loaded on the surface of the material play a synergistic catalytic role, reducing the reaction activation energy, improving the selectivity and sensitivity of the material to ethanol, and reducing the operating temperature.

[0008] The present invention is realized through the following scheme:

[0009] The ethanol gas-sensitive material based on a Pd / MoO x nanoparticle assembly structure, characterized by including interdigital electrodes with an insulating substrate and Mo nanoparticles and Pd nanoparticles successively deposited on the surface of the interdigital electrodes. After aging, a disordered and uniform mixed structure of molybdenum oxide MoO x nanoparticles and Pd nanoparticles is formed (the property of Pd is relatively stable and it is difficult to be oxidized in air, while Mo will be oxidized to MoO x ) during long-term aging in air, which is the MoO x / Pd hybrid nanoparticle assembly material. When sensing ethanol, the MoO x nanoparticles serve as ethanol sensing materials, and the Pd nanoparticles play a synergistic catalytic role, reducing the reaction activation energy and improving the ethanol sensing ability.

[0010] The ethanol gas-sensitive material based on a Pd / MoO x nanoparticle assembly structure, characterized in that the mass percentage of Pd nanoparticles in the Pd / MoO x nanoparticle assembly material is 0.5% - 10%.

[0011] The present invention also provides an ethanol gas-sensitive material based on a Pd / MoO xPreparation method of ethanol gas-sensitive material with nanoparticle assembly structure. The preparation process is as follows: Place high-purity Mo target and high-purity Pd target on two sputtering guns of a cluster beam deposition device respectively. Place the interdigital electrode with an insulating substrate in the deposition chamber of the cluster beam deposition system. Evacuate the whole device. After the vacuum degree reaches the requirement, introduce sputtering gas into both sputtering guns, introduce buffer gas into the sputtering chamber of the cluster beam deposition system, and apply voltage. First, partially vaporize the Mo target and Pd target into gaseous molecules or atoms, then the buffer gas collides with them to form nanoparticles, and form a nanoparticle beam through the method of differential pumping. Then direct the beam to the deposition chamber of the cluster beam deposition device and deposit it on the surface of the placed interdigital electrode with an insulating substrate, thus obtaining the Mo / Pd nanoparticle assembly material. After the preparation is completed, take out the interdigital electrode, and after aging, form Pd / MoO x nanoparticle assembly material. Place the material in the test cavity, connect a stable voltage to the interdigital electrode with a Keithley digital source meter. After introducing ethanol gas with a certain concentration, ethanol reacts with the adsorbed oxygen on the material surface, causing a change in the material resistance, thereby resulting in a change in the current displayed on the source meter. According to the formula:

[0012]

[0013] where I a is the current value displayed on the Keithley digital source meter before introducing ethanol, I g is the current value displayed on the Keithley digital source meter after introducing ethanol. The response performance of the material to ethanol can be obtained through calculation.

[0014] Furthermore, in the preparation method of the ethanol gas-sensitive material based on the Pd / MoO x nanoparticle assembly structure, use high-purity argon with a purity of more than 99.99% as the sputtering gas, use high-purity helium with a purity of more than 99.99% as the buffer gas, and maintain the gas pressure in the sputtering chamber at 50 - 150 Pa.

[0015] Furthermore, in the preparation method of the ethanol gas-sensitive material based on the Pd / MoO x nanoparticle assembly structure, in step (3), set the sputtering power of the Mo target to 12 - 18 W, its sputtering current is 0.03 - 0.0375 A, the sputtering voltage is 400 - 480 V, and the sputtering time is 180 - 250 s.

[0016] Furthermore, in the preparation method of the ethanol gas-sensitive material based on the Pd / MoO xIn the preparation method of the ethanol gas-sensitive material with a nanoparticle assembly structure, in step (3), the sputtering power of the Pd target is set to 10-15 W, its sputtering current is 0.033-0.042 A, the sputtering voltage is 300-360 V6, and the sputtering time is 80-150 s.

[0017] A sensor device includes the ethanol gas-sensitive material based on the Pd / MoOx nanoparticle assembly structure of the present invention.

[0018] The beneficial effects achieved by the present invention are as follows: The molybdenum oxide and palladium hybrid nanoparticle assembly material involved in the present invention has more adsorbed oxygen content properties. And due to the chemical modification and synergistic catalytic effect of Pd nanoparticles on ethanol, the hybrid nanoparticle assembly material has more active sites compared with a single MoO x and can achieve high sensitivity and rapid response perception of ethanol at a lower temperature. In addition, since the sputtered material is a nanoparticle assembly material, it has a higher specific surface area than a thin film, can greatly increase the contact opportunity with ethanol, create more reaction sites, and can effectively promote the rapid response to ethanol. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the structure of the nanoparticle assembly material prepared by the present invention.

[0020] Figure 2a It is the response curve of the nanoparticle assembly material prepared by the present invention to different ethanol concentrations at 180 °C.

[0021] Figure 2b It is the linear fitting relationship between the response degree and the ethanol concentration when the nanoparticle assembly material prepared by the present invention is tested with different concentrations of ethanol at 180 °C. Specific Embodiment

[0022] The following further illustrates the present invention with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0023] Example 1:

[0024] A preparation method of an ethanol gas-sensitive material based on a Pd / MoO x nanoparticle assembly structure includes the following steps:

[0025] (1) Preparation of the Pd / MoO x nanoparticle assembly material: Place the high-purity Mo target and the high-purity Pd target on two sputtering guns of the cluster beam deposition equipment respectively. Place the substrate with interdigitated electrodes in the deposition chamber of the cluster beam deposition system, evacuate the entire device, and make the vacuum in the deposition chamber reach 2×10 -4 Pa.

[0026] Introduce 50 sccm of sputtering gas into the sputtering gun equipped with a Mo target, and introduce 80 sccm of buffer gas into the sputtering chamber. At this time, the pressure in the sputtering chamber is 110 Pa. Then, apply a power of 15 W to the sputtering gun equipped with the Mo target. At this time, the sputtering current is 0.034 A and the sputtering voltage is 441 V. The sputtering time is 500 s. Turn off the sputtering gas and the power supply.

[0027] Then, introduce 50 sccm of sputtering gas into the sputtering gun equipped with a Pd target, and introduce 80 sccm of buffer gas into the sputtering chamber. At this time, the pressure in the sputtering chamber is 110 Pa. Then, apply a power of 12 W to it. At this time, the sputtering current is 0.038 A and the sputtering voltage is 315 V. The deposition time is 100 s. Obtain the Mo / Pd nanoparticle assembly material, and its structural schematic diagram is as Figure 1 shown.

[0028] Use high-purity argon with a purity of more than 99.99% as the sputtering gas, and use high-purity helium with a purity of more than 99.99% as the buffer gas.

[0029] Place the obtained Mo / Pd nanoparticle assembly material in the air for aging for 24 h to obtain the Pd / MoO x nanoparticle assembly material, where the mass percentage of Pd in the Pd / MoO x nanoparticles accounts for approximately 0.61%. Perform ethanol gas-sensing performance testing on the above-obtained Pd / MoO x nanoparticle assembly material:

[0030] (2) Place the interdigital electrode deposited with the Pd / MoOx nanoparticle assembly material in the test cavity, and use a PID temperature controller to heat the interdigital electrode deposited with the Pd / MoOx nanoparticle assembly material to 180 °C. Connect both ends of the interdigital electrode to a Keithley digital source meter, and use the digital source meter to apply a stable voltage of 1 V to both ends of the interdigital electrode, and read the current at both ends of the assembly material through the source meter.

[0031] Adopt the bubbling method to control the ethanol gas flow rate and air flow rate through a flow meter, introduce ethanol gas with different concentrations into the test cavity, record the current values before and after ventilation, and use the formula:

[0032]

[0033] where I a is the current value shown on the Keithley digital source meter of the material before introducing ethanol, I gIt is the current value shown on the Keithley digital source meter after ethanol is introduced into the material. The response of the material to ethanol can be obtained through calculation, and the measured results are shown in Figure 2a and Figure 2b . It can be seen from the figure that the detection range is 0-1000 ppm, and the response time T 90 < 80 s, and the response degree is 0-300%.

[0034] The MoO prepared by traditional chemical methods x has an optimal response temperature to ethanol as high as 260 °C, a response time of 111 s, and a maximum response of 23% at an ethanol concentration of 100 ppm. For example, the literature: Farzi-Kahkesh S, Rahmani M B, Fattah A. Growth of novel α-MoO3 hierarchical nanostructured thin films for ethanol sensing[J]. Materials Science in Semiconductor Processing, 2020, 120: 105263.

[0035] In summary, compared with the gas-sensitive response effect of the existing MoOx continuous thin film to ethanol, the present invention uses physical vapor deposition technology to prepare Pd / MoOx nanoparticle assembly materials through cluster beam deposition technology and realizes ethanol sensing. This invention can greatly improve the sensing ability of molybdenum oxide to ethanol and reduce the working temperature to 180 °C.

Claims

1. An ethanol gas-sensing material based on a Pd / MoO x nanoparticle assembly structure, characterized in that It includes interdigital electrodes with an insulating substrate, as well as Mo nanoparticles and Pd nanoparticles deposited successively on the surface of the interdigital electrodes. After aging in air, the Mo nanoparticles are oxidized to MoO x , forming a disordered and uniform mixed structure of molybdenum oxide MoO x nanoparticles and Pd nanoparticles. This is the MoO x / Pd hybrid nanoparticle assembly material. When sensing ethanol, the MoO x nanoparticles serve as the ethanol sensing material, and the Pd nanoparticles play a synergistic catalytic role, reducing the reaction activation energy and improving the ethanol sensing ability; The mass percentage of Pd nanoparticles in the Pd / MoO x nanoparticle assembly material is 0.5% to 10%; The described preparation method of an ethanol gas-sensitive material based on a Pd / MoO x nanoparticle assembly structure, which is prepared based on the cluster beam deposition technology, and the preparation method includes the following steps: (1) Place high-purity Mo and Pd targets on two sputtering guns of the cluster beam deposition equipment respectively, place the interdigital electrode with an insulating substrate in the deposition chamber of the cluster beam deposition system, and evacuate the whole device. (2) Introduce sputtering gas into both of the two sputtering guns, and introduce buffer gas into the sputtering chamber of the cluster beam deposition system. (3) Sputter the Mo and Pd targets successively. First deposit Mo nanoparticles on the surface of the interdigital electrode, and then deposit Pd nanoparticles. (4) The deposited Mo and Pd nanoparticles are aged in air for more than 3 hours, causing the Mo nanoparticles to be oxidized into MoO x , forming a disordered and uniform mixed structure composed of molybdenum oxide MoO x nanoparticles and Pd nanoparticles on the surface of the interdigital electrodes; In step (3), set the sputtering power of the Mo target to 12 - 18 W, its sputtering current to 0.03 - 0.0375 A, sputtering voltage to 400 - 480 V, and sputtering time to 180 - 250 s. In step (3), set the sputtering power of the Pd target to 10 - 15 W, its sputtering current to 0.033 - 0.042 A, sputtering voltage to 300 - 360 V, and sputtering time to 80 - 150 s.

2. The ethanol gas-sensitive material based on the Pd / MoO x nanoparticle assembly structure, characterized in that Use high-purity argon with a purity of more than 99.99% as the sputtering gas, use high-purity helium with a purity of more than 99.99% as the buffer gas, and maintain the gas pressure in the sputtering chamber at 50 - 150 Pa.

3. A sensor device, characterized in that, The sensor device includes the ethanol gas-sensitive material based on the Pd / MoO x nanoparticle assembly structure as described in Claim 1.

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