Nb-TiO2 / WO3 junction powder material-based room-temperature MEMS carbon monoxide sensor and preparation method thereof

Abstract

The invention discloses a room-temperature MEMS carbon monoxide sensor based on an Nb-TiO2 / WO3 heterojunction powder material and a preparation method of the room-temperature MEMS carbon monoxide sensor, and relates to the technical field of carbon monoxide gas detection. The preparation method comprises the following steps: S1, preparing an Nb-TiO2 / WO3 heterojunction powder material by a two-step hydrothermal method; s2, 0.5 g of the Nb-TiO2 / WO3 heterojunction powder material, the aluminum oxide dispersion liquid and glycerol are mixed and subjected to ball milling, and slurry needed by the MEMS carbon monoxide sensor is obtained; s3, dispensing the slurry onto an MEMS gas sensor substrate with an electrode; according to the room-temperature MEMS carbon monoxide sensor provided by the invention, the sensitivity and selectivity of TiO2 to carbon monoxide can be improved through Nb doping and WO3 modification, the combination of the Nb-doped and WO3-modified semiconductor gas-sensitive material and the MEMS device can utilize the characteristics of miniaturization, easy integration, low power consumption, good stability and the like of the MEMS device, and the gas-sensitive gas-sensitive material can be used as a gas-sensitive gas-sensitive material for the room-temperature MEMS carbon monoxide sensor. The response and working consistency of the TiO2 gas-sensitive material to CO at room temperature is greatly improved, and the method has important practical application value for further promoting the development of semiconductor gas-sensitive devices.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon monoxide gas detection, and in particular to a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material and a preparation method thereof. Background Art

[0002] Carbon monoxide (CO) is a colorless and odorless toxic gas. After entering the human body, CO can bind to hemoglobin to form carboxyhemoglobin, which prevents hemoglobin from binding to oxygen, causing poisoning, and in severe cases, life-threatening. Incomplete combustion of industrial fuels, automobile exhaust, etc. will release a large amount of CO, so effective monitoring of CO is very necessary. Metal oxide semiconductor sensors have been widely studied due to their low cost, high sensitivity, and fast response recovery. Currently, a lot of research work is focused on improving the sensitivity of CO sensors and reducing their detection limits. Their working performance at room temperature is still challenging. For the commercial application of sensors, the two factors of response and sensitivity at room temperature are crucial. Therefore, it is very important to prepare a metal oxide semiconductor CO gas sensor that is responsive and sensitive under room temperature conditions.

[0003] TiO2, with its excellent stability, ease of synthesis, and ability to manipulate its surface properties, has become a sensitive material for detecting a variety of toxic, hazardous, or flammable and explosive gases. However, TiO2-based sensors exhibit poor sensitivity to carbon monoxide at room temperature. Nb doping and WO3 modification can improve their sensitivity to carbon monoxide and lower their operating temperature. Combining Nb-doped and WO3-modified TiO2 with MEMS devices can reduce device size, lower power consumption, and enhance device safety and stability. Summary of the Invention

[0004] The object of the present invention is to provide a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material and a preparation method thereof, so as to solve the problems in the current market raised by the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material, comprising the following steps:

[0006] S1. Prepare Nb-TiO2 / WO3 heterojunction powder material by two-step hydrothermal method; the preparation method of Nb-TiO2 / WO3 heterojunction powder material comprises the following steps:

[0007] Preparation of Nb-TiO2 nanosheet powder by hydrothermal method:

[0008] S1-1, take 8mL of hydrofluoric acid into a centrifuge tube, then add a certain amount of ethanol and niobium, ultrasonicate for 10 minutes;

[0009] S1-2, take 20 mL of tetrabutyl titanate and 20 mL of anhydrous ethanol in the inner liner of a 100 mL reactor and stir for 5 minutes, then slowly add the hydrofluoric acid solution prepared in the centrifuge tube in the previous step and stir for 1 hour;

[0010] S1-3. Place the reactor in an oven at 180°C for 16 hours to obtain a white powder material. Wash the powder material with ethanol, 0.1 mol / L NaOH aqueous solution, and deionized water, respectively. Place the washed sample in an oven at 80°C for 24 hours, then take it out and grind it in a mortar to obtain Nb-TiO2 nanosheet powder.

[0011] Preparation of Nb-TiO2 / WO3 heterojunction powder by hydrothermal method:

[0012] S1-4. Add Na2WO4·2H2O to a beaker at a certain molar ratio of Ti to W, heat and stir at 70°C for 30 minutes; after cooling to room temperature, transfer to a reactor and add 0.1g of Nb-TiO2 nanosheet powder prepared in S1-3 and 2.5mL of HCl. After stirring thoroughly for 30 minutes, place the reactor in an oven at 150°C for 720 minutes;

[0013] S1-5. After the reaction is completed, wash with ethanol and deionized water respectively, and dry in a vacuum drying oven at 60°C for 12 hours to obtain Nb-TiO2 / WO3 heterojunction powder;

[0014] S1-6, annealing the obtained Nb-TiO2 / WO3 heterojunction powder at 450°C for 2 hours;

[0015] S2. Take 0.5g of Nb-TiO2 / WO3 heterojunction powder material, alumina dispersion, and glycerol and mix them by ball milling to obtain the slurry required for MEMS carbon monoxide sensor;

[0016] S3, applying the slurry onto a MEMS gas sensor substrate with electrodes, and drying at 80° C. to obtain a resistive MEMS carbon monoxide sensor;

[0017] S4. Place the MEMS carbon monoxide sensor on a base with a heating electrode and a test electrode, and continue heating and aging for 12 hours in an air atmosphere.

[0018] Preferably, in the S1, 0.5 g of the annealed Nb-TiO2 / WO3 heterojunction powder is taken into a ball mill, and an alumina dispersion is added according to a ratio of 2:1 between the powder and alumina, and then a certain amount of anhydrous ethanol is added and ball milled for 2 hours. 1 mL of propylene glycol is added to the ball-milled and dried powder and ball milled for 4 hours to obtain a Nb-TiO2 / WO3 slurry.

[0019] Preferably, in the S1-1, the doping amount of Nb is 0.6 mol%.

[0020] Preferably, in S1-4, the molar ratio of Ti to W is 1:5.

[0021] The present invention also provides a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material, which is prepared using the above-mentioned preparation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a room-temperature MEMS carbon monoxide sensor, which can improve the sensitivity and selectivity of TiO2 to carbon monoxide through Nb doping and WO3 modification. The combination of Nb-doped and WO3-modified semiconductor gas-sensitive materials and MEMS devices can take advantage of the miniaturization, easy integration, low power consumption, and good stability of MEMS devices to greatly improve the response and working consistency of TiO2 gas-sensitive materials at room temperature, which has important practical application value for further promoting the development of semiconductor gas-sensitive devices.

[0024] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a SEM photo of the Nb-TiO2 / WO3 heterojunction powder material prepared in the present invention;

[0026] Figure 2 This is one of the response graphs of the Nb-TiO2 / WO3 heterojunction powder material with different Nb doping ratios to carbon monoxide in the present invention;

[0027] Figure 3 This is the second graph of the response of the Nb-TiO2 / WO3 heterojunction powder material with different Nb doping ratios to carbon monoxide in the present invention;

[0028] Figure 4 This is the third graph of the response of the Nb-TiO2 / WO3 heterojunction powder material with different Nb doping ratios to carbon monoxide according to the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1:

[0031] Nb-doped TiO2 powder was prepared by hydrothermal method:

[0032] Take 8 mL of hydrofluoric acid in a centrifuge tube, add 0.4% mol (59 μl) of niobium ethanol and sonicate for 10 minutes;

[0033] Take 20 mL of tetrabutyl titanate and 20 mL of anhydrous ethanol and stir them in the inner liner of a 100 mL reactor for 5 minutes. Then slowly add the hydrofluoric acid solution prepared in the centrifuge tube in the previous step and stir for 1 hour.

[0034] The reactor was placed in an oven at 180°C for 16 hours, and the reaction product was taken out and washed with ethanol, 0.1 mol / L NaOH aqueous solution, and deionized water respectively. The washed sample was placed in an oven at 80°C for 24 hours, and then taken out and ground into 0.4% Nb-TiO2 powder in a mortar.

[0035] 2g of Na2WO4·2H2O was added to a beaker at a Ti:W molar ratio of 1:5 and heated with stirring at 70°C for 30 minutes. After cooling to room temperature, the mixture was transferred to a reactor, where 0.1g of Nb-TiO2 nanosheet powder and 2.5mL of HCl were added. After thorough stirring for 30 minutes, the reactor was placed in an oven at 150°C and reacted for 720 minutes. After the reaction, the mixture was washed with ethanol and deionized water, respectively, and dried in a vacuum oven at 60°C for 12 hours to obtain a Nb-TiO2 / WO3 heterojunction powder. The resulting Nb-TiO2 / WO3 heterojunction powder was then annealed at 450°C for 2 hours.

[0036] Preparation of the slurry required for spot coating: Take 0.5 g of annealed Nb-TiO2 / WO3 powder and put it in a ball mill. Add 250 μl of alumina dispersion at a ratio of 2:1 between powder and alumina. Then add a certain amount of anhydrous ethanol and ball mill for 2 hours. Add 1 mL of propylene glycol to the ball-milled and dried powder and ball mill for 4 hours to obtain the slurry required for spot coating.

[0037] The prepared slurry was spot-coated on a sensor printed with an Au electrode and placed in an oven at 80°C until dry. Finally, the obtained MEMS device was placed on a base with a heating electrode and a test electrode and aged in an air atmosphere for 12 hours to obtain a MEMS carbon monoxide sensor.

[0038] Example 2:

[0039] Nb-doped TiO2 powder was prepared by hydrothermal method:

[0040] Take 8 mL of hydrofluoric acid in a centrifuge tube, add 0.6% mol (88.4 μl) of niobium ethanol and sonicate for 10 minutes;

[0041] Take 20 mL of tetrabutyl titanate and 20 mL of anhydrous ethanol and stir them in the inner liner of a 100 mL reactor for 5 minutes. Then slowly add the hydrofluoric acid solution prepared in the centrifuge tube in the previous step and stir for 1 hour.

[0042] The reactor was placed in an oven at 180°C for 16 hours, and the reaction product was taken out and washed with ethanol, 0.1 mol / L NaOH aqueous solution, and deionized water respectively. The washed sample was placed in an oven at 80°C for 24 hours, and then taken out and ground into 0.6% Nb-TiO2 powder in a mortar.

[0043] 2g of Na2WO4·2H2O was added to a beaker at a Ti:W molar ratio of 1:5 and heated with stirring at 70°C for 30 minutes. After cooling to room temperature, the mixture was transferred to a reactor, where 0.1g of Nb-TiO2 nanosheet powder and 2.5mL of HCl were added. After thorough stirring for 30 minutes, the reactor was placed in an oven at 150°C and reacted for 720 minutes. After the reaction, the mixture was washed with ethanol and deionized water, respectively, and dried in a vacuum oven at 60°C for 12 hours to obtain a Nb-TiO2 / WO3 heterojunction powder. The resulting Nb-TiO2 / WO3 heterojunction powder was then annealed at 450°C for 2 hours.

[0044] Preparation of the slurry required for spot coating: Take 0.5 g of annealed Nb-TiO2 / WO3 powder and put it in a ball mill. Add 250 μl of alumina dispersion at a ratio of 2:1 between powder and alumina. Then add a certain amount of anhydrous ethanol and ball mill for 2 hours. Add 1 mL of propylene glycol to the ball-milled and dried powder and ball mill for 4 hours to obtain the slurry required for spot coating.

[0045] The prepared slurry was spot-coated on a sensor printed with an Au electrode and placed in an oven at 80°C until dry. Finally, the obtained MEMS device was placed on a base with a heating electrode and a test electrode and aged in an air atmosphere for 12 hours to obtain a MEMS carbon monoxide sensor.

[0046] Example 3:

[0047] Nb-doped TiO2 powder was prepared by hydrothermal method:

[0048] Take 8 mL of hydrofluoric acid in a centrifuge tube, add 0.8% mol (117.8 μl) of niobium ethanol and sonicate for 10 minutes;

[0049] Take 20 mL of tetrabutyl titanate and 20 mL of anhydrous ethanol and stir them in the inner liner of a 100 mL reactor for 5 minutes. Then slowly add the hydrofluoric acid solution prepared in the centrifuge tube in the previous step and stir for 1 hour.

[0050] The reactor was placed in an oven at 180°C for 16 hours, and the reaction product was taken out and washed with ethanol, 0.1 mol / L NaOH aqueous solution, and deionized water respectively. The washed sample was placed in an oven at 80°C for 24 hours, and then taken out and ground into 0.8% Nb-TiO2 powder in a mortar.

[0051] 2g of Na2WO4·2H2O was added to a beaker at a Ti:W molar ratio of 1:5 and heated with stirring at 70°C for 30 minutes. After cooling to room temperature, the mixture was transferred to a reactor, where 0.1g of Nb-TiO2 nanosheet powder and 2.5mL of HCl were added. After thorough stirring for 30 minutes, the reactor was placed in an oven at 150°C and reacted for 720 minutes. After the reaction, the mixture was washed with ethanol and deionized water, respectively, and dried in a vacuum oven at 60°C for 12 hours to obtain a Nb-TiO2 / WO3 heterojunction powder. The resulting Nb-TiO2 / WO3 heterojunction powder was then annealed at 450°C for 2 hours.

[0052] Preparation of the slurry required for spot coating: Take 0.5 g of annealed Nb-TiO2 / WO3 powder and put it in a ball mill. Add 250 μl of alumina dispersion according to the ratio of powder to alumina of 2:1. Then add a certain amount of anhydrous ethanol and ball mill for 2 hours. Add 1 mL of propylene glycol to the ball-milled and dried powder and ball mill for 4 hours to obtain the slurry required for spot coating.

[0053] The prepared slurry was spot-coated on a sensor printed with an Au electrode and placed in an oven at 80°C until dry. Finally, the obtained MEMS device was placed on a base with a heating electrode and a test electrode and aged in an air atmosphere for 12 hours to obtain a MEMS carbon monoxide sensor.

[0054] Nb doping and WO3 modification can increase its sensitivity to carbon monoxide and reduce operating temperature. Combining Nb doped and WO3 modified TiO2 with MEMS devices can reduce device size, reduce device power consumption, and improve device safety and stability.

[0055] Figures 2 to 4The response diagram of Nb-TiO2 / WO3 heterojunction powder materials with different Nb doping ratios to carbon monoxide is shown in FIG. Figure 1 As shown, Figure 1 The SEM photo of the Nb-TiO2 / WO3 heterojunction powder material is shown. It can be seen from the figure that the powder material has a uniform particle size distribution and good crystallinity, which provides the basis for the high sensitivity and selectivity of the sensor. Figures 2 to 4 It can be seen that with the increase of Nb doping ratio, the response of the sensor to carbon monoxide first increases and then decreases, and there is an optimal doping ratio. In this experiment, the Nb doping ratio of 0.6% showed the best response characteristics, verifying the optimal doping ratio mentioned in the document. The present invention comprehensively solves the problems in the prior art that MEMS gas-sensitive materials are difficult to have a high response to carbon monoxide at room temperature. Nb-TiO2 / WO3 powder is prepared by Nb doping modification and surface WO3 modification, and the slurry required for spot coating is prepared. Spot coating on MEMS devices for aging can achieve the preparation of MEMS sensors with high bonding strength, high sensitivity and long-term stability. Compared with traditional methods, this MEMS sensor has the characteristics of small size, easy integration, high consistency and low power consumption. It has broad application prospects in the highly sensitive identification of toxic gases and the manufacture of new array gas sensors.

[0056] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0057] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material, characterized in that: The steps include: S1. Prepare Nb-TiO2 / WO3 heterojunction powder material by two-step hydrothermal method; the preparation method of Nb-TiO2 / WO3 heterojunction powder material comprises the following steps: Preparation of Nb-TiO2 nanosheet powder by hydrothermal method: S1-1, take 8mL of hydrofluoric acid into a centrifuge tube, then add a certain amount of ethanol and niobium, ultrasonicate for 10 minutes; S1-2, take 20 mL of tetrabutyl titanate and 20 mL of anhydrous ethanol in the inner liner of a 100 mL reactor and stir for 5 minutes, then slowly add the hydrofluoric acid solution prepared in the centrifuge tube in the previous step and stir for 1 hour; S1-3. Place the reactor in an oven at 180°C for 16 hours to obtain a white powder material. Wash the powder material with ethanol, 0.1 mol / L NaOH aqueous solution, and deionized water, respectively. Place the washed sample in an oven at 80°C for 24 hours, then take it out and grind it in a mortar to obtain Nb-TiO2 nanosheet powder. The Nb-TiO2 / WO3 heterojunction powder is prepared by a hydrothermal method; specifically, the method includes: S1-4. Add Na2WO4·2H2O to a beaker at a certain molar ratio of Ti to W, heat and stir at 70°C for 30 minutes; after cooling to room temperature, transfer to a reactor and add 0.1g of Nb-TiO2 nanosheet powder prepared in S1-3 and 2.5mL of HCl. After thorough stirring for 30 minutes, place the reactor in an oven at 150°C for 720 minutes; S1-5. After the reaction is completed, wash with ethanol and deionized water respectively, and dry in a vacuum drying oven at 60°C for 12 hours to obtain Nb-TiO2 / WO3 heterojunction powder; S1-6, annealing the obtained Nb-TiO2 / WO3 heterojunction powder at 450°C for 2 hours; S2. Take 0.5g of Nb-TiO2 / WO3 heterojunction powder material, alumina dispersion, and glycerol and mix them by ball milling to obtain the slurry required for MEMS carbon monoxide sensor; S3, applying the slurry onto a MEMS gas sensor substrate with electrodes, and drying at 80° C. to obtain a resistive MEMS carbon monoxide sensor; S4. Place the MEMS carbon monoxide sensor on a base with a heating electrode and a test electrode, and continue heating and aging for 12 hours in an air atmosphere.

2. The method for preparing a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material according to claim 1, characterized in that: In the S1, 0.5 g of the annealed Nb-TiO2 / WO3 heterojunction powder is taken into a ball mill, and an alumina dispersion is added in a ratio of 2:1 between the powder and alumina, and then a certain amount of anhydrous ethanol is added and ball milled for 2 hours. 1 mL of propylene glycol is added to the ball-milled and dried powder and ball milled for 4 hours to obtain a Nb-TiO2 / WO3 slurry.

3. The method for preparing a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material according to claim 1, characterized in that: In the S1-1, the doping amount of Nb is 0% to 1.5% mol.

4. The method for preparing a room-temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material according to claim 1, characterized in that: In the S1-4, the molar ratio of Ti to W is 2-0.

15.

5. A room temperature MEMS carbon monoxide sensor based on Nb-TiO2 / WO3 heterojunction powder material, characterized in that: The method is prepared according to any one of claims 1 to 4.

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