CN116337950A - LaFeO based on oxygen-enriched vacancy 3 Preparation method of nanoparticle high-performance formaldehyde gas sensor - Google Patents
LaFeO based on oxygen-enriched vacancy 3 Preparation method of nanoparticle high-performance formaldehyde gas sensor Download PDFInfo
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Abstract
The invention discloses a LaFeO based on oxygen-enriched vacancy 3 Preparation method of nanoparticle high-performance formaldehyde gas sensor, belongs to the field of chemiresistive gas sensor, and is based on LaFeO rich in oxygen vacancies 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor comprises the steps of mixing lanthanum nitrate hexahydrate and ethanol solution, mixing trimesic acid and ethanol solution, preparing La/Fe-MOF gel, drying the gel, annealing and preparing LaFeO rich in oxygen vacancies 3 Nanoparticles, ultrasonic cleaning, slurry coating, sensitive material drying and formaldehyde gas sensor generation. The formaldehyde sensor can effectively improve the production efficiency in the production process, simultaneously saves a large amount of use cost, improves the practical effect of the sensor in formaldehyde gas detection, and simultaneously enhances the sensitivity of the formaldehyde sensor.
Description
Technical Field
The invention relates to the field of chemiresistive gas sensors, in particular to a LaFeO based on oxygen-enriched vacancy 3 A preparation method of a nanoparticle high-performance formaldehyde gas sensor.
Background
Formaldehyde is widely used as a colorless and strongly odorous gas in industrial production of resins, paints, plastics, and the like due to its good adhesion and solvent properties. However, excessive formaldehyde contained in the building material causes indoor air pollution, thereby threatening the health of human bodies and causing a series of diseases including sick building syndrome, respiratory diseases and even cancer. People can cause headache, nausea and respiratory diseases even when exposed to low concentrations of formaldehyde. The safe concentration threshold for formaldehyde in an indoor environment was 1ppm as reported by the national institute of occupational safety and health. Therefore, real-time detection of indoor formaldehyde gas concentration has become an important and urgent task. Heretofore, chemical resistance type formaldehyde gas sensors based on n-type semiconductor oxides (such as tin oxide, zinc oxide, tungsten oxide, etc.) have been widely studied for their advantages of high sensitivity, low cost, compatibility with microelectromechanical systems, etc., however, n-type semiconductor oxide based gas sensors also have disadvantages such as high operating temperature and high baseline resistance, which limit their practical application.
In recent years, perovskite semiconductor oxides (ABO 3 ) There is a great interest in the field of gas sensors because of their high thermal stability, adjustable composition, high electron mobility and excellent gas-sensitive properties. Wherein LaFeO 3 As a typical p-type perovskite semiconductor oxide, it shows excellent potential in detecting formaldehyde. However, intrinsic LaFeO 3 The base gas sensor generally exhibits low sensitivity. Many researchers have systematically studied the structure-activity relationship between the microstructure and gas sensitivity of an oxide semiconductor, and found that oxygen vacancies are inherent defects in metal oxides, and can act as an electron carrier to absorb oxygen molecules and form active sites, thereby improving the sensitivity of a gas sensor.
Based on the above, the present inventors found that:
when formaldehyde gas is detected, common methods such as plasma bombardment, heat treatment in a reducing atmosphere and the like have been used for effectively regulating the concentration of oxygen vacancies on the surface of metal oxide, but when the methods are used, due to the limitations of materials and products used, the defects of higher use cost and complex preparation process are easy to occur, so that the practical effect of the products or methods in formaldehyde gas detection is reduced.
Accordingly, in view of the above, an improvement of the conventional structure has been studied and provided by the present invention, which is based on LaFeO rich in oxygen vacancies 3 The preparation method of the high-performance formaldehyde gas sensor with the nano particles aims to achieve the purpose of higher practical value.
Disclosure of Invention
1. Technical problem to be solved
In view of the problems of the prior art, an object of the present invention is to provide a LaFeO based on oxygen-enriched vacancies 3 The preparation method of the high-performance formaldehyde gas sensor of the nano particles can effectively improve the production efficiency in the production process, simultaneously save a large amount of use cost, improve the practical effect of the sensor in formaldehyde gas detection and simultaneously enhance the sensitivity of the formaldehyde gas sensor.
2. Technical proposal
In order to solve the problems, the invention adopts the following technical scheme.
LaFeO based on oxygen-enriched vacancy 3 Preparation method of nanoparticle high-performance formaldehyde gas sensor comprises formaldehyde gas sensor, wherein the formaldehyde gas sensor comprises Al 2 O 3 A ceramic tube substrate, the Al 2 O 3 A nickel-chromium alloy heating wire is fixedly arranged in the ceramic tube lining, and the Al is 2 O 3 A pair of annular gold electrodes are fixedly printed at two ends of the ceramic tube lining, and the Al is 2 O 3 The surface of the ceramic tube lining is uniformly coated with a gas sensitive film;
the gas sensitive film is derived to be rich in oxygen vacancy LaFeO by adopting MOF template method 3 Nanoparticles based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor prepared by the nano particles comprises the following specific steps:
step S1: adding 10-14 mmol of lanthanum nitrate hexahydrate and 10-14 mmol of ferric nitrate nonahydrate into 30-50 ml of ethanol, and stirring at room temperature for 0.5-2 h to obtain a uniform solution A of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 10-14 mmol of trimesic acid into 30-50 ml of ethanol to obtain trimesic acid ethanol solution;
step S3: pouring the mixed solution A prepared in the step S1 into the trimesic acid ethanol solution based on the step S2, and stirring for 2-10 min at room temperature to obtain La/Fe-MOF gel;
step S4: setting the La/Fe-MOF gel based on the step S3 in a vacuum drying oven at 60-100 ℃ and drying for 12-18 h to obtain a La/Fe-MOF sample;
step S5: based on the La/Fe-MOF sample of the step S4, placing the La/Fe-MOF sample in a tube furnace for annealing, controlling the heating rate to be 5-10 ℃/min, the annealing temperature to be 700-900 ℃ and the annealing time to be 3-5 h, removing the organic ligand in the La/Fe-MOF precursor, and obtaining the LaFeO rich in oxygen vacancies 3 A nanoparticle;
step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and pure water 2 O 3 Ceramic tube and drying;
step S7: based on the step S5, 5 to 15mg of LaFeO rich in oxygen vacancies is weighed 3 Mixing nano particles and ethanol in a mass ratio of (4-6) 1, grinding into uniform slurry, uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 Forming an object B on the ceramic tube;
step S8: based on the object B in the step S7, placing the object B in an oven at 60-80 ℃ for 30-90 min, and after the sensitive material is dried, passing a nichrome heating wire with a resistance value of 30-40 omega through Al with the sensitive material 2 O 3 Ceramic tube, al with sensitive material is obtained 2 O 3 A ceramic tube;
step S9: al based on step S8 2 O 3 Ceramic tube, al 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base to form an object C, and aging for 2-5 days at 250-350 ℃ to obtain the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
In step S1, the ambient temperature range of the room temperature is controlled to be 15 ℃ to 25 ℃.
Further, in the step S2, when trimesic acid is introduced into ethanol by filling in a paper tank, the mixed solution is slowly stirred.
In step S3, the ambient temperature range of the room temperature is controlled to be 15-20 ℃.
Further, in the step S4, a temperature and humidity sensor with the model number of HK2022011401 is adopted to monitor the humidity in the vacuum drying oven, and when the temperature value is less than 30% rh, drying is completed.
Further, in the step S5, the temperature rise time is controlled to be 90 to 140 minutes.
Further, in the step S6, when no obvious debris falls during the ultrasonic cleaning, it is determined that the ultrasonic cleaning is completed.
Further, in the step S7, ethanol is added to LaFeO rich in oxygen vacancies when the slurry is mixed 3 In the nanoparticle, and stirring.
Further, in step S8, a temperature and humidity sensor with the model HK2022011401 is used to monitor the temperature and humidity in the vacuum drying oven, and the temperature value is determined to be less than 20% rh, so as to determine that drying is completed.
Further, in the step S9, the working humidity of the formaldehyde gas sensor is less than or equal to 90% rh, and the detection range of the formaldehyde gas sensor is 0-5000 ppm.
3. Advantageous effects
Compared with the prior art, the invention has the advantages that:
(1) In the scheme, the MOF template method is adopted to synthesize the LaFeO rich in oxygen vacancies 3 Sensitive material and is matched with Al 2 O 3 The ceramic tube forms the formaldehyde detection sensor with high sensitivity and high precision, the manufacturing process of the whole formaldehyde detection sensor is simpler, the production efficiency can be effectively improved in the production process, a large amount of use cost is saved, the practical effect of the sensor in formaldehyde gas detection is improved, and meanwhile, the prepared LaFeO is prepared 3 The nanoparticle sensitive material has rich oxygen vacancies and large ratioThe surface area can provide more active sites for the target gas, so that the sensitivity of the formaldehyde sensor is enhanced;
(2) In the scheme, the LaFeO rich in oxygen vacancies is synthesized by a MOF template method 3 Sensitive material, and the temperature, time and speed of synthesis are precisely controlled in the synthesis process, so as to ensure that the LaFeO rich in oxygen vacancies after synthesis 3 The quality of sensitive materials is high, the whole synthesis process is simple to operate, the cost is low, the yield is high, the production period is short, and the method is suitable for batch production;
(3) The scheme is based on LaFeO rich in oxygen vacancy 3 The formaldehyde sensor has high sensitivity and excellent selectivity to formaldehyde gas at a lower working temperature of 160 ℃, can detect formaldehyde gas as low as 1ppm, has quick response and recovery time, good repeatability and long-term stability, and has wide application prospect in the aspect of indoor volatile organic compound detection.
Drawings
FIG. 1 is a schematic diagram of the X-ray diffraction pattern of La/Fe-MOF in example 1 of the present invention;
FIG. 2 shows the La/Fe-MOF derived oxygen vacancy-enriched LaFeO in example 1 of the present invention 3 An X-ray diffraction pattern diagram of the nanoparticle;
FIG. 3 shows the oxygen vacancy-enriched LaFeO of example 1 of the present invention 3 Scanning electron microscope image schematic diagram of nano particles;
FIG. 4 shows the oxygen vacancy-enriched LaFeO of example 1 of the present invention 3 Schematic of X-ray photoelectron spectrum of O1s of nanoparticles;
FIG. 5 shows the oxygen-enriched LaFeO of example 1 3 Electron paramagnetic resonance spectroscopy of nanoparticles is shown;
FIG. 6 shows the oxygen-enriched vacancy based LaFeO of example 1 of the present invention 3 The dynamic resistance response curve of the formaldehyde sensor of the nano particles to formaldehyde with different concentrations at 160 ℃ is shown schematically;
FIG. 7 shows the oxygen-enriched vacancy based LaFeO of example 1 of the present invention 3 Schematic of the dynamic response of the nanoparticle formaldehyde sensor to 1ppm formaldehyde at 160 ℃;
FIG. 8 shows the oxygen-enriched vacancy based LaFeO in example 2 of the present invention 3 Schematic of the repeatability curve of the nanoparticle formaldehyde sensor for 30ppm formaldehyde at 160 ℃;
FIG. 9 shows the oxygen-enriched vacancy based LaFeO in example 3 of the present invention 3 Schematic of the sensitivity of the nanoparticle formaldehyde sensor to 100ppm formaldehyde and 100ppm other interfering gases at 160 ℃;
FIG. 10 is a flow chart of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments, and that all other embodiments obtained by persons of ordinary skill in the art without making creative efforts based on the embodiments in the present invention are within the protection scope of the present invention.
Example 1:
referring to FIGS. 1-10, a LaFeO based oxygen-enriched vacancy 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor comprises a formaldehyde gas sensor, wherein the formaldehyde gas sensor comprises Al 2 O 3 Ceramic tube substrate, al 2 O 3 The inside of the ceramic tube lining is fixedly provided with a nickel-chromium alloy heating wire, al 2 O 3 A pair of annular gold electrodes and Al are fixedly printed at two ends of the ceramic tube lining 2 O 3 The surface of the ceramic tube lining is uniformly coated with a gas sensitive film;
the gas sensitive film is derived to be rich in oxygen vacancy LaFeO by adopting MOF template method 3 Nanoparticles based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor prepared by the nano particles comprises the following specific steps:
step S1: adding 10-14 mmol of lanthanum nitrate hexahydrate and 10-14 mmol of ferric nitrate nonahydrate into 30-50 ml of ethanol, and stirring at room temperature for 0.5-2 h to obtain a uniform solution A of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 10-14 mmol of trimesic acid into 30-50 ml of ethanol to obtain trimesic acid ethanol solution;
step S3: pouring the mixed solution A prepared in the step S1 into the trimesic acid ethanol solution based on the step S2, and stirring for 2-10 min at room temperature to obtain La/Fe-MOF gel;
step S4: setting the La/Fe-MOF gel based on the step S3 in a vacuum drying oven at 60-100 ℃ and drying for 12-18 h to obtain a La/Fe-MOF sample;
step S5: based on the La/Fe-MOF sample of the step S4, placing the La/Fe-MOF sample in a tube furnace for annealing, controlling the heating rate to be 5-10 ℃/min, the annealing temperature to be 700-900 ℃ and the annealing time to be 3-5 h, removing the organic ligand in the La/Fe-MOF precursor, and obtaining the LaFeO rich in oxygen vacancies 3 A nanoparticle;
step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and pure water 2 O 3 Ceramic tube and drying;
step S7: based on the step S5, 5 to 15mg of LaFeO rich in oxygen vacancies is weighed 3 Mixing nano particles and ethanol in a mass ratio of (4-6) 1, grinding into uniform slurry, uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 Forming an object B on the ceramic tube;
step S8: based on the object B in the step S7, placing the object B in an oven at 60-80 ℃ for 30-90 min, and after the sensitive material is dried, passing a nichrome heating wire with a resistance value of 30-40 omega through Al with the sensitive material 2 O 3 Ceramic tube, al with sensitive material is obtained 2 O 3 A ceramic tube;
step S9: al based on step S8 2 O 3 Ceramic tube, al 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base to form an object C, and aging for 2-5 days at 250-350 ℃ to obtain the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
In the step S1, the ambient temperature range of the room temperature is controlled to be 15-25 ℃.
When the lanthanum nitrate hexahydrate and the ethanol are in certain hotter or colder environments, the mixing speed of the lanthanum nitrate hexahydrate and the ethanol is easily influenced, and at the moment, the temperature is controlled, so that the lanthanum nitrate hexahydrate and the ethanol can be conveniently mixed in a shorter time, and the volatilization amount of the ethanol in the mixing process is reduced.
In step S2, when trimesic acid is introduced into ethanol by adopting a paper tank filling mode, the mixed solution is slowly stirred.
The paper tank is adopted to slowly inject trimesic acid into ethanol, and the mixed solution is slowly stirred, so that the mixing efficiency of trimesic acid and ethanol can be improved, and the volatilization rate of ethanol can be reduced.
In the step S3, the ambient temperature range of the room temperature is controlled to be 15-20 ℃.
The volatilization amount of the ethanol can be reduced under the condition of controlling the temperature and ensuring the mixing efficiency.
In the step S4, a temperature and humidity sensor with the model of HK2022011401 is adopted to monitor the humidity in the vacuum drying oven, and when the temperature value is judged to be less than 30%rh, the drying is completed.
And detecting the humidity value to judge whether the gel is sufficiently dried or not, so as to ensure the quality of the obtained La/Fe-MOF sample.
In the step S5, the temperature rise time is controlled to be 90-140 min.
The heating time is controlled, the heating speed is properly regulated according to the heating time, the La/Fe-MOF sample is ensured to be in a relatively uniform temperature change state, and the influence on the quality of the La/Fe-MOF sample during annealing due to the rapid change of the temperature is avoided.
In step S6, when no obvious debris falls during ultrasonic cleaning, it is determined that ultrasonic cleaning is completed.
Determining Al according to whether scraps are generated in the ultrasonic cleaning process 2 O 3 Whether the ceramic tube still contains sundries or not is judged whether the ultrasonic cleaning is finished or not, and the influence of the sundries on the quality of the subsequently formed formaldehyde gas sensor can be reduced.
In step S7, ethanol is added to LaFeO rich in oxygen vacancies when the slurry is mixed 3 In the nanoparticle, and stirring.
Control ofEthanol and LaFeO rich in oxygen vacancies 3 The access sequence of the nano particles is that LaFeO rich in oxygen vacancy is added into ethanol 3 When in nano particles, the LaFeO rich in oxygen vacancies can be realized 3 The nano particles can quickly absorb the ethanol, so that the volatilization of the ethanol is reduced.
In step S8, a temperature and humidity sensor with the model of HK2022011401 is adopted to monitor the temperature and humidity in the vacuum drying oven, the temperature value is judged to be less than 20%rh, and drying is judged to be completed.
And detecting the humidity value to judge whether the object B is sufficiently dried or not, so as to ensure the quality of the sensitive material after being connected with the nichrome heating wire.
In the step S9, the working humidity of the formaldehyde gas sensor is less than or equal to 90 percent rh, and the detection range of the formaldehyde gas sensor is 0-5000 ppm.
The formaldehyde gas sensor can work in an environment with higher humidity and has the monitoring function of formaldehyde gas with a wider detection range, so that the actual application function of the formaldehyde gas sensor is improved.
Referring to FIG. 1, the La/Fe-MOF sample showed the same characteristic diffraction peak as the simulated MIL-100 (Fe) from the spectrum, indicating that the La/Fe-MOF sample had the MOF structure.
Referring to FIG. 2, la/Fe-MOF-derived oxygen vacancy enriched LaFeO 3 X-ray diffraction pattern of nanometer particle, and the prepared LaFeO rich in oxygen vacancy 3 Diffraction peak of nanoparticle and orthorhombic LaFeO 3 The diffraction peaks of (2) are consistent, and no other miscellaneous diffraction peaks exist, which indicates that the LaFeO is successfully synthesized by adopting the MOF template method 3 A material.
Referring to FIG. 3, laFeO is enriched in oxygen vacancies 3 LaFeO image of scanning electron microscope 3 Consists of nano particles, has obvious porous structure and uniform particle size of about 50nm.
Referring to FIG. 4, laFeO is enriched in oxygen vacancies 3 The spectrum peaks of the X-ray photoelectron spectrum of (2) are respectively matched with the O of the sensitive material at the positions of 528.3eV, 530.4eV and 532.4eV of the binding energy L (lattice oxygen), O C (chemisorbed oxygen) and O H (hydroxy oxygen) correlation.
Wherein LaFeO 3 Middle O C Peak area is up to 41.0%, higher O C The concentration is favorable for the gas reaction.
Referring to FIG. 5, laFeO is enriched in oxygen vacancies 3 Electron paramagnetic resonance spectrum of (2) and having an absorption peak of obvious oxygen vacancies at g value of 2.004, indicating LaFeO derived from La/Fe-MOF 3 The nanoparticles have abundant oxygen vacancies.
Referring to FIG. 6, a process based on LaFeO rich in oxygen vacancies 3 The transient dynamic response curve of the formaldehyde gas sensor to 5-100 ppm formaldehyde at 160 ℃ is gradually increased along with the increase of formaldehyde concentration, and the sensor can recover to the initial resistance value when the formaldehyde gas sensor is switched into air. In addition, the sensor has rapid response and recovery characteristics to formaldehyde gas.
Referring to FIG. 7, a process based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor has a significant signal response to 1ppm formaldehyde gas at 160 ℃ and can have a practical detection limit for formaldehyde gas as low as 1ppm.
Example 2
See example 1 above and described further.
Step S1: adding 10mmol of lanthanum nitrate hexahydrate and 10mmol of ferric nitrate nonahydrate into 30ml of ethanol, and stirring at room temperature for 0.5h to obtain a uniform solution of the two;
step S2: dissolving 10mmol of trimesic acid into 30ml of ethanol to obtain a uniform solution;
step S3: pouring the trimesic acid solution obtained in the step S2 into the mixed solution of lanthanum nitrate and ferric nitrate obtained in the step S1, and stirring for 2min at room temperature to obtain La/Fe-MOF gel;
step S4: drying the La/Fe-MOF gel obtained in the step S3 in a vacuum drying oven at 60 ℃ for 12 hours to obtain a La/Fe-MOF sample;
step S5: placing the La/Fe-MOF sample obtained in the step S4 in a tube furnace for annealing at a heating rate of 5 ℃/min at 700 ℃ for 3 hours to remove La/Fe-Organic ligand in MOF precursor to obtain LaFeO rich in oxygen vacancy 3 And (3) nanoparticles.
Step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and water 2 O 3 Ceramic tube and drying;
step S7: weighing 5mg of LaFeO rich in oxygen vacancy 3 Mixing the nano particles and ethanol in a mass ratio of 4:1, grinding into uniform slurry, and uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 A ceramic tube;
step S8: placing the device obtained in the step S7 in a 60 ℃ oven for 30min, and after the sensitive material is dried, passing a nichrome heating wire with a resistance value of 30 omega through Al with the sensitive material 2 O 3 A ceramic tube;
step S9: al with sensitive material is obtained in the step S8 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base, aging the prepared device at 250 ℃ for 2 days, thereby obtaining the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
Referring to FIG. 8, a process based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor has consistent sensitivity in four-time response and recovery cycle test at 160 ℃ for the repeatability curve of 30ppm formaldehyde gas, and shows good repeatability.
Example 3
See example 1 above and described further.
Step S1, adding 12mmol of lanthanum nitrate hexahydrate and 12mmol of ferric nitrate nonahydrate into 40ml of ethanol, and stirring for 1h at room temperature to obtain a uniform solution of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 12mmol of trimesic acid into 50ml of ethanol to obtain a uniform solution;
step S3: pouring the trimesic acid solution obtained in the step S2 into the mixed solution of lanthanum nitrate and ferric nitrate obtained in the step S1, and stirring for 5min at room temperature to obtain La/Fe-MOF gel;
step S4: drying the La/Fe-MOF gel obtained in the step S3 in a vacuum drying oven at 80 ℃ for 15 hours to obtain a La/Fe-MOF sample;
step S5: placing the La/Fe-MOF sample obtained in the step S4 in a tube furnace for annealing at a heating rate of 10 ℃/min, an annealing temperature of 800 ℃ and an annealing time of 4 hours to remove the organic ligand in the La/Fe-MOF precursor, thereby obtaining the LaFeO rich in oxygen vacancies 3 And (3) nanoparticles.
Step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and water 2 O 3 Ceramic tube and drying;
step S7: weighing 10mg of LaFeO rich in oxygen vacancy 3 Mixing the nano particles and ethanol in a mass ratio of 5:1, grinding into uniform slurry, and uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 A ceramic tube;
step S8: placing the device obtained in the step S7 in a 70 ℃ oven for 60min, and after the sensitive material is dried, passing a nickel-chromium alloy heating wire with the resistance value of 35 omega through Al with the sensitive material 2 O 3 A ceramic tube;
step S9: al with sensitive material is obtained in the step S8 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base, aging the prepared device at 300 ℃ for 3 days, thereby obtaining the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
Referring to FIG. 9, a process based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor has the highest sensitivity to formaldehyde gas and excellent selectivity, and the sensitivity to 100ppm of formaldehyde, acetone, methanol, ethanol, ammonia and carbon monoxide gas is at 160 ℃.
Example 4
See example 1 above and described further.
Step S1, adding 12mmol of lanthanum nitrate hexahydrate and 12mmol of ferric nitrate nonahydrate into 40ml of ethanol, and stirring for 1h at room temperature to obtain a uniform solution of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 14mmol of trimesic acid into 50ml of ethanol to obtain a uniform solution;
step S3: pouring the trimesic acid solution obtained in the step S2 into the mixed solution of lanthanum nitrate and ferric nitrate obtained in the step S1, and stirring for 10min at room temperature to obtain La/Fe-MOF gel;
step S4: drying the La/Fe-MOF gel obtained in the step S3 in a vacuum drying oven at 100 ℃ for 15 hours to obtain a La/Fe-MOF sample;
step S5: placing the La/Fe-MOF sample obtained in the step S4 in a tube furnace for annealing at a heating rate of 10 ℃/min, an annealing temperature of 900 ℃ and an annealing time of 4 hours to remove the organic ligand in the La/Fe-MOF precursor, thereby obtaining the LaFeO rich in oxygen vacancies 3 And (3) nanoparticles.
Step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and water 2 O 3 Ceramic tube and drying;
step S7: weighing 15mg of LaFeO rich in oxygen vacancy 3 Mixing the nano particles and ethanol in a mass ratio of 5:1, grinding into uniform slurry, and uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 A ceramic tube;
step S8: placing the device obtained in the step S7 in a 70 ℃ oven for 60min, and after the sensitive material is dried, passing a nickel-chromium alloy heating wire with the resistance value of 35 omega through Al with the sensitive material 2 O 3 A ceramic tube;
step S9: al with sensitive material is obtained in the step S8 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base, aging the prepared device for 4 days at 300 ℃ to obtain the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
Example 5
See example 1 above and described further.
Step S1, adding 14mmol of lanthanum nitrate hexahydrate and 14mmol of ferric nitrate nonahydrate into 40ml of ethanol, and stirring for 1h at room temperature to obtain a uniform solution of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 14mmol of trimesic acid into 50ml of ethanol to obtain a uniform solution;
step S3: pouring the trimesic acid solution obtained in the step S2 into the mixed solution of lanthanum nitrate and ferric nitrate obtained in the step S1, and stirring for 10min at room temperature to obtain La/Fe-MOF gel;
step S4: drying the La/Fe-MOF gel obtained in the step S3 in a vacuum drying oven at 100 ℃ for 18 hours to obtain a La/Fe-MOF sample;
step S5: placing the La/Fe-MOF sample obtained in the step S4 in a tube furnace for annealing at a heating rate of 10 ℃/min, an annealing temperature of 900 ℃ and an annealing time of 5 hours to remove the organic ligand in the La/Fe-MOF precursor, thereby obtaining the LaFeO rich in oxygen vacancies 3 And (3) nanoparticles.
Step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and water 2 O 3 Ceramic tube and drying;
step S7: weighing 15mg of LaFeO rich in oxygen vacancy 3 Mixing the nano particles and ethanol in a mass ratio of 5:1, grinding into uniform slurry, and uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 A ceramic tube;
step S8: placing the device obtained in the step S7 in an oven at 80 ℃ for 60min, and after the sensitive material is dried, passing a nichrome heating wire with the resistance value of 35 omega through Al with the sensitive material 2 O 3 A ceramic tube;
step S9: al with sensitive material is obtained in the step S8 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base, aging the prepared device for 4 days at 300 ℃ to obtain the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
Example 6
See example 1 above and described further.
Step S1, adding 14mmol of lanthanum nitrate hexahydrate and 14mmol of ferric nitrate nonahydrate into 40ml of ethanol, and stirring for 1h at room temperature to obtain a uniform solution of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 14mmol of trimesic acid into 50ml of ethanol to obtain a uniform solution;
step S3: pouring the trimesic acid solution obtained in the step S2 into the mixed solution of lanthanum nitrate and ferric nitrate obtained in the step S1, and stirring for 10min at room temperature to obtain La/Fe-MOF gel;
step S4: drying the La/Fe-MOF gel obtained in the step S3 in a vacuum drying oven at 100 ℃ for 18 hours to obtain a La/Fe-MOF sample;
step S5: placing the La/Fe-MOF sample obtained in the step S4 in a tube furnace for annealing at a heating rate of 10 ℃/min, an annealing temperature of 900 ℃ and an annealing time of 5 hours to remove the organic ligand in the La/Fe-MOF precursor, thereby obtaining the LaFeO rich in oxygen vacancies 3 And (3) nanoparticles.
Step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and water 2 O 3 Ceramic tube and drying;
step S7: weighing 15mg of LaFeO rich in oxygen vacancy 3 Mixing the nano particles and ethanol in a mass ratio of 5:1, grinding into uniform slurry, and uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 A ceramic tube;
step S8: placing the device obtained in the step S7 in an oven at 80 ℃ for 90min, and after the sensitive material is dried, passing a nichrome heating wire with a resistance value of 40 omega through Al with the sensitive material 2 O 3 A ceramic tube;
step S9: al with sensitive material is obtained in the step S8 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base, aging the prepared device at 350 ℃ for 5 days, thereby obtaining the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
The above description is only of the preferred embodiments of the present invention; the scope of the invention is not limited in this respect. Any person skilled in the art, within the technical scope of the present disclosure, may apply to the present invention, and the technical solution and the improvement thereof are all covered by the protection scope of the present invention.
Claims (10)
1. LaFeO based on oxygen-enriched vacancy 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor comprises the formaldehyde gas sensor and is characterized in that:
the formaldehyde gas sensor comprises Al 2 O 3 A ceramic tube substrate, the Al 2 O 3 A nickel-chromium alloy heating wire is fixedly arranged in the ceramic tube lining, and the Al is 2 O 3 A pair of annular gold electrodes are fixedly printed at two ends of the ceramic tube lining, and the Al is 2 O 3 The surface of the ceramic tube lining is uniformly coated with a gas sensitive film;
the gas sensitive film is derived to be rich in oxygen vacancy LaFeO by adopting MOF template method 3 Nanoparticles based on LaFeO rich in oxygen vacancies 3 The formaldehyde gas sensor prepared by the nano particles comprises the following specific steps:
step S1: adding 10-14 mmol of lanthanum nitrate hexahydrate and 10-14 mmol of ferric nitrate nonahydrate into 30-50 ml of ethanol, and stirring at room temperature for 0.5-2 h to obtain a uniform solution A of the lanthanum nitrate hexahydrate and the ferric nitrate nonahydrate;
step S2: dissolving 10-14 mmol of trimesic acid into 30-50 ml of ethanol to obtain trimesic acid ethanol solution;
step S3: pouring the mixed solution A prepared in the step S1 into the trimesic acid ethanol solution based on the step S2, and stirring for 2-10 min at room temperature to obtain La/Fe-MOF gel;
step S4: setting the La/Fe-MOF gel based on the step S3 in a vacuum drying oven at 60-100 ℃ and drying for 12-18 h to obtain a La/Fe-MOF sample;
step S5: based on the La/Fe-MOF sample of the step S4, placing the La/Fe-MOF sample in a tube furnace for annealing, controlling the heating rate to be 5-10 ℃/min, the annealing temperature to be 700-900 ℃ and the annealing time to be 3-5 h, removing the organic ligand in the La/Fe-MOF precursor, and obtaining the LaFeO rich in oxygen vacancies 3 A nanoparticle;
step S6: sequentially ultrasonically cleaning Al with a pair of gold electrodes and four platinum wires by using ethanol and pure water 2 O 3 Ceramic tube and drying;
step S7: based on step S5, weigh5-15 mg LaFeO rich in oxygen vacancy 3 Mixing nano particles and ethanol in a mass ratio of (4-6) 1, grinding into uniform slurry, uniformly coating the uniform slurry on Al with a pair of gold electrodes and four platinum wires 2 O 3 Forming an object B on the ceramic tube;
step S8: based on the object B in the step S7, placing the object B in an oven at 60-80 ℃ for 30-90 min, and after the sensitive material is dried, passing a nichrome heating wire with a resistance value of 30-40 omega through Al with the sensitive material 2 O 3 Ceramic tube, al with sensitive material is obtained 2 O 3 A ceramic tube;
step S9: al based on step S8 2 O 3 Ceramic tube, al 2 O 3 Welding two ends of four platinum wires and two ends of a nichrome heating wire of a ceramic tube on a hexagonal base to form an object C, and aging for 2-5 days at 250-350 ℃ to obtain the LaFeO based on oxygen-enriched vacancy 3 Nanoparticle formaldehyde gas sensor.
2. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S1, the ambient temperature range of the room temperature is controlled to be 15-25 ℃.
3. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S2, when trimesic acid is introduced into ethanol by adopting a paper tank holding mode, the mixed solution is slowly stirred.
4. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S3, the ambient temperature range of the room temperature is controlled to be 15-20 ℃.
5. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S4, a temperature and humidity sensor with the model number of HK2022011401 is adopted to monitor the humidity in the vacuum drying oven, and when the temperature value is less than 30% rh, drying is completed.
6. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S5, the temperature rise time is controlled to be 90-140 min.
7. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S6, when no obvious debris falls during ultrasonic cleaning, it is determined that ultrasonic cleaning is completed.
8. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S7, ethanol is added into LaFeO rich in oxygen vacancies when the slurry is mixed 3 In the nanoparticle, and stirring.
9. An oxygen-vacancy-enriched LaFeO-based catalyst according to claim 1 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S8, a temperature and humidity sensor with the model HK2022011401 is adopted to monitor the temperature and humidity in the vacuum drying oven, and the temperature value is determined to be less than 20%rh, so that the drying is determined to be completed.
10. A enrichment-based food according to claim 1Oxygen vacancy LaFeO 3 The preparation method of the nanoparticle high-performance formaldehyde gas sensor is characterized by comprising the following steps of:
in the step S9, the working humidity of the formaldehyde gas sensor is less than or equal to 90% rh, and the detection range of the formaldehyde gas sensor is 0-5000 ppm.
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