CN113390929B - Zinc oxide-based sensing gas-sensitive composite material and preparation method and application thereof - Google Patents

Zinc oxide-based sensing gas-sensitive composite material and preparation method and application thereof Download PDF

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CN113390929B
CN113390929B CN202110616781.7A CN202110616781A CN113390929B CN 113390929 B CN113390929 B CN 113390929B CN 202110616781 A CN202110616781 A CN 202110616781A CN 113390929 B CN113390929 B CN 113390929B
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向兰
罗仕睿
吕昕峰
杨帆
张灵军
黄著
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Abstract

The invention discloses a zinc oxide-based sensing gas-sensitive composite material and a preparation method and application thereof. The preparation method comprises the following steps: loading nano copper/silver particles on the surface of the zinc oxide nano cluster by a solution reduction method, and preparing the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by utilizing a nano copper/silver reduction effect; the zinc oxide-based sensing gas-sensitive composite material is formed by coating a zinc-containing ZIF layer on the surface of a zinc oxide composite material through in-situ growth and/or coating a microporous molecular sieve layer on the surface of the composite material by a coating method. The invention can realize the sensing detection of high sensitivity, quick response and high selectivity to methane, and provides a new way for methane sensing in the industries of coal mines, natural gas and the like.

Description

Zinc oxide-based sensing gas-sensitive composite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of new chemical materials, in particular to a zinc oxide-based sensing gas-sensitive composite material and a preparation method and application thereof.
Background
Methane (CH) 4 ) Is the main component of natural gas and coal mine gas, is also inflammable and explosive gas, and has an explosion limit of 5-15% in air. The key to guarantee the safe production of natural gas and coal mines is to monitor the methane concentration quickly and accurately. Methane sensors are mainly of three types, catalytic combustion, infrared and semiconductor oxide.
The catalytic combustion type methane sensor mainly uses a catalytic combustion type gas sensor, and the working principle is that methane combusts on the surface of a platinum catalyst in a flameless manner, so that the resistance of a platinum wire changes due to the rise of temperature. However, such sensors have problems: 1. the working temperature is higher (650-800 ℃), and the use danger is larger in inflammable and explosive atmosphere. 2. The stability is poor, the catalyst is easy to deposit carbon and deactivate, and the recalibration is needed in 7-14 days. 3. The selectivity is poor, and the catalyst responds to other reducing gases (such as carbon monoxide, hydrogen sulfide, sulfur dioxide and the like).
The infrared methane sensor mainly uses non-dispersive infrared (NDIR) and has the principle that methane molecules have characteristic absorption at a position of 3.2-3.45 mu m of a middle infrared band. The infrared sensing is sensitive and safe, the selectivity is good, but an infrared light source needs to be configured, the influence of dust and water vapor is large, the cost is high, and the large-scale application is limited.
The principle of the semiconductor oxide methane sensor is that the resistance changes before and after the sensor contacts methane. The oxide involved in the semiconductor oxide methane sensor is SnO 2 、ZnO、WO 3 、In 2 O 3 、NiO、TiO 2 And so on. Among various semiconductor oxides, ZnO is becoming a research and development hotspot due to the characteristics of low cost, easy performance control and the like. For example, Chinese application CN110117025A discloses a ZnO/Zn 2 SnO 4 A composite gas-sensitive material with heterogeneous structure is prepared from ZnO and Zn with hierarchical structure and prepared from sheets 2 SnO 4 The molar ratio of Sn to Zn is 10-50%; the method synthesizes ZnO/Zn with different doping ratios by controlling the molar ratio of Sn to Zn 2 SnO 4 The heterostructure composite gas sensitive material has good sensitivity to methane, and has wide application prospect in the aspect of manufacturing novel efficient methane gas sensors.
However, most of the currently reported work on methane sensing of zinc oxide-based materials focuses on detection of a single methane system, and less relates to methane selective detection under the condition of coexistence of multi-component gases.
Therefore, the research and development of the zinc oxide-based sensing material which can realize the high-sensitivity and quick response of methane and can realize the high-selectivity sensing detection of methane has very important practical significance.
Disclosure of Invention
The invention aims to provide a zinc oxide-based sensing gas-sensitive composite material, and a preparation method and application thereof, so as to realize high-sensitivity quick response and high-selectivity sensing detection of methane.
The above purpose of the invention is realized by the following technical scheme:
according to a first aspect of the invention, the invention provides a preparation method of a zinc oxide-based sensing gas-sensitive composite material, which comprises the following steps:
loading nano copper/silver particles on the surface of the zinc oxide nano agglomerate by adopting a solution reduction method to obtain the zinc oxide nano agglomerate loaded with the nano copper/silver particles;
carrying out nano copper/silver reduction effect on soluble palladium salt and the nano copper/silver particle-loaded zinc oxide nano agglomerates to prepare the palladium and nano copper/silver loaded zinc oxide composite material;
coating zinc-containing ZIF on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer; and/or the presence of a gas in the gas,
and coating a microporous molecular sieve on the surface of the zinc oxide-based sensing gas-sensitive composite material coated with the zinc ZIF layer/the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting a coating method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the microporous molecular sieve layer.
According to a second aspect of the invention, the zinc oxide-based sensing gas-sensitive composite material provided by the invention comprises zinc oxide nano agglomerates, nano copper/silver and nano palladium loaded on the zinc oxide nano agglomerates, and a zinc node imidazole ester framework structure (zinc-containing ZIF for short) and/or a microporous molecular sieve loaded on the surface. Further, the zinc oxide-based sensing gas-sensitive composite material is prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material.
According to a third aspect of the invention, the invention provides an application of a zinc oxide-based sensing gas-sensitive composite material in preparation of a methane sensing element, wherein the preparation of the methane sensing element comprises the following steps: and mixing the zinc oxide-based sensing gas-sensitive composite material with water, coating the mixture on a sensing element, and drying to prepare the methane sensing element. The sensing element is one of a ceramic tube, a ceramic wafer and a silicon wafer;
according to a fourth aspect of the present invention, the present invention provides an application of a zinc oxide-based sensing gas-sensitive composite material in gas sensing detection, comprising: preparing a methane sensing element by adopting a zinc oxide-based sensing gas-sensitive composite material; and (3) connecting the methane sensing element into a gas sensing detection system, and detecting the gas at the temperature of 200-400 ℃. The gas can be a mixture of methane and an impurity gas, and the impurity gas can be any one or a mixture of nitrogen dioxide, ammonia gas, sulfur dioxide, hydrogen sulfide, carbon monoxide and water vapor.
Compared with the prior art, the method can realize the sensing detection of methane with high sensitivity, quick response and high selectivity. The high-sensitivity rapid sensing of methane is realized by utilizing the synergistic catalytic effect of nano palladium/copper/silver particles; the high-selectivity sensing of methane is realized by utilizing the aperture blocking and polar adsorption effects of zinc-containing ZIF and/or microporous molecular sieves. The invention provides a new way for methane sensing in the industries of coal mines, natural gas and the like.
The characteristics and the prominent technical effects of the invention are embodied in the following aspects:
(1) in the preparation method, nano palladium/silver/copper particles are coated on the surfaces of the zinc oxide nano clusters by a solution method, and the high-sensitivity and rapid sensing of methane is realized by utilizing the synergistic catalytic effect of the nano palladium/copper/silver particles. Wherein, the sensor is based on zinc oxide nano-aggregates and has the characteristics of high activity, sensitive sensing, low price and the like.
(2) In the preparation method, the zinc-containing ZIF layer and/or the microporous molecular sieve layer are/is coated on the surface of the zinc oxide nano-agglomerates coated with the nano palladium/silver/copper particles by an in-situ growth and/or coating method, and the high-selectivity sensing of methane is realized by utilizing the aperture blocking effect and the polar adsorption effect of the zinc-containing ZIF and the microporous molecular sieve.
Wherein, the aperture blocking effect is as follows: pore diameter
Figure BDA0003096826500000031
The zinc-containing ZIF and microporous molecular sieve can block NO 2 (molecular diameter)
Figure BDA0003096826500000032
)、SO 2 (molecular diameter)
Figure BDA0003096826500000033
) And other molecules with diameters greater than
Figure BDA0003096826500000034
Gas of (C), CH 4 (molecular diameter)
Figure BDA0003096826500000035
) And O 2 (molecular diameter)
Figure BDA0003096826500000036
) It may pass.
Polar adsorption effect: with a nonpolar molecule CH 4 And O 2 By comparison, polar molecules CO (dipole moment 0.122D), NH 3 (dipole moment 1.47D), H 2 O (dipole moment 1.84D), H 2 The polar adsorption effect of S (dipole moment 1.20D) and the like with polar zinc-containing ZIF and the microporous molecular sieve is stronger, and the diffusion resistance is larger.
(3) The zinc oxide-based sensing gas-sensitive composite material obtained by the invention comprises zinc oxide nano agglomerates, nano palladium/copper/silver, a zinc node imidazole ester framework structure (zinc-containing ZIF for short) and/or a microporous molecular sieve, has the characteristics of quick response, high selectivity and the like during methane sensing detection, and provides a new way for methane sensing in the industries of coal mines, natural gas and the like.
(4) The zinc oxide-based sensing gas-sensitive composite material can realize the quick high-selection response of methane in the lower temperature range of 200-400 ℃, has very short sensing response time, and has the sensing response value of impurity gas far smaller than that of methane. Therefore, the methane sensing detection under the condition of multi-component gas coexistence can be realized by adopting the method.
For example, the sensing response time for 0.05-4% methane and 1-40ppm impurity gases (nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, carbon monoxide and water vapor) is less than 20 seconds, and the impurity gas sensing response value is not higher than 10% of the methane sensing response value, wherein the impurity gas sensing response value is not higher than 5% of the methane sensing response value in the preferred embodiment.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the preparation method of the zinc oxide-based sensing gas-sensitive composite material, firstly, nano metal particles are loaded on the surface of a zinc oxide nano cluster by a solution reduction method; then preparing a zinc oxide composite material simultaneously loaded with palladium and nano metal by utilizing a nano metal reduction effect; and then respectively coating a zinc-containing ZIF layer and/or a microporous molecular sieve layer on the surface of the zinc oxide composite material by an in-situ growth and/or coating method to form the zinc oxide-based sensing gas-sensitive composite material. The nano metal particles can be nano copper/silver particles.
The invention realizes the high-sensitivity and rapid sensing of methane by utilizing the synergistic catalytic effect of nano palladium/copper/silver particles, and realizes the high-selectivity sensing of methane by utilizing the aperture blocking and polar adsorption effects of zinc-containing ZIF and/or microporous molecular sieves.
In an alternative embodiment, the preparation method of the zinc oxide-based sensing gas-sensitive composite material provided by the invention can include: loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles; gathering soluble palladium salt and the zinc oxide nano-particles loaded with the nano-copper/silver particles, and preparing the zinc oxide composite material loaded with palladium and nano-copper/silver simultaneously by adopting a nano-copper/silver reduction effect; and coating a zinc-containing ZIF layer on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer.
Through detection, the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer has sensing detection effects of high sensitivity, quick response and high selectivity on methane. Further, in the embodiment, the high-sensitivity and rapid sensing of methane is realized through the synergistic catalytic effect of the nano palladium/copper/silver particles, and the high-selectivity sensing of methane is realized through the aperture blocking and polar adsorption effect of zinc-containing ZIF.
In an alternative embodiment, the preparation method of the zinc oxide-based sensing gas-sensitive composite material provided by the present invention may include: loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles; carrying out nano copper/silver reduction effect on soluble palladium salt and the nano copper/silver particle-loaded zinc oxide nano agglomerates to prepare the palladium and nano copper/silver loaded zinc oxide composite material; and coating a microporous molecular sieve on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting a coating method to prepare the first zinc oxide-based sensing gas-sensitive composite material (without a ZIF layer) coated with the microporous molecular sieve layer.
Through detection, the zinc oxide-based sensing gas-sensitive composite material coated with the microporous molecular sieve layer has sensing detection effects of high sensitivity, quick response and high selectivity on methane. Further, the embodiment realizes high-sensitivity and rapid sensing of methane through the synergistic catalytic effect of the nano palladium/copper/silver particles; the high-selectivity sensing of methane is realized through the aperture blocking and polar adsorption effects of the microporous molecular sieve.
In an alternative embodiment, the preparation method of the zinc oxide-based sensing gas-sensitive composite material provided by the invention can include: loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles; carrying out nano copper/silver reduction effect on soluble palladium salt and the nano copper/silver particle-loaded zinc oxide nano agglomerates to prepare the palladium and nano copper/silver loaded zinc oxide composite material; coating a zinc-containing ZIF layer on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer; and coating a microporous molecular sieve on the surface of the zinc oxide-based sensing gas-sensitive composite material coated with the zinc ZIF layer by adopting a coating method to prepare a second zinc oxide-based sensing gas-sensitive composite material coated with a microporous molecular sieve layer, wherein the second zinc oxide-based sensing gas-sensitive composite material is coated with the zinc ZIF layer firstly and then is coated with the microporous molecular sieve layer on the outer surface.
Through detection, the second zinc oxide-based sensing gas-sensitive composite material obtained in the embodiment has high-sensitivity quick-response and high-selectivity sensing detection effects on methane. Further, the embodiment realizes high-sensitivity and rapid sensing of methane through the synergistic catalytic effect of the nano palladium/copper/silver particles; the high-selectivity sensing of methane is realized through the aperture blocking and polar adsorption effects of the zinc-containing ZIF and the microporous molecular sieve, and the effect is better.
The invention also provides a zinc oxide-based sensing gas-sensitive composite material which can be prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material. Specifically, the zinc oxide-based sensing gas-sensitive composite material consists of zinc oxide nano agglomerates, nano copper/silver, nano palladium, a zinc node imidazole ester framework structure (zinc-containing ZIF for short) and/or a microporous molecular sieve.
The invention also provides application of the zinc oxide-based sensing gas-sensitive composite material in preparation of a methane sensing element. Wherein the preparation of the methane sensing element comprises: and mixing the zinc oxide-based sensing gas-sensitive composite material with water, coating the mixture on a sensing element, and drying to prepare the methane sensing element. The sensing element is one of a ceramic tube, a ceramic wafer and a silicon wafer.
The invention also provides an application of the zinc oxide-based sensing gas-sensitive composite material in methane sensing detection, which comprises the following steps: and (3) connecting the methane sensing element into a gas sensing detection system, and detecting the gas at the temperature of 200-400 ℃. Wherein the gas is a mixture of methane and an impurity gas, for example, a mixed gas of 0.05-4% methane and 1-40ppm impurity gas; the impurity gas is any one or a mixture of several of nitrogen dioxide, ammonia gas, sulfur dioxide, hydrogen sulfide, carbon monoxide and water vapor.
The following takes a preferred embodiment of coating a zinc-containing ZIF layer and a microporous molecular sieve layer as an example, and specifically describes a preparation method and application of the zinc oxide-based sensing gas-sensitive composite material.
Preparing a zinc oxide-based sensing gas-sensitive composite material and a methane sensing element:
(1) at the temperature of 25-120 ℃ and under the stirring condition, the stirring speed is 50-500 r/m, zinc oxide nano agglomerates with the agglomerate grain size of 100-2000 nm and soluble metal salt are added into a reducing agent solution containing a first dispersing agent, and the mass ratio of the zinc oxide nano agglomerates, the soluble metal salt, the first dispersing agent and the reducing agent is controlled to be 1: 0.1-1: 0.5-5: 50-500, reacting for 1-10 hours at constant temperature to obtain the zinc oxide nano cluster loaded with the metal nano particles. The whole reaction in this step is carried out under the stirring conditions described. Through detection, 0.1-5% of metal nano-particles are loaded in the zinc oxide nano-cluster loaded with the metal nano-particles, and the particle size of the metal nano-particles is 0.5-20 nm.
The zinc oxide nano-agglomerates are any one or a mixture of zinc oxide nano-particle agglomerates, zinc oxide nano-rod agglomerates and zinc oxide nano-sheet agglomerates. Wherein, the single nano-particle of the zinc oxide nano-particle cluster is 1-100 nm in primary particle diameter, the diameter of the single nano-rod in the zinc oxide nano-rod cluster is 1-100 nm, the length of the single nano-rod in the zinc oxide nano-rod cluster is 10-1000 nm, and the thickness of the single nano-plate in the zinc oxide nano-plate cluster is 1-100 nm.
The soluble metal salt is any one or a mixture of more of copper nitrate, copper chloride, copper sulfate, silver fluoride, silver nitrate and silver acetate.
The first dispersing agent is any one or a mixture of several of sodium dodecyl benzene sulfonate, cetyl trimethyl ammonium bromide and polyvinylpyrrolidone.
The reducing agent is any one or a mixture of ethanol, glycol and hydrazine hydrate.
(2) Adding the zinc oxide nano agglomerates loaded with the metal nano particles obtained in the step (1) and soluble palladium salt into an aqueous solution containing a second dispersing agent at the temperature of 25-100 ℃ and the stirring speed of 50-500 r/min, and controlling the mass ratio of zinc oxide to soluble palladium salt to the second dispersing agent to be 1: 0.001-0.02: 0.5-5: 50-500, reacting for 0.5-5 hours at constant temperature to obtain the zinc oxide composite material simultaneously loaded with the nano palladium and the nano metal particles. Wherein, 0.095 to 4.99 percent of nano metal is loaded, the grain diameter is 0.5 to 20 nanometers, 0.001 to 0.02 percent of nano palladium is loaded, and the grain diameter is 0.2 to 5 nanometers.
The soluble palladium salt is any one or a mixture of more of palladium nitrate, palladium chloride and palladium sulfate.
The second dispersing agent is any one or a mixture of several of sodium dodecyl sulfate, oleylamine and polyvinylpyrrolidone.
(3) Adding the zinc oxide nano-cluster composite material obtained in the step (2) and the imidazole organic ligand into a mixed solution of N, N-dimethylformamide and water at the temperature of 25-100 ℃ and at the stirring speed of 50-500 revolutions per minute, and controlling the mass ratio of the zinc oxide nano-cluster composite material to the imidazole organic ligand to the N, N-dimethylformamide to the water to be 1: 1-5: 100-500: 100-500, reacting at constant temperature for 4-48 hours, coating a layer of 10-100nm and aperture on the surface of the zinc oxide nano-cluster composite material by in-situ growth
Figure BDA0003096826500000081
The zinc-junction imidazole ester framework structure (zinc-containing ZIF for short) layer is adopted to obtain the zinc oxide-based sensing composite material coated with the zinc-containing ZIF. In the step, imidazole organic ligands are selected to be combined with zinc ions dissolved out of the surface of the zinc oxide, and the reaction time and the mass ratio are controlled at the same time, so that the zinc-containing ZIF layer with the thickness and the aperture is finally obtained.
The imidazole organic ligand is any one or a mixture of more of imidazole, 2-methylimidazole, 2-nitroimidazole, benzimidazole, 4, 5-dichloroimidazole, 6-nitrobenzimidazole and imidazole-2-formaldehyde.
(4) The zinc oxide based sensing composite material coated with zinc ZIF comprises: mixing the zinc ZIF-coated zinc oxide-based composite material obtained in the step (3) with water in a ratio of 1: 2-10 to form slurry, dipping the slurry by a brush, coating the slurry between the electrodes of the sensing element to form a gas-sensitive film layer with the thickness of 30-300 microns, and drying the gas-sensitive film layer for 8-24 hours at the temperature of 100-. Wherein, the sensing element refers to any one of a ceramic tube, a ceramic wafer and a silicon wafer.
(5) Coating a microporous molecular sieve layer: mixing microporous molecular sieve and water according to the ratio of 1: and 2-10, uniformly mixing to form slurry, dipping the slurry by using a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 30-300 microns on the surface of the gas-sensitive film layer, and drying at the temperature of 100-200 ℃ for 8-24 hours to obtain the methane sensing element.
In the methane sensing element obtained in the step, the surface of the ceramic tube, the ceramic plate or the silicon wafer sensing element is formed to form the second zinc oxide-based sensing gas-sensitive composite material, and the outer surface of the zinc-containing ZIF layer is also coated with a microporous molecular sieve layer.
Wherein the microporous molecular sieve refers to any one or a mixture of more of 4A molecular sieve, SAPO-39, SAPO-42 and AlPO-22.
Sensing and detecting gas:
(6) and (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of the methane and the impurity gas at the temperature of 200-400 ℃.
The impurity gas is any one or a mixture of several of nitrogen dioxide, ammonia gas, sulfur dioxide, hydrogen sulfide, carbon monoxide and water vapor.
The results show that: in the range of 0.05-4% of methane concentration and 1-40ppm of impurity gas concentration, the sensing response time (the time required for the resistance change to reach 90%) of the methane sensing element to methane and impurity gas is less than 20 seconds, and the sensing response value of impurity gas is only less than 5% of the sensing response value of methane.
Therefore, the zinc oxide-based methane sensing gas-sensitive composite material prepared by the invention has the characteristics of quick response, high selectivity and the like in methane sensing detection application, and provides a new way for methane sensing in industries such as coal mines, natural gas and the like.
The present invention will be further described with reference to specific examples, which are intended to illustrate only some of the embodiments of the present invention, but not all of them. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
The zinc oxide-based sensing gas-sensitive composite materials in examples 1 to 6 were coated with a zinc-containing ZIF layer and a microporous molecular sieve layer; example 7 is a non-microporous molecular sieve, example 8 is a non-zinc containing ZIF layer, and comparative example 1 is a non-filter layer, i.e., a non-zinc containing ZIF layer and a non-microporous molecular sieve.
Example 1 (zinc containing ZIF layer and microporous molecular sieve layer)
(1) Adding zinc oxide nano-particle aggregates (primary particle size of 1 nanometer) with the aggregate particle size of 100 nanometers and copper nitrate into an ethanol solution containing sodium dodecyl benzene sulfonate under the condition of stirring (50 revolutions per minute) at 25 ℃, and controlling the mass ratio of the zinc oxide nano-particle aggregates to the copper nitrate to the sodium dodecyl benzene sulfonate to be 1: 0.1: 0.5: 50, reacting for 1 hour at constant temperature to obtain zinc oxide nano agglomerates loaded with 0.1 percent of copper nano particles (the particle size is 0.5 nm).
(2) Adding the copper nanoparticle-loaded zinc oxide nano agglomerates and palladium nitrate into an aqueous solution containing sodium dodecyl sulfate at 25 ℃ under the condition of stirring (50 revolutions per minute), and controlling the mass ratio of the zinc oxide nano agglomerates, the palladium nitrate, the sodium dodecyl sulfate and the water to be 1: 0.001: 0.5: 50, reacting at constant temperature for 0.5 hour to obtain the zinc oxide nano-agglomeration composite material loaded with 0.099 percent of nano-copper (with the grain diameter of 0.5 nm) and 0.001 percent of nano-palladium (with the grain diameter of 0.2 nm).
(3) Adding the zinc oxide nanoparticle agglomerated composite material coated with the nano copper/palladium and imidazole into a mixed solution of N, N-dimethylformamide and water at the temperature of 25 ℃ and at the stirring speed of 50 revolutions per minute, and controlling the mass ratio of the zinc oxide nanoparticle agglomerated composite material to the imidazole to the N, N-dimethylformamide to the water to be 1: 1:100: 100, reacting at constant temperature for 4 hours, and coating the surface of the zinc oxide nanoparticle agglomeration composite material with a layer with thickness of 10nm and aperture by in-situ growth
Figure BDA0003096826500000101
And obtaining the zinc oxide nanoparticle agglomerated composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nano-agglomerate composite material coated with zinc ZIF and water in a proportion of 1:2 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic tube) to form a gas-sensitive film layer with the thickness of 30 microns, and drying for 8 hours at 100 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) Mixing a 4A molecular sieve with water according to the weight ratio of 1:2 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 30 microns on the surface of the gas-sensitive film layer, and drying for 8 hours at 100 ℃ to obtain the methane sensing element.
(6) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane and nitrogen dioxide at 200 ℃. The gas sensing test system adopted by each embodiment of the invention can be a CGS-8 gas-sensitive test system; the test method comprises the following steps: the sensing element is fixed in a constant volume gas cavity, quantitative test gas is injected into the constant volume gas cavity through a gas sampling needle to obtain the concentration to be measured, the sensing system can record the resistance change of the sensing element, and information such as a response value and response time is obtained according to the resistance change.
The results show that: under the conditions that the methane concentration is 0.05% and the nitrogen dioxide concentration is 1ppm, the sensing response time of the methane sensing element to methane and nitrogen dioxide is 15 seconds and 16 seconds respectively, and the sensing response value of nitrogen dioxide is only 1% of the sensing response value of methane.
Example 2 (Zinc containing ZIF layer and microporous molecular sieve layer)
(1) Adding zinc oxide nano-particle aggregates (with a primary particle size of 100 nanometers) with an aggregate particle size of 2000 nanometers and copper chloride into ethylene glycol solution containing cetyl trimethyl ammonium bromide under the conditions of stirring (50 revolutions per minute) at 120 ℃, and controlling the mass ratio of the zinc oxide nano-particle aggregates, the copper chloride, the cetyl trimethyl ammonium bromide and the ethylene glycol to be 1: 1: 5: 500, reacting for 10 hours at constant temperature to obtain zinc oxide nano agglomerates loaded with 5 percent of copper nano particles (the particle size is 20 nanometers).
(2) Adding the zinc oxide nano agglomerates loaded with the copper nano particles and palladium chloride into an aqueous solution containing oleylamine under the conditions of stirring (500 revolutions per minute) at 100 ℃, and controlling the mass ratio of the zinc oxide to the palladium chloride to the oleylamine to be 1: 0.02: 5: and 500, reacting at constant temperature for 5 hours to obtain the zinc oxide nano-agglomeration composite material loaded with 4.98 percent of nano copper (with the grain diameter of 20 nanometers) and 0.02 percent of nano palladium (with the grain diameter of 5 nanometers).
(3) Adding the zinc oxide nanoparticle agglomerate composite material coated with the nano copper/palladium and 2-methylimidazole into a mixed solution of N, N-dimethylformamide and water at the temperature of 100 ℃ and the stirring speed of 500 revolutions per minute, and controlling the mass ratio of the zinc oxide nanoparticle agglomerate composite material to the 4, 5-dichloroimidazole to the N, N-dimethylformamide to the water to be 1: 5: 500: 500, reacting at constant temperature for 48 hours, and coating the surface of the zinc oxide nanoparticle agglomeration composite material with a layer with thickness of 100nm and aperture by in-situ growth
Figure BDA0003096826500000111
And obtaining the zinc oxide nanoparticle agglomerated composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nano-agglomerate composite material coated with zinc ZIF and water in a proportion of 1:10 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 300 microns, and drying the gas-sensitive film layer for 24 hours at 200 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) SAPO-39 and water are mixed according to a weight ratio of 1:10 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 300 microns on the surface of the gas-sensitive film layer, and drying for 24 hours at 200 ℃ to obtain the methane sensing element.
(6) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane and ammonia gas at 400 ℃.
The results show that: under the conditions of 4% of methane concentration and 40ppm of ammonia gas concentration, the sensing response time of the methane sensing element to methane and ammonia gas is 2 seconds and 3 seconds respectively, and the sensing response value of ammonia gas is only 5% of the sensing response value of methane.
Example 3 (Zinc containing ZIF layer and microporous molecular sieve layer)
(1) Adding zinc oxide nanorod clusters (the diameter is 1 nanometer, the length is 10 nanometers) with the aggregate grain diameter of 200 nanometers, zinc oxide nanosheet clusters (the diameter is 10 nanometers, the thickness is 1 nanometer) with the aggregate grain diameter of 800 nanometers and copper sulfate into a hydrazine hydrate solution containing polyvinylpyrrolidone under the conditions of stirring (250 revolutions per minute) at the temperature of 80 ℃, and controlling the mass ratio of the zinc oxide nanorod clusters (the mass ratio of the nanosheets to the nanorods is 1:10), the copper nitrate, the polyvinylpyrrolidone and the hydrazine hydrate to be 1: 0.5: 1: 250, reacting at constant temperature for 5 hours to obtain zinc oxide nano agglomerates loaded with 2 percent of copper nano particles (the particle size is 5 nanometers).
(2) Adding the copper nanoparticle-loaded zinc oxide nano agglomerates and palladium sulfate into an aqueous solution containing oleylamine under the conditions of 55 ℃ and stirring (350 revolutions per minute), and controlling the mass ratio of the zinc oxide nano agglomerates, palladium nitrate, oleylamine and water to be 1: 0.01: 2: 150, reacting at constant temperature for 2.5 hours to obtain the zinc oxide nano-agglomeration composite material loaded with 1.99 percent of nano copper (with the grain diameter of 5 nanometers) and 0.01 percent of nano palladium (with the grain diameter of 1 nanometer).
(3) Adding the zinc oxide nano-cluster composite material coated with nano-copper/palladium and 2-nitroimidazole into a mixed solution of N, N-dimethylformamide and water at the temperature of 45 ℃ and the stirring speed of 150 revolutions per minute, and controlling the mass ratio of the zinc oxide nano-cluster composite material, the 2-nitroimidazole, the N, N-dimethylformamide and the water to be 1:2: 200: 300, reacting at constant temperature for 24 hours, and coating the surface of the zinc oxide nanoparticle agglomeration composite material with a layer with thickness of 50nm and aperture by in-situ growth
Figure BDA0003096826500000121
And obtaining the zinc oxide nano-cluster composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nano-agglomeration composite material coated with zinc ZIF and water in a proportion of 1:4 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (silicon wafer) to form a gas-sensitive film layer with the thickness of 200 microns, and drying for 10 hours at 150 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) SAPO-42 and water are mixed according to a ratio of 1: 6 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 100 microns on the surface of the gas-sensitive film layer, and drying for 12 hours at 120 ℃ to obtain the methane sensing element.
(6) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane and sulfur dioxide at 300 ℃.
The results show that: under the conditions of 1% of methane concentration and 20ppm of sulfur dioxide concentration, the sensing response time of the methane sensing element to methane and impurity gas is 3 seconds and 6 seconds respectively, and the sensing response value of the sulfur dioxide is only 2% of that of the methane.
Example 4 (Zinc containing ZIF layer and microporous molecular sieve layer)
(1) Under the condition of stirring at 70 ℃ and (400 revolutions per minute), adding zinc oxide nano-particle clusters (with a primary particle diameter of 10 nanometers) with an aggregate particle diameter of 500 nanometers, zinc oxide nano-rod clusters (with a diameter of 100 nanometers and a length of 1000 nanometers) with an aggregate particle diameter of 1500 nanometers, zinc oxide nano-sheet clusters (with a diameter of 1000 nanometers and a thickness of 100 nanometers) with an aggregate particle diameter of 500 nanometers and silver fluoride into ethylene glycol solution containing hexadecyl trimethyl ammonium bromide, controlling the mass ratio of the zinc oxide nano-clusters (consisting of nano-particles, nano-rods and nano-sheets to be 1:100:10), the silver fluoride, the hexadecyl trimethyl ammonium bromide and the ethylene glycol to be 1: 0.4: 3: 200, reacting for 3 hours at constant temperature to obtain zinc oxide nano agglomerates loaded with 2% silver nano particles (the particle size is 6 nanometers).
(2) Adding the silver nanoparticle-loaded zinc oxide nano aggregates and soluble palladium salt (composed of palladium nitrate and palladium chloride in a mass ratio of 5:1) into an aqueous solution containing sodium dodecyl sulfate at 75 ℃ under stirring (150 rpm), and controlling the mass ratio of the zinc oxide nano aggregates to the soluble palladium salt to the sodium dodecyl sulfate to be 1: 0.01: 4: 400, reacting at constant temperature for 3 hours to obtain the zinc oxide nano agglomerate composite material loaded with 1.992 percent of nano silver (with the grain diameter of 6 nanometers) and 0.008 percent of nano palladium (with the grain diameter of 3 nanometers).
(3) Adding the nano-silver/palladium-coated zinc oxide nano-micelle composite material and imidazole organic ligand (consisting of benzimidazole, 4, 5-dichloroimidazole and 6-nitrobenzimidazole in a mass ratio of 1:2:5) into a mixed solution of N, N-dimethylformamide and water at the temperature of 85 ℃ and at the stirring speed of 220 r/min, and controlling the mass ratio of the nano-silver/palladium-coated zinc oxide nano-micelle composite material to the imidazole organic ligand to be 1: 4: 200: 300, reacting at constant temperature for 12 hours, and coating the surface of the zinc oxide nano-cluster composite material with a layer of thickness of 50nm and aperture by in-situ growth
Figure BDA0003096826500000131
And obtaining the zinc oxide nano-cluster composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nano-agglomeration composite material coated with zinc ZIF and water in a proportion of 1: 8 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic tube) to form a gas-sensitive film layer with the thickness of 120 microns, and drying the gas-sensitive film layer for 20 hours at 160 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) Mixing a microporous molecular sieve (consisting of a 4A molecular sieve, SAPO-42 and AlPO-22 in a mass ratio of 1:3:6) and water according to a ratio of 1: 7 to form slurry, dipping the slurry by using a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 160 microns on the surface of the gas-sensitive film layer, and drying for 8 hours at 150 ℃ to obtain the methane sensing element.
(6) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane, nitrogen dioxide, hydrogen sulfide, carbon monoxide and water vapor at 350 ℃.
The results show that: under the conditions of 0.1% of methane concentration, 5ppm of nitrogen dioxide concentration, 6ppm of hydrogen sulfide concentration, 30ppm of carbon monoxide concentration and 38ppm of water vapor concentration, the sensing response time of the methane sensing element to methane, nitrogen dioxide, hydrogen sulfide, carbon monoxide and water vapor is respectively 5 seconds, 6 seconds, 10 seconds, 8 seconds and 20 seconds, and the sensing response values of the nitrogen dioxide, the hydrogen sulfide, the carbon monoxide and the water vapor are only 2%, 1%, 0.5% and 0.8% of the sensing response value of the methane respectively.
Example 5 (Zinc containing ZIF layer and microporous molecular sieve layer)
(1) Under the condition of stirring at 70 ℃ and 200 revolutions per minute (200 revolutions per minute), adding a reducing agent (comprising ethanol and glycol in a mass ratio of 1:4) solution containing a dispersing agent 1 (comprising sodium dodecyl benzene sulfonate and hexadecyl trimethyl ammonium bromide in a mass ratio of 10:1) into a zinc oxide nanorod aggregation (with the diameter of 30 nanometers and the length of 200 nanometers) and a soluble silver salt (comprising silver nitrate and silver acetate in a mass ratio of 5:3) with the aggregation grain diameter of 1000 nanometers, and controlling the mass ratio of the zinc oxide nanorod aggregation, the soluble silver salt, the dispersing agent 1 and the reducing agent to be 1: 0.4: 2: 450, reacting for 6 hours at constant temperature to obtain the zinc oxide nanorod agglomerates loaded with 2.2% silver nanoparticles (with the particle size of 10 nanometers).
(2) Adding the silver nanoparticle-loaded zinc oxide nanorod clusters and palladium sulfate into an aqueous solution containing a dispersing agent 2 (composed of sodium dodecyl sulfate and polyvinylpyrrolidone in a mass ratio of 1:5) at 65 ℃ under the condition of stirring (350 r/m), and controlling the mass ratio of the zinc oxide nanorod clusters to the palladium sulfate to the dispersing agent 2 to water to be 1: 0.01: 4: 400, reacting at constant temperature for 3 hours to obtain the zinc oxide nano-agglomeration composite material loaded with 1.99 percent of nano silver (with the grain diameter of 10 nanometers) and 0.01 percent of nano palladium (with the grain diameter of 2.5 nanometers).
(3) Adding the zinc oxide nanorod aggregation composite material coated with nano silver/palladium and imidazole-2-formaldehyde into a mixed solution of N, N-dimethylformamide and water at 75 ℃ and at a stirring speed of 260 revolutions per minute, and controlling the mass ratio of the zinc oxide nanorod aggregation composite material, the imidazole-2-formaldehyde, the N, N-dimethylformamide and the water to be 1:2: 250: 450, reacting at constant temperature for 16 hours, and coating the surface of the zinc oxide nano-cluster composite material with a layer thickness of 200nm and a pore diameter by in-situ growth
Figure BDA0003096826500000151
And obtaining the zinc oxide nanorod aggregation composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nanorod aggregation composite material coated with the zinc ZIF with water in a proportion of 1:3 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 260 microns, and drying for 10 hours at 180 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) Mixing a microporous molecular sieve (consisting of a 4A molecular sieve and SAPO-39 in a mass ratio of 1:4) and water according to a ratio of 1:5 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 60 microns on the surface of the gas-sensitive film layer, and drying for 24 hours at 140 ℃ to obtain the methane sensing element.
(6) And (4) connecting the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane, nitrogen dioxide, ammonia gas and sulfur dioxide at 350 ℃.
The results show that: under the conditions of 1.5% of methane concentration, 20ppm of nitrogen dioxide concentration, 25ppm of ammonia gas concentration and 38ppm of sulfur dioxide concentration, the sensing response time of the methane sensing element to methane, nitrogen dioxide, ammonia gas and sulfur dioxide is respectively 2 seconds, 4 seconds, 3 seconds and 10 seconds, and the sensing response values of the nitrogen dioxide, the ammonia gas and the sulfur dioxide are only 3%, 2% and 2.5% of the sensing response value of the methane respectively.
Example 6 (zinc containing ZIF layer and microporous molecular sieve layer)
(1) Under the condition of stirring (250 revolutions per minute) at 60 ℃, adding a glycol solution containing a dispersing agent 1 (comprising sodium dodecyl benzene sulfonate, hexadecyl trimethyl ammonium bromide and polyvinylpyrrolidone in a mass ratio of 9:6:1) into a zinc oxide nano sheet cluster (with the diameter of 300 nanometers and the thickness of 200 nanometers) and a soluble copper salt (comprising copper nitrate, copper chloride and copper sulfate in a mass ratio of 5:1:2) with the cluster particle size of 800 nanometers, and controlling the mass ratio of the zinc oxide nano sheet cluster, the soluble copper salt, the dispersing agent 1 and the glycol to be 1: 0.3: 3: 400, reacting at constant temperature for 5 hours to obtain zinc oxide nano-sheet agglomerates loaded with 3 percent of copper nano-particles (the particle size is 10 nanometers).
(2) Adding the copper nanoparticle-loaded zinc oxide nano-sheet agglomerates and soluble palladium salt (composed of palladium nitrate, palladium chloride and palladium sulfate in a mass ratio of 8:4:1) into a polyvinylpyrrolidone-containing aqueous solution at the temperature of 55 ℃ and under stirring (250 revolutions per minute), and controlling the mass ratio of the zinc oxide nano-rod agglomerates, the soluble palladium salt, the polyvinylpyrrolidone and water to be 1: 0.02: 3: and 500, reacting at constant temperature for 3 hours to obtain the zinc oxide nano-agglomeration composite material loaded with 1.98 percent of nano copper (with the grain diameter of 10 nanometers) and 0.02 percent of nano palladium (with the grain diameter of 2.5 nanometers).
(3) Adding the zinc oxide nanorod aggregation composite material coated with the nano copper/palladium and an imidazole organic ligand (consisting of imidazole, 2-methylimidazole and 6-nitrobenzimidazole in a mass ratio of 2:3:5) into a mixed solution of N, N-dimethylformamide and water at 65 ℃ and at a stirring speed of 240 revolutions per minute, and controlling the mass ratio of the zinc oxide nanorod aggregation composite material, the imidazole organic ligand, the N, N-dimethylformamide and the water to be 1: 1.5: 200: 400, reacting at constant temperature for 20 hours, and coating the surface of the zinc oxide nano-cluster composite material with a layer of thickness of 150nm and aperture by in-situ growth
Figure BDA0003096826500000161
And obtaining the zinc oxide nanosheet agglomeration composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nanosheet agglomeration composite material coated with the zinc ZIF and water in a proportion of 1:2 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 240 microns, and drying at 150 ℃ for 12 hours to obtain the sensing element with the gas-sensitive film layer.
(5) Mixing AlPO-22 and water according to the proportion of 1:5 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 90 microns on the surface of the gas-sensitive film layer, and drying for 16 hours at 160 ℃ to obtain the methane sensing element.
(6) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane, nitrogen dioxide, ammonia gas and sulfur dioxide at 300 ℃.
The results show that: under the conditions of 2% of methane concentration and 40ppm of impurity gas concentration (wherein the water vapor concentration is 20ppm, the carbon monoxide concentration is 10ppm and the hydrogen sulfide concentration is 10ppm), the sensing response time of the methane sensing element to methane and the impurity gas is respectively 6 seconds and 4 seconds, and the sensing response value of the impurity gas is only 2.5% of the sensing response value of methane respectively.
Example 7 (non-microporous molecular sieve layer)
(1) Adding zinc oxide nanorod aggregates (with the diameter of 30 nanometers and the length of 200 nanometers) with the aggregate particle size of 1000 nanometers and silver nitrate into ethylene glycol solution containing sodium dodecyl sulfate under the conditions of stirring (200 revolutions per minute) at 80 ℃, and controlling the mass ratio of the zinc oxide nanorod aggregates, the silver nitrate, the sodium dodecyl sulfate and the ethylene glycol to be 1: 0.4: 2: 450, reacting for 7 hours at constant temperature to obtain the zinc oxide nanorod agglomerates loaded with 2.2% silver nanoparticles (with the particle size of 10 nanometers).
(2) Adding the silver nanoparticle-loaded zinc oxide nanorod agglomerates and palladium sulfate into an aqueous solution containing sodium dodecyl sulfate under the conditions of stirring (200 revolutions per minute) at 50 ℃, and controlling the mass ratio of the zinc oxide nanorod agglomerates, the palladium sulfate, the sodium dodecyl sulfate and the water to be 1: 0.01: 4: 400, reacting at constant temperature for 3 hours to obtain the zinc oxide nano-agglomeration composite material loaded with 1.99 percent of nano silver (with the grain diameter of 10 nanometers) and 0.01 percent of nano palladium (with the grain diameter of 2.5 nanometers).
(3) Adding the zinc oxide nanorod aggregation composite material coated with nano silver/palladium and imidazole-2-formaldehyde into a mixed solution of N, N-dimethylformamide and water at 65 ℃ and at a stirring speed of 200 revolutions per minute, and controlling the mass ratio of the zinc oxide nanorod aggregation composite material, the imidazole-2-formaldehyde, the N, N-dimethylformamide and the water to be 1:2: 250: 450, reacting at constant temperature for 8 hours, and coating the surface of the zinc oxide nano agglomerate composite material with a layer with thickness of 50nm and aperture by in-situ growth
Figure BDA0003096826500000171
And obtaining the zinc oxide nanorod aggregation composite material coated with the zinc ZIF.
(4) Mixing the zinc oxide nanorod aggregation composite material coated with the zinc ZIF with water in a proportion of 1:3 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 260 microns, and drying for 10 hours at 180 ℃ to obtain the sensing element with the gas-sensitive film layer.
(5) And (5) connecting the sensing element obtained in the step (4) into a gas sensing test system, and detecting the sensing performance of methane, nitrogen dioxide, ammonia gas and sulfur dioxide at 350 ℃.
The results show that: under the condition that the methane concentration is 1.5%, the nitrogen dioxide concentration is 25ppm, the ammonia gas concentration is 25ppm and the sulfur dioxide concentration is 40ppm, the sensing response time of the methane sensing element to methane, nitrogen dioxide, ammonia gas and sulfur dioxide is 1.5 seconds, 2.5 seconds, 4 seconds and 7 seconds respectively, and the sensing response values of the nitrogen dioxide, the ammonia gas and the sulfur dioxide are only 7%, 6% and 5.5% of the sensing response value of the methane respectively.
Example 8 (No Zinc containing ZIF layer)
(7) Adding zinc oxide nanorod aggregates (with the diameter of 30 nanometers and the length of 300 nanometers) and soluble silver salt (composed of silver nitrate and silver acetate in a mass ratio of 1:1) with the aggregate particle size of 1000 nanometers into an ethylene glycol solution containing sodium dodecyl benzene sulfonate under the condition of stirring (250 revolutions per minute) at 75 ℃, and controlling the mass ratio of the zinc oxide nanorod aggregates, the soluble silver salt, the sodium dodecyl benzene sulfonate and the ethylene glycol to be 1: 0.3: 3: 550, reacting for 7 hours at constant temperature to obtain the zinc oxide nanorod agglomerates loaded with 2.2% silver nanoparticles (with the particle size of 10 nanometers).
(8) Adding the silver nanoparticle-loaded zinc oxide nanorod agglomerates and palladium sulfate into a polyvinylpyrrolidone-containing aqueous solution under the conditions of stirring (250 revolutions per minute) at 55 ℃, and controlling the mass ratio of the zinc oxide nanorod agglomerates, the palladium sulfate, the polyvinylpyrrolidone and the water to be 1: 0.015: 5: 500, reacting for 4 hours at constant temperature to obtain the zinc oxide nano-agglomeration composite material loaded with 2.19 percent of nano silver (with the grain diameter of 10 nanometers) and 0.01 percent of nano palladium (with the grain diameter of 2.5 nanometers).
(9) Mixing the zinc oxide nanorod aggregation composite material with water in a proportion of 1:3 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 200 microns, and drying for 10 hours at 150 ℃ to obtain the sensing element with the gas-sensitive film layer.
(10) Mixing a microporous molecular sieve (consisting of a 4A molecular sieve and SAPO-39 in a mass ratio of 1:1) and water according to a ratio of 1:5 to form slurry, dipping the slurry by a brush, coating the slurry on the sensing element with the gas-sensitive film layer obtained in the step (4), forming a microporous molecular sieve layer with the thickness of 60 microns on the surface of the gas-sensitive film layer, and drying for 24 hours at 120 ℃ to obtain the methane sensing element.
(11) And (4) accessing the methane sensing element obtained in the step (5) into a gas sensing test system, and detecting the sensing performance of methane, carbon monoxide, ammonia gas and sulfur dioxide at 350 ℃.
The results show that: under the condition that the methane concentration is 1.5%, the carbon monoxide concentration is 10ppm, the ammonia concentration is 20ppm and the sulfur dioxide concentration is 30ppm, the sensing response time of the methane sensing element to methane, carbon monoxide, ammonia and sulfur dioxide is respectively 4 seconds, 8 seconds, 6 seconds and 12 seconds, and the sensing response value of the carbon monoxide, the ammonia and the sulfur dioxide is only 6%, 10% and 8% of the sensing response value of the methane.
Comparative example 1 (non-microporous molecular sieve layer, non-zinc containing ZIF layer)
(1) Adding zinc oxide nano-sheet aggregates (with the diameter of 200 nanometers and the thickness of 50 nanometers) with the aggregate particle size of 700 nanometers and soluble copper salt (copper nitrate and copper chloride in a mass ratio of 1:1) into ethylene glycol solution containing cetyl trimethyl ammonium bromide under the condition of stirring (250 revolutions per minute) at the temperature of 60 ℃, and controlling the mass ratio of the zinc oxide nano-sheet aggregates, the soluble copper salt, the cetyl trimethyl ammonium bromide and the ethylene glycol to be 1: 0.2: 3: 350, reacting for 6 hours at constant temperature to obtain zinc oxide nano-sheet agglomerates loaded with 2.5 percent of copper nano-particles (the particle size is 10 nanometers).
(7) Adding the copper nanoparticle-loaded zinc oxide nanosheet agglomerates and palladium chloride into a polyvinylpyrrolidone-containing aqueous solution at 60 ℃ under stirring (250 revolutions per minute), and controlling the mass ratio of the zinc oxide nanosheet agglomerates, the palladium chloride, the polyvinylpyrrolidone and the water to be 1: 0.015: 3: 450, reacting for 3 hours at constant temperature to obtain the zinc oxide nano-agglomeration composite material loaded with 2.48 percent of nano-copper (with the grain diameter of 10 nanometers) and 0.02 percent of nano-palladium (with the grain diameter of 2.5 nanometers).
(8) Mixing the zinc oxide nano-sheet agglomeration composite material with water in a proportion of 1:2 to form slurry, dipping the slurry by a brush, coating the slurry between electrodes of the sensing element (ceramic wafer) to form a gas-sensitive film layer with the thickness of 140 microns, and drying at 130 ℃ for 12 hours to obtain the sensing element with the gas-sensitive film layer.
(9) And (4) connecting the methane sensing element obtained in the step (3) into a gas sensing test system, and detecting the sensing performance of methane, carbon monoxide, nitrogen dioxide and ammonia gas at 300 ℃.
The results show that: under the conditions of 2% of methane concentration and 40ppm of impurity gas concentration (wherein the concentration of carbon monoxide is 20ppm, the concentration of nitrogen dioxide is 10ppm and the concentration of ammonia is 10ppm), the sensing response time of the methane sensing element to methane and impurity gas is respectively 3 seconds and 2 seconds, and the sensing response value of the impurity gas is 125% of the sensing response value of methane.
In summary, compared with comparative example 1, examples 1 to 8 of the present invention have high selectivity to methane, wherein, in examples 1 to 8, the sensing response value of other impurity gases is not higher than 10% of the sensing response value of methane; in examples 1 to 6, the impurity gas sensing response value was not higher than 5% or less of the methane sensing response value.
The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to practitioners skilled in this art. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims (14)

1. A preparation method of a zinc oxide-based sensing gas-sensitive composite material is characterized by comprising the following steps:
loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles;
preparing a zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting soluble palladium salt and the nano zinc oxide cluster loaded with nano copper/silver particles through a nano copper/silver reduction effect;
and coating zinc-containing ZIF on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer.
2. A preparation method of a zinc oxide-based sensing gas-sensitive composite material is characterized by comprising the following steps:
loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles;
preparing a zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting soluble palladium salt and the nano zinc oxide cluster loaded with nano copper/silver particles through a nano copper/silver reduction effect;
and coating a microporous molecular sieve on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting a coating method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the microporous molecular sieve layer.
3. A preparation method of a zinc oxide-based sensing gas-sensitive composite material is characterized by comprising the following steps:
loading nano copper/silver particles on the surface of the zinc oxide nano cluster by adopting a solution reduction method to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles;
preparing a zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting soluble palladium salt and the nano zinc oxide cluster loaded with nano copper/silver particles through a nano copper/silver reduction effect;
coating zinc-containing ZIF on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by adopting an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer;
and coating a microporous molecular sieve on the surface of the zinc oxide-based sensing gas-sensitive composite material coated with the zinc ZIF layer by adopting a coating method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the microporous molecular sieve layer.
4. The preparation method according to any one of claims 1 to 3, wherein the step of obtaining the nano-copper/silver particle-loaded zinc oxide nanoclusters by loading nano-copper/silver particles on the surface of the zinc oxide nanoclusters by a solution reduction method comprises:
adding zinc oxide nano-agglomerates and soluble metal copper salt/silver salt into a reducing agent solution containing a first dispersing agent; controlling the mass ratio of the zinc oxide nano agglomerates, the soluble metal copper salt/silver salt, the first dispersing agent and the reducing agent to be 1: (0.1-1): (0.5-5): (50-500) reacting for 1-10 hours to obtain the zinc oxide nano cluster loaded with the nano copper/silver particles.
5. The production method according to claim 4,
the zinc oxide nano agglomerates are any one or a mixture of more of zinc oxide nano particle agglomerates, zinc oxide nano rod agglomerates and zinc oxide nano sheet agglomerates; the diameter of a single nanorod in the zinc oxide nanorod aggregation is 1-100 nanometers, the length of the single nanorod in the zinc oxide nanorod aggregation is 10-1000 nanometers, and the diameter of a single nanosheet in the zinc oxide nanosheet aggregation is 10-1000 nanometers and the thickness of the single nanosheet in the zinc oxide nanosheet aggregation is 1-100 nanometers;
the soluble metal copper salt is any one or a mixture of copper nitrate, copper chloride and copper sulfate;
the soluble metal silver salt is any one or a mixture of silver fluoride, silver nitrate and silver acetate;
the first dispersing agent is any one or a mixture of several of sodium dodecyl benzene sulfonate, cetyl trimethyl ammonium bromide and polyvinylpyrrolidone;
the reducing agent solution is any one or a mixture of more of ethanol, glycol and hydrazine hydrate.
6. The preparation method according to any one of claims 1 to 3, wherein the step of preparing the zinc oxide composite material simultaneously supporting palladium and nano copper/silver by using the soluble palladium salt and the nano copper/silver particle-supporting zinc oxide nano agglomerates through the nano copper/silver reduction effect comprises the following steps:
adding the zinc oxide nano agglomerates loaded with the nano copper/silver particles and soluble palladium salt into an aqueous solution containing a second dispersing agent; controlling the mass ratio of zinc oxide, soluble palladium salt, second dispersing agent and water to be 1: (0.001-0.02): (0.5-5): (50-500) reacting for 0.5-5 hours to obtain the zinc oxide composite material simultaneously supporting palladium and nano copper/silver.
7. The method according to claim 6,
the soluble palladium salt is any one or a mixture of more of palladium nitrate, palladium chloride and palladium sulfate;
the second dispersing agent is any one or a mixture of several of sodium dodecyl sulfate, oleylamine and polyvinylpyrrolidone.
8. The preparation method of claim 1 or 3, wherein the step of growing the zinc-containing ZIF on the surface of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver by using an in-situ growth method to prepare the zinc oxide-based sensing gas-sensitive composite material coated with the zinc-containing ZIF layer comprises the following steps:
adding the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver and imidazole organic ligand into a mixed solution of N, N-dimethylformamide and water; controlling the mass ratio of the zinc oxide composite material simultaneously loaded with palladium and nano copper/silver, the imidazole organic ligand, the N, N-dimethylformamide and the water to be 1: (1-5): (100-500): (100-500), reacting for 4-48 hours, coating a layer with the aperture of 10-100nm by in-situ growth
Figure FDA0003693000390000031
Zinc-containing ZIF layer to obtain a packageThe zinc oxide-based sensing gas-sensitive composite material is covered with a zinc ZIF layer;
wherein the imidazole organic ligand is any one or a mixture of more of imidazole, 2-methylimidazole, 2-nitroimidazole, benzimidazole, 4, 5-dichloroimidazole, 6-nitrobenzimidazole and imidazole-2-formaldehyde.
9. The preparation method according to claim 2 or 3, wherein the microporous molecular sieve is any one or a mixture of 4A molecular sieve, SAPO-39, SAPO-42 and AlPO-22.
10. The zinc oxide-based sensing gas-sensitive composite material prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material of claim 1 is characterized by comprising the following steps: the zinc oxide nano-agglomerates comprise nano copper/silver and nano palladium loaded on the zinc oxide nano-agglomerates, and zinc-containing ZIF loaded on the surface.
11. The zinc oxide-based sensing gas-sensitive composite material prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material of claim 2 is characterized by comprising the following steps: the nano-palladium/copper catalyst comprises zinc oxide nano-agglomerates, nano copper/silver and nano palladium loaded on the zinc oxide nano-agglomerates, and a microporous molecular sieve loaded on the surface.
12. A zinc oxide-based sensing gas-sensitive composite material prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material of claim 3 is characterized by comprising the following steps: the zinc oxide nano-cluster comprises zinc oxide nano-clusters, nano copper/silver and nano palladium loaded on the zinc oxide nano-clusters, zinc-containing ZIF loaded on the surface, and a microporous molecular sieve loaded on the surface of the zinc-containing ZIF.
13. The application of the zinc oxide-based sensing gas-sensitive composite material in the preparation of a methane sensing element is characterized in that the preparation of the methane sensing element comprises the following steps:
mixing the zinc oxide-based sensing gas-sensitive composite material with water, coating the mixture on a sensing element, and drying to prepare a methane sensing element;
wherein, the zinc oxide-based sensing gas-sensitive composite material is prepared by adopting the preparation method of the zinc oxide-based sensing gas-sensitive composite material of any one of claims 1 to 9;
the sensing element is one of a ceramic tube, a ceramic wafer and a silicon wafer.
14. The application of the zinc oxide-based sensing gas-sensitive composite material in methane sensing detection is characterized by comprising the following steps: preparing a methane sensing element by adopting a zinc oxide-based sensing gas-sensitive composite material; the methane sensing element is accessed into a gas sensing detection system, and gas detection is carried out at the temperature of 200-;
the zinc oxide-based sensing gas-sensitive composite material is prepared by the preparation method of the zinc oxide-based sensing gas-sensitive composite material according to any one of claims 1 to 9;
the gas is a mixture of methane and impurity gas, and the impurity gas is any one or a mixture of several of nitrogen dioxide, ammonia gas, sulfur dioxide, hydrogen sulfide, carbon monoxide and water vapor.
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