CN110412085A - A kind of formaldehyde sensor gas sensitive and its sensor and preparation method, application - Google Patents
A kind of formaldehyde sensor gas sensitive and its sensor and preparation method, application Download PDFInfo
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- CN110412085A CN110412085A CN201910646539.7A CN201910646539A CN110412085A CN 110412085 A CN110412085 A CN 110412085A CN 201910646539 A CN201910646539 A CN 201910646539A CN 110412085 A CN110412085 A CN 110412085A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
- G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
Abstract
The present invention relates to gas sensor technical field more particularly to a kind of formaldehyde sensor gas sensitive and its sensor and preparation methods, application.The gas sensitive is by Sn3O4It is formed with rGO, wherein the Sn3O4Nanometer sheet, which is stacked, forms three-dimensional flower-like structure, and the rGO is located at Sn3O4Being formed in nanometer sheet has Sn3O4The gas sensitive of-rGO hetero-junctions, and this heterogeneous becomes p-n junction.Formaldehyde gas sensor of the invention is with flower-shaped Sn3O4- rGO heterojunction structure is gas sensitive, and by the gas sensor of building heater-type structure, efficiently solves the problems such as operation temperature present in traditional gas sensor is high, sensitivity is low, poor selectivity, repeatability difference.
Description
Technical field
The present invention relates to gas sensor technical field more particularly to a kind of formaldehyde sensor gas sensitives and its sensor
With preparation method, application.
Background technique
It is only intended to increase understanding of the overall background of the invention for information disclosed in background of invention, without
It is existing well known to persons skilled in the art so to be considered as recognizing or imply that information composition has become in any form
Technology.
In order to meet the requirement of monitored gas environment and industrial gasses analysis, researcher has studied various gases and passes
Sensor is for detecting toxic and harmful gas, such as nitrogen oxides, oxycarbide, sulfide and volatile organic compounds.As
One of most common volatile organic compounds, formaldehyde play more and more important in chemistry, the fields such as biology and textile industry
Effect.But due to that can have many potential health risks, including maincenter mind when the mankind are chronically exposed in formaldehyde gas
Through system damage, disease of immune system, respiratory disease, even cancer, formaldehyde is classified as by international cancer research institution
" carcinogenic substance ".Therefore, the research of the gas sensor of formaldehyde can effectively and accurately be detected to monitored gas environment and industrial gas
Body analysis is particularly important.
In in the past few decades, it is based on metal oxide (Sn3O4,SnO2,ZnO,In2O3, NiO and CuO) semiconductor
Formaldehyde gas sensor has obtained extensive concern due to low cost, low energy consumption, the advantages such as easy to operate.However, being based on metal
The gas sensor of oxide semiconductor, which generally requires higher operating temperature (200-400 DEG C) just, can be such that device obtains preferably
Sensing capabilities.This means that needing to consume a large amount of energy, and higher work when the gas sensor work of the type
Temperature can reduce the stability and working life of gas sensor.Secondly, this traditional based on metal-oxide semiconductor (MOS)
The problems such as also generally existing sensitivity of gas sensor is low, repeatable poor, so that the sensor of the type is difficult to obtain extensively
Application, this be also restrict gas sensor technology development key factor.
To sum up, present inventors believe that the more existing gas sensor based on metal-oxide semiconductor (MOS) has operation
The disadvantages of temperature is high, sensitivity is low, repeatable difference.Therefore, the sensor mechanism of further search gas sensor, seeks more
Effective reliable sensing material, is the key that solve the problems, such as that existing INVENTIONConventional metal-oxide gas sensor exists.
Summary of the invention
In view of the above problems, the present invention is intended to provide a kind of formaldehyde sensor gas sensitive and its sensor and system
Preparation Method, application.Experiment proves that the operating temperature of inventive sensor is low, high sensitivity, repeatability are strong；Change well
Be apt to the existing gas sensor operation temperature based on metal-oxide semiconductor (MOS) is high, sensitivity is low, repeatable difference not
Foot.
An object of the present disclosure: a kind of formaldehyde gas sensor gas sensitive and preparation method thereof is provided.
Second purpose of the invention: a kind of formaldehyde gas sensor and preparation method thereof is provided.
Third purpose of the present invention: answering for described formaldehyde gas sensor gas sensitive and preparation method thereof and sensor is provided
With.
For achieving the above object, the invention discloses following technical proposals:
Firstly, the present invention discloses a kind of formaldehyde gas sensor gas sensitive, by Sn3O4It is formed with rGO, wherein described
Sn3O4Nanometer sheet, which is stacked, forms three-dimensional flower-like structure, and the rGO is located at Sn3O4In nanometer sheet, so that being formed has
Sn3O4The gas sensitive of-rGO hetero-junctions, and this heterogeneous becomes p-n junction.
As further technical solution, the Sn3O4The thickness of nanometer sheet between 10-20nm, diameter 1-3 μm it
Between.
It is proposed by the present invention that there is Sn3O4The characteristics of gas sensitive of-rGO hetero-junctions, is: this to have three-dimensional structure
Sn3O4Nano flower has biggish specific surface area, helps to improve response intensity and the sensitivity of PARA FORMALDEHYDE PRILLS(91,95) gas.In addition,
Sn3O4Nanometer sheet and the rGO of its surface growth form Sn3O4- rGO heterogeneous (p-n) knot can reduce working sensor temperature
Degree and raising air-sensitive performance etc. play the role of huge.In addition, relative to SnO2The tin oxidation that both are common with SnO
Object, Sn3O4It is the tin-oxide containing mixed valence, the tin both containing 4 valences, while also having the tin of divalent.Its band gap width 2.2-
2.9eV, compared to SnO23.6eV and SnO 2.7-3.2eV forbidden bandwidth it is lower, Sn3O4It can protect in room temperature to 400 DEG C
Holding quality is constant, i.e., it is the stabilizing material at room temperature to 400 DEG C.
Secondly, the present invention discloses a kind of formaldehyde gas sensor, it is heater-type structure, comprising: pedestal, connects support leg
Terminal, ceramic tube, heater strip, circular metal electrode, gas sensitive and conducting wire；Wherein, the gas sensitive is above-mentioned formaldehyde
Gas sensor gas sensitive is provided with six groups of support legs on the bottom surface of the pedestal, and the upper surface of the pedestal is correspondingly
Six groups of binding posts are provided with, heater strip are provided in the ceramic tube, and the both ends of heater strip extend respectively to ceramic tube two
The outside of port；The circular metal electrode is two, is covered on the outer surface of ceramic tube along the circumferential direction of ceramic tube,
And there is interval between two circular metal electrodes；The ceramic tube for being provided with circular metal electrode is arranged in the gas sensitive
On outer surface, so that ceramic tube and circular metal electrode be wrapped up wherein；The heater strip extends to outside ceramic tube
Both ends connect respectively with two binding posts；The conducting wire is four, for connecting four additional binding post and endless metal electricity
Pole, and the two sides of a circular metal electrode are arranged in the corresponding circular metal electrode of every two conducting wire, two electrodes.
As further technical solution, the material of the ceramic tube is aluminium oxide etc..
As further technical solution, the material of the heater strip is nichrome, any one in ferrochrome.
As further technical solution, the material of the metal electrode is noble metal, such as gold, platinum, silver, palladium, iridium.
As further technical solution, the material of the conducting wire is noble metal, such as gold, platinum, silver, palladium, iridium.
As further technical solution, it is spiral shape that the heater strip, which is located at the part in ceramic tube,.In order to more
Operating temperature needed for rapidly providing sensor.
Again, the present invention provides a kind of preparation method of formaldehyde gas sensor gas sensitive, includes the following steps:
(1) then graphene oxide dispersion is added to abundant dissolution in stannous chloride, citrate stirring soluble in water
And it stirs and to form uniform mixed solution；Sodium hydroxide solution is add to the above mixed solution stirring, obtains precursor solution；
(2) precursor solution in step (1) is subjected to hydro-thermal reaction, after product is centrifuged, obtained solid produces
Object is by Sn3O4The heterojunction structure gas sensitive formed with rGO.
As further technical solution, in step (1), the stannous chloride, citrate (such as sodium citrate), hydrogen
Sodium oxide molybdena, graphene oxide adding proportion be sequentially 1mmol:(2-3) mmol:(2-4) mmol:(10-20) mg, the use of water
Amount guarantees sufficiently to dissolve stannous chloride and citrate.
As further technical solution, in step (1), the preparation of the graphene oxide dispersion is by graphite oxide
Alkene is distributed in deionized water, ethyl alcohol or n,N-Dimethylformamide (DMF) equal solvent, and ultrasonic disperse forms graphene oxide point
Dispersion liquid.
As further technical solution, in step (2), the condition of the hydro-thermal reaction are as follows: anti-between 160-180 DEG C
Answer 12-16h.
As further technical solution, in step (2), the centrifugation rate is 8000-12000rpm.
As further technical solution, in step (2), further include the steps that washing the solid product, have
Body are as follows: sequentially cleaned with ethyl alcohol, deionized water, can be cleaned multiple times when necessary, such as cleaning 3-5 times.
As further technical solution, in step (2), further include the steps that the solid product is dried, institute
State drying condition are as follows: the dry 10-12h between 60-80 DEG C obtains gas sensitive powder (Sn after dry3O4-rGO)。
Thirdly, the present invention discloses a kind of preparation method of formaldehyde gas sensor, includes the following steps:
S1, the gas sensitive powder is prepared into finely dispersed paste；
S2, the paste in step S1 is uniformly coated on the ceramic pipe surface with a pair of metal electrodes, dried in the air naturally
It is dried after dry；
S3, will it is dry in step S2 after ceramic tube in heating wire, metal electrode be respectively welded at connecing for six leg bases
To get the formaldehyde gas sensor of heater-type structure on terminal.
As further technical solution, in step S1, the paste the preparation method comprises the following steps: by gas sensitive powder with
Deionized water is mixed by mass volume ratio (mg/ml) 180-220:1, and then grinding and ultrasound, obtain finely dispersed paste,
Wherein, the milling time is 10-20min, ultrasonic time 30-60min.
As further technical solution, in step S2, the drying condition are as follows: the dry 10-12h between 60-80 DEG C.
Finally, the present invention discloses described formaldehyde gas sensor gas sensitive and preparation method thereof and sensor in environment gas
Application in the fields such as body monitoring, industrial gasses analysis.
Compared with prior art, the present invention achieve it is following the utility model has the advantages that
(1) formaldehyde gas sensor of the invention is with flower-shaped Sn3O4- rGO heterojunction structure is gas sensitive, and passes through building
The gas sensor of heater-type structure efficiently solves the height of operation temperature present in traditional gas sensor, sensitivity
The problems such as low, poor selectivity, repeatability difference.
(2) present invention has Sn using one step hydro thermal method synthesis3O4The gas sensitive of-rGO heterojunction structure, the ratio of the material
Surface area is big, is capable of providing a large amount of active site, makes the activation energy to react reduction, therefore reduces device to operation temperature
The requirement of degree thereby reduces the power consumption of device, is conducive to the repeatability and long-term stability of device sensing capabilities.
(3) compare traditional gas sensor, the invention proposes a kind of operating temperature low (150 DEG C), high sensitivity, can
The strong formaldehyde gas sensor of repeatability and its it is low in cost, method is simple and the preparation method that can be mass-produced.
Detailed description of the invention
The Figure of description for constituting a part of the invention is used to provide further understanding of the present invention, and of the invention shows
Examples and descriptions thereof are used to explain the present invention for meaning property, does not constitute improper limitations of the present invention.
Fig. 1 is the gas sensitive (Sn prepared for the embodiment of the present invention 13O4- rGO) SEM figure.
Fig. 2 is the gas sensitive (Sn prepared for the embodiment of the present invention 13O4- rGO) N2The BET specific surface of physical absorption
Product.
Fig. 3 is the structural schematic diagram of formaldehyde gas sensor in the embodiment of the present invention 5.
Fig. 4 is the sectional view of formaldehyde gas sensor in the embodiment of the present invention 5.
Fig. 5 is for the gas-sensing mechanisms schematic diagram of formaldehyde gas sensor in the embodiment of the present invention.
Fig. 6 is response of the formaldehyde gas sensor of the embodiment of the present invention 5 at 150 DEG C to the formaldehyde gas of various concentration
Curve.
Fig. 7 is that the formaldehyde gas sensor of the embodiment of the present invention 5 is strong to the response of the gas with various of 100ppm at 150 DEG C
Degree.
Fig. 8 be for formaldehyde gas sensor continuous five times of the embodiment of the present invention 5 at 150 DEG C to the formaldehyde gas of 100ppm
The dynamic response curve of body.
Fig. 9 be in formaldehyde gas sensor 60 days of the embodiment of the present invention 5 at 150 DEG C to the dynamic of the formaldehyde of 100ppm
Response intensity.
Figure acceptance of the bid note respectively represents: 1- pedestal, 2- support leg, 3- binding post, 4- ceramic tube, 5- heater strip, 6- annular gold
Belong to electrode, 7- gas sensitive, 8- conducting wire.
Specific embodiment
It is noted that following detailed description is all illustrative, it is intended to provide further instruction to the present invention.Unless another
It indicates, all technical and scientific terms used herein has usual with general technical staff of the technical field of the invention
The identical meanings of understanding.
It should be noted that term used herein above is merely to describe specific embodiment, and be not intended to restricted root
According to exemplary embodiments of the present invention.Such as, used herein, unless the context clearly indicates otherwise, otherwise singular shape
Formula is also intended to include plural form, additionally, it should be understood that, when in the present specification using term "comprising" and/or " packet
Include " when, indicate existing characteristics, step, operation, device, component and/or their combination.
As previously mentioned, the more existing gas sensor based on metal-oxide semiconductor (MOS) has operation temperature
The disadvantages of height, low, repeatable poor sensitivity.Therefore, the present invention proposes a kind of formaldehyde sensor gas sensitive and its sensor
With preparation method, application；The present invention is further illustrated now in conjunction with the drawings and specific embodiments.
Embodiment 1
1, a kind of preparation method of formaldehyde sensor gas sensitive, including the following steps:
(1-1) according to 1:2.5 molar ratio precise stannous chloride (SnCl2·2H2) and sodium citrate O
(Na3C6H5O7·2H2O) (dosage of stannous chloride and sodium citrate is respectively 4 and 10mmol), is added to 10ml deionized water
In, uniform mixed solution is obtained using magnetic stirrer 40min.
The graphene oxide (GO) of 15mg is distributed in n,N-Dimethylformamide (DMF) solution of 30ml by (1-2), is surpassed
Sound 20-30min obtains the GO dispersion liquid of 0.5mg/ml.
Above-mentioned GO dispersion liquid is added to the (dosage of GO dispersion liquid in the mixed solution that the step (1-1) obtains by (1-3)
For 1.5ml), magnetic agitation 20min.
0.08g sodium hydroxide (NaOH) is added in 10ml deionized water and obtains sodium hydroxide solution by (1-4), rear to be added
Into above-mentioned mixed solution, magnetic agitation 40min obtains uniform mixing precursor solution.
Precursor solution obtained above is transferred in the autoclave of 50ml teflon lined by (1-5), at 180 DEG C
Under the conditions of hydro-thermal reaction 16h.
After (1-6) above-mentioned hydro-thermal reaction, autoclave is down to room temperature naturally.
The resulting product of above-mentioned hydro-thermal reaction is centrifuged by (1-7), centrifugation rate 8000rpm, respectively with ethyl alcohol and go from
Sub- water cleans 3 times repeatedly, and dry 12h, obtains having flower-shaped Sn under the conditions of 80 DEG C3O4The powder of-rGO heterojunction structure.
2, a kind of preparation method of formaldehyde sensor, including the following steps:
(2-1) takes what the present embodiment step (1-7) of 200mg obtained to have flower-shaped Sn3O4The powder of-rGO heterojunction structure,
It is mixed with the deionized water of 1ml, grinds 15min with agate mortar, ultrasonic 35min obtains finely dispersed Sn3O4- rGO paste
Object.
(2-2) dips the Sn that the step (2-1) obtains with hooking pen3O4- rGO paste is uniformly coated on one
To the Al of gold electrode2O3Ceramic pipe surface, the number that each device hooking pen dips paste coating are controlled at 6 times.
(2-3) is coated with Sn for above-mentioned3O4The ceramic tube of-rGO paste places 12h naturally dry, after under the conditions of 80 DEG C
Dry 12h.
The resistance heating wire of ceramic tube and nichrome that the step (2-3) obtains successively is welded on hexagonal by (2-4)
On pedestal.
Embodiment 2
1, a kind of preparation method of formaldehyde sensor gas sensitive, including the following steps:
(1-1) according to 1:2 molar ratio precise stannous chloride (SnCl2·2H2) and sodium citrate (Na O3C6H5O7·
2H2O) (dosage of stannous chloride and sodium citrate is respectively 4 and 8mmol), is added in 20ml deionized water, is stirred using magnetic force
It mixes device stirring 30min and obtains uniform mixed solution.
The graphene oxide (GO) of 10mg is distributed in the deionized water of 25ml by (1-2), and ultrasonic 20min is obtained
The GO dispersion liquid of 0.4mg/ml.
Above-mentioned GO dispersion liquid is added to the (dosage of GO dispersion liquid in the mixed solution that the step (1-1) obtains by (1-3)
For 1.5ml), magnetic agitation 30min.
0.16g sodium hydroxide (NaOH) is added to the hydroxide for obtaining that concentration is 0.2M in 20ml deionized water by (1-4)
Sodium solution, after be add to the above mixed solution, magnetic agitation 30min obtains uniform mixing precursor solution.
Precursor solution obtained above is transferred in the autoclave of 50ml teflon lined by (1-5), at 180 DEG C
Under the conditions of hydro-thermal reaction 16h.
After (1-6) above-mentioned hydro-thermal reaction, autoclave is down to room temperature naturally.
The resulting product of above-mentioned hydro-thermal reaction is centrifuged by (1-7), centrifugation rate 12000rpm, respectively with ethyl alcohol and go from
Sub- water cleans 3 times repeatedly, and dry 12h, obtains having flower-shaped Sn under the conditions of 80 DEG C3O4The powder of-rGO heterojunction structure.
2, a kind of preparation method of formaldehyde sensor, including the following steps:
(2-1) takes what the present embodiment step (1-7) of 180mg obtained to have flower-shaped Sn3O4The powder of-rGO heterojunction structure,
It is mixed with the deionized water of 1ml, grinds 10min with agate mortar, ultrasonic 60min obtains finely dispersed Sn3O4- rGO paste
Object.
(2-2) dips the Sn that the step (2-1) obtains with hooking pen3O4- rGO paste is uniformly coated on one
To the Al of gold electrode2O3Ceramic pipe surface, the number that each device hooking pen dips paste coating are controlled at 7 times.
(2-3) is coated with Sn for above-mentioned3O4The ceramic tube of-rGO paste places 12h naturally dry, after under the conditions of 80 DEG C
Dry 12h.
The resistance heating wire of ceramic tube and nichrome that the step (2-3) obtains successively is welded on hexagonal by (2-4)
On pedestal.
Embodiment 3
1, a kind of preparation method of formaldehyde sensor gas sensitive, including the following steps:
(1-1) according to 1:3 molar ratio precise stannous chloride (SnCl2·2H2) and sodium citrate (Na O3C6H5O7·
2H2O) (dosage of stannous chloride and sodium citrate is respectively 4 and 12mmol), is added in 10ml deionized water, uses magnetic force
Blender stirring 30-60min obtains uniform mixed solution.
The graphene oxide (GO) of 18mg is distributed in 30ml ethanol solution by (1-2), and ultrasonic 30min obtains 0.6mg/
The GO dispersion liquid of ml.
Above-mentioned GO dispersion liquid is added to the (dosage of GO dispersion liquid in the mixed solution that the step (1-1) obtains by (1-3)
For 1.5ml), magnetic agitation 30min.
0.08g sodium hydroxide (NaOH) is added in 10ml deionized water and obtains sodium hydroxide solution by (1-4), rear to be added
Into above-mentioned mixed solution, magnetic agitation 30min obtains uniform mixed solution.
Mixed solution obtained above is transferred in the autoclave of 50ml teflon lined by (1-5), in 180 DEG C of items
Hydro-thermal reaction 16h under part.
After (1-6) above-mentioned hydro-thermal reaction, autoclave is down to room temperature naturally.
The resulting product of above-mentioned hydro-thermal reaction is centrifuged by (1-7), centrifugation rate 8000rpm, respectively with ethyl alcohol and go from
Sub- water cleans 3 times repeatedly, and dry 10h, obtains having flower-shaped Sn under the conditions of 60 DEG C3O4The powder of-rGO heterojunction structure.
2, a kind of preparation method of formaldehyde sensor, including the following steps:
(2-1) takes what the present embodiment step (1-7) of 210mg obtained to have flower-shaped Sn3O4The powder of-rGO heterojunction structure,
It is mixed with the deionized water of 1ml, grinds 20min with agate mortar, ultrasonic 30min obtains finely dispersed Sn3O4- rGO paste
Object.
(2-2) dips the Sn that the step (2-1) obtains with hooking pen3O4- rGO paste is uniformly coated on one
To the Al of gold electrode2O3Ceramic pipe surface, the number that each device hooking pen dips paste coating are controlled at 5 times.
(2-3) is coated with Sn for above-mentioned3O4The ceramic tube of-rGO paste places 12h naturally dry, after under the conditions of 60 DEG C
Dry 10h.
The resistance heating wire of ceramic tube and nichrome that the step (2-3) obtains successively is welded on hexagonal by (2-4)
On pedestal.
Embodiment 4
1, a kind of preparation method of formaldehyde sensor gas sensitive, including the following steps:
(1-1) according to 1:2.5 molar ratio precise stannous chloride (SnCl2·2H2) and sodium citrate O
(Na3C6H5O7·2H2O) (dosage of stannous chloride and sodium citrate is respectively 4 and 10mmol), is added to 20ml deionized water
In, uniform mixed solution is obtained using magnetic stirrer 30min.
The graphene oxide (GO) of 20mg is distributed in n,N-Dimethylformamide (DMF) solution of 30ml by (1-2), is surpassed
Sound 20-30min obtains the GO dispersion liquid of 0.5mg/ml.
Above-mentioned GO dispersion liquid is added to the (dosage of GO dispersion liquid in the mixed solution that the step (1-1) obtains by (1-3)
For 2ml), magnetic agitation 25min.
0.16g sodium hydroxide (NaOH) is added in 20ml deionized water and obtains sodium hydroxide solution by (1-4), rear to be added
Into above-mentioned mixed solution, magnetic agitation 50min obtains uniform mixing precursor solution.
Precursor solution obtained above is transferred in the autoclave of 50ml teflon lined by (1-5), at 160 DEG C
Under the conditions of hydro-thermal reaction 12h.
After (1-6) above-mentioned hydro-thermal reaction, autoclave is down to room temperature naturally.
The resulting product of above-mentioned hydro-thermal reaction is centrifuged by (1-7), centrifugation rate 12000rpm, respectively with ethyl alcohol and go from
Sub- water cleans 3 times repeatedly, and dry 10h, obtains having flower-shaped Sn under the conditions of 60 DEG C3O4The powder of-rGO heterojunction structure.
2, a kind of preparation method of formaldehyde sensor, including the following steps:
(2-1) takes what the present embodiment step (1-7) of 220mg obtained to have flower-shaped Sn3O4The powder of-rGO heterojunction structure,
It is mixed with the deionized water of 1ml, grinds 10min with agate mortar, ultrasonic 40min obtains finely dispersed Sn3O4- rGO paste
Object.
(2-2) dips the Sn that the step (2-1) obtains with hooking pen3O4- rGO paste is uniformly coated on one
To the Al of gold electrode2O3Ceramic pipe surface, the number that each device hooking pen dips paste coating are controlled at 7 times.
(2-3) is coated with Sn for above-mentioned3O4The ceramic tube of-rGO paste places 12h naturally dry, after under the conditions of 60 DEG C
Dry 10h.
The resistance heating wire of ceramic tube and nichrome that the step (2-3) obtains successively is welded on hexagonal by (2-4)
On pedestal.
Embodiment 5
With reference to Fig. 3 and 4, a kind of formaldehyde gas sensor uses method described in embodiment 1 to prepare, the sensor its
For heater-type structure comprising: pedestal 1, support leg 2, binding post 3, alumina ceramic tube 4, nichrome heater strip 5, gold electricity
Pole 6, gas sensitive 7 and platinum conducting wire 8；Wherein, the gas sensitive 7 is formaldehyde gas sensor air-sensitive material prepared by embodiment 1
Expect (Sn3O4- rGO), six groups of support legs 2 are provided on the bottom surface of the pedestal 1, are provided on 1 upper surface of pedestal corresponding
Six groups of binding posts 3, heater strip 5 is provided in the ceramic tube 4, and it is spiral that heater strip 5, which is located at the part in ceramic tube 4,
Shape, the both ends of the heater strip extend respectively to the outside of two ports of ceramic tube；The circular metal electrode 6 is two,
It is covered on the outer surface of ceramic tube 4 along the circumferential direction of ceramic tube 4, and there is interval between two circular metal electrodes 6；Institute
It states gas sensitive 7 to be arranged on the outer surface for the ceramic tube 4 for being provided with circular metal electrode 6, thus by ceramic tube 4 and annular gold
Belong to electrode 6 to wrap up wherein；The both ends of the heater strip 5 extended to outside ceramic tube 4 connect with two binding posts 3 respectively
It connects；The conducting wire 8 is four, for connecting four additional binding post 3 and circular metal electrode 6, and every two conducting wire corresponding one
The two sides of a circular metal electrode are arranged in a circular metal electrode, two electrodes.
Performance test:
(1) Fig. 1 is the formaldehyde sensor gas sensitive (Sn that embodiment 1 is prepared by one step hydro thermal method3O4- rGO) SEM
Figure, as can be seen from the figure: the Sn3O4- rGO is by the Sn with a thickness of 10-20nm3O4Nanometer sheet, which is stacked, to be assembled into
Flower-like structure, the average diameter of flower-like structure is about between 1-3 μm, and uniformity is good, large specific surface area, wherein rGO passes through
Hydrothermal Growth is in Sn3O4In nanometer sheet.Fig. 2 show the Sn of the preparation of embodiment 13O4The N of-rGO2The BET of physical absorption compares table
Area is 46.5649m2g-1, the performance of sensor can be effectively improved.
(2) Fig. 5 is the gas-sensing mechanisms schematic diagram of formaldehyde gas sensor in embodiment 5.In air, surface can mention
Oxygen molecule, O are adsorbed for a large amount of active site2From Sn3O4Conduction band in capture a large amount of electronics and then ionization is formed largely
O2 -、O-、O2-, therefore, the aerial resistance value Ra of sensor is in compared with high-impedance state, when the sensor is placed in embodiment 5
When in formaldehyde gas, the O of a large amount of formaldehyde gas molecule and material surface absorption2 -、O-、O2-Redox reaction occurs, it will
Electronics is re-released into Sn3O4Conduction band, resistance value Rg of the sensor in object gas is greatly lowered at this time, to improve
The response intensity of PARA FORMALDEHYDE PRILLS(91,95) gas and sensitivity.In addition, Sn3O4Nanometer sheet and the rGO of its surface growth form Sn3O4-
RGO heterogeneous (p-n) knot can play the role of huge in terms of reducing senor operating temperature and improving.Cause
For in air, Sn3O4The interface of-rGO can be since the different band curvatures that occur of fermi level be to form p-n junction, potential barrier
It obviously increases.Shown in resistance value R such as formula (1) due to gas sensitive:
R∝A(qφ/kT) (1)；
In formula (1), the A is thermal constant, and φ is the barrier height of hetero-junctions, and k is Boltzmann constant, and T is absolute
Temperature；Therefore the variation of barrier height can make the aerial resistance value Ra of device that can exponentially change.Since gas response is strong
Spend S=Ra/Rg, therefore Sn3O4The introducing of-rGO hetero-junctions can effectively improve sensor to the response intensity of object gas and
Sensitivity.
(3) Fig. 6 be embodiment 5 sensor at 150 DEG C to the response curve of the formaldehyde gas of various concentration, from Fig. 6
(a) this it appears that the response of the sensor PARA FORMALDEHYDE PRILLS(91,95) increases with the increase of formaldehyde gas concentration in.And in 1-
The response of two concentration range inner sensor PARA FORMALDEHYDE PRILLS(91,95) gases of 100ppm and 100-1000ppm be all it is linearly increasing, such as Fig. 6
(b) shown in.Wherein, when formaldehyde gas concentration is 1-100ppm, the relationship of response and concentration of formaldehyde can be fitted linear
Equation: y1=6.8743+0.3754x1；When formaldehyde gas concentration is 100-1000ppm, the relationship of response and concentration of formaldehyde can
It is expressed as linear equation: y2=33.0558+0.0946x2.Obviously, sensor to the sensitivity of the formaldehyde gas of low concentration more
Height, this is because the transfer rate that will lead to electronics when formaldehyde gas excessive concentration is greatly lowered, to reduce PARA FORMALDEHYDE PRILLS(91,95)
The sensitivity of gas.
(4) Fig. 7 be the gas sensor for preparing of embodiment 5 at 150 DEG C to the ethyl alcohol of 100ppm, dimethylbenzene, formaldehyde, third
The response of ketone and triethylamine, response are respectively 23.2,5.2,43.6,4.3 and 23.9, and showing the sensor PARA FORMALDEHYDE PRILLS(91,95) has
Good gas-selectively.
(5) Fig. 8 be embodiment 5 prepare gas sensor continuous five times at 150 DEG C to the formaldehyde gas of 100ppm
Dynamic response curve.It is worth noting that, the response of 5 loop test PARA FORMALDEHYDE PRILLS(91,95) gases is maintained at comparable level, i.e. S=
43.5, without significantly fluctuating and declining, illustrate that the sensor has excellent repeatability.
(6) Fig. 9 is loud to the dynamic of the formaldehyde of 100ppm at 150 DEG C in gas sensor 60 days of the preparation of embodiment 5
Answer intensity.It is easy discovery, after to sensor test in continuous 60 days, which does not show PARA FORMALDEHYDE PRILLS(91,95) gas
Body response is substantially reduced, and illustrates that the sensor has good long-time stability.
The above description is only a preferred embodiment of the present invention, is not intended to restrict the invention, for those skilled in the art
For member, the invention may be variously modified and varied.All within the spirits and principles of the present invention, it is made it is any modification,
Equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (10)
1. a kind of formaldehyde gas sensor gas sensitive, which is characterized in that by Sn3O4It is formed with rGO, wherein the Sn3O4Nanometer
Piece, which is stacked, forms three-dimensional flower-like structure, and the rGO is located at Sn3O4Being formed in nanometer sheet has Sn3O4- rGO hetero-junctions
Gas sensitive, and this heterogeneous becomes p-n junction.
2. formaldehyde gas sensor gas sensitive as described in claim 1, which is characterized in that the Sn3O4The thickness of nanometer sheet
Between 10-20nm, diameter is between 1-3 μm.
3. a kind of preparation method of formaldehyde gas sensor gas sensitive, which comprises the steps of:
(1) by stannous chloride, citrate stirring soluble in water to abundant dissolution, graphene oxide dispersion is then added and stirs
It mixes to form uniform mixed solution；Sodium hydroxide solution is add to the above mixed solution stirring, obtains precursor solution；
(2) by step (1) precursor solution carry out hydro-thermal reaction, after product is centrifuged, obtained solid product is i.e.
For by Sn3O4The heterojunction structure gas sensitive formed with rGO.
4. the preparation method of formaldehyde gas sensor gas sensitive as claimed in claim 3, which is characterized in that in step (1),
The stannous chloride, citrate (preferably sodium citrate), sodium hydroxide, graphene oxide adding proportion be sequentially
1mmol:(2-3) mmol:(2-4) mmol:(10-20) mg；
Preferably, in step (1), the preparation of the graphene oxide dispersion be graphene oxide is distributed to deionized water,
In ethyl alcohol or n,N-Dimethylformamide, ultrasonic disperse forms graphene oxide dispersion；
Preferably, in step (2), the condition of the hydro-thermal reaction are as follows: 12-16h is reacted between 160-180 DEG C；
Preferably, in step (2), the centrifugation rate is 8000-12000rpm；
Preferably, in step (2), further include the steps that washing the solid product, specifically: with sequentially using second
Alcohol, deionized water cleaning, are preferably cleaned 3-5 times；
Preferably, in step (2), further include the steps that the solid product is dried, the drying condition are as follows: in 60-
Dry 10-12h, obtains gas sensitive powder after dry between 80 DEG C.
5. a kind of formaldehyde gas sensor, which is characterized in that it is heater-type structure, comprising: pedestal, support leg, binding post, pottery
Porcelain tube, heater strip, circular metal electrode, gas sensitive and conducting wire；Wherein, gas sensitive first of any of claims 1 or 2
The formaldehyde gas sensor gas sensitive of the preparation of method described in aldehyde gas sensor gas sensitive and/or right 3 or 4, it is described
It is provided with support leg on one bottom surface of pedestal, six groups of binding posts are provided on the face of the bottom surface opposite side, are set in the ceramic tube
It is equipped with heater strip, and the both ends of heater strip extend respectively to the outside of two ports of ceramic tube；The circular metal electrode is two
It is a, it is covered on the outer surface of ceramic tube along the circumferential direction of ceramic tube, and there is interval between two circular metal electrodes；
The gas sensitive is arranged on the outer surface for being provided with the ceramic tube of circular metal electrode, thus by ceramic tube and endless metal
Electrode wraps up wherein；The both ends of the heater strip extended to outside ceramic tube are connect with two binding posts respectively；It is described
Conducting wire is four, for connecting four additional binding post and circular metal electrode, and the corresponding endless metal of every two conducting wire
The two sides of a circular metal electrode are arranged in electrode, two electrodes.
6. formaldehyde gas sensor as claimed in claim 5, which is characterized in that the material of the ceramic tube is aluminium oxide；
Preferably, the material of the heater strip is nichrome, any one in ferrochrome；
Preferably, the material of the metal electrode is noble metal, such as any one in gold, platinum, silver, palladium, iridium；
Preferably, the material of the conducting wire is noble metal, such as any one in gold, platinum silver, palladium, iridium.
7. such as formaldehyde gas sensor described in claim 5 or 6, which is characterized in that the heater strip is located in ceramic tube
Part is spiral shape.
8. a kind of preparation method of formaldehyde gas sensor, which comprises the steps of:
S1, the gas sensitive for preparation method described in gas sensitive of any of claims 1 or 2 and/or claim 3 or 4
It is prepared into finely dispersed paste；
S2, the paste in step S1 is uniformly coated on the ceramic pipe surface with a pair of metal electrodes, after natural drying
It is dried；
S3, will it is dry in step S2 after ceramic tube in heating wire, metal electrode be respectively welded at the binding posts of six leg bases
On to get heater-type structure formaldehyde gas sensor.
9. the preparation method of formaldehyde gas sensor as claimed in claim 8, which is characterized in that in step S1, the paste
Object the preparation method comprises the following steps: gas sensitive powder is mixed with deionized water by mass volume ratio 180-220:1, then mg/ml is ground
Mill and ultrasound, obtain finely dispersed paste, wherein the milling time is 10-20min, ultrasonic time 30-60min；
Preferably, in step S2, the drying condition are as follows: the dry 10-12h between 60-80 DEG C.
10. gas sensitive as claimed in claim 1 or 2 and/or preparation method as described in claim 3 or 4 and/or as weighed
Benefit requires application of the described in any item sensors of 5-7 in monitored gas environment, industrial gasses analysis field.
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