CN105606660A

CN105606660A - Gas-sensitive material for detecting NO2 and method for manufacturing gas-sensitive element made of gas-sensitive material

Info

Publication number: CN105606660A
Application number: CN201510978559.6A
Authority: CN
Inventors: 邵长路; 刘益春; 赵英倩; 沈腾; 李兴华
Original assignee: Northeast Normal University
Current assignee: Northeastern University China; Northeast Normal University
Priority date: 2015-12-24
Filing date: 2015-12-24
Publication date: 2016-05-25

Abstract

The invention discloses a gas-sensitive material for detecting NO2 and a method for manufacturing a gas-sensitive element made of the gas-sensitive material. The gas-sensitive material is prepared into a SnO2 nano-fiber with a rough surface and a hollow tubular structure by adopting an electrospinning method and high-temperature processing, the hollow SnO2 nano-fiber is of a rutile structure, the SnO2 nano-fiber diameter is about 250-300nm, and the thickness of a particle layer is about 40nm. Au particle modification is performed on the surface of SnO2 in an in-situ reduction manner without changing the crystal structure of SnO2. The specific surface area of the material is increased by the one-dimensional hollow nano-structure characteristic of the gas-sensitive material, the gas-sensitive performance of SnO2 is obviously improved by precious metal modification, and higher sensitivity to NO2 and a larger measurement range are presented. The obtained material is applied to the surface of a ceramic tube, annealing is performed, and a calcined ceramic tube core and a nickel-chromium heating wire are welded to a base, accordingly, the gas-sensitive element is manufactured.

Description

A kind of NO that detects2Gas sensitive and the preparation method of gas sensor

Technical field

The invention belongs to gas detection technology field. Be specifically related to a kind of NO of detection₂Gas sensitive and the preparation method of gas sensor.

Background technology

Along with the develop rapidly of modern science and technology, the level of production of modern industrial or agricultural is also thereupon progressive fast, and people's living standard is also progressively improving, but environmental pollution is becoming a day by day serious problem that affects people's normal life. In recent years, due to poisonous, harmful, the improper discharge of flammable explosive gas in producing, leakage, the accidents such as a large amount of poisoning, blasts, fire have been caused. Nitrogen dioxide is one of at present the most dangerous air pollutants, and it plays a major role in the forming process of ozone and acid rain, continues or be often exposed to content of nitrogen dioxide to exceed 3ppm and may increase the incidence of disease of acute respiratory disease infant. Therefore, in order to reduce, reduce its impact on the mankind, to NO₂Gas carries out qualitative, quantitative analyzing and testing and monitoring has in real time become a requisite part in industrial production and daily life.

Because nano semi-conductor metal oxide has preferably selective, the feature such as measurement means is simple, good operating stability, low cost of manufacture, element power consumption are little, and be widely used in detecting toxic and harmful, flammable explosive gas etc., be the class gas sensor that current practical value is higher. SnO₂、In₂O₃, ZnO and WO₃Developed widely and be used as gas sensitive Deng metal oxide semiconductor, wherein to SnO₂The research of gas sensitive is the most extensive, and practical production at first. But in the middle of practical application, SnO₂Gas sensitive still exists selectively relatively low, to problems such as the linear response range of gas to be measured are little, has directly affected measurement result and the range of application of sensor, and material nano, metal-doped and finishing are all the effective means that improves its gas sensing property.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of novel detection NO for above-mentioned deficiency of the prior art₂Gas sensitive and the preparation method of gas sensor, to NO₂Highly sensitive, and selectively good.

The present invention solves the problems of the technologies described above adopted technical scheme:

A kind of NO that detects₂Gas sensitive, described gas sensitive obtains SnO with the method for electrostatic spinning₂Hollow Nano fiber in use, as matrix, is realized noble metal Au by in-situ reducing technology and is modified SnO₂Gas sensitive.

According to such scheme, described Au modifies SnO₂Hollow Nano fiber in use is Rutile Type, and diameter is about 50 ~ 500nm.

According to such scheme, described Au modifies SnO₂The preparation method of hollow Nano fiber in use: SnO₂Nanofiber joins certain density chlorauric acid solution and carries out in-situ reducing, at SnO₂Finishing Au nanoparticle

Son, with dry after deionized water and ethanol cyclic washing, obtain final Au and modifies SnO₂Hollow Nano fiber in use sample.

According to such scheme, described SnO₂The preparation method of hollow Nano fiber in use: obtain macromolecule/tin predecessor by electrostatic spinning technique, then predecessor is placed in Muffle furnace and is heat-treated, then the cooling SnO that just obtains at normal temperatures₂Hollow Nano fiber in use.

According to such scheme, described macromolecular material can be polyvinyl alcohol, polyvinylpyrrolidone, polyacrylonitrile etc.

According to such scheme, described calcining speed is 0.5 ~ 2 DEG C/min, and calcining heat is 500 ~ 800 DEG C.

Above-mentioned gas sensitive is made heater-type Alcohol Gas Sensor and is comprised the following steps: the sample of gained is coated in to earthenware surface, and is placed in Muffle furnace and anneals, burnt ceramic die and nickel-chromium heater strip are welded on base, and gas sensor completes.

According to such scheme, described heat treatment temperature is 200 ~ 350 DEG C, and heat treatment time is 1 ~ 2h.

The principle that the present invention adopts is: when gas sensor is exposed in air, airborne oxygen molecule can be adsorbed on fibrous material surface and trapped electrons forms O₂ ^-、O^-Or O^2-, make material surface form depleted of electrons layer, cause the barrier height between fiber to increase, the resistance of material changes thereupon, and gas signal is converted into the signal of telecommunication. Au loads on SnO₂Nano-fiber material surface has increased the avtive spot of material surface afterwards, and its catalytic action to gas has simultaneously improved Gas Surface Absorption and diffusion rate, thereby has affected the response of material to gas, has showed NO₂There is good air-sensitive character.

The advantage that the present invention has compared with known technology and good effect: the present invention adopts one dimension hollow Nano fiber in use, be conducive to the transmission of electronics. And carry out in-situ reducing Au nano particle on its surface, and the Au particle size of institute's load is little, and chemical dispersion is good, thereby has improved material to NO₂Air-sensitive performance. And preparation method provided by the present invention is simply controlled.

Brief description of the drawings

Below in conjunction with drawings and Examples, the invention will be further described. In accompanying drawing:

Fig. 1 is SnO prepared by the embodiment of the present invention 1₂The SEM Electronic Speculum figure of nanofiber;

Fig. 2 is that Au prepared by the embodiment of the present invention 2 modifies SnO₂The TEM transmission electron microscope picture of nanofiber;

Fig. 3 is the SnO of the embodiment of the present invention 1,2 preparations₂And Au modifies SnO₂The XRD collection of illustrative plates of nanofiber;

Fig. 4 is 20ppmNO in the embodiment of the present invention 1,2₂The air-sensitive response diagram of gas at different operating temperature;

Fig. 5 be the embodiment of the present invention 1,2 under optimum working temperature to NO₂The air-sensitive response diagram of variable concentrations;

Fig. 6 is the embodiment of the present invention 1,2 air-sensitive response diagram to gas with various under optimum working temperature.

Detailed description of the invention

In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is described in further detail, it is pointed out that following examples are intended to be convenient to the understanding of the present invention, and it is not played to any restriction effect.

Embodiment 1

Preparation SnO₂Nanofiber

By 0.6g stannous chloride (SnCl₂·2H₂O) add the N of 10ml with 1g PVP (PVP), in dinethylformamide (DMF) and absolute ethyl alcohol mixed solution (volume ratio DMF: ethanol=1:1), place it in constant temperature blender with magnetic force and mix, solution is placed under room temperature and continues to stir 24h to solution clear, evenly had the SnCl of viscosity₂/ PVP precursor solution.

Gained precursor solution is poured in the syringe of 10ml, syringe needle puts capillary nozzle, to inserting a metal needle in injection-tube and being connected to the positive pole of high voltage source, adjust syringe and become 10 ° of inclination angles with level, at one, metal dash receiver upper berth masking foil as negative pole, receive metallic plate and capillary tip at a distance of 15cm, high voltage source applies the voltage of 10kV. After solution consumption is complete, the fiber obtaining is positioned over and in drying box, is dried 24h.

The fiber obtaining is placed in Muffle furnace and is heat-treated, rise to 600 DEG C and at 600 DEG C of calcining 4h with the speed of 0.5 DEG C/min from normal temperature, finally the cooling SnO that just obtains at normal temperatures₂Hollow Nano fiber in use. As shown in Figure 1, can clearly see its hollow structure.

The SnO that the present embodiment is made₂Nanofiber, specifically comprises the following steps for the preparation of gas sensor as sensitive material:

By SnO₂Join in agate mortar with the ratio of 100:25 with ethanol, evenly grind along same direction, furnishing pasty state, is evenly coated in the earthenware surface with a pair of gold electrode by the sensitive material of pasty state with coating pen, makes sensitive material cover gold electrode completely and forms one deck sense film. The earthenware that scribbles sensitive material is placed in to 300 DEG C of annealing 2h of Muffle furnace. Burnt ceramic die is welded on to base, nickel-chromium heater strip, through earthenware, is welded on base equally, gas sensor completes.

Use CGS-8 intelligence air-sensitive analytical system to carry out the gas-sensitive property test of sample. Above-mentioned material is placed in to air-sensitive test macro, utilizes the method for static distribution, at detection different operating temperature, sample is to 20ppmNO₂Air-sensitive response diagram.

Embodiment 2

Noble metal Au is modified SnO₂Nano-fiber material preparation

Get 0.01g stannous chloride and join in 20mL hydrochloric acid, the SnO that then adds 0.01g to prepare₂Hollow Nano fiber in use, at room temperature stirs and fiber is taken out after 6h with deionized water rinsing 5 times, has completed SnO₂The activation of hollow Nano fiber in use. Fiber after activation is joined to stirring at normal temperature 2h in the chlorauric acid solution of 20mL0.05mmol/L. The fiber color precipitating in solution is from white pulverize redness. After being cleaned repeatedly with deionized water and ethanol, fiber taking-up dries 24h at 60 DEG C. Obtain final Au and modified SnO₂Hollow Nano fiber in use.

The product that this step makes, through X-ray diffraction analysis, as shown in Figure 2, is determined rutile-type SnO₂, (JCPDSNo.41-1445), in collection of illustrative plates, can see the characteristic diffraction peak of Au, and scheme also can find out the existence of Au by TEM, as shown in Figure 3, the finishing of a small amount of Au, its fibre structure does not change.

The Au making in the present embodiment is modified to SnO₂Nanofiber comes for the preparation of gas sensor as sensitive material. Sample and ethanol join in agate mortar with the ratio of 100:25, evenly grind along same direction, furnishing pasty state, is evenly coated in the earthenware surface with a pair of gold electrode by the sensitive material of pasty state with coating pen, makes sensitive material cover gold electrode completely and forms one deck sense film. The earthenware that scribbles sensitive material is placed in to 300 DEG C of annealing 2h of Muffle furnace. Burnt ceramic die is welded on to base, nickel-chromium heater strip (for element provides suitable operating temperature), through earthenware, is welded on base equally, gas sensor completes.

Above-mentioned gas sensor is placed in to air-sensitive test macro, identical with embodiment 1, test its under different temperatures for 20ppmNO₂Air-sensitive response, as shown in Figure 4, Au has improved it to NO after modifying₂Sensitivity. Fig. 5 is sample variable concentrations NO under optimum working temperature₂Air-sensitive response diagram, can find out Au modify SnO₂Hollow Nano fiber in use sensitive in NO₂The increase of concentration and raising, and the sample that remolding sensitivity is modified without Au is high a lot, than the nanostructured SnO reporting in document₂The NO of film₂Sensitivity (100ppm sensitivity is 19), SnO of the present invention₂The sensitivity of hollow Nano fiber in use is that the fiber sample sensitivity that 48, Au modifies is 198, is 4 times of left and right of unmodified sample. And with without Au modify SnO₂Compare, obtained larger measurement category. As shown in Figure 6, for gas with various, the SnO after Au modifies₂Hollow Nano fiber in use is to NO₂There is clearly selective, improved SnO₂Air-sensitive performance.

Claims

1. one kind is detected NO₂The preparation method of gas sensitive, it is characterized in that comprising following concrete steps:

(1) prepare macromolecule/tin predecessor composite nano fiber by electrostatic spinning technique;

(2) step (1) gained composite nano fiber is placed in Muffle furnace and is heat-treated, then the cooling SnO that just obtains at normal temperatures₂Nanofiber;

(3) by step (2) gained SnO₂Nanofiber adds in stannous chloride solution and activates, with dry after deionized water and ethanol cyclic washing;

(4) step (3) gained sample is joined in certain density gold chloride and carry out in-situ reducing, with dry after deionized water and ethanol cyclic washing, obtain Au and modify SnO₂Hollow Nano fiber in use.

2. gas sensitive according to claim 1, is characterized in that: the macromolecular material of step (1) is polyvinyl alcohol, polyvinylpyrrolidone, polyacrylonitrile etc.; The tin predecessor of step (1) is butter of tin, stannous chloride, nitric acid tin, stannous acetate, and the calcining heat of step (2) is 500 ~ 800 DEG C, described SnO₂Nanofiber is cubic rutile structure, and fibre diameter is in 50nm ~ 500nm interval; Step (3) soak time is 2 ~ 10h; Chlorauric acid solution concentration is 0.05mmol/L ~ 1mmol/L; The in-situ reducing time is 1 ~ 5h; Dry 12 ~ 24h.

3. the method for making gas sensor by the gas sensitive described in claim 1 or 2, is characterized in that comprising the following steps:

(1) by above-mentioned gas sensitive furnishing pulpous state, be evenly coated in earthenware surface, dry 4 ~ 6h;

(2) through 200 ~ 350 DEG C of annealing 1 ~ 2h;

(3) earthenware is soldered to sensor base and makes heater-type gas sensor.