A kind of preparation method of the NOx sensor element based on tungsten oxide nanometer block
Technical field
The present invention relates to gas sensor technology field, particularly a kind of preparation method of the NOx sensor element based on tungsten oxide nanometer block.
Background technology
Oxides of nitrogen (NO
x) be a kind ofly cause the environmental problem such as acid rain and photo-chemical smog and the mankind formed to the toxic and harmful of grave danger.High performance gas sensitive and the device of studying the accurate examination and controlling being used for oxides of nitrogen are vital to human health.Tungsten oxide is a kind of N-type semiconductor material of broad stopband, and it has a wide range of applications in gas sensor field.As the high performance gas sensitive of one, tungsten oxide can be widely used in various toxic and harmful as NO
x, SO
2, NH
3deng detection.But, WO
3the shortcoming of gas sensitive working temperature high (about 250 DEG C) brings complicacy and instability to sensor-based system is integrated.For this reason, scientific and technical personnel are devoted to the research of the gas sensor for low-temperature working always.And tungsten oxide nanometer block has larger specific surface area and stronger gas sorption ability, thus effectively reduce working temperature while the sensitivity of gas sensor being improved further.
Summary of the invention
In order to solve problems of the prior art, the invention provides a kind of preparation method of the NOx sensor element based on tungsten oxide nanometer block, overcoming the problem that the working temperature of tungsten oxide gas sensor existence in prior art is higher.
Technical scheme of the present invention is: a kind of preparation method of the NOx sensor element based on tungsten oxide nanometer block, has following steps:
(1) cleaning of potsherd substrate
Adopt potsherd as substrate, potsherd substrate is put into successively acetone solvent, absolute ethyl alcohol sonic oscillation 15-20min, removing surface organic matter impurity.Subsequently deionized water is put in potsherd substrate to clean, after having rinsed, put into absolute ethyl alcohol, and be placed in IR bake and dry;
(2) interdigital electrode of Pt is prepared
Potsherd substrate is placed in the vacuum chamber of DPS-III type high vacuum facing-target magnetron sputtering system equipment, adopt the metal platinum of quality purity 99.99% as target, using the argon gas of quality purity 99.999% as working gas, sputtering operating pressure is 2.0Pa, sputtering power 80-90W, sputtering time 8-10min, base reservoir temperature is room temperature, forms interdigital platinum electrode at alumina base basal surface;
(3) preparation feedback solution
First configure the tungsten hexachloride solution of 0.025M-0.1M, be dissolved in by tungsten hexachloride in 65ml deionized water, magnetic agitation, to all dissolving, forms the tungsten hexachloride solution of white;
(4) gas sensor is prepared
The alumina substrate being coated with platinum electrode in step (2) is placed in the stainless steel hydrothermal reaction kettle that liner is teflon, tungsten hexachloride solution prepared by step (3) is also transferred in reactor simultaneously, sealing, then reactor is placed in thermostatic drying chamber, at alumina base basal surface synthesis tungsten oxide nanometer block structure at temperature of reaction 200 DEG C, reaction time is 6-9h, after completion of the reaction, reactor is naturally cooled to room temperature;
(5) cleaning reaction rear oxidation aluminium substrate
By the alumina substrate after solvent thermal reaction in step (4), repeatedly through deionized water and soaked in absolute ethyl alcohol cleaning, then dry 8-10h in the vacuum drying chamber of 60-80 DEG C;
(6) thermal treatment of gas sensor element
Tungsten oxide nanometer block structure gas sensor element prepared by step (5) is placed in muffle furnace heat-treat, heat treatment temperature is 300-400 DEG C, temperature retention time is 2h, and heating rate is 2-5 DEG C/min, in order to increase the crystallinity of tungsten oxide nanometer block.
Beneficial effect of the present invention is: the present invention adopts solvent-thermal method to prepare tungsten trioxide nano block structure in potsherd substrate, it has huge specific surface area and larger surfactivity, and this nanometer blocks structure is applied to gas sensor field, result shows: this tungsten trioxide nano block gas sensitive effectively can detect oxides of nitrogen under low temperature (~ 100 DEG C) condition, to oxides of nitrogen gas extremely low concentration detection (0.1ppm can be reached), and there is very high gas sensing property, excellent repeatability and good stability.And emphasis have studied the impact of solvent thermal reaction time on gas sensor element air-sensitive performance.The method has that equipment is simple, easy to operate, favorable repeatability, the advantage such as with low cost, has important practice and Research Significance.
Accompanying drawing explanation
Fig. 1 is the electron scanning micrograph of the tungsten oxide nanometer block prepared by embodiment 1, and scale is 100nm;
Fig. 2 is the XRD collection of illustrative plates of the tungsten oxide nanometer block prepared by embodiment 1;
Fig. 3 be tungsten oxide nanometer block structure gas sensor element prepared by embodiment 1 at different operating temperature to 1ppmNO
2the corresponding relation figure of gas;
Fig. 4 be tungsten oxide nanometer block structure gas sensor element prepared by embodiment 1 under 100 DEG C of conditions to 1ppmNO
2the dynamic response curve of gas;
Fig. 5 is the sensitivity under 100 DEG C of conditions of tungsten oxide nanometer block structure gas sensor element prepared by embodiment 1 and NO
2the corresponding relation figure of gas concentration;
Fig. 6 is that tungsten oxide nanometer block structure gas sensor element prepared by embodiment 1 is to the selectivity schematic diagram of multiple gases.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is elaborated.
The present invention is raw materials used all adopts commercially available chemically pure reagent.
Embodiment 1
(1) cleaning of potsherd substrate:
Adopt potsherd (1cm × 2cm) as substrate, potsherd substrate is put into successively acetone solvent, absolute ethyl alcohol sonic oscillation 15min, removing surface organic matter impurity.And be placed in IR bake and dry stand-by.
(2) interdigital electrode of Pt is prepared:
Potsherd substrate is placed in the vacuum chamber of DPS-III type high vacuum facing-target magnetron sputtering system equipment, adopt the metal platinum of quality purity 99.99% as target, using the argon gas of quality purity 99.999% as working gas, sputtering operating pressure is 2.0Pa, sputtering power 85W, sputtering time 10min, base reservoir temperature is room temperature, forms interdigital platinum electrode at alumina base basal surface.
(3) preparation feedback solution:
First configure the tungsten hexachloride solution of 0.05M, take 1.19g tungsten hexachloride and be dissolved in 65ml deionized water, magnetic agitation, to all dissolving, forms the tungsten hexachloride solution of white.
(4) gas sensor is prepared:
The alumina substrate being coated with platinum electrode in step (2) is placed in the polytetrafluoroethyllining lining of 100ml hydrothermal reaction kettle, tungsten hexachloride solution prepared by step (3) is also transferred in reactor simultaneously, sealing, then reactor is placed in thermostatic drying chamber, at alumina base basal surface synthesis tungsten oxide nanometer block structure at temperature of reaction 200 DEG C, reaction time is 7h, after completion of the reaction, reactor is naturally cooled to room temperature;
(5) cleaning reaction rear oxidation aluminium substrate:
By the alumina substrate after solvent thermal reaction in step (4), repeatedly through deionized water and soaked in absolute ethyl alcohol cleaning, then dry 9h in the vacuum drying chamber of 80 DEG C.
The electron microscopic analysis result of the surface topography of the tungsten oxide nanometer block prepared by embodiment 1 as shown in Figure 1.The nanometer blocks of square and rectangular parallelepiped can be formed on alumina substrates.
(6) thermal treatment of gas sensor element:
Tungsten oxide nanometer block structure gas sensor element prepared by step (5) is placed in muffle furnace heat-treat, heat treatment temperature is 350 DEG C, and temperature retention time is 2h, and heating rate is 2.5 DEG C/min.
The X-ray diffraction analysis result of the tungsten oxide nanometer block prepared by embodiment 1 as shown in Figure 2.The crystalline phase of XRD spectra display tungsten oxide nanometer block is the WO that monoclinic phase mixes mutually with six sides
3, and there is good crystallinity.
The obtained tungsten oxide nanometer block structure gas sensor element of embodiment 1 at different operating temperature to 1ppmNO
2the corresponding relation figure of gas as shown in Figure 3, can find out that the optimum working temperature of tungsten oxide nanometer block structure sensor is 100 DEG C.Its sensitivity at 100 DEG C and 1ppmNO
2the dynamic response figure of gas concentration as shown in Figure 4.
The sensitivity of the obtained tungsten oxide nanometer block structure gas sensor element of embodiment 1 at 100 DEG C and NO
2the corresponding relation schematic diagram of gas concentration as shown in Figure 5, wherein to 0.1,0.5,1,2,3ppmNO
2the sensitivity of gas is respectively 3.24,11.78,33.84,41.11 and 49.39.
Tungsten oxide nanometer block structure gas sensor element obtained by embodiment 1 is respectively 2.22,1.85,1.55,1.33,1.19,1.15 to the sensitivity of 100ppm ammonia, ethanol, isopropyl alcohol, methyl alcohol, acetone steam at 100 DEG C, and to 1ppmNO
2the sensitivity of gas is 33.84, as shown in Figure 6.This shows that this tungsten oxide nanometer block structure gas sensor element is to NO
2gas has excellent selectivity.
Embodiment 2
The difference of the present embodiment and embodiment 1 is: in the solvent thermal reaction liquid configured in step (3), the concentration of tungsten hexachloride is 0.025M, obtained tungsten oxide nanometer block structure gas sensor element at 100 DEG C to lppmNO
2the sensitivity of gas is 9.72.
Embodiment 3
The difference of the present embodiment and embodiment 1 is: in the solvent thermal reaction liquid configured in step (3), the concentration of tungsten hexachloride is 0.075M, obtained tungsten oxide nanometer block structure gas sensor element at 100 DEG C to lppmNO
2the sensitivity of gas is 18.34.
Embodiment 4
The difference of the present embodiment and embodiment 1 is: in the solvent thermal reaction liquid configured in step (3), the concentration of tungsten hexachloride is 0.1M, obtained tungsten oxide nanometer block structure gas sensor element at 100 DEG C to lppmNO
2the sensitivity of gas is 14.87.
The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.