Disclosure of Invention
The invention aims at designing BP/ZnFe2O4 composite material, realizing the detection of acetone gas with lower detection limit (100 ppb-2 ppm), high sensitivity (about 5.34 for acetone response Ra/Rg of 500 ppb) and quick response (6 s for acetone response time of 500 ppb), and sensitively sensing the existence of trace acetone gas in simulated respiratory gas, so as to solve the technical problem that the existing acetone detection technology is difficult to quickly distinguish the weak change of the acetone concentration within the range of 100 ppb-2 ppm.
In order to solve the technical problems, the invention adopts the following technical scheme:
An acetone gas sensor comprises a micro-thermal electrode plate, wherein a gas sensitive layer formed by BP/ZnFe2O4 composite material is coated on the micro-thermal electrode plate.
Preferably, the micro-heating electrode plate comprises a supporting film, a heater is fixed on the supporting film, an isolating film is covered on the heater, and interdigital electrodes are arranged on the isolating film.
Preferably, the BP/ZnFe2O4 composite material is coated on the surface of the interdigital electrode.
Preferably, in the BP/ZnFe2O4 composite material, the mass ratio of BP to ZnFe2O4 is 1:180-1:200.
Preferably, a calculation formula of a response value of the acetone sensor to acetone with a certain concentration is Ra/Rg, wherein Rg is a stable resistance value of the acetone sensor with a certain concentration, and Ra is a stable resistance value of the acetone sensor in dry air.
The BP material refers to Black Phosphorus (BP) which is an allotrope of elemental phosphorus.
The invention also discloses a preparation method of the acetone gas sensor, which is characterized by comprising the following steps of:
Step 1, respectively dispersing zinc acetate dihydrate and ferric chloride with preset mass into ethanol and glycol with preset volume to form mixed solution, and dispersing BP into absolute ethanol to obtain BP-absolute ethanol dispersion;
Step 2, mixing and stirring the mixed solution obtained in the step 1 and BP-absolute ethyl alcohol dispersion liquid to obtain a doped mixed solution;
step 3, adding the doped mixed solution obtained in the step 2 into the inner lining of the reaction kettle to perform hydrothermal reaction;
step 4, centrifuging the doped mixed solution subjected to the hydrothermal reaction, repeatedly washing with absolute ethyl alcohol, and then placing the mixed solution into a vacuum drying box for drying to obtain a BP/ZnFe2O4 composite material;
And 5, dispersing the BP/ZnFe2O4 composite material obtained in the step 4 in a solvent by adopting a dripping method, dripping the BP/ZnFe2O4 composite material on the surface of the micro-hot electrode plate, and then carrying out vacuum drying treatment on the micro-hot electrode plate to obtain the acetone gas sensor taking the BP/ZnFe2O4 composite material as a gas sensitive layer.
Preferably, the preset weight part range of zinc acetate dihydrate in the step1 is 0.8-0.9, the preset weight part range of ferric chloride is 1.2-1.3, the preset weight part range of ethanol is 22-24, the preset weight part range of ethylene glycol is 7-9, and the purities of ethanol and ethylene glycol are all more than or equal to 99.7%.
Preferably, in the doping mixed solution, the mass ratio of BP to ZnFe2O4 is 1:180-1:200.
Preferably, the micro-thermal electrode plate in the step 5 comprises a supporting film, a heater is fixed on the supporting film, an isolating film is covered on the heater, an interdigital electrode is arranged on the isolating film, and the BP/ZnFe2O4 composite solution obtained in the step 4 is dripped on the surface of the interdigital electrode.
The invention has the following beneficial effects:
1. Compared with the signal of single ZnFe2O4 gas sensitive material, the BP/ZnFe2O4 composite material is used as a gas sensitive layer of the acetone gas sensor, the signal of the BP/ZnFe2O4 composite gas sensitive material formed under the doping of the proper BP material is introduced to accelerate the electron transfer speed of the gas sensitive material, increase oxygen vacancies and specific surface area, increase the adsorption sites of gas molecules and promote the adsorption and diffusion of the gas molecules in a sensitive film, thereby improving the adsorption/desorption speed and response strength of the sensor.
2. The acetone gas sensor prepared by the invention has larger response to the acetone gas with the gas concentration in the range of 100 ppb-2 ppm, and has low detection limit;
3. The acetone gas sensor prepared by the invention has high sensitivity, and the response Ra/Rg of the acetone gas sensor to 500ppb is about 5.34;
4. The acetone gas sensor prepared by the invention has fast response and the response time to 500ppb of acetone is 6s;
5. The acetone gas sensor prepared by the invention has the advantages of unique morphology, clustered shape, uniform size and good physical morphology.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, the following describes an acetone gas sensor and a preparation method thereof in detail with reference to the accompanying drawings.
The invention solves the technical problems that the existing acetone detection technology is difficult to distinguish the weak change of the acetone concentration (100 ppb-2 ppm) in the low-concentration acetone environment, and has higher responsivity and sensitivity.
Based on the technical problems to be solved, as shown in fig. 1, the invention discloses an acetone gas sensor, which comprises a micro-thermal electrode plate, wherein a gas sensitive layer formed by BP/ZnFe2O4 composite material is coated on the micro-thermal electrode plate.
The micro-thermal electrode plate comprises a supporting film, a heater is fixed on the supporting film, an isolating film is covered on the heater, an interdigital electrode is arranged on the isolating film, and the BP/ZnFe2O4 composite material is coated on the surface of the interdigital electrode.
In the BP/ZnFe2O4 composite material, the mass ratio of BP to ZnFe2O4 is 1:180-1:200, and the mass ratio of BP to ZnFe2O4 is 1:193.
When the gas sensitive layer is coated, 100 mu L of absolute ethyl alcohol is added into 10mg of BP/ZnFe2O4 composite material to prepare paste, and the paste is coated on the surface of the interdigital electrode.
The calculation formula of the response value of the acetone sensor to acetone with a certain concentration is Ra/Rg, wherein Rg is a stable resistance value of the acetone sensor with a certain concentration, and Ra is a stable resistance value of the acetone sensor in dry air.
The BP material refers to Black Phosphorus (BP) which is an allotrope of elemental phosphorus.
The invention also discloses a preparation method of the acetone gas sensor, which comprises the following steps:
Step 1, respectively dispersing zinc acetate dihydrate and ferric chloride with preset mass into ethanol and glycol with preset volume to form mixed solution, and dispersing BP into absolute ethanol to obtain BP-absolute ethanol dispersion;
Step 2, mixing and stirring the mixed solution obtained in the step 1 and BP-absolute ethyl alcohol dispersion liquid to obtain a doped mixed solution;
step 3, adding the doped mixed solution obtained in the step 2 into the inner lining of the reaction kettle, and carrying out hydrothermal reaction at 180 ℃;
step 4, centrifuging the doped mixed solution subjected to the hydrothermal reaction, repeatedly washing with absolute ethyl alcohol, and then placing the mixed solution into a vacuum drying box for drying to obtain a BP/ZnFe2O4 composite material;
And 5, dispersing the BP/ZnFe2O4 composite material obtained in the step 4 in an ethanol solvent by adopting a dripping method, dripping the BP/ZnFe2O4 composite material on the surface of a micro-hot electrode plate, and then carrying out vacuum drying treatment on the micro-hot electrode plate to obtain the acetone gas sensor taking the BP/ZnFe2O4 composite material as a gas sensitive layer.
The zinc acetate dihydrate in the step 1 is 0.8-0.9 in preset weight part, ferric chloride is 1.2-1.3 in preset weight part, ethanol is 22-24 in preset weight part, ethylene glycol is 7-9 in preset weight part, and the purities of ethanol and ethylene glycol are more than or equal to 99.7%. In the concrete implementation, the weight of the zinc acetate dihydrate and the weight of the ferric chloride are respectively 0.878g and 1.298g, and the volumes of ethanol and ethylene glycol are respectively 30ml and 8ml according to parts by weight and corresponding density conversion.
Preferably, in step 3, the hydrothermal reaction time is 12 hours.
In the step 4, the drying temperature of the vacuum drying box is 80 ℃ and the drying time is 12 hours.
Wherein, the ethanol in the step 5 is absolute ethanol, and the purity of the solvent is more than or equal to 99.7 percent.
The micro-heating electrode plate in the step 5 comprises a supporting film, a heater is fixed on the supporting film, an isolating film is covered on the heater, an interdigital electrode is arranged on the isolating film, and the BP/ZnFe2O4 composite solution obtained in the step 4 is dripped on the surface of the interdigital electrode.
Example 1
The acetone gas sensor is prepared by the following method, and comprises the following steps:
step 1, dispersing 0.878g of zinc acetate dihydrate and 1.298g of ferric chloride in 30ml of absolute ethyl alcohol and 8ml of ethylene glycol, mixing the above materials, and dispersing 5mgBP in 5ml of absolute ethyl alcohol to obtain BP-absolute ethyl alcohol dispersion;
step 2, mixing the solutions obtained in the step 1, and stirring at a speed of 700r/min for 10min to obtain a doped mixed solution;
step 3, adding the doped mixed solution obtained in the step 2 into a lining of a 100ml reaction kettle, and carrying out hydrothermal reaction at 180 ℃;
Step 4, centrifuging the doped mixed solution subjected to the hydrothermal reaction, repeatedly washing for 3-4 times by using absolute ethyl alcohol, and then placing the mixed solution into a vacuum drying box for drying for 12 hours at 80 ℃ to obtain a BP/ZnFe2O4 composite material;
and 5, dispersing the BP/ZnFe2O4 composite material obtained in the step 4 in an ethanol solvent by adopting a dripping method, dripping the BP/ZnFe2O4 composite material on the surface of a micro-hot electrode plate, and then carrying out vacuum drying (45 ℃) treatment on the micro-hot electrode plate for 90 minutes to obtain the acetone gas sensor taking the BP/ZnFe2O4 composite material as a gas sensitive layer.
In the doping mixed solution in the step 2, the mass ratio of BP to ZnFe2O4 is as follows:
BP:ZnFe2O4=5 mg:0.96 g。
in the step3, the hydrothermal reaction time is 12h.
As shown by the characterization of FIG. 2 SEM, the BP/ZnFe2O4 composite condition in the prepared material is good, wherein the flaky BP is tightly adhered to spherical ZnFe2O4 particles.
And detecting acetone gas by using an acetone gas sensor of the obtained BP/ZnFe2O4 composite material, wherein a schematic diagram of detecting acetone by using a BP/ZnFe2O4 device is shown in fig. 3, and the obtained results are shown in fig. 4 to 7.
As can be seen from FIG. 4, the acetone gas sensor of the BP/ZnFe2O4 composite material has good repeatability under the lower acetone environment, namely, the acetone gas concentration is 100ppb, wherein the response is defined as Ra/Rg, rg is the stable resistance value of the acetone sensor under the condition of a certain concentration of acetone, and Ra is the stable resistance value of the acetone sensor under the condition of dry air.
As shown in FIG. 5, the acetone gas sensor of the BP/ZnFe2O4 composite material has faster response and recovery time (6 s/63 s) and good sensitivity when detecting low-concentration acetone in an acetone gas concentration environment of 500 ppb.
As shown in FIG. 6, the acetone gas sensor of the BP/ZnFe2O4 composite material is tested under the environment of different concentrations of acetone gas, and the result is that the acetone gas sensor has good concentration gradient for detecting the acetone gas under the environment of different concentrations of acetone gas.
As shown in fig. 7, when the acetone gas concentration is in the range of 100ppb to 1.5ppm, the acetone gas sensor of the BP/ZnFe2O4 composite material has good sensitivity (slope of 0.006/ppb) and linearity (r2 =0.98) for detecting low-concentration acetone.
As shown in fig. 8, the real-time response of the acetone gas sensor of the BP/ZnFe2O4 composite material to 100ppb acetone at different Relative Humidities (RH) under different conditions (12% RH to 68% RH) is shown in fig. 8a and 8b, respectively, and fig. 8c is a comparison of the responses in both cases. With the increase of RH value, the reaction of the acetone gas sensor of the BP/ZnFe2O4 composite material to acetone is slightly enhanced, and the response of adding 100ppb of acetone is improved by about 2 times compared with pure humidity although the water vapor concentration under the test condition is far higher than that of acetone, so that the acetone gas sensor has good moisture resistance and good detection characteristic under a humid environment, and has higher practical application potential. Meanwhile, as shown in fig. 8d, the acetone sensor also shows good long-term stability (discrete coefficient cv=5.4%) over 34 days.
In addition, one application example of the acetone gas sensor is disclosed herein, and the acetone gas sensor disclosed by the invention is used for detecting the content of acetone in human expiration. It should be noted that the acetone gas sensor disclosed in the present invention can be applied to multiple occasions, and is not limited to this application example. As shown in fig. 9, the acetone gas sensor disclosed by the invention has good performance of detecting the acetone content in human expiration under the condition of a simulated pathological individual (such as diabetes).
Firstly, simulating the expiration states of healthy individuals and sick individuals, wherein the simulated expiration of the normal individuals comprises 75% of nitrogen, 20% of oxygen, 4% of carbon dioxide (volume percent) and water vapor brought by the carbon dioxide gas flowing through a gas flowmeter. The expiration of the sick individual was increased by acetone gas compared to the expiration of a normal individual.
Four acetone concentrations 100, 300, 500, 700ppb were then selected for testing, five consecutive respiratory cycles were tested consecutively, as shown in fig. 9b, the baseline resistance was selected to be the stable resistance under simulated normal expiration, and the dynamic response results of the sensor are shown in fig. 9 c. It can be seen that the response of the sensor increases with increasing acetone concentration and shows better sensitivity (slope of 0.003/ppb) and linearity (r2 =0.93) as shown in fig. 9 d. This also demonstrates that the acetone gas sensor disclosed by the invention has good detection performance on weak acetone gas in expiration of a sick individual.
The acetone gas sensor and the preparation method thereof have the technical effects that the acetone gas sensor prepared by the invention has unique morphology, is clustered, has uniform size and has good physical morphology. Compared with the signal of a single ZnFe2O4 gas-sensitive material, the signal of the BP/ZnFe2O4 composite material formed under the doping of a proper BP material leads the electron transfer speed of the gas-sensitive material to be accelerated along with the introduction of BP, the oxygen vacancy is increased, the specific surface area is increased, the adsorption site of gas molecules is increased, and the adsorption and diffusion of the gas molecules in a sensitive film are promoted, thereby improving the adsorption/desorption speed and the response strength of the sensor. The acetone gas sensor prepared by the invention has larger response to the acetone gas with the gas concentration within the range of 100 ppb-2 ppm, and has low detection limit. The acetone gas sensor prepared by the invention has high sensitivity and has response Ra/Rg of about 5.34 to 500ppb acetone. The acetone gas sensor prepared by the invention has fast response and the response time to 500ppb acetone is 6s. The acetone gas sensor prepared by the invention has good moisture resistance and good detection characteristic in a humid environment, the response to 100ppb acetone in the humid environment is improved by about 2 times compared with the response to pure humidity, and the acetone gas sensor has great practical application potential. The acetone gas sensor prepared by the invention has good long-term stability, and the response discrete coefficient CV=5.4% in 34 days. The acetone gas sensor prepared by the invention has the advantages of unique morphology, clustered shape, uniform size and good physical morphology.
It will be understood that the application has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the application without departing from the essential scope thereof. Therefore, it is intended that the application not be limited to the particular embodiment disclosed, but that the application will include all embodiments falling within the scope of the appended claims.