Normal-temperature ammonia gas sensor based on porous cuprous sulfide nanosheet and preparation method of normal-temperature ammonia gas sensor

Abstract

The invention discloses a normal-temperature ammonia gas sensor based on a porous cuprous sulfide nanosheet and a preparation method of the normal-temperature ammonia gas sensor, and relates to the technical field of environmental monitoring. The invention discloses a preparation method of a normal-temperature ammonia gas sensor based on a porous cuprous sulfide nanosheet. The preparation method comprises the following steps: coating the surface of a sensing substrate with a solution containing a porous cuprous sulfide nanosheet material, and drying to obtain the ammonia gas sensor. The two-dimensional copper oxysulfide nanosheet material layer formed by the invention has a large surface area and good normal-temperature gas molecule physical adsorption characteristic, does not need an additional excitation source, can be applied to a normal-temperature ammonia gas sensor, and shows strong response sensitivity, restorability, selectivity and long-term stability to low-concentration ammonia gas.

Description

Technical Field

[0001] The invention relates to the technical field of environmental monitoring, and in particular to a room-temperature ammonia sensor based on porous cuprous oxysulfide nanosheets and a preparation method thereof. Background Art

[0002] Ammonia is a toxic gas widely used in industry. It is colorless and has a pungent odor. It is irritating and corrosive to the upper respiratory tract of animals or humans. It is often adsorbed on the skin, mucous membranes and conjunctiva, causing irritation and inflammation. If a person inhales 700 mg˙m -3 Continuing for 30 minutes can be moderate, inhalation 1750-4000mg˙m -3 It can endanger life. There are three sources of ammonia in the atmosphere: one is biological nitrogen fixation, through which nitrogen in the atmosphere enters the ecological cycle system, and the amount of ammonia produced by biological nitrogen fixation accounts for 1 Tg / a of the total global ammonia emissions; the second is ammoniation, including agriculture, wildlife, decomposition of leaves and other processes, the released ammonium ions and gaseous ammonia are synthesized by bacteria into nitrite and nitrate, and the total global ammonia emissions come from ammoniation, accounting for 20-35 Tg / a; the third is from the chemical industry and motor vehicles, and the ammonia in this process mainly comes from the chemical production of fertilizers and refrigeration processes.

[0003] According to the national standard for hazardous occupational exposure limits in the workplace, the maximum allowable concentration of ammonia in the workshop is 50ppm. However, in fields such as environmental analysis, chemical industry, and medical applications, the required ammonia detection concentration must be lower than this limit. Therefore, the development of ammonia sensors with low detection limits is very necessary. Summary of the invention

[0004] The purpose of the present invention is to provide a room-temperature ammonia sensor based on porous cuprous sulfur oxide nanosheets and a preparation method thereof, to solve the following technical problems:

[0005] The existing ammonia sensor has low response sensitivity to low concentration ammonia.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of a room-temperature ammonia sensor based on porous cuprous oxysulfide nanosheets, wherein a solution containing a porous cuprous oxysulfide nanosheet material is coated on the surface of a sensing substrate and then dried to obtain an ammonia sensor;

[0008] The preparation method of the porous cuprous sulfide oxide nanosheet material comprises the following steps:

[0009] S1: Mix the copper nitrate solution and the thiourea solution and add them into a reaction kettle, and heat them to react to obtain a copper sulfide precursor solution;

[0010] S2: The precursor solution is cooled and centrifuged to obtain the supernatant, the supernatant is added with deionized water and centrifuged again, and the supernatant is obtained, and this step is repeated 2-4 times to obtain copper sulfide;

[0011] S3: Copper sulfide is calcined in nitrogen, ultrasonically crushed, and centrifugally purified to obtain porous cuprous sulfur oxide nanosheet material.

[0012] As a further solution of the present invention: the sensing substrate includes any one of interdigital electrodes and field effect transistors.

[0013] As a further solution of the present invention: the addition ratio of the porous cuprous oxide sulfide nanosheet material and anhydrous ethanol in the solution containing the porous cuprous oxide sulfide nanosheet material is 1 g:5 mL.

[0014] As a further solution of the present invention: the copper nitrate solution in S1 is obtained by mixing 0.8-1g of copper nitrate with 1000mL of deionized water; and the thiourea solution is obtained by mixing 1-1.5g of thiourea with 100mL of ethanol.

[0015] As a further solution of the present invention: the addition ratio of copper nitrate to thiourea in S1 is 1g:1-1.4g.

[0016] As a further solution of the present invention: the specific steps of the temperature raising reaction in S1 are: controlling the temperature at 125-155° C. and reacting for 9-12 hours.

[0017] As a further solution of the present invention: the specific steps of the calcination treatment are: under the condition of inputting 10-20 sccm nitrogen, calcining the copper sulfide at 200-300° C. for 2-3 hours.

[0018] As a further solution of the present invention: the specific steps of ultrasonic pulverization are: 4-6 mg of the copper sulfide calcined material is mixed with 25 mL of ethanol, and ultrasonic pulverized for 30-35 minutes.

[0019] A room-temperature ammonia sensor based on porous cuprous oxysulfide nanosheets is prepared by any one of the above preparation methods.

[0020] Beneficial effects of the present invention:

[0021] The two-dimensional copper oxysulfide nanosheet material layer formed by the present invention has a large surface area and good physical adsorption characteristics of gas molecules at room temperature. It does not require an additional excitation source and can be applied to a room-temperature ammonia sensor. It exhibits strong response sensitivity, recovery, selectivity and long-term stability for low-concentration ammonia (3ppm). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings.

[0023] Figure 1This is a transmission electron microscope (TEM) image of the porous cuprous oxysulfide nanosheet material prepared in Example 1 of the present application;

[0024] Figure 2 This is a scanning electron microscope (SEM) characterization image of the porous cuprous oxysulfide nanosheet material prepared in Example 1 of the present application;

[0025] Figure 3 This is the X-ray transmission photoelectron spectroscopy Cu2p spectrum of the porous cuprous sulfide oxide nanosheet material prepared in Example 1 of the present application;

[0026] Figure 4 This is the X-ray transmission photoelectron spectrum S2p spectrum of the porous cuprous sulfide oxide nanosheet material prepared in Example 1 of the present application;

[0027] Figure 5 This is the ultraviolet absorption spectrum of the porous cuprous sulfide oxide nanosheet material prepared in Example 1 of the present application;

[0028] Figure 6 The energy band gap of the material can be obtained by performing Tauc diagram calculation and deduction on the porous cuprous sulfide oxide nanosheet material prepared in Example 1 of the present application;

[0029] Figure 7 This is a statistical graph of the gas sensitivity test results of the porous cuprous sulfur oxide nanosheet room temperature ammonia sensor prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1 The preparation method of porous cuprous sulfide oxide nanosheet material comprises the following steps:

[0032] S1: 1 g of copper nitrate was mixed with 1000 mL of deionized water to obtain a copper nitrate solution; 1 g of thiourea was mixed with 100 mL of ethanol to obtain a thiourea solution; the copper nitrate solution and the thiourea solution were stirred at 100 pm for 30 min, and then added into a reaction kettle, the temperature was controlled at 140° C., and the reaction was carried out for 10 h to obtain a copper sulfide precursor solution;

[0033] S2: The precursor solution was centrifuged at 4000 rpm for 15 min at room temperature, the supernatant was taken, deionized water was added to the supernatant, and the supernatant was centrifuged at 10000 rpm for 15 min, and the supernatant was taken, and this step was repeated twice to obtain copper sulfide;

[0034] S3: Under the condition of inputting 10 sccm nitrogen, 50 mg of copper sulfide was calcined at 200°C for 2 h to obtain a calcined material to achieve a specific concentration of oxygen and sulfur atom replacement. 5 mg of the calcined material was mixed with 25 mL of anhydrous ethanol and ultrasonically crushed for 30 min, and centrifuged for purification to obtain a porous cuprous sulfur oxide nanosheet material.

[0035] A method for preparing a room-temperature ammonia sensor based on porous cuprous sulfur oxide nanosheets comprises the following steps:

[0036] A1: Mix 1 g of porous cuprous sulfide oxide nanosheet material with 5 mL of anhydrous ethanol to obtain a solution;

[0037] A2: The solution was dropped onto the surface of the interdigital electrode and dried naturally for 24 hours, so that the surface of the interdigital electrode contained 4 mg of porous cuprous sulfur oxide nanosheets per square millimeter, thereby obtaining an ammonia sensor.

[0038] Performance Testing

[0039] (1) Observation by transmission electron microscope

[0040] Depend on Figure 1 It can be seen that the porous cuprous sulfide oxide nanosheet material synthesized in the present application is in the form of a translucent nanosheet, with an average sheet width greater than 50 nm and a thickness of about 10 nm.

[0041] (2) Observation by scanning electron microscope

[0042] Depend on Figure 2 It can be seen that the porous cuprous oxysulfide nanosheet material synthesized in the present application presents a porous structure in the self-polymerized form.

[0043] (3) Tested by X-ray transmission photoelectric spectrum

[0044] Depend on Figure 3 It can be seen that the porous cuprous sulfur oxide nanosheet material synthesized in the present application shows a characteristic peak of monovalent copper (Cu+) in the copper energy spectrum (Cu2p) test results.

[0045] Depend on Figure 4 It can be seen that the porous cuprous sulfur oxide nanosheet material synthesized in the present application presents the chemical bond energy of sulfur-oxygen in the sulfur energy spectrum (S2p).

[0046] (4) Tested by UV absorption spectrum

[0047] Depend on Figure 5 It can be seen that the porous cuprous oxysulfide nanosheet material synthesized in the present application exhibits an absorption peak in the visible light band.

[0048] (5) Calculate the band gap / bandgap width based on the UV absorption spectrum

[0049] according to Figure 5 After the Tauc diagram calculation and derivation, we get Figure 6 ,Depend on Figure 6 It can be seen that the energy band gap of the porous cuprous oxide sulfide nanosheet material synthesized in the present application is about 1.96 electron volts. It can be seen that the porous cuprous oxide sulfide nanosheet material prepared in the present application is a semiconductor material, and after contacting with external gas, the surface carrier concentration is easily changed by physical adsorption of specific gas, so it can be used as a medium for gas sensing at room temperature.

[0050] (6) Gas sensing performance

[0051] The WS-30A gas-sensitive test system was used for testing. The test environment was as follows: 3ppm and 5ppm ammonia were injected into the test chamber at room temperature and one atmosphere, and the saturated resistance value of the sensor exposed to the gas was detected and recorded. Then, in the recovery stage, the injection of ammonia was stopped and pure air was injected, and the sensor resistance recovered; and the response factor α was calculated according to the following formula:

[0052] α=(R NH3 –R Ai r) / R Ai r×100%

[0053] Where, α-response factor, %; R NH3 - saturation resistance value when the sensor is exposed to ammonia, Ω; RAi r- saturation resistance value in pure air, Ω;

[0054] Depend on Figure 7 It can be seen that the Y-axis in the figure uses the response factor to express the response degree of the sensor. It can be seen from the figure that the porous cuprous sulfur oxide nanosheet room temperature ammonia sensor prepared in this application shows strong response sensitivity and recovery to low concentration ammonia (3ppm).

[0055] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a room-temperature ammonia sensor based on porous cuprous sulfide oxide nanosheets, characterized in that: A solution containing porous cuprous oxysulfide nanosheet material is coated on the surface of a sensing substrate and then dried to obtain an ammonia sensor; The preparation method of the porous cuprous sulfide oxide nanosheet material comprises the following steps: S1: Mix the copper nitrate solution and the thiourea solution and add them into a reaction kettle, and heat them to react to obtain a copper sulfide precursor solution; S2: The precursor solution is cooled and centrifuged to obtain the supernatant, the supernatant is added with deionized water and centrifuged again, and the supernatant is obtained, and this step is repeated 2-4 times to obtain copper sulfide; S3: Copper sulfide is calcined in nitrogen, ultrasonically crushed, and centrifugally purified to obtain porous cuprous sulfur oxide nanosheet material.

2. The method for preparing a room temperature ammonia sensor based on porous cuprous oxysulfide nanosheets according to claim 1, characterized in that: The sensing substrate includes any one of an interdigital electrode and a field effect transistor.

3. The method for preparing a room temperature ammonia sensor based on porous cuprous sulfide oxide nanosheets according to claim 1, characterized in that: The addition ratio of the porous cuprous oxide sulfide nanosheet material and anhydrous ethanol in the solution containing the porous cuprous oxide sulfide nanosheet material is 1 g:5 mL.

4. The method for preparing a room temperature ammonia sensor based on porous cuprous oxysulfide nanosheets according to claim 1, characterized in that: The copper nitrate solution in S1 is obtained by mixing 0.8-1 g of copper nitrate with 1000 mL of deionized water; the thiourea solution is obtained by mixing 1-1.5 g of thiourea with 100 mL of ethanol.

5. The method for preparing a room temperature ammonia sensor based on porous cuprous sulfide oxide nanosheets according to claim 1, characterized in that: The addition ratio of copper nitrate to thiourea in S1 is 1g:1-1.4g.

6. The method for preparing a room temperature ammonia sensor based on porous cuprous oxysulfide nanosheets according to claim 1, characterized in that: The specific steps of the temperature-raising reaction in S1 are: controlling the temperature at 125-155° C. and reacting for 9-12 hours.

7. The method for preparing a room temperature ammonia sensor based on porous cuprous oxysulfide nanosheets according to claim 1, characterized in that: The specific steps of the calcination treatment are: calcining copper sulfide at 200-300° C. for 2-3 hours under the condition of inputting 10-20 sccm nitrogen.

8. The method for preparing a room temperature ammonia sensor based on porous cuprous oxysulfide nanosheets according to claim 1, characterized in that: The specific steps of the ultrasonic pulverization are: mixing 4-6 mg of the copper sulfide calcined material with 25 mL of ethanol, and ultrasonically pulverizing for 30-35 minutes.

9. A room temperature ammonia sensor based on porous cuprous sulfide oxide nanosheets, characterized in that: Prepared by the preparation method described in any one of claims 1 to 8.

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