A volatile alcohol detection sensor, a preparation method and application thereof

Abstract

The present application relates to alcohol detection technology field, disclose a kind of volatile alcohol detection sensor and its preparation method and application.The preparation method steps include: the mixture of biomass carbon source, ammonium nitrate and zinc nitrate is pressed into sheet, placed in inert atmosphere, with 1~5 ℃ / min rate to 200~210 ℃, 30~60 min, then with 1~3 ℃ / min to 500~510 ℃, 60~90 min, finally with 10~13 ℃ / min to 950~960 ℃, 120~150 min, obtain porous carbon sheet;Two electrode sheets are attached to porous carbon sheet, and two electrode sheets are connected with voltage detection device by external lead, obtain volatile alcohol detection sensor.The preparation method of the present application can make the prepared sensor have higher mechanical stability, and can realize higher detection sensitivity in the detection of volatile alcohol substances.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alcohol detection, and in particular to a volatile alcohol detection sensor and a preparation method and application thereof. BACKGROUND

[0002] Evaporative power generation is a technology that converts the energy generated during natural evaporation into electrical energy. Its core principle is to use the physical and chemical changes caused by liquid evaporation to promote the separation of electric charges within the material, thereby generating an electric current. When liquid molecules evaporate from the surface of a porous material, the interaction between the vapor and the surface of the porous material causes a redistribution of electric charges, resulting in a voltage.

[0003] Powdered porous carbon materials, such as carbon black, are typical evaporative power generation materials. Due to their large specific surface area, simple preparation method, flexible modification method, and low cost, they provide a good foundation for the application of evaporative power generation technology in the field of sensors. By doping heteroatoms or adding functional groups to the porous carbon material, the size and polarity of the output voltage can be controlled.

[0004] However, in actual sensor applications, powdered carbon materials need to overcome the problem of long-term stability. Powdered carbon materials are generally attached to a substrate through deposition or coating, for example, in patent CN114323319B, flaky graphite, ethyl cellulose, alpha-terpineol, and alcohol are mixed and then applied to the surface of a medium material to form a thin layer. After drying and annealing, a conductive material layer is formed. In the above method, there is a lack of strong chemical bond between the powdered carbon material and the substrate, and the mechanical stability is low, which can be easily damaged by air flow, friction, or mechanical impact during the handling process, resulting in sensor failure and interruption of power output. SUMMARY

[0005] To solve the technical problem of poor mechanical stability of existing porous carbon material sensors based on the principle of evaporative power generation, the present application provides a volatile alcohol detection sensor and a preparation method and application thereof. The preparation method of the present application can make the prepared sensor have high mechanical stability and high detection sensitivity in the detection of volatile alcohol substances.

[0006] The specific technical solutions of the present application are as follows:

[0007] In a first aspect, the present application provides a preparation method of a volatile alcohol detection sensor, comprising the following steps: pressing a mixture of a biomass carbon source, ammonium nitrate and zinc nitrate into a sheet, and then placing the sheet in an inert atmosphere, and heating the sheet to 190-210 DEG C at a rate of 1-5 DEG C / min, and then heating the sheet to 480-540 DEG C at a rate of 1-3 DEG C / min, and then heating the sheet to 950-1000 DEG C at a rate of 10-13 DEG C / min, and then keeping the sheet at the temperature for 120-150 min to obtain a porous carbon sheet; and then adhering two electrode sheets to the porous carbon sheet, and connecting the two electrode sheets to a voltage detection device through external wires to obtain the volatile alcohol detection sensor.

[0008] The sensor of the present application is based on the potential difference generated between two electrodes by the evaporation potential of alcohol substances in the porous carbon sheet, and realizes the detection of volatile alcohol substances, and the specific mechanism is as follows: when the sample liquid to be detected contacts one end of the porous carbon sheet, the volatile alcohol molecules climb along the porous carbon sheet by capillary action. When the volatile alcohol molecules evaporate from the surface of the porous carbon sheet, direct intermolecular interaction occurs between the volatile alcohol molecules and the porous carbon sheet, which causes the carriers in the porous carbon sheet to transfer from one region to another region, thereby generating a voltage in the porous carbon sheet. The functional groups on the surface of the porous carbon sheet affect the electrical properties and voltage of the evaporation potential, and when the alcohol molecules are adsorbed onto these functional groups, electrons are transferred from the alcohol molecules to the porous carbon sheet, which causes the local charge to redistribute; when the alcohol molecules evaporate from the surface of the porous carbon sheet, these electrons gradually return to the alcohol molecules, which causes the local hole carrier concentration to increase, thereby generating a potential. The evaporation potential is mainly generated in the part of the wetting area before the capillary front, and this voltage is different from the classical streaming potential (the potential caused by the flow of liquid), and the evaporation potential is not dependent on the flow of liquid in the channel, but is directly generated by the evaporation process. The type and concentration of the volatile alcohol in the sample to be detected will affect the potential difference generated between the two electrodes, and based on this, the sensor of the present application can be used to detect the type and concentration of the volatile alcohol in the sample.

[0009] Compared with the method of depositing or coating a powder carbon material on a substrate in the prior art, in the process of preparing the sensor, the mixture of the biomass carbon source and the pore-forming agent (ammonium nitrate and zinc nitrate) is first pressed into a sheet, and then sintered to form a whole porous carbon material, which can solve the problem that the powder carbon material is easy to fall off from the substrate, and can realize good mechanical and chemical stability in long-term use, so that it can resist the erosion of various harsh environments including temperature, pressure, organic matter and oxidation.

[0010] However, compared with the deposition or coating method, the whole sintering method is prone to have lower porosity, which affects the detection sensitivity. In order to solve the above problems, the application adopts ammonium nitrate and zinc nitrate as the pore-forming agent, and cooperates with a special sintering procedure, which can improve the pore distribution in the prepared porous carbon sheet, thereby effectively improving the detection sensitivity of the sensor to volatile alcohol substances. Specifically, in the first stage sintering process (heated to 190-210 DEG C at a rate of 1-5 DEG C / min and kept for 30-60 min), ammonium nitrate is first decomposed to form interconnected diffusion pores in the system; in the second stage sintering process (heated to 480-540 DEG C at a rate of 1-3 DEG C / min and kept for 60-90 min), the carbon source is completely converted into coke, at the same time, zinc nitrate is thermally decomposed and converted into zinc oxide, accompanied by the escape of nitrogen dioxide and oxygen, which can further build a connected structure between the pores formed in the first stage sintering. According to the characteristics of the above reaction, a slower heating rate is used in this stage, which can avoid the collapse of the pores caused by the rapid decomposition of the carbon source precursor, and is beneficial to improve the microporosity; in the third stage sintering process (heated to 950-1000 DEG C at a rate of 10-13 DEG C / min and kept for 120-150 min), carbon thermal reduction reaction occurs, etching the carbon structure, at the same time, zinc oxide is reduced to zinc and vaporized, accompanied by the escape of CO, which can further improve the porosity. A faster heating rate is used in this stage, which is beneficial to produce a large amount of Zn vapor and CO gas in a short time, to generate higher instantaneous gas pressure in the carbon skeleton, and to create more micropores and mesopores in a "blasting" manner, thereby further improving the specific surface area and detection sensitivity.

[0011] In addition, the pore-forming agents ammonium nitrate and zinc nitrate used in the application can be removed during sintering, and the obtained porous carbon sheet is basically free of zinc impurity residues, eliminating the post-processing steps such as acid washing in the conventional plate method, which not only avoids the wastewater treatment problem and the damage of corrosive gas to the equipment, enhances the flexibility of the process, but also improves the safety of the process and reduces the health risk to the operators. Moreover, a large amount of functional group structures containing O, N and S heteroatoms in the biomass precursor can be retained in the porous carbon sheet after sintering, which can interact with alcohol molecules through the "double electric layer charging and discharging" process during the evaporation and power generation stage, thereby improving the detection sensitivity to alcohol molecules.

[0012] As an optional embodiment, the mass percentage of the biomass carbon source in the biomass carbon source, ammonium nitrate and zinc nitrate is 50-60%, and the mass ratio of ammonium nitrate to zinc nitrate is 1:2-3.

[0013] As an optional embodiment, the biomass carbon source includes one or more of starch, glucose, sucrose, cellulose, hemicellulose, lignin, chitosan, chitin and coconut shell.

[0014] As an optional implementation, after the pressing process is completed, the obtained sheet is a rectangular sheet with a width of 2-4 cm, a length of 7-13 cm, and a thickness of 0.3-0.7 cm.

[0015] As an optional implementation, the preparation step of the mixture of the biomass carbon source, ammonium nitrate and zinc nitrate comprises: mixing, stirring, heating the biomass carbon source, ammonium nitrate, zinc nitrate and a dispersion medium, and then performing grinding after the dispersion medium is completely evaporated; the dispersion medium comprises one or more of water, an alcohol liquid, an aldehyde liquid, an ether liquid, a ketone liquid and an ester liquid.

[0016] As an optional implementation, the inert atmosphere is one or more of nitrogen, argon and helium.

[0017] As an optional implementation, the material of the electrode sheet is one or more of gold, silver, platinum, aluminum, iron, copper, graphite, graphene, carbon nanotubes and conductive adhesive tape; and the voltage detection device is a picoammeter.

[0018] As an optional implementation, in the process of adhering the two electrode sheets to the porous carbon sheet, the two electrode sheets are adhered to the two ends of the same surface of the porous carbon sheet, and are packaged by using epoxy resin packaging glue, silicone packaging glue, polyurethane packaging glue or ultraviolet light curing packaging glue.

[0019] In a second aspect, the present application provides a volatile alcohol detection sensor prepared by the preparation method.

[0020] In a third aspect, the present application provides an application of the volatile alcohol detection sensor in detecting volatile alcohols.

[0021] As an optional implementation, the application step comprises: immersing one end of the volatile alcohol detection sensor into a sample liquid to be detected, so that one electrode sheet is immersed in the sample liquid to be detected, and the other electrode sheet is exposed to air, and an electrical signal displayed by a voltage detection device is read.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] (1) The present application adopts the method of pressing the mixture of the biomass carbon source and the porogen into a sheet and then sintering, to form a whole porous carbon material, which can improve the chemical and mechanical stability of the sensor, so that the sensor can still maintain the complete structure and maintain the potential difference output under long-term use or mechanical and chemical erosion.

[0024] (2) The application uses ammonium nitrate and zinc nitrate as a pore-forming agent, and cooperates with a special sintering procedure, so that the pore distribution in the porous carbon sheet can be improved, and the pore-forming agent can be removed more completely after sintering, while a large number of functional groups containing O, N and S heteroatoms in the biomass precursor are retained, so that the sensor can achieve high sensitivity in the detection of volatile alcohol substances. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the nitrogen adsorption-desorption curve of the porous carbon sheet obtained in Example 1.

[0026] Figure 2 is the pore size distribution curve of the porous carbon sheet obtained in Example 1.

[0027] Figure 3 is a schematic diagram of the device structure of the sensor of Example 1 for ethanol detection.

[0028] Figure 4 is a schematic diagram of the principle of the sensor of Example 1 for ethanol detection.

[0029] Figure 5 is a voltage-time signal diagram of the sensor of Example 1 for ethanol detection. DETAILED DESCRIPTION

[0030] The application will be further described below in conjunction with the drawings and examples.

[0031] First, the application relates to a preparation method of a volatile alcohol detection sensor, comprising the following steps: after a mixture of a biomass carbon source, ammonium nitrate and zinc nitrate is pressed into a sheet, the sheet is placed in an inert atmosphere, and then heated at a rate of 1-5 ℃ / min to 190-210 ℃ for 30-60 min, then heated at a rate of 1-3 ℃ / min to 480-540 ℃ for 60-90 min, and finally heated at a rate of 10-13 ℃ / min to 950-1000 ℃ for 120-150 min, to obtain a porous carbon sheet; two electrode sheets are attached to the porous carbon sheet, and the two electrode sheets are connected to a voltage detection device through external wires, to obtain a volatile alcohol detection sensor.

[0032] In some specific embodiments, the mass percentage of the biomass carbon source in the biomass carbon source, ammonium nitrate and zinc nitrate is 50-60%, and the mass ratio of ammonium nitrate to zinc nitrate is 1:2-3.

[0033] In some specific embodiments, the biomass carbon source includes one or more of starch, glucose, sucrose, cellulose, hemicellulose, lignin, chitosan, chitin and coconut shell.

[0034] In some embodiments, the preparation step of the mixture of the biomass carbon source, ammonium nitrate and zinc nitrate comprises: mixing and stirring the biomass carbon source, ammonium nitrate, zinc nitrate and a dispersion medium, and heating until the dispersion medium is completely evaporated, and then grinding. The dispersion medium comprises one or more of water, an alcohol liquid, an aldehyde liquid, an ether liquid, a ketone liquid and an ester liquid.

[0035] In some embodiments, after the pressing into a sheet is completed, the obtained sheet is a rectangular sheet with a width of 2-4 cm, a length of 7-13 cm and a thickness of 0.3-0.7 cm.

[0036] In some embodiments, the inert atmosphere is one or more of nitrogen, argon and helium.

[0037] In some embodiments, the material of the electrode sheet is one or more of gold, silver, platinum, aluminum, iron, copper, graphite, graphene, carbon nanotubes and conductive adhesive tape.

[0038] In some embodiments, the voltage detection device is a picoammeter.

[0039] In some embodiments, during the process of attaching the two electrode sheets to the porous carbon sheet, an epoxy encapsulation adhesive, a silicone encapsulation adhesive, a polyurethane encapsulation adhesive or a UV light-cured encapsulation adhesive is used for encapsulation.

[0040] In some embodiments, during the process of attaching the two electrode sheets to the porous carbon sheet, the two electrode sheets are respectively attached to the two ends of the same side of the porous carbon sheet.

[0041] Secondly, the present application relates to a volatile alcohol detection sensor prepared by the preparation method.

[0042] Thirdly, the present application relates to the application of the volatile alcohol detection sensor in detecting volatile alcohols.

[0043] In some embodiments, the application step comprises: immersing one end of the volatile alcohol detection sensor into a sample liquid to be detected, so that one electrode sheet is immersed in the sample liquid to be detected and the other electrode sheet is exposed to air, and reading the electrical signal displayed by the voltage detection device.

[0044] The present application is illustrated by specific examples and comparative examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

[0045] Example 1: Preparation of a volatile alcohol detection sensor

[0046] The volatile alcohol detection sensor of the present example is prepared by the following steps:

[0047] Step 1: 6 g of cellulose, 2 g of ammonium nitrate and 4 g of zinc nitrate powder were weighed and put into water and stirred and heated to 80°C. After the water was completely evaporated, the obtained solid was ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0048] Step 2: The rectangular sheet prepared in Step 1 was placed in a tube furnace and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia was 5:1, and the flow rate of the mixed gas was 30 mL / min) according to the following procedure: the temperature was raised to 200°C at a heating rate of 5°C / min and kept for 30 min; then the temperature was raised to 500°C at a heating rate of 1°C / min and kept for 60 min; then the temperature was raised to 950°C at a heating rate of 10°C / min and kept for 120 min; finally, the temperature was naturally cooled to room temperature to obtain a porous carbon sheet.

[0049] The porous carbon sheet prepared in this step was detected for specific surface area by nitrogen adsorption-desorption method, and the obtained nitrogen adsorption-desorption curve is shown in Figure 1 , and the measured specific surface area was 2325 m 2 / g; the pore size distribution calculated according to the BJH method is shown in Figure 2 , wherein it is shown that the high specific surface area of the porous carbon sheet is mainly contributed by micropores.

[0050] Step 3: Two electrode sheets of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, and the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet was 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet was also 0.2 cm; the contact area between the electrode sheets and the porous carbon sheet was encapsulated with an epoxy resin encapsulation glue, and the two electrode sheets were connected to a picoammeter through external leads to obtain a volatile alcohol detection sensor (structure as shown in Figure 3 ).

[0051] As shown in Figure 3 , the lower end of the sensor prepared in this example (together with one electrode sheet at the lower end) was immersed in ethanol, and the middle and upper end (together with one electrode sheet at the upper end) were exposed to air. The principle of the sensor for ethanol detection is shown in Figure 4 , when ethanol contacts the porous carbon sheet, capillary action drives ethanol to flow along the pore, and charge transfer occurs in the wet area at the front, resulting in a potential difference between the two electrodes, i.e. the voltage value read on the picoammeter. After immersing the lower end of the sensor in ethanol, the change of the voltage read on the picoammeter with time is shown in Figure 5 , and the output voltage after stabilization was about 0.8 V.

[0052] Example 2: Preparation of volatile alcohol detection sensor

[0053] The volatile alcohol detection sensor of this example was prepared by the following steps:

[0054] Step 1: Take 9 g of sucrose, 3 g of ammonium nitrate and 6 g of zinc nitrate powder, place them in water and stir to heat to 80°C. After the water completely evaporates, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0055] Step 2: Place the rectangular sheet prepared in Step 1 in a tube furnace, and under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia is 3:1, and the flow rate of the mixed gas is 30 mL / min), sinter according to the following program: heat to 190°C at a heating rate of 5°C / min, keep for 30 min; then heat to 480°C at a heating rate of 1°C / min, keep for 60 min; then heat to 950°C at a heating rate of 10°C / min, keep for 120 min; finally, naturally cool to room temperature to obtain a porous carbon sheet.

[0056] Step 3: Use aluminum-based conductive tape as electrode sheets, and adhere two electrode sheets to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, so that the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet is 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet is also 0.2 cm. The contact area between the electrode sheets and the porous carbon sheet is encapsulated using epoxy resin encapsulation glue, and the two electrode sheets are connected to the picoammeter through external leads to obtain a volatile alcohol detection sensor.

[0057] Example 3: Preparation of volatile alcohol detection sensor

[0058] The difference between this example and Example 1 is only that in Step 2, the parameter design in the sintering program is changed; the rest of the raw materials, preparation steps and sensor structure are the same as those of Example 1. The specific steps for preparing the volatile alcohol detection sensor of this example are as follows:

[0059] Step 1: Take 6 g of cellulose, 2 g of ammonium nitrate and 4 g of zinc nitrate powder, place them in water and stir to heat to 80°C. After the water completely evaporates, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0060] Step 2: Put the rectangular sheet prepared in Step 1 into a tube furnace, and sinter it under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia is 5:1, and the flow rate of the mixed gas is 30 mL / min) according to the following procedure: increase the temperature to 210°C at a heating rate of 5°C / min, and keep the temperature for 60 min; then increase the temperature to 540°C at a heating rate of 3°C / min, and keep the temperature for 90 min; then increase the temperature to 1000°C at a heating rate of 13°C / min, and keep the temperature for 150 min; finally, naturally cool to room temperature to obtain a porous carbon sheet.

[0061] Step 3: Use aluminum-based conductive adhesive tape as electrode sheets, and adhere two electrode sheets to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, so that the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet is 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet is also 0.2 cm. The contact area between the electrode sheets and the porous carbon sheet is packaged with epoxy resin packaging glue, and the two electrode sheets are connected to the picoammeter through external wires to obtain a volatile alcohol detection sensor.

[0062] Example 4: Preparation of a volatile alcohol detection sensor

[0063] The difference between this example and Example 1 is only that in Step 1, the ratio between ammonium nitrate and zinc nitrate is changed; the remaining raw materials, preparation steps, and sensor structure are the same as those of Example 1. The specific steps for preparing the volatile alcohol detection sensor in this example are as follows:

[0064] Step 1: Take 6 g of cellulose, 1 g of ammonium nitrate, and 3 g of zinc nitrate powder, and place them in water and stir to heat to 80°C. After the water is completely evaporated, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm, and a thickness of 0.5 cm.

[0065] Step 2: Put the rectangular sheet prepared in Step 1 into a tube furnace, and sinter it under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia is 5:1, and the flow rate of the mixed gas is 30 mL / min) according to the following procedure: increase the temperature to 210°C at a heating rate of 5°C / min, and keep the temperature for 60 min; then increase the temperature to 540°C at a heating rate of 3°C / min, and keep the temperature for 90 min; then increase the temperature to 1000°C at a heating rate of 13°C / min, and keep the temperature for 150 min; finally, naturally cool to room temperature to obtain a porous carbon sheet.

[0066] Step 3: Two electrode pieces of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, with the distance between the upper electrode piece and the upper edge of the porous carbon sheet being 0.2 cm, and the distance between the lower electrode piece and the lower edge of the porous carbon sheet also being 0.2 cm. The contact area between the electrode pieces and the porous carbon sheet was encapsulated using an epoxy resin encapsulating glue, and the two electrode pieces were connected to the picoammeter through external wires, thereby obtaining a volatile alcohol detection sensor.

[0067] Example 5: Preparation of a volatile alcohol detection sensor

[0068] The difference between this example and Example 1 is only that in Step 1, the ratio between ammonium nitrate and zinc nitrate is changed; the remaining raw materials, preparation steps, and sensor structure are the same as in Example 1. The specific steps for preparing a volatile alcohol detection sensor in this example are as follows:

[0069] Step 1: 6 g of cellulose, 3 g of ammonium nitrate, and 1 g of zinc nitrate powder were weighed and placed in water and stirred and heated to 80°C. After the water completely evaporated, the obtained solid was ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm, and a thickness of 0.5 cm.

[0070] Step 2: The rectangular sheet prepared in Step 1 was placed in a tube furnace and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio of nitrogen to ammonia being 5:1, mixed gas flow being 30 mL / min) according to the following program: heating to 200°C at a rate of 5°C / min, holding for 30 min; then heating to 500°C at a rate of 1°C / min, holding for 60 min; then heating to 950°C at a rate of 10°C / min, holding for 120 min; finally, naturally cooling to room temperature, thereby obtaining a porous carbon sheet.

[0071] Step 3: Two electrode pieces of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, with the distance between the upper electrode piece and the upper edge of the porous carbon sheet being 0.2 cm, and the distance between the lower electrode piece and the lower edge of the porous carbon sheet also being 0.2 cm. The contact area between the electrode pieces and the porous carbon sheet was encapsulated using an epoxy resin encapsulating glue, and the two electrode pieces were connected to the picoammeter through external wires, thereby obtaining a volatile alcohol detection sensor.

[0072] Example 6: Preparation of a volatile alcohol detection sensor

[0073] The difference between this example and Example 1 is only that in Step 1, the ratio between ammonium nitrate and zinc nitrate is changed; the remaining raw materials, preparation steps, and sensor structure are the same as in Example 1. The specific steps for preparing a volatile alcohol detection sensor in this example are as follows:

[0074] Step 1: 6 g of cellulose, 0.5 g of ammonium nitrate and 5.5 g of zinc nitrate powder were weighed and placed in water and heated to 80°C with stirring. After the water was completely evaporated, the obtained solid was ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0075] Step 2: The rectangular sheet prepared in Step 1 was placed in a tube furnace and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia was 5:1, and the flow rate of the mixed gas was 30 mL / min) according to the following procedure: the temperature was raised to 200°C at a heating rate of 5°C / min and maintained for 30 min; then the temperature was raised to 500°C at a heating rate of 1°C / min and maintained for 60 min; then the temperature was raised to 950°C at a heating rate of 10°C / min and maintained for 120 min; finally, the temperature was naturally cooled to room temperature, and a porous carbon sheet was obtained.

[0076] Step 3: Two aluminum-based conductive adhesive tapes were used as electrode sheets, which were respectively adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, and the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet was 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet was also 0.2 cm. The contact area between the electrode sheet and the porous carbon sheet was packaged with epoxy resin packaging glue, and the two electrode sheets were connected to the picoammeter through external wires, and a volatile alcohol detection sensor was obtained.

[0077] Preparation of a volatile alcohol detection sensor

[0078] The volatile alcohol detection sensor of the present comparative example was prepared by the following steps:

[0079] Step 1: Toluene was ignited in an alcohol lamp and placed above the flame, and carbon black from incomplete combustion was collected on a glass sheet. After the carbon black was evenly attached to the glass sheet, the glass sheet was annealed in air at 400°C for 1 hour and treated with air plasma for 3 minutes to obtain a glass sheet covered with a carbon black layer.

[0080] Step 2: Two aluminum-based conductive adhesive tapes were used as electrode sheets, which were respectively adhered to the upper and lower ends of the surface of the carbon black layer, and the distance between the electrode sheet at the upper end and the upper edge of the carbon black layer was 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the carbon black layer was also 0.2 cm. The contact area between the electrode sheet and the carbon black layer was packaged with dimethyl silicone optical glue, and the two electrode sheets were connected to the voltmeter through external wires, and a volatile alcohol detection sensor was obtained.

[0081] Preparation of a volatile alcohol detection sensor

[0082] The difference between this comparative example and Example 1 is only that in Step 1, the zinc nitrate is replaced by an equal amount of ammonium nitrate; the remaining raw materials, preparation steps, and sensor structure are the same as in Example 1. The specific steps for preparing the volatile alcohol detection sensor in this comparative example are as follows:

[0083] Step 1 : 6 g of cellulose and 6 g of zinc nitrate powder are weighed and placed in water and stirred and heated to 80°C. After the water is completely evaporated, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm, and a thickness of 0.5 cm.

[0084] Step 2: The rectangular sheet prepared in Step 1 is placed in a tube furnace and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia is 5:1, and the flow rate of the mixed gas is 30 mL / min) according to the following program: the temperature is raised to 200°C at a heating rate of 5°C / min, and then the temperature is raised to 500°C at a heating rate of 1°C / min, and then the temperature is raised to 950°C at a heating rate of 10°C / min, and then the temperature is kept at 950°C for 120 min; finally, it is naturally cooled to room temperature to obtain a porous carbon sheet.

[0085] Step 3: Two aluminum-based conductive adhesive tapes are used as electrode sheets, and the two electrode sheets are adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, so that the distance between the electrode sheet located at the upper end and the upper edge of the porous carbon sheet is 0.2 cm, and the distance between the electrode sheet located at the lower end and the lower edge of the porous carbon sheet is also 0.2 cm. The contact area between the electrode sheet and the porous carbon sheet is packaged with epoxy resin packaging glue, and the two electrode sheets are connected to the picoammeter through external leads to obtain a volatile alcohol detection sensor.

[0086] Comparative Example 3: Preparation of a volatile alcohol detection sensor

[0087] The difference between this comparative example and Example 1 is only that in Step 1, the zinc nitrate is replaced by an equal amount of ammonium nitrate; the remaining raw materials, preparation steps, and sensor structure are the same as in Example 1. The specific steps for preparing the volatile alcohol detection sensor in this comparative example are as follows:

[0088] Step 1 : 6 g of cellulose and 6 g of zinc nitrate powder are weighed and placed in water and stirred and heated to 80°C. After the water is completely evaporated, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm, and a thickness of 0.5 cm.

[0089] Step 2: The rectangular sheet prepared in step 1 was placed in a tube furnace, and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia was 5:1, and the flow rate of the mixed gas was 30 mL / min) according to the following procedure: the temperature was raised to 200°C at a heating rate of 5°C / min, and maintained for 30 min; then the temperature was raised to 500°C at a heating rate of 1°C / min, and maintained for 60 min; then the temperature was raised to 950°C at a heating rate of 10°C / min, and maintained for 120 min; finally, the temperature was naturally cooled to room temperature, to obtain a porous carbon sheet.

[0090] Step 3: Two electrode sheets of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in step 2, respectively, so that the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet was 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet was also 0.2 cm; the contact area between the electrode sheets and the porous carbon sheet was encapsulated using an epoxy resin encapsulating glue, and the two electrode sheets were connected to a picoammeter through external wires, to obtain a volatile alcohol detection sensor.

[0091] Comparative Example 4: Preparation of a volatile alcohol detection sensor

[0092] The difference between this comparative example and Example 1 is only that in step 2, the three-step sintering procedure was changed to one-step sintering; the remaining raw materials, preparation steps, and sensor structure were the same as in Example 1. The specific steps for preparing the volatile alcohol detection sensor in this comparative example are as follows:

[0093] Step 1: 6 g of cellulose, 2 g of ammonium nitrate, and 4 g of zinc nitrate powder were weighed out, placed in water, and stirred and heated to 80°C. After the water completely evaporated, the obtained solid was ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm, and a thickness of 0.5 cm.

[0094] Step 2: The rectangular sheet prepared in step 1 was placed in a tube furnace, and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia was 5:1, and the flow rate of the mixed gas was 30 mL / min) according to the following procedure: the temperature was raised to 200°C at a heating rate of 5°C / min, and maintained for 30 min; then the temperature was raised to 500°C at a heating rate of 1°C / min, and maintained for 60 min; then the temperature was raised to 950°C at a heating rate of 10°C / min, and maintained for 120 min; finally, the temperature was naturally cooled to room temperature, to obtain a porous carbon sheet.

[0095] Step 3: Two electrode sheets of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in step 2, respectively, so that the distance between the electrode sheet at the upper end and the upper edge of the porous carbon sheet was 0.2 cm, and the distance between the electrode sheet at the lower end and the lower edge of the porous carbon sheet was also 0.2 cm; the contact area between the electrode sheets and the porous carbon sheet was encapsulated using an epoxy resin encapsulating glue, and the two electrode sheets were connected to a picoammeter through external wires, to obtain a volatile alcohol detection sensor.

[0096] Preparation of volatile alcohol detection sensor

[0097] The difference between this comparative example and Example 1 is only that in Step 2, the heating rate in the second stage of the sintering process is accelerated; the rest of the raw materials, preparation steps and sensor structure are the same as Example 1. The specific steps for preparing the volatile alcohol detection sensor in this comparative example are as follows:

[0098] Step 1: Take 6 g of cellulose, 2 g of ammonium nitrate and 4 g of zinc nitrate powder, place them in water and stir to heat to 80°C. After the water is completely evaporated, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0099] Step 2: Place the rectangular sheet prepared in Step 1 in a tube furnace, and under the protection of a mixed gas of nitrogen and ammonia (volume ratio between nitrogen and ammonia is 5:1, and the flow rate of the mixed gas is 30 mL / min), sinter according to the following program: heat to 200°C at a heating rate of 5°C / min, keep for 30 min; then heat to 500°C at a heating rate of 5°C / min, keep for 60 min; then heat to 950°C at a heating rate of 10°C / min, keep for 120 min; finally, naturally cool to room temperature to obtain a porous carbon sheet.

[0100] Step 3: Use aluminum-based conductive adhesive tape as electrode sheets, and adhere two electrode sheets to the upper and lower ends of the same side of the porous carbon sheet obtained in Step 2, so that the distance between the electrode sheet located at the upper end and the upper edge of the porous carbon sheet is 0.2 cm, and the distance between the electrode sheet located at the lower end and the lower edge of the porous carbon sheet is also 0.2 cm. The contact area between the electrode sheet and the porous carbon sheet is packaged with epoxy resin packaging glue, and the two electrode sheets are connected to the picoammeter through external leads to obtain a volatile alcohol detection sensor.

[0101] Preparation of volatile alcohol detection sensor

[0102] The difference between this comparative example and Example 1 is only that in Step 2, the heating rate in the third stage of the sintering process is slowed down; the rest of the raw materials, preparation steps and sensor structure are the same as Example 1. The specific steps for preparing the volatile alcohol detection sensor in this comparative example are as follows:

[0103] Step 1: Take 6 g of cellulose, 2 g of ammonium nitrate and 4 g of zinc nitrate powder, place them in water and stir to heat to 80°C. After the water is completely evaporated, the obtained solid is ground and then molded into a rectangular sheet with a width of 2.5 cm, a length of 7.5 cm and a thickness of 0.5 cm.

[0104] Step 2: The rectangular sheet prepared in step 1 was placed in a tube furnace and sintered under the protection of a mixed gas of nitrogen and ammonia (volume ratio of nitrogen to ammonia was 5:1, and the flow rate of the mixed gas was 30 mL / min) according to the following procedure: heating to 200°C at a rate of 5°C / min, holding for 30 min; then heating to 500°C at a rate of 1°C / min, holding for 60 min; then heating to 950°C at a rate of 5°C / min, holding for 120 min; and finally naturally cooling to room temperature to obtain a porous carbon sheet.

[0105] Step 3: Two electrode sheets made of aluminum-based conductive adhesive tape were adhered to the upper and lower ends of the same side of the porous carbon sheet obtained in step 2, with the electrode sheet at the upper end being 0.2 cm away from the upper edge of the porous carbon sheet and the electrode sheet at the lower end being 0.2 cm away from the lower edge of the porous carbon sheet. The contact area between the electrode sheets and the porous carbon sheet was encapsulated using an epoxy resin encapsulation adhesive, and the two electrode sheets were connected to a picoammeter through external wires to obtain a volatile alcohol detection sensor.

[0106] Test Example 1: Mechanical stability test

[0107] The sensors prepared according to the methods of Examples 1-6 and Comparative Example 1 were subjected to a mechanical stability test, and the test method was as follows:

[0108] (1) Liquid scouring test: The liquid scouring test was designed to evaluate the structural stability and performance retention of the sensor surface when exposed to liquid scouring, especially alcohol solvents and their mixtures. The scouring media were deionized water, deionized water / ethanol mixture (volume ratio 1:1), and ethanol. The tests were divided into three groups according to the scouring medium, and each group was repeated three times. In each experiment, a standard needle with an inner diameter of 0.5 mm was used to scour the sensor surface at a distance of 10 mm, and the flow rate was controlled by a constant flow pump at 20 mL / min. The single scouring process consisted of 10 cycles of 30 s liquid scouring → 5 min standing and drying → dry air blowing to dry the surface. After drying, the test was performed and the average value was recorded.

[0109] (2) External force scratching test: The external force scratching test was designed to evaluate the ability of the sensor sensing area to resist mechanical scratching and wear, simulating scenarios such as installation, cleaning, or daily friction. The scratching tool was a polypropylene plastic blade with a tip radius of 0.5 mm, simulating accidental scratching of hard plastic. The scratching speed was 5 cm / s, and the sensor surface was pushed at an angle of 45° for about 5 cm. The sensor performance was tested after each scratch, and the average value of 5 tests was recorded.

[0110] The surface morphology of the porous carbon sheet was observed before and after liquid flushing or external force scraping, and was used for ethanol detection, as follows: the lower end of the sensor (together with an electrode sheet located at the lower end) was immersed in ethanol, the middle and upper end (together with an electrode sheet located at the upper end) was exposed to air, and the voltage was recorded after the reading of the picoammeter was stable. The results are shown in Table 1.

[0111] Table 1: Results of mechanical stability test

[0112]

[0113] According to the test results in Table 1, it can be seen that:

[0114] The sensor of Comparative Example 1 showed cracking and peeling of the carbon black layer after liquid flushing or external force scraping, and the output voltage was interrupted, indicating poor mechanical stability. The surface structure of the sensors of Examples 1-6 was not damaged after liquid flushing or external force scraping, and the output voltage was basically unchanged, indicating that the method of pressing the mixture of biomass carbon source and pore-forming agent into a sheet and then sintering in the present application can effectively improve the mechanical stability of the sensor.

[0115] Test Example 2: Sensitivity test

[0116] The sensors prepared according to the methods of the respective examples and comparative examples were taken for sensitivity test, and the test method was as follows:

[0117] A series of ethanol / cyclohexane standard mixtures with different proportions were prepared, the lower end of the sensor (together with an electrode sheet located at the lower end) was immersed in the ethanol / cyclohexane standard mixture, the middle and upper end (together with an electrode sheet located at the upper end) was exposed to air, and the response relationship between the output voltage and the ethanol concentration was tested, and the sensitivity (ratio between the output voltage and the ethanol concentration) was calculated. During the test, the sensor was fixed on a support to ensure that it was immersed in the same position and depth each time, and the voltage after the output was stable was recorded. Before changing the concentration, the sensor was quickly washed with anhydrous ethanol and dried with nitrogen to avoid cross contamination, and each concentration was tested 5 times. The ethanol concentration was taken as the abscissa, the response signal ΔV was taken as the ordinate, a scatter plot was drawn, and linear regression analysis was performed.

[0118] The sensitivity was tested in the ethanol concentration range of 0-10%vol, and a strong concentration-voltage response was shown. The test results are shown in Table 2.

[0119] Table 2: Results of sensitivity test

[0120]

[0121] According to the test results in Table 2, it can be seen that:

[0122] (1) The sensor sensitivity of Example 1 and Example 4 is higher than that of Example 5 and Example 6, and is higher than that of Comparative Example 2 and Comparative Example 3. It is shown that, compared with using single ammonium nitrate or zinc nitrate as a pore-forming agent, using the two in combination can make the prepared sensor have higher detection sensitivity, and the ratio between ammonium nitrate and zinc nitrate will affect the above effect. The reason is that, with the special sintering procedure in the application, ammonium nitrate can first decompose to form connected diffusion pores in the system; then zinc nitrate is thermally decomposed into zinc oxide, which further builds a connected structure between the pores formed in the first stage sintering, while avoiding the rapid decomposition of the carbon source precursor and the rapid escape of the gas generated by the thermal decomposition of zinc nitrate, which leads to pore collapse; finally, the zinc oxide is reduced into zinc and gasified, and escapes with CO, which can further improve the porosity.

[0123] (2) The sensor sensitivity of Example 1 is obviously higher than that of Comparative Example 4. It is shown that, compared with one-step sintering, the three-step sintering method used in the application is helpful to give the sensor higher detection sensitivity. The reason is that, when one-step sintering is used, it is difficult to well control the speed of the decomposition and release of gas by the biomass carbon source and zinc nitrate and ammonium nitrate in each stage, which is prone to cause problems such as pore collapse and inappropriate pore size, thereby affecting the detection of volatile alcohols by the sensor.

[0124] (3) The sensor sensitivity of Example 1 is obviously higher than that of Comparative Example 5. It is shown that, by using a slower heating rate in the second stage sintering process, the prepared sensor can have higher detection sensitivity. The reason is that, in the second stage sintering process, the carbon source is completely converted into coke, and at the same time, zinc nitrate is thermally decomposed and converted into zinc oxide, accompanied by the escape of nitrogen dioxide and oxygen. For the characteristics of the above reaction, using a slower heating rate in this stage can avoid the rapid decomposition of the carbon source precursor leading to pore collapse, which is beneficial to improve the microporosity.

[0125] (4) The sensor sensitivity of Example 1 is obviously higher than that of Comparative Example 6. It is shown that, by using a faster heating rate in the third stage sintering process, the prepared sensor can have higher detection sensitivity. The reason is that, in the third stage sintering process, a carbonthermal reduction reaction occurs, etching the carbon structure, and at the same time, the zinc oxide is reduced into zinc and gasified, and escapes with CO, which can further improve the porosity. Using a faster heating rate in this stage is beneficial to produce a large amount of Zn vapor and CO gas in a short time, to generate a higher instantaneous gas pressure inside the carbon skeleton, and to "blow up" to create more micropores and mesopores, thereby further improving the specific surface area and detection sensitivity.

Claims

1. A method for preparing a volatile alcohol detection sensor, characterized by, The steps comprise: After the mixture of the biomass carbon source, ammonium nitrate and zinc nitrate is pressed into a sheet, the sheet is placed in an inert atmosphere, heated to 190-210 DEG C at a rate of 1-5 DEG C / min, kept for 30-60 min, then heated to 480-540 DEG C at a rate of 1-3 DEG C / min, kept for 60-90 min, and finally heated to 950-1000 DEG C at a rate of 10-13 DEG C / min, kept for 120-150 min, to obtain a porous carbon sheet; two electrode sheets are attached to the porous carbon sheet, and the two electrode sheets are connected to a voltage detection device through external wires, to obtain a volatile alcohol detection sensor; the mass ratio of ammonium nitrate to zinc nitrate is 1:2-3.

2. The production method according to claim 1, characterized by, In the biomass carbon source, ammonium nitrate and zinc nitrate, the mass fraction of the biomass carbon source is 50-60%.

3. The production method according to claim 1 or 2, characterized by, The biomass carbon source includes one or more of starch, glucose, sucrose, cellulose, hemicellulose, lignin, chitosan, chitin and coconut shell.

4. The production method according to claim 1, characterized by, After the pressing into a sheet process is completed, the obtained sheet is a rectangular sheet with a width of 2-4 cm, a length of 7-13 cm and a thickness of 0.3-0.7 cm.

5. The production method according to claim 1 or 2, characterized by, The preparation steps of the mixture of the biomass carbon source, ammonium nitrate and zinc nitrate include: mixing and stirring the biomass carbon source, ammonium nitrate, zinc nitrate and a dispersion medium, and heating until the dispersion medium is completely evaporated, and then grinding; the dispersion medium includes one or more of water, alcohol liquid, aldehyde liquid, ether liquid, ketone liquid and ester liquid.

6. The method of claim 1, wherein, The material of the electrode sheet is one or more of gold, silver, platinum, aluminum, iron, copper, graphite, graphene, carbon nanotube and conductive tape; and the voltage detection device is a picoammeter.

7. The preparation method according to claim 1, characterized in that, In the process of attaching the two electrode sheets to the porous carbon sheet, the two electrode sheets are respectively attached to the two ends of the same side of the porous carbon sheet, and are packaged using epoxy resin packaging glue, silicone packaging glue, polyurethane packaging glue or ultraviolet light curing packaging glue.

8. A volatile alcohol detection sensor prepared by the preparation method of any one of claims 1-7.

9. The use of the volatile alcohol detection sensor of claim 8 in detecting volatile alcohols.

10. Use according to claim 9, characterized in that, The steps comprise: One end of the volatile alcohol detection sensor is immersed in the sample liquid to be detected, so that one electrode sheet is immersed in the sample liquid to be detected and the other electrode sheet is exposed to air, and the electrical signal displayed by the voltage detection device is read.

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