A sensor material for ammonia detection and its preparation method and application

Abstract

The present invention discloses a sensor material for ammonia detection, its preparation method, and application. The preparation method comprises: dissolving raw materials including amino acids and siloxanes in water to prepare a carbon dot material source mixture, then performing a hydrothermal reaction, performing solid-liquid separation after the reaction to obtain a filtrate, then purifying the filtrate, and then drying. The preparation method uses siloxanes and amino acids as precursors to prepare a carbon dot material with special response properties to ammonia through a one-step hydrothermal method. The synthesis method is simple and convenient, the reaction conditions are mild, the raw material cost is low, and it is environmentally friendly. The prepared sensor material can respond quickly to ammonia gas at room temperature and has the advantages of high reaction sensitivity, low detection limit, and fast recovery speed.

Description

Technical Field

[0001] The present invention relates to the technical field of gas-sensitive materials, and in particular to a sensing material for ammonia detection, a preparation method thereof, and an application thereof. Background Art

[0002] While the rapid development of industry and agriculture in modern society has led to a rapid improvement in people's living standards, it has also caused a certain amount of environmental pollution. Among all types of environmental pollution, air pollution is of the greatest concern. Toxic and harmful gases in the air can harm our health every moment we breathe. Ammonia (NH3) is a gas with a density lower than that of air (0.771 g / L), a pungent odor, and toxicity. Detection or monitoring of NH3 is widely used in industrial production, animal husbandry, environmental protection, healthcare, and food safety. Ammonia is a strong irritant to skin tissue and, due to its high solubility, can irritate and even corrode the upper respiratory tract of humans and animals.

[0003] Ammonia is widely present in industrial production fields such as petrochemicals, steel foundries, and fertilizer production, and is also present in automobile exhaust. It is one of the most serious atmospheric pollutants that pose a serious threat to the environment and human health. my country stipulates that the concentration of NH3 in residential areas must not exceed 0.2 mg / m3. When the concentration of NH3 in the atmosphere reaches or exceeds 300 ppm, it will cause severe irritation and even corrosion to the skin in our respiratory tract. When people are exposed to large amounts of NH3, human cells, tissues, and organs will be severely damaged, causing symptoms such as tearing, difficulty breathing, dizziness, and fatigue. If excessive NH3 is inhaled, it will lead to high ammonia concentrations in the blood, which is life-threatening.

[0004] Due to the widespread presence and significant toxicity of ammonia, the development and research of ammonia sensors has long garnered significant attention. Currently, the main technologies for ammonia detection include spectroscopic methods, electrochemical methods, and solid-state sensors based on metal oxides or organic conductive materials. Optical methods for detecting NH3 offer the advantages of high accuracy, reliability, and low detection limits. However, optical equipment is typically expensive and bulky, making it unsuitable for widespread application. Electrochemical methods for detecting NH3 are the most mature, but they suffer from a narrow detection range, low accuracy, and the need for frequent calibration. Regarding gas-sensing materials, solid-state sensors based on metal oxides, while commercially available on a large scale and capable of achieving low detection limits and high sensitivity, require high operating temperatures (generally above 200°C), consume high energy, and are not easily miniaturized and integrated. Currently, the majority of materials used for ammonia sensing are organic conductive gas-sensing materials, such as polyaniline, polythiophene, polypyrrole, and their derivatives. While these sensing materials offer the advantages of high sensitivity and room-temperature operation, they also suffer from numerous limitations, such as poor long-term stability, selectivity, and recovery, making them far from convenient, fast, and flexible. Therefore, studying how to achieve high-sensitivity detection of ammonia at room temperature has become an important topic in the field of semiconductor ammonia gas sensors. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a sensing material for ammonia detection, a preparation method thereof, and an application thereof.

[0006] In a first aspect of the present invention, a method for preparing a sensing material for ammonia detection is provided, comprising the following steps:

[0007] S1. dissolving raw materials including at least one of amino acid and citric acid and at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine in water to prepare a carbon dot material source mixture;

[0008] S2, subjecting the carbon dot material source mixture to a hydrothermal reaction;

[0009] S3, separating the mixed solution after the reaction in step S2 into solid and liquid, taking the filtrate, and then purifying the filtrate and then drying it.

[0010] The method for preparing a sensor material for ammonia detection according to an embodiment of the present invention has at least the following beneficial effects: This method uses at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine, and at least one of amino acids and citric acid as precursors to prepare a carbon dot material with exceptional ammonia response properties via a one-step hydrothermal method. The synthesis method is simple and convenient, with mild reaction conditions, low raw material costs, and environmental friendliness. The sensor material prepared by this method can rapidly respond to ammonia gas at room temperature and exhibits high sensitivity, a low detection limit, and a fast recovery rate.

[0011] In some embodiments of the present invention, in step S1, the amino acid is selected from at least one of glycine and aspartic acid.

[0012] In some embodiments of the present invention, in step S1, the ratio of the mass of at least one of the amino acid and citric acid to the volume of at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine is (1-5): (100-2000) g / μL; preferably (2-3): (500-650) g / μL. Alternatively, the raw materials comprising at least one of the amino acid and citric acid and at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine can be uniformly dispersed by mixing with water using methods such as stirring, shaking, and physical ultrasound.

[0013] In some embodiments of the present invention, in step S2, the temperature of the hydrothermal reaction is 90-220° C., preferably 100-200° C., for example, 100° C., 120° C., 150° C., 160° C., 180° C., or 200° C. Preferably, the hydrothermal reaction time is 3-72 hours, preferably 3-24 hours, for example, 3 hours, 5 hours, 6 hours, 10 hours, 12 hours, 18 hours, or 24 hours.

[0014] In some embodiments of the present invention, in step S3, the solid-liquid separation is performed by microporous membrane filtration; preferably, the drying is performed by freeze drying. In addition, before performing the solid-liquid separation, the solution is generally cooled to room temperature.

[0015] In some embodiments of the present invention, in step S3, the purification process is dialysis. After the dialysis process, the dialysate is collected and then dried.

[0016] In a second aspect of the present invention, a sensing material for ammonia detection is provided, which is prepared by any one of the methods for preparing ammonia sensing materials provided in the first aspect of the present invention.

[0017] The third aspect of the present invention is the use of any one of the ammonia detection sensing materials proposed in the second aspect of the present invention in detecting ammonia gas.

[0018] In a fourth aspect of the present invention, a gas-sensitive electrode is provided, wherein a gas-sensitive coating is provided on the gas-sensitive electrode, and the material of the gas-sensitive coating includes any one of the ammonia detection sensing materials proposed in the second aspect of the present invention.

[0019] In a fifth aspect of the present invention, a sensor for detecting ammonia gas is provided, comprising any one of the gas-sensitive electrodes provided in the fourth aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0021] Figure 1 Schematic diagram of the process flow for the hydrothermal reaction of siloxane and amino acid in Example 1;

[0022] Figures 2a-2c The XRD patterns of the ammonia gas detection sensing materials prepared in Examples 1 to 3 are shown;

[0023] Figures 3a-3c TEM images of the ammonia gas detection sensing materials prepared in Examples 1 to 3;

[0024] Figures 4a-4c FTIR images of the ammonia gas detection sensing materials prepared in Examples 1 to 3;

[0025] Figures 5a-5c Graph showing the cyclic stability test results of the ammonia detection sensing materials prepared in Examples 1 to 3 for detecting ammonia;

[0026] Figures 6a-6c Graph showing the gas-sensitive response recovery test results of the ammonia detection sensing materials prepared in Examples 1 to 3 to ammonia of different concentrations;

[0027] Figure 7 This is a comparison chart of the gas-sensitive response test results of the ammonia detection sensor material prepared in Example 1 to different gases. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment prepares a sensing material for ammonia detection, which specifically includes the following steps:

[0031] S1. Weigh 492 μL of triethoxysilane and 2.1014 g of citric acid and dissolve them in 10 mL of deionized water. Ultrasonic vibration is used to obtain a uniformly dispersed carbon dot material source mixture.

[0032] S2, the carbon dot material source mixture prepared in step S1 was placed into a polytetrafluoroethylene high-pressure reactor lining with a capacity of 25 mL, and after tightening, it was transferred to a hydrothermal oven for hydrothermal reaction at a reaction temperature of 150 ° C and a reaction time of 6 h; the reaction of triethoxysilane and citric acid was as follows: Figure 1 As shown;

[0033] S3. Cool the mixed solution after the reaction in step S2 to room temperature, and then filter it with a microporous filter membrane to collect the filtrate; then place the filtrate in a dialysis bag, dialyze it for 48 hours, collect the dialysate, and finally freeze-dry it to obtain a sensing material for ammonia detection.

[0034] Example 2

[0035] This embodiment prepares a sensing material for ammonia detection, which specifically includes the following steps:

[0036] S1. Weigh 670 μL of N-[3-(trimethoxysilyl)propyl]ethylenediamine and 2.1014 g of aspartic acid and dissolve them in 10 mL of deionized water. Ultrasonicate to obtain a uniformly dispersed carbon dot material source mixture.

[0037] S2. The carbon dot material source mixture prepared in step S1 was placed into a 25 mL polytetrafluoroethylene autoclave liner, tightened, and transferred to a hydrothermal oven for hydrothermal reaction at a temperature of 150°C for 6 h.

[0038] S3. Cool the mixed solution after the reaction in step S2 to room temperature, and then filter it with a microporous filter membrane to collect the filtrate; then place the filtrate in a dialysis bag, dialyze it for 48 hours, collect the dialysate, and finally freeze-dry it to obtain a sensing material for ammonia detection.

[0039] Example 3

[0040] This embodiment prepares a sensing material for ammonia detection, which specifically includes the following steps:

[0041] S1. Weigh 670 μL of N-[3-(trimethoxysilyl)propyl]ethylenediamine and 1.3310 g of citric acid and dissolve them in 10 mL of deionized water. Ultrasonicate to obtain a uniformly dispersed carbon dot material source mixture.

[0042] S2. The carbon dot material source mixture prepared in step S1 was placed into a 25 mL polytetrafluoroethylene autoclave liner, tightened, and transferred to a hydrothermal oven for hydrothermal reaction at a temperature of 150°C for 6 h.

[0043] S3. Cool the mixed solution after the reaction in step S2 to room temperature, and then filter it with a microporous filter membrane to collect the filtrate; then place the filtrate in a dialysis bag, dialyze it for 48 hours, collect the dialysate, and finally freeze-dry it to obtain a sensing material for ammonia detection.

[0044] Comparative Example 1

[0045] In this comparative example, a sensing material for ammonia detection is prepared. The difference between this comparative example and Example 1 is that triethoxysilane is eliminated in this comparative example, and other operations are the same as those in Example 1.

[0046] Test example

[0047] The ammonia detection sensing materials prepared in Examples 1 to 3 were observed using an X-ray diffractometer, and the obtained XRD patterns were as follows: Figure 2a 、 Figure 2b and Figure 2c As shown. Figure 2a The XRD pattern shown shows the presence of characteristic peaks of carbon dot materials at 22° and 52°; Figure 2b The XRD pattern shown shows the characteristic peaks of carbon dot materials at 21° and 42°. Figure 2c The XRD pattern shown shows the presence of characteristic peaks of carbon dot materials at 22° and 43°, thereby proving that the ammonia detection sensing materials prepared in Examples 1 to 3 are carbon dot materials.

[0048] The ammonia gas detection sensing materials prepared in Examples 1 to 3 were observed and characterized using a transmission electron microscope. The results are shown in FIG. Figures 3a-3c As shown, Figures 3a-3c The TEM images show that the carbon dot materials prepared in each embodiment are evenly distributed and have uniform particle sizes. The transmission electron microscope photos further intuitively demonstrate the successful preparation of the carbon dot materials.

[0049] The ammonia detection sensing materials prepared in Examples 1 to 3 were observed and characterized using a Fourier transform infrared spectrometer. The results are shown in FIG. Figures 4a-4c shown. Figure 4aIn the FTIR spectrum shown, there is an absorption band near 3446 cm-1, which is attributed to the stretching vibration of C-OH; at 2354 cm-1 corresponds to the stretching vibration of OH; some vibration peaks near 1629 cm-1 correspond to the stretching vibration of C=O; there is a stretching vibration peak of Si-O-Si near 1100 cm-1; 964 cm-1 and 796 cm-1 correspond to the stretching vibration of Si-O bond. Figure 4b In the FTIR spectrum shown, there is an absorption band near 3410 cm-1, which is attributed to the stretching vibration of NH; at 2941 cm-1 corresponds to the stretching vibration of CH; some vibration peaks near 1710 cm-1 correspond to the stretching vibration of CO; there is a stretching vibration peak of -OH near 1419 cm-1; 1112 cm-1 corresponds to the stretching vibration of the CN bond; and there is a stretching vibration peak of Si-O near 719 cm-1. Figure 4c In the FTIR spectrum shown, there is an absorption band near 3423 cm-1, which is attributed to the stretching vibration of OH; at 2935 cm-1 corresponds to the stretching vibration of CH; some vibration peaks near 1647 cm-1 correspond to the stretching vibration of C=O; there is a stretching vibration peak of C-OH near 1392 cm-1; 1093 cm-1 corresponds to the stretching vibration of CO bond; there is a stretching vibration peak of Si-C near 914 cm-1; and there is a stretching vibration peak of Si-O-Si near 682 cm-1.

[0050] As can be seen from the above, the ammonia detection sensing material prepared by the preparation method in Examples 1 to 3 is a single carbon dot material having a carbon core or a surface containing precursor-related functional groups.

[0051] The above-mentioned ammonia gas detection sensing material can be applied to the detection of ammonia gas. Specifically, the above-mentioned ammonia gas detection sensing material can be used to prepare a gas-sensitive electrode, and then to prepare an ammonia gas detection sensor for detecting ammonia gas. For example, the above-mentioned ammonia gas detection sensing material can be used to prepare a gas-sensitive electrode, and then to prepare an ammonia gas detection sensor, which can specifically include the following steps:

[0052] 1) Dispersing a sensing material for ammonia detection in deionized water to obtain a sensing material dispersion;

[0053] 2) applying the sensing material dispersion prepared in step 1) to the surface of the test electrode, removing moisture from the sensing material dispersion applied to the test electrode, and forming a gas-sensitive coating on the surface of the test electrode to prepare a gas-sensitive electrode;

[0054] 3) Connecting the gas-sensitive electrode prepared in step 2) to an ammonia gas detection device to produce an ammonia gas detection sensor. Specifically, the ammonia gas detection sensor includes a gas-sensitive electrode having a gas-sensitive coating on its surface, wherein the gas-sensitive coating is made of the aforementioned ammonia gas detection sensing material.

[0055] The above ammonia detection sensor is used to detect ammonia gas to examine the gas sensitivity of the corresponding ammonia detection sensor material to ammonia. The specific detection method may include: a. Placing the gas-sensitive electrode in a sealed test chamber with air atmosphere and measuring its initial resistance (Ra). After stabilization, a certain concentration of ammonia gas is injected into the test chamber and the resistance change is recorded. After the response is stabilized (Rg), the test chamber is opened to restore the air atmosphere and the change in the gas-sensitive electrode resistance is recorded. The change in resistance is the response factor, which is equal to Ra / Rg.

[0056] First, the above method was used to test the cyclic stability of the sensor made of the ammonia detection sensing material in Example 1 at room temperature (26.3 ° C) and relative humidity of 40% RH, with a concentration of 5 ppm ammonia gas. The results are as follows: Figure 5a As shown. Figure 5a The results show that the ammonia gas detection sensing material prepared in Example 1 has a response multiple of 1.4 to 5 ppm ammonia gas at room temperature, and has good cyclic stability for ammonia gas detection.

[0057] The above method was used to test the cyclic stability of the sensor made of the ammonia detection sensing material in Example 2 under the conditions of room temperature (26.3°C) and relative humidity of 40% RH, with a concentration of 50 ppm ammonia gas. The results were as follows: Figure 5b As shown. Figure 5b The results show that the ammonia gas detection sensing material prepared in Example 2 has a response multiple of 1.2 to 50 ppm ammonia gas at room temperature, and its cyclic stability for ammonia gas detection is average.

[0058] The above method was used to test the cyclic stability of the sensor made of the ammonia detection sensing material in Example 3 under the conditions of room temperature (26.3°C) and relative humidity of 40% RH, with a concentration of 50 ppm ammonia gas. The results were as follows: Figure 5c As shown. Figure 5c The results show that the ammonia gas detection sensing material prepared in Example 3 has a response multiple of 1.08 to 50 ppm ammonia gas at room temperature, and has good cyclic stability for ammonia gas detection.

[0059] Secondly, at room temperature (26.3 ° C) and relative humidity of 43% RH, the sensor prepared by the ammonia detection sensing material of Example 1 was subjected to gas-sensitive response recovery tests on ammonia gas of different concentrations (1 ppm, 2 ppm and 3 ppm) to investigate the response and recovery performance of the sensing material to ammonia gas. The response results are shown in FIG. Figure 6a As shown. Figure 6a It can be seen that the detection limit of the sensing material in Example 1 is low, with the minimum detection of 1 ppm and a response multiple of 1.1. It has an extremely fast response speed, a fast recovery speed, good recovery, and a good linear relationship between the response value and the concentration.

[0060] At room temperature (26.3°C) and relative humidity of 43%RH, the sensor prepared by the ammonia detection sensing material of Example 2 was subjected to gas-sensitive response tests for ammonia gas of different concentrations (50ppm, 100ppm, 150ppm). The response results are shown in the figure below. Figure 6b As shown. Figure 6b It can be seen that the minimum detection concentration of the sensing material in Example 2 is 50 ppm, the response multiple is 1.2, and the linear relationship between the response value and the concentration is generally good.

[0061] At room temperature (26.3 ° C) and relative humidity of 43% RH, the sensor prepared by the ammonia detection sensing material of Example 3 was tested for gas-sensitive response to ammonia gas of different concentrations (50ppm, 100ppm, 150ppm). The response results are shown in the figure below. Figure 6c As shown. Figure 6c It can be seen that the minimum detection concentration of the sensing material in Example 3 is 50 ppm, the response multiple is 1.08, and the linear relationship between the response value and the concentration is good.

[0062] In addition, in order to verify the gas selectivity of the prepared ammonia detection sensing material, the sensor prepared by the ammonia detection sensing material of Example 1 was used to perform selectivity tests on ammonia with a concentration of 5 ppm and methanol, ethanol and acetone vapor with a concentration of 100 ppm, respectively, at room temperature (26.3 ° C) and a relative humidity of 40% RH. The results are shown in FIG. Figure 7 As shown. Figure 7 It can be seen that the response multiples of the ammonia detection sensing material of Example 1 to 100 ppm of methanol, ethanol and acetone vapor are 1.006, 1.062 and 1.061 respectively, and the response to a lower concentration (5 ppm) of ammonia is 1.4 times. It can be seen that the ammonia detection sensing material prepared in Example 1 has a specific response to ammonia.

[0063] The sensor prepared by using the ammonia detection sensing material of Comparative Example 1 was subjected to an ammonia gas-sensitive response recovery test similar to the above method. The test found that the ammonia detection sensing material prepared in Comparative Example 1 did not respond to ammonia.

[0064] As can be seen from the above, the method for preparing ammonia gas sensing materials in this application uses at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine, and at least one of amino acids and citric acid as precursors to prepare a carbon dot material with unique ammonia response properties through a one-step hydrothermal method. This synthesis method is simple and convenient, with mild reaction conditions, low raw material costs, and environmentally friendly properties. The sensing material prepared by this preparation method can respond rapidly to ammonia gas at room temperature and has the advantages of high reaction sensitivity, low detection limit, and fast recovery speed.

[0065] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. Application of a sensing material for ammonia detection in detecting ammonia gas, characterized in that: The ammonia detection sensing material is prepared by a preparation method comprising the following steps: S1. dissolving raw materials including at least one of amino acid and citric acid and at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine in water to prepare a carbon dot material source mixture; S2, subjecting the carbon dot material source mixture to a hydrothermal reaction; S3, separating the mixed solution after the reaction in step S2 into solid and liquid, taking the filtrate, and then purifying the filtrate and then drying it.

2. The use according to claim 1, characterized in that In step S1, the amino acid is selected from at least one of glycine and aspartic acid.

3. The use according to claim 1, characterized in that The ratio of the mass of at least one of the amino acid and citric acid to the volume of at least one of the triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine is (1-5):(100-2000) g / μL.

4. The use according to claim 1, characterized in that In step S2, the temperature of the hydrothermal reaction is 90-220°C.

5. The use according to claim 1, characterized in that In step S3, microporous membrane filtration is used for solid-liquid separation; and freeze-drying is used for drying.

6. The use according to any one of claims 1 to 5, characterized in that In step S3, the purification treatment is dialysis treatment.

7. A gas-sensitive electrode, characterized in that: The gas-sensitive electrode is provided with a gas-sensitive coating, and the material of the gas-sensitive coating includes a sensing material for ammonia detection; the sensing material for ammonia detection is prepared by a preparation method comprising the following steps: S1. dissolving raw materials including at least one of amino acid and citric acid and at least one of triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine in water to prepare a carbon dot material source mixture; S2, subjecting the carbon dot material source mixture to a hydrothermal reaction; S3, separating the mixed solution after the reaction in step S2 into solid and liquid, taking the filtrate, and then purifying the filtrate and then drying it.

8. The gas-sensing electrode according to claim 7, characterized in that: In step S1, the amino acid is selected from at least one of glycine and aspartic acid.

9. The gas-sensing electrode according to claim 7, characterized in that: The ratio of the mass of at least one of the amino acid and citric acid to the volume of at least one of the triethoxysilane, (3-aminopropyl)triethoxysilane, and N-[3-(trimethoxysilyl)propyl]ethylenediamine is (1-5):(100-2000) g / μL.

10. The gas sensing electrode according to claim 7, characterized in that: In step S2, the temperature of the hydrothermal reaction is 90-220°C.

11. The gas sensing electrode according to claim 7, characterized in that In step S3, microporous membrane filtration is used for solid-liquid separation; and freeze-drying is used for drying.

12. The gas sensing electrode according to any one of claims 7 to 11, characterized in that: In step S3, the purification treatment is dialysis treatment.

13. A sensor for detecting ammonia, characterized in that: The gas sensing electrode comprises the gas sensing electrode according to any one of claims 7 to 12.

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