Materials and detection methods for carbon dioxide concentration detection

Abstract

This invention belongs to the field of gas detection technology. A method for detecting carbon dioxide concentration involves increasing the effective optical path using a diffuse reflection microcubic cavity, the surface of which is coated with a high diffuse reflection material; a fluorescent probe material is disposed on the surface of the high diffuse reflection material, and activated carbon material is disposed on the surface of the fluorescent probe material; by characterizing the luminescence intensity under different carbon dioxide concentration conditions, the carbon dioxide concentration detection accuracy is high.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology and relates to a method for detecting carbon dioxide concentration based on fluorescent materials. Background Technology

[0002] Carbon dioxide is a colorless and odorless gas with the molecular formula CO2. The chemical bonds within its molecule are typically covalent bonds. Solid carbon dioxide is widely used in the refrigeration of dairy products, meat, frozen foods, and other perishable foods during transport. In industrial processing, it acts as a refrigerant, such as in metal cold treatment, shrink-fit assembly of mechanical parts, and vacuum cold traps. Gaseous carbon dioxide is used in the carbonization of soft drinks, pH control in water treatment processes, chemical processing, food preservation, inert protection in chemical and food processing, welding gases, and as a plant growth stimulant. In foundry processes, it is used as a diluent for sterilizing gases and is widely used in the sterilization of medical devices, packaging materials, clothing, fur, and bedding. Liquid carbon dioxide is used as a refrigerant to improve oil well recovery and can also be used as a fire extinguishing agent. Supercritical carbon dioxide can be used as a solvent to dissolve nonpolar, nonionic, and low molecular weight compounds, thus finding wide application in homogeneous reactions. Therefore, the detection of carbon dioxide concentration is crucial, as different concentrations produce different effects.

[0003] Compared with other detection technologies, fluorescence-based detection techniques have the following advantages: 1. Excellent selectivity; 2. No damage to the test environment, and adaptability to various extreme conditions; 3. Scanning is usually completed within seconds, and measurement does not require sampling or preprocessing, resulting in a fast reaction process. This invention proposes using a fluorescent probe co-doped with ytterbium and neodymium ions, employing a diffuse reflection picocubic cavity as the gas absorption cell to increase the effective optical path and improve the sensitivity of low-concentration carbon dioxide detection. Based on this, the carbon dioxide concentration is detected by utilizing changes in fluorescence intensity. Summary of the Invention

[0004] The purpose of this invention is to disclose a method for detecting carbon dioxide concentration, which uses a diffuse reflection microcubic cavity as a gas sample cell to extend the effective optical path, adsorbs carbon dioxide through activated carbon coated on the surface, and uses a fluorescent probe co-doped with ytterbium ions and neodymium ions.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A method for detecting carbon dioxide concentration involves increasing the effective optical path using a diffuse reflection microcube cavity, the surface of which is coated with a high diffuse reflection material; a fluorescent probe material is disposed on the surface of the high diffuse reflection material, and an activated carbon material is disposed on the surface of the fluorescent probe material; carbon dioxide concentration is detected by characterizing the luminescence intensity under different carbon dioxide concentration conditions.

[0007] As a preferred option, the high diffuse reflectance material is Avian-D coating; the activated carbon material is coconut shell activated carbon or bamboo charcoal activated carbon. The fluorescent probe material is co-doped with ytterbium and neodymium ions.

[0008] Materials used for carbon dioxide concentration detection include fluorescent probe materials, the molecular formula of which is Sc2Mo3O. 12 :Ca / Yb / Nd. The fluorescent probe material has activated carbon material on its surface. The preparation method of the fluorescent probe material includes the following steps:

[0009] (1) According to the molar percentage, 0.65 mmol scandium nitrate, 0.2 mmol ytterbium nitrate, 0.1 mmol neodymium nitrate and 0.05 mmol calcium nitrate were dissolved in 4 mL of deionized water and heated and stirred until all the raw materials were dissolved to obtain a transparent mixed solution;

[0010] (2) Dissolve 2 mmol of ammonium molybdate and 3 mmol of citric acid in 4 mL of deionized water and add them to the solution obtained in step (1);

[0011] (3) The mixed solution is heated in a water bath at 80 degrees Celsius, and the mixed solution becomes a sol;

[0012] (4) The sol was dried at 120 degrees Celsius for 24 h to obtain a gel;

[0013] (5) After grinding the gel thoroughly in a mortar, keep it at 800 degrees Celsius for 3 hours. After the reaction is complete, the product is obtained.

[0014] Molecular formula of fluorescent probe material: Sc2Mo3O 12 :Ca / Yb / Nd. 980 nm incident photons are sensitized by Yb 3+ After ion absorption, the activated Nd ions are filled through a phonon-assisted energy transfer process. 3+ The excited state energy level of Ca is thus achieved, thereby realizing upconversion luminescence. 2+ Ion doping can significantly improve upconversion luminescence intensity and lower the laser excitation threshold, enabling low-power excitation of carbon dioxide concentration detection. As the carbon dioxide adsorption concentration increases, the phonon-assisted energy transfer efficiency decreases, leading to a weakening of luminescence intensity. By characterizing the upconversion luminescence intensity under different carbon dioxide concentration conditions, high-precision carbon dioxide concentration detection can be achieved. Attached Figure Description

[0015] Figure 1 Example: Sc2Mo3O 12 X-ray diffraction pattern of Ca / Yb / Nd;

[0016] Figure 2 Example: Sc2Mo3O 12Upconversion luminescence spectra of Ca / Yb / Nd;

[0017] Figure 3 Example: Sc2Mo3O 12 Integral curves of upconversion luminescence intensity of Ca / Yb / Nd under different carbon dioxide concentrations;

[0018] Figure 4 In diffuse reflection microcavities, Example Sc2Mo3O 12 Integral curves of upconversion luminescence intensity of Ca / Yb / Nd under different carbon dioxide concentrations;

[0019] Figure 5 Comparative example: Sc2Mo3O 12 Upconversion luminescence spectra of Ca / Yb / Er;

[0020] Figure 6 In a diffuse reflection microcavity, comparative example Sc2Mo3O 12 Integral curves of upconversion luminescence intensity of Ca / Yb / Er under different carbon dioxide concentrations. Detailed Implementation

[0021] The following is combined Figure 1-6 The present invention will be further described below. Example

[0022] A method for detecting carbon dioxide concentration involves increasing the effective optical path using a diffuse reflection microcube cavity, the surface of which is coated with a high diffuse reflection material; a fluorescent probe material is disposed on the surface of the high diffuse reflection material, and an activated carbon material is disposed on the surface of the fluorescent probe material; carbon dioxide concentration is detected by characterizing the luminescence intensity under different carbon dioxide concentration conditions.

[0023] Optical path extension technology: In order to improve the sensitivity of gas concentration detection, this system uses a diffuse reflection microcubic cavity to increase the effective optical path. The inner surface is coated with a high diffuse reflection material, and the effective optical path is increased by utilizing the diffuse reflection of light on the inner surface of the integrating sphere.

[0024] Coating of fluorescent probe material inside the microcubic cavity: The fluorescent probe material is coated on the surface of the microcubic cavity, and then activated carbon material is coated on the surface of the fluorescent material. The excitation light source is input and the emitted light is output using an optical fiber. The concentration of carbon dioxide is determined by the change in the intensity of the output light.

[0025] The high diffuse reflection material is Avian-D coating. The activated carbon material is bamboo charcoal, specifically fruit shell activated carbon or bamboo charcoal activated carbon.

[0026] Preparation of fluorescent probe materials: The molecular formula of the fluorescent probe material is Sc2Mo3O 12The preparation method of Ca / Yb / Nd includes the following steps: (1) Dissolve 0.65 mmol scandium nitrate, 0.2 mmol ytterbium nitrate, 0.1 mmol neodymium nitrate and 0.05 mmol calcium nitrate in 4 mL of deionized water by molar percentage, heat and stir with a magnetic stirrer to dissolve all raw materials to obtain a transparent mixed solution; (2) Dissolve 2 mmol ammonium molybdate and 3 mmol citric acid in 4 mL of deionized water and add them to the solution obtained in step (1); (3) Heat the mixed solution in a water bath at 80 degrees Celsius until it becomes a pale yellow sol; (4) Place the sol in an oven and dry it at 120 degrees Celsius for 24 h to obtain a yellow gel; (5) Grind the gel thoroughly in a mortar and keep it at 800 degrees Celsius for 3 hours. After the reaction is complete, the product is obtained.

[0027] Sc2Mo3O prepared by the above method 12 Ca / Yb / Nd probe material; powder X-ray diffraction analysis showed that the synthesized product was a pure orthorhombic phase. Figure 1 Nd2 was observed under 980 nm laser illumination. 3 Emission of ions in the near-infrared region ( Figure 2 Because Nd 3 Ions cannot absorb the energy of incident photons at 980 nanometers; their upconversion luminescence is achieved through an energy transfer process. Nd: 4 F 5 / 2 With Yb: 2 F 5 / 2 The energy difference between the two is compensated by the energy of the phonons. Therefore, the phonon energy of the matrix plays an important role in its upconversion luminescence efficiency.

[0028] like Figure 3 As shown, with the increase of carbon dioxide concentration around the probe material, Nd 3 The change in luminescence intensity of the ions was not significant because Sc2Mo3O 12 Ca / Yb / Nd probe materials cannot directly react with carbon dioxide. For example... Figure 4 As shown, Sc2Mo3O 12 The Ca / Yb / Nd probe material is coated on the inner surface of the microcubic cavity, and then activated carbon material, specifically bamboo charcoal activated carbon material, is coated on the surface of the fluorescent material. The excitation light source is input and the emitted light is output using an optical fiber. As the carbon dioxide concentration gradually increases, the upconversion luminescence intensity gradually decreases.

[0029] The principle of diffuse reflection microcubic cavities is similar to that of integrating spheres; both utilize diffuse reflection of light within their interiors to increase the effective optical path. This invention employs a common microcubic cavity, focusing on a fluorescent probe. In natural environments, the normal concentration of carbon dioxide in the air is 0.04% (400 ppm), reaching up to 500 ppm in large cities with heavy traffic. When carbon dioxide concentrations reach 1500-2000 PPM, people experience asthma, headaches, and dizziness. When the carbon dioxide concentration in office air reaches 2000 ppm, employees feel drowsy, have difficulty concentrating, and experience mental fatigue. Above 2000 PPM, cognitive abilities decline significantly. When the concentration exceeds 5000 PPM, severe bodily dysfunction occurs, leading to loss of consciousness and awareness. The detection system designed in this invention can effectively detect carbon dioxide concentrations within the range of 100-5000 ppm, demonstrating promising application prospects.

[0030] To further demonstrate the importance of activated carbon in this invention, the detection results were compared when there was no activated carbon coating. The results show that the fluorescence intensity change without activated carbon coating is similar to... Figure 3 Similarly, this demonstrates that coated activated carbon can effectively adsorb carbon dioxide, thereby enabling the carbon dioxide to interact with the fluorescent probe material, altering the upconversion luminescence intensity, and thus achieving the detection of carbon dioxide concentration.

[0031] To further demonstrate the importance of the phonon-assisted energy transfer upconversion luminescence mechanism in this invention, Sc2Mo3O 12 The Ca / Yb / Er probe material is a comparative example, and... Figure 4 A similar comparative experiment was conducted. For example... Figure 5 As shown, this comparative example exhibits strong upconversion luminescence under 980 nm near-infrared excitation, including both green and red emission bands. Figure 6 As shown, its luminescence intensity remains basically unchanged with the change of carbon dioxide concentration in the environment. This is because the upconversion luminescence process from Yb to Er is mainly achieved through two-photon energy transfer and is not affected by the carbon dioxide concentration.

Claims

1. A method for detecting carbon dioxide concentration, wherein the effective optical path is increased by using a diffuse reflection microcubic cavity, the surface of which is coated with a high diffuse reflection material; characterized in that... A fluorescent probe material is deposited on the surface of a high diffuse reflectance material, and activated carbon material is deposited on the surface of the fluorescent probe material. Carbon dioxide concentration is detected by characterizing the luminescence intensity under different carbon dioxide concentration conditions. The molecular formula of the fluorescent probe material is: Sc₂Mo₃O₃. 12 :Ca / Yb / Nd.

2. The carbon dioxide concentration detection method according to claim 1, characterized in that... The high diffuse reflection material is Avian-D coating.

3. The carbon dioxide concentration detection method according to claim 1, characterized in that... The activated carbon material is either fruit shell activated carbon or bamboo charcoal activated carbon.

4. The carbon dioxide concentration detection method according to claim 3, characterized in that... 980 nm incident photons are sensitized by Yb 3+ After ion absorption, the activated Nd ions are filled through a phonon-assisted energy transfer process. 3+ The excited state energy level is thus achieved, thereby realizing upconversion luminescence.

5. A material for detecting carbon dioxide concentration, characterized in that, The material includes a fluorescent probe material, the molecular formula of which is: Sc2Mo3O 12 :Ca / Yb / Nd; The surface of the fluorescent probe material is covered with activated carbon material.

6. The material for detecting carbon dioxide concentration according to claim 5, characterized in that... The preparation method of fluorescent probe materials includes the following steps: (1) According to the molar percentage, 0.65 mmol scandium nitrate, 0.2 mmol ytterbium nitrate, 0.1 mmol neodymium nitrate and 0.05 mmol calcium nitrate were dissolved in 4 mL of deionized water and heated and stirred until all the raw materials were dissolved to obtain a transparent mixed solution; (2) Dissolve 2 mmol of ammonium molybdate and 3 mmol of citric acid in 4 mL of deionized water and add them to the solution obtained in step (1); (3) The mixed solution is heated in a water bath at 80 degrees Celsius, and the mixed solution becomes a sol; (4) The sol was dried at 120 degrees Celsius for 24 h to obtain a gel; (5) After grinding the gel thoroughly in a mortar, keep it at 800 degrees Celsius for 3 hours. After the reaction is complete, the product is obtained.

Images