Materials for detecting carbon dioxide concentration and preparation method thereof

Abstract

The present invention belongs to the technical field of gas detection. The material used for carbon dioxide concentration detection is a down-conversion fluorescent material sensitized by ytterbium ions, and the material is rare earth doped scandium molybdate with a surface coated with silicon dioxide. The molecular formula of the material is: Sc2Mo3O 12 :Li / Yb / Tm@SiO2. This patent is used for the material of carbon dioxide concentration detection, and the carbon dioxide concentration detection accuracy is high.

Description

Technical Field

[0001] The invention belongs to the technical field of gas detection and relates to a material for carbon dioxide concentration detection and a preparation method thereof. Background Art

[0002] Carbon dioxide is a colorless and odorless gas with a molecular formula of CO2. The chemical bonds within the molecule are usually covalent bonds. Gaseous carbon dioxide is used for carbonation of soft drinks, pH control of water treatment processes, chemical processing, food preservation, inert protection of chemical and food processing processes, welding gas, plant growth stimulant; used as a diluent for sterilizing gas in casting, and widely used in the sterilization of medical devices, packaging materials, clothing, fur and bedding. Carbon dioxide detection methods, such as the chemical method, pass the generated gas into clear lime water, the lime water becomes turbid, proving that the gas is carbon dioxide; combustion method, infrared gas analysis method, gas chromatography and volumetric titration method. These methods have problems such as complex analysis process, slow detection speed or high cost.

[0003] Detection technology based on fluorescent materials is widely used in the detection of temperature, biomolecules and pH, and has the advantages of high selectivity, adaptability to various extreme conditions and fast analysis speed. The present invention proposes to use down-conversion luminescent materials as fluorescent probes, and diffuse reflection picocubic cavities as gas absorption cells to increase the effective optical path and improve the sensitivity of low-concentration carbon dioxide detection. On this basis, the change of fluorescence intensity is used to realize the detection of carbon dioxide concentration. Summary of the invention

[0004] One object of the present invention is to disclose a material for detecting carbon dioxide concentration, the material is a down-conversion fluorescent material sensitized by ytterbium ions, and can achieve accurate detection of carbon dioxide concentration. Another object of the present invention is to disclose a method for preparing the material for detecting carbon dioxide concentration.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] The material used for carbon dioxide concentration detection is a down-conversion fluorescent material sensitized by ytterbium ions. The material is rare earth doped scandium molybdate coated with silicon dioxide. The molecular formula of the material is: Sc2Mo3O 12 : Li / Yb / Tm@SiO2.

[0007] A method for detecting carbon dioxide concentration based on down-conversion luminescent materials, wherein the effective optical path is increased by a diffuse reflection microcubic cavity, the surface of which is coated with a high diffuse reflection material; a down-conversion fluorescent probe is arranged on the surface of the high diffuse reflection material, characterized in that the down-conversion fluorescent material is sensitized with ytterbium ions. Carbon dioxide concentration detection is achieved by characterizing the luminescence intensity under different carbon dioxide concentration conditions.

[0008] Preferably, the highly diffuse reflective material is Avian-D coating modified with citric acid ligands.

[0009] A material for detecting carbon dioxide concentration, wherein the preparation method of the material comprises the following steps in sequence:

[0010] (1) Dissolve 1.2 mmol of scandium nitrate, 0.4 mmol of ytterbium nitrate, 0.2 mmol of thulium nitrate, and 0.2 mmol of lithium nitrate in 6 ml of deionized water by molar percentage, and heat and stir until all the raw materials are dissolved to obtain a transparent mixed solution;

[0011] (2) dissolving 3 mmol of ammonium molybdate and 4 mmol of citric acid in 5 ml of deionized water, and adding the mixture to the solution obtained in step (1);

[0012] (3) The mixed solution is heated in a water bath at 80 degrees Celsius to form a sol;

[0013] (4) The sol was dried at 120 °C for 24 h to obtain a gel;

[0014] (5) After the gel is fully ground in a mortar, it is kept at 850 degrees Celsius for 3 hours. After the reaction is completed, Sc2Mo3O 12 : Li / Yb / Tm;

[0015] (6) Sc2Mo3O 12 : Li / Yb / Tm powder was dissolved in 10 ml of aqueous solution and 10 ml of ethanol and stirred for 60 min;

[0016] (7) Add 10 ml of ethyl orthosilicate dropwise, then add a small amount of ammonia water until the solution pH is 8, stir for 4 hours, and the final product is obtained.

[0017] The patented material for carbon dioxide concentration detection is used. The molecular formula of the material is: Sc2Mo3O 12 : Li / Yb / Tm@SiO2. 980 nm incident photons are sensitized by Yb 3+ After ion absorption, the activated ions Tm are filled in turn through the energy transfer process 3+ The excited state energy level 3 H5 and 3 F4, thus achieving down-conversion luminescence. 2+Ion doping can greatly increase the down-conversion luminescence intensity, reduce the laser excitation threshold, and realize low-power excitation carbon dioxide concentration detection. The surface is coated with silicon dioxide to improve the adsorption efficiency of fluorescent probes to carbon dioxide in the environment and improve the detection sensitivity. As the concentration of carbon dioxide adsorption increases, the efficiency of phonon-assisted energy transfer decreases, resulting in a decrease in luminescence intensity. By characterizing the down-conversion luminescence intensity under different carbon dioxide concentration conditions, carbon dioxide concentration detection can be achieved with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Example Sc2Mo3O 12 : X-ray diffraction pattern of Li / Yb / Tm@SiO2;

[0019] Figure 2 Example Sc2Mo3O 12 : Down-conversion luminescence spectrum of Li / Yb / Tm@SiO2;

[0020] Figure 3 Example Sc2Mo3O 12 : Down-conversion luminescence intensity integral curve of Li / Yb / Tm@SiO2 under different carbon dioxide concentration conditions;

[0021] Figure 4 : Diffuse reflection microcavity, Example Sc2Mo3O 12 : Down-conversion luminescence intensity integral curve of Li / Yb / Tm@SiO2 under different carbon dioxide concentration conditions;

[0022] Figure 5 :Comparative Example Sc2Mo3O 12 : Down-conversion luminescence spectrum of Yb / Tm;

[0023] Figure 6 :Comparative Example Sc2Mo3O 12 : Down-conversion luminescence intensity integral curves of Li / Yb / Tm under different CO2 concentrations. DETAILED DESCRIPTION

[0024] Combine the following Figure 1-6 The present invention is further described. Example

[0025] A method for detecting carbon dioxide concentration increases the effective optical path by using a diffuse reflection microcube cavity, the surface of which is coated with a high diffuse reflection material; a fluorescent probe material is arranged on the surface of the high diffuse reflection material, and carbon dioxide concentration detection is achieved by characterizing the down-conversion luminescence intensity under different carbon dioxide concentration conditions.

[0026] Optical path extension technology: In order to improve the sensitivity of gas concentration detection, this system uses diffuse reflection micro-cubic cavity to increase the effective optical path. The inner surface is coated with high diffuse reflection material, and the diffuse reflection of light on the inner surface of the integrating sphere is used to increase the effective optical path.

[0027] Coating of fluorescent probe material inside the microcubic cavity: The fluorescent probe material is coated on the surface of the microcubic cavity, and the concentration of carbon dioxide is determined by the change in the output light intensity using an optical fiber to input an excitation light source and output an emission light.

[0028] The highly diffuse reflective material is Avian-D coating modified with citric acid ligands.

[0029] Preparation of fluorescent probe materials: The molecular formula of the fluorescent probe material is Sc2Mo3O 12 : Li / Yb / Tm@SiO2, the preparation method comprises the following steps in sequence: (1) dissolving 1.2 mmol of scandium nitrate, 0.4 mmol of ytterbium nitrate, 0.2 mmol of thulium nitrate and 0.2 mmol of lithium nitrate in 6 ml of deionized water by molar percentage, heating and stirring, so that all the raw materials are dissolved to obtain a transparent mixed solution; (2) dissolving 3 mmol of ammonium molybdate and 4 mmol of citric acid in 5 ml of deionized water, and adding the mixture to the solution obtained in step (1); (3) heating the mixed solution in a water bath at 80 degrees Celsius to form a sol; (4) drying the sol at 120 degrees Celsius for 24 hours to obtain a gel; (5) grinding the gel in a mortar and then keeping it at 850 degrees Celsius for 3 hours to obtain Sc2Mo3O 12 : Li / Yb / Tm; (6) Sc2Mo3O 12 : Li / Yb / Tm powder was dissolved in 10 ml of aqueous solution and 10 ml of ethanol and stirred for 60 minutes; (7) 10 ml of ethyl orthosilicate was added dropwise, and then a small amount of ammonia water was added until the pH of the solution was 8. After stirring for 4 hours, the final product Sc2Mo3O was obtained. 12 : Li / Yb / Tm@SiO2.

[0030] Sc2Mo3O prepared by the above method 12 : Li / Yb / Tm@SiO2 probe material, powder X-ray diffraction analysis shows that the synthesized product is a pure orthorhombic phase ( Figure 1 ); Under 980 nm laser irradiation, Tm 3 Ions emit light in the infrared region ( Figure 2 ), the emission center wavelength is about 1830 nanometers, corresponding to 3 F4→ 3 The electronic transition of H6. 3Ions cannot absorb the energy of incident photons at 980 nanometers, and their upconversion luminescence is achieved through an energy transfer process. Tm: 3 F4 and Yb: 2 F 5 / 2 The energy difference between them is compensated by the energy of phonons. Therefore, the phonon energy of the matrix has a greater influence on its down-conversion luminescence efficiency.

[0031] like Figure 3 As shown in Figure 2, as the concentration of carbon dioxide around the probe material increases, Tm 3 The luminescence intensity of the ions gradually decreases, which is because the Sc2Mo3O 12 : Li / Yb / Tm@SiO2 probe material can adsorb carbon dioxide, and the adsorbed carbon dioxide will change the phonon energy of the matrix, weakening the Yb 3+ To Tm 3+ The energy transfer efficiency is reduced, which reduces the down-conversion luminescence intensity. Figure 4 As shown, Sc2Mo3O 12 : Li / Yb / Tm@SiO2 probe material is coated on the inner surface of the microcubic cavity, and the optical fiber is used to input the excitation light source and output the emission light. As the concentration of carbon dioxide gradually increases, the down-conversion luminescence intensity gradually weakens, and its weakening amplitude is much better than the case without the microcubic cavity. This shows that the diffuse reflection microcubic cavity increases the effective optical path and improves the sensitivity of carbon dioxide detection. The principle of the diffuse reflection microcubic cavity is the same as that of the integrating sphere, both of which use the diffuse reflection of light inside it to increase the effective optical path.

[0032] In the natural environment, the normal content of carbon dioxide in the air is 0.04% (400ppm), and it can reach 500ppm in large cities with many vehicles; when the carbon dioxide concentration reaches 1500-2000 PPM, people will feel asthma, headache and dizziness; when the carbon dioxide concentration in the office air reaches 2000 ppm, employees will feel sleepy, inattentive and mentally exhausted; after exceeding 2000PPM, thinking ability will be significantly reduced; when the concentration exceeds 5000PPM, human body functions are seriously disordered, causing people to lose consciousness and perception. The detection system designed by the present invention can well detect the carbon dioxide concentration within the range of 100-5000 ppm, and has a good application prospect.

[0033] In order to further reflect the effect of Li+ ion doping in the matrix, we compared Sc2Mo3O 12 : Yb / Tm and Sc2Mo3O 12 : Down-conversion luminescence intensity of Li / Yb / Tm. Figure 5 As shown, Sc2Mo3O 12 : The spectral intensity of Yb / Tm is much lower than that of Sc2Mo3O 12: Li / Yb / Tm, indicating that Li+ ion doping can improve the crystallinity of the matrix, reduce the probability of non-radiative relaxation of activated ions, and increase the luminescence intensity.

[0034] In order to further demonstrate the importance of silica coating on the surface of fluorescent probes, we used Sc2Mo3O 12 : The carbon dioxide detection performance of Li / Yb / Tm was analyzed. Figure 6 As shown in the figure, as the concentration of carbon dioxide in the environment gradually increases, the down-conversion luminescence intensity changes slightly. This is because Sc2Mo3O 12 : Li / Yb / Tm matrix cannot effectively adsorb carbon dioxide, and carbon dioxide in the environment cannot change Yb 3+ To Tm 3+ The energy transfer efficiency is thus difficult to affect the down-conversion luminescence intensity.

Claims

1. A material for detecting carbon dioxide concentration, characterized in that: The material is a down-conversion fluorescent material sensitized by ytterbium ions; the down-conversion fluorescent material sensitized by ytterbium ions is rare earth doped scandium molybdate with a surface coated with silicon dioxide, and the molecular formula is: Sc2Mo3O 12 : Li / Yb / Tm@SiO2.

2. A method for detecting carbon dioxide concentration based on down-conversion luminescent materials, wherein the effective optical path is increased by a diffuse reflection microcubic cavity, the surface of which is coated with a high diffuse reflection material; a down-conversion fluorescent probe is arranged on the surface of the high diffuse reflection material, characterized in that: The down-conversion fluorescent probe is the down-conversion fluorescent material sensitized with ytterbium ions as claimed in claim 1.

3. The method for detecting carbon dioxide concentration based on down-conversion luminescent materials according to claim 2, characterized in that By characterizing the luminescence intensity under different carbon dioxide concentration conditions, carbon dioxide concentration detection can be achieved.

4. A method for preparing a material for detecting carbon dioxide concentration, characterized in that: The material is the down-conversion fluorescent material sensitized by ytterbium ions as claimed in claim 1, and the preparation method comprises the following steps in sequence: (1) Dissolve 1.2 mmol of scandium nitrate, 0.4 mmol of ytterbium nitrate, 0.2 mmol of thulium nitrate, and 0.2 mmol of lithium nitrate in 6 ml of deionized water by molar percentage, and heat and stir until all the raw materials are dissolved to obtain a transparent mixed solution; (2) dissolving 3 mmol of ammonium molybdate and 4 mmol of citric acid in 5 ml of deionized water, and adding the mixture to the solution obtained in step (1); (3) The mixed solution is heated in a water bath at 80 degrees Celsius to form a sol; (4) The sol was dried at 120 °C for 24 h to obtain a gel; (5) After the gel is fully ground in a mortar, it is kept at 850 degrees Celsius for 3 hours. After the reaction is completed, Sc2Mo3O 12 : Li / Yb / Tm; (6) Sc2Mo3O 12 : Li / Yb / Tm powder was dissolved in 10 ml of aqueous solution and 10 ml of ethanol and stirred for 60 minutes; 10 ml of ethyl orthosilicate was added dropwise, and then a small amount of ammonia water was added until the pH of the solution was 8, and stirred for 4 hours to obtain the final product.

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