CN115093846A - Material for detecting concentration of carbon dioxide and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of gas detection. The material used for the detection of carbon dioxide concentration is a down-conversion fluorescent material sensitized by ytterbium ions, and the material is a rare earth-doped scandium molybdate coated with silicon dioxide on the surface. The molecular formula of the material is: Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ . This patent is used for carbon dioxide concentration detection materials, and the carbon dioxide concentration detection accuracy is high.

Description

Materials for carbon dioxide concentration detection and preparation method thereof

technical field

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 technique

Carbon dioxide is a colorless, odorless gas with the molecular formula CO ₂ , and the chemical bonds within the molecule are usually covalent bonds. Gaseous carbon dioxide is used in carbonation of soft drinks, pH control in water treatment processes, chemical processing, food preservation, inert protection in chemical and food processing, welding gas, plant growth stimulator; diluent for bactericidal gas in foundry, widely used For sterilization of medical equipment, packaging materials, clothing, fur and bedding, etc. The detection methods of carbon dioxide, such as chemical method, pass the generated gas into clear lime water, and the lime water becomes turbid, which proves that the gas is carbon dioxide; combustion method, infrared gas analysis method, gas chromatography and volumetric titration method, etc. These methods have the problems of complex analysis process, slow detection speed or high cost.

Detection technology based on fluorescent materials is widely used in the detection of temperature, biomolecules, pH and other fields. It has the advantages of high selectivity, adaptability to various extreme conditions and fast analysis speed. The present invention proposes to use down-conversion luminescent material as a fluorescent probe, and a diffuse reflection microcube cavity as a gas absorption cell to increase the effective optical path and improve the sensitivity of low-concentration carbon dioxide detection. detection.

SUMMARY OF THE INVENTION

One object of the present invention is to disclose a material for carbon dioxide concentration detection, which is a down-conversion fluorescent material sensitized by ytterbium ions, so as to realize accurate detection of carbon dioxide concentration. Another object of the present invention is to disclose a preparation method of a material for carbon dioxide concentration detection.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical scheme:

The material used for the detection of carbon dioxide concentration is a down-conversion fluorescent material sensitized by ytterbium ions. The material is rare earth doped scandium molybdate coated with silica. The molecular formula of the material is: Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ .

A carbon dioxide concentration detection method based on a down-conversion luminescent material, the effective optical path is increased by a diffuse reflection micro-cube cavity, the surface of the diffuse reflection micro-cube cavity is coated with a high diffuse reflection material; the surface of the high diffuse reflection material is provided with a down conversion fluorescent probe , which is characterized by a down-conversion fluorescent material sensitized with ytterbium ions. Carbon dioxide concentration detection is realized by characterizing the luminescence intensity under different carbon dioxide concentration conditions.

Preferably, the highly diffuse reflection material is Avian-D paint modified with citric acid ligands.

The material used for the detection of carbon dioxide concentration, the preparation method of the material 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, heating and stirring to dissolve all the raw materials to obtain a transparent mixed solution ;

(2) 3 mmol of ammonium molybdate and 4 mmol of citric acid were dissolved in 5 ml of deionized water, and added 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 the gel is fully ground in a mortar, the gel is kept at 850 degrees Celsius for 3 hours, and after the reaction, Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm is obtained;

(6) Dissolve the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm powder in 10 ml of aqueous solution and 10 ml of ethanol, and stir for 60 minutes;

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

The material for carbon dioxide concentration detection of this patent is adopted, and the molecular formula of the material is: Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ . After the 980 nm incident photon is absorbed by the sensitizer Yb ³⁺ ion, the excited state energy levels ³ H ₅ and ³ F ₄ of the activated ion Tm ³⁺ are filled in turn through the energy transfer process, thereby realizing down-conversion luminescence. The doping of Li ²⁺ ions can greatly increase the down-conversion luminescence intensity, reduce the excitation threshold of the laser, and realize low-power excitation carbon dioxide concentration detection. The surface is coated with silica, which is used to improve the adsorption efficiency of the fluorescent probe to carbon dioxide in the environment and improve the detection sensitivity. With the increase of carbon dioxide adsorption concentration, the phonon-assisted energy transfer efficiency decreases, resulting in a weakening of the luminescence intensity. By characterizing the down-conversion luminescence intensity under different carbon dioxide concentration conditions, carbon dioxide concentration detection can be realized, and the carbon dioxide concentration detection accuracy is high.

Description of drawings

Figure 1: X-ray diffraction pattern of Example Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ ;

Figure 2: Down-conversion luminescence spectrum of Example Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ ;

Figure 3: The integral curve of down-conversion luminescence intensity of Example Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ under different carbon dioxide concentrations;

Figure 4: In the diffuse reflection microcavity, the integral curve of down-conversion luminescence intensity of Example Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ under different carbon dioxide concentrations;

Figure 5: Down-conversion luminescence spectrum of Comparative Example Sc ₂ Mo ₃ O ₁₂ : Yb/Tm;

Figure 6: The integral curve of down-conversion luminescence intensity of the comparative example Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm under different carbon dioxide concentrations.

Detailed ways

The present invention will be further described below with reference to FIGS. 1-6 .

Example

A carbon dioxide concentration detection method, the effective optical path is increased through a diffuse reflection micro-cube cavity, the surface of the diffuse reflection micro-cube cavity is coated with a high diffuse reflection material; the surface of the high diffuse reflection material is provided with a fluorescent probe material, which can characterize different carbon dioxide concentration conditions by The down-converted luminescence intensity under the lower temperature can realize the detection of carbon dioxide concentration.

Optical path extension technology: In order to improve the sensitivity of gas concentration detection, the system uses a diffuse reflection microcube cavity to increase the effective optical path. increase.

Coating of fluorescent probe material inside the micro-cube cavity: Coating the fluorescent probe material on the surface of the micro-cube cavity, using optical fiber to input excitation light source and output emission light, and determine the concentration of carbon dioxide by the change of output light intensity.

The high diffuse reflectance material is Avian-D paint modified with citric acid ligands.

Preparation of fluorescent probe material: the molecular formula of the fluorescent probe material is Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ , and the preparation method sequentially includes the following steps: (1) in molar percentage, 1.2 mmol scandium nitrate is , 0.4 mmol of ytterbium nitrate, 0.2 mmol of thulium nitrate and 0.2 mmol of lithium nitrate were dissolved in 6 ml of deionized water with heating and stirring, so that all the raw materials were dissolved to obtain a transparent mixed solution; (2) 3 mmol of ammonium molybdate and 4 Millimolar citric acid was dissolved in 5 ml of deionized water and added to the solution obtained in step (1); (3) the mixed solution was heated in a water bath at 80 degrees Celsius, and the mixed solution became a sol; (4) the sol was heated at 120 degrees Celsius (5) After fully grinding the gel in a mortar, the gel was kept at 850 degrees Celsius for 3 hours to obtain Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm after the reaction; ( 6) Dissolve the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm powder in 10 ml of aqueous solution and 10 ml of ethanol, and stir for 60 minutes; (7) Add 10 ml of ethyl orthosilicate dropwise, and then add a small amount of ammonia water When the pH of the solution was 8, it was stirred, and after 4 hours, the final product Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ was obtained.

Powder X-ray diffraction analysis of the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ probe material prepared by the above method shows that the synthesized product is a pure orthorhombic phase (Fig. 1); under 980 nm laser irradiation , the emission of Tm ³ ions in the infrared region can be observed (Fig. 2), the emission center wavelength is about 1830 nm, corresponding to the electronic transition of ³ F ₄ → ³ H ₆ . Because Tm ³ ions cannot absorb the incident photon energy at 980 nm, its upconversion luminescence is achieved through an energy transfer process. The energy difference between Tm: ³ F ₄ and Yb: ² F _5/2 is compensated by the phonon energy, so the phonon energy of the host has a great influence on its down-conversion luminous efficiency.

As shown in Fig. 3, with the increase of carbon dioxide concentration around the probe material, the luminescence intensity of Tm ³ ions gradually decreases, which is because the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ probe material can adsorb carbon dioxide, and the adsorbed carbon dioxide will change the phonon energy of the matrix, weaken the energy transfer efficiency from Yb ³⁺ to Tm ³⁺ , and reduce the down-conversion luminescence intensity. As shown in Fig. 4, the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ probe material was coated on the inner surface of the micro-cube cavity, and the excitation light source and the output emission light were input by the optical fiber. With increasing, the down-conversion luminescence intensity gradually weakens, and its weakening magnitude is much better than that without the microcube cavity. This shows that the diffuse reflection microcube cavity increases the effective optical path and improves the detection sensitivity of carbon dioxide. In principle, the diffuse reflection microcube cavity is the same as the integrating sphere, which uses the diffuse reflection of light inside it to increase the effective optical path.

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 office When the concentration of carbon dioxide in the air reaches 2000 ppm, employees will feel sleepy, inattentive and mentally exhausted; when the concentration exceeds 2000 PPM, the thinking ability decreases significantly; when the concentration exceeds 5000 PPM, the human body function is seriously disturbed, causing people to lose consciousness and consciousness. The detection system designed by the invention can detect the carbon dioxide concentration well in the range of 100-5000 ppm, and has a good application prospect.

In order to further reflect the effect of Li+ ion doping in the host, we compared the down-conversion luminescence intensities of Sc ₂ Mo ₃ O ₁₂ : Yb/Tm and Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm. As shown in Figure 5, the spectral intensity of Sc ₂ Mo ₃ O ₁₂ : Yb/Tm is much lower than that of Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm, indicating that Li+ ion doping can improve the crystallinity of the matrix and reduce the activation of ions The radiation-free relaxation probability increases the luminous intensity.

In order to further demonstrate the importance of silica coating on the surface of fluorescent probes, we analyzed the carbon dioxide detection performance of Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm. As shown in Fig. 6, as the carbon dioxide concentration in the environment gradually increases, the down-conversion luminescence intensity changes less, this is because the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm matrix cannot effectively adsorb carbon dioxide, and the carbon dioxide in the environment The energy transfer efficiency from Yb ³⁺ to Tm ³⁺ cannot be changed, so it is difficult to influence its down-conversion luminescence intensity.

Claims (7)

1. A material for carbon dioxide concentration detection, characterized in that the material is a down-conversion fluorescent material sensitized by ytterbium ions. 2 . The material for carbon dioxide concentration detection according to claim 1 , wherein the material is a rare earth-doped scandium molybdate coated with silicon dioxide on the surface. 3 . 3. The material for carbon dioxide concentration detection according to claim 2, wherein the molecular formula of the material is: Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm@SiO ₂ . 4. A carbon dioxide concentration detection method based on a down-conversion luminescent material, the effective optical path is increased through a diffuse reflection micro-cube cavity, the surface of the diffuse reflection micro-cube cavity is coated with a high diffuse reflection material; the surface of the high diffuse reflection material is provided with down-conversion fluorescence A probe characterized by a down-converting fluorescent material sensitized with ytterbium ions. 5 . The carbon dioxide concentration detection method based on the down-conversion luminescent material according to claim 4 , wherein the carbon dioxide concentration detection is realized by characterizing the luminous intensity under different carbon dioxide concentration conditions. 6 . 6 . The carbon dioxide concentration detection method based on a down-conversion luminescent material according to claim 4 , wherein the highly diffuse reflection material is Avian-D paint modified with citric acid ligands. 7 . 7. The preparation method of the material used for carbon dioxide concentration detection, it is characterized in that, the material is the rare earth doped scandium molybdate whose surface is coated with silica, and the preparation method of the material comprises the following steps in turn: (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, heating and stirring to dissolve all the raw materials to obtain a transparent mixed solution ; (2) 3 mmol of ammonium molybdate and 4 mmol of citric acid were dissolved in 5 ml of deionized water, and added 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 the gel is fully ground in a mortar, the gel is kept at 850 degrees Celsius for 3 hours, and after the reaction, Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm is obtained; (6) Dissolve the Sc ₂ Mo ₃ O ₁₂ : Li/Yb/Tm powder in 10 ml of aqueous solution and 10 ml of ethanol, stir for 60 minutes; add 10 ml of ethyl orthosilicate dropwise, and then add a small amount of ammonia water to the solution After stirring at pH 8, the final product was obtained after 4 hours.

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