A visual recording method for the diffusion process of single crystal porous materials

Abstract

The present application discloses a method for visually recording the diffusion process of a single-crystal porous material, comprising the following steps: dispersing the porous material crystals into a fluorescent confocal culture dish, adding a fluorescent probe solution for disturbance, and continuously recording the fluorescence signal image of the single-crystal porous material through a super-resolution fluorescence microscope, thereby obtaining an image of the surface penetration and intracrystalline diffusion process in the single-crystal porous material evolving over time. The present application is based on super-resolution fluorescence microscopy technology, which can conveniently realize the visualization process of the surface and interface mass transfer of single-crystal porous materials, effectively distinguish between the surface penetration and intracrystalline diffusion steps, quantify the surface permeability and intracrystalline diffusion coefficient in a single crystal, and analyze its mass transfer limitation mechanism, which has a very distinct physical meaning. By recording the surface and interface mass transfer properties of single-crystal porous materials, the basic properties of surface penetration and intracrystalline diffusion are effectively supplemented, which can provide guidance for the synthesis and optimization of porous materials.

Description

Technical Field

[0001] The invention relates to a method for visually recording a diffusion process of a single crystal porous material, and belongs to the field of material testing. Background Art

[0002] Porous crystalline materials, with their unique properties of molecular sieving and selectivity, are widely used in heterogeneous catalysis, adsorption separation, and other fields. However, because the kinetic diameter of guest molecules is comparable to the pore size, molecular mass transfer processes significantly limit the application of porous crystalline materials. Currently, the mass transfer theory of porous materials remains incomplete, and further improvement of basic mass transfer theory is of great significance.

[0003] It is generally believed that the diffusion process in porous materials is dominated by two mass transfer mechanisms: intracrystalline diffusion and surface resistance. Intracrystalline diffusion is controlled by the diffusion of guest molecules within the pores, while surface permeation is influenced by the transport of guest molecules on the external surface. However, due to the limitations of current mass transfer research methods, understanding the fundamental properties and control mechanisms of mass transfer processes remains a major challenge. Finding methods to study the host-guest interaction between guest molecules and crystal surfaces will help us understand surface mass transfer mechanisms, lay the foundation for regulating the properties of porous materials, and thus guide the synthesis and design of catalysts to promote their effective utilization.

[0004] The main macroscopic methods for measuring the diffusion coefficient include zero column length, frequency response, and adsorption rate. However, with the exception of the adsorption rate method, macroscopic measurement methods currently lack mathematical methods to directly quantify surface permeability and intracrystalline diffusion, making it difficult to directly quantify surface permeability and intracrystalline diffusion coefficient. On the other hand, microscopic methods such as microscopy have measured the diffusion behavior of single crystals of porous materials, revealing the differences from macroscopic methods for measuring diffusion and indicating that macroscopic methods may lead to incorrect conclusions when judging the mass transfer control mechanism dominated by surface resistance, making microscopic methods irreplaceable in studying mass transfer mechanisms. However, current microscopic techniques mainly include interference microscopy and infrared microscopy, which still reflect the mass transfer properties of the entire crystal and still lack the study of local details in the crystal. The research on surface permeability and intracrystalline diffusion is still not in-depth enough. Therefore, it is necessary to construct a high-resolution, comprehensive single crystal measurement method for studying surface and intracrystalline transport mechanisms.

[0005] Super-resolution fluorescence microscopy is widely used in biology and is now also gaining applications in nanomaterial research. Compared to interference microscopy, fluorescence microscopy utilizes a confocal optical path, enabling the acquisition of fluorescence signals from any cross-section of a crystal. Super-resolution technology can overcome the optical diffraction limit, resulting in higher imaging resolution, enabling applications in the study of small-crystal molecular sieves and making them more suitable for industrial applications. However, a method for quantitatively measuring diffusion in single-crystal porous materials using super-resolution fluorescence microscopy remains lacking. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for studying the basic properties of surface and interface mass transfer in single crystal porous materials, which can measure the surface permeability and intracrystalline diffusion coefficient in single crystals, so as to solve the problems of unclear understanding and unclear properties of single crystal mass transfer in existing microscopic methods.

[0007] Existing macroscopic methods for studying porous materials are not suitable for studying mass transfer control mechanisms and basic properties. Microscopic methods that can be used for the mass transfer properties of single-crystal porous materials measure the average signal of the adsorbate along the vertical direction in the single crystal, reflecting the mass transfer properties of the entire crystal, while ignoring the details of the mass transfer at the surface interface of the single-crystal porous material. In addition, the use of traditional microscopic quantitative methods requires assumptions about the mass transfer control mechanism, which may cause large errors in the fitting results. The inventors used super-resolution fluorescence microscopy to study the mass transfer properties in single-crystal porous materials. Based on the mass transfer theory of single-crystal porous materials, they explored the surface penetration process and the intracrystalline diffusion process, and were able to obtain the surface permeability and intracrystalline diffusion coefficient in the single crystal, which has clear physical significance.

[0008] A method for visually recording the diffusion process of a single crystal porous material comprises the following steps:

[0009] The porous material crystals are dispersed into a fluorescence confocal culture dish, and a fluorescent probe solution is added to disturb the material. The fluorescence signal image of the single crystal porous material is continuously recorded using a super-resolution fluorescence microscope to obtain an image of the surface penetration and intracrystalline diffusion process of the single crystal porous material evolving over time.

[0010] Optionally, the porous material crystals are dispersed into a fluorescent confocal culture dish, and then the focal plane of the super-resolution fluorescence microscope is adjusted to the top surface of the single crystal porous material, a fluorescent probe solution is added for disturbance, and the fluorescence signal image of the single crystal porous material is continuously recorded by the super-resolution fluorescence microscope, thereby obtaining an image of the surface penetration process of the single crystal porous material evolving over time.

[0011] Optionally, the porous material crystals are dispersed into a fluorescent confocal culture dish, and then the focal plane of the super-resolution fluorescence microscope is adjusted to the central plane of the single crystal porous material, a fluorescent probe solution is added for disturbance, and the fluorescence signal image of the single crystal porous material is continuously recorded by the super-resolution fluorescence microscope, thereby obtaining an image of the surface penetration and intracrystalline diffusion process of the single crystal porous material evolving over time.

[0012] Optionally, the single crystal porous material is subjected to a calcination treatment, wherein the calcination temperature is 550-650° C. and the calcination time is 24-72 hours.

[0013] Optionally, the fluorescent probe includes at least one of trans-4-[4-dimethylaminostyryl]-1-methylpyridine iodide, 4-(4-dimethylaminostyryl)-1-methylpyridine iodide, 4-(4-dimethylaminostyryl)methylpyridine iodide, 4',6-diamidino-2-phenylindole, and pyronin G;

[0014] Optionally, the concentration of the fluorescent probe is 1 to 100 μmol / L;

[0015] Optionally, the concentration of the fluorescent probe is 5 to 20 μmol / L.

[0016] Optionally, the super-resolution fluorescence microscope records fluorescence signal images with a time resolution of 3 to 10 seconds.

[0017] Optionally, the super-resolution fluorescence microscope used includes at least one of a co-structured light microscope, a stimulated emission diffraction microscope and a random optical reconstruction microscope.

[0018] Optionally, the method further comprises the following steps:

[0019] (a) When recording the fluorescence signal image of a single-crystal porous material, record the fluorescence intensity F; where: the initial moment corresponds to the intensity F0, and the moment t corresponds to the intensity F t , the corresponding intensity F at adsorption equilibrium ∞ ;

[0020] (b) Fluorescence intensity F corresponding to the adsorption equilibrium reached by the single crystal porous material under the perturbation of the fluorescent probe ∞ , the measured fluorescence intensity change data were normalized using formula (1) to obtain the normalized probe adsorption concentration change curve over time

[0021]

[0022] In formula (1), m t represents the adsorption amount in the single crystal porous material at each moment, m ∞ It represents the adsorption amount of single crystal porous material at adsorption equilibrium;

[0023] (c) When the adsorption time is 0-40 seconds, the surface permeability α is determined using the governing equation shown in formula (2),

[0024]

[0025] In formula (2), t represents the adsorption time, and l represents the characteristic length of the single crystal porous material;

[0026] (d) According to the surface permeability obtained by formula (2), the intracrystalline diffusion coefficient D of the single crystal porous material is calculated by formula (3).

[0027]

[0028] In formula (3), L represents the ratio of the characteristic time of intracrystalline diffusion to surface penetration, β n Represents the parameters in the equation being solved.

[0029] Optionally, the coefficient of determination formula (4) is used to determine the error between the curve (3) fitted by the equation and the experimental value to determine the accuracy of the method;

[0030]

[0031] In formula (4), R 2 represents the coefficient of determination between the calculated fit and the experimental measurement, m t fit It means that formula (3) fits the adsorption amount at each moment, It represents the average value of the adsorption amount at each time.

[0032] Optionally, the surface permeability and intracrystalline diffusion coefficient obtained by fitting calculation are brought into the governing equation, which is consistent with the experimental data of the change of adsorption concentration of single crystal porous materials with time, and the determination coefficient is 0.95-1.

[0033] Optionally, the loading amount of the porous material single crystal for super-resolution fluorescence measurement is 0.2 to 1 mg, and the number of crystals in the fluorescence microscope lens is 1 to 6.

[0034] The top surface of the single crystal porous material mentioned in this application refers to the surface of the molecular sieve single crystal, and the center surface refers to the center cross section of the molecular sieve single crystal.

[0035] The beneficial effects of this application include:

[0036] 1) Based on super-resolution fluorescence microscopy technology, this application can conveniently realize the visualization process of surface and interface mass transfer of single-crystal porous materials, effectively distinguish the surface penetration and intracrystalline diffusion steps, quantify the surface permeability and intracrystalline diffusion coefficient in single crystals, and analyze their mass transfer limitation mechanism, which has very distinct physical significance.

[0037] 2) This application can effectively supplement the basic theory of mass transfer in porous materials. By recording the surface and interfacial mass transfer properties of single-crystal porous materials, it effectively supplements the basic properties of surface permeation and intracrystalline diffusion, providing guidance for the synthesis and optimization of porous materials and effectively improving their performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1This is a schematic diagram of an implementation case of the present invention using super-resolution fluorescence microscopy to measure surface penetration and intracrystalline diffusion in single-crystal porous materials and their corresponding diffusion coefficients.

[0039] Figure 2 This is an image of the time evolution of the penetration process of a fluorescent probe on the surface of a single crystal porous material measured by super-resolution fluorescence microscopy in Example 1 of the present invention.

[0040] Figure 3 This is an image of the time evolution of the surface penetration and intracrystalline diffusion of a fluorescent probe on a single crystal porous material measured using super-resolution fluorescence microscopy in Example 2 of the present invention.

[0041] Figure 4 These are the experimental data of the normalized concentration adsorption curve that changes with time in the experiment of measuring the surface permeability and intracrystalline diffusion coefficient of single crystal porous materials in Example 2 of the present invention and the fitting results of the control equation.

[0042] Figure 5 These are the experimental data of the normalized concentration adsorption curve that changes with time in the experiment of measuring the surface permeability and intracrystalline diffusion coefficient of single crystal porous materials in Example 3 of the present invention and the fitting results of the control equation. DETAILED DESCRIPTION

[0043] The present application is described in detail below in conjunction with specific implementation cases, but the present application is not limited to these implementation cases. Unless otherwise specified, the raw materials in the examples of the present application were purchased through commercial channels.

[0044] The test material used in the present invention is a ZSM-5 single crystal molecular sieve porous material, but the method disclosed in the present invention is not limited to measuring the surface-interface mass transfer process of guest molecules in the ZSM-5 molecular sieve.

[0045] The super-resolution fluorescence microscope was an N-SIM structured light illumination microscope produced by Nikon Corporation of Japan.

[0046] Example 1

[0047] The results show that the trans-4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine molecule is stable in the ZSM-5 molecular sieve single crystal (crystal size is 20×10×10 μm) under low loading. 3) in the surface penetration process. First, the ZSM-5 molecular sieve was placed in a muffle furnace at 600°C and calcined for 48 hours to completely remove the template and the fluorescent substance in the system. The calcined ZSM-5 molecular sieve single crystals were then dispersed into a confocal culture dish and placed on the stage of a super-resolution fluorescence microscope. Before the test, the confocal plane of the super-resolution fluorescence microscope was adjusted so that it was aligned with the surface of the ZSM-5 single crystal sample. Trans-4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine molecule was selected as the fluorescent probe molecule, and deionized water was used as the solvent. At a given temperature of 25°C, 2 mL of a fluorescent probe solution with a concentration of 10 μmol / L was added to the confocal culture dish, the fluorescence signal acquisition time resolution was 5 s, and the fluorescence images at each moment were recorded.

[0048] Example 2

[0049] The results show that the trans-4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine molecule is stable in the ZSM-5 molecular sieve single crystal (crystal size is 20×10×10 μm) under low loading. 3 ) in the surface penetration and intracrystalline diffusion process. First, the ZSM-5 molecular sieve was placed in a muffle furnace at 600°C and calcined for 48 hours to completely remove the template and the fluorescent substance in the system. The calcined ZSM-5 molecular sieve single crystals were then dispersed into a confocal culture dish and placed on the stage of a super-resolution fluorescence microscope. Before the test, the confocal plane of the super-resolution fluorescence microscope was adjusted so that it was aligned with the center plane of the ZSM-5 single crystal sample. Trans-4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine molecule was selected as the fluorescent probe molecule, and deionized water was used as the solvent. At a given temperature of 25°C, 1 mL of a fluorescent probe solution with a concentration of 5 μmol / L was added to the confocal culture dish, and the fluorescence signal acquisition time resolution was 5s. The fluorescence images at each moment and the corresponding fluorescence signal intensity were recorded. The fluorescence signals at each moment were normalized, and the initial stage of the normalized curve that changes with time was processed using formula (1). The surface permeability of the probe molecule in the ZSM-5 molecular sieve single crystal was obtained by fitting: α = 3.4 × 10 -8 m / s, and the coefficient of determination is 0.995, indicating that the calculated results have a high degree of credibility. Further processing the normalized curve of the time-varying phase according to formula (2), the intracrystalline diffusion coefficient D = 9.2 × 10 -11 m / s 2 , the coefficient of determination is 0.981, indicating that the calculated results have high credibility.

[0050] Example 3

[0051] The results show that the molecular structure of 4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine is stable in the ZSM-5 molecular sieve single crystal (crystal size is 10×5×5μm) under low loading. 3 ) in the surface penetration and intracrystalline diffusion process. First, the ZSM-5 molecular sieve was placed in a muffle furnace at 600°C and calcined for 48 hours to completely remove the template and the fluorescent substance in the system. The calcined ZSM-5 molecular sieve single crystals were then dispersed into a confocal culture dish and placed on the stage of a super-resolution fluorescence microscope. Before the test, the confocal plane of the super-resolution fluorescence microscope was adjusted so that it was aligned with the center plane of the ZSM-5 single crystal sample. 4-[4-dimethylaminophenylvinyl]-1-iodinated methylpyridine molecule was selected as the fluorescent probe molecule, and deionized water was used as the solvent. At a given temperature of 25°C, 2 mL of a fluorescent probe solution with a concentration of 20 μmol / L was added to the confocal culture dish, the fluorescence signal acquisition time resolution was 10 s, and the fluorescence signal intensity at each moment was recorded. The fluorescence signals at each moment were normalized, and the initial stage of the normalized curve that changes with time was processed using formula (1). The surface permeability of the probe molecule in the ZSM-5 molecular sieve single crystal was obtained by fitting: α = 2.7 × 10 -8 m / s, and the coefficient of determination is 0.996, indicating that the calculated results have high credibility. Further processing the normalized curve of the time-varying phase according to formula (2), the intracrystalline diffusion coefficient D = 9.5 × 10 -11 m / s 2 , the coefficient of determination is 0.972, indicating that the calculated results have high credibility.

[0052] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for visually recording the diffusion process of a single crystal porous material, characterized in that: The steps include: The porous material crystals are dispersed into a fluorescence confocal culture dish, and a fluorescent probe solution is added to disturb the single crystal porous material. The fluorescence signal image of the single crystal porous material is continuously recorded using a super-resolution fluorescence microscope, thereby obtaining an image of the surface penetration and intracrystalline diffusion process of the single crystal porous material evolving over time. The porous material crystals are dispersed into a fluorescence confocal culture dish, and then the focus of the super-resolution fluorescence microscope is adjusted to the top surface of the single crystal porous material. A fluorescent probe solution is added to disturb the single crystal porous material. The fluorescence signal image of the single crystal porous material is continuously recorded by the super-resolution fluorescence microscope, thereby obtaining an image of the surface permeation process of the single crystal porous material evolving over time. The porous material crystals are dispersed into a fluorescent confocal culture dish, and then the focal plane of the super-resolution fluorescence microscope is adjusted to the center plane of the single crystal porous material. A fluorescent probe solution is added to disturb the single crystal porous material. The fluorescence signal image of the single crystal porous material is continuously recorded by the super-resolution fluorescence microscope, thereby obtaining an image of the surface penetration and intracrystalline diffusion process of the single crystal porous material over time. The following steps are also included: (a) When recording the fluorescence signal image of a single-crystal porous material, the fluorescence intensity F is recorded; where: the initial moment corresponds to the intensity F0, and the moment t corresponds to the intensity F t , the corresponding intensity F at adsorption equilibrium ∞ ; (b) Fluorescence intensity F corresponding to the adsorption equilibrium reached by the single crystal porous material under the perturbation of the fluorescent probe ∞ , the measured fluorescence intensity change data were normalized using formula (1) to obtain the normalized probe adsorption concentration change curve over time In formula (1), m t represents the adsorption amount in the single crystal porous material at each moment, m ∞ It represents the adsorption amount of single crystal porous material at adsorption equilibrium; (c) When the adsorption time is 0-40 seconds, the surface permeability is determined using the control equation shown in formula (2): α , In formula (2), t represents the adsorption time, and l represents the characteristic length of the single crystal porous material; (d) Based on the surface permeability obtained by formula (2), the intracrystalline diffusion coefficient of the single crystal porous material is calculated by formula (3): D , In formula (3), L represents the ratio of the characteristic time of intracrystalline diffusion to surface penetration, β n Represents the parameters in the equation being solved.

2. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The single crystal porous material is calcined at a temperature of 550-650° C. for 24-72 hours.

3. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The fluorescent probe includes at least one of trans-4-[4-dimethylaminostyryl]-1-methylpyridine iodide, 4-(4-dimethylaminostyryl)-1-methylpyridine iodide, 4-(4-dimethylaminostyryl)methylpyridine iodide, 4',6-diamidino-2-phenylindole, and pyronin G.

4. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The concentration of the fluorescent probe is 1-100 μmol / L.

5. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The concentration of the fluorescent probe is 5-20 μmol / L.

6. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The super-resolution fluorescence microscope records fluorescence signal images with a time resolution of 3 to 10 seconds.

7. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The super-resolution fluorescence microscope used includes at least one of a co-structured light microscope, a stimulated emission diffraction microscope and a random optical reconstruction microscope.

8. The method for visually recording the diffusion process of a single crystal porous material according to claim 1, characterized in that: The coefficient of determination formula (4) is used to determine the error between the curve fitted by the equation (3) and the experimental value to determine the accuracy of the method; In formula (4), R 2 represents the coefficient of determination between the calculated fit and the experimental measurement, m t fit It means that formula (3) fits the adsorption amount at each moment, It represents the average value of the adsorption amount at each time.

9. The method for visually recording the diffusion process of a single crystal porous material according to claim 8, characterized in that: The surface permeability and intracrystalline diffusion coefficient obtained by fitting calculation are substituted into the governing equation, which is consistent with the experimental data of the change of adsorption concentration of single crystal porous materials with time, and the determination coefficient is 0.95~1.

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