A method for determining the magnitude of interlayer confinement effects in two-dimensional films using single-molecule fluorescence.

Abstract

This invention discloses a method for determining the magnitude of interlayer confinement in a two-dimensional membrane using single-molecule fluorescence, wherein the two-dimensional membrane is a vermiculite two-dimensional membrane. The method includes: providing a vermiculite dispersion containing rhodamine 6G; preparing the vermiculite dispersion containing rhodamine 6G into a membrane; and detecting the normalized fluorescence intensity of rhodamine 6G in the membrane. A higher normalized fluorescence intensity of rhodamine 6G indicates a weaker interlayer confinement in the vermiculite two-dimensional membrane; a lower normalized fluorescence intensity of rhodamine 6G indicates a stronger interlayer confinement in the vermiculite two-dimensional membrane. This invention proposes using the normalized fluorescence intensity of a single-molecule fluorescent probe in a two-dimensional membrane to determine the magnitude of the confinement space constraint. This method is of great significance for guiding the design of separation membranes and understanding separation mechanisms.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, and more specifically, relates to a method for determining the magnitude of interlayer confinement effect in two-dimensional membranes using single-molecule fluorescence. Background Technology

[0002] With the increasing demands for environmental protection and energy, gas and ion separation technologies are becoming increasingly important in industrial production, environmental protection, and energy utilization. Separation membranes, as a highly efficient and energy-saving separation method, have been widely used in gas separation, water treatment, air purification, and many other fields. However, accurately assessing the mass transfer behavior and confinement effect of gases within separation membranes remains a significant scientific and technological challenge.

[0003] The confinement effect within sub-nanometer capillaries enables various anomalous phenomena in ion transport, such as ballistic gas diffusion, frictionless ion transport, and water permeation. In particular, the development of two-dimensional (2D) materials has provided opportunities to fabricate sub-nanometer capillaries whose widths can be tunable, making it possible to study the fundamental principles of confined mass transport. The interlayer confinement between 2D materials influences the selectivity and transport velocity of molecules within these capillaries. Inspired by these findings, various membranes based on 2D materials have been designed to achieve gas or ion separation, transcending the traditional trade-off between permeability and selectivity. However, current understanding of interlayer confinement as one of the main influencing factors in selective membranes of 2D materials remains largely based on simulations or assumptions derived from performance evaluations. Therefore, developing a method for studying interlayer confinement is urgently needed for the rational design and further optimization of selective membranes with 2D capillaries.

[0004] However, current state-of-the-art characterization techniques, including transmission electron microscopy, scanning probe microscopy, X-ray diffraction, and dielectric spectroscopy, can only provide indirect evidence of interlayer confinement, such as capillary size or the filling of the permeating medium. Some pioneering studies have utilized the fluorescence signal of reversible protonation defects to visualize ion diffusion pathways along two-dimensional boron nitride surfaces. Fluorescence microscopy, with its ability to utilize spatial and temporal resolution, is considered an effective technique for tracking dynamic processes within capillaries. However, visualizing interlayer confinement, as an invisible interaction, remains an unresolved challenge. Summary of the Invention

[0005] 1. The problem to be solved

[0006] The purpose of this invention is to provide a novel visualization method based on spectroscopic techniques, particularly fluorescence techniques, for accurately assessing the magnitude of the confinement effect on gases or liquids within a separation membrane.

[0007] Based on the above-mentioned objectives of this invention, and addressing the problem that changes in the interlayer confinement effect of existing two-dimensional materials are difficult to directly visualize and monitor, this invention provides a judgment method based on Rhodamine 6G (R6G) indicator. This method utilizes spectroscopic detection and fluorescence microscopy, employing single-molecule fluorescence to directly determine the magnitude of the interlayer confinement effect in two-dimensional materials.

[0008] Based on the above-mentioned objectives of this invention, and addressing the problem that it is difficult to conduct in-situ visual monitoring of changes in interlayer confinement effects of existing two-dimensional materials under different humidity conditions, an in-situ visual monitoring method is provided, which realizes the visual observation of interlayer confinement effects.

[0009] 2. Technical Solution

[0010] This invention discovers that increased interlayer constraint in two-dimensional films reduces the dihedral angle between xanthylium and benzyl in the R6G molecule, leading to attenuation of the R6G fluorescence signal. Based on this, this invention uses the normalized fluorescence intensity of R6G as a standard for judging the magnitude of interlayer constraint in two-dimensional films. The magnitude of interlayer constraint in two-dimensional films under different conditions was determined using fluorescence detection, and the above-mentioned determination method was experimentally verified.

[0011] This invention proposes using R6G as a single-molecule fluorescent probe to monitor the confinement effect of R6G between two-dimensional membrane layers through single-molecule fluorescence emission spectroscopy and fluorescence microscopy, thereby achieving visual monitoring of changes in the magnitude of the confinement effect. This method provides a new direction and technical support for the design and development of efficient gas and ion separation membranes.

[0012] [A method for determining the magnitude of interlayer confinement effects in two-dimensional films using single-molecule fluorescence]

[0013] The first aspect of this invention provides a method for determining the magnitude of interlayer confinement effects in two-dimensional films using single-molecule fluorescence, comprising:

[0014] Provides dispersions of two-dimensional materials containing fluorescent molecules;

[0015] A film was prepared from a dispersion of two-dimensional materials containing fluorescent molecules;

[0016] The normalized fluorescence intensity of fluorescent molecules in the membrane was detected;

[0017] The higher the normalized fluorescence intensity of the fluorescent molecule, the smaller the confinement effect between the two-dimensional film layers.

[0018] The lower the normalized fluorescence intensity of the fluorescent molecule, the greater the confinement effect between the two-dimensional film layers.

[0019] The normalized fluorescence intensity is the ratio of the fluorescence intensity to the ultraviolet absorption intensity of the film.

[0020] Depending on the fluorescent molecule, the fluorescence intensity is the maximum fluorescence intensity at the optimal excitation wavelength, and the ultraviolet absorption intensity is the maximum ultraviolet absorption intensity.

[0021] The fluorescent molecule should meet the requirement that its fluorescence changes under two-dimensional interlayer confinement.

[0022] As a preferred embodiment of any of the first aspects of the present invention, the two-dimensional membrane may be a two-dimensional gas separation membrane or a two-dimensional ion separation membrane.

[0023] [A method for determining the magnitude of interlayer confinement effect in vermiculite two-dimensional films using single-molecule fluorescence]

[0024] A second aspect of this invention provides a method for determining the magnitude of interlayer confinement effect in a two-dimensional film using single-molecule fluorescence, wherein the two-dimensional film is a vermiculite two-dimensional film;

[0025] Provides a vermiculite dispersion containing 6g of rhodamine;

[0026] A vermiculite dispersion containing 6g of rhodamine was prepared into a film;

[0027] The normalized fluorescence intensity of Rhodamine 6G in the membrane was detected;

[0028] The greater the normalized fluorescence intensity of Rhodamine 6G, the smaller the interlayer confinement effect of the vermiculite two-dimensional film.

[0029] The smaller the normalized fluorescence intensity of Rhodamine 6G, the greater the interlayer confinement effect of the vermiculite two-dimensional film.

[0030] The normalized fluorescence intensity is the ratio of the fluorescence intensity to the ultraviolet absorption intensity of the film.

[0031] The fluorescence intensity is the maximum fluorescence intensity of Rhodamine 6G at the optimal excitation wavelength, and the ultraviolet absorption intensity is the maximum ultraviolet absorption intensity of Rhodamine 6G.

[0032] Vermiculite (V) is a natural layered silicate mineral belonging to the mica group. It possesses unique expansion properties and excellent thermal insulation, heat preservation, moisture absorption, and adsorption capabilities. V nanosheets exhibit uniform interlayer channels, showing promising application prospects in membrane separation and are considered an ideal material for preparing high-performance gas separation membranes.

[0033] R6G is an organic fluorescent dye with high fluorescence quantum yield, good photostability, and a broad spectral range. It exhibits characteristic absorption and emission changes in response to external stimuli. In the structure of the solution-based fluorescent probe R6G, xanthylium and benzyl form an 80.4° dihedral angle, resulting in strong fluorescence emission intensity. However, the interlayer of two-dimensional materials possesses different confinement forces. When R6G is situated between two-dimensional material layers in different confinement states, it experiences varying degrees of constraint, leading to changes in the dihedral angle between xanthylium and benzyl, and consequently, altering the fluorescence emission intensity.

[0034] Based on this principle, this invention explores the changes in interlayer constraint in two-dimensional capillaries by measuring the fluorescence emission intensity changes of the fluorescent probe R6G between vermiculite two-dimensional film layers, and visually determines the magnitude of the interlayer confinement effect of the two-dimensional film layers.

[0035] When the confinement space between the layers of a two-dimensional material decreases, the molecules sandwiched between two nanosheets tend to flatten, resulting in a decrease in the dihedral angle and R6G fluorescence quenching. Conversely, when the confinement space between the layers of a two-dimensional material increases, the molecules sandwiched between two nanosheets tend to be the same as those in solution, resulting in an increase in the dihedral angle and enhanced R6G fluorescence.

[0036] As a preferred embodiment of any of the second aspects of the present invention, the thickness of the vermiculite two-dimensional film is 1 to 10 μm.

[0037] Preferably, the thickness of the vermiculite two-dimensional film is 3–5 μm. Two-dimensional films with a thickness of less than 5 μm tend to be transparent, which facilitates the observation of changes in fluorescence emission intensity.

[0038] As a preferred embodiment of any of the second aspects of the present invention, the vermiculite two-dimensional film is a vermiculite two-dimensional film doped with cellulose nanofibers, and the vermiculite dispersion is a vermiculite dispersion containing cellulose nanofibers.

[0039] As a preferred embodiment of any of the second aspects of the present invention, the vermiculite two-dimensional film is Al 3+ The doped vermiculite two-dimensional film was prepared by using the vermiculite dispersion containing Rhodamine 6G, and then the film was subjected to an Al-containing film. 3+ It was obtained by soaking in a solution.

[0040] As a preferred embodiment of any of the second aspects of the present invention, the vermiculite two-dimensional film is composed of cellulose nanofibers and Al. 3+ A co-doped vermiculite two-dimensional film, wherein the vermiculite dispersion is a vermiculite dispersion containing cellulose nanofibers, is prepared by means of the vermiculite dispersion containing Rhodamine 6G, and then the film is coated with an Al-containing membrane. 3+ It was obtained by soaking in a solution.

[0041] As a preferred embodiment of any second aspect of the present invention, the cellulose nanofibers in the vermiculite two-dimensional film have a mass percentage content of 0.01 to 33% of the vermiculite.

[0042] As a preferred embodiment of any of the second aspects of the present invention, the Al 3+ Al in solution 3+ The concentration is 10 -5 ~10 -1 mol / L.

[0043] As a preferred embodiment of any of the second aspects of the present invention,

[0044] In the vermiculite dispersion containing Rhodamine 6G, the concentration of vermiculite is 0.05–10 mg / mL;

[0045] The concentration of rhodamine 6G in the vermiculite dispersion is 10. -6 ~10 -5 mol / L.

[0046] As a preferred embodiment of any of the second aspects of the present invention, the normalized fluorescence intensity is the ratio of the fluorescence emission intensity with a fluorescence emission peak at 560 nm when the fluorescence excitation wavelength is 532 nm to the intensity of the absorption peak at 532 nm in the ultraviolet-visible spectrum.

[0047] [A method for determining the magnitude of interlayer confinement effects in two-dimensional films under different relative humidity using single-molecule fluorescence]

[0048] A third aspect of this invention provides a method for determining the magnitude of interlayer confinement effect of a two-dimensional film under different relative humidities using single-molecule fluorescence, wherein the two-dimensional film is a vermiculite two-dimensional film;

[0049] Provides a vermiculite dispersion containing 6g of rhodamine;

[0050] A vermiculite dispersion containing 6g of rhodamine was prepared into a film;

[0051] The normalized fluorescence intensity of Rhodamine 6G in the membrane was detected under different relative humidities;

[0052] The higher the normalized fluorescence intensity of Rhodamine 6G, the smaller the confinement effect between the two-dimensional film layers.

[0053] The lower the normalized fluorescence intensity of Rhodamine 6G, the greater the confinement effect between the two-dimensional film layers.

[0054] The normalized fluorescence intensity is the ratio of the fluorescence intensity to the ultraviolet absorption intensity of the film.

[0055] It is known in the prior art that the higher the relative humidity, the weaker the confinement effect between the two-dimensional film layers, and the larger the interlayer spacing. This is consistent with the results of this invention, which uses the normalized fluorescence intensity of Rhodamine 6G to determine the magnitude of the confinement effect between the two-dimensional film layers.

[0056] The enhancement and reduction of fluorescence emission can be determined by detecting fluorescence emission spectra or observing fluorescence microscopy. If necessary, the normalized fluorescence intensity can be further calculated. Therefore, the method of this invention makes it more intuitive to determine the magnitude of the confinement effect between two-dimensional film layers under different relative humidities.

[0057] As a preferred embodiment of any of the third aspects of the present invention, the relative humidity is 0 to 100% RH.

[0058] 3. Beneficial effects

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] (1) In this invention, it is proposed for the first time to use the normalized fluorescence intensity of a single-molecule fluorescent probe in a two-dimensional membrane to determine the size of the confinement space constraint force. Specifically, when the constraint force on the R6G fluorescent probe between the two-dimensional material layers increases, the dihedral angle between xanthylium and benzyl in its molecule decreases, and the fluorescence emission intensity increases. Conversely, when the two-dimensional confinement space increases, the constraint force between the layers decreases, the constraint force on the R6G fluorescent probe between the layers decreases, the dihedral angle between xanthylium and benzyl increases, and the fluorescence emission intensity increases. In this way, the change in the size of the confinement space of the two-dimensional separation membrane under different external environmental conditions or different doping conditions can be accurately determined. This is of great significance for guiding the design of the separation membrane and understanding the separation mechanism.

[0061] (2) The present invention realizes the visualization of the size change of the two-dimensional confined channel in the two-dimensional separation membrane by using fluorescence microscopy.

[0062] (3) This invention uses fluorescence emission spectroscopy or fluorescence microscopy to determine the enhancement and reduction of R6G fluorescence emission in two-dimensional films under different relative humidity, and obtains the magnitude of interlayer confinement effect of two-dimensional films under different humidity conditions. This enables in-situ real-time observation and makes the determination of the magnitude of interlayer confinement effect of two-dimensional films under different relative humidity more intuitive. Attached Figure Description

[0063] Figure 1 A schematic diagram illustrating the mechanism of monitoring the confined state of a two-dimensional channel using R6G;

[0064] Figure 2 (a) is the cross-section and (b) is the plane of the V two-dimensional membrane;

[0065] Figure 3 :

[0066] (a) Visible and ultraviolet absorption spectra and fluorescence emission spectra of R6G solution (excitation wavelength 532 nm);

[0067] (b) Visible and ultraviolet absorption spectra and fluorescence emission spectra of V-R6G dispersion (excitation wavelength 532 nm);

[0068] (c) Comparison of fluorescence intensity between R6G solutions with different R6G concentrations and V-R6G dispersion;

[0069] (d) The ratio of fluorescence intensity of different concentrations of R6G under the spatial confinement of vermiculite two-dimensional film and without the influence of the film. R6G / I R6G / V (Excitation wavelength 532nm);

[0070] Figure 4 :

[0071] (a) Comparison of XRD patterns of V-R6G CNF two-dimensional separation membranes with different CNF addition amounts;

[0072] (b) Comparison of fluorescence emission spectra of V-R6G and V-R6G 2CNF;

[0073] (c) Normalized fluorescence intensity of V-R6G CNF two-dimensional separation membranes with different CNF addition amounts;

[0074] (d) Fluorescence micrograph of the V-R6G two-dimensional film;

[0075] (e) A fluorescence microscope image of the V-R6G 2CNF two-dimensional film;

[0076] Figure 5 :

[0077] (a)Al 3+ Linear relationship between ion concentration and normalized fluorescence intensity of R6G;

[0078] (b) Different Al 3+ V-R6G CNF Al obtained by ion concentration 3+ XRD pattern of a two-dimensional membrane;

[0079] Figure 6 :

[0080] (a) Schematic diagram of an experiment using humidity to change the size of the confined channels of a two-dimensional separation membrane;

[0081] (b) Fluorescence microscopy observation of the fluorescence changes of V-R6G two-dimensional film under gradually increasing relative humidity over time. Detailed Implementation

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0083] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0084] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0085] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0086] I. Materials

[0087] Multilayer vermiculite (V) clay was purchased from Chenxing Company; LiCl, NaCl, R6G powder was purchased from Heowns, and cellulose nanofibers (CNF) were purchased from Frontier Nanotech. All chemicals were used directly without further purification.

[0088] II. Preparation of Separation Membranes

[0089] Based on the principle of this technical solution, this technical solution uses fluorescence spectroscopy to monitor the changes in the confinement channels of a two-dimensional separation membrane, which is suitable for studying the confinement effect between nanosheet layers in two-dimensional gas and ion separation membranes.

[0090] In this embodiment, the specific two-dimensional material is vermiculite nanosheets (V nanosheets), and the preparation steps are as follows:

[0091] 1. Synthesis of V nanosheets

[0092] First, V nanosheets were prepared using an ion-intercalation strategy. Specifically, 0.20 g of thermally expanded V clay was intercalated and mixed with 200 mL of saturated NaCl, and the mixture was magnetically stirred at 120 °C for 24 hours. After the reaction, the product was filtered through a polyethersulfone (PES) membrane and washed with plenty of deionized water to remove excess NaCl. Subsequently, the intercalated NaCl nanosheets were... + V was mixed with 200 mL of 2 M LiCl solution and magnetically stirred at 120 °C for 24 hours. After this reaction, the product was washed again and filtered to remove excess LiCl, yielding Li. + Intercalation of V. During ion intercalation, the intercalation product was dispersed in ultrapure water and sonicated for 30 minutes to exfoliate it into few-layer V nanosheets. The dispersion was then centrifuged at 3000 rpm for 30 minutes to remove unexfoliated V clay from the bottom of the centrifuge tube; this step was repeated three times. Next, the dispersion was centrifuged at 10000 rpm for 30 minutes to remove smaller nanosheets from the supernatant; this step was also repeated three times. The colloidal suspension at the bottom of the centrifuge tube was resuspended in ultrapure water to obtain a solution containing few-layer V nanosheets. To further determine the V nanosheet concentration, 10 ml of the obtained few-layer nanosheets were vacuum filtered and centrifuged. The final two-dimensional membrane was weighed, and the V nanosheet concentration was determined to be 0.3 mg / ml.

[0093] 2. Assembly of V two-dimensional membranes

[0094] The dispersion of few-layer V nanosheets prepared in the previous step was used to assemble a two-dimensional membrane by vacuum filtration.

[0095] 3. V-R6G dispersion, V-R6G two-dimensional membrane, V-R6G CNF two-dimensional membrane, and V-R6G CNFAl for monitoring confinement effects. 3+ Preparation of two-dimensional membranes

[0096] Preparation of V-R6G dispersion: Mix 1 ml of V nanosheet dispersion (0.3 mg / ml) with 1 ml of R6G solution (1 × 10⁻⁶ mg / ml). - 5 Mix thoroughly (mol / L), and finally add water to make the total volume of the solution 10 ml.

[0097] Preparation of V-R6G two-dimensional film: 10 ml of V nanosheet dispersion (0.3 mg / ml) and 2 ml of R6G solution (1 × 10⁻⁶ g / ml) were mixed. - 5 Mix thoroughly with mol / L, add water to make the total volume of the solution 20 ml, and finally filter to obtain the V-R6G two-dimensional membrane and then dry it.

[0098] Preparation of V-R6G CNF two-dimensional membrane: CNF solution (0.5, 1, 2 ml, 0.5 mg / ml) was added to the V-R6G dispersion and stirred thoroughly to make it evenly mixed. Finally, water was added to make the total volume of the solution 20 ml. Finally, the V-R6G CNF two-dimensional membrane was obtained by suction filtration and then dried.

[0099] V-R6G CNF Al 3+ Preparation of two-dimensional membranes: The V-R6G 1CNF two-dimensional membrane obtained by vacuum filtration was divided into five equal parts, and then immersed in Al at different concentrations. 3+ 12h in solution (Al) 3+ The solutions were dried after being prepared with concentrations of 0.00001, 0.001, 0.1, and 1 mol / L.

[0100] III. Characterization of V two-dimensional films

[0101] 1. Optical microscope image of a V two-dimensional film.

[0102] like Figure 2 The image shown is a SEM image of the cross-section and plane of the V two-dimensional membrane synthesized in Part 2 of Section II, "Preparation of Separation Membrane".

[0103] IV. Spectral Testing

[0104] 1. Principles of Spectroscopy

[0105] The principle of fluorescence spectroscopy is as follows: when a substance absorbs light of a specific wavelength, electrons transition from the ground state to an excited state. They then return to a lower excited state through a non-radiative relaxation process, and finally release energy as photons of a longer wavelength when returning from the excited state to the ground state. This process is called fluorescence emission. Fluorescence spectroscopy provides detailed information about the optical properties of a substance and its environment by measuring the fluorescence intensity at different wavelengths.

[0106] The principle of ultraviolet-visible spectroscopy is that when a substance absorbs light in the ultraviolet or visible region, electrons in its molecules transition from the ground state to the excited state, forming an absorption spectrum. By measuring the absorbance at different wavelengths, the characteristic absorption curves of the substance can be obtained, thereby identifying the type and concentration of the substance.

[0107] In this technical solution, R6G is used as an indicator, and a V two-dimensional membrane is used as the site for confining the channel. This is achieved through CNF and Al... 3+ The size of the confinement space was adjusted by humidity. The concentration of R6G molecules was detected using a UV-Vis photometer. After the R6G molecules were affected by the size of the confinement space between the two-dimensional film layers, their molecular structure changed. These changes were monitored by fluorescence spectroscopy and fluorescence microscopy. These changes in fluorescence efficiency can accurately show the changes in the confinement space and confinement effect between the two-dimensional material layers, thus providing guidance for efficient ion and gas separation.

[0108] 2. Spectral Measurement

[0109] First, place the V-R6G dispersion prepared in section II, "Preparation of Separation Membrane," into a cuvette and collect its fluorescence and ultraviolet (UV) spectra. During measurement, tests should be performed in ascending order of concentration to avoid testing errors caused by residual high-concentration solutions. The excitation wavelength for the fluorescence emission spectrum is 532 nm, and the measurement wavelength range for the UV-Vis absorption spectrum is 200-700 nm.

[0110] V. Spectroscopic testing of mixtures of R6G and V at different concentrations in solution.

[0111] like Figure 3 As shown in a and 3b, the UV absorption peak of R6G is at 532 nm, and the emission peak of its fluorescence spectrum is at 560 nm. Figure 3 Comparing a and 3b, it can be seen that at the same concentration, the emission peak position of the fluorescence spectrum does not shift after R6G enters the interlayer, but the intensity decreases significantly. Figure 3 c represents the fluorescence intensity decay when different concentrations of R6G solution are added to solution V. To maximize the response of the fluorescent molecules to the confinement effect, the R6G concentration was increased from 1×10⁻⁶ to 1×10⁻⁶. -6 Adjust to 1×10 -5 The concentration of vermiculite was controlled at 0.3 mg / ml, and fluorescence attenuation was used (the ratio of fluorescence intensity at 560 nm to I0.05). R6G / I R6G+v To assess the sensitivity of the response to confinement effects, the concentration of R6G decreases. R6G / I R6G+v The value of ) increased to 23.21. Figure 3 d) Further reducing the R6G concentration would cause the fluorescence signal to weaken below the detection limit in subsequent spectroscopic and microscopic studies; therefore, the dye concentration was set to 10. - 6 mol / L to maximize the fluorescence response to confinement effects.

[0112] VI. Spectral Testing of CNF-Extended V-R6G Two-Dimensional Membrane Confinement Space

[0113] like Figure 4a. In this section, V-R6G 0.5CNF represents 0.5 ml of CNF added to the V-R6G CNF synthesized in Part 3 of Section II, "Preparation of Separation Membrane" (CNF accounts for approximately 8.3% of the mass of V); V-R6G 1CNF represents 1 ml of CNF added to the V-R6G CNF synthesized in Part 3 of Section II, "Preparation of Separation Membrane" (CNF accounts for approximately 16.7% of the mass of V); and V-R6G 2CNF represents 2 ml of CNF added to the V-R6G CNF synthesized in Part 3 of Section II, "Preparation of Separation Membrane" (CNF accounts for approximately 33% of the mass of V). XRD analysis of the V-R6G CNF two-dimensional membrane obtained in Section II, "Preparation of Separation Membrane" showed that with the increase of CNF content, the XRD peak of the 002 crystal plane of V shifted towards a smaller angle, and the peak width also broadened slightly. To verify the application of R6G in visualizing the confinement effect in two-dimensional capillaries, vermiculite (V) films exhibited a UV absorption peak at 532 nm, but the fluorescence signal was weak, indicating that the interlayer space of the two-dimensional capillaries composed of vermiculite was in a confined state. However, when cellulose nanofibers (V-R6G CNF) were inserted to expand the capillary (interlayer space), fluorescence appeared ( Figure 4 b). When the CNF mass content increased to 33% of the V content, the normalized fluorescence intensity gradually increased by 9 times compared to the absence of CNF. Figure 4 c) This is due to the weakened confinement effect in the dilated capillary. Furthermore, based on the R6G indicator, fluorescence microscopy can observe the spatial resolution confinement effect in the capillary. Figure 4 (de). The VR6G film exhibits a weak fluorescence signal, indicating interlayer constraint on the film plane. In contrast, fluorescence is observed on the VR6G CNF film, particularly in the ripple region, primarily due to the reduced interlayer constraint caused by CNF doping. This experiment demonstrates the visualization of interlayer constraint based on the R6G indicator.

[0114] VII. Al 3+ Spectral testing of crosslinked extended V-R6G CNF two-dimensional membrane confinement space.

[0115] Ionic crosslinking, as another method for regulating interlayer constraint, is widely used in the design of selective membranes. This invention introduces a typical crosslinking agent, Al, by immersing a V-R6G CNF membrane in an aqueous solution of Al(NO3)3·9H2O. 3+ ( Figure 5 a insertion). With Al 3+ As the concentration increased from 0 to 1 mol / L, the normalized fluorescence intensity of the R6G indicator in the vermiculite capillary increased by 201.3%, indicating a weakening of interlayer constraint. Figure 5 a). Meanwhile, the XRD results further validated that, with Al...3+ As the concentration increases from 0 to 1 mol / L, the capillary interlayer space changes from Expand to ( Figure 5 b), that is, Al 3+ The crosslinking further weakens the confinement in the capillaries constructed from V, which is consistent with the reduced confinement effect shown by the fluorescent indicator.

[0116] 8. In-situ observation of changes in the interlayer confinement effect of V-R6G under different humidity levels using fluorescence microscopy

[0117] To demonstrate the application value of R6G molecular probes in dynamic process research, the fluorescence intensity of V-R6G films under different humidity levels was monitored using fluorescence microscopy. Water was inserted into the interlayer space of a two-dimensional capillary by adding humidity. Therefore, a nitrogen gas saturated with 100% relative humidity was blown into a chamber beneath the V-R6G film. Figure 6 a). Then, fluorescence images are captured to track the dynamic changes in interlayer constraints ( Figure 6 (b) Under 100% RH humidity input, the dark area (yellow dashed line area) gradually brightens, indicating that the interlayer confinement effect weakens after water enters the capillary. Therefore, the confinement effect based on R6G can reveal the dynamic changes in interlayer constraints.

[0118] This invention demonstrates the visualization of interlayer confinement effects using R6G as a molecular probe. Interlayer constraints reduce the dihedral angle between xanthylium and benzyl in the R6G molecule, leading to fluorescence signal attenuation. Therefore, R6G was used to probe interlayer constraints in two-dimensional capillaries composed of vermiculite and its composites. The fluorescence signal of R6G is quenched in the original vermiculite channels, while the embedding of cellulose nanofibers reduces the interlayer confinement effect, further enhancing the fluorescence of R6G.

[0119] Furthermore, this invention is also applicable to assessing constraints caused by geometric deformations (such as ripples) and ionic crosslinking by tracking the spatial and spectral signals of R6G. With the aid of the R6G molecular probe, fluorescence microscopy can monitor the dynamic changes in interlayer confinement, providing temporal and spatial resolution information. Therefore, the strategy of this invention provides a direct means of visualizing interlayer constraints in two-dimensional capillaries, which will facilitate the design of highly efficient selective films based on two-dimensional materials.

[0120] The above description provides an illustrative overview of the present invention and its embodiments. This description is not restrictive, and the embodiments shown are merely one example of the invention's implementation. Actual implementations are not limited to these examples. Therefore, if those skilled in the art are inspired by this description and design similar implementations and examples without departing from the spirit of the invention, such designs should fall within the scope of protection of the present invention.

Claims

1. A method for determining the magnitude of interlayer confinement effects in two-dimensional films using single-molecule fluorescence, characterized in that, The two-dimensional film is a vermiculite two-dimensional film; the method includes: Provides a vermiculite dispersion containing 6g of rhodamine; A vermiculite dispersion containing 6g of rhodamine was prepared into a film; The normalized fluorescence intensity of Rhodamine 6G in the membrane was detected; The higher the normalized fluorescence intensity of Rhodamine 6G, the smaller the interlayer confinement effect of the vermiculite two-dimensional film. The lower the normalized fluorescence intensity of Rhodamine 6G, the greater the interlayer confinement effect of the vermiculite two-dimensional film. The normalized fluorescence intensity is the ratio of the fluorescence intensity to the ultraviolet absorption intensity of the film.

2. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 1, characterized in that, The thickness of the vermiculite two-dimensional film is 1~10μm.

3. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 1, characterized in that, The vermiculite two-dimensional film is a vermiculite two-dimensional film doped with cellulose nanofibers, and the vermiculite dispersion is a vermiculite dispersion containing cellulose nanofibers.

4. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 1, characterized in that, The vermiculite two-dimensional film is Al 3+ The doped vermiculite two-dimensional film was prepared by using the vermiculite dispersion containing Rhodamine 6G, and then the film was subjected to an Al-containing film. 3+ It was obtained by soaking in a solution.

5. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 1, characterized in that, The vermiculite two-dimensional film is composed of cellulose nanofibers and Al. 3+ A co-doped vermiculite two-dimensional film, wherein the vermiculite dispersion is a vermiculite dispersion containing cellulose nanofibers, is prepared by means of the vermiculite dispersion containing Rhodamine 6G, and then the film is coated with an Al-containing membrane. 3+ It was obtained by soaking in a solution.

6. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 3 or 5, characterized in that, In the vermiculite two-dimensional membrane, the mass percentage of cellulose nanofibers is 0.01~33% of vermiculite.

7. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to claim 4 or 5, characterized in that, In the vermiculite dispersion, the Al 3+ The concentration is 10 -5 ~10 -1 mol / L.

8. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to any one of claims 1 to 5, characterized in that: In the vermiculite dispersion containing Rhodamine 6G, the concentration of vermiculite is 0.05~10 mg / mL; The concentration of rhodamine 6G in the vermiculite dispersion is 10. -6 ~10 -5 mol / L.

9. The method for determining the magnitude of interlayer confinement effect in two-dimensional films using single-molecule fluorescence according to any one of claims 1 to 5, characterized in that, The normalized fluorescence intensity is the ratio of the fluorescence emission intensity at a fluorescence excitation wavelength of 532 nm with the fluorescence emission peak at 560 nm to the absorption intensity at 532 nm in the UV-Vis absorption spectrum.

10. A method for determining the magnitude of interlayer confinement effect in two-dimensional films under different relative humidities using single-molecule fluorescence, characterized in that, The two-dimensional membrane is a vermiculite two-dimensional membrane; Provides a vermiculite dispersion containing 6g of rhodamine; A vermiculite dispersion containing 6g of rhodamine was prepared into a film; The normalized fluorescence intensity of Rhodamine 6G in the membrane was detected under different relative humidities; The higher the normalized fluorescence intensity of Rhodamine 6G, the smaller the interlayer confinement effect of the vermiculite two-dimensional film. The lower the normalized fluorescence intensity of Rhodamine 6G, the greater the interlayer confinement effect of the vermiculite two-dimensional film. The normalized fluorescence intensity is the ratio of the fluorescence intensity to the ultraviolet absorption intensity of the film.

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