Amorphous metal-organic framework microspheres, their preparation method and applications
The amorphous metal-organic framework microspheres were prepared by a solvothermal method, which solved the problem of crystal damage caused by traditional methods, realized efficient whispering-gallery mode microcavity signals, enhanced the security of information encoding, and simplified the preparation process.
Patent Information
- Application Number
- CN202411367364.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2044-09-29
AI Technical Summary
Traditional metal-organic framework (MOF) microcavities suffer from rigid polygonal boundaries due to the anisotropy of crystal growth, resulting in low optical confinement and significant light scattering losses. This makes it difficult to obtain effective microcavity signals at low power, limiting the development of high-resolution spectral coding. Furthermore, existing fabrication methods cause irreversible damage to the crystal, further restricting the material's applications.
Amorphous metal-organic framework microspheres were synthesized in one step using a solvothermal method. By controlling the concentration of organic molecules and heating conditions, smooth-surfaced microspheres were prepared to realize low-threshold whispering-gallery mode microcavities. The whispering-gallery mode signal switching was achieved by utilizing the framework breathing effect.
The prepared amorphous metal-organic framework microspheres have smooth circular boundaries and exhibit sharp whispering-gallery mode peaks, providing a hidden photonic barcode with high coding capability and high security, simplifying the preparation process and improving information security.
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Figure CN119241858B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photonics technology, specifically relating to an amorphous metal-organic framework microsphere, its preparation method, and its application. Background Technology
[0002] Luminescent metal-organic frameworks (MOFs) combine the advantages of designable organic ligands, diverse metal nodes, and infinitely combinable fluorescence mechanisms, leading to their widespread application in optical sensors, information storage, and anti-counterfeiting. The rapid development of anti-counterfeiting technologies places increasingly higher demands on the design of MOF devices with accurate identification, large coding capacity, and strong security. However, traditional MOF systems are primarily based on broadband spectral signals, suffering from spectral overlap and low signal recognition resolution, severely impacting overall security levels. In contrast, MOF microcavity structures possess a series of distinguishable optical resonance mode peaks, modulated by microcavity size and external stimuli, providing a high-security platform for high-resolution spectral coding. To date, various MOF microcavities, including 1D microwires, 2D microplates, and 3D polyhedral structures, have been created to realize optically recordable and identifiable photonic barcodes. However, due to the anisotropy of crystal growth, these MOF microcavities typically have rigid polygonal boundaries, resulting in low optical confinement, large light scattering losses, and difficulty in obtaining effective microcavity signals at low power, hindering the development of simple, efficient, and intelligent devices. Amorphous metal-organic frameworks (MOFs) are generated by the non-periodic arrangement of coordination networks, allowing for the fabrication of smooth, spherical microcavity structures. These structures can effectively confine photons through continuous internal reflection, eliminating scattering losses and thus generating highly efficient whispering-gallery modes. However, most amorphous MOFs introduce disorder into crystalline MOFs through post-processing methods such as heating, pressurization, or ball milling. This typically requires complex fabrication processes and devices, and these methods are too aggressive, potentially causing irreversible damage to the crystal and limiting further applications of the material. Therefore, there is an urgent need for a gentler and simpler method to fabricate amorphous MOF microspheres and explore the application of their tunable whispering-gallery modes in anti-counterfeiting labels. Summary of the Invention
[0003] The purpose of this invention is to provide an amorphous metal-organic framework microsphere, its preparation method, and its application.
[0004] The technical concept of this invention is as follows: Metal-organic frameworks (MOFs) combine the advantages of designable luminescent organic ligands, diverse metal nodes, and infinitely combinable fluorescence mechanisms, making them an excellent platform for studying luminescent materials. Furthermore, amorphous MOFs, generated through the non-periodic arrangement of coordination networks, allow for the fabrication of low-threshold whispering-gallery mode (EMM) microcavities, such as hemispheres, isotropic spheres, and microdisks. In EEM microcavities, photons can propagate along the microcavity / air interface. This structure effectively confines photons through continuous internal reflection, thereby eliminating scattering losses. Therefore, amorphous MOF microspheres hold great promise for realizing low-threshold EEM microcavities. More importantly, utilizing the intrinsic framework breathing effect of MOFs, signal switching in EEM microcavities can be achieved, allowing for the design of covert photonic barcodes as anti-counterfeiting labels, which is beneficial for improving coding capabilities and enhancing information security.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for preparing amorphous metal-organic framework microspheres includes the following steps:
[0007] 1) Dissolve organic molecules and metal salt (cadmium nitrate) uniformly in an organic solvent (a good solvent for organic molecules) to obtain an organic solution; add water (a poor solvent for organic molecules) to the organic solution and sonicate to obtain a mixture;
[0008] 2) Pour the mixture into a glass bottle and then place it in an oven to heat;
[0009] 3) Remove and cool to room temperature, then wash the product three times with a washing solution made of organic solvent and water to obtain smooth amorphous metal-organic framework microspheres.
[0010] The organic molecule mentioned is 1,1,2,2-tetraphenyl[1,1'-biphenyl-4(1-H-tetrazole)ethylene](H4TTBE), with the following molecular structure:
[0011]
[0012] Furthermore, the organic solvent is N,N-dimethylformamide.
[0013] Furthermore, in the organic solution, the mass concentration of the organic molecule H4TTBE is 1.2-2 mg / mL, and the mass concentration of cadmium nitrate is 2 mg / mL.
[0014] Furthermore, the amorphous metal-organic framework microspheres have a size of 3-15 μm, preferably 5-10 μm. The microspheres of this size are selected because they have good whispering-gallery mode microcavity signals, thus realizing modulated whispering-gallery mode microcavity signals.
[0015] In this invention, the size of the microcavity can be controlled by changing the concentration of the organic molecule H4TTBE, thereby obtaining different modes of output signals. For example, when the mass percentage concentration of the organic molecule is 1.2 mg / mL, the microsphere size is about 3-5 μm; when the mass concentration of the organic molecule H4TTBE is 1.5 mg / mL, the microsphere size is 5-8 μm; and when the mass concentration of the organic molecule H4TTBE is 2 mg / mL, the microsphere size is about 8-10 μm.
[0016] Furthermore, in step 1), the volume ratio of water to organic solvent is 1:3 to 5, with 1:5 being a preferred ratio. Using this preferred ratio, amorphous metal-organic framework microspheres with more uniform dimensions can be prepared.
[0017] Furthermore, in step 1), the duration of the ultrasound is 5 to 6 minutes, and the frequency of the ultrasound is 40 to 45 kHz.
[0018] Furthermore, in step 2), the glass bottle can be filled with a solvent of 5 mL, 8 mL, or 10 mL, with 5 mL being the preferred option. Using this preferred option allows for the acquisition of a larger quantity of amorphous metal-organic framework microspheres.
[0019] Furthermore, in step 2), the heating temperature is 65-100℃ and the heating time is 12-24h. The preferred option is to heat at 85℃ for 18h. Under these conditions, the amorphous metal-organic framework microspheres have smooth surfaces and few cavity defects, and can obtain high-quality microcavity signals.
[0020] Furthermore, in step 3), the mass ratio of N,N-dimethylformamide to water in the washing solution is 1:5. The washing solution is used to wash away residual organic molecules on the surface of amorphous metal-organic framework microspheres to obtain high-quality microspheres.
[0021] This invention also provides applications of the aforementioned amorphous metal-organic framework microspheres, which can be used for anti-counterfeiting encoding and decoding, and can be used to design covert barcodes as anti-counterfeiting labels.
[0022] This invention employs the above technical solution to synthesize amorphous metal-organic framework microspheres in one step via a simple solvothermal method. The beneficial effects of this invention are as follows:
[0023] 1. This invention provides amorphous metal-organic framework microspheres with ideal circular boundaries and smooth surfaces. The microspheres exhibit a series of sharp characteristic peaks in their PL emission, displaying a typical whispering-gallery mode. The microspheres are size-dependent, with different sizes exhibiting different modal spacings, which facilitates the fabrication of photonic barcodes with high encoding capabilities. The microspheres possess tunable whispering-gallery modes.
[0024] 2. This invention provides a method for preparing amorphous metal-organic framework microspheres. The preparation method is simple and easy to operate. The microspheres synthesized in one step by solvothermal method have smooth surfaces and good stability, which is beneficial for achieving effective whispering-gallery modes at low excitation thresholds.
[0025] 3. This invention provides an application of amorphous metal-organic framework microspheres, whose switchable whispering-gallery mode allows for the design of concealed photonic barcodes as anti-counterfeiting labels, which is beneficial for improving coding capabilities and enhancing information security. Attached Figure Description
[0026] Figure 1 This is a flowchart of the method for preparing amorphous metal-organic framework microspheres according to the present invention.
[0027] Figure 2 The amorphous metal-organic framework microspheres prepared in Example 1 are shown in A, B, and C. A scanning electron microscope (SEM) image of the microspheres is shown in B, and a polarized light image of the microspheres is shown in C.
[0028] Figure 3 The microspheres are amorphous metal-organic framework microspheres prepared in Example 1. A is the PL spectrum of the microspheres, and the inset is a PL image of the microspheres. The size of the microspheres is 5 μm. B is the microspheres encoded using the PL spectrum.
[0029] Figure 4 The data for the 5μm microspheres prepared in Example 1 are shown in A, which are PL images and scanning electron microscope images of the 5μm microspheres; and B, which are PL spectra of the microspheres and their corresponding barcodes.
[0030] Figure 5 The data for the 8μm microspheres prepared in Example 2 are shown in Figure A, which is a PL image and a scanning electron microscope image of the 8μm microspheres; and Figure B, which is a PL spectrum of the microspheres and their corresponding barcodes.
[0031] Figure 6 Data for the 10 μm microspheres prepared in Example 3: A is the PL image and scanning electron microscope image of the 10 μm microspheres; B is the PL spectrum of the microspheres and their corresponding barcodes.
[0032] Figure 7 This is a graph showing the relationship between the microsphere size and the inter-mold spacing.
[0033] Figure 8 The data for the 3μm microspheres prepared in Example 4 are shown in A, which is a scanning electron microscope image of the 3μm microspheres, with four parts selected and numbered 1, 2, 3, and 4 respectively; and B, which is the PL spectrum of the microspheres measured in regions 1, 2, 3, and 4.
[0034] Figure 9In a preferred embodiment of the present invention, the microspheres are PL images in three states: raw, heated, and treated with organic solvents; PL spectra of the microspheres in the three states; and a barcode obtained from the PL spectra. Detailed Implementation
[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by this invention.
[0036] The amorphous metal-organic framework microspheres described in this invention can be used in anti-counterfeiting encoding and decoding. The encoding scheme is as follows: each barcode is located at a corresponding mode peak, and its width is determined by the intensity of the corresponding mode peak. Through the encoding scheme, a unique barcode corresponding to the microcavity signal can be generated. Each barcode and its corresponding microcavity signal are strictly one-to-one, which greatly improves the security of anti-counterfeiting information encryption.
[0037] Example 1
[0038] 1) Dissolve organic molecules H4TTBE and cadmium nitrate uniformly in N,N-dimethylformamide to obtain an organic solution. In the organic solution, the mass concentration of organic molecules H4TTBE is 1.2 mg / mL and the mass concentration of cadmium nitrate is 2 mg / mL.
[0039] Add water (water to organic solvent volume ratio of 1:5) to the above organic solution, sonicate for 5 min at a sonic frequency of 4 kHz to obtain a mixture.
[0040] 2) Pour the mixture into a 5mL glass bottle and then place it in an oven and heat at 85℃ for 18 hours;
[0041] 3) Remove and cool to room temperature. Wash the product three times with a washing solution of N,N-dimethylformamide and water in a mass ratio of 1:5 to obtain smooth amorphous metal-organic framework microspheres with a size of about 5 μm.
[0042] Figure 4 The data for the 5μm microspheres prepared in Example 1 are shown in A, which are PL images and scanning electron microscope images of the 5μm microspheres; and B, which are PL spectra of the microspheres and their corresponding barcodes.
[0043] Figure 4 The barcode encoding scheme is as follows: each barcode is located at the corresponding mode peak, and its width is determined by the intensity of the corresponding mode peak.
[0044] Example 2
[0045] 1) Dissolve organic molecules H4TTBE and cadmium nitrate uniformly in N,N-dimethylformamide to obtain an organic solution. In the organic solution, the mass concentration of organic molecules H4TTBE is 1.5 mg / mL and the mass concentration of cadmium nitrate is 2 mg / mL.
[0046] Add water (water to organic solvent volume ratio of 1:5) to the above organic solution, sonicate for 5 min at a sonic frequency of 4 kHz to obtain a mixture.
[0047] 2) Pour the mixture into a 5mL glass bottle and then place it in an oven and heat at 85℃ for 18 hours;
[0048] 3) Remove and cool to room temperature. Wash the product three times with a washing solution of N,N-dimethylformamide and water in a mass ratio of 1:5 to obtain smooth amorphous metal-organic framework microspheres with a size of about 8 μm.
[0049] Figure 5 The data for the 8μm microspheres prepared in Example 2 are shown in Figure A, which is a PL image and a scanning electron microscope image of the 8μm microspheres; and Figure B, which is a PL spectrum of the microspheres and their corresponding barcodes.
[0050] Figure 5 The barcode encoding scheme is as follows: each barcode is located at the corresponding mode peak, and its width is determined by the intensity of the corresponding mode peak.
[0051] Example 3
[0052] 1) Dissolve organic molecules H4TTBE and cadmium nitrate uniformly in N,N-dimethylformamide to obtain an organic solution. The organic solution contains organic molecules H4TTBE at a mass concentration of 2 mg / mL and cadmium nitrate at a mass concentration of 2 mg / mL.
[0053] Add water (water to organic solvent volume ratio of 1:5) to the above organic solution, sonicate for 5 min at a sonic frequency of 4 kHz to obtain a mixture.
[0054] 2) Pour the mixture into a 5mL glass bottle and then place it in an oven and heat at 85℃ for 18 hours;
[0055] 3) Remove and cool to room temperature. Wash the product three times with a washing solution of N,N-dimethylformamide and water in a mass ratio of 1:5 to obtain smooth amorphous metal-organic framework microspheres with a size of about 10 μm.
[0056] Figure 6 Data for the 10 μm microspheres prepared in Example 3: A is the PL image and scanning electron microscope image of the 10 μm microspheres; B is the PL spectrum of the microspheres and their corresponding barcodes.
[0057] Figure 6 The barcode encoding scheme is as follows: each barcode is located at the corresponding mode peak, and its width is determined by the intensity of the corresponding mode peak.
[0058] Figure 7 The graph shows the relationship between microsphere size and intermodal spacing. As the microsphere diameter increases from 5 μm and 8 μm to 10 μm, the intermodal spacing decreases from 9 nm and 7 nm to 5.5 nm. According to the whispering-gallery mode microcavity theory, the relationship between intermodal spacing (Δλ) and microsphere diameter (D) is given by λ... 2 / Δλ=nπD, where λ is the central emission wavelength and n is the refractive index. Figure 7 D and λ are given 2 The linear fitting result for the relationship between nπ and Δλ is nπ = 5.18, and the calculated refractive index n is 1.65.
[0059] Example 4
[0060] 1) Dissolve organic molecules H4TTBE and cadmium nitrate uniformly in N,N-dimethylformamide to obtain an organic solution. In the organic solution, the mass concentration of organic molecules H4TTBE is 1.2 mg / mL and the mass concentration of cadmium nitrate is 2 mg / mL.
[0061] Add water (water to organic solvent volume ratio of 1:5) to the above organic solution, sonicate for 5 min at a sonic frequency of 4 kHz to obtain a mixture.
[0062] 2) Pour the mixture into a 5mL glass bottle and then place it in an oven and heat at 85℃ for 18 hours;
[0063] 3) Remove and cool to room temperature. Wash the product three times with a washing solution of N,N-dimethylformamide and water in a mass ratio of 1:5 to obtain smooth amorphous metal-organic framework microspheres with a size of about 3 μm.
[0064] Figure 8 In the image, A is a scanning electron microscope (SEM) image of a 3 μm microsphere, with four sections selected and numbered 1, 2, 3, and 4 respectively; B is the photoluminescence (PL) spectrum of the microsphere measured in regions 1, 2, 3, and 4. The resonant modes of the four PL spectra are consistent, indicating that the microcavity signal is direction-independent, which is beneficial for barcode recognition.
[0065] Figure 9The data for the 3 μm microspheres prepared in Example 4 are shown from left to right: photonic resonance (PL) images of the microspheres in their original, heated, and organic solvent-treated states; PL spectra in each of the three states; and a barcode obtained from the PL spectra. After heating, the resonant modes in the original PL spectrum of the microspheres transformed into another set of mode peaks with the same position but different intensities. The resonant wavelength remained unchanged, indicating that there were no detectable changes in the size, mass, or other parameters of the microspheres during heating. Based on the encoding rules, a photonic barcode different from the original state can be obtained. Under organic solvent treatment, the microspheres returned to their original state, and the mode peaks and barcode also returned to their initial state.
[0066] Depend on Figure 9 It is known that the amorphous metal-organic framework microspheres realize switchable whispering-gallery mode microcavity signals, which can be used for anti-counterfeiting encoding and decoding.
[0067] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing amorphous metal-organic framework microspheres, characterized in that, Includes the following steps: 1) Dissolve organic molecules and cadmium nitrate uniformly in an organic solvent to obtain an organic solution; add water to the organic solution and sonicate to obtain a mixed solution; 2) Pour the mixture into a glass bottle and then place it in an oven to heat; 3) Remove and cool to room temperature, then wash the product with a washing solution made of organic solvent and water to obtain amorphous metal-organic framework microspheres; The organic molecule mentioned is 1,1,2,2-tetraphenyl[1,1'-biphenyl-4(1-H-tetrazole)ethylene](H4TTBE), with the following molecular structure:
2. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, The organic solvent is N,N-dimethylformamide.
3. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, In the organic solution, the mass concentration of the organic molecule H4TTBE is 1.2-2 mg / mL, and the mass concentration of cadmium nitrate is 2 mg / mL.
4. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, The amorphous metal-organic framework microspheres have a size of 3-15 μm.
5. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, In step 1), the volume ratio of water to organic solvent is 1:3 to 5.
6. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, In step 1), the ultrasound duration is 5 to 6 minutes, and the ultrasound frequency is 40 to 45 kHz.
7. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, In step 2), the heating temperature is 65-100℃ and the heating time is 12-24h.
8. The method for preparing amorphous metal-organic framework microspheres according to claim 1, characterized in that, In step 3), the mass ratio of N,N-dimethylformamide to water in the washing solution is 1:
5.
9. Amorphous metal-organic framework microspheres obtained by the preparation method according to any one of claims 1 to 8.
10. The application of the amorphous metal-organic framework microspheres as described in claim 9 in the field of anti-counterfeiting.