Solid-state fluorescent covalent organic framework material, preparation and application of solid-state fluorescent covalent organic framework material in antibiotic detection and fingerprint identification

Abstract

The invention relates to the technical field of fluorescent nano material application, in particular to a solid-state fluorescent covalent organic framework material, preparation and application of the solid-state fluorescent covalent organic framework material in antibiotic detection and fingerprint recognition. The solid-state fluorescent covalent organic framework material is prepared from the following raw materials: a polyamino aromatic compound, a pi-conjugated aromatic compound and a mixed solvent. Through the interaction between monomer structures, the interlayer spacing of COF-MA is expanded to 7.054, which significantly exceeds the 3-4 range of traditional COFs. Therefore, interlayer pi-pi accumulation is remarkably weakened, and COF-MA is promoted to emit solid-state red fluorescence. Long excitation wavelength and emission wavelength enable the COF-MA to have strong background interference resistance, so that sensitive antibiotic detection can be carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of applications of fluorescent nanomaterials, and in particular, to a solid-state fluorescent covalent organic framework material, its preparation, and its applications in antibiotic detection and fingerprint recognition. Background Art

[0002] Covalent organic frameworks (COFs) are a class of highly ordered, crystalline, porous materials formed by strong covalent bonds between building units. Generally, COFs exhibit a graphene-like periodic arrangement and a highly conjugated crystal structure. Therefore, they have a large specific surface area, high porosity, excellent stability, and considerable conductivity. The presence of various functional groups endows COFs with a high degree of customizability, making them widely applicable to various fields of application. Utilizing these properties, COFs have shown great potential in fields such as sensing, imaging, recognition, adsorption, energy storage, catalysis, and drug delivery. Among these applications, the fluorescence detection method based on COFs has received extensive attention due to its rapidity and sensitivity. Specifically, fluorescent COFs have multiple identical active sites extended through the framework system. When a binding event occurs at one of the sites, the signal is effectively transmitted and amplified through the entire framework, enabling highly sensitive detection.

[0003] Due to the tightly packed flat molecular layer arrangement of conventional COFs, strong π-π stacking interactions are prone to occur, which usually results in weak fluorescence or non-luminescence. Therefore, obtaining COFs with ideal fluorescence properties remains a major challenge. Currently, two main strategies have been developed to construct fluorescent COFs. The first strategy involves functionalization, including post-modification and material composite. For example, ionic groups can be incorporated into COFs through Williamson ether synthesis reactions, which not only expands the conjugated structure of COFs but also significantly enhances their fluorescence properties. Additionally, Eu 3+Functionalization can achieve ratiometric fluorescence sensing of COFs, thereby improving detection sensitivity and visualization detection performance. This method usually uses easily synthesized weakly fluorescent COFs as precursors and modifies their structures and functions by introducing various groups. However, the post-modification process may change the crystal structure of COFs or lead to an amorphous state. These effects seriously damage the physical and chemical properties of COFs and limit their application potential. The second strategy focuses on structural tuning. For example, promoting the rigidification of the spatial structure through the steric effect of the framework can improve the fluorescence emission efficiency of COFs. In addition, integrating highly flexible non-planar flexible building units helps increase the layer spacing and weaken π-π interactions, thereby reducing fluorescence self-quenching induced by COF aggregation. Different from the functionalization strategy, the structural tuning strategy synthesizes highly crystalline COFs in one step through reasonable structural design and integration. This process avoids material loss and crystal damage that may be caused by functionalization, simplifies the operation and reduces the cost, and is considered a productive method.

[0004] Traditional COFs have a closely packed flat molecular layer arrangement, so they are prone to strong π-π stacking interactions, which usually result in weak fluorescence or non-luminescence, causing functional singleness. The existing post-functionalization methods for improving the fluorescence properties of COFs are not only complex and costly in operation, but may also change the crystal structure of COFs, leading to an amorphous state, which seriously affects the physical and chemical properties of COFs and is not conducive to exploring their further applications.

[0005] The vast majority of fluorescent COF probes exhibit blue, green, and yellow fluorescence, with short excitation and emission wavelengths. This wavelength band may overlap with some fluorescent impurities and is easily interfered with, which is not conducive to fluorescence detection. Traditional liquid fluorescent probes have limitations in solid-state applications. Summary of the Invention

[0006] The present invention provides a solid-state fluorescent covalent organic framework material, and its preparation raw materials include: polyamino aromatic compounds, π-conjugated aromatic compounds, and mixed solvents.

[0007] As an embodiment of the present invention, the polyamino aromatic compound is selected from one or more of 4,4’,4’’-triaminotriphenylmethane, 4,4’,4’’-triaminotriphenylmethane ether, 4,4’,4’’-triaminotriphenylbenzene, tris(4-aminophenyl)amine, tris(4-aminophenyl)triazine, and tris(4-aminophenyl)pyrazine.

[0008] As an embodiment of the present invention, the polyamino aromatic compound is 4,4’,4’’-triaminotriphenylmethane.

[0009] As an embodiment of the present invention, the π-conjugated aromatic compound is selected from 2,6-dialdehyde-1,5-dihydroxynaphthalene, 2,6-dialdehyde naphthalene, 1,5-dialdehyde-2,6-dihydroxynaphthalene, 2,5-dialdehyde hydroquinone, 2,6-dialdehyde fluorene, 2,7-dialdehyde pyrene, 2,6-dialdehyde perylene.

[0010] As an embodiment of the present invention, the π-conjugated aromatic compound is 2,6-dialdehyde-1,5-dihydroxynaphthalene.

[0011] As an embodiment of the present invention, the mixed solvent is one of a mixed solvent of mesitylene / 1,4-dioxane, a mixed solvent of dimethyl sulfoxide / ethanol, a mixed solvent of mesitylene / N,N-dimethylformamide, a mixed solvent of mesitylene / acetonitrile, and a mixed solvent of N,N-dimethylformamide / 1,4-dioxane.

[0012] As an embodiment of the present invention, a method for preparing the solid-state fluorescent covalent organic framework material includes the following steps: Mix a polyamino aromatic compound and a π-conjugated aromatic compound in a mixed solvent; after ultrasonic treatment, slowly add glacial acetic acid and continue ultrasonic treatment; then place it at room temperature to complete the reaction, wash the red precipitate with tetrahydrofuran, and collect the product by centrifugation; finally, dry it to obtain the product.

[0013] As an embodiment of the present invention, the ratio of the polyamino aromatic compound, the π-conjugated aromatic compound, and the mixed solvent is: polyamino aromatic compound 17.42 mg: 19.46 mg: (6 - 14) mL.

[0014] On the other hand, the present invention provides the application of the solid-state fluorescent covalent organic framework material in the field of antibiotic detection.

[0015] On the other hand, the present invention provides the application of the solid-state fluorescent covalent organic framework material in the field of fingerprint recognition.

[0016] Adopting the above technical solution, the present invention has the following beneficial effects: Based on the structural tuning strategy, a flexible-rigid alternating assembled COF (COF-MA) linked by imine was developed by integrating flexible and rigid building blocks. Among them, the flexible monomer exhibits highly free rotation, while the rigid monomer is solidified by intramolecular hydrogen bonding through the naphthalene ring. Through the interaction between monomer structures, the layer spacing of COF-MA expands to 7.054 Å, significantly exceeding the 3-4 Å range of traditional COFs. This significantly weakens the interlayer π-π stacking and promotes COF-MA to emit solid-state red fluorescence. The longer excitation and emission wavelengths endow COF-MA with strong anti-background interference ability, enabling sensitive antibiotic detection. In addition, as a solid-state phosphor with unique colors under sunlight and UV light, COF-MA can be used as a good fingerprint developer to identify potential fingerprints under sunlight and further reveal complex fingerprint details under UV light, effectively excluding the interference of stains on the substrate surface. So far, most of the reported red fluorescent COFs are prepared by complex functionalization modifications, and there are few reports on the one-step synthesis of spontaneous red fluorescent COFs. Notably, the one-step synthesis method of solid-state red fluorescent COF achieved through the structural tuning strategy in this study provides an innovative and effective method for the preparation and optimization of fluorescent COFs. This strategy compensates for the limitations of traditional liquid fluorescent materials in solid-state applications and broadens the practical application scope of fluorescent COFs. Description of the Drawings

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 Schematic diagram of the preparation process and application of COF-MA Figure 2 PXRD spectra of COF-MA under different conditions: A. Solvent composition; B. Solvent volume; C. Catalyst dosage; D. Reaction time Figure 3 A. FT-IR spectra of TAPM, DHNDA and COF-MA; B-E. XPS spectra of COF-MA and its C 1s region, N 1s region and O 1s region; F-G. SEM and TEM images of COF-MA; H. TGA curve of COF-MA; I. Water contact angle of COF-MA.

[0019] Figure 4A-B. Fluorescence spectra and intensities of COF-MA placed for different times; C-D. Fluorescence spectra and intensities of COF-MA in different ionic solutions; E-F. Fluorescence spectra and intensities of COF-MA in high-concentration salt solutions; G-H. Fluorescence spectra and intensities of COF-MA at different pH values.

[0020] Figure 5 A. Schematic diagrams of the structures of RFP, RPT, structural analogs, and functional analogs; C-D. Fluorescence detection selectivity of COF-MA.

[0021] Figure 6 A. Fluorescence spectra of COF-MA at different concentrations of RFP; B-C. Linear relationship between COF-MA and RFP; D. Fluorescence spectra of COF-MA at different concentrations of RPT; E-F. Linear relationship between COF-MA and RPT.

[0022] Figure 7 A-E. Fluorescence spectra of COF-MA for detecting RFP under interference of different concentrations of structural analogs; F-J. Fluorescence spectra of COF-MA for detecting RPT under interference of different concentrations of structural analogs; K-L. Effects of structural analogs on the detection of RFP and RPT by COF-MA.

[0023] Figure 8 A. Fluorescence reusability of COF-MA; B-C. Detection efficiencies of reused COF-MA for RFP and RPT.

[0024] Figure 9 Potential fingerprint daylight images obtained by COF-MA on 8 substrates.

[0025] Figure 10 A-H. Resolution analysis of the upper right yellow line area of potential fingerprint UV images on 8 substrates obtained by COF-MA.

[0026] Figure 11 G value of the upper right yellow line area R / G F value comparison.

[0027] Figure 12 Detailed potential fingerprint identification of COF-MA on plastics. Specific implementation manners

[0028] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0029] The reagents used are as follows: 4,4’,4’’-Triaminotriphenylmethane (TAPM, purity > 97%), 2,6-diformyl-1,5-dihydroxynaphthalene (DHNDA, purity > 97%), mesitylene, 1,4-dioxane, glacial acetic acid, tetrahydrofuran.

[0030] Table 1 Specific preparation raw materials for Examples 1 - 4

[0031] Among them, the preparation methods for Examples 1 - 4 are as follows: Mix TAPM 4,4’,4’’-Triaminotriphenylmethane (17.42 mg, 0.06 mmol) and DHNDA 2,6-diformyl-1,5-dihydroxynaphthalene (19.46 mg, 0.09 mmol) in 14 mL of a mesitylene / 1,4-dioxane mixed solvent with different volume ratios. After ultrasonic treatment for 10 min, slowly add 0.3 mL of HAc (6 M), and continue ultrasonic treatment for 5 min. React at room temperature for 48 h. Subsequently, wash the red precipitate with THF 3 times, and collect the product by centrifugation (7800 rpm, 5 min). Finally, dry under vacuum at 60 ºC for 12 h to obtain a red powder, namely COF-MA.

[0032] Perform PXRD spectral tests on the COF-MA obtained from Examples 1 - 4. Figure 2 Reacting in a mesitylene / 1,4-dioxane mixed solution (2:3, v / v) can obtain COF-MA with high crystallinity.

[0033] Table 2 Specific preparation raw materials for Examples 5 - 9

[0034] Among them, the preparation methods for Examples 5 - 9 are as follows: Mix TAPM 4,4’,4’’-triaminotriphenylmethane (17.42 mg, 0.06 mmol) and DHNDA 2,6-dialdehyde-1,5-dihydroxynaphthalene (19.46 mg, 0.09 mmol) in different volumes of mesitylene / 1,4-dioxane mixed solvent (2:3, v / v). After sonication for 10 min, slowly add 0.3 mL of HAc (6 M), and continue sonication for 5 min. React at room temperature for 48 h. Subsequently, wash the red precipitate with THF three times and collect the product by centrifugation (7800 rpm, 5 min). Finally, dry it under vacuum at 60 ºC for 12 h to obtain a red powder, namely COF-MA.

[0035] Perform PXRD spectral tests on the COF-MA obtained in Example 1 and Examples 5 - 9. As Figure 2 shown in B, reacting in 14 mL of mesitylene / 1,4-dioxane mixed solution (2:3, v / v) can obtain COF-MA with high crystallinity.

[0036] Table 3 Specific preparation raw materials for Examples 10 - 14

[0037] Among them, the preparation methods for Examples 10 - 14 are as follows: Mix TAPM 4,4’,4’’-triaminotriphenylmethane (17.42 mg, 0.06 mmol) and DHNDA 2,6-dialdehyde-1,5-dihydroxynaphthalene (19.46 mg, 0.09 mmol) in 14 mL of mesitylene / 1,4-dioxane mixed solvent with different volume ratios (2:3, v / v). After sonication for 10 min, slowly add different volumes of HAc (6 M), and continue sonication for 5 min. React at room temperature for 48 h. Subsequently, wash the red precipitate with THF three times and collect the product by centrifugation (7800 rpm, 5 min). Finally, dry it under vacuum at 60 ºC for 12 h to obtain a red powder, namely COF-MA.

[0038] Perform PXRD spectral tests on the COF-MA obtained in Example 1 and Examples 10 - 14. As Figure 2 shown in C, COF-MA with high crystallinity can be obtained under the catalyst of 0.3 mL HAc.

[0039] Table 4 Specific preparation raw materials for Examples 15 - 17

[0040] Among them, the preparation methods of Examples 15 to 17 are as follows: Mix TAPM 4,4’,4’’-triaminotriphenylmethane (17.42 mg, 0.06 mmol) and DHNDA 2,6-dialdehyde-1,5-dihydroxynaphthalene (19.46 mg, 0.09 mmol) in 14 mL of a mesitylene / 1,4-dioxane mixed solvent (2:3, v / v). After ultrasonic treatment for 10 min, slowly add 0.3 mL of HAc (6 M), and continue ultrasonic treatment for 5 min. React at room temperature for different times. Subsequently, wash the red precipitate with THF three times, and collect the product by centrifugation (7800 rpm, 5 min). Finally, dry it under vacuum at 60 ºC for 12 h to obtain a red powder, namely COF-MA.

[0041] Perform PXRD spectral tests on the COF-MA obtained in Example 1 and Examples 15 to 17. It can be seen from Figure 2 D that COF-MA with high crystallinity can be obtained under a reaction time of 48 h.

[0042] Generally, the condensation reaction of COFs is reversible. During this process, the chemical bonds between monomers are constantly formed and broken, promoting the "self-healing" of the main chain of COFs, which is an important process for the formation of COFs crystals. Since the synthesis of COFs is thermodynamically controlled, too fast or too slow reaction rates will disrupt the structural arrangement, resulting in a decrease in crystallinity and even the formation of a completely amorphous structure. Therefore, it is crucial to determine appropriate reaction conditions. In this study, based on the PXRD characterization results, the synthesis conditions of COF-MA were systematically optimized. Figure 2 A-2C shows that COF-MA with high crystallinity can be obtained by reacting in 14 mL of a mesitylene / 1,4-dioxane mixed solution (2:3, v / v) and 0.3 mL of HAc. In addition, considering the factors of crystal form stability and yield comprehensively, Figure 2 D determines 48 h as the optimal reaction time.

[0043] Characterize the solid-state fluorescent COF material prepared in Example 1.

[0044] Infrared analysis (FT-IR) Infrared spectroscopy shows ( Figure 3 A) that the N-H stretching vibration peak of TAPM at 3454 - 3020 cm -1 and the C=O stretching vibration peak of DHNDA at 1641 cm -1 disappear, while the characteristic C=N stretching peak of COF-MA is at 1616 cm -1appeared. These results indicate that a Schiff base reaction occurred between TAPM and DHNDA, generating imine bonds and successfully synthesizing COF-MA.

[0045] Elemental analysis (XPS) The XPS spectrum of COF-Bpy ( Figure 3 B) shows the presence of elements C (83.29%), N (7.59%), and O (9.12%), which is consistent with the theoretical structural element ratios. Among them, in the C 1s region ( Figure 3 C), peaks corresponding to C=C / C-C, C=N / C-N, and C-O bonds are shown at 284.60 eV, 285.44 eV, and 286.40 eV, respectively. In the N 1s region ( Figure 3 D), peaks corresponding to N=C and N-C bonds appear at 399.05 eV and 400.20 eV, respectively. In addition, the O 1s region ( Figure 3 E) shows peaks corresponding to O-C and O-H bonds at 533.00 eV and 532.30 eV. These results together confirm the formation of imine bonds, indicating the successful synthesis of COF-MA.

[0046] Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis As Figure 3 shown in F-3G, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure and surface morphology of COF-Bpy. The SEM and TEM images show that COF-MA exhibits a microstructure with a beaded spherical arrangement and obvious lattice fringes.

[0047] Thermogravimetric analysis (TGA) As Figure 3 shown in H, thermogravimetric analysis (TGA) was used to evaluate the thermal stability of COF-MA. Due to the evaporation of residual solvents and moisture, the weight loss is about 5.7% at 400 ºC, and then due to the decomposition of the carbon skeleton, the weight further decreases by about 35.77% at 800 ºC, indicating that COF-MA has good thermal stability.

[0048] Water contact angle analysis The hydrophilicity / hydrophobicity of COF-MA was studied using an AFES contact angle meter. As Figure 3 shown in I, the measured water contact angle of COF-MA decreased from 72.90 º to 36.38 º within 10 s, and this rapid change shows the hydrophilicity of COF-MA and its applicability to water system applications.

[0049] The fluorescence stability of the solid-state fluorescent COF material prepared in Example 1 was studied.

[0050] To explore the potential of COF-MA for detecting antibiotics in complex samples, the fluorescence stability of COF-MA was first evaluated. COF-MA was dispersed in ethanol to obtain a COF-MA ethanol dispersion of 30 μg·mL -1 . The COF-MA was allowed to stand for a long time, and the fluorescence intensity was measured at an excitation wavelength (λex) of 490 nm every hour to determine the time stability of COF-MA.

[0051] To evaluate the anti-ion interference of COF-MA, 300 μL of different ion solutions (Li + , Na + , K + , Fe 2+ , Ba 2+ , Mg 2+ , Ca 2+ , Ni 2+ , Cu 2+ , Pb 2+ , Cd 2+ , Hg 2+ , Fe 3+ , Al 3+ , Co 3+ , F - , Cl - , NO3 - , CH3COO - , and SO4 2- , 1 mM) were added to 2700 μL of COF-MA. After mixing evenly, the fluorescence intensity was measured at λex = 490 nm. Subsequently, 300 μL of high-concentration salt solutions (10 - 200 mM) were added to 2700 μL of COF-MA, and the fluorescence intensity at λex = 490 nm was measured after thorough mixing.

[0052] To further demonstrate the pH stability of COF-MA, 90 μL of COF-MA (1000 μg·mL -1 ) was added to 2910 μL of different pH solutions, and then the fluorescence intensity was measured at λex = 490 nm.

[0053] Figure 4The A-4H display shows that the fluorescence of COF-MA exhibits minor fluctuations within 7 h and remains stable in 20 ionic solutions, even at a high salt concentration of 200 mM. In addition, COF-MA also shows fluorescence stability in a wide pH range of 2 - 12, indicating the anti-interference and durability of COF-MA under various environmental conditions.

[0054] Perform fluorescence detection performance analysis on the solid-state fluorescent COF material prepared in Example 1.

[0055] To study the selectivity and sensitivity of COF-MA for detecting rifampicin (RFP) and rifapentine (RPT), other drugs were used as competitive substances, including structural analogs (such as RBT, etc.) and functional analogs (such as INH, etc.). COF-MA was dispersed in ethanol to obtain a COF-MA ethanol dispersion of 50 μg·mL -1 . 200 μg·mL -1 of each drug analyte was added to 2700 μL of COF-MA. After thorough mixing, the fluorescence intensity was measured at λex = 490 nm to analyze the detection selectivity of COF-MA.

[0056] Then, 300 μL of RFP or RPT with a concentration of 0 - 1000 μg·mL -1 was added to 2700 μL of COF-MA. After mixing evenly, the fluorescence intensity was measured at λex = 490 nm to analyze the detection sensitivity of COF-MA to RFP or RPT. Subsequently, the fluorescence intensity of COF-MA for detecting RFP or RPT was measured in the coexistence of different concentrations of structural analogs to explore the anti-interference ability of COF-MA. A mixture of 300 μL of RFP or RPT and a structural analog (1:1 equivalent) was added to 2700 μL of COF-MA, and then the fluorescence intensity at λex = 490 nm was measured.

[0057] To clarify the reusability of COF-MA in the detection of RFP or RPT, 300 μL of RFP or RPT (200 μg·mL -1 ) was added to 2700 μL of the COF-MA ethanol dispersion (50 μg·mL -1 ). The fluorescence intensity before and after adding RFP or RPT was measured at λex = 490 nm. The remaining COF-MA was dried and then ethanol was added again until the concentration returned to 50 μg·mL -1, and the fluorescence intensities before and after adding RFP or RPT were measured at λex = 490 nm. This was recorded as one cycle period. This cycle was repeated 8 times to demonstrate the fluorescence reusability of COF-MA.

[0058] The selectivity of COF-MA for antibiotic detection was investigated. Rifamycin antibiotics were used as the target analytes, and their structural and functional analogues were used as competitive analytes, with the structure shown as Figure 5 shown in A. Figure 5 Figures C-5D show that RFP and RPT significantly quenched the fluorescence of COF-MA, while the effects of other competitive analytes were almost negligible, highlighting the good fluorescence detection selectivity of COF-MA for RFP and RPT. In addition, Figure 6 Figure A-6F shows that the fluorescence intensity of COF-MA decreased with increasing concentrations of RFP or RPT. It showed a linear relationship with RFP in the concentration range of 0 - 100 μg·mL -1 and with RPT in the concentration range of 0 - 60 μg·mL -1 , with R 2 > 0.9948, and the LODs were as low as 6.7 ng·mL -1 . These results demonstrated the excellent sensitivity of COF-MA in detecting RFP or RPT, capable of accurately quantifying low concentrations of target antibiotics through fluorescence analysis. Given the structural similarity between RFP, RPT and their analogues, the fluorescence intensity of COF-MA was further evaluated in the case of a 1:1 equivalent mixture of the structural analogue with RFP or RPT to investigate its anti-interference ability. Figure 7 Figure A-7L shows that the antibiotic mixture did not change the overall fluorescence spectral shape of COF-MA, but RBT, RXM and RFSV at higher concentrations (up to 40 μg·mL -1 ) significantly interfered with the detection of RFP. Similarly, RFSV also significantly affected the detection of RPT at this concentration. Despite these effects at higher concentrations, COF-MA showed good anti-interference performance towards structural analogues at low to moderate interference concentrations. In addition, fluorescence reusability is an important parameter for evaluating the durability and service life of COF-MA. Figure 8 Figure A shows that after 8 cycle periods, the fluorescence intensity of COF-MA fluctuated within an acceptable range Figure 8 Figure B-8C shows that the detection efficiency of COF-MA for RFP or RPT decreased with increasing number of cycles and stabilized at about 70% after 8 cycles, reflecting the stable fluorescence characteristics and reusability of COF-MA.

[0059] The potential fingerprint recognition performance of the solid-state fluorescent COF material prepared in Example 1 was analyzed.

[0060] Given the solid-state fluorescence properties of COF-MA powder, its application potential for identifying latent fingerprints was systematically evaluated. Volunteers were asked to wash their hands and gently touch their foreheads with their fingers. Then, the fingertips were pressed on the surfaces of different substrates, including plastic, tin foil, stainless steel, paper, glass, rubber, wood, and leather. An appropriate amount of COF-MA powder was swept over the latent fingerprints, and the excess powder was gently blown away with an ear bulb. Latent fingerprint images were recorded using an iPhone 11 Pro Max under UV light at 365 nm. Grayscale analysis was performed using ImageJ software.

[0061] Figure 9 It was shown that latent fingerprints on 8 substrates, including plastic, tin foil, stainless steel, paper, glass, rubber, wood, and leather, were successfully visualized using COF-MA, and the orange-red fingerprints were clearly visible under daylight. The grayscale of the upper right yellow line region of the fluorescence image of each substrate was analyzed using ImageJ software. To evaluate the image resolution, the ratio of the grayscale to the lowest grayscale (G / G0) was used as a parameter. Figure 10 A-10H showed that as the roughness of the substrate increased, the fingerprint resolution and contrast decreased, and COF-MA exhibited the best visualization performance on plastic (G / G0 up to 25) and tin foil (G / G0 up to 22). In addition, Figure 11 It was shown that by analyzing the ratio of the average grayscale of fingerprint ridges to grooves (G R / G F ) on all substrates, it was found that plastic and tin foil had the highest G R / G F values, up to 13. Although the fingerprint images on rough substrates such as rubber, wood, and leather showed uneven resolution, they still had G R / G F values of about 3. To further verify the effect of COF-MA, it was used to analyze 2 different fingerprints on plastic. Figure 12 It showed the detailed features of the fingerprints, such as cores, bifurcations, endings, lakes, isolated ridges, islands, spurs, and scars, which could be clearly identified by COF-MA. These results highlight the versatility of COF-MA in identifying latent fingerprints in complex environments, emphasizing the successful development of a rapid, convenient, and efficient latent fingerprint identification method based on COF-MA.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid-state fluorescent covalent organic framework material, characterized in that, Its preparation raw materials include: polyamino aromatic compounds, π-conjugated aromatic compounds, and a mixed solvent.

2. The solid-state fluorescent covalent organic framework material according to claim 1, wherein The polyamino aromatic compound is selected from one or more of 4,4',4''-triaminotriphenylmethane, 4,4',4''-triaminotriphenylmethane ether, 4,4',4''-triaminotriphenylbenzene, tris(4-aminophenyl)amine, tris(4-aminophenyl)triazine, and tris(4-aminophenyl)pyrazine.

3. The solid-state fluorescent covalent organic framework material according to claim 2, wherein The polyamino aromatic compound is 4,4',4''-triaminotriphenylmethane.

4. A solid-state fluorescent covalent organic framework material according to claim 1, characterized in that, The π-conjugated aromatic compound is selected from 2,6-dialdehyde-1,5-dihydroxynaphthalene, 2,6-dialdehyde naphthalene, 1,5-dialdehyde-2,6-dihydroxynaphthalene, 2,5-dialdehyde hydroquinone, 2,6-dialdehyde fluorene, 2,7-dialdehyde pyrene, and 2,6-dialdehyde perylene.

5. The solid-state fluorescent covalent organic framework material according to claim 4, characterized in that, The π-conjugated aromatic compound is 2,6-dialdehyde-1,5-dihydroxynaphthalene.

6. A solid-state fluorescent covalent organic framework material according to any one of claims 1 to 4, characterized in that, The mixed solvent is one of the mixed solvents of mesitylene / 1,4-dioxane, dimethyl sulfoxide / ethanol, mesitylene / N,N-dimethylformamide, mesitylene / acetonitrile, and N,N-dimethylformamide / 1,4-dioxane.

7. A method for preparing a solid-state fluorescent covalent organic framework material according to any one of claims 1 to 6, characterized in that, It includes the following steps: Mix the polyamino aromatic compound and the π-conjugated aromatic compound in the mixed solvent; after ultrasonic treatment, slowly add glacial acetic acid and continue ultrasonic treatment; then place it at room temperature to complete the reaction. Wash the red precipitate with tetrahydrofuran and collect the product by centrifugation; finally, dry it to obtain.

8. The preparation method of a solid-state fluorescent covalent organic framework material according to claim 7, wherein The ratio of the polyamino aromatic compound, the π-conjugated aromatic compound, and the mixed solvent is: polyamino aromatic compound 0.06 mmol: 0.09 mmol: (6~14) mL.

9. A solid-state fluorescent covalent organic framework material according to any one of claims 1 to 6, wherein It is applied to the field of antibiotic detection.

10. A solid-state fluorescent covalent organic framework material according to any one of claims 1 to 6, characterized in that, It is applied to the field of fingerprint recognition.

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