Ratiometric sensor based on uiO-66-nh2@tpTt-COF composites and preparation method thereof

Abstract

This invention relates to a ratiometric sensor based on UiO-66-NH2@TT-COF composite material and its preparation method. The ratiometric sensor based on UiO-66-NH2@TpTt-COF composite material is synthesized by using an interface growth method to coat a TpTt-COF shell onto the surface of UiO-66-NH2, resulting in a UiO-66-NH2@TpTt-COF composite material with dual emission properties. A ratiometric fluorescence sensor can then be constructed using this UiO-66-NH2@TpTt-COF composite material. This invention uses an interface growth method to coat a TpTt-COF shell onto the surface of UiO-66-NH2, thereby synthesizing a UiO-66-NH2@TpTt-COF composite material with dual emission properties, thus constructing a novel ratiometric fluorescence sensor. When used to detect tetracycline, it achieves high selectivity and high sensitivity, thus providing a novel synchronous response sensor for antibiotic detection and offering a new possibility for the use of core-shell MOF@COF composite materials in the field of food safety.

Description

Technical Field

[0001] This invention relates to a fluorescence sensor, specifically a ratio sensor based on UiO-66-NH2@TpTt-COF composite material and its preparation method. Background Technology

[0002] Tetracycline (TET) is a broad-spectrum antibiotic commonly used to treat a variety of diseases in humans and animals. However, due to the limited metabolism of TET in organisms, most ingested TET is excreted and re-enters the environment, and it is difficult to degrade naturally, leading to its continuous accumulation in the environment. Studies have shown that TET residues detected in drinking water and milk are typically in the range of μg / kg. -1 The magnitude of TET is significant. Residual TET can move up the food chain, accumulating in the human body and causing allergic reactions and liver toxicity, as well as increasing bacterial resistance to antibiotics. This not only seriously threatens human health but may also disrupt the balance of the ecosystem.

[0003] Currently, the most common method for detecting TET residues in samples such as water and milk is instrumental analysis such as high-performance liquid chromatography (HPLC). This method has good sensitivity and low detection limits; however, its high cost and long detection time make it difficult to achieve real-time sample detection in everyday situations. Fluorescence detection, as an emerging and sensitive detection method, can achieve low-cost and highly sensitive detection of tetracycline. Therefore, developing a fluorescence sensor capable of specifically detecting tetracycline is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a ratio sensor based on UiO-66-NH2@TpTt-COF composite material to meet the need for sensitive, reliable and specific detection of tetracycline.

[0005] The objective of this invention is achieved as follows:

[0006] A ratiometric sensor based on UiO-66-NH2@TpTt-COF composite material is synthesized by using an interface growth method to attach a TpTt-COF shell to the surface of UiO-66-NH2, resulting in a UiO-66-NH2@TpTt-COF composite material with dual emission properties. A ratiometric fluorescence sensor can be constructed using this UiO-66-NH2@TpTt-COF composite material.

[0007] The objective of this invention can also be achieved in the following ways:

[0008] A ratio sensor based on UiO-66-NH2@TpTt-COF composite material was fabricated by the following method:

[0009] First, weigh 0.18 g of ZrCl4 according to the formula, dissolve it in 40 mL of N,N-dimethylformamide, and sonicate for 15 min until completely dissolved. Then, add 0.14 g of 2-aminoterephthalic acid, continue sonicating for 15 min, and add 5 mL of glacial acetic acid. Transfer the above mixed solution to a 100 mL polytetrafluoroethylene reactor liner, heat to 120 °C, keep warm for 24 h, and cool to 26 °C. Wash three times each with N,N-dimethylformamide and methanol, centrifuge at 8000 r / min to collect the particles, and vacuum dry at 70 °C for 12 h to obtain UiO-66-NH2.

[0010] Then, according to the ratio, 30 mg of UiO-66-NH2 and 15 mg of ligand Tp were added to a thick-walled glass tube containing a mixture of 2 ml N,N-dimethylacetamide and 1 ml dimethyl sulfoxide. After sonication for 15 min, 0.1 mL of acetic acid (6 M) was added, and the mixture was heated to 80 °C and kept at that temperature for 24 h. The precipitate was centrifuged at 8000 r / min for 5 min, and then washed three times each with N,N-dimethylacetamide and acetone. The precipitate was then vacuum dried at 80 °C for 12 h to obtain UiO-66-NH2(-CHO).

[0011] Then, according to the specified ratio, 30 mg of UiO-66-NH2(-CHO), 10 mg of ligand Tp, and 5 mg of ligand Tt were added to a thick-walled glass tube, followed by 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide. After sonication for 15 min, 0.1 mL of acetic acid (6M) was added. The thick-walled glass tube was then degassed by three freeze-pump-thaw cycles. After sealing, it was heated to 120℃ and kept at that temperature for 72 h. The resulting precipitate was centrifuged at 8000 r / min for 5 min, and then washed once each with N,N-dimethylacetamide and acetone. After vacuum drying at 80℃ for 12 h, the UiO-66-NH2@TpTt-COF composite material was obtained.

[0012] Finally, 10 mg of UiO-66-NH2@TpTt-COF composite material was weighed according to the formula and dissolved in 50 mL of ultrapure water. The solution was ultrasonically treated for 15 min until completely dissolved, thus obtaining a 0.2 mg / mL UiO-66-NH2@TpTt-COF ratio sensor solution.

[0013] The objective of this invention can also be achieved in the following ways:

[0014] A method for fabricating a ratio sensor based on UiO-66-NH2@TpTt-COF composite material includes the following steps:

[0015] Preparation of S1 and UiO-66-NH2: Weigh 0.18g of ZrCl4 according to the formula, dissolve it in 40mL of N,N-dimethylformamide, sonicate for 15min until completely dissolved, then add 0.14g of 2-aminoterephthalic acid, continue sonication for 15min, then add 5mL of glacial acetic acid, transfer the above mixed solution to a 100mL polytetrafluoroethylene reactor liner, heat to 120℃, keep warm for 24h, cool to 26℃, wash three times each with N,N-dimethylformamide and methanol, centrifuge at 8000r / min to collect particles, and vacuum dry at 70℃ for 12h to obtain UiO-66-NH2;

[0016] Synthesis of S2 and UiO-66-NH2(-CHO): 30 mg of UiO-66-NH2 and 15 mg of ligand Tp were added to a thick-walled glass tube containing a mixture of 2 ml N,N-dimethylacetamide and 1 ml dimethyl sulfoxide according to the specified ratio. After sonication for 15 min, 0.1 mL of acetic acid (6 M) was added, and the mixture was heated to 80 °C and kept at that temperature for 24 h. The precipitate was centrifuged at 8000 r / min for 5 min, and then washed three times each with N,N-dimethylacetamide and acetone. The precipitate was then vacuum dried at 80 °C for 12 h to obtain UiO-66-NH2(-CHO).

[0017] Synthesis of S3, UiO-66-NH2@TpTt-COF composite material: 30 mg of UiO-66-NH2(-CHO), 10 mg of ligand Tp and 5 mg of ligand Tt were added to a thick-walled glass tube according to the specified ratio. Then, 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide were added. After sonication for 15 min, 0.1 mL of acetic acid (6M) was added. The thick-walled glass tube was then degassed by three freeze-pump-thaw cycles. After sealing, it was heated to 120℃ and kept at that temperature for 72 h. The precipitate was centrifuged at 8000 r / min for 5 min and then washed once each with N,N-dimethylacetamide and acetone. After vacuum drying at 80℃ for 12 h, the UiO-66-NH2@TpTt-COF composite material was obtained.

[0018] S4. Preparation of UiO-66-NH2@TpTt-COF ratio sensor: Weigh 10 mg of UiO-66-NH2@TpTt-COF composite material according to the ratio and dissolve it in 50 mL of ultrapure water. Sonicate for 15 min until completely dissolved to obtain a 0.2 mg / mL UiO-66-NH2@TpTt-COF ratio sensor solution.

[0019] Fluorescent sensors exhibit a single response to a single recognition site of the target analyte, which can be susceptible to interference from the target analyte and analogues in complex matrices, severely limiting their selectivity and anti-interference capabilities. The natural π-conjugated system makes covalent organic frameworks (COFs) excellent dual-emission fluorescent materials (covalent-organic frameworks as proton conductors). However, due to intramolecular rotation, COFs tend to exhibit nonradiative relaxation, and their layered stacking structure can induce aggregation quenching (ACQ), thus affecting fluorescence emission. When the ACQ effect is suppressed, COFs with a π-conjugated triazine structure can undergo their own electron and proton transfer, producing fluorescence emission. Therefore, COFs with a π-conjugated triazine structure can serve as ratiometric fluorescence sensors for target analyte detection.

[0020] UiO-66-NH2 is a commonly used precursor material that can be complexed with TpTt-COF via an aldehyde-amine condensation reaction. The complexation of UiO-66-NH2, which exhibits strong fluorescence emission, with TpTt-COF not only increases the interlayer spacing but also restricts the rotation within the COF molecule and suppresses the ACQ effect, thus enhancing the dual fluorescence emission of TpTt-COF. The combined effect of UiO-66-NH2 and TpTt-COF, which has a π-conjugated structure, provides more affinity sites, improving the sensitivity and specificity of the sensor in detecting benzene ring target analytes. Due to the presence of an aromatic ring structure in the TET structure, π-π superposition can be used for the specific recognition of tetracyclines. Furthermore, TET is rich in hydroxyl and amino groups, which can form intermolecular hydrogen bonds with the triazine structure in TpTt-COF, causing a synchronous response in the sensing signal. The added UiO-66-NH2 not only enhances the dual emission signal of the fluorescence sensor, but also provides a π-conjugated structure and affinity site, enabling it to specifically respond to the selective detection of TET.

[0021] In this invention, the UiO-66-NH2@TpTt-COF composite material synthesized via the interface growth method described above is referred to as UiO-66-NH2@TpTt-COF. Correspondingly, the ratio sensor constructed based on the UiO-66-NH2@TpTt-COF composite material is referred to as a UiO-66-NH2@TpTt-COF ratio sensor or a UiO-66-NH2@TpTt-COF sensor.

[0022] This invention utilizes an interface growth method to coat a TpTt-COF shell onto the surface of UiO-66-NH2, thereby synthesizing a UiO-66-NH2@TpTt-COF composite material with dual emission properties, constructing a novel ratiometric fluorescent sensor. This sensor exhibits high selectivity and sensitivity for detecting TET. At an excitation wavelength of 395 nm, UiO-66-NH2@TpTt-COF displays significant dual emission at 452 nm and 575 nm. The UiO-66-NH2@TpTt-COF of this invention specifically recognizes TET through π-π interactions and sensitively responds to TET through the intermolecular hydrogen bonds formed between the -NH- / C=N of UiO-66-NH2@TpTt-COF and the -OH / -NH2 of TET. The protons of TET are transferred to the N atom of UiO-66-NH2@TpTt-COF via intermolecular hydrogen bonds, thereby hindering intramolecular charge transfer (ICT) and electret intramolecular proton transfer (ESIPT) processes, ultimately quenching fluorescence. On the other hand, hydrogen bonding promotes the photoinduced electron transfer (PET) effect between TET and UiO-66-NH2@TpTt-COF, further accelerating fluorescence quenching. The UiO-66-NH2@TpTt-COF sensor detects TET... LOD The concentration is approximately 7.4 nmol / L. The dual-emission MOF@COF ratiometric fluorescence sensor constructed in this invention can sensitively detect antibiotics in the environment, which is beneficial for hazard monitoring and food safety.

[0023] This invention constructs a ratio sensor based on the UiO-66-NH2@TpTt-COF composite material for the detection of tetracycline. The introduction of UiO-66-NH2 weakens the aggregation-induced quenching of TpTt-COF, resulting in strong dual emission of UiO-66-NH2@TpTt-COF at 452 nm and 575 nm. Tetracycline (TET) can be recognized by the UiO-66-NH2@TpTt-COF sensor via π-π superposition, and is related to the triazine N and deprotonated O atoms of UiO-66-NH2@TpTt-COF through intermolecular hydrogen bonds. -The interaction between the two molecules promotes the PET effect by inhibiting the synchronous fluorescence quenching of the dual emission of UiO-66-NH2@TpTt-COF induced by ESIPT and ICT. The synchronous response of the UiO-66-NH2@TpTt-COF sensor enhances its specificity, exhibiting good sensitivity for tetracycline detection with a detection limit of 7.4 nmol / L. Fluorescence determination of tetracycline in drinking water and milk using UiO-66-NH2@TpTt-COF showed recoveries of 88.58-104.31%. This invention provides a novel synchronous response sensor for antibiotic detection and offers a new possibility for the application of core-shell MOF@COF composite materials in food safety detection. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the fabrication process of the sensor of the present invention.

[0025] Figure 2 In the image, (a) is the SEM image of UiO-66-NH2; (b) is the SEM image of TpTt-COF; (c) is the SEM image of UiO-66-NH2@TpTt-COF; (d) is the PXRD spectrum of UiO-66-NH2, TpTt-COF and UiO-66-NH2@TpTt-COF; (e) is the FTIR spectrum of UiO-66-NH2, TpTt-COF and UiO-66-NH2@TpTt-COF; and (f) is the UV-Vis spectrum of UiO-66-NH2, TpTt-COF and UiO-66-NH2@TpTt-COF.

[0026] Figure 3 In the diagram, (a) shows the UV-Vis absorption spectrum of TET and the excitation and emission spectra of UiO-66-NH2@TpTt-COF; (b) shows the FTIR spectra of UiO-66-NH2@TpTt-COF before and after the reaction with TET; and (c) shows the FTIR spectra of UiO-66-NH2@TpTt-COF and TET. E LUMO and E HOMO Energy level diagram.

[0027] Figure 4 In the figure, (a) is the fluorescence emission spectrum of UiO-66-NH2@TpTt-COF after adding different concentrations of TET; (b) is the relative fluorescence intensity F of UiO-66-NH2@TpTt-COF. 452 / F 575 and C TET(c) is the linear relationship diagram; (d) is the fluorescence intensity response diagram of UiO-66-NH2@TpTt-COF to TET and different types of interference. Detailed Implementation

[0028] The technical terms used in this invention have the following meanings: tetracycline (TET), intramolecular proton transfer (ESIPT), intramolecular charge transfer (ICT), photoinduced electron transfer (PET), high performance liquid chromatography (HPLC), fluorescence (FL) detection, aggregation quenching (ACQ), 1,3,5-tricarboxymethyl phloroglucinol (Tp), 1,3,5-triazine-2,4,6-triamine (Tt), field emission scanning electron microscopy (SEM), X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectrophotometer (UV-vis), internal filtration effect (IFE), follicle resonance energy transfer (FRET), density generalized function theory (DFT), lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital (HOMO).

[0029] like Figure 1 As shown, the method for preparing the ratio sensor based on the UiO-66-NH2@TpTt-COF composite material of the present invention includes the following steps:

[0030] Preparation of S1 and UiO-66-NH2: First, accurately weigh 0.18 g of ZrCl4 and dissolve it in 40 mL of N,N-dimethylformamide. Sonicate for 15 min until completely dissolved. Then add 0.14 g of 2-aminoterephthalic acid and continue sonicating for 15 min. Add 5 mL of glacial acetic acid. Transfer the above mixed solution to a 100 mL polytetrafluoroethylene reactor liner, heat to 120 °C, keep warm for 24 h, and cool to 26 °C. Wash three times each with N,N-dimethylformamide and methanol, centrifuge at 8000 r / min, collect the particles, and vacuum dry at 70 °C for 12 h to obtain UiO-66-NH2.

[0031] Synthesis of S2 and UiO-66-NH2(-CHO): 30 mg of UiO-66-NH2 and 15 mg of ligand Tp were added to a thick-walled glass tube containing 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide. After sonication for 15 h, 0.1 mL of acid (6 M) was added, and the mixture was heated to 80 °C and kept at that temperature for 24 h. The precipitate was centrifuged at 8000 r / min for 5 min, washed three times each with N,N-dimethylacetamide and acetone, and dried under vacuum at 80 °C for 12 h to obtain the synthesized UiO-66-NH2(-CHO).

[0032] Synthesis of S3, UiO-66-NH2@TpTt-COF: 30 mg of UiO-66-NH2(-CHO), 10 mg of ligand Tp and 5 mg of ligand Tt were added to a 10 mL thick-walled glass tube. 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide were added. After sonication for 15 min, 0.1 mL of acetic acid (6 M) was added. The thick-walled glass tube was then degassed through three freeze-pump-thaw cycles. The tube was sealed and heated to 120 °C and kept at that temperature for 72 h. The resulting precipitate was centrifuged at 8000 r / min for 5 min, washed once each with N,N-dimethylacetamide and acetone, and then vacuum dried at 80 °C for 12 h to obtain UiO-66-NH2@TpTt-COF.

[0033] Characterization of UiO-66-NH2@TpTt-COF: UiO-66-NH2@TpTt-COF was synthesized by attaching TpTt-COF to UiO-66-NH2, and UiO-66-NH2, TpTt-COF, and UiO-66-NH2@TpTt-COF were characterized by SEM, PXRD, and FTIR methods. Figure 2 As shown in (a), the SEM image of the synthesized UiO-66-NH2 reveals a smooth, regular octahedral structure. Figure 2 As shown in (b), TpTt-COF exhibits good crystallinity and an interwoven thread shape. Figure 2 As shown in (c), UiO-66-NH2@TpTt-COF has a solid morphology similar to UiO-66-NH2, but its surface is rougher because the fiber TpTt-COF is attached to the original UiO-66-NH2. This confirms the successful synthesis of UiO-66-NH2@TpTt-COF.

[0034] like Figure 2 As shown in (d), PXRD patterns characterize the crystallinity of UiO-66-NH2, TpTt-COF, and UiO-66-NH2@TpTt-COF. In the figure, diffraction peaks near 7.41°, 8.54°, 12.07°, 25.72°, and 33.11° clearly indicate the (111), (002), (022), (224), and (137) lattice planes of UiO-66-NH2, respectively. The PXRD pattern of TpTt-COF shows strong peaks at 8.3° and 27.1°. The reflection PXRD patterns corresponding to the (100) and (002) lattice planes of TpTt-COF show that the synthesized UiO-66-NH2 nanocrystals and TpTt-COF have high crystallinity, and the positions and intensities of the diffraction peaks are in good agreement with the simulation results (see [reference]). Figure 2(d) The PXRD pattern of UiO-66-NH2@TpTt-COF matches well with that of UiO-66-NH2 and TpTt-COF, indicating that the synthesized UiO-66-NH2@TpTt-COF does not cause significant loss of crystallinity and crystal composition.

[0035] FTIR was used to characterize the surface groups of UiO-66-NH2, TpTt-COF, and UiO-66-NH2@TpTt-COF. Figure 2 As shown in (e), UiO-66-NH2 at 3474 cm⁻¹ -1 and 3360cm -1 The peaks at 3360-3474 cm⁻¹ belong to the NH symmetric and asymmetric stretching vibrations of primary amines (-NH₂), providing abundant active sites for the growth of the TpTt-COF shell. -1 The absorption peak of -NH2 in the tensile mode is significantly weaker, indicating that the -NH2 content in the UiO-66-NH2@TpTt-COF composite material is lower than that in UiO-66-NH2. (The absorption peaks at 1672 and 662 cm⁻¹ are also mentioned.) -1 The peak centered at 1698 cm⁻¹ in the UiO-66-NH₂@TpTt-COF composite belongs to the CO bending vibration and Zr-O tensile mode of UiO-66-NH₂, indicating the presence of UiO-66-NH₂ in the UiO-66-NH₂@TpTt-COF composite. Compared with the FTIR results of UiO-66-NH₂(-CHO), the aldehyde tensile vibration in the UiO-66-NH₂@TpTt-COF composite is more pronounced at 1698 cm⁻¹. -1 The disappearance of the characteristic peak at 1524 cm⁻¹ indicates Schiff base interaction, successfully modifying the TpTt-COF shell on UiO-66-NH₂. UiO-66-NH₂@TpTt-COF shows a peak at 1524 cm⁻¹. -1 (C=C) and 1241cm -1 There are two peaks at (C=C), which is due to the successful incorporation of β-ketoamines into the TpTt-COF shell. Furthermore, in the FTIR spectrum of UiO-66-NH2@TpTt-COF, there is a peak at 812 cm⁻¹. -1 A characteristic peak of tensile vibration of a triazine ring unit was observed, and the intensity of the peak decreased, indicating that the core-shell structure of the UiO-66-NH2@TpTt-COF composite material was successfully synthesized through covalent bonding.

[0036] like Figure 2As shown in (f), the UV-Vis absorption spectra of UiO-66-NH2, TpTt-COF, and UiO-66-NH2@TpTt-COF demonstrate their optical absorption properties. The results show that UiO-66-NH2 exhibits a strong absorption response in the 300-400 nm range, which is attributed to the π-π* transition of the benzene ring and the n-π* transition associated with the amino group. TpTt-COF exhibits strong absorption in both the UV and visible regions. The absorption spectrum of UiO-66-NH2@TpTt-COF inherits the absorption peak of TpTt-COF at 525 nm, and the absorption range of UiO-66-NH2@TpTt-COF is significantly wider than that of UiO-66-NH2, further indicating the successful synthesis of UiO-66-NH2@TpTt-COF.

[0037] The interaction between TET and UiO-66-NH2@TpTt-COF was determined using fluorescence spectroscopy, FTIR, and UV-vis methods. Internal filtration effect (IFE) and fluorescence resonance energy transfer (FRET) are generally considered two common follicle quenching mechanisms. Figure 3 As shown in (a), the UV-Vis absorption spectrum of TET overlaps well with the excitation spectrum of UiO-66-NH2@TpTt-COF, but hardly overlaps with the emission spectrum of UiO-66-NH2@TpTt-COF. Therefore, the ability of TET to selectively quench UiO-66-NH2@TpTt-COF is related to IFE, but not to FRET.

[0038] Furthermore, due to the presence of numerous polar groups on UiO-66-NH2@TpTt-COF and TET, such as -OH, -COOH, -NH2, and -NH-, intermolecular hydrogen bonds may exist between UiO-66-NH2@TpTt-COF and TET. Figure 3As shown in (a), the redshift in fluorescence emission may be due to weak interactions between the TET molecule and the TpTt-COF shell of UiO-66-NH2@TpTt-COF, such as π-conjugation or hydrogen bonding. Therefore, UiO-66-NH2@TpTt-COF can specifically recognize TET through strong π-conjugation and hydrogen bonding. On the other hand, the fluorescence quenching of TET at 452 nm can be explained by the suppression of the ICT effect of TET on UiO-66-NH2@TpTt-COF. The N atoms in the TpTt-COF shell have abundant electron density, and TET is a good hydrogen bond donor; therefore, hydrogen bonds may form between the -NH2 / -OH of TET and the triazine ring of UiO-66-NH2@TpTt-COF. The hydrogen bond formed between the N atom and TET disrupts the ICT effect and the PET effect between UiO-66-NH2@TpTt-COF and TET, reducing the fluorescence intensity at 452 nm. On the other hand, the decrease in fluorescence intensity at 575 nm may be due to the transfer of protons from the -OH / -NH2 groups in TET to the triazine of UiO-66-NH2@TpTt-COF via intermolecular hydrogen bonding, inhibiting the reaction of -NH- with deprotonated O-. - The ESIPT effect between triazines quenched the fluorescence at 575 nm.

[0039] The following analysis examines the FTIR spectra of UiO-66-NH2@TpTt-COF before and after the reaction with TET. Figure 3 (b) FTIR before and after the reaction of UiO-66-NH2@TpTt-COF with TET, showing the position at 3473 cm⁻¹. -1 and 3371cm -1 The -NH2 peak disappears at 3432 cm⁻¹ -1 A new peak appears at 812cm. -1 The intensity of the triazine ring characteristic peak at 1619 cm⁻¹ significantly decreased, indicating that intermolecular hydrogen bonds were formed between the -OH / -NH₂ group of TET and the -NH₃ and C=N groups of UiO-66-NH₂@TpTt-COF. After reacting with TET, the peak intensity at 1619 cm⁻¹... -1 The peak intensity at (CC) increases, from 1300 to 1500 cm⁻¹. -1 The increased cluster peak intensity within the range indicates that UiO-66-NH2@TpTt-COF exhibits a specific interaction with TET through π-π superposition. The lowest unoccupied molecular orbitals (LUMOs) and highest occupied molecular orbitals (HOMOs) of UiO-66-NH2@TpTt-COF and TET in the B3LYP / 3-21G mode were measured using DFT. Figure 3As shown in (c), UiO-66-NH2@TpTt-COF E LUMO and E HOMO The values ​​are -2.54 eV and -5.71 eV, respectively, for TET. E LUMO and E HOMO The energy levels are -3.61 eV and -5.90 eV, respectively. The LUMO level of UiO-66-NH2@TpTt-COF is higher than that of TET, and the energy level difference exhibits a cross-type pattern, allowing electron transfer from UiO-66-NH2@TpTt-COF to TET. This further confirms the PET mechanism between UiO-66-NH2@TpTt-COF and TET. UiO-66-NH2@TpTt-COF specifically recognizes TET through π-π interactions, forming intermolecular hydrogen bonds with TET, inhibiting the ICT and ESIPT processes, and promoting the PET effect, thus specifically responding to TET.

[0040] To evaluate the performance of UiO-66-NH2@TpTt-COF as a ratiometric fluorescence sensor for detecting TET, this invention used titration to measure the fluorescence spectra of UiO-66-NH2@TpTt-COF at different TET concentrations. Figure 4 (a) It can be seen that with the increase of TET concentration, the fluorescence intensity of the double emission at 452 nm and 575 nm gradually decreases, but the intensity of the second emission peak decreases faster, and the fluorescence intensity is higher than that of the second emission peak. F 452 / F 575 (increase) F 452 / F 575 The linear relationship between the TET concentration and the concentration in the range of 0–160.00 μmol / L was good, with a correlation coefficient R0. 2 =0.9996 (see) Figure 4 (b)). In addition, the corresponding linear regression equation for the UiO-66-NH2@TpTt-COF sensor is shown in Equation (1). With an accuracy of ±1% of the emission intensity, the lowest detection limit of UiO-66-NH2@TpTt-COF is 7.4 nmol / L.

[0041] F 452 / F 575 =0.0188C TET +0.9929 (1)

[0042] in, F 452 / F 575 The ratio of fluorescence intensity of the two emission peaks located at 452 nm and 575 nm. C TET It refers to the concentration of TET.

[0043] The results show that UiO-66-NH2@TpTt-COF can be used as a ratiometric fluorescence sensor to determine TET with high sensitivity, while reducing interference from environmental factors and improving its detection sensitivity. The ratiometric fluorescence detection method based on the UiO-66-NH2@TpTt-COF ratio sensor of this invention was compared with other fluorescence detection methods, and the detection results are shown in Table 1.

[0044]

[0045] Compared with existing single-emission and ratiometric fluorescence detection methods, the ratiometric fluorescence detection method of the present invention has a better linear range and a lower detection limit, indicating that the UiO-66-NH2@TpTt-COF sensor has good sensitivity.

[0046] This invention also applies UiO-66-NH2@TpTt-COF to the detection of TET in drinking water and milk. Spiked samples were prepared by adding different concentrations (0, 5.00, 10.00, 20.00 μmol / L) of TET to the samples, and the accuracy of the qualitative analysis was evaluated by the recovery rate of TET. The content of TET in drinking water and milk was determined using high-performance liquid chromatography (HPLC) and liquid chromatography (LC). The results are shown in Table 2.

[0047]

[0048] The detection results show that the UiO-66-NH2@TpTt-COF ratio sensor is consistent with the HPLC method. The recoveries in drinking water and milk ranged from 88.58% to 104.31%, with RSDs ranging from 0.22% to 4.29%. These results demonstrate that the ratio sensor of this invention has good application value in the detection of TET in real samples.

[0049] This invention also investigated the selectivity of UiO-66-NH2@TpTt-COF through comparative experiments with potential interference from other common antibiotics, molecular anions, and cations. Figure 4 As shown in (c), only TET caused a measurable fluorescence change; the fluorescence changes of other common antibiotics and metal cations under the same conditions were negligible. These results indicate that UiO-66-NH2@TpTt-COF is an ideal fluorescence sensor for detecting TET with good selectivity and high sensitivity.

Claims

1. A ratiometric sensor based on UiO-66-NH2@TpTt-COF composite material, characterized in that, By using an interface growth method, a TpTt-COF shell is attached to the surface of UiO-66-NH2 to synthesize a UiO-66-NH2@TpTt-COF composite material with dual emission properties. A ratiometric fluorescence sensor can be constructed using this UiO-66-NH2@TpTt-COF composite material.

2. A ratiometric sensor based on UiO-66-NH2@TpTt-COF composite material, characterized in that, It is prepared by the following method: First, weigh 0.18 g of ZrCl4 according to the formula, dissolve it in 40 mL of N,N-dimethylformamide, and sonicate for 15 min until completely dissolved. Then, add 0.14 g of 2-aminoterephthalic acid, continue sonicating for 15 min, and add 5 mL of glacial acetic acid. Transfer the above mixed solution to a 100 mL polytetrafluoroethylene reactor liner, heat to 120 °C, keep warm for 24 h, and cool to 26 °C. Wash three times each with N,N-dimethylformamide and methanol, centrifuge at 8000 r / min to collect the particles, and vacuum dry at 70 °C for 12 h to obtain UiO-66-NH2. Then, according to the ratio, 30 mg of UiO-66-NH2 and 15 mg of ligand Tp were added to a thick-walled glass tube containing a mixture of 2 ml N,N-dimethylacetamide and 1 ml dimethyl sulfoxide. After sonication for 15 min, 0.1 mL of acetic acid (6 M) was added, and the mixture was heated to 80 °C and kept at that temperature for 24 h. The precipitate was centrifuged at 8000 r / min for 5 min, and then washed three times each with N,N-dimethylacetamide and acetone. The precipitate was then vacuum dried at 80 °C for 12 h to obtain UiO-66-NH2(-CHO). Then, according to the specified ratio, 30 mg of UiO-66-NH2(-CHO), 10 mg of ligand Tp, and 5 mg of ligand Tt were added to a thick-walled glass tube, followed by 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide. After sonication for 15 min, 0.1 mL of acetic acid (6M) was added. The thick-walled glass tube was then degassed by three freeze-pump-thaw cycles. After sealing, it was heated to 120℃ and kept at that temperature for 72 h. The resulting precipitate was centrifuged at 8000 r / min for 5 min, and then washed once each with N,N-dimethylacetamide and acetone. After vacuum drying at 80℃ for 12 h, the UiO-66-NH2@TpTt-COF composite material was obtained. Finally, 10 mg of UiO-66-NH2@TpTt-COF composite material was weighed according to the formula and dissolved in 50 mL of ultrapure water. The solution was ultrasonically treated for 15 min until completely dissolved, thus obtaining a 0.2 mg / mL UiO-66-NH2@TpTt-COF ratio sensor solution.

3. A method for fabricating a ratio sensor based on UiO-66-NH2@TpTt-COF composite material, characterized in that, Includes the following steps: Preparation of S1 and UiO-66-NH2: Weigh 0.18g of ZrCl4 according to the formula, dissolve it in 40mL of N,N-dimethylformamide, sonicate for 15min until completely dissolved, then add 0.14g of 2-aminoterephthalic acid, continue sonication for 15min, then add 5mL of glacial acetic acid, transfer the above mixed solution to a 100mL polytetrafluoroethylene reactor liner, heat to 120℃, keep warm for 24h, cool to 26℃, wash three times each with N,N-dimethylformamide and methanol, centrifuge at 8000r / min to collect particles, and vacuum dry at 70℃ for 12h to obtain UiO-66-NH2; Synthesis of S2 and UiO-66-NH2(-CHO): 30 mg of UiO-66-NH2 and 15 mg of ligand Tp were added to a thick-walled glass tube containing a mixture of 2 ml N,N-dimethylacetamide and 1 ml dimethyl sulfoxide according to the specified ratio. After sonication for 15 min, 0.1 mL of acetic acid (6 M) was added, and the mixture was heated to 80 °C and kept at that temperature for 24 h. The precipitate was centrifuged at 8000 r / min for 5 min, and then washed three times each with N,N-dimethylacetamide and acetone. The precipitate was then vacuum dried at 80 °C for 12 h to obtain UiO-66-NH2(-CHO). Synthesis of S3, UiO-66-NH2@TpTt-COF composite material: 30 mg of UiO-66-NH2(-CHO), 10 mg of ligand Tp and 5 mg of ligand Tt were added to a thick-walled glass tube according to the specified ratio. Then, 2 mL of N,N-dimethylacetamide and 1 mL of dimethyl sulfoxide were added. After sonication for 15 min, 0.1 mL of acetic acid (6M) was added. The thick-walled glass tube was then degassed by three freeze-pump-thaw cycles. After sealing, it was heated to 120℃ and kept at that temperature for 72 h. The precipitate was centrifuged at 8000 r / min for 5 min and then washed once each with N,N-dimethylacetamide and acetone. After vacuum drying at 80℃ for 12 h, the UiO-66-NH2@TpTt-COF composite material was obtained. S4. Preparation of UiO-66-NH2@TpTt-COF ratio sensor: Weigh 10mg of UiO-66-NH2@TpTt-COF composite material according to the ratio and dissolve it in 50mL of ultrapure water. Sonicate for 15min until completely dissolved to obtain a 0.2mg / mL UiO-66-NH2@TpTt-COF ratio sensor solution.

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