A multi-channel fluorescence sensor array for detecting hexavalent chromium in aqueous bodies

Abstract

The present application relates to a kind of multichannel fluorescence sensor array materials for Cr2O7 2‑ And CrO4 2‑ Detection in water body. Material is carbon dot functionalized multi-rare earth metal organic framework material (CDs@La-MOFs:3%Eu 3+ ,7%Tb 3+ ). The material has good pH and structural stability, while having red green blue three emission centers. CDs@La-MOFs:3%Eu 3+ ,7%Tb 3+ Composite material is used for the recognition detection of sixteen anions, and it is found that Cr2O7 2‑ And CrO4 2‑ Three emission center bands of the material show different degrees of fluorescence quenching response signals. In addition, the different three fluorescence response signal values generated by Cr2O7 2‑ And CrO4 2‑ To composite material, a multichannel fluorescence sensing array is constructed to realize the simultaneous recognition of Cr2O7 2‑ And CrO4 2‑ Two kinds of anions.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of carbon dot and rare earth metal-organic framework composite materials, specifically a Cr2O7 composite material that can be used in water. 2- and CrO4 2- Preparation and application of lanthanum trimellitate metal-organic framework materials doped with carbon dots and rare earth ions europium and terbium. Background Technology

[0002] Chromium is one of the most widely used metals in modern industry and agriculture, especially hexavalent chromium (Cr(VI)), which remains stable in ecosystems, mostly in the form of the oxyacid anion Cr2O7. 2- and CrO4 2- Cr(VI) exists in various forms. Excessive use and emissions of Cr(VI) products lead to increasing exposure of the biological environment and humans to Cr(VI). Unfortunately, Cr(VI) is highly toxic, easily accumulates in the environment, and is non-biodegradable, posing a persistent threat to the ecological environment. Furthermore, the human body readily absorbs Cr(VI) pollutants, posing significant risks to human health. Studies have shown that Cr(VI) may cause hereditary gene defects, allergic reactions, kidney and liver damage, and various cancers. Cr(VI) anion (Cr₂O₇) 2- / CrO4 2- As a potent carcinogen and mutagen, Cr(VI) is classified as a highly toxic pollutant by the U.S. Environmental Protection Agency, and the World Health Organization (WHO) sets the upper limit for Cr(VI) concentration in drinking water at 50 μg / L (0.96 μM). Therefore, accurate detection and determination of Cr(VI) in the aquatic environment is crucial for environmental protection and human safety. Currently, researchers have developed several methods for Cr(VI) detection, such as atomic absorption spectrometry, chromatography, and inductively coupled plasma mass spectrometry. However, these traditional detection techniques often require significant time, manpower, and economic costs. Fluorescence sensing technology, due to its fast response, simple operation, and low cost, has gained widespread acceptance in the sensing field, especially in the research of novel fluorescent probe materials for ratiometric detection, which remains of great practical significance.

[0003] Metal-organic frameworks (MOFs) are porous crystalline hybrid materials self-assembled from multidentate-bridged organic ligands and inorganic metal ions or clusters. Over the past few decades, they have been studied for various applications, such as gas storage and separation, catalysis, chemical sensing, and drug delivery. Carbon dots (CDs) are a newly discovered and promising class of carbon nanomaterials. Compared with traditional fluorescent materials such as organic dyes and semiconductor quantum dots, CDs possess advantages including low toxicity, ease of synthesis and functionalization, high water solubility, photochemical stability (resistance to photobleaching), and good biocompatibility. Due to their excellent physicochemical properties, abundant synthesis methods, and superior luminescence properties, CDs have been successfully used for the detection of some substances. Therefore, CDs can serve as ideal luminescent guests for MOFs. Introducing CDs into MOFs with strong encapsulation capabilities to prepare functionalized composite materials combines the hybrid characteristics of MOFs with the unique optical properties of CDs. This strategy is an effective approach for preparing next-generation fluorescent sensors. To date, the simultaneous identification of Cr2O7... 2- and CrO4 2- Ratio-modulated fluorescent probe materials are still relatively scarce. Therefore, developing a sensitive, rapid, and simple trace Cr2O7 probe is crucial. 2- and CrO4 2- Fluorescent methods for ion detection have attracted much attention. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a Cr2O7 solution that can be used in water. 2- and CrO4 2- Preparation and application of lanthanum trimellitate metal-organic framework materials doped with carbon dots and rare earth ions europium and terbium.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a Cr2O7 solution that can be used in water. 2- and CrO4 2- The preparation and application of lanthanum trimellitate metal-organic framework materials doped with europium and terbium rare earth ions, as detected by the test, are as follows:

[0006] S1, select raw materials, pyromellitic acid, La(NO3)3·6H2O, Eu(NO3)3·6H2O and Tb(NO3)3·6H2O to prepare rare earth metal-organic frameworks;

[0007] S2, Dissolve pyromellitic acid in anhydrous ethanol and stir;

[0008] S3, add 0.05M La(NO3)3·6H2O solution to the solution obtained in S2, and then add different proportions of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O aqueous solutions (all at a concentration of 0.05M), and stir;

[0009] S4 forms a large amount of white precipitate. After standing at room temperature, the white precipitate is collected by centrifugation, washed and dried to obtain a white rare earth metal-organic framework material.

[0010] S5, Selecting folic acid as the raw material to prepare CDs;

[0011] S6. Dissolve folic acid in distilled water and stir.

[0012] S7. Transfer the S6 solution to a high-pressure reactor. After it has completely cooled, remove the macromolecules using a microporous filter membrane and store it in a refrigerator for later use.

[0013] S8, mix the rare earth metal-organic framework material in S4 with the solution obtained in S7, and stir;

[0014] S9, centrifuge to collect the precipitate sample, dry and grind to obtain lanthanum pyromellitic tricarboxylate metal-organic framework material doped with carbon dots and rare earth ions europium and terbium;

[0015] S10, the obtained carbon dots and rare earth ion europium and terbium-doped lanthanum trimellitate metal-organic framework material were used for the detection of anions in Cr2O7. 2- and CrO4 2- Ion detection;

[0016] S11, using Cr2O7 2- and CrO4 2- A multi-channel sensor array was constructed by performing LDA calculations on the different fluorescence quenching results of the three emission bands of the ion-paired composite material. This sensor array can effectively and simultaneously distinguish Cr2O7. 2- and CrO4 2- ion.

[0017] Preferably, step S2 involves stirring at room temperature until dissolved, step S3 involves stirring at room temperature for 60 minutes, step S6 involves vigorous stirring at room temperature for 30 minutes, and step S8 involves stirring at room temperature for 24 hours.

[0018] Preferably, the resting time in step S4 is 24 hours and the drying temperature is 60°C.

[0019] Preferably, in step S3, the proportions of La-MOFs are mTb. 3+ ,nEu 3+ (n=10%-m, n=1%, 3%, 5%, 7%, 9%).

[0020] Preferably, the detection in step S10 is the effect of the material on Cr2O7 in water. 2- and CrO4 2- Stability, selectivity, anti-interference ability, and sensitivity of ion recognition.

[0021] Compared with existing technologies, the advantages of this invention are: This invention uses rare earth ions europium and terbium, along with trimesolic acid (TMA) which has a symmetrical structure and multiple coordination sites, as raw materials to form a rare earth metal-organic framework. Simultaneously, it uses carbon dots (folic acid) for recombination to obtain a ratiometric fluorescent probe, which can more sensitively and accurately identify and detect Cr2O7. 2- and CrO4 2- ion. Attached Figure Description

[0022] Figure 1 The La(TMA)(H2O)6 single crystal simulation and synthetic crystal La-MOFs in this invention: 3% Eu 3+ 7% Tb 3+ CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ XRD pattern of the sample (a); ligands, La-MOFs: 3% Eu 3+ 7% Tb 3+ CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Fourier transform infrared spectrum of the sample (b);

[0023] Figure 2 The La-MOFs in this invention are 3% Eu. 3+ 7% Tb 3+ SEM images (a) and EDX spectra (b); CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ SEM image (c) and EDX spectrum (d);

[0024] Figure 3 In this invention, CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Element mapping graph;

[0025] Figure 4 The La-MOFs in this invention are 3% Eu. 3+ 7% Tb 3+ (a) and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ (b) Thermogravimetric curve;

[0026] Figure 5 La-MOFs:mEu in this invention 3+ ,nTb 3+ (a) Emission spectrum of the sample; (b) La-MOFs: 3% Eu3+ 7% Tb 3+ Fluorescence spectrum of the sample;

[0027] Figure 6 The excitation and emission spectra of the CDs of this invention are shown in the figures, with the insets showing the corresponding CIE chromaticity diagrams and photographs under ultraviolet light.

[0028] Figure 7 In this invention, CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Excitation spectra at different monitoring wavelengths (Em = 445 / 545 / 616 nm) (a); CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Emission spectra at different excitation wavelengths (260–285 nm) (b);

[0029] Figure 8 The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ The emission spectrum;

[0030] Figure 9 The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ XRD patterns in solutions at different pH values ​​(a); CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ XRD patterns of immersion in water for different times (b);

[0031] Figure 10 The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Emission spectra (a) and intensity changes (b) under different pH conditions; CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Emission spectra (c) and intensity variations (d) under different time conditions.

[0032] Figure 11 The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Emission spectra in different anion solutions (a); CDs@La-MOFs:3% Eu in different anion aqueous solutions 3+ 7% Tb 3+ The variation of the intensity pairs of the three emission peaks (1-I / I0)(b);

[0033] Figure 12The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Exposure to Cr2O7 2- Changes in the three emission bands (1-I / I0) in solutions coexisting with other anions (a); CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Exposure to CrO4 2- Changes in the three emission bands (1-I / I0)(b) when coexisting with other anions;

[0034] Figure 13 The present invention is CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Cr2O7 at different concentrations (0–250 μM) 2- Fluorescence emission spectrum in solution (a); containing Cr2O7 2- Fluorescence response of the three emission bands of the ions (b); CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ CrO4 at different concentrations (0–250 μM) 2- Fluorescence emission spectrum in solution (c); Containing CrO4 2- Fluorescence response of the three emission bands of the ion (d);

[0035] Figure 14 The fluorescence intensity ratio of this invention is I 545 / I 445 (a) and I 616 / I 445 (b) with Cr2O7 respectively 2- The relationship between concentrations; fluorescence intensity ratio I 545 / I 445 (c) and I 616 / I 445 (d) reacted with CrO4 2- The relationship between concentrations. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1:

[0038] See Figure 1A type of Cr2O7 that can be used in water 2- and CrO4 2- The preparation and application of lanthanum trimellitate metal-organic framework materials doped with europium and terbium rare earth ions, as detected by the assay, are as follows:

[0039] S1, select raw materials, pyromellitic acid, La(NO3)3·6H2O, Eu(NO3)3·6H2O and Tb(NO3)3·6H2O to prepare rare earth metal-organic frameworks;

[0040] S2, Dissolve pyromellitic acid in anhydrous ethanol and stir;

[0041] S3, add 0.05M La(NO3)3·6H2O solution to the solution obtained in S2, and then add different proportions of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O aqueous solutions (all at a concentration of 0.05M), and stir;

[0042] S4 forms a large amount of white precipitate. After standing at room temperature, the white precipitate is collected by centrifugation, washed and dried to obtain a white rare earth metal-organic framework material.

[0043] S5, Selecting folic acid as the raw material to prepare CDs;

[0044] S6. Dissolve folic acid in distilled water and stir.

[0045] S7. Transfer the S6 solution to a high-pressure reactor. After it has completely cooled, remove the macromolecules using a microporous filter membrane and store it in a refrigerator for later use.

[0046] S8, mix the rare earth metal-organic framework material in S4 with the solution obtained in S7, and stir;

[0047] S9, centrifuge to collect the precipitate sample, dry and grind to obtain lanthanum pyromellitic tricarboxylate metal-organic framework material doped with carbon dots and rare earth ions europium and terbium;

[0048] S10, the obtained carbon dots and rare earth ion europium and terbium-doped lanthanum trimellitate metal-organic framework material were used for the detection of anions in Cr2O7. 2- and CrO4 2- Ion detection;

[0049] S11, using Cr2O7 2- and CrO4 2- A multi-channel sensor array was constructed by performing LDA calculations on the different fluorescence quenching results of the three emission bands of the ion-paired composite material. This sensor array can effectively and simultaneously distinguish Cr2O7. 2- and CrO4 2- ion.

[0050] Furthermore, step S2 involves stirring at room temperature until dissolved, step S3 involves stirring at room temperature for 60 minutes, step S6 involves vigorous stirring at room temperature for 30 minutes, and step S8 involves stirring at room temperature for 24 hours.

[0051] Furthermore, in step S4, the settling time is 24 hours and the drying temperature is 60°C.

[0052] Furthermore, in step S3, the La-MOFs are used in different proportions, with a proportion of mTb. 3+ ,nEu 3+ (n=10%-m, n=1%, 3%, 5%, 7%, 9%).

[0053] Furthermore, the detection in step S10 refers to the effect of this material on Cr2O7 in the water. 2- and CrO4 2- Stability, selectivity, anti-interference ability, and sensitivity of ion recognition.

[0054] Among them, the water stability and pH stability of the prepared carbon dot functionalized rare earth metal-organic framework materials were tested: pH stability test: seven groups of 20mg CDs@La-MOFs: 3% Eu were weighed. 3+ 7% Tb 3+ The sample powder was soaked in 10 mL of aqueous solutions with different pH values ​​(pH = 3–9) for 24 h, then centrifuged and dried. Its XRD pattern and fluorescence emission spectrum were then measured. Water stability test: Four groups of 20 mg CDs@La-MOFs:3% Eu were weighed. 3+ 7% Tb 3+ The sample powder was soaked in 10 mL of aqueous solution for 1, 3, 5, 7 and 14 days, respectively. After centrifugation and drying, its XRD pattern and fluorescence emission spectrum were collected.

[0055] The prepared carbon dot-functionalized rare-earth metal-organic framework materials were used for selective assays of different anions in aqueous solutions: all anion detections were performed in Tris-HCl buffer (pH = 7.4). Anion SO42- 2- S 2- NO 3- NO 2- F - Cl - ,Br - I - H2PO4 - HPO4 2- S2O3 2- CH3COO - CO3 2- C2O4 2- It is a sodium salt, Cr2O72- and CrO4 2- It is a potassium salt. Cr2O7 2- and CrO4 2- The final concentrations were 0, 1, 10, 25, 50, 100, 150, and 250 μM, with the remaining anion concentrations all at 250 μM. Weigh out 3 mg of CDs@La-MOFs:3% Eu. 3+ 7% Tb 3+ After adding 4 mL of anion exchange solution to the sample, the mixture was sonicated to form a stable mixed suspension, and the fluorescence spectrum of the mixed suspension was tested.

[0056] The prepared carbon dot-functionalized rare earth metal-organic framework materials were used to control Cr2O7 in the presence of different anions. 2- and CrO4 2- Anti-interference testing for SO42- anions: All anion detections were performed in Tris-HCl buffer (pH = 7.4). 2- S 2- NO 3- NO 2- F - Cl - ,Br - I - H2PO4 - HPO4 2- S2O3 2- CH3COO - CO3 2- C2O4 2- It is a sodium salt, Cr2O7 2- and CrO4 2- It is a potassium salt. Cr2O7 2- and CrO4 2- The final concentrations were 0, 1, 10, 25, 50, 100, 150, and 250 μM, with the remaining anion concentrations all at 250 μM. Weigh out 3 mg of CDs@La-MOFs:3% Eu. 3+ 7% Tb 3+ After adding 4 mL of anion exchange solution to the sample, the mixture was sonicated to form a stable mixed suspension, and the fluorescence spectrum of the mixed suspension was tested.

[0057] The prepared carbon dot functionalized rare earth metal-organic framework material for Cr2O7 2- and CrO4 2- Sensitivity testing: All anion detections were performed in Tris-HCl buffer (pH = 7.4). SO42- anion 2- S 2- NO 3- NO 2- F- Cl - ,Br - I - H2PO4 - HPO4 2- S2O3 2- CH3COO - CO3 2- C2O4 2- It is a sodium salt, Cr2O7 2- and CrO4 2- It is a potassium salt. Cr2O7 2- and CrO4 2- The final concentrations were 0, 1, 10, 25, 50, 100, 150, and 250 μM, with the remaining anion concentrations all at 250 μM. Weigh out 3 mg of CDs@La-MOFs:3% Eu. 3+ 7% Tb 3+ After adding 4 mL of anion exchange solution to the sample, the mixture was sonicated to form a stable mixed suspension, and the fluorescence spectrum of the mixed suspension was tested.

[0058] The samples were structurally characterized as rare earth metal-organic framework materials and carbon dot-functionalized rare earth metal-organic framework materials.

[0059] XRD testing: To investigate the structure of the obtained product, XRD was used to characterize it. First, XRD tests were performed to verify the crystal structure of the prepared sample, such as... Figure 1 As shown in (a), the simulated XRD pattern of La(TMA)(H2O)6 single crystal and the synthesized crystal La-MOFs:3% Eu are presented. 3+ 7% Tb 3+ and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ XRD patterns of the samples. It can be observed that the positions of the XRD diffraction peaks of all samples match those of the XRD diffraction peaks of the single-crystal simulated La(TMA)(H2O)6, and no other impurity peaks were detected. This result confirms the synthesized La-MOFs: 3% Eu 3+ 7% Tb 3+ The material is isomorphous with the single-crystal simulated La(TMA)(H2O)6 crystal. (CDs@La-MOFs: 3% Eu) 3+ 7% Tb 3+ No diffraction peaks belonging to CDs were detected in the XRD pattern, which may be due to the low content of CDs and their encapsulation within the MOF framework structure.

[0060] Infrared spectroscopy analysis: Ligand TMA, La-MOFs: 3% Eu 3+7% Tb 3+ and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ FT-IR of the sample, such as Figure 1 As shown in (b), the non-free carboxyl peak belonging to the ligand is located at 1721 cm⁻¹. -1 and 537cm -1 In La-MOFs: 3% Eu 3+ 7% Tb 3+ and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The characteristic bands of non-free carboxyl groups disappeared, while those at 1613, 1556, 1432, and 1373 cm⁻¹ appeared. -1 The -COO appeared - The new spectral bands indicate that rare earth ions are successfully coordinated with ligand TMA.

[0061] SEM analysis: Figure 2 (a) and (c) are samples of La-MOFs: 3% Eu, respectively. 3+ 7% Tb 3+ and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The SEM morphology images show that La-MOFs: 3% Eu 3+ 7% Tb 3+ The material exhibits a bundled structure, and its morphology shows no significant change after the addition of CDs. No characteristic peaks belonging to CDs were observed by XRD and IR, which may be due to insufficient CD encapsulation. Therefore, other testing methods were used to confirm the successful introduction of CDs into La-MOFs:3%Eu. 3+ 7% Tb 3+ In the structure. For example... Figure 2 (b) and (d) show samples La-MOFs: 3% Eu 3+ 7% Tb 3+ and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The EDX spectrum. From Figure 2 (b) shows that La-MOFs: 3% Eu 3+ 7% Tb 3+ It contains five elements: C, O, La, Eu, and Tb, which are consistent with the target elements for material preparation. Figure 2 (d) Displaying CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+The sample contains six elements: C, O, La, Eu, Tb, and N. After the addition of CDs, the EDX spectrum showed the addition of N, which belongs to the CDs material.

[0062] Mapping analysis: CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Elemental mapping diagram of the sample, such as Figure 3 As shown, it was demonstrated that in CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ The six characteristic elements C, O, La, Eu, Tb, and N in the sample were uniformly dispersed in the matrix material. These results indicate that CDs functionalized CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The composite material was successfully prepared.

[0063] Thermogravimetric analysis: Thermal stability is also one of the criteria for evaluating the performance of fluorescent probes. La-MOFs: 3% Eu 3+ 7% Tb 3+ Samples and CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The thermogravimetric curve of the sample shows ( Figure 4 The sample exhibits approximately two weight loss ranges. First, La-MOFs: 3% Eu 3+ 7% Tb 3+ The sample experienced its first weight loss at 50–150 °C, with a weight loss rate of 22.54%, primarily due to the loss of free and coordinated water molecules within the material. No significant weight loss was observed in the 150–425 °C range, indicating excellent thermal stability. A second weight loss occurred at 425–525 °C, with a larger weight loss rate (40.39%), attributed to the overall decomposition of the matrix material. CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The weight loss process of the sample and La-MOFs: 3% Eu 3+ 7% Tb 3+ They are basically the same. The difference is that CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The second weight loss of the sample occurred in the range of 425–585 °C, which indicates that the composite material CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ It has superior thermal stability.

[0064] Furthermore, the performance of the carbon dot-functionalized rare earth metal-organic framework material of this invention is characterized.

[0065] Excitation and emission spectra of La-MOFs: La-MOFs:mEu 3+ ,nTb 3+ fluorescence properties and Eu 3+ and Tb 3+ The amount added is significantly related to this. This is important for studying La-MOFs:mEu 3+ ,nTb 3+ The luminescence of the sample was recorded with different amounts of Eu added. 3+ and Tb 3+ The prepared La-MOFs:mEu 3+ ,nTb 3+ Sample. Results as follows Figure 5 As shown in (a), it can be clearly observed that Eu is present in the emission spectra of all samples. 3+ and Tb 3+ The characteristic emission peaks are located at 616nm and 545nm, with the strongest emission peaks at 616nm and 545nm, respectively, which are formed by... 5 D0→ 7 F2 and 5 D4→ 7 This is generated by the F5 transition. With Tb 3+ As the amount of Eu increases, the emission intensity of the characteristic peak at 545 nm also gradually increases. Conversely, the emission intensity of the characteristic peak at 616 nm increases with the amount of Eu added. 3+ The fluorescence intensity decreased with decreasing content. Ultimately, La-MOFs with comparable fluorescence intensity at 616 nm and 545 nm were selected: 3% Eu. 3+ 7% Tb 3+ The sample was then used for subsequent experiments. Figure 5 (b) Demonstrates La-MOFs: 3% Eu 3+ 7% Tb 3+ Fluorescence spectra of the samples. Excitation spectra obtained at monitoring wavelengths of 616 nm and 545 nm showed a broad and strong excitation peak in the 200-300 nm range, originating from the π→π* electronic transition of the ligand. The strongest excitation wavelength was located at 258 nm. La-MOFs: 3% Eu were recorded under 258 nm excitation. 3+ 7% Tb 3+ The emission spectrum showed Eu at 616 nm and 544 nm, respectively. 3+ and Tb 3+ The characteristic emission peaks indicate that La-MOFs: 3% Eu 3+ 7% Tb 3+ The material was successfully prepared.

[0066] Excitation and emission spectra of CDs: To construct fluorescent materials with multiple emission centers, we attempted to introduce a fluorescent guest molecule into La-MOFs: 3% Eu 3+ 7% Tb 3+ Among the materials, fluorescein dimethyl ethers (CDs) possess advantages such as small size, excellent photoluminescence properties, and good biocompatibility, making them a feasible option for encapsulating fluorescent guest molecules. Ultimately, a non-toxic folic acid drug was chosen to synthesize blue-emitting fluorescent CDs via a one-step hydrothermal method. Figure 6 The fluorescence spectrum of CDs is shown. The strongest emission peak of CDs appears at 445 nm, which is typical of blue emission fluorescent materials.

[0067] CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Excitation and emission spectra: The prepared CDs were encapsulated in La-MOFs: 3% Eu using a post-synthetic modification method. 3+ 7% Tb 3+ middle, Figure 7 (a) CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Excitation spectra were obtained under three different emission wavelengths. As expected, a broad excitation peak appeared in the 200–300 nm range at both 545 nm and 616 nm detection wavelengths. However, at a detection wavelength of 445 nm, two excitation peaks appeared simultaneously; the peak around 370 nm was due to absorption by CDs. The overlapping region of the three excitation spectra, within the 220–300 nm range, ensured that CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ It exhibits three emissions. Therefore, in order to find the optimal excitation wavelength, the emission spectrum in this range was tested, such as... Figure 7 As shown in (b). With increasing excitation wavelength, Eu 3+ and Tb 3+ The fluorescence intensity of CDs gradually decreased, while the fluorescence intensity of CDs initially increased and then decreased. Ultimately, the excitation wavelength (275 nm) at which the emission peak intensity of CDs was highest was selected as the optimal excitation for subsequent studies. CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ emission spectrum such as Figure 8 As shown, there are three strongest emission peaks in total, with the emission peaks at 544nm and 616nm originating from... 5 D0→ 7 F2 and 5 D4→ 7 The F5 characteristic transition peak, while the one at 445nm originates from CDs.

[0068] Example 2

[0069] This invention utilizes carbon dot-functionalized rare-earth metal-organic framework materials as fluorescent probes for the detection of Cr2O7. 2- and CrO4 2 .

[0070] Stability: As a fluorescent probe for anion detection in aquatic environments, the material's tolerance to environmental changes is also essential. For CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The stability of the samples in different environments was investigated in detail. For example... Figure 9 As shown in (a) and (b), CDs@La-MOFs:3%Eu 3+ 7% Tb 3+ XRD patterns were obtained after immersion in solutions with different pH values ​​(pH = 3–10) and for different durations (1, 3, 5, 7, and 14 days) in water. The figures show that changes in the aquatic environment had no effect on the crystal structure of the samples. Then, XRD patterns were obtained for CDs@La-MOFs:3% Eu. 3+ 7% Tb 3+ The fluorescence stability of the samples under different environments was also studied. Figure 10 (a) and (b) are CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The fluorescence intensity of the sample under pH conditions showed no significant change, even in environments with large variations in pH. Furthermore, the sample exhibited stable fluorescence intensity after immersion in water for different durations. Figure 10 As shown in (c) and (d). All the above test results indicate that CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The sample exhibits extremely high tolerance to environmental changes. CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The sample can be used as a fluorescent sensing probe for detecting anions in water.

[0071] Selectivity: Next, we will examine CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Whether the material can be used as a fluorescent probe for anion sensing was investigated by combining a certain amount of CDs@La-MOFs:3% Eu. 3+ 7% Tb 3+ The samples were dispersed in different anion solutions (SO4) 2- S 2- NO 3-NO 2- F - Cl - ,Br - I - H2PO4 - HPO4 2- S2O3 2- CH3COO - CO3 2- C2O4 2- Cr2O7 2- CrO4 2- The fluorescence emission spectra of the samples were tested under the same conditions. Figure 11 In (a), it can be clearly observed that, except for Cr2O7 2- and CrO4 2- Other anionic components besides CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The effect of the fluorescence intensity changes on the three characteristic emission bands is weak and negligible. However, in the presence of Cr2O7... 2- and CrO4 2- The emission spectra obtained from the suspension all showed varying degrees of decrease in the three emission peaks. This indicates that CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The fluorescence signal of the material can simultaneously affect Cr2O7 2- and CrO4 2- The two anions produce a response, which holds promise for use in Cr2O7. 2- and CrO4 2- The identification of anions in CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ The effect of sample fluorescence was investigated by analyzing in detail the changes in fluorescence intensity (1-I / I0, where I0 and I are the fluorescence intensities before and after the addition of the ions, respectively) of the three characteristic emission bands for each of the 16 anions. The results are as follows: Figure 11 As shown in (b). Removal of Cr2O7 2- and CrO4 2- The other 14 anions paired with CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ The influence of sample fluorescence was minimal. Cr2O7 2- and CrO4 2- Although for CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+All three characteristic emission bands of the sample exhibited weakened response signals, but the degree of fluorescence quenching differed between them. This is advantageous for subsequently constructing a fluorescence sensing array based on the changes in the three fluorescence signals, thereby enabling simultaneous differentiation of Cr2O7. 2- and CrO4 2- .

[0072] Anti-interference: Real-world detection scenarios are often complex, with polluting ions frequently coexisting in environmental water bodies. Therefore, further testing with a mixed ion solution of CDs@La-MOFs:3% Eu is necessary. 3+ 7% Tb 3+ Fluorescence testing of the material is conducted to investigate its anti-interference performance, which is also an important factor in evaluating the performance of fluorescent probes. For example... Figure 12 As shown, Cr2O7 is displayed. 2- and CrO4 2- They were compared with 14 other anions (SO4) 2- S 2- NO 3- NO 2- F - Cl - ,Br - I - H2PO4 - HPO4 2- S2O3 2- CH3COO - CO3 2- C2O4 2- The fluorescence intensity changes when coexisting with other interfering ions. It can be observed that even when coexisting with other interfering ions, CDs@La-MOFs:3%Eu 3+ 7% Tb 3+ The intensity variations of the three emission bands in the sample were all similar to those of Cr2O7 alone. 2- and CrO4 2- The changes were consistent when they were present. This indicates that CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Materials for Cr2O7 2- and CrO4 2- Its recognition function is not affected by other anions, and it has excellent anti-interference detection performance.

[0073] Sensitivity: In the above studies, CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ Material for Cr2O7 2- and CrO4 2-Having demonstrated excellent qualitative detection capabilities, the next step was to explore the quantitative detection capabilities of the materials in detail. For example... Figure 13 As shown, with Cr2O7 2- and CrO4 2- The concentration was increased from 0 to 250 μM, CDs@La-MOFs: 3% Eu 3+ 7% Tb 3+ All three emission bands of the material exhibited quenching response signals, but the degree of decrease in fluorescence intensity differed. From Figure 13 (b) It can also be clearly observed that with the increase of Cr2O7 2- As the concentration of CrO4 increases, the three characteristic emission bands exhibit different decreasing trends. Similarly, with increasing CrO4 concentration, the emission bands decrease in the same direction. 2- With increasing Cr2O7 concentration, the three characteristic emission bands showed varying degrees of decrease, but this is consistent with the effects of adding Cr2O7. 2- The fluorescence response varies over time. Figure 13 (c) and Figure 13 (d)). Further analysis of Cr2O7 2- and CrO4 2- Concentration changes with CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Fluorescence intensity change ratio (I) 545 / I 445 and I 616 / I 445 Fitting a linear relationship. For example... Figure 14 (a) and Figure 14 As shown in (b), within the concentration range of 0–250 μM, I 545 / I 445 and I 616 / I 445 With Cr2O7 2- The concentration showed a good linear dependence relationship, with a high linear correlation coefficient (R0). 2 =0.9930 and R 2 =0.9921). Within the same concentration range (0–250 μM), CrO4 2- The concentration is also related to the fluorescence intensity ratio (I 545 / I 445 and I 616 / I 445 There is a good linear relationship. Figure 14 (c) and Figure 14 (d)), R 2 The values ​​are 0.9809 and 0.9915, respectively. Using the 3σ / K equation (σ = standard deviation of the blank solution, K = slope of the fitted curve), the values ​​of Cr₂O₇ are calculated. 2- and CrO42- The limits of detection (LODs) were 0.28 μM and 0.31 μM, respectively, which are lower than the World Health Organization's maximum permitted concentration of Cr(VI) in drinking water of 0.96 μM. Therefore, CDs@La-MOFs:3% Eu 3+ 7% Tb 3+ Material for Cr2O7 2- and CrO4 2- With excellent selectivity and high sensitivity, this material shows promise for use in environmental applications involving Cr(VI)(Cr2O7). 2- and CrO4 2- Monitoring of CDs@La-MOFs: 3% Eu. 3+ 7% Tb 3+ The fluorescent sensing probe exhibits superior sensitivity for Cr(VI) detection compared to most other sensing systems, demonstrating a wider detection range and a lower LOD value.

[0074] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 Cr2O7 that can be used in water bodies 2- and CrO4 2- The multi-channel fluorescence sensor array material for detection is characterized by The preparation method includes the following steps: P1. Select raw materials: pyromellitic acid, La(NO3)3·6H2O, Eu(NO3)3·6H2O and Tb(NO3)3·6H2O. Dissolve pyromellitic acid in anhydrous ethanol and stir. Add La(NO3)3·6H2O solution, and then add aqueous solutions of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O in different proportions and stir. A large amount of white precipitate is formed. After standing at room temperature, the white precipitate is collected by centrifugation, washed and dried to obtain a white rare earth metal-organic framework. P2, using folic acid as the raw material, blue fluorescent carbon dots were prepared by hydrothermal method; P3, add the rare earth metal-organic framework material in P1 to the solution in P2 and mix to obtain carbon dot functionalized multi-rare earth metal-organic framework material. P4, the carbon dot-functionalized multi-rare earth metal-organic framework material used in Cr2O7 2- and CrO4 2- Ion detection; P5, using Cr2O7 2- and CrO4 2- A multi-channel sensor array was constructed by performing LDA calculations on different fluorescence quenching results of ion-paired composite materials.

2. The Cr2O7 as described in claim 1, which can be used in water bodies 2- and CrO4 2- The multi-channel fluorescence sensor array material for detection is characterized by: In step P1, the molar ratio of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O is m:n, where n = 10% - m, n = 1%, 3%, 5%, 7%, 9%.

3. The Cr2O7 as described in claim 1, which can be used in water bodies 2- and CrO4 2- The multi-channel fluorescence sensor array material for detection is characterized by: In step P2, the reaction temperature is 180 °C and the reaction time is 2 h.

4. The Cr2O7 as described in claim 1, which can be used in water bodies 2- and CrO4 2- The multi-channel fluorescence sensor array material for detection is characterized by: In step P3, the mass of rare earth metal-organic framework material is 50 mg, the CDs solution is 10 mL, and after stirring at room temperature for 24 h, the precipitate sample is collected by centrifugation.

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