Fluorescent sensing material for detecting Cu < 2 + >, Ag < + > and Au < 3 + > ions as well as preparation method and application of fluorescent sensing material

Abstract

The invention discloses a fluorescent sensing material for detecting Cu < 2 + >, Ag < + > and Au < 3 + > ions as well as a preparation method and application of the fluorescent sensing material. Specifically, the crystal belongs to a monoclinic system, the space group is P21 / n, the molecular formula is C122H96N4O16Zn4, the molecular weight is 2135.50, the cell parameters a are equal to 13.8299 (7), the cell parameters b are equal to 22.8747 (12), the cell parameters c are equal to 31.8830 (16), the cell parameters alpha are equal to 90 degrees, the cell parameters beta are equal to 95.746 (2) degrees, and the cell parameters gamma are equal to 90 degrees. The prepared fluorescence sensing material has a clear space structure and an accurate molecular formula, can efficiently and rapidly detect Ag < + >, Cu < 2 + > and Au < 3 + > ions, and has a wide application prospect as a fluorescence sensor. The technology has the advantages of simplicity in operation, low cost, stable performance and the like.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence sensing materials and crystal material chemistry, and relates to a method for detecting Cu. 2+ Ag + Au 3+ Fluorescent sensing materials for ions, their preparation methods and applications. Background Technology

[0002] The detection principle of fluorescent sensing materials is based on the different changes in fluorescence intensity caused by light irradiation of different substances, thereby enabling qualitative and quantitative detection of targets. For example, MOF materials can be used to detect targets by interacting with them, causing fluorescence quenching or enhancement. Fluorescent sensing materials are widely used in environmental monitoring, food safety, biomedicine, and other fields. MOF fluorescent sensing materials can be used to detect heavy metal ions and organic pollutants in water.

[0003] MOF materials are typically metal-organic framework materials (Metal-Organic Frameworks). Organic Frameworks (MOFs), also known as metal coordination compound crystal materials, are a type of organic-inorganic hybrid material. MOFs are three-dimensional framework materials with porous structures formed by the self-assembly of organic ligands and metal ions or clusters through coordination bonds. MOFs are widely used in gas adsorption and separation, catalysis, and ion detection. Metal ions are almost ubiquitous in human production and daily life. Although some metals, such as copper, gold, and silver, are widely used in production tools, electronic appliances, currency, and jewelry due to their stable chemical properties and unique luster, like most metals, excessive presence in soil or environmental water bodies can still pose a potential threat to ecosystems and human health. Therefore, effective monitoring of metal ions in water bodies is of great significance for ensuring water environmental safety and promoting pollution control.

[0004] MOFs, as fluorescent sensing materials, possess advantages such as high sensitivity, fast response, and ease of operation. The strong electronic conjugation properties of these materials ensure their efficient fluorescence performance and high degree of electron delocalization, making them a focus of attention in the fields of sensing and imaging. In recent years, fluorene derivatives, anthraquinone derivatives, pyrene derivatives, biphenyl derivatives, styrene derivatives, imidazole derivatives, and polyurethane derivatives have become the main raw materials for fluorescent probes. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a method for detecting Cu. 2+ Ag + Au 3+Fluorescent sensing materials for ions and their preparation methods. This invention synthesizes a zinc complex crystal material using fluorenylcarboxylic acid ligands, fluorenylpyridine ligands, and metallic zinc. Utilizing the different fluorescence emission spectra of this material in response to different metal ions, rapid detection of copper, silver, and gold ions is achieved.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: the fluorescent sensing material is a zinc complex crystal material, and its structural formula is [Zn4(L1)4(L2)2]. n (L1 = 9,9-diethylfluorene-2,7-dicarboxylate, L2 = 2,7-di(4-pyridyl)fluorene, this crystal belongs to the monoclinic crystal system, space group is) P twenty one / n The molecular formula is C 122 H 96 N4O 16 Zn4, with a molecular weight of 2135.50, has unit cell parameters a = 13.8299(7) Å, b = 22.8747(12) Å, and c = 31.8830(16) Å. α = 90°, β = 95.746(2)°, γ = 90°; the asymmetric structural unit of the crystal material includes four Zn(II) ions, four L1 ligands and two L2 ligands ( Figure 1 The Zn(II) ion has two coordination configurations: Zn1 and Zn2 adopt a six-coordinate octahedral configuration, with eight oxygen atoms from the carboxyl groups of four ligands L1, two nitrogen atoms from the pyridine nitrogen of ligand L2, and the other position occupied by Zn–Zn. Figure 2 The distance between Zn1 and Zn2 is 2.968 Å; Zn3 and Zn4 adopt a tetrahedral configuration with four coordinations, with six oxygen atoms from the carboxyl group of ligand L1 and two nitrogen atoms from the pyridyl group of ligand L2; through bridging by ligand L1, a two-dimensional layered structure is formed in the b and c directions. Figure 3 In the two-dimensional layered structure, ligand L2 bridges the layers, forming a three-dimensional network structure with channels. Figure 4 The three-dimensional network structures interweave to form a three-dimensional network structure with four layers of interweaving. Figure 5 The test results show that the prepared zinc complex crystal material is the one used for detecting Cu. 2+ Ag + Au 3+ Fluorescent sensing materials for ions. The present invention also provides a method for preparing the zinc complex crystal material, the method comprising the following steps: A certain amount of ligand L1, ligand L2, and zinc salt were weighed and placed in a reaction vessel, and dissolved in a mixed solution of N,N-dimethylacetamide (DMA), anhydrous ethanol, and distilled water. The reaction vessel containing the mixed solution was sealed and heated at 90–120 °C for 48–72 hours. After cooling to room temperature, colorless and transparent blocky crystals were obtained, which are a zinc complex crystal material, and thus a material used for detecting Cu. 2+ Ag + Au 3+ Fluorescent sensing materials for ions. The zinc salt is zinc nitrate hexahydrate; The molar ratio of the ligands L1, L2 and the zinc salt is 1:1:1; The ligand L1, named 9,9-diethylfluorene-2,7-dicarboxylate, has the abbreviation H2L1 for its unprotonated molecule, and its molecular formula is C2. 19 H 18 O4, with a molecular weight of 310.12, has the following structural formula:

[0007] Equation (I); The ligand L2 is named 2,7-bis(4-pyridyl)fluorene, and its molecular formula is C2. 23 H 16 N2, with a molecular weight of 320.393, has the structural formula shown in formula (II):

[0008] Formula (II); All substances or solvents participating in the reaction are chemically pure.

[0009] This invention also provides the use of the zinc complex crystal material, which can efficiently and rapidly detect Cu. 2+ Ag + Au 3+ Metal ions, this zinc complex crystal material has broad application prospects as a fluorescence sensing material in the detection field.

[0010] Compared with the prior art, the present invention is characterized by: This invention synthesizes a zinc complex crystal material with a unique spatial structure using a solvothermal method by employing a mixed ligand with a special structure. This crystal material, as a fluorescence sensing material, exhibits specific fluorescence emission properties, particularly for Cu... 2 + Ag + Au 3+ Metal ions exhibit high sensitivity and selective response.

[0011] The ligands L1 and L2 used in this invention both possess a fluorene-based large conjugated unit structure, are fluorene derivatives, have rigid planes, and contain a basic unit composed of two benzene rings and a five-membered ring. They are highly stable fluorescent materials with strong fluorescence emission. Their unique spatial structure determines the high stability, specific fluorescence properties, and unique fluorescence response to specific metal ions of the prepared crystal material, making it a promising candidate for use as a fluorescence sensing and detection material.

[0012] In particular, compared with other similar ligands, ligand L2 has two active hydrogens at the 9 position instead of large groups such as methyl or ethyl groups. This feature, on the one hand, allows the MOF materials formed to have large pores, which can accommodate large metal ions or small organic molecules, or form a multi-layered interpenetrating network structure, giving them special physicochemical properties. On the other hand, the two active hydrogens can form special hydrogen bonds or intermolecular forces with ions or molecules in the crystal pores, thus giving the MOF materials formed to special physicochemical properties. Attached Figure Description

[0013] Figure 1 This is the basic structural unit of the fluorescent sensing material described in this invention; Figure 2 This is a coordination environment diagram of Zn(II) ions in the fluorescent sensing material described in this invention, with hydrogen atoms omitted; Figure 3 The two-dimensional structure of the fluorescent sensing material described in this invention along the b and c directions is shown, with hydrogen atoms omitted; Figure 4 The fluorescent sensing material described in this invention has a three-dimensional network structure along the a, b, and c directions, in which hydrogen atoms are ignored; Figure 5 The fluorescent sensing material described in this invention has a 4-fold interpenetrating three-dimensional network structure in which hydrogen atoms are ignored; Figure 6 Thermogravimetric spectrum of the fluorescent sensing material described in this invention; Figure 7 The fluorescence response spectra of the fluorescent sensing material described in this invention in the presence of different metal ions are shown. Figure 8 This is a test image showing the anti-interference performance of the fluorescent sensing material described in this invention. Figure 8 (a) Figure 8 (b) Figure 8 (c) respectively correspond to Ag + Cu 2+ Au 3+A comparison of fluorescence intensity of fluorescent sensing materials under different cation interference conditions with and without the presence of K+ ions. The test conditions were that the fluorescent sensing materials were prepared as a suspension, and the interfering ion was K+. + Na + Co² + , Ba² + Ni² + Zn² + Cd² + Mg² + Pb² + Al 3+ , Cr 3+ Fe 3+ Each concentration is 10 -4 M; Figure 9 For testing Ag in the fluorescent sensing material described in this invention + Cu 2+ Au 3+ Sensitivity graph of metal ions; Figure 9 (a) Figure 9 (c) Figure 9 (e) shows the Ag content of the fluorescent sensing material at different concentrations. + Cu 2+ Au 3+ fluorescence intensity spectrum, Figure 9 (b) Figure 9 (d) Figure 9 (f) shows the test results of Ag at different concentrations of the fluorescent sensing material. + Cu 2 + Au 3+ The linear fitting curve of fluorescence intensity; Ksv is the slope of the fitting curve. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the embodiments.

[0015] Example 1: Weigh out 2.9 mg of Zn(NO3)2·6H2O (0.01 mmol), 3.1 mg of ligand L1 (0.01 mmol), and 3.2 mg of ligand L2 (0.01 mmol), and place them separately in a reaction vessel. Dissolve them in a mixed solution consisting of 1.5 mL of solvent N,N-dimethylacetamide (DMA), 1.0 mL of anhydrous ethanol, and 1.0 mL of distilled water, with a solvent volume ratio of 1.5:1:1. Seal the reaction vessel containing the solution and heat it at 90 °C for 72 hours. Then cool it to room temperature to obtain colorless and transparent blocky crystals. Example 2: Weigh out 5.9 mg of Zn(NO3)2·6H2O (0.02 mmol), 6.2 mg of ligand L1 (0.02 mmol), and 6.4 mg of ligand L2 (0.02 mmol), and place them separately in a reaction vessel. Dissolve them in a mixed solution consisting of 1.5 mL of N,N-dimethylacetamide (DMA), 1.0 mL of anhydrous ethanol, and 1.0 mL of distilled water. Seal the reaction vessel containing the solution and heat it at 120 °C for 48 hours. Then cool it to room temperature to obtain colorless and transparent blocky crystals.

[0016] Example 3: Weigh out 8.9 mg of Zn(NO3)2·6H2O (0.03 mmol), 9.3 mg of ligand L1 (0.03 mmol), and 9.6 mg of ligand L2 (0.03 mmol), and place them separately in a reaction vessel. Dissolve them in a mixed solution consisting of 3.0 mL of N,N-dimethylacetamide (DMA), 2.0 mL of anhydrous ethanol, and 2.0 mL of distilled water. Seal the reaction vessel containing the solution and heat it at 105 °C for 60 hours. Then cool it to room temperature to obtain colorless and transparent blocky crystals.

[0017] The colorless, transparent, blocky crystals prepared in Example 1 were subjected to single-crystal X-ray diffraction analysis. Crystals of suitable size and regular shape were selected at room temperature and fixed to the test probe with epoxy resin. The test probe was then placed on a Rigaku Oxford XtaLAB PRO diffractometer, and the sample was tested using monochromatic MoKα radiation (λ = 0.71073 Å). Data was acquired using Apex II software, diffraction points were screened, the lattice type was determined, and absorption correction and data reconstruction were performed. The crystal structure was directly solved using the ShelXS program, and anisotropic refinement was performed using ShelXL. F 2 The structure was refined and corrected using the full matrix least squares method. The coordinates of non-hydrogen atoms were gradually determined and anisotropically refined through Fourier peak synthesis. Hydrogen atoms were obtained through theoretical hydrogenation. All hydrogen atoms underwent isotropic refinement, and a CIF file was obtained. X-ray single-crystal diffraction analysis showed that the prepared zinc complex crystal material has the structural formula [Zn2(L1)4(L2)2]. n This crystal belongs to the monoclinic crystal system, space group 1. P twenty one / n The molecular formula is C 122 H 96 N4O 16Zn4, with a molecular weight of 2135.50, has unit cell parameters a = 13.8299(7) Å, b = 22.8747(12) Å, and c = 31.8830(16) Å. α =90°, β = 95.746(2)°, γ = 90°; the asymmetric structural unit of the crystal material includes four Zn(II) ions, four L1 ligands and two L2 ligands ( Figure 1 The Zn(II) ion has two coordination configurations: Zn1 and Zn2 adopt a six-coordinate octahedral configuration, with eight oxygen atoms from the carboxyl groups of four ligands L1, two nitrogen atoms from the pyridine nitrogen of ligand L2, and the other position occupied by Zn–Zn. Figure 2 The distance between Zn1 and Zn2 is 2.968 Å; Zn3 and Zn4 adopt a tetrahedral configuration with four coordinations, with six oxygen atoms from the carboxyl group of ligand L1 and two nitrogen atoms from the pyridyl group of ligand L2; the crystal material forms a two-dimensional layered structure in the b and c directions through bridging by ligand L1. Figure 3 The two-dimensional layered structure is bridged between layers by ligand L2, forming a three-dimensional network structure with channels. Figure 4 The three-dimensional network structures interweave to form a three-dimensional network structure with four layers of interweaving. Figure 5 The test results showed that the prepared zinc complex crystals were the aforementioned method for detecting Cu. 2+ Ag + Au 3+ Fluorescent sensing materials for ions.

[0018] The zinc complex crystal material prepared in Example 1 above was subjected to thermogravimetric analysis. Figure 6 The results showed that the framework of the prepared crystal material remained stable at around 420 °C, indicating that the crystal has good thermal stability.

[0019] To evaluate the detection effect of the crystal material prepared in Example 1 on metal ions in water, 5 mg of the crystal was dissolved in 50 mL of deionized water to obtain a suspension with a concentration of 100 μM. Subsequently, 200 μL of various metal cation solutions M(NO3)n (Mn) were added. n+ = K + Na + Ag + Co² + , Ba² + Cu² + Ni² + Zn² + Cd² + Mg²+ Pb² + Al³ + Au 3+ The concentrations were all 10. -4 M) was added to 1800 μL of the crystal material suspension, and then fluorescence analysis was performed, recording the fluorescence spectrum. The test results showed that Ag was present in the prepared crystal material suspension. + Cu 2+ Au 3+ The different fluorescence intensities observed when ions were present indicate that the prepared material reacts with Ag. + Cu 2+ Au 3+ Ions have specific response properties ( Figure 7 Anti-interference test () Figure 8 In real aquatic environments, multiple metal ions coexist, necessitating interference resistance testing to evaluate the selective ion detection of the compound. The interfering ions were K+, Na+, Co²+, Ba²+, Ni²+, Zn²+, Cd²+, Mg²+, Pb²+, and Al³+ (all with a concentration of 10⁻⁴ M). The interference performance of the compound against 10 other ions was tested. The results show that the crystal prepared in Example 1 exhibits strong selectivity for Ag+, Cu²+, and Au³+ as a fluorescent sensing material, demonstrating its potential application in detecting Ag+, Cu²+, and Au³+ in complex environments.

[0020] Sensitivity test ( Figure 9 Because this fluorescent sensing material exhibits significant selectivity for Ag+, Cu2+, and Au3+, we further analyzed the zinc complex crystal material prepared in Example 1 using quantitative fluorescence titration to evaluate its sensitivity as a sensor. With increasing concentrations of Ag+, Cu2+, and Au3+, respectively, the fluorescence intensity decreased significantly. Within a specific concentration range, the fluorescence intensity showed a good linear relationship with the ion concentration. The detection limits for Ag+, Cu2+, and Au3+ were calculated to be 2.51 μM, 2.15 μM, and 2.41 μM, respectively. These results confirm the high sensitivity of this crystal material as a fluorescent sensing material for the detection of Ag+, Cu2+, and Au3+.

Claims

1. A fluorescent sensing material for detecting Cu 2+ , Ag + , Au 3+ ions, characterized in that, The fluorescent sensing material is a zinc complex crystal material with the structural formula [Zn₄(L₁)₄(L₂)₂]. n This crystal belongs to the monoclinic crystal system, space group 1. P twenty one / n The molecular formula is C 122 H 96 N4O 16 Zn4, with a molecular weight of 2135.50, has unit cell parameters a = 13.8299(7) Å, b = 22.8747(12) Å, and c = 31.8830(16) Å. α = 90°, β = 95.746(2)°, γ = 90°; the asymmetric structural unit of the crystal material includes four Zn(II) ions, four L1 ligands and two L2 ligands; the Zn(II) ions have two coordination configurations, Zn1 and Zn2 adopt a six-coordinate octahedral configuration, with eight oxygen atoms from the carboxyl groups of the four L1 ligands, two nitrogen atoms from the pyridine nitrogen of the L2 ligand, and the other position is occupied by Zn–Zn, with a distance of 2.968 Å between Zn1 and Zn2; Zn3 and Zn4 adopt a four-coordinate tetrahedral configuration, with six oxygen atoms from the carboxyl groups of the L1 ligands and two nitrogen atoms from the pyridine groups of the L2 ligand; The crystalline material forms a two-dimensional layered structure in the b and c directions through bridging by ligand L1; the layers of the two-dimensional layered structure are bridged by ligand L2 to form a three-dimensional network structure with channels; the three-dimensional network structures interpenetrate with each other to finally form a three-dimensional network structure with 4-fold interpenetration. The structural formula is [Zn4(L1)4(L2)2]. n The ligand L1 is named 9,9-diethylfluorene-2,7-dicarboxylate, and its unprotonated molecule is abbreviated as H2L1. The molecular formula of H2L1 is C2. 19 H 18 O4, with a molecular weight of 310.12, has the following structural formula: Equation (I); The structural formula is [Zn4(L1)4(L2)2]. n The middle ligand L2 is named 2,7-bis(4-pyridyl)fluorene, and its molecular formula is C2. 23 H 16 N2, with a molecular weight of 320.393, has the structural formula shown in formula (II): Equation (II).

2. A method for detecting Cu as described in claim 1 2+ Ag + Au 3+ A method for preparing fluorescent sensing materials for ions, characterized in that, The preparation method includes the following steps: A certain amount of ligand L1, ligand L2, and zinc salt were weighed and placed in a reaction vessel, and dissolved in a mixed solution of N,N-dimethylacetamide, anhydrous ethanol, and distilled water. The reaction vessel containing the mixed solution was sealed and heated at 90–120 °C for 48–72 hours. After cooling to room temperature, colorless and transparent blocky crystals were obtained. These crystals are a zinc complex crystal material, which is used to detect Cu. 2+ Ag + Au 3+ Fluorescent sensing materials for ions; The zinc salt is zinc nitrate hexahydrate; The molar ratio of ligand L1, ligand L2 and zinc salt is 1:1:

1.

3. Use of the fluorescent sensing material for detecting Cu2+, Ag+, Au3+ ions according to claim 1, characterized in that, The fluorescent sensing material has the use of detecting metal ions Ag + , Cu 2+ , Au 3+ .

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