Praseodymium-based complex crystal material, preparation method thereof and fluorescent recognition application thereof

Abstract

This invention belongs to the technical field of crystalline materials, and discloses a praseodymium-based complex crystalline material, its preparation method, and its fluorescence recognition application, with the chemical formula {[Pr(L 1.5 The compound is 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfonyl)diethyl)benzoic acid. The preparation method involves dissolving Pr(NO3)3·6H2O, H2L, and the auxiliary uncoordinated ligand 1,4-bis(imidazol-1-yl)benzene in a DMF / ethanol / water mixed solvent, reacting at 90°C for 3 days, and then cooling to obtain plate-like crystals. This material is effective against Fe... 3+ It exhibits highly selective and sensitive fluorescence quenching response with a quenching rate of 99.8%; it can specifically recognize ethoxyquinoline (fluorescence enhancement) and 2,4-dichlorophenoxyacetic acid (fluorescence quenching); it can specifically recognize the antibiotic oxytetracycline with a fluorescence quenching rate exceeding 99%.

Description

Technical Field

[0001] This invention belongs to the technical field of crystalline materials, specifically metal-organic coordination polymer materials, and more specifically, a praseodymium complex crystalline material, its preparation method, and its fluorescence recognition application. Background Technology

[0002] Adequate iron intake can help prevent certain diseases, such as heart disease, Parkinson's disease, and Alzheimer's disease. However, when its concentration exceeds a certain safe threshold, it will have negative effects on the organism, triggering a series of serious physiological disorders. For example, excessive iron... 3+ It may lead to insomnia and affect the body's immune function, causing it to decline. More seriously, long-term accumulation of Fe... 3+ It may damage the liver and even lead to serious diseases such as cirrhosis. However, with the rapid development of industry, Fe... 3+ It has become a significant source of inorganic pollutants. For example, in industry, large amounts of Fe are present. 3+ Wastewater is directly discharged into rivers, polluting the environment; the use of iron-containing machinery or chemical additives in food preparation and processing can lead to excessive iron intake. 3+ Introducing Fe into food can cause a series of physiological toxic effects on the human body, posing a threat to human health. Due to Fe... 3+ The importance and impact of Fe in biological and environmental systems, therefore, for the sake of human health, the environmental protection of Fe... 3+ Concentration detection is crucial. Traditional detection methods include electrochemical methods, liquid chromatography, mass spectrometry, and atomic emission spectrophotometry. However, these methods typically suffer from drawbacks such as expensive instruments, complex and time-consuming operations, high costs, inability to provide real-time data feedback, and difficulty in meeting the needs of intelligent control. Therefore, developing highly sensitive and rapid specific detection methods is of significant research importance.

[0003] With the rapid development of technology, environmental protection and quality of life have gradually become the focus of people's attention. Against this backdrop, developing a low-cost, portable, highly sensitive metal ion detection sensor that meets people's needs for accurate detection is particularly important. In recent years, metal ion sensors made of various materials have been developed. However, new metal ion sensors that can be widely used in actual production and daily life are still very scarce. This is mainly because the sensitivity and accuracy of sensors need further improvement; therefore, it is necessary to develop more reusable and easy-to-operate metal ion detection sensors. Among them, fluorescence recognition technology is a commonly used method for metal ion identification, with advantages such as fast analysis speed and low cost. Luminescent materials with fluorescence recognition properties show broad prospects in the field of sensing.

[0004] To address this bottleneck, metal-organic coordination polymers (CPs) have shown unique potential. Due to the designability and controllability of their structures, coordination compounds have become a hot topic in materials research in recent years. The structure of coordination compounds can be modulated not only by changing the metal cations and organic ligands, but also by altering the synthesis conditions. Therefore, coordination polymers have enormous potential application value in the field of fluorescence recognition. Summary of the Invention

[0005] One objective of this invention is to provide a praseodymium-based complex crystal material, wherein the chemical formula of the praseodymium-based complex crystal material is {[Pr(L 1.5 [(DMF)2(H2O)]·2DMF} (named R-Pr), with the ligand 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfonated diethyl)dibenzoic acid (H2L), has the following chemical structure: .

[0006] Furthermore, from the perspective of structural connection construction, the praseodymium complex crystal material is a two-dimensional layered structure.

[0007] The crystal structure belongs to the triclinic crystal system. P Space group -1, cell parameters are: a = 12.5838(3) Å, b = 14.3012(4) Å, c = 17.2778(5) Å, α =66.9140(10), β =70.7060(10), γ =89.9280(10).

[0008] Furthermore, in the asymmetric structural unit of R-Pr, the coordination number of Pr(III) is 9. Pr(III) is coordinated with nine O atoms, six of which are O1, O2, O3, O5. i O6 i and O6 ii The Pr(III) atoms originate from four different H2L ligands, with two additional O atoms (O8 and O9) from a coordinated DMF molecule and one O atom (O7) from a coordinated water molecule. Ignoring the coordination solvent molecules, two adjacent Pr(III) atoms are linked together by the O6 atoms in their two carboxyl groups to form a Pr2L6 secondary structural unit, which simultaneously connects six L atoms. 2- Ligands, each L 2- Then connect the two Pr(III); therefore, in space, Pr(III) and L 2- The ligands form a 2D layered structure.

[0009] The present invention also provides a method for preparing praseodymium complex crystal materials, comprising the following steps: Pr(NO3)3·6H2O, the main ligand H2L, and the auxiliary non-coordinate ligand 1,4-bis(imidazol-1-yl)benzenebib were weighed and added to a mixed solvent of DMF / ethanol / water. The mixture was sealed and heated to react. After the reaction was completed, the system was allowed to slowly cool to room temperature, and yellow flaky crystals were obtained.

[0010] Furthermore, the molar ratio of Pr(NO3)3·6H2O, the main ligand H2L, and bib is 1:1:0.5.

[0011] Furthermore, the volume ratio of DMF / ethanol / water is 5:2:1, and the amount of mixed solvent added is limited to 0.1 mmol corresponding to 8 ml of mixed solvent.

[0012] Furthermore, the heating reaction was carried out at 90°C for 3 days.

[0013] This invention also provides the praseodymium complex crystal material in Fe 3+ Applications in recognition.

[0014] The present invention also provides the application of the praseodymium complex crystal material in the recognition of ethoxyquinoline and 2,4-dichlorophenoxyacetic acid.

[0015] The present invention also provides the application of the praseodymium complex crystal material in the identification of oxytetracycline.

[0016] Beneficial technical effects of the present invention: The praseodymium coordination polymer R-Pr synthesized in this invention possesses a novel two-dimensional layered structure, in which the coordination number of Pr(III) is 9, and the structure is linked by strong coordination bonds. Thermogravimetric analysis shows that the material is structurally stable below 380°C, exhibiting good thermal stability. Furthermore, its structure remains intact after immersion in solvents such as DMF, water, and 1,4-dioxane, demonstrating excellent chemical stability, which lays the foundation for its application in complex environments.

[0017] R-Pr in ethanol solution for Fe 3+ It exhibits an extremely sensitive and specific fluorescence "turn-off" response. The fluorescence quenching rate is as high as 99.8%, and the fluorescence changes from bright to almost completely quenched under 254 nm ultraviolet light visible to the naked eye. Logarithmic concentration-response curves established through fluorescence titration experiments show that it exhibits a high response to Fe... 3+ It has a wide detection range and high sensitivity. Anti-interference experiments demonstrate that even in the presence of interference from various other common metal ions (including rare earth ions), R-Pr effectively detects Fe. 3+ Its recognition capability remains unaffected, demonstrating excellent anti-interference performance and practical application potential.

[0018] In addition to detecting Fe 3+ Furthermore, R-Pr extends its fluorescence recognition capabilities to the fields of food additives and antibiotics, demonstrating its multi-purpose advantage. Among the 16 food additives tested, R-Pr efficiently identified ethoxyquinoline (EQ, showing significant fluorescence enhancement and red shift) and 2,4-dichlorophenoxyacetic acid (2,4-D, showing efficient fluorescence quenching), while exhibiting weaker responses to other additives, demonstrating good selectivity. Among the 17 antibiotics tested, R-Pr showed a near-specific and highly efficient fluorescence quenching response (quenching rate >99%) to oxytetracycline (OTC), while its recognition effect on other antibiotics was not significant, showing promising application prospects in the detection of specific antibiotics.

[0019] The preparation method of this material is the classic hydrothermal / solvothermal method. The raw materials are readily available, the steps are simple, the conditions are mild (heating at 90℃), and the produced crystals are of good quality, which is conducive to large-scale synthesis and practical applications. Attached Figure Description

[0020] Figure 1 The coordination environment diagram of Pr(III) in R-Pr of this invention (symmetric code: i x, -1+y, 1+z. ii -x, 1-y, 1-z. iii 1-x, 1-y, 2-z.

[0021] Figure 2 This refers to the Pr2L6 secondary structure unit present in the R-Pr of this invention.

[0022] Figure 3 This refers to the 2D layered structure present in R-Pr of the present invention.

[0023] Figure 4 This is the thermogravimetric analysis diagram of R-Pr in this invention.

[0024] Figure 5 This is the infrared spectrum of R-Pr of the present invention.

[0025] Figure 6 The powder diffraction patterns of the R-Pr of this invention after soaking in different solutions for 1 hour are shown.

[0026] Figure 7 The solid-state fluorescence emission spectra of R-Pr and H2L in this invention are shown.

[0027] Figure 8 This is the fluorescence emission spectrum of R-Pr in common solvents according to the present invention.

[0028] Figure 9 This is a bar chart showing the relative intensity of the strongest emission peak of R-Pr in common solvents according to the present invention.

[0029] Figure 10 The fluorescence emission spectra of R-Pr in 11 non-rare earth metal salt solutions (metal ion concentration 10) are shown below. -3 (mmol / mL).

[0030] Figure 11 This is a bar chart showing the intensity of the strongest emission peak of R-Pr at 315 nm in 11 non-rare earth metal salt solutions (metal ion concentration 10). -3 (mmol / mL).

[0031] Figure 12 The fluorescence emission spectra of R-Pr in 13 rare earth salt solutions (metal ion concentration 10) are shown below. -3 (mmol / mL).

[0032] Figure 13 This is a bar chart showing the intensity of the strongest emission peak at 315 nm for R-Pr in 13 rare earth salt solutions according to the present invention.

[0033] Figure 14 For the R-Pr blank and Fe addition of this invention 3+ The image was then taken under ultraviolet light at a wavelength of 254 nm.

[0034] Figure 15 For the R-Pr blank and Tb addition of this invention 3+ The image was then taken under ultraviolet light at a wavelength of 254 nm.

[0035] Figure 16 The present invention provides R-Pr with different Fe concentrations. 3+ Fluorescence emission spectrum of the solution.

[0036] Figure 17 Fe for R-Pr of the present invention 3+ The response curve of concentration logarithm versus fluorescence enhancement rate.

[0037] Figure 18 The present invention provides R-Pr for Fe 3+ Bar graph of anti-interference experiment.

[0038] Figure 19 For the present invention R-Pr at 10 -3 Fluorescence emission spectrum of mmol / mL food additive solution.

[0039] Figure 20 These are images of the R-Pr blank and the R-Pr after the addition of ethoxyquinoline under ultraviolet light at a wavelength of 254 nm.

[0040] Figure 21Images of the R-Pr blank and the image after the addition of 2,4-dichlorophenoxyacetic acid under ultraviolet light at a wavelength of 254 nm.

[0041] Figure 22 For the present invention R-Pr at 10 -3 Fluorescence emission spectrum of antibiotic solution at mmol / mL.

[0042] Figure 23 Images of the R-Pr blank and the image after the addition of oxytetracycline under ultraviolet light at a wavelength of 254 nm. Detailed Implementation

[0043] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0044] Example 1 Pr(NO3)3·6H2O (43 mg, 0.10 mmol), the auxiliary uncoordinated ligand bib ligand (10.0 mg, 0.05 mmol), and H2L (20.0 mg, 0.10 mmol) were mixed and then added to DMF / EtOH / H2O (5:2:1, V / V / V) (8.0 mL). The mixture was heated at 90 °C for three days under sealed conditions. After cooling to room temperature, yellow flaky crystals of R-Pr were obtained in 45% yield.

[0045] (1) Determination of crystal structure: Crystals with good growth and few cracks were selected and adhered to thinned glass wires. R-Pr diffraction data were collected at room temperature under Mo-Kα radiation (λ=0.71073Å) using a Bruker APEX-II CCD single-crystal diffractometer. The structure was solved using the XS structure solver and optimized using the SHELXTL software package using the least squares method. Anisotropic shift parameters of non-hydrogen atoms were provided during the improvement process. The positions of hydrogen atoms on the ligands were determined using theoretical hydrogenation. Crystallographic data are shown in Table 1.

[0046] Table 1 Crystallographic data of R-Pr materials

[0047] The structural diagram of the complex R-Pr is as follows: Figure 1-3 As shown, Figure 1 This indicates the coordination environment of Pr(III). In the asymmetric structural unit of R-Pr, the coordination number of Pr(III) is 9. Pr(III) is coordinated with nine O atoms, six of which are O1, O2, O3, O5. i O6 i and O6 iiThe two O atoms (O8 and O9) come from different H2L ligands, and the other two O atoms (O7) come from a coordinated DMF molecule, while one O atom (O8) comes from a coordinated water molecule. Without considering the coordinating solvent molecule, two adjacent Pr(III) groups are linked together by the O6 atom in their two carboxyl groups to form a Pr2L6 secondary structural unit. Figure 2 The secondary structural unit connects six L at the same time. 2- Ligands, each L 2- Then connect the two Pr(III); in space, Pr(III) and L 2- Ligands form 2D layered structures ( Figure 3 ).

[0048] Generally, coordination polymers with good thermal stability are more suitable as recognition materials and are easier to apply in high-temperature and complex environments. The thermal degradation process of coordination polymers is often accompanied by the breaking of coordination bonds and the combustion of ligands; therefore, the thermal stability of coordination polymers is generally related to the strength of the coordination bonds and the number of nodal ligands. Common Pr 3+ The coordination numbers are 7, 8, and 9 in the R-Pr complexes of this invention. 3+ The coordination number of each is 9, with one coordinated water molecule, two coordinated DMF molecules, and two free DMF molecules in R-Pr. The crystal material of this invention is novel; in R-Pr, two adjacent Pr(III) are connected by two O6 atoms, and each L... 2- The ligand connects two Pr(III), L 2- The ligands and Pr(III) are interconnected to form a 2D layered structure. Thermogravimetric analysis shows that (… Figure 4 R-Pr loses approximately 12.32% of its weight from room temperature to 97°C, which is consistent with the weight loss of two free DMF molecules (theoretical value 12.73%). Within the temperature range of 97°C to 380°C, the weight loss is 14.03%, which matches the weight loss of coordinated water and coordinated DMF (theoretical value 14.28%). The subsequent significant weight loss indicates framework collapse. The fact that the material remains structurally stable up to 380°C demonstrates its good thermal stability, which is beneficial for the widespread application of R-Pr.

[0049] Figure 5 The Fourier transform infrared spectrum shows that, using a Shimadzu FTIR-8400S spectrometer, the wavelength range of 4000-500 cm⁻¹ is [missing information]. -1 FT-IR spectra of R-Pr were collected within the range of [specific range], and the corresponding characteristic absorption peaks were characterized. Major absorption peak (KBr, cm⁻¹) -1The major absorption peaks were: 3421.68 (w), 2915.04 (w), 1660.33 (m), 1587.01 (m), 1568.84 (s), 1542.75 (m), 1431.98 (w), 1405.23 (m), 1340.57 (w), 1262.94 (w), 1059.11 (m), 779.76 (w), 744.28 (m), 654.99 (w), 570.58 (w), and 490.96 (w). No -COOH was observed at 1710 cm⁻¹. -1 The strong characteristic peak near the L-axis indicates that the carboxyl group has lost a proton and participated in coordination, confirming the interaction between the metal ion and the ligand L. 2- Coordination, which is consistent with the results of X-ray single-crystal diffraction data analysis.

[0050] Figure 6 The images show the powder diffraction patterns of the R-Pr complex after immersion in different solutions for 1 hour. The results show that after immersion in N,N-dimethylformamide (DMF), water (H2O), and 1,4-dioxane for 1 hour, the XRD spectra of the R-Pr complex correspond well with the simulated values, indicating that the R-Pr complex has good stability in N,N-dimethylformamide (DMF), water (H2O), and 1,4-dioxane.

[0051] Before conducting the fluorescence recognition experiment, solid-state fluorescence tests were first performed on the complexes R-Pr and H2L. Figure 7 When H₂L is excited at a wavelength of 290 nm, its strongest emission peak appears at 398 nm. For the complex R-Pr, at an excitation wavelength of 250 nm, the strongest emission peak is located at 378 nm. Compared with H₂L, the strongest emission peak of R-Pr exhibits a slight blue shift, and this shift in the strongest emission peak is related to the coordination of the ligand and the metal ion. The fluorescence of the complex mainly originates from the π→π transition of the ligand. ＊ or n→π ＊ Transition luminescence and ligand-to-metal ion charge transfer (LMCT) luminescence are also observed. Furthermore, after complex formation, the coordination bonds between the ligand and the metal ion restrict the vibration and rotation of the ligand molecule, reducing vibrational relaxation. This allows the excited-state molecule to emit photons at higher energies, resulting in a blue shift.

[0052] At room temperature, a powder sample (3 mg) of complex R-Pr was immersed in 3 mL of different organic solvents: anhydrous methanol (MeOH), anhydrous ethanol (EtOH), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), water (H2O), 1,4-dioxane, N,N-diethylformamide, and acetonitrile (CH3CN). The above mixed solutions were then sonicated for 15 min to obtain a suspension for fluorescence detection. At an excitation wavelength of 250 nm, the fluorescence spectra of R-Pr in different solvents showed that, compared with solid-state fluorescence, its strongest emission peak shifted (the strongest peak was at 315 nm). The fluorescence intensity varied greatly in different solvents, and the intensity of the strongest emission peak decreased in the following order: MeOH > EtOH > 1,4-dioxane > CH3CN > H2O > DMSO > NMP > DMA > DMF > DEF. Figure 8 The above phenomena can be attributed to the interaction between the complex and solvents with different polarities, due to the different intermolecular interactions caused by the difference in solvent polarity. Specifically, when the complex is added to DMA, DMF, or DEF solvents, fluorescence quenching occurs. The quenching may be caused by photoinduced electron transfer in the amide molecules. All three amide solvents are strongly polar aprotic solvents. The amide carbonyl group (C=O) is a strong electron-withdrawing group with low-energy empty orbitals. Excited electrons from the carboxylic acid ligand can jump to these low-energy empty orbitals, with the energy mainly dissipated as heat, thus weakening luminescence.

[0053] Figure 9 This is a bar chart showing the relative intensity of the strongest emission peak of R-Pr in common solvents. The peak intensity is highest in MeOH, and fluorescence quenching occurs in DMA, DMF, and DEF solvents. Using ethanol as the solvent selected in this experiment as a reference, the fluorescence quenching rates in DMA, DMF, and DEF solvents are 99.3%, 99.7%, and 99.7%, respectively.

[0054] In this invention, ethanol is chosen as the solvent for fluorescence recognition. The choice of ethanol as the detection solvent is based on the following advantages: (1) Environmental friendliness: low toxicity risk, in line with green chemistry standards; (2) Practical adaptability: it can directly detect complex matrices such as environmental water samples and industrial wastewater, and has good solubility and adjustable polarity characteristics.

[0055] R-Pr was added to a 0.001 mmol / mL metal salt solution prepared in ethanol. These metal salts were 11 non-rare earth metal salts (NaNO3, KNO3, Al(NO3)3, Cr(NO3)3, Fe(NO3)3, Co(NO3)2, Ni(NO3)2, Cu(NO3)2, Pb(NO3)2, AgNO3, Cd(NO3)2) and 13 rare earth metal salts (Y(NO3)3, La(NO3)3, Ce(NO3)3, Pr(NO3)3, Nd(NO3)3, Sm(NO3)3, Eu(NO3)3, Gd(NO3)3, Tb(NO3)3, Dy(NO3)3, Er(NO3)3, Yb(NO3)3, Lu(NO3)3). At an excitation wavelength of 250 nm, compared with the absence of metal salt, the position of the strongest emission peak remained unchanged, but the fluorescence intensity changed significantly. The order of intensity changes after adding non-rare earth salts is as follows: K + >Blank>Na + >Cd 2+ >Cr 3+ >Pb 2+ >Co 2+ >Ag + >Ni 2+ >Al 3+ >Cu 2+ >Fe 3+ ( Figure 10 It is worth noting that the addition of Fe(NO3)3 solution caused fluorescence quenching. (Compared to not adding Fe...) 3+ Compared with the blank sample, the quenching rate was 99.8%. Therefore, R-Pr has a quenching rate of 99.8% for Fe. 3+ It exhibits fluorescent recognition. This indicates that the complex R-Pr has a fluorescent recognition effect on Fe. 3+ It exhibits strong fluorescence recognition effect and has the potential to be used as Fe 3+ The potential of fluorescence sensors.

[0056] Figure 11 This is a bar chart showing the intensity of the strongest emission peak of R-Pr in 11 non-rare earth metal salt solutions according to the present invention. Metal ion concentration 10... -3 mmol / mL, with the strongest emission peak at 315 nm. Intensity order: K + >Blank>Na + >Cd 2+ >Cr 3+ >Pb 2+ >Co 2+ Ag + Ni 2+ >Al 3+ >Cu 2+ >Fe 3+ .

[0057] Figure 12 This is the fluorescence emission spectrum of R-Pr in 13 rare earth salt solutions according to the present invention. R-Pr was added to 13 10... -3 In mmol / mL rare earth salt solutions, the fluorescence emission spectra are similar in shape, with the strongest emission peak around 315 nm, but the fluorescence intensities differ. Adding Tb... 3+ Afterwards, the intensity of the strongest emission peak significantly increased, being twice that of the blank sample. Compared with the blank sample, except for Tb... 3+ Furthermore, the strongest emission peaks were weakened upon the addition of other rare earth ions. Specifically, when Lu... 3+ After addition, the strongest peak weakened most significantly, decreasing to 74.7% of the intensity of the blank sample.

[0058] Figure 13 This is a bar graph showing the intensity of the strongest emission peak of R-Pr in 13 rare earth salt solutions according to the present invention. Metal ion concentration 10... -3 mmol / mL, with the strongest emission peak at 315 nm. Intensity order: Tb 3+ >Blank>La 3+ >Er 3+ >Y 3+ >Pr 3+ Eu 3+ >Ce 3+ >Yb 3+ >Dy 3+ >Gd 3+ >Nd 3+ >Sm 3+ >Lu 3+ .

[0059] Figure 14 For the R-Pr blank and Fe addition of this invention 3+ The image was then taken under ultraviolet light at a wavelength of 254 nm. Figure 15 For the R-Pr blank and Tb addition of this invention 3+ The image was then taken under UV light at a wavelength of 254 nm. (The solution fluorescence was extremely weak under the same 254 nm UV light.) Tb was added. 3+ The solution then emitted a bright green fluorescence after the addition of Fe. 3+ Then, the fluorescence quenched.

[0060] Given R-Pr on Fe 3+ It exhibits significant fluorescence response characteristics, and its quantitative analysis was performed using a fluorescence titration experiment. Different concentrations of Fe were added to the R-Pr aqueous system. 3+ Subsequently, the fluorescence intensity at a specific characteristic wavelength of 315 nm showed a significant change, and with Fe 3+ The changes in concentration exhibit regular fluctuations, which can be used to assess Fe. 3+The effect of concentration on the emission intensity of R-Pr fluorescence sensing. A series of Fe concentrations were prepared using ethanol as a solvent. 3+ Solution (concentration gradient: 10) -6 M~10 -3 M), and a detection system was constructed by mixing with the complex. The fluorescence intensity at characteristic wavelengths was measured, and the enhancement rate was calculated using the formula: Enhancement rate (%) = (I / I0-1)×100%. Where I0 is the fluorescence intensity of the blank group (ethanol phase system containing only R-Pr), and I is the fluorescence intensity of the sample group (R-Pr + Fe). 3+ Fluorescence intensity. Figure 16 For the present invention R-Pr at 10 -6 M, 10 -5 M, 10 -4 M, 10 -3 M of Fe 3+ Fluorescence emission spectrum of the solution. With Fe 3+ Concentration from 10 -6 M rises to 10 -3 M, fluorescence intensity gradually decreases. Fe 3+ The detection system exhibits a unique concentration dependence, which is a key characteristic of its specific interaction with the probe. Specifically, when Fe... 3+ At lower concentrations (approximately -6 to -5 logarithmic values), the fluorescence intensity of the system gradually decreases, while the quenching rate gradually increases. When Fe... 3+ The concentration exceeds a specific threshold (lgC = -5.0, corresponding to a concentration of 10). -5 After M), the fluorescence signal transforms into a strong quenching effect, with the quenching rate increasing exponentially with increasing concentration, reaching lgC = -3.0 (corresponding to a concentration of 10). -3 The fluorescence quenching rate peaks at M) at 99.95%. Therefore, with Fe... 3+ Concentration from extremely low levels (e.g., 10) -6 As M gradually increases, the fluorescence intensity continuously decreases, reaching a critical concentration point (10). -5 After M), if the concentration continues to increase, the fluorescence intensity continues to decrease. -4 When the concentration after M is further increased, the change in fluorescence intensity is small, and the quenching rate exceeds 98.6%. At a concentration of 10... -3 At time M, the peak fluorescence quenching rate was 99.95% ( Figure 17 ).

[0061] Good anti-interference performance is an important prerequisite for the practical application of fluorescence sensing materials, therefore, for Fe 3+ Anti-interference experiments were also conducted. When the solution contained other metal ions (such as rare earth metal ions), Fe was added. 3+The fluorescence intensity then significantly decreased, indicating fluorescence quenching. Therefore, this complex material exhibits resistance to Fe in the presence of other metal ions. 3+ It still has a strong recognition effect, indicating that the material has a high Fe content. 3+ It has strong anti-interference ability during identification. Figure 18 ).

[0062] The multifunctional recognition properties of R-Pr have been further extended to the field of food additive detection. R-Pr (3 mg) was dispersed in an ethanol solution containing 0.001 mmol / mL of 16 food additives. The main food additives were: tert-butylhydroquinone (TBHQ), sodium diacetate (SDA), disodium stannous citrate (DSC), 2,4-dichlorophenoxyacetic acid (2,4-D), ethoxyquinoline (EQ), benzimidazole (BZI), sodium propionate (NaPr), methylparaben (Nipagin M), sodium benzoate (NaA), deoxyacetic acid (DA), potassium sorbate (PS), ethylparaben (Ethyl), butylated hydroxyanisole (BHA), sodium bicarbonate (NaHCO3), calcium propionate (CP), and ascorbic acid (Vc). Compared to the blank control sample without any food additives, the emission spectrum changed most significantly after adding ethoxyquinoline (EQ), showing a clear peak position shift and fluorescence enhancement. The strongest emission peak shifted from 315 nm in the blank sample to 445 nm, with a fluorescence intensity enhancement rate as high as 124.4%. Compared to the blank control sample without any food additives, the fluorescence intensity quenching rate after adding 2,4-dichlorophenoxyacetic acid (2,4-D) was as high as 99.7%, demonstrating a significant recognition effect. Figure 19 ).

[0063] Furthermore, the strongest emission peak of benzimidazole (BZI) was located at 293 nm. Compared with the blank control sample, it showed a slight blue shift, but the intensity change was not significant, and the recognition effect was not obvious. After adding sodium stannous citrate (DSC) and methylparaben (Nipagin M), the emission spectrum showed two emission peaks, one at 315 nm and the other at 350 nm. The peak intensity was weaker than that of the blank, but it was not quenched. The peak at 350 nm was stronger. After adding deoxyacetic acid (DA) and ascorbic acid (Vc), the strongest emission peak red-shifted to 375 nm compared with the blank control sample. The remaining nine food additives—tert-butylhydroquinone (TBHQ), sodium diacetate (SDA), sodium propionate (NaPr), sodium benzoate (NaA), potassium sorbate (PS), ethylparaben (Ethyl), butylated hydroxyanisole (BHA), sodium bicarbonate (NaHCO3), and calcium propionate (CP)—all exhibited their strongest emission peaks at 350 nm. Compared to the blank control, the intensity of these peaks was somewhat weakened, and their positions showed a red shift, but the magnitude of the red shift was small, resulting in a negligible recognition effect. In conclusion, among the 16 food additives mentioned above, the complex R-Pr showed the best recognition effect for ethoxyquinoline (EQ) and 2,4-dichlorophenoxyacetic acid (2,4-D).

[0064] Figure 20 These are images of the R-Pr blank and the sample after the addition of ethoxyquinoline under ultraviolet light at a wavelength of 254 nm. The bright blue fluorescence emitted under ultraviolet light after the addition of ethoxyquinoline demonstrates its significant fluorescence response to the substance. Figure 21 Images of the R-Pr blank and the sample after the addition of 2,4-dichlorophenoxyacetic acid under ultraviolet light at a wavelength of 254 nm. The addition of 2,4-dichlorophenoxyacetic acid resulted in purple fluorescence, confirming its ability to identify and detect 2,4-dichlorophenoxyacetic acid.

[0065] The multifunctional recognition properties of R-Pr were further extended to the field of antibiotic detection. R-Pr (3.0 mg) was dispersed in an ethanol solution containing 0.001 mmol / mL of antibiotics, including 17 antibiotics, mainly: sulfamethoxazole (SMZ), erythromycin (EM), metronidazole (DMZ), chloramphenicol (CAP), sulfadiazine sodium (SM2-Na), tetracycline (TC), sulfathiazole (ST), sulfadiazine (SD), florfenicol (FFC), nitrofurantoin (NT), amoxicillin (AMX), doxycycline (DOX), methacycline hydrochloride (METC-HCl), dimethylaminotetracycline hydrochloride (MH), nitrofurazone (NF), metronidazole (MTZ), and oxytetracycline (OTC). Figure 22 For the present invention R-Pr at 10 -3Fluorescence emission spectra of antibiotic solutions at mmol / mL. Compared to the blank control, the addition of oxytetracycline (OTC) quenched the strongest emission peak, with a quenching rate exceeding 99%. For the remaining 16 antibiotics, compared to the blank control, the intensity of the strongest emission peak was generally significantly reduced, but the quenching effect was not obvious, and the peak position shifted, resulting in poor identification. Figure 23 Images of the R-Pr blank probe and the probe with oxytetracycline added under 254 nm ultraviolet light are shown. The images visually demonstrate that the R-Pr probe turns yellow-green under 254 nm ultraviolet light after the addition of oxytetracycline, proving its fluorescent response to oxytetracycline.

Claims

1. A praseodymium complex crystal material, characterized in that: The chemical formula of the praseodymium complex crystal material is {[Pr(L 1.5 [(DMF)2(H2O)]·2DMF}, with ligand 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfonated diethyl)dibenzoic acid H2L, has the following chemical structure: 。 2. The praseodymium-based complex crystal material according to claim 1, characterized in that: From the perspective of structural connection construction, the praseodymium-based complex crystal material has a two-dimensional layered structure.

3. The praseodymium-based complex crystal material according to claim 1, characterized in that: The crystal structure of the praseodymium complex crystal material belongs to the triclinic crystal system. P Space group -1, cell parameters are: a = 12.5838(3) Å, b = 14.3012(4) Å, c = 17.2778(5) Å, α = 66.9140(10), β = 70.7060(10), γ = 89.9280(10).

4. The praseodymium-based complex crystal material according to claim 1, characterized in that: In the asymmetric structural unit of R-Pr, the coordination number of Pr(III) is 9; Pr(III) is coordinated with nine O atoms, six of which are O1, O2, O3, and O5. i O6 i O6 ii The Pr(III) groups originate from four different H2L ligands, with two additional O atoms (O8 and O9) from a coordinated DMF molecule and one O atom (O7) from a coordinated water molecule. Ignoring the coordination solvent molecules, two adjacent Pr(III) groups are linked together by the O6 atom in their two carboxyl groups to form a Pr2L6 secondary structural unit, which simultaneously connects six L atoms. 2- Ligands, each L 2- Then connect the two Pr(III); in space, Pr(III) and L 2- The ligands form a 2D layered structure.

5. A method for preparing a praseodymium-based complex crystal material as described in any one of claims 1-4, characterized in that: The process includes the following steps: weigh Pr(NO3)3·6H2O, the main ligand H2L, and the auxiliary non-coordinate ligand 1,4-bis(imidazol-1-yl)benzenebib and add them to a mixed solvent of DMF / ethanol / water. Seal and heat the mixture to react. After the reaction is complete, allow the system to slowly cool to room temperature to obtain yellow flaky crystals.

6. The method for preparing praseodymium-based complex crystal materials according to claim 5, characterized in that: The molar ratio of Pr(NO3)3·6H2O, the main ligand H2L, and bib is 1:1:0.5, the volume ratio of DMF / ethanol / water is 5:2:1, and the amount of mixed solvent added is limited to 0.1 mmol corresponding to 8 ml of mixed solvent.

7. The method for preparing praseodymium-based complex crystal materials according to claim 5, characterized in that: The heating reaction was carried out at 90°C for 3 days.

8. A praseodymium complex crystal material as described in any one of claims 1-4 in Fe 3+ Applications in recognition.

9. The use of a praseodymium complex crystal material as described in any one of claims 1-4 in the recognition of ethoxyquinoline and 2,4-dichlorophenoxyacetic acid.

10. The application of a praseodymium complex crystal material as described in any one of claims 1-4 in the identification of oxytetracycline.

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