Dual-emission fluorescence sensor as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of analysis sensing detection, and particularly relates to a dual-emission fluorescence sensor and a preparation method and application thereof. The method comprises the following steps: dispersing ZrCl4, 2-hydroxyterephthalic acid and 2, 5-thiophenedicarboxylic acid in a solvent, and adding acetic acid under a stirring condition to obtain a mixture; then putting the mixture into a high-pressure reaction kettle for reaction, and after the reaction is finished, centrifuging, washing and drying in vacuum to obtain UTDCA; then dispersing EuCl3. 6H2O into water, heating, centrifuging, washing and drying in vacuum to obtain the dual-emission fluorescence sensor. The dual-emission fluorescence sensor prepared by the preparation method disclosed by the invention can identify, distinguish and sensitively detect CBL and IMD, has the advantages of good selectivity, interference resistance, repeatability, recoverability and the like, and shows huge practical application potential in food and environmental safety application.

Description

Technical Field

[0001] The present application belongs to the field of analytical sensing detection technology, and specifically relates to a dual-emission fluorescence sensor and a preparation method and application thereof. Background Art

[0002] Pesticides are essential for controlling pests, weeds, and plant diseases. In agricultural production, multiple pesticides are often used simultaneously to increase crop yields and economic benefits. However, the superposition effect of different pesticides increases their residual risks in drinking water, soil, and food, and makes pesticide residue detection difficult. Therefore, the simultaneous quantitative detection of multiple pesticides in the environment is beneficial to protecting the environment and food safety. Carbaryl (CBL) is the first successfully used carbamate insecticide with long-residue and broad-spectrum characteristics. It is mainly used to control cotton bollworm, leaf roller, thrips, rice leafhopper, and fruit tree pests. However, high concentrations of CBL irreversibly inhibit acetylcholinesterase (AChE) and accumulate in neurotransmitters, leading to various neurological diseases and even death. In addition, CBL may have potentially destructive effects on DNA, leading to serious diseases such as reproductive abnormalities. Imidacloprid (IMD) is a selective agonist of nicotinic acetylcholine receptors (nAChRs) with the advantages of long duration, broad spectrum, stability, and high efficiency. However, IMD can enter the human body and gradually accumulate, causing significant toxicity to immunity, nerve conduction and cardiovascular diseases. Therefore, many organizations and countries have set maximum residue limits for CBL and IMD. The U.S. Environmental Protection Agency and the European Union stipulate that the maximum residue limits for CBL in agricultural products are 20 and 50 μg / kg, respectively. The EU food safety standard stipulates that the content of IMD in fruit should not exceed 100 μg / kg.

[0003] To date, many analytical techniques have been used to quantitatively detect CBL and IMD, respectively. Among them, high performance liquid chromatography (HPLC) and electrochemical analysis are the two most widely used methods. Although HPLC has high sensitivity, its sample pretreatment is complex and the instrument operation is cumbersome. Electrochemical analysis has high sensitivity, but it is affected by many factors, such as electrochemically active molecules and solution pH. In addition, electrochemical analysis lacks sufficient repeatability because the electrode surface is covered with oxidation products. In addition, it is difficult for traditional methods to non-invasively distinguish and quantitatively detect multiple pesticides in the same sample. Fluorescence detection technology has been widely studied in recent years due to its high sensitivity, fast response speed, strong real-time detection, and simple operation. However, most reported fluorescent sensors only determine the analyte concentration through a single response mode (enhancement or attenuation). The background interference of such sensors will seriously reduce the detection accuracy, and the fluorescence color change is not easy to identify with the naked eye. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide a dual-emission fluorescence sensor and a preparation method and application thereof, specifically adopting the following technical solutions: In a first aspect, the present invention provides a method for preparing a dual-emission fluorescence sensor, comprising the following steps: S1: Dispersing ZrCl4, 2-hydroxyterephthalic acid and 2,5-thiophenedicarboxylic acid in a solvent, adding acetic acid under stirring to obtain a mixture; then placing the mixture in a high-pressure reactor for reaction, centrifuging after the reaction, washing, and vacuum drying to obtain UTDCA; S2: EuCl3·6H2O and UTDCA obtained in S1 are dispersed in water, heated, centrifuged, washed, and vacuum dried to obtain the dual-emission fluorescence sensor.

[0005] The present invention uses 2-hydroxyterephthalic acid (H2BDC-OH) and 2,5-thiophenedicarboxylic acid (TDCA) to synthesize a UiO-66 type MOF material (UTDCA), and further adds Eu 3+ A dual-emission fluorescence sensor (EuUTDCA) was constructed by coordination with UTDCA, in which the two emission peaks of EuUTDCA in the present invention are attributed to H2BDC-OH and Eu 3+ .

[0006] Preferably, the amount ratio of ZrCl4, 2-hydroxyterephthalic acid, 2,5-thiophenedicarboxylic acid, solvent and acetic acid is 0.4 mmol: 0.54 mmol: 0.06 mmol: 60 mL: 6.0 mL. More preferably, the solvent is N,N-dimethylformamide.

[0007] Preferably, the usage ratio of EuCl3·6H2O and UTDCA in S2 is 5 mM:0.2 g.

[0008] Preferably, the reaction temperature in S1 is 120° C. and the reaction time is 24 h.

[0009] Preferably, the heating temperature in S2 is 80° C. and the heating time is 24 h.

[0010] Preferably, the washing process in S1 is: washing the centrifuged product with N,N-dimethylformamide and ethanol in sequence.

[0011] Preferably, the washing process in S2 is: washing the centrifuged product with water and ethanol in sequence.

[0012] In a second aspect, the present invention provides a dual-emission fluorescence sensor prepared by the above preparation method.

[0013] In a third aspect, the present invention provides the use of the dual-emission fluorescence sensor in the simultaneous quantitative detection of carbaryl (CBL) and imidacloprid.

[0014] In a fourth aspect, the present invention further provides a portable paper-based sensor for simultaneously detecting carbaryl and imidacloprid, wherein the portable paper sensor is prepared from the above-mentioned dual-emission fluorescence sensor.

[0015] Beneficial effects of the present invention: (1) The present invention synthesizes a UiO-66 type MOF material (UTDCA) by using 2-hydroxyterephthalic acid (H2BDC-OH) and 2,5-thiophenedicarboxylic acid (TDCA), and further by adding Eu 3+ A dual-emission fluorescence sensor (EuUTDCA) was constructed by coordination with UTDCA. The ratiometric fluorescence response and built-in self-calibration mode of the dual-emission fluorescence sensor can identify, distinguish and sensitively detect CBL and IMD, and can be well applied in the simultaneous quantitative detection of CBL and IMD in river water and honeysuckle samples.

[0016] (2) The dual-emission fluorescence sensor provided by the present invention has good selectivity, anti-interference ability, repeatability and recyclability. In addition, according to the data results of the embodiments of the present invention, the dual-emission fluorescence sensor provided by the present invention has a good recovery rate for real samples. Mixed solutions of CBL and IMD with different concentrations were also added to river water samples, and the spiked recovery rate of quantitative detection ranged from 85.7% to 114.3%.

[0017] (3) The present invention also provides a paper-based sensor that realizes non-invasive and real-time monitoring of two pesticides in apples, grapes, cucumbers, green peppers and lettuce leaves, which has high feasibility. Therefore, the dual-emission sensor provided by the present invention provides a practical strategy for non-invasive visualization and simultaneous quantification of CBL and IMD, showing great practical application potential in food and environmental safety applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The HPLC linear standard curves established with different concentrations of CBL and IMD are shown as follows: (a) CBL: river water sample; (b) CBL: honeysuckle sample; (c) IMD: river water sample; (d) IMD: in honeysuckle sample; Figure 2 Shown is the PXRD pattern of the material prepared in Example 1; Figure 3 Shown is the FT-IR spectrum of the material prepared in Example 1; Figure 4The XPS full spectrum, high-resolution fine energy spectrum, and binding energy change diagram of the material prepared in Example 1 are shown; (a) the XPS full spectrum of the material; (b) the high-resolution fine energy spectrum of C 1s in EuUTDCA; (c) the high-resolution fine energy spectrum of Eu 3d in EuUTDCA; (d) the binding energy change of O 1s of the material; Figure 5 Shown are SEM images of the materials prepared in Example 1; (a) SEM image of UTDCA, the inset is the particle size distribution of UTDCA; (b) SEM image of EuUTDCA, the inset is the particle size distribution of EuUTDCA; Figure 6 Shown is the EDS elemental mapping of EuUTDCA of the material prepared in Example 1; Figure 7 Shown is the TGA graph of the material prepared in Example 1.

[0019] Figure 8 Shown are the spectrum and fluorescence photographs of the material prepared in Example 1; (a) the solid spectrum and fluorescence photograph of the material; (b) the spectrum and fluorescence photograph of the material dispersed in H2O; Fig. 9 Shown is the best excitation image of EuUTDCA in H2O; Fig.10 Shown is the 3D fluorescence spectrum of EuUTDCA; Fig.11 Shown is the optimal dispersion concentration diagram of EuUTDCA in H2O; Fig.12 Shown is the fluorescence time stability diagram of EuUTDCA; Fig.13 Shown is the pH fluorescence stability graph of EuUTDCA; Fig.14 Shown is the fluorescence stability diagram of EuUTDCA in NaCl solutions with different concentrations; Fig.15 Shown is the stability graph of EuUTDCA against photobleaching; Fig.16 Shown are the titration spectra of CBL and F 445 / F 614 Linear relationship with CBL concentration; (a) Titration spectrum of CBL, the inset is the fluorescence photo of EuUTDCA dripping with different concentrations of CBL (b) F 445 / F 614 Linear relationship with CBL concentration; Fig.17Shown is the titration spectrum of IMD, ( F 0 / F ) 445 and( F 0 / F ) 614 Linear relationship diagram with IMD concentration; (a) Titration spectrum of IMD, the inset is the fluorescence photo of EuUTDCA with different concentrations of IMD added (b) F 0 / F ) 445 and( F 0 / F ) 614 Linear relationship with IMD concentration; Fig.18 Shown are the fluorescence images of EuUTDCA after adding different pesticides; Fig.19 Shown are the fluorescence emission spectra of EuUTDCA after adding different pesticides; Fig. 20 Shown is the EuUTDCA F 445 / F 614 intensity, fluorescence intensity at 380 nm, and intensity at 445 and 614 nm; (a) EuUTDCA after adding CBL in the presence of different interferents F 445 / F 614 (b) The fluorescence intensity of EuUTDCA at 380 nm after adding CBL in the presence of different interfering substances. (c) The intensity of EuUTDCA at 445 and 614 nm after adding IMD in the presence of different interfering substances. Fig.21 Shown are the time-resolved fluorescence responses of EuUTDCA to CBL and IMD; (a) Time-resolved fluorescence response of EuUTDCA to CBL; (b) Time-resolved fluorescence response of EuUTDCA to IMD; Fig. 22 The PXRD patterns and fluorescence response diagrams of three batches of EuUTDCA are shown; (a) PXRD patterns of three batches of EuUTDCA; (b) fluorescence responses of three batches of EuUTDCA to CBL and IMD; each data represents the mean ± SD of 10 parallel measurements per batch, "ns" means no significant difference, t test, p >0.05( p Values ​​< 0.05 indicated statistical significance); Fig.23Figure 5 shows the five regeneration cycles of the sensor EuUTDCA used for CBL and IMD detection; (a) Five regeneration cycles of the sensor EuUTDCA used for CBL detection; (b) Five regeneration cycles of the sensor EuUTDCA used for IMD detection; Fig.24 Shown are the fluorescence intensity diagrams of EuUTDCA under different conditions, the truth table of the logic gate, and the equivalent circuit of the NOR logic circuit; (a) The fluorescence intensity of EuUTDCA in the presence / absence of CBL / IMD at 445 and 614 nm, the gray cross section represents the set threshold; (b) The truth table of the logic gate; (c) The equivalent circuit of the NOR logic circuit; Fig.25 The figure shows the effect of different concentrations of IMD on the fluorescence intensity of the EuUTDCA system at 380 nm in the presence of CBL; (b) the effect of different concentrations of CBL on the fluorescence intensity of the EuUTDCA system at 445 nm in the presence of IMD; (c) F / F 0) 380 Linear relationship with IMD concentration; Fig.26 Shown is the PXRD pattern of EuUTDCA after detection of CBL and IMD; Fig. 27 Shown are the UV-visible adsorption spectra of CBL, IMD, and TDCA; Fig.28 Shown are the energy spectra of the materials; (a) XPS O1s energy spectra of CBL, IMD, CBL@EuUTDCA and IMD@EuUTDCA; (b) XPS N 1s energy spectra of CBL, IMD, CBL@EuUTDCA and IMD@EuUTDCA; (c) XPS Eu 3d energy spectra of EuUTDCA, CBL@EuUTDCA and IMD@EuUTDCA.

[0020] Fig.29 Shown are the UV-visible adsorption spectra of the materials; (a) UV-visible adsorption spectra of EuUTDCA, CBL@EuUTDCA and IMD@EuUTDCA; (b) 3+ 、Eu 3+ +CBL and Eu 3+ +UV-visible absorption spectrum of IMD; Fig.30The fluorescence lifetime diagrams of EuUTDCA at 445 nm and 614 nm after detecting CBL and IMD are shown; (a) The fluorescence lifetime of EuUTDCA at 445 nm after detecting CBL and IMD; (b) The fluorescence lifetime of EuUTDCA at 614 nm after detecting CBL and IMD; Fig.31 Shown are the emission spectra of TDCA under different conditions and the comparison between the calculated and measured quenching efficiencies (a) Emission spectra of TDCA after adding different concentrations of IMD (0–150 μM); (b) Comparison between the calculated and measured quenching efficiencies of TDCA at different concentrations of IMD; Fig.32 Shown are the schematic diagram of paper-based sensor preparation and the results of CBL and IMD used to detect the surface of fruits and vegetables; (a) Schematic diagram of paper-based sensor preparation based on EuUTDCA, the inset is the SEM image of the paper-based sensor before and after loading EuUTDCA; (b) Paper-based sensor is used to detect CBL and IMD on the surface of fruits and vegetables; Fig.33 Shown is a schematic diagram of the smartphone-assisted paper-based sensor for detecting CBL and IMD. The inset is the fluorescence image of the paper-based sensor after adding different concentrations of CBL and IMD, and the linear relationship between the B / R value and CBL concentration, and the RGB value and IMD concentration.

[0021] Fig.34 Shown are the fluorescence image of the paper-based sensor, the RGB value of the paper-based sensor and the PCA analysis graph; (a) Fluorescence image of the paper-based sensor after adding different interfering substances; (b) RGB values ​​of the paper-based sensor containing different interfering substances. (c) PCA analysis based on the RGB values ​​of the paper-based sensor; Fig.35 Shown is a graph of the temporal stability of the paper-based sensor; Fig.36 Shown are the target concentration distribution measured by RGB analysis and the CV graphs at different CBL concentrations; (a) target concentration distribution measured by RGB analysis and the CV at different CBL concentrations; (b) target concentration distribution measured by RGB analysis and the CV at different IMD concentrations; Fig.37 Shown are the fluorescence emission spectra and fluorescence intensity graphs of EuUTDCA under different conditions; (a) EuUTDCA fluorescence emission spectra with or without river water and honeysuckle samples; (b) EuUTDCA fluorescence intensities at 445 and 614 nm with or without river water and honeysuckle samples; where "ns" means no significant difference; Fig.38 Shown are the synthesis of EuUTDCA and its fluorescence response to CBL and IMD. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] Example 1 A method for preparing a dual-emission fluorescence sensor comprises the following steps: (1) Synthesis of UTDCA by hydrothermal method: ZrCl4 (0.4 mmol), 2-hydroxyterephthalic acid (H2BDC-OH, 0.54 mmol) and 2,5-thiophenedicarboxylic acid (TDCA, 0.06 mmol) were dispersed in 60 mL of N,N-dimethylformamide (DMF) solution. Acetic acid (6.0 mL) was slowly added under continuous stirring. The mixture was transferred to an autoclave and reacted at 120 °C for 24 h. The white product was collected by centrifugation, washed three times with DMF and ethanol, and dried in a vacuum oven at 80 °C to obtain UTDCA (yield: 0.85 g); (2) Synthesis of dual-emission fluorescence sensor (EuUTDCA): EuCl3·6H2O (5 mM) and UTDCA (0.2 g) were mixed in 50 mL of water with continuous stirring and heated at 80 °C for 24 h. The white precipitate was collected by centrifugation, washed three times with water and ethanol each, and dried in a vacuum oven (yield: 0.16 g).

[0024] The UTDCA and EuUTDCA prepared above were characterized, and the results are as follows: The powder X-ray diffraction (PXRD) patterns of UTDCA and EuUTDCA are in good agreement with the theoretical simulation results ( Figure 2 ), indicating the successful preparation of the material. PXRD results also confirmed that the doped Eu 3+ The MOF structure was well maintained. Fourier transform infrared (FT-IR) spectroscopy confirmed that Eu 3+ Coordination with UTDCA. 1660 cm -1 The peak at is attributed to the protonated carboxyl groups in UTDCA, whereas this peak is not observed in EuUTDCA ( Figure 3 ), indicating that Eu 3+ With -COO - Group coordination. At 1420 and 1520 cm -1 -COO -Asymmetric and symmetric vibrations. X-ray photoelectron spectroscopy (XPS) further confirmed that Eu 3+ Successful doping. Figure 4 (a) shows that the characteristic peak of Eu 3d is observed in EuUTDCA, indicating that Eu 3+ The high-resolution Eu 3d peaks at 1163.9 and 1133.72 eV are attributed to Eu 3d 3 / 2 and Eu 3d 5 / 2 ( Figure 4 (b)). The high-resolution C 1s peak of EuUTDCA exhibits a main peak at 284.82 eV ( Figure 4 (c)), corresponding to the sp 2 The peaks at 284.19, 286.56, and 288.87 eV are associated with CS, CO, and C=O bonds, respectively. 3+ The O 1s peak shifts from 531.73 eV to 531.83 eV due to coordination interaction ( Figure 4 (d)). The coordinated Eu was further determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. 3+ The content of Zr 4+ With Eu 3+ The molar ratio of UTDCA to EuUTDCA was 5.52:1. Scanning electron microscopy (SEM) was used to observe the morphology of UTDCA and EuUTDCA. Figure 5 As shown in (a) and (b), the two materials have similar octahedral structures with average sizes of 555 and 546 nm, respectively. Figure 5 Inset), showing that Eu 3+ There is no significant effect on the morphology and particle size of UTDCA. Elemental mapping shows that C, O, S, Zr and Eu are uniformly distributed throughout EuUTDCA ( Figure 6 Thermogravimetric analysis (TGA) was used to test the thermal stability of UTDCA and EuUTDCA. The free solvent molecules of the materials were lost in the range of 65-115 °C. The weight losses of UTDCA and EuUTDCA in the first stage were 13.5% and 14.6%, respectively ( Figure 7 The weight loss in the second stage from 115 to 420 °C due to the loss of coordinating solvent molecules is 7.8% and 8.3%, respectively. These results indicate that both materials have good structural stability within 420 °C.

[0025] Example 2 The dual-emission fluorescence sensor (EuUTDCA) prepared in Example 1 was subjected to fluorescence sensing experiments. Before the sensing experiments, 8.0 mg EuUTDCA powder was dispersed in 20 mL H2O and sonicated for 20 min to prepare a homogeneous sensor suspension.

[0026] (1) The luminescence characteristics of the EuUTDCA sensor suspension prepared above were tested at room temperature. The results are as follows: Figure 8-Figure 15 shown by Figure 8 (a) It can be seen that blue and red emissions can be observed in the solid-state spectra of UTDCA and EuUTDCA, respectively. Due to the charge transfer from ligand to metal, a weaker broad emission band (445 nm) is observed for UTDCA, and EuUTDCA is observed at 578, 592, 614, 651, and 699 nm. 3+ characteristic emission bands. Figure 8 (b) shows the emission spectra of UTDCA and EuUTDCA dispersed in H2O. A broad emission band was observed for UTDCA at 445 nm, and the blue emission was visible to the naked eye ( Figure 8 (b) Inset). The emission spectrum of the EuUTDCA suspension shows two emission bands at 445 and 614 nm, with the red emission visible to the naked eye ( Figure 8 (b) Inset). The intensity of EuUTDCA increases with the excitation wavelength and reaches a maximum at 315 nm ( Fig. 9 ). The three-dimensional fluorescence spectra of EuUTDCA suspensions showed that these materials exhibited two emission peaks, which were attributed to H2BDC-OH and Eu 3+ ( Fig.10 The optimal concentration of EuUTDCA dispersed in H2O is 0.4 mg / L ( Fig.11 ). Fig.12 The fluorescence intensity of EuUTDCA after immersion in H2O for 15 days showed no significant change, indicating that its fluorescence was stable in aqueous media. In addition, the fluorescence stability of EuUTDCA at different pH values ​​was studied ( Fig.13 ), the fluorescence intensity at 445 and 614 nm remained stable in the pH range of 3-9. Fig.14 As shown in Figure 2, EuUTDCA exhibits good fluorescence stability in a wide range of NaCl solution concentrations (0.05-15 mM). After continuous irradiation with a 313 nm UV lamp (6 W) for 12 h, the fluorescence intensity of the EuUTDCA aqueous suspension remained almost unchanged ( Fig.15 ), indicating that it has good stability against photobleaching. These excellent luminescence properties of EuUTDCA indicate that it has the potential to be used as a fluorescent sensor in aqueous media.

[0027] (2) The sensing performance was studied by recording the emission spectra of EuUTDCA after adding different concentrations of CBL and IMD. For CBL sensing, the color of EuUTDCA changed from red to blue-purple ( Fig.16 (a) Inset). The fluorescence intensity at 614 nm decreased significantly, while the change at 445 nm was negligible ( Fig.16 (a)). F 445 / F 614 The results showed a good linear relationship with CBL concentration in the concentration range of 0.5-130 μM (R 2 = 0.9958)( F 445 / F 614 = 0.0146[CBL] + 0.2626 Equation 1, Fig.16 (b)). The detection limit (LOD) of CBL was calculated to be 0.083 μM. For IMD sensing, the fluorescence color of EuUTDCA changed from red to colorless, and the fluorescence intensities at 445 and 614 nm were gradually quenched ( Fig.17 (a)). F 0 / F ) 445 = 0.007[IMD] +1.0185(R 2 = 0.9931, Equation 2) and ( F 0 / F ) 614 = 0.0118[IMD] + 1.0297(R 2 = 0.9939, Equation 3, Fig.17 (b) The linear equation was used for quantitative determination. The LOD values ​​of IMD were 0.177 μM and 0.094 μM, respectively.

[0028] (3) The present invention also studies the fluorescence response of EuUTDCA to 23 insecticides, including acetamiprid (ACE), benomyl (BEN), carbendazim (CBZ), chlordimeform (CDM), chlorpyrifos (CPF), cyhalothrin (CT), clothianidin (CTN), deltamethrin (DLM), dinotefuran (DNT), fenthioguanidine (FBT), fluazifop (FLU), fumaric acid (FNC), glufosinate ammonium (GLA), isoprocarb (IPC), malathion (MAL), methomyl (MET), metoclocarb (MTMC), nitenpyram (NPM), paraquat (PQ), tricyclazole (TC), trifloxylin (TDZ), trifluralin (TFL) and thiamethoxam (TMX). The emission spectra of the mixture (2 mL) containing EuUTDCA (0.4 mg / mL) suspension and all insecticides (200 μM) were recorded. Fluorescence spectra were recorded at an excitation wavelength of 315 nm and a slit width of 2.0 / 2.0 nm, and all measurements were performed in triplicate.

[0029] The results are as follows Figure 18-Figure 21 As shown in the results, only CBL and IMD changed the color and fluorescence intensity of EuUTDCA. The effects of other pesticides were negligible, indicating that EuUTDCA had high selectivity for CBL and IMD. In addition, EuUTDCA showed good response to CBL and IMD in the presence of other pesticides, showing its good anti-interference ability ( Fig. 20 In addition, EuUTDCA responds quickly to CBL and IMD, and the emission intensities of CBL and IMD at 614 and 445 nm are rapidly quenched within 10 seconds ( Fig.21 ).

[0030] (4) Recycling experiment of EuUTDCA After CBL or IMD sensing, EuUTDCA was washed with ethanol several times and dried under vacuum at 80 °C. The recovered EuUTDCA powder was redispersed in H2O at the same initial concentration (0.4 mg / mL), and then the fluorescence spectra were recorded. This cycle was repeated 5 times.

[0031] The results are as follows Figure 22-23 As shown in the figure, the PXRD patterns of three different batches of EuUTDCA are in good agreement with the simulated PXRD patterns, indicating that the sensor is simple and repeatable ( Fig. 22 (a)). In addition, there is no statistical difference in the fluorescence intensity of the three batches of EuUTDCA ( Fig. 22(b)). The highly consistent responses of the three batches to CBL and IMD confirm the excellent reproducibility of the sensor in terms of detection performance. In addition, after 5 cycles of sensing experiments, the original intensity can be restored, indicating that EuUTDCA can be recycled and reused to detect CBL and IMD ( Fig.23 ).

[0032] (5) Logic gate sensor design Simultaneous detection of multiple analytes in a mixture is challenging due to the coexistence and cross-interference of multiple analytes. Logic gate sensors provide a digital, rigorous and accurate solution for identifying and sensing multiple analytes. According to the different response modes of EuUTDCA to CBL and IMD, this paper designs a novel NOR logic gate sensor, which provides a unique identification path for CBL and IMD. Specifically, CBL and IMD are the input signals, and the signal intensity of the two emission peaks (380 and 445 nm) of EuUTDCA is the output signal. Fig.24 As shown in (a), the threshold value (“on” or “off”) of the logic gate output is defined. F 380 More than 2.4×104 (threshold) or F 445 When it is below 1×105 (threshold), the output is “on”, otherwise, the output is “off”. Therefore, the first column of the truth table represents the output signal (0,0) without CBL and IMD ( Fig.24 (b)). In other input combinations, (0,1), (1,0) and (1,1) represent different output results. Among them, the signal output of (1,1) is only applicable to the simultaneous input of CBL and IMD. Therefore, the Boolean expression of the logic gate function shows that the output of this system is a "NOR" type logic gate ( Fig.24 (c)).

[0033] Example 3 Exploring the quantitative detection of CBL and IMD by EuUTDCA This embodiment is equipped with several mixed solutions with standard concentrations of CBL and IMD, as follows: 0.1, 0.2, 1, 2, 4, 6, 8, 10, 12, 14, 18, 22, and 26 μL of CBL standard solution (10 mM) were added to 3 mL of EuUTDCA suspension (0.4 mg / mL) and then analyzed by fluorescence. The final concentrations of CBL in the mixed solution were 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 90, 110, and 130 μM, respectively. The IMD detection method was the same as that of CBL, but the final concentrations were 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 110, 130, and 150 μM, respectively.

[0034] The results are as follows Fig.25 As shown by Fig.25 As shown in (a), when different concentrations of IMD (1, 3, and 5 μM) are added to the system with CBL, the emission intensity at 380 nm remains unchanged. Similarly, the addition of CBL to the system with IMD does not affect the fluorescence intensity at 445 nm ( Fig.25 (b)). Therefore, it is possible to use (( F / F 0) 380 = 0.0766[CBL] + 1.4841 (R 2 =0.9945)) Equation 4 calculates the CBL concentration in the mixed solution ( Fig.25 (c)). The IMD concentration can be calculated using Equation 2, and the results are shown in Table 1. As shown in Table 1, the detected concentrations of CBL and IMD were consistent with the spiked concentrations in the mixture, confirming that EuUTDCA can simultaneously and quantitatively detect CBL and IMD in the mixed solution.

[0035] Table 1. Simultaneous quantification results of CBL and IMD in mixtures Example 4 Analysis of the fluorescence response mechanism of EuUTDCA To better understand the response mechanism of EuUTDCA sensor to CBL and IMD, PXRD pattern, XPS spectrum, UV-visible spectrum and fluorescence lifetime were studied. The PXRD pattern of EuUTDCA in response to CBL and IMD showed no significant changes ( Fig.26 ), excluding the fluorescence change caused by structural collapse. In addition, the overlapping UV absorption spectra of the two pesticides and TDCA indicate competitive absorption, which prevents the transfer of TDCA to Eu 3+ energy transfer, resulting in fluorescence quenching at 614 nm ( Fig. 27). XPS spectra were used to study the interaction between EuUTDCA and the two pesticides. The binding energy shifts showed that the O and N atoms of CBL and IMD interacted with the Eu 3+ Coordination ( Fig.28 and Table 2). Fig.29 As shown in the figure, the absorbance values ​​of CBL@EuUTDCA and IMD@EuUTDCA red-shifted, which also revealed that Eu 3+ The fluorescence lifetimes of EuUTDCA at 445 and 614 nm were 1.55 ns and 951 μs, respectively, and did not change significantly after the detection of CBL and IMD. These results suggest that the quenching process involves static quenching ( Fig.30 In addition, the quenching of 445 nm fluorescence by IMD is attributed to the internal filter effect (IFE), and the contribution of IFE can be expressed as ( ) is determined by Equation 5.

[0036] Where A and A0 are the absorbance of H2BDC-OH at 315 nm. The fluorescence quenching efficiency at different IMD concentrations was calculated and compared with the absorbance value ( Fig.31 ). The consistency between the two data sets suggests an IFE mechanism. In summary, competitive absorption, interaction, internal filter effect (IFE), and static quenching effects contribute to the fluorescence response of EuUTDCA to CBL and IMD.

[0037] Table 2. XPS binding energy summary Example 5 Preparation and analytical application of paper-based sensors (1) A portable paper sensor, the preparation method of which is as follows: First, Whatman filter paper was cut into strips of 1 cm × 3 cm. Then, the test strips were immersed in EuUTDCA (1.0 mg / mL) ethanol suspension for 5 min and removed to dry at room temperature. The whole process was repeated five times to ensure that EuUTDCA was evenly coated on the surface of the test paper. Finally, a portable paper sensor was obtained.

[0038] When the portable paper sensor obtained above is used for quantitative detection, the paper sensor is immersed in CBL and IMD solutions of different concentrations, and the fluorescence color changes are photographed under a 302 nm ultraviolet light. The RGB values ​​of the fluorescence photos are analyzed using color recognition software installed on a smartphone.

[0039] (2) The portable paper sensor prepared in step (1) is used for non-invasive detection of CBL and IMD in fruit and vegetable samples. The specific process is as follows: Grape, apple, cucumber, green pepper and lettuce leaf samples were obtained from the market. Fruit and vegetable samples were rinsed with water to remove impurities. Then, 50 μL of CBL and IMD were sprayed on the dry sample surface to simulate pesticide contamination. The prepared paper sensor was used to wipe the sample surface sprayed with pesticides, and the fluorescence color of the paper-based sensor was observed under a 302 nm UV lamp.

[0040] The results are as follows Figure 32-Figure 36 As shown, Fig.32 The preparation process of EuUTDCA-based paper-based sensors and their use for non-invasive detection of CBL and IMD residues on the surface of fruit and vegetable samples are shown. CBL and IMD were sprayed on the sample surface to simulate pesticide contamination. After the paper-based sensor was in contact with the sample surface, the color change was visually observed by the naked eye under a 302 nm UV lamp. According to the standard experimental procedure, the entire detection time was less than 1.0 min. However, the color change depends on the naked eye, and it is difficult to distinguish minor changes. Therefore, the present invention designs a smartphone-assisted sensing platform to achieve accurate on-site monitoring of CBL and IMD. The platform can convert the fluorescence image of the paper-based sensor under UV light into specific RGB values. With the increase of CBL concentration, the red fluorescence gradually turns into blue-purple, and the CBL concentration and B / R value show good linearity ( Fig.33 ). Meanwhile, the red color of the paper strips gradually quenched with the increase of IMD concentration. The detection limits of CBL and IMD were 1.33 and 3.33 μM, respectively. In addition, the paper-based sensor showed high selectivity in the color response to CBL and IMD, which can be verified from the RGB values ​​and principal component analysis (PCA) ( Fig.34 The paper-based sensor showed uniform color and almost unchanged RGB values ​​after being stored at room temperature for 20 days, indicating excellent stability ( Fig.35 In addition, the reproducibility and accuracy of the paper-based sensor were evaluated by calculating the coefficient of variation (CV) of the response results of three batches of test strips to the two analytes. Fig.36 As shown in the figure, the CV values ​​of CBL and IMD were 2.05-7.74% and 2.25-7.15%, respectively, indicating that the fluorescence responses of different batches of test strips showed high reproducibility. These results indicate that the paper-based sensor constructed based on EuUTDCA and smartphone-assisted smart sensing platform shows great application potential in the noninvasive quantitative analysis of CBL and IMD.

[0041] Example 7 Actual sample testing and analysis (1) Pretreatment experiment of river water and honeysuckle samples River water was collected from Xunsi River in Hongshan District, Wuhan City, Hubei Province, China. River water samples were centrifuged and filtered through a 0.22 μm membrane to remove insoluble particles and were directly used for testing without additional treatment.

[0042] Honeysuckle samples were obtained from the local market. 2.0 ± 0.1 g of honeysuckle sample was weighed and added with 5 mL H2O and 10 mL acetonitrile, and vortexed for 1 min. Then 1.0 g NaCl and 4.0 g anhydrous MgSO4 were added to the mixture and vortexed for 1 min. The mixture was centrifuged at 5000 rpm for 5 min, and 10 mg C18, 15 mg primary secondary amine (PSA) and 150 mg anhydrous MgSO4 were added to 1.0 mL of the centrifugal supernatant. Finally, the mixture was centrifuged at 12000 rpm for 1 min, and the supernatant was filtered through a 0.22 µm membrane to obtain the pretreated honeysuckle solution.

[0043] (2) Fluorescence analysis 30 μL of CBL (20, 40 and 60 mM) and IMD (10, 30 and 50 mM) solutions of different concentrations were added to 3 mL of pretreated river water samples to obtain mixed solutions of CBL (0.2, 0.4 and 0.6 mM) and IMD (0.1, 0.3 and 0.5 mM) of different concentrations. Then, 30 μL of mixed solutions of different concentrations were added to 3.0 mL of EuUTDCA suspension for fluorescence analysis. The final concentrations of CBL were 2, 4 and 6 μM, and the concentrations of IMD were 1, 3 and 5 μM. The fluorescence analysis method of honeysuckle samples was the same as that of river water samples, except that the pretreated honeysuckle samples were used instead of river water samples.

[0044] (3) Simultaneous quantification of CBL and IMD 30 μL of CBL (10, 40, and 70 mM) and IMD (7, 15, and 30 mM) solutions were simultaneously added to 3 mL of pretreated river water samples to obtain mixed solutions with different concentrations of CBL (0.1, 0.4, and 0.7 mM) and IMD (0.07, 0.15, and 0.3 mM), respectively. Then, 30 μL of the mixed solution was added to 3.0 mL of EuUTDCA suspension (0.4 mg / mL). The final concentrations of CBL were 1, 4, and 7 μM, and the concentrations of IMD were 0.7, 1.5, and 3 μM in the simultaneous quantitative analysis.

[0045] (4) HPLC analysis For HPLC detection of CBL, water / methanol (2 / 8, v / v) was used as the mobile phase, the injection volume was 20 μL, and the flow rate was 1.0 mL / min. A linear standard calibration curve was established using different concentrations (1, 2, 4, 6, 8, 10, and 12 μM, Figure 1). The HPLC detection procedure for IMD was the same as that for CBL, but the mobile phase was water / acetonitrile (7 / 3, v / v).

[0046] Its structure is as Fig.37 As shown in the figure, and as the results show, the pre-treated real sample solution does not affect the EuUTDCA fluorescence response, which indicates that the contents of CBL and IMD are below the LOD value. The individual detection results of CBL and IMD are summarized in Tables 3 and 4, respectively. The proposed fluorescence sensing method achieved satisfactory recoveries with RSDs less than 5.0%. In addition, mixed solutions of CBL and IMD with different concentrations were also added to river water samples, and the spiked recoveries for simultaneous quantitative detection ranged from 85.7-114.3%, with RSD values ​​of 0.2 to 3.1% (Table 5). HPLC also confirmed the contents of CBL and IMD in real samples. These results show that the established fluorescence method is reliable for the individual and simultaneous quantification of CBL and IMD. In addition, the application of the portable sensing platform was evaluated using river water samples (Table 6). The recoveries of the smartphone-assisted visual sensing platform ranged from 82.7% to 105.3%, with RSD values ​​less than 4.0%. These results show that EuUTDCA is suitable for the quantitative analysis of CBL and IMD in real samples.

[0047] Table 3. Detection results of CBL and IMD in river water samples. All concentrations are expressed as the average of three measurements. ND*: Below LOD, not detected Table 4. The results of the detection of CBL and IMD in honeysuckle samples. All concentrations are expressed as the average of three measurements. ND*: Below LOD, not detected Table 5. Simultaneous quantitative detection results of CBL and IMD in river water samples ND*: Below LOD, not detected.

[0048] Table 6. Quantification of CBL and IMD in river water samples using a smartphone-assisted paper-based sensing platform Therefore, in summary, the present invention provides a water-stable dual-emission fluorescence sensor (EuUTDCA) that exhibits different and non-interfering response patterns to CBL and IMD, and is capable of simultaneously and quantitatively detecting these two pesticides. In addition, a logic gate sensor is designed based on EuUTDCA to distinguish and quantify CBL and IMD. The dual-channel binary output of the logic gate sensor changes from 1 / 0 to 0 / 1, which can intelligently identify the two pesticides with higher reliability and accuracy. In addition, a smartphone-assisted paper-based sensing platform is developed to achieve non-invasive identification and portable, rapid, and intelligent quantitative detection of CBL and IMD in fruit and vegetable samples. The dual-emission sensor with different response patterns designed in the present invention provides a new approach for the simultaneous quantitative detection method of multi-target analytes.

[0049] It should be noted that the three batches of sensors in the above experimental process of the present invention refer to being synthesized three times using the same method and raw material dosage (the preparation method of Example 1).

[0050] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, it should belong to the protection scope of the present invention. Within the protection scope of the present invention, its technical scheme and / or implementation method can have various modifications and changes.

Claims

1. A method for preparing a dual-emission fluorescence sensor, characterized in that: The following steps are involved: S1: Dispersing ZrCl4, 2-hydroxyterephthalic acid and 2,5-thiophenedicarboxylic acid in a solvent, adding acetic acid under stirring to obtain a mixture; then placing the mixture in a high-pressure reactor for reaction, centrifuging after the reaction, washing, and vacuum drying to obtain UTDCA; S2: EuCl3·6H2O and UTDCA obtained in S1 are dispersed in water, heated, centrifuged, washed, and vacuum dried to obtain the dual-emission fluorescence sensor.

2. The preparation method according to claim 1, characterized in that The usage ratio of ZrCl4, 2-hydroxyterephthalic acid, 2,5-thiophenedicarboxylic acid, solvent and acetic acid is 0.4 mmol: 0.54 mmol: 0.06 mmol: 60 mL: 6.0 mL.

3. The preparation method according to claim 2, characterized in that: The solvent is N,N-dimethylformamide.

4. The preparation method according to claim 1, characterized in that The dosage ratio of EuCl3·6H2O and UTDCA in S2 was 5 mM:0.2 g.

5. The preparation method according to claim 1, characterized in that The reaction temperature in S1 was 120 °C and the reaction time was 24 h.

6. The preparation method according to claim 1, characterized in that The heating temperature in S2 is 80 °C and the heating time is 24 h.

7. The preparation method according to claim 1, characterized in that: The washing process in S1 is: washing the centrifuged product with N,N-dimethylformamide and ethanol in sequence; The washing process in S2 is: washing the centrifuged product with water and ethanol in sequence.

8. A dual-emission fluorescence sensor, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the dual-emission fluorescence sensor according to claim 8 in the simultaneous quantitative detection of carbaryl and imidacloprid.

10. A portable paper-based sensor for simultaneous detection of carbaryl and imidacloprid, characterized in that: The dual-emission fluorescence sensor is prepared according to claim 8.

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