Indicator replacement sensor for detecting perfluorooctane sulfonic acid as well as preparation method and application of indicator replacement sensor

Abstract

The invention relates to the technical field of organic pollutant detection, in particular to an indicator replacement sensor for detecting perfluorooctane sulfonic acid as well as a preparation method and application of the indicator replacement sensor. Specifically, the sensor is composed of an aminated and fluorinated modified MOF material and an anionic fluorescent dye 1-pyrene sodium sulfonate, and through an indicator replacement analysis strategy, the fluorescent dye is replaced by PFOS, so that the fluorescent'start 'detection of the PFOS is realized, and the detection sensitivity is high. And the risk of generating a false positive result due to the interference of a non-target object, equipment failure or the influence of fluorophore bleaching in practical application is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of organic pollutant detection, and in particular to an indicator displacement sensor for detecting perfluorooctane sulfonic acid, and a preparation method and application thereof. Background Art

[0002] Perfluoroalkyl compounds (PFAS) are widely used in industrial production and commercial products due to their excellent stability, high surface activity and unique water- and oil-proof properties. However, with large-scale production and use, a large amount of PFAS is discharged into the environment. PFAS is extremely persistent and bioaccumulative, and is accompanied by potential developmental toxicity, hepatotoxicity and immunotoxicity. In 2009, as a typical perfluoroalkyl substance, perfluorooctane sulfonic acid (PFOS) and its salts were included in the list of restricted chemicals by the Stockholm Convention on Persistent Organic Pollutants. In addition, the "Announcement on the Prohibition of the Production, Circulation, Use and Import and Export of Persistent Organic Pollutants Such as Lindane" issued in 2019 also stipulates that perfluorooctane sulfonic acid and its salts shall not be used. The "List of New Pollutants under Key Control (2023 Edition)" issued in 2023 has imposed stricter supervision on the production and use of PFAS. Due to the low volatility and good water solubility of PFAS, the water environment has become an important gathering place for it. Therefore, it is crucial to screen and detect PFAS in water quickly, accurately and reliably.

[0003] At present, the conventional detection of PFAS mainly relies on liquid chromatography-mass spectrometry technology, but its equipment is expensive, the operation is complicated and the detection is time-consuming, which limits its widespread application. Fluorescence sensing technology, however, has great potential in the detection of various environmental pollutants due to its simple equipment, convenient operation and rapid detection. Currently, the fluorescence sensing technology used to detect PFAS mostly adopts the fluorescence quenching mechanism, but in actual applications, the fluorescence "off" response may be affected by interference from non-target objects, equipment failure or fluorophore bleaching, which can easily produce false positive results. Summary of the invention

[0004] The present invention provides an indicator displacement sensor for detecting perfluorooctane sulfonic acid. The sensor is based on a fluorescence "on" detection mechanism, which avoids the risk of false positive results caused by interference from non-target objects, equipment failure or fluorophore bleaching in practical applications.

[0005] The present invention also provides a method for preparing the indicator displacement sensor, which is simple and easy to operate.

[0006] The present invention also provides a method for detecting perfluorooctane sulfonic acid in water, which can realize high-sensitivity PFOS detection.

[0007] The present invention achieves the above technical objectives through the following technical solutions:

[0008] An indicator displacement sensor for detecting perfluorooctane sulfonic acid, wherein the sensor is a supramolecular mixed system formed by a receptor and an indicator dispersed in a buffer, wherein the receptor is a chromium-containing metal organic framework grafted with a modifying group, and the modifying group is as shown in Formula I, Formula I; the indicator is sodium 1-benzoylsulfonate, and the pH of the buffer solution is 4±0.3.

[0009] According to the above-mentioned indicator displacement sensor for detecting perfluorooctane sulfonic acid, the concentration of the receptor in the indicator displacement sensor is 3±1 μg / mL, and the concentration of the indicator is 0.05±0.02 μM.

[0010] According to the above-mentioned indicator displacement sensor for detecting perfluorooctane sulfonic acid, the organic ligand in the chromium-containing metal organic framework is terephthalic acid.

[0011] The above-mentioned indicator replacement sensor for detecting perfluorooctane sulfonic acid is used, and the buffer is an acetic acid-sodium acetate buffer with a pH of 4±0.3.

[0012] The detection reaction time of the above-mentioned indicator replacement sensor for detecting perfluorooctane sulfonic acid is not less than 20 minutes.

[0013] The above-mentioned indicator displacement sensor for detecting perfluorooctane sulfonic acid has a linear detection range of 2-50 nM and a detection limit as low as 0.62 nM.

[0014] The present invention also provides a method for preparing the above-mentioned indicator displacement sensor for detecting perfluorooctane sulfonic acid, which comprises at least the following steps:

[0015] 1) reacting a chromium-containing metal organic framework with diethylenetriamine to obtain an amination intermediate;

[0016] 2) reacting the amination intermediate with trifluoromethanesulfonyl chloride under the action of an acid-binding agent to obtain the receptor;

[0017] 3) Dissolving the receptor and the indicator in a buffer solution to obtain the indicator displacement sensor.

[0018] According to the preparation method described above, the mass ratio of diethylenetriamine to the chromium-containing metal organic framework is (4-6):1, and the mass ratio of trifluoromethanesulfonyl chloride to the amination intermediate is (1.2-1.6):1.

[0019] According to the above preparation method, in step 1), the reaction temperature is 110°C.

[0020] According to the above preparation method, in step 2), the reaction temperature is 20-30°C.

[0021] The present invention also provides a method for detecting perfluorooctane sulfonic acid in water, comprising the step of using the above-mentioned indicator replacement sensor for detecting perfluorooctane sulfonic acid to perform detection.

[0022] The present invention is based on the fluorescence "on" detection mechanism provided by the indicator displacement analysis strategy, utilizing the combination of bifunctionalized MOF and fluorescent dye 1-PS, and realizing competitive displacement in the presence of PFOS through electrostatic, hydrophobic and fluorine-fluorine interactions, thereby inducing a significant fluorescence enhancement effect, achieving highly sensitive PFOS detection, and avoiding the risk of false positive results caused by interference from non-target objects, equipment failure or fluorophore bleaching in actual applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The synthetic route of the receptor in Example 1 of the present invention is shown in FIG.

[0024] Figure 2 is a SEM image of MIL-101-DETA-TF in Example 1 of the present invention;

[0025] Figure 3 Spectra of MIL-101(Cr) and MIL-101-DETA-TF in Example 1 of the present invention, wherein a is an XRD spectrum, b is an FTIR spectrum, and c is an XPS full spectrum;

[0026] Figure 4 The UV-visible absorption spectra and fluorescence emission spectra of 1-PS, MIL-101-DETA-TF and PS-MIL systems, where a is the UV-visible absorption spectrum and b is the fluorescence emission spectrum;

[0027] Figure 5 This is a schematic diagram of PFOS fluorescence detection based on the indicator displacement analysis method of the present invention;

[0028] Figure 6 is the relationship between the fluorescence emission spectrum of the PS-MIL system and the fluorescence enhancement effect and the PFOS concentration, where a is the fluorescence emission spectrum of the PS-MIL system (λ ex = 342 nm) with the change trend of PFOS concentration, b is the linear relationship between the fluorescence enhancement response and PFOS concentration;

[0029] Figure 7 The results of the stability experiment of the PS-MIL system, where a is the fluorescence intensity change of the PS-MIL system after seven days of storage, and b is the fluorescence intensity change of the PS-MIL system under continuous excitation light irradiation. The error bar represents the standard deviation of three measurements.

[0030] Figure 8The selectivity of PS-MIL system for PFOS (10 μM). DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Existing fluorescent sensors for detecting PFAS mostly use a fluorescence quenching mechanism, which may be affected by interference from non-target objects, equipment failure or fluorophore bleaching, and are prone to false positive results. The present invention provides an indicator displacement sensor with a fluorescence "on" response based on an indicator displacement analysis strategy. The indicator displacement sensor is a supramolecular-based sensing method, in which the indicator first reversibly binds to the receptor through hydrogen bonds, electrostatic interactions, metal complexes or hydrophobic interactions to form a supramolecular complex. When the target analyte is added to the system, if its binding ability to the receptor is stronger, it will displace the indicator, thereby generating a detectable optical signal.

[0033] The present invention specifically comprises a sensor composed of an amino and fluorinated MOF material and an anionic fluorescent dye, and through an indicator replacement analysis strategy, utilizes the replacement of the fluorescent dye by PFOS to successfully realize the fluorescence "on" detection of PFOS, thus avoiding the risk of false positive results caused by interference from non-target objects, equipment failure or fluorophore bleaching in practical applications.

[0034] Specifically, the present invention provides an indicator displacement sensor for detecting perfluorooctane sulfonic acid, wherein the sensor is a supramolecular hybrid system (denoted as PS-MIL) formed by a receptor and an indicator dispersed in a buffer, wherein the receptor is a chromium-containing metal organic framework grafted with a modifying group, and the modifying group is as shown in Formula I, Formula I;

[0035] The indicator is sodium 1-benzoylsulfonate (1-PS for short), and the pH of the buffer solution is 4±0.3.

[0036] Further studies found that when the concentration of the receptor in the indicator displacement sensor was 3±1 μg / mL and the concentration of the indicator was 0.05±0.02 μM, the system had a higher detection sensitivity for PFOS.

[0037] In the present invention, the organic ligand in the chromium-containing metal organic framework is terephthalic acid.

[0038] Further studies have also found that when the pH of the buffer is 4±0.3, the fluorescence enhancement is most significant under different PFOS concentration conditions. For example, in some specific embodiments, the buffer is an acetic acid-sodium acetate buffer with a pH of 4.

[0039] Further studies also found that the mixed system of 1-PS and MIL-101-DETA-TF reached equilibrium within 25 minutes, while the PS-MIL system after adding PFOS reached fluorescence equilibrium in about 20 minutes. Therefore, its detection reaction time was not less than 20 minutes, among which 20 minutes was the optimal reaction time.

[0040] It was further found that under the optimal conditions, the fluorescence emission intensity of the PS-MIL system increased significantly with the increase of PFOS concentration, and the maximum enhancement rate exceeded 12 times ( Figure 6 a), and showed a good linear relationship in the concentration range of 2-50nM, which can achieve quantitative detection of PFOS. Further linear fitting results show that the detection limit of PFOS in this system is as low as 0.62nM. This detection limit is significantly better than most reported PFAS fluorescent sensors (10 -5 -10 -9 mol / L) and is lower than the World Health Organization's limit concentration of PFAS in drinking water (500ng / L).

[0041] The present invention also provides a method for preparing the above-mentioned indicator displacement sensor for detecting perfluorooctane sulfonic acid, which comprises at least the following steps:

[0042] 1) reacting a chromium-containing metal organic framework with diethylenetriamine to obtain an amination intermediate;

[0043] 2) reacting the amination intermediate with trifluoromethanesulfonyl chloride under the action of an acid-binding agent to obtain the receptor;

[0044] 3) Dissolving the receptor and the indicator in a buffer solution to obtain the indicator displacement sensor.

[0045] In the method, the mass ratio of diethylenetriamine to the chromium-containing metal organic framework is (4-6):1, and the mass ratio of trifluoromethanesulfonyl chloride to the amination intermediate is (1.2-1.6):1. In step 1), the reaction temperature is 110°C; in step 2), the reaction temperature is 20-30°C.

[0046] The function of the acid binding agent is to neutralize the acid generated in the reaction. The choice of the acid binding agent is not limited, and commonly used acid binding agents such as sodium hydroxide, potassium hydroxide, triethylamine, etc. can be selected.

[0047] The present invention also provides a method for detecting perfluorooctane sulfonic acid in water, comprising the step of using the above-mentioned indicator replacement sensor for detecting perfluorooctane sulfonic acid to perform detection. The detection method has high selectivity for PFOS, and the fluorescence intensity of PFOS is much higher than that of similar structural interferences (OA, OS, CTAB) at the same concentration and common anions and cations Cl in water. - , SO4 2- , HCO3 - ,CO3 2- , Na + , K + ,Mg 2+ , Ca 2+ .

[0048] The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to the present invention is described below in conjunction with specific embodiments.

[0049] Example 1 Preparation of indicator displacement sensor

[0050] MIL-101(Cr) was prepared by a hydrothermal method using Cr(NO3)3·9H2O and terephthalic acid as precursors. MIL-101(Cr) was weighed and dehydrated in a vacuum oven at 150 °C overnight. The dehydrated MIL-101(Cr) was added to anhydrous toluene to form a uniform suspension, and then diethylenetriamine (DETA) was added to the solution and mixed evenly (the mass ratio of dehydrated MIL-101(Cr) to DETA was controlled to be 1:5), and stirred and refluxed overnight at 110 °C in a nitrogen atmosphere. Centrifugal washing was performed several times, and finally MIL-101-DETA was collected by suction filtration. MIL-101-DETA and a trace amount of triethylamine (as an acid-binding agent to neutralize the acid produced in the reaction, the mass ratio of triethylamine to MIL-101-DETA is 1:300) were added to DMF, mixed evenly, stirred at room temperature, and trifluoromethanesulfonyl chloride was slowly added dropwise (the mass ratio of trifluoromethanesulfonyl chloride to MIL-101-DETA was controlled to be 1.4:1), stirred overnight. Centrifugation was washed several times and dried in a vacuum oven to obtain MIL-101-DETA-TF.

[0051] Sodium 1-pyrenesulfonate (1-PS) dye and MIL-101-DETA-TF were dispersed in acetic acid-sodium acetate (HAc-NaAc) buffer at pH 4, where the concentration of 1-PS was 0.05 μM and the concentration of MIL-101-DETA-TF was 3 μg / mL, forming a supramolecular mixed system (denoted as PS-MIL system) as an indicator displacement sensor.

[0052] The above synthetic route is as follows Figure 1As shown. The SEM image and elemental map of MIL-101-DETA-TF were recorded using an environmental scanning electron microscope-electron spectrometer. The XRD patterns were collected using an X-ray powder diffractometer at room temperature using Cu Kα radiation. The BET surface area and pore size distribution of MIL-101-DETA-TF were determined by nitrogen adsorption / desorption isotherms obtained at –196 °C using a surface area analyzer. The XPS spectrum was obtained using Al Kα radiation from an X-ray photoelectron spectroscopy. The FTIR spectrum of MIL-101-DETA-TF was obtained using a Fourier transform infrared spectrometer.

[0053] Among them, the scanning electron microscope image of MIL-101-DETA-TF is as follows Figure 2 As shown in the image, the crystal morphology of MIL-101-DETA-TF is a flat surface, clear-cut octahedral morphology with an average size of about 300 nm. This morphology is similar to that of the original MIL-101(Cr) and the morphology reported in the literature, indicating that the overall morphology of the material remains unchanged during the functionalization process.

[0054] XRD analysis further confirmed the crystal structure of MIL-101-DETA-TF, such as Figure 3 As shown in a, its diffraction peak matches the characteristic peak of MIL-101(Cr) and the simulated MIL-101(Cr), indicating the successful synthesis of MOF and the complete crystal structure of MOF during the functional modification process. The results of Fourier infrared spectroscopy show ( Figure 3 b) MIL-101-DETA-TF at 1617 and 1399 cm –1 Two strong absorption peaks were observed at 3500-3200 cm-1, corresponding to the asymmetric and symmetric stretching vibrations of the carboxyl group, which are consistent with the characteristic peaks of MIL-101(Cr). –1 Between and 813cm –1 New peaks appeared on the left and right, which were attributed to the stretching vibration and deformation vibration of NH, indicating the successful introduction of amino groups. The chemical composition of the material surface was further verified by XPS analysis ( Figure 3 c). The full XPS spectrum shows that MIL-101-DETA-TF has the same C 1s, O 1s, and Cr 2p peaks as MIL-101(Cr), and new N 1s and F 1s peaks appear, indicating the successful grafting and doping of amino and fluorine functional groups.

[0055] The inventors analyzed the UV-visible absorption spectra of 1-PS, MIL-101-DETA-TF and PS-MIL systems (see Figure 4a), it was found that 1-PS showed a strong absorption peak in the range of 300~360 nm, with the strongest absorption at 342 nm, while MIL-101-DETA-TF had no obvious absorption peak in the UV-visible region. In the PS-MIL system, the observed absorption intensity was significantly weakened relative to 1-PS, indicating that the content of free 1-PS in the system was low. Then, fluorescence spectroscopy analysis (see Figure 4 b) It was found that under the excitation of the maximum absorption wavelength of 342 nm, 1-PS exhibited fluorescence emission in the range of 360~450 nm, and the emission peak at 372 nm was particularly significant, showing a typical Stokes shift. Consistent with the absorption characteristics, MIL-101-DETA-TF produced almost no fluorescence emission. The fluorescence peak position and peak shape of the PS-MIL system were almost the same as those of 1-PS, but the fluorescence intensity was significantly reduced, indicating that the fluorescence source of the PS-MIL system was mainly trace free 1-PS.

[0056] Based on the above results, it can be seen that 1-PS as a sulfonate can ionize in aqueous solution to produce fluorescent anions, and the amino-modified MIL-101-DETA-TF exhibits positive charge and captures 1-PS anions through electrostatic action, thereby significantly reducing the content of free 1-PS in the solution, resulting in a decrease in fluorescence intensity. Therefore, the present invention adopts an indicator replacement analysis strategy to add PFOS that can form anions to the PS-MIL system to replace and release the adsorbed 1-PS, thereby achieving a "fluorescence turn-on" effect, and quantitatively detecting PFOS according to the degree of fluorescence enhancement (for specific detection principles, see Figure 5 ). The sensor has excellent stability and can maintain no significant change in fluorescence intensity under long-term storage in water and light conditions, ensuring the long-term stability of the sensor.

[0057] In order to further understand the mechanism of action between the PS-MIL system and PFOS, the inventors compared the adsorption and release capabilities of unmodified MIL-101(Cr) and bifunctionalized MIL-101-DETA-TF for 1-PS. The results showed that the adsorption capacity of 1-PS and the ability to be exchanged by PFOS after bifunctionalization modification of MOF were significantly stronger than those before modification. Zeta potential analysis showed that MIL-101(Cr) contained almost no positive charge (0.38 mV), while the surface of MIL-101-DETA-TF had a higher positive charge (33.5 mV), indicating that electrostatic interaction plays an important role in the adsorption process of 1-PS. In addition, for MIL-101-DETA-TF, low concentrations of PFOS can also exchange more 1-PS. The water contact angle test shows that the contact angle of fluorinated MIL-101-DETA-TF (103.4°) is much larger than that of MIL-101(Cr) (26.4°), indicating that it is more hydrophobic. Therefore, it is speculated that the enhanced hydrophobicity of fluorinated modification plays a key role in promoting the interaction with PFOS, and further enhances the affinity for PFOS through fluorine-fluorine interaction. In summary, the PS-MIL system mediates the interaction with PFOS through electrostatic interaction, hydrophobic interaction and fluorine-fluorine interaction.

[0058] Example 2 Detection Performance Study

[0059] (1) Sensitivity study

[0060] To evaluate the sensitivity of the sensor to PFOS, different concentration gradients of PFOS (0.005-40 μM, such as 0, 0.002 μM, 0.005 μM, 0.01 μM, 0.02 μM, 0.05 μM) were added to the mixed system PS-MIL in Example 1, and the fluorescence intensity was measured after equilibrium (20 min). To ensure the accuracy and repeatability of the experimental results, three groups of parallel experiments were performed for each concentration.

[0061] The experimental results show that with the increase of PFOS concentration, the fluorescence emission intensity of the PS-MIL system is significantly enhanced, and the maximum enhancement rate exceeds 12 times ( Figure 6 a), and showed a good linear relationship in the concentration range of 0.002-0.05 μM, so PFOS can be quantitatively detected. According to the linear fitting results ( Figure 6b) and the formula for calculating the limit of detection (LOD = 3σ / slope, σ is the standard deviation of the blank sample), the LOD of the PS-MIL system for PFOS is 0.62 nM (310 ng / L), which is significantly better than most reported PFAS fluorescent sensors and lower than the World Health Organization's limit concentration for PFAS in drinking water (500 ng / L). This excellent detection limit may be attributed to the low initial fluorescence value formed by the combination of the positive charge of the amino group of MIL-101-DETA-TF with 1-PS, and the high affinity of the amino and fluorinated modifications of MIL-101-DETA-TF for PFOS.

[0062] (2) Stability study

[0063] In order to study the stability of the sensor in detecting PFOS, PFOS of the corresponding concentration (40 μM) was added to the mixed system PS-MIL in Example 1, and the fluorescence intensity was continuously measured after equilibrium (20 min) for 1 hour at a frequency of once per minute. The stability of the PS-MIL system was further evaluated to ensure that the sensor can be used stably for a long time.

[0064] The fluorescence was detected in water for 7 days. Figure 7 a) It was found that the PS-MIL system and the mixed solution after adding PFOS showed stable fluorescence intensity, indicating that the system has good water stability. Figure 7 b shows that the fluorescence intensity of the PS-MIL system has no obvious fluctuation under 1 hour of continuous excitation light irradiation, reflecting the excellent fluorescence stability.

[0065] (3) Selective research

[0066] The selectivity of the probe to the analyte is an important indicator of detection performance. In order to evaluate the selectivity of the PS-MIL system to PFOS, the effects of various potential interferents on the fluorescence intensity of the system were tested.

[0067] PFOS and a series of interfering substances, including perfluorooctanoic acid (PFOA), octanoic acid (OA), sodium octyl sulfonate (OS), cetyltrimethylammonium bromide (CTAB) and common inorganic salts (NaCl, KCl, MgCl2, CaCl2, Na2SO4, Na2CO3, NaHCO3) at corresponding concentrations (10 μM) were added to the mixed system PS-MIL in Example 1, and the fluorescence intensity was measured after equilibrium (20 min). Three parallel experiments were set for each target.

[0068] The results show that ( Figure 8, where F is the fluorescence intensity after adding PFOS or interfering substances at corresponding concentrations, and F0 is the fluorescence intensity of the system without adding PFOS and interfering substances). The fluorescence enhancement response of the PS-MIL system to PFOS is much higher than that of other substances; although sodium octyl sulfonate (OS) also enhances the fluorescence to a certain extent due to its similar structure to PFOS, the effect is weak. The effect of other substances on the fluorescence intensity is very small, indicating that the PS-MIL system has good selectivity for PFOS.

[0069] Example 3 Detection of PFOS in Reagent Water Samples

[0070] In this study, the sensor in Example 1 was used to detect PFOS in actual water samples. Surface water samples were collected from the Yangtze River in Jiangsu Province, China (N32°09′00″, E118°49′29″). Tap water was taken from the laboratory tap. The water samples were filtered through a 0.22 μm filter membrane and stored in a brown glass bottle at 4 °C for testing. 0.01-0.2 μM PFOS samples were added to the real water samples for spiked testing (measured 20 minutes after adding the sample). The applicability of the established fluorescence "on" system was evaluated by measuring the detection concentration and recovery rate. The test results obtained are listed in Table 1.

[0071] Table 1 Analysis results of PFOS determination in actual water samples

[0072]

[0073] From the above results, we can see that the recovery rates of tap water samples are between 88.2% and 109.6%, and the recovery rates of Yangtze River water samples are between 98.1% and 117.1%, indicating that the PS-MIL system can be used to detect PFOS in actual water samples.

[0074] Example 4: Sensing Conditions

[0075] (1) Research on dye types

[0076] Sodium 1-pyrenesulfonate (1-PS), 1,8-naphthalimide, solvent green 7, and fluorescein were selected as dye optimization objects. The dye and MIL-101-DETA-TF were dispersed in 5 mmol / L acetic acid-sodium acetate (HAc–NaAc) buffer at pH = 5.0, and the maximum fluorescence intensity of each was recorded. MIL-101-DETA-TF was dispersed in water into a suspension and added to the dye solution to form a dye-MOF mixed system. The fluorescence intensity was measured after mixing evenly. PFOS at the corresponding concentration was then added to the dye-MOF mixed system, and the fluorescence intensity was measured after equilibrium. The measurement results were compared and analyzed to explore the influence of the dye type.

[0077] The results show that the adsorption of MIL-101-DETA-TF on 1-PS and solvent green 7 exceeds 95%, which can make the initial fluorescence of the system lower. After further adding different concentrations of PFOS, the dye-MOF system of 1-PS showed a higher replacement rate, while the combination of solvent green 7 and MOF was too strong to be replaced by PFOS, that is, the indicator dye 1-PS in the present invention cannot be replaced at will.

[0078] (2) pH condition investigation

[0079] 1-PS and MIL-101-DETA-TF were dispersed in 5 mmol / L acetic acid-sodium acetate (HAc-NaAc, effective pH range is 3.76-5.76) buffer with pH values ​​of 4.0, 4.5, 5.0, 5.5, and 6.0, and citric acid-sodium citrate buffer with pH values ​​of 3 and 3.5, respectively, to form a PS-MOF hybrid system. PFOS at corresponding concentrations was added to the PS-MOF hybrid system, and the fluorescence intensity (λ ex = 342 nm / λ em = 372 nm, the same below). The measurement results were compared and analyzed to determine the most suitable pH value. The results are shown in Table 2 below.

[0080] Table 2 Fluorescence enhancement response (F / F0) of the PS-MIL system to 0.5 μM and 10 μM PFOS in HAc–NaAc buffer at different pH values

[0081]

[0082] Since the effective pH range of HAc–NaAc buffer is 3.76–5.76 (the pK a The results showed that the effect of citric acid-sodium citrate buffer was not good, which may be because the three carboxyl groups of citric acid enhanced its binding with MIL-101-DETA-TF, inhibited the binding of dye with MOF, and caused the initial fluorescence intensity to be high. Therefore, when the pH was 4±0.3, the fluorescence intensity enhancement (F / F0, where F is the fluorescence intensity after adding PFOS, and F0 is the fluorescence intensity of the system without adding PFOS) was better, and the best effect was achieved at pH 4.

[0083] (3) System concentration study

[0084] Different concentrations of 1-PS and different concentrations of MIL-101-DETA-TF were dispersed in 5 mmol / L acetic acid-sodium acetate (HAc-NaAc) buffer at pH 4.0 to form a PS-MOF mixed system. The corresponding concentration of PFOS was added to the PS-MOF mixed system, and the fluorescence intensity was measured after equilibrium. By comparing the measurement results under different concentration combinations, the influence of the concentrations of 1-PS and MIL-101-DETA-TF was explored, and the results are shown in Table 3 below.

[0085] Table 3 Fluorescence enhancement responses of PS-MIL systems with different initial concentrations to 0.5 μM and 10 μM PFOS

[0086]

[0087] From the above results, it can be seen that when the concentration of 1-PS is 0.05μM and the concentration of MIL-101-DETA-TF is 3μg / mL, it is the optimal system concentration.

[0088] (4) Reaction time study

[0089] Different concentrations of 1-PS and different concentrations of MIL-101-DETA-TF were dispersed in 5 mmol / L acetic acid-sodium acetate (HAc-NaAc) buffer with a pH of 4.0 to form a PS-MOF mixed system. The corresponding concentration of PFOS was added to the PS-MOF mixed system, and the fluorescence intensity was measured while balancing for 1 hour. The appropriate reaction time was determined by comparing and analyzing the measurement results under different reaction times. The results are shown in Table 4 below.

[0090] Table 4

[0091]

[0092] From the above results, it can be seen that the PS-MIL system after adding PFOS reaches fluorescence equilibrium in about 20 min. Therefore, the reaction time should not be less than 20 min, among which 20 min is the best reaction time.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An indicator displacement sensor for detecting perfluorooctane sulfonic acid, characterized in that: The sensor is a supramolecular hybrid system formed by a receptor and an indicator dispersed in a buffer, wherein the receptor is a chromium-containing metal organic framework grafted with a modifying group, and the modifying group is as shown in Formula I, Formula I; The indicator is sodium 1-benzoylsulfonate, and the pH of the buffer solution is 4±0.

3.

2. The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to claim 1, characterized in that: The concentration of the receptor in the indicator displacement sensor is 3±1 μg / mL, and the concentration of the indicator is 0.05±0.02 μM.

3. The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to claim 1, characterized in that: The organic ligand in the chromium-containing metal organic framework is terephthalic acid.

4. The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to any one of claims 1 to 3, characterized in that: The buffer is an acetic acid-sodium acetate buffer with a pH of 4±0.

3.

5. The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to any one of claims 1 to 3, characterized in that: The detection reaction time is not less than 20min.

6. The indicator displacement sensor for detecting perfluorooctane sulfonic acid according to any one of claims 1 to 3, characterized in that: The linear range of the assay was 2-50 nM, and the detection limit was as low as 0.62 nM.

7. The method for preparing the indicator displacement sensor for detecting perfluorooctane sulfonic acid according to any one of claims 1 to 6, characterized in that: At least the following steps are included: 1) reacting a chromium-containing metal organic framework with diethylenetriamine to obtain an amination intermediate; 2) reacting the amination intermediate with trifluoromethanesulfonyl chloride under the action of an acid-binding agent to obtain the receptor; 3) Dissolving the receptor and the indicator in a buffer solution to obtain the indicator displacement sensor.

8. The method for preparing the indicator displacement sensor for detecting perfluorooctane sulfonic acid according to claim 7, characterized in that: The mass ratio of diethylenetriamine to the chromium-containing metal organic framework is (4-6):1, and the mass ratio of trifluoromethanesulfonyl chloride to the amination intermediate is (1.2-1.6):

1.

9. The method for preparing the indicator displacement sensor for detecting perfluorooctane sulfonic acid according to claim 7 or 8, characterized in that: In step 1), the reaction temperature is 110°C; and / or, In step 2), the reaction temperature is 20-30°C.

10. A method for detecting perfluorooctane sulfonic acid in water, characterized in that: The method comprises the step of using the indicator displacement sensor for detecting perfluorooctane sulfonic acid as claimed in any one of claims 1 to 6 to perform detection.

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