A Smart Detection Method for Perfluorinated Compounds Based on Upconversion Fluorescent Silicon Dot Molecular Imprinted Polymers

Abstract

This invention provides an intelligent detection method for perfluorinated compounds based on upconversion fluorescent silicon dot molecularly imprinted polymers. The upconversion fluorescent silicon dot molecularly imprinted polymers specifically recognize perfluorinated compounds; in the presence of PFOA or PFOS, the fluorescence of the molecularly imprinted polymer is quenched or enhanced. Combined with a portable UV device, the RGB values ​​of the molecularly imprinted polymer-perfluorinated compound system are acquired, converted, or detected using a smartphone platform, and the blue fluorescence signal under 700 nm excitation is analyzed, enabling rapid and highly sensitive detection of PFOA and PFOS in environmental water and food. The method for detecting perfluorinated compounds in environmental water and food based on a smartphone sensing platform using upconversion fluorescent silicon dot molecularly imprinted polymers, as constructed in this invention, has advantages such as simple operation, rapid feedback, high sensitivity and repeatability, high stability, and high accuracy. It can intuitively and in real-time achieve rapid determination of perfluorinated compounds in simple systems, broadening the application directions in environmental monitoring.

Description

Technical Field

[0001] This invention belongs to the field of fluorine detection technology, and relates to the detection of perfluorinated compounds in environmental water and food. Specifically, it relates to a method for detecting perfluorinated compounds in environmental water and food by combining an upconversion fluorescent silicon dot molecularly imprinted polymer fluorescent probe with a smartphone sensing platform. Background Technology

[0002] Perfluorinated compounds (PFAS) are a class of man-made chemicals commonly used in the production of waterproof, oil-proof, and stain-resistant products. Long-term exposure to certain PFAS may increase the risk of cancer, particularly liver and testicular cancer. Simultaneously, some PFAS may have adverse effects on the reproductive system, including affecting fertility and causing abnormalities in reproductive organ development. Furthermore, some PFAS may interfere with the normal function of the endocrine system, causing hormonal imbalances, affecting normal physiological processes, weakening the immune system, and increasing the risk of infection and disease. Moreover, perfluorinated compound pollution may also be associated with health problems such as liver damage, thyroid dysfunction, and gallbladder disease. Given the potential hazards of PFAS, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), the U.S. Environmental Protection Agency set a health advisory level of 70 ng / L for PFOS in drinking water in 2016, and the European Food Safety Authority set weekly intake limits of 6 ng / kg for PFOA and 13 ng / kg for PFOS in 2018. However, PFAS levels are initially low, accumulating to a certain concentration before exhibiting toxic effects. Furthermore, PFAS samples have complex matrices and diverse interfering components. Therefore, new technologies are needed to meet the analytical requirements for trace and even ultra-trace levels of PFAS in environmental water bodies and animal-derived foods.

[0003] Given the increasingly stringent requirements for food safety and consumer rights protection, the improvement of testing technologies is both urgent and crucial. Currently, commonly used rapid testing technologies for food safety both domestically and internationally include chemical colorimetric analysis, molecular biological analysis, immunological analysis, as well as biosensors and nanotechnology. Traditional testing technologies primarily rely on instrumental analysis, but these suffer from drawbacks such as large equipment requirements, complex operation, long processing times, and high costs, making it difficult to meet the demands for timely and rapid on-site safety monitoring. Subsequent methods, such as the paper disc method and reagent kits (cards), still suffer from relatively low method sensitivity.

[0004] Molecular imprinting technology, with its predictive, recognizable, and practical characteristics, has been widely applied in many fields, such as chromatographic separation, solid-phase extraction, biomimetic sensing, enzyme-mimicking, and clinical drug analysis. Currently, many scientists combine nanocrystalline silicon with molecular imprinting technology for detection and imaging. However, traditional molecularly imprinted fluorescent probes are only suitable for the determination of PFAS in simple matrices (such as water and serum), and are inadequate for complex matrices (such as animal-derived foods). When the excitation wavelength of the fluorescent probe reaches the near-infrared region (upconversion characteristic), the high background of complex matrices that reduces sensitivity can be overcome, thus achieving efficient and sensitive recognition of targets in complex matrices.

[0005] A novel method for detecting target compounds in simple and complex systems was developed by combining silicon quantum dot-based molecularly imprinted polymers with smartphones. This method enables quantitative analysis of perfluorinated compounds in water samples by simply identifying the RGB values ​​of the samples within a portable UV device, meeting the needs of real-time monitoring and providing technical support for environmental and food safety testing applications. Summary of the Invention

[0006] This invention addresses the aforementioned problems by providing a novel smartphone sensing platform for the detection of perfluorinated compounds, based on upconversion fluorescent silicon dot molecularly imprinted polymer fluorescent probes, enabling rapid detection of perfluorinated compounds in water and food. This invention utilizes the specific recognition of perfluorinated compounds by upconversion fluorescent silicon dot molecularly imprinted polymers; in the presence of PFOA or PFOS, the fluorescence of the molecularly imprinted polymer is quenched or enhanced. Combined with a portable UV device, the RGB values ​​of the molecularly imprinted polymer-perfluorinated compound system are acquired and converted via a smartphone platform, achieving rapid and highly sensitive detection of PFOA and PFOS in environmental water and food.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides the application of upconversion fluorescent silicon dot molecularly imprinted polymers in the detection of perfluorinated compounds.

[0009] Preferably, the perfluorinated compound is a perfluorinated compound found in environmental water bodies and food, including at least perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS).

[0010] In a second aspect, the present invention provides a method for preparing a molecularly imprinted polymer fluorescent probe based on the upconversion fluorescent silicon dot molecularly imprinted polymer used in the above applications, as follows:

[0011] (1) Add the template molecule PFOA or PFOS and the silicon source to an organic solvent, then add the functional monomer APTES, and stir magnetically to make them fully contacted to obtain a homogeneous mixed solution.

[0012] (2) After a certain period of time, add crosslinking agent TEOS to the mixed solution and continue stirring to make the reactants mix evenly;

[0013] (3) Add the catalyst ammonia water to the mixed solution in step (2) and continue stirring for a certain period of time to make the reactants evenly mixed;

[0014] (4) Transfer the solution from step (3) to a centrifuge and centrifuge at a certain temperature for a certain time to obtain the eluted molecularly imprinted polymer fluorescent probe;

[0015] (5) Continue stirring and eluting with methanol as the eluent for a certain period of time, centrifuge the solution, remove the supernatant, and obtain the eluted molecularly imprinted polymer precipitate;

[0016] (6) Place the precipitate that has been eluted in step (5) into a vacuum drying oven to dry it, and finally obtain the molecularly imprinted polymer fluorescent probe.

[0017] Preferably, the mass-volume ratio of the template molecule, silicon source, anhydrous ethanol, APTES and crosslinking agent TEOS is 1:4:4:9:5~9, and most preferably 1:4:4:9.

[0018] Furthermore, in step (1), the silicon source is selected from silicon quantum dots; the organic solvent is selected from any one or a mixture of anhydrous ethanol, methanol, n-propanol, isopropanol, acetone, tetrahydrofuran, and ethyl acetate.

[0019] The magnetic stirring time in step (1) is 1-2 h (preferably 1 h), the stirring time in step (2) is 30-60 min (preferably 30 min), and the magnetic stirring time in step (3) is 12-15 h (preferably 12 h).

[0020] In step (4), the centrifugation temperature is 4 ℃ and the centrifugation time is 45-60 min, preferably centrifuged 3 times, 15 min each time;

[0021] In step (5), the magnetic stirring time is 12-15 h (preferably 12 h), the centrifugation temperature is 4 ℃, and the centrifugation time is 45-60 min. It is preferred to centrifuge 3 times, 15 min each time.

[0022] In step (6), the drying temperature is 60 ℃ and the drying time is 8-12 h, preferably 8 h.

[0023] In a third aspect, the present invention provides a molecularly imprinted polymer fluorescent probe for the detection of perfluorinated compounds, prepared by the above method. Detection results show that the prepared fluorescent probe has abundant surface functional groups, good fluorescence performance, strong photostability, and good selectivity for PFOA and PFOS.

[0024] In a fourth aspect, this invention provides a method for detecting perfluorinated compounds based on upconversion fluorescent silicon dot molecularly imprinted polymers. This method can be implemented in two ways. The first way combines the aforementioned molecularly imprinted polymer fluorescent probe with a mobile intelligent sensing platform. The molecularly imprinted polymer fluorescent probe captures the perfluorinated compound, and the detection is then performed by combining the grayscale value converted from the RGB values ​​of the mobile intelligent sensing platform. The steps are as follows:

[0025] After mixing the molecularly imprinted polymer with the water to be tested, the mixture is irradiated with ultraviolet light of a specific wavelength (365 nm). The RGB values ​​are obtained by color recognition software of a mobile intelligent sensing platform, converted into gray values, and then the concentration of perfluorinated compounds in the water is quantitatively determined.

[0026] The formula for converting RGB values ​​to grayscale values ​​is: grayscale value PFOA = G / B; grayscale value PFOS = R*0.299 + G*0.587 + B*0.144.

[0027] Preferably, the sensing platform includes an ultraviolet dark chamber device and color recognition software installed on a mobile electronic product. The ultraviolet dark chamber device includes an imaging port at the top, a power switch next to the imaging port, a sample inlet at the front end, a sample cell inside the sample inlet, and a power socket.

[0028] The second method is to detect upconversion fluorescence: after mixing the above-mentioned molecularly imprinted polymer fluorescent probe with the water body to be tested, the blue fluorescence signal under 700 nm excitation is detected and analyzed, thereby realizing the qualitative and quantitative analysis of the target analyte.

[0029] Both of these detection methods can be used to detect PFOA concentrations of 0–5 µM and PFOS concentrations of 0–3.5 µM in water.

[0030] The beneficial protections and effects of this invention are as follows:

[0031] The silicon quantum dot molecularly imprinted polymer prepared in this invention exhibits excellent fluorescence properties, with fluorescence quenching in the presence of PFOA and enhancement in the presence of PFOS. The method for detecting perfluorinated compounds in environmental water and food based on a silicon quantum dot molecularly imprinted polymer sensing platform offers advantages such as simple operation, rapid feedback, high sensitivity and repeatability, good stability, and high accuracy. It enables direct and real-time rapid determination of perfluorinated compounds in environmental and food water samples, broadening the application directions for silicon quantum dot molecularly imprinted polymer detection. Attached Figure Description

[0032] Figure 1 A schematic diagram of the research process of this invention is shown.

[0033] Figure 2 Selectivity test results for PFOA are shown, where (A) shows the selectivity test results for PFOA with other ions and analogs; and (B) shows the interference resistance test results.

[0034] Figure 3 The results of selective experiments on PFOS are shown, in which (A) shows the selective experiments on PFOS with other ions and analogs; and (B) shows the results of interference resistance experiments.

[0035] Figure 4 The diagram shows the structure and detection diagram of the portable ultraviolet device used in this invention.

[0036] Figure 5 The results of PFOA detection in the examples are shown in the figure; where: (A) fluorescence images of silicon-based molecularly imprinted polymer solution and silicon-based molecularly imprinted polymer solution-PFOA solution in a 365 nm ultraviolet dark chamber; (B) linear relationship between G / B and PFOA concentration.

[0037] Figure 6 This is a fluorescence intensity quenching spectrum of silicon-based molecularly imprinted polymers at a wavelength of 700 nm, as a function of PFOA concentration.

[0038] Figure 7 This is a spectrum showing the increase in fluorescence intensity of silicon-based molecularly imprinted polymers with PFOS concentration at a wavelength of 700 nm.

[0039] Figure 8 This is a graph showing the linear relationship between grayscale value and PFOS concentration in the example. Detailed Implementation

[0040] The following embodiments and experimental examples further illustrate the present invention and should not be construed as limiting the invention. The embodiments do not include a detailed description of conventional methods, which are well known to those skilled in the art and described in numerous publications.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention, and the preferred embodiments and materials described in the specific implementation are for illustrative purposes only.

[0042] Unless otherwise specified, the experimental methods described in the following examples are generally performed under standard conditions or as recommended by the manufacturer.

[0043] Figure 1A schematic diagram of the research process of this invention is shown below:

[0044] I. Preparation of Molecularly Imprinted Polymer Fluorescent Probes

[0045] 1) Add the template molecule PFOA or PFOS and the silicon source to the solvent anhydrous ethanol, and then add the functional monomer APTES. The ratio of template molecule to silicon source to anhydrous ethanol to functional monomer APTES is 1:4:4:9. Stir magnetically to ensure full contact and obtain a homogeneous mixed solution.

[0046] 2) After 1 h, add 25-45 μL of crosslinking agent TEOS to the mixed solution and continue stirring for 30 min to mix the reactants evenly;

[0047] 3) Add 50 μL of catalyst ammonia water to the mixed solution and continue stirring for 12 h to ensure that the reactants are mixed evenly;

[0048] 4) Transfer the solution to a centrifuge at 10,000 rpm and centrifuge at 4 °C for 15 min. Repeat this process three times to obtain the eluted molecularly imprinted polymer fluorescent probe.

[0049] 5) Continue stirring and eluting with methanol as the eluent for 12 h. Centrifuge the solution at 4 °C for 15 min, repeat three times, remove the supernatant, and obtain the eluted molecularly imprinted polymer precipitate.

[0050] 6) Place the eluted precipitate in a vacuum drying oven and dry it at 60 °C for 8 h to obtain the molecularly imprinted polymer fluorescent probe.

[0051] II. Detection of perfluorinated compounds in water

[0052] Take a certain amount of silicon quantum dot molecularly imprinted polymer and add Cl - F - NO3 - CO3 2- SO4 2- Na + K + Ca 2+ Mg 2+ Ionic solutions and some perfluorinated compound analogue solutions were diluted to 500 μL with buffer solution, allowed to stand for 15-20 min, and the selectivity was tested. Figure 2 A, 3A) and anti-interference ( Figure 2 (B, 3B) The results showed that only PFOA and PFOS quenched the fluorescence of the silicon dots, demonstrating their good selectivity and anti-interference ability.

[0053] III. Detection of PFOA and PFOS at Different Concentrations

[0054] 1. Detection using a 365 nm ultraviolet darkroom combined with a smartphone

[0055] A certain amount of silicon quantum dot molecularly imprinted polymer was taken, and PFOA and PFOS solutions were added. The buffer solution was adjusted to 500 μL so that the concentrations of PFOA and PFOS in the test solution were 1 µM, 2 µM, 3 µM, 4 µM, and 5 µM, respectively. After standing for 15 min, the prepared solution was placed in a UV dark chamber and irradiated with a 365 nm UV lamp. The RGB values ​​were obtained by the color recognition software of a smartphone and then converted into grayscale values ​​and ratios.

[0056] See the structure of the ultraviolet darkroom equipment. Figure 4 It includes a camera port 1 at the top for easy mobile phone shooting, a power switch 2 next to the camera port 1, a sample inlet 3 at the front end, a sample cell 4 inside the sample inlet, and a power socket 5 on the right side of the device.

[0057] A molecularly imprinted polymer-PFOA / PFOS system solution was placed in a sample cell. A color recognition app on a mobile phone was used to capture the RGB values. Based on the grayscale value formula: Grayscale value... PFOA =G / B; Gray value PFOS =R*0.299+G*0.587+B*0.144 to calculate the gray value, and then obtain the PFOA or PFOS solution concentration according to the standard curve method.

[0058] Following the methods described in the above embodiments, silicon dot nanofluorescent materials were prepared for upconversion fluorescence detection of PFOA in water, comprising: 1) silicon-based molecularly imprinted polymer, 2) silicon-based molecularly imprinted polymer + 1 µM PFOA, 3) silicon-based molecularly imprinted polymer + 2 µM PFOA, 4) silicon-based molecularly imprinted polymer + 3 µM PFOA, 5) silicon-based molecularly imprinted polymer + 4 µM PFOA, and 6) silicon-based molecularly imprinted polymer + 5 µM PFOA. The results are as follows: Figure 5 As shown: its emission spectrum and the corresponding fluorescence image in a 365 nm ultraviolet dark chamber are shown in [reference needed]. Figure 5 A. The linear relationship between grayscale values ​​and PFOA and PFOS concentrations, and the corresponding 365 nm UV irradiation photos at each concentration point, can be found in [reference needed]. Figure 5 B, R PFOA 2 =0.9967.

[0059] 2. Detection of upconversion fluorescence at 700 nm

[0060] The aforementioned silicon-based molecularly imprinted polymer and mixtures of different concentrations of PFOA were irradiated at a wavelength of 700 nm, and blue fluorescence signals at this wavelength were collected. The fluorescence intensity quenching spectrum of the silicon-based molecularly imprinted polymer as a function of PFOA concentration is shown in [reference needed]. Figure 6 .

[0061] The following polymers were prepared according to the methods described in the above embodiments: 1) silicon-based molecularly imprinted polymer, 2) silicon-based molecularly imprinted polymer + 1 µM PFOS, 3) silicon-based molecularly imprinted polymer + 1.5 µM PFOS, 4) silicon-based molecularly imprinted polymer + 2 µM PFOS, 5) silicon-based molecularly imprinted polymer + 2.5 µM PFOS, 6) silicon-based molecularly imprinted polymer + 3 µM PFOS, and 7) silicon-based molecularly imprinted polymer + 3.5 µM PFOS. PFOS in water was detected using upconversion fluorescence based on silicon dot nanofluorescent materials. Irradiation was performed at a wavelength of 700 nm, and blue fluorescence signals at this wavelength were collected. The fluorescence intensity of the silicon-based molecularly imprinted polymer increased with PFOS concentration as shown in the graph below. Figure 7 As shown; the linear relationship between grayscale value and PFOS concentration is shown in the figure. Figure 8 R PFOS 2 =0.993.

[0062] IV. Actual Sample Testing

[0063] The upconversion fluorescence method based on silicon-based molecularly imprinted polymers, established above, was used to detect PFOA in tap water, seawater, milk, and orange juice, and spiked recovery experiments were conducted. The results are shown in Table 1 below. Simultaneously, the spiked recovery experiment of PFOA detection in actual samples was performed using the established smartphone method based on silicon-based molecularly imprinted polymers, and the results are shown in Table 2 below. The results confirm that the method of the present invention has high accuracy.

[0064] Table 1. Spiked recovery experiments of PFOA detection in real samples using the established upconversion fluorescence method based on silicon-based molecularly imprinted polymers.

[0065]

[0066] Table 2. Spiked recovery experiments of the established smartphone method based on silicon-based molecularly imprinted polymers in real samples for the detection of PFOA.

[0067]

[0068] Furthermore, spiked recovery experiments were conducted on tap water and river water based on the established upconversion fluorescence method. The specific results are shown in Table 3 below.

[0069] Table 3. Spiked recovery experiments of PFOA detection in real samples using the established upconversion fluorescence method based on silicon-based molecularly imprinted polymers.

[0070]

[0071] The above experimental results demonstrate that the method for detecting perfluorinated compounds in environmental water and food based on silicon quantum dot molecularly imprinted polymer fluorescent probes in this invention has high sensitivity, repeatability, stability, and accuracy, and can directly achieve rapid determination of PFOA and PFOS in environmental and food water samples.

[0072] The undescribed parts of this invention are the same as or implemented using existing technology. The applicant declares that this invention is illustrated through the above embodiments, but the invention is not limited to the above detailed methods, i.e., it does not mean that the invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for preparing a molecularly imprinted polymer fluorescent probe for detecting perfluorinated compounds, characterized by, The perfluorinated compound is selected from perfluorooctanoic acid or perfluorooctane sulfonic acid; the molecularly imprinted polymer fluorescent probe is a fluorescent probe based on an upconversion fluorescent silicon dot molecularly imprinted polymer, and the preparation method includes the following steps: (1) Add template molecules PFOA or PFOS and silicon quantum dots to an organic solvent, then add functional monomer APTES, and stir magnetically to make them fully contacted to obtain a homogeneous mixed solution. (2) After a certain period of time, add crosslinking agent TEOS to the mixed solution and continue stirring to make the reactants mix evenly; (3) Add the catalyst ammonia water to the mixed solution in step (2) and continue stirring for a certain period of time to make the reactants evenly mixed; (4) Transfer the solution from step (3) to a centrifuge and centrifuge at a certain temperature for a certain time to obtain the eluted molecularly imprinted polymer fluorescent probe; (5) Continue stirring and eluting with methanol as the eluent for a certain period of time, centrifuge the solution, remove the supernatant, and obtain the eluted molecularly imprinted polymer precipitate; (6) Place the precipitate that has been eluted in step (5) into a vacuum drying oven to dry it, and finally obtain the molecularly imprinted polymer fluorescent probe.

2. The production method according to claim 1, characterized by, The perfluorinated compounds are those found in environmental water bodies and food.

3. The preparation method according to claim 1, characterized in that: wherein, The mass-volume ratio of the template molecule, silicon quantum dots, organic solvent, APTES, and crosslinking agent TEOS is 1:4:4:9:5~9.

4. The preparation method according to claim 1, characterized in that: in, In step (1), the organic solvent is selected from any one or a mixture of anhydrous ethanol, methanol, n-propanol, isopropanol, acetone, tetrahydrofuran, and ethyl acetate; The magnetic stirring time in step (1) is 1-2 h, the stirring time in step (2) is 30-60 min, and the magnetic stirring time in step (3) is 12-15 h.

5. The preparation method according to claim 1, characterized in that: in, In step (4), the centrifugation temperature is 4 ℃ and the centrifugation time is 45-60 min; In step (5), the magnetic stirring time is 12-15 h, the centrifugation temperature is 4 ℃, and the centrifugation time is 45-60 min; In step (6), the drying temperature is 60 ℃ and the drying time is 8-12 h.

6. A molecularly imprinted polymer fluorescent probe, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

7. A method for detecting perfluorinated compounds based on upconversion fluorescent silicon dot molecularly imprinted polymers, characterized in that, Implement using any of the following methods: Method 1: This method combines the molecularly imprinted polymer fluorescent probe described in claim 6 with a mobile intelligent sensing platform. The molecularly imprinted polymer fluorescent probe captures perfluorinated compounds, and the detection is then performed by combining the grayscale values ​​converted from the RGB values ​​of the mobile intelligent sensing platform. The steps are as follows: After mixing the molecularly imprinted polymer with the water sample, the mixture was irradiated with 365 nm ultraviolet light. The RGB values ​​were then obtained using color recognition software on a mobile intelligent sensing platform, converted to grayscale values, and the concentration of perfluorinated compounds in the water was quantitatively determined. The formula for converting the RGB value into a gray value is: gray value = R*0.299+G*0.587+B*0.144 PFOA = G / B; gray value PFOS = R*0.299+G*0.587+B*0.144; Method 2: After mixing the molecularly imprinted polymer fluorescent probe of claim 6 with the water body to be tested, the blue fluorescence signal under 700 nm excitation is detected and analyzed.

8. The detection method according to claim 7, characterized in that, The sensing platform includes an ultraviolet dark chamber device and color recognition software installed on a mobile electronic product. The ultraviolet dark chamber device includes an imaging port at the top, a power switch next to the imaging port, a sample inlet at the front end, a sample cell inside the sample inlet, and a power socket.

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