Method for detecting aflatoxin by using electrospun nanofiber membrane loaded with NH2-MIL-53(AI)

Abstract

A method for detecting aflatoxin (AFB1) by using an electro-spun nano-fibre membrane loaded with NH2-MIL-53(Al) comprises; dropwise adding a sample solution to be detected to the loaded membrane; incu

Description

The present disclosure belongs to the technical field of aflatoxin detection, and particularly relates to a method for detecting aflatoxin by using an electrospun nanofiber membrane loaded with NH2-MIL-53(A1). Description of Related Art It is of significant importance to create an economical, sensitive, simple, convenient, and rapid method for detecting aflatoxin Bi (AFBi), a type of most harmful and common mycotoxin. The current methods for detecting AFBi primarily include enzyme-linked immunosorbent assay, high performance liquid chromatography, membrane flow immunoassay, immunoassay chromatography, and an electrochemical method. Although being sensitive to AFBi sensing, chromatography features a high cost, a complicated sample preparation process, and high technical requirements for users. Incorporation of biomolecules also makes the immunoassay chromatography less robust. These methods also have some common disadvantages, such as a costly apparatus and complicated and time-consuming operations. Under the limitations of these disadvantages, these methods may not be applied to developing countries in a wide range. With high sensitivity, broad substrate selectivity, good reproducibility, simple apparatuses, etc., luminescent metal-organic frameworks (LMOFs), a new type of chemical sensors, have drawn much attention. The detection of AFBi through MOF-based sensors has been reported occasionally so far. However, the sensing mechanism of these sensors is luminescence quenching (i.e. fluorescence quenching), commonly referred to as “turn-off’ sensing, which lacks the advantages of those sensors operating on the basis of the luminescence “turn-on” principle, such as excellent sensitivity, selectivity, and practicality. Therefore, the development of a robust and efficient MOF-based fluorescence “turn-on” sensor for detecting AFBi is more meaningful and highly-demanded. BRIEF SUMMARY OF THE INVENTION Aiming at the problems in the prior art, an objective of the present disclosure is to provide a method for detecting aflatoxin by using an electrospun nanofiber membrane loaded with NH2-MIL-53(A1). In order to realize the above objective, the present disclosure employs the technical solution as follows: A method for preparing NH2-MIL-53(A1) is as follows: (1) dissolving AlCh 6H2O in ultrapure water, adding NH2-BDC under stirring, and stirring a resulting solution to obtain “solution 1”; (2) dissolving urea in ultrapure water to obtain “solution 2”; (3) slowly adding “solution 2” to “solution 1” under continuous stirring, evenly stirring and mixing a mixed solution, then maintaining a resulting solution at 150°C for 5 h, and naturally cooling an obtained solution to a room temperature, so as to obtain a yellow solid; (4) washing the yellow solid three times with deionized water, dispersing a yellow solid washed in DMF through centrifugal separation, stirring a suspension at the room temperature without light for 24 h, and then removing the DMF through centrifugation; and dispersing the solid in methanol, stirring a resulting solution at the room temperature without light for 24 h, and then removing the methanol through centrifugation; (5) vacuum-drying a product washed in step (4) at 50°C for 24 h to obtain the NH2-MIL-53(A1) powder. The application of NH2-MIL-53(A1) in detecting aflatoxin is as follows. A method for detecting aflatoxin includes: preparing NH2-MIL-53(A1) into a dispersion; adding a sample solution to be detected to the dispersion; incubating a mixed solution at the room temperature; then recording a fluorescence intensity of an incubated mixed solution at 430 nm under excitation of 330 nm; and calculating a content of the aflatoxin in a sample to be detected through comparison with a standard curve between a fluorescence intensity and an aflatoxin concentration. The application of NH2-MIL-53(A1) in preparing a reagent for detecting aflatoxin is as follows. An electrospun nanofiber membrane loaded with NH2-MIL-53(A1) is formed by preparing NH2-MIL-53(A1) into a nanofiber membrane through an electrospinning method. In a specific example, a method for preparing the electrospun nanofiber membrane loaded with NH2-MIL-53(A1) is as follows: dissolving the NH2-MIL-53(A1) powder and polyacrylonitrile (PAN) in DMF, and vigorously stirring a resulting solution at 90°C for 2 h to obtain a NH2-MIL-53(A1) / PAN solution; and filling a disposable needle tube with the NH2-MIL-53(A1) / PAN solution, and putting the disposable needle tube filled with the NH2-MIL-53(A1) / PAN solution into an electrospinning apparatus for spinning. The application of the electrospun nanofiber membrane loaded with NH2-MIL-53(A1) in detecting aflatoxin may be configured to detect aflatoxin in a cereal or a peanut. The method for detecting aflatoxin by using the electrospun nanofiber membrane loaded with NH2-MIL-53(A1) includes dropwise adding a sample solution to be detected to the electrospun nanofiber membrane loaded with NH2-MIL-53(A1); incubating an electrospun nanofiber membrane added with NH2-MIL-53(A1) at the room temperature; then taking a fluorescence photo of a nanofiber; rapidly acquiring G data and B data of the photo through color recognition software; calculating a value of G / B, and substituting the value into a relation curve between G / B and an aflatoxin concentration; and calculating an aflatoxin concentration in the substance. In a specific example, the sample solution to be detected is prepared through a method as follows: mixing a ground sample with acetonitrile; rotatably evaporating a supernatant to make the supernatant approximately dry; dispersing a supernatant approximately dry in a poly butylene succinate (PBS) solution; and centrifuging a resulting solution, and filtering a centrifuged solution through a filter membrane of 0.22 gm to obtain the sample solution to be detected. The technical solutions of the present disclosure have the advantages as follows: The present disclosure provides a fluorescence detection platform based on a low-concentration aluminum metal-organic framework for detecting AFBi. Specifically, NH2-MIL-53(A1) is used as a fluorescence platform. NH2-MIL-53(A1) has a respiratory effect and stability in an aqueous solution. Amino groups may interact with AFBi through hydrogen bonds, acid-base effects, coordination bonds, etc. On the basis of the sensitivity and selectivity of NH2-MIL-53(A1) to AFBi, a new method is provided for rapidly detecting AFBi in food. In addition, a portable flexible sensor is prepared by loading a fluorescence probe on the electrospun nanofiber membrane. After the flexible sensor is successfully combined with the smart phone, a detection cost and time are greatly reduced. Therefore, a promising method is provided for on-site qualitative recognition and quantitative detection of AFBi. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Fig. 1 shows a principle for detecting aflatoxin Bi on the basis of NH2-MIL-53(A1); Fig. 2 shows stability of a NH2-MIL-53(A1) solution; Fig. 3 shows an emission spectrum NH2-MIL-53(A1); Fig. 4 shows an excitation spectrum, an emission spectrum, and an ultraviolet absorption spectrum of NH2-MIL-53(A1); Fig. 5 shows an X-ray diffraction pattern of NH2-MIL-53(A1); Fig. 6 shows a Fourier transform infrared spectra of NH2-MIL-53(A1) and NH2-BDC; Fig. 7 shows a thermogravimetric analysis of NH2-MIL-53(A1); Fig. 8 shows ultraviolet absorption spectra of NH2-MIL-53(A1) and NH2-MIL-53(A1)+AFBi; Fig. 9 shows a sensitivity graph and a color change graph of fluorescence detection of AFBi; Fig. 10 shows a linear relation graph of an AFBi concentration; Fig. 11 shows a linear relation curve between G / B and an AFBi concentration; Fig. 12 shows a diagram of detecting AFBi through an electrospun nanofiber; Fig. 13 shows specificity of NH2-MIL-53(A1); and Fig. 14 shows immunity of NH2-MIL-53(A1). DETAILED DESCRIPTION OF THE INVENTION The terms used in the present disclosure generally have the meanings commonly understood by those of ordinary skill in the art unless otherwise specified. The present disclosure is further described in detail below with reference to specific examples and data. The following examples are merely intended to illustrate the present disclosure, and are not to limit the scope of the present disclosure in any way. The principle for detecting aflatoxin Bi of the present disclosure is as shown in Fig. 1. AlCh 6H2O and NH2-BDC were prepared into NH2-MIL-53(A1) in a urea solution. NH2-MIL-53(A1) prepared had the strongest fluorescence emission at 430 nm under an excitation wavelength of 330 nm. NH2-MIL-53(A1) prepared may be directly dispersed in a poly butylene succinate (PBS) solution to prepare a dispersion; a sample to be detected was added to the dispersion; a fluorescence intensity at 430 nm was measured if the sample to be detected contained AFBi; and an AFBi concentration in the sample to be detected was acquired through comparison with a standard curve between a fluorescence intensity and an AFBi concentration. Alternatively, NH2-MIL-53(A1) prepared was prepared into an electrospun nanofiber membrane loaded with NH2-MIL-53(A1) through an electrospinning method; a sample solution to be detected was dropwise added to the nanofiber membrane; and a fluorescence photo of a nanofiber added with the sample solution to be detected was taken through a smart phone. Different color pictures may be converted into three values RGB through a color recognition application (APP), and a graph was created through a ratio of G to B. G data and B data of these photos were rapidly acquired through color recognition APP, a value of G / B was calculated and substituted into a linear relation curve between G / B and an AFBi concentration, and an AFBi concentration in the substance was calculated. Example 1 NH2-MIL-53(A1) was prepared as follows: First, 1.448 g of AlCh 6H2O were dissolved in 30 mL of ultrapure water, 1.088 g of NH2-BDC were added under magnetic stirring, and a resulting solution was stirred for 30 min to obtain “solution 1”. In another container, 0.576 g of urea was dissolved in 10 mL of ultrapure water to obtain “solution 2”. Then, “solution 2” was slowly added to “solution 1” under continuous stirring at a room temperature, and a mixed solution was stirred for 30 min. A mixture was transferred to a polytetrafluoroethylene-lined reaction kettle and maintained at 150°C for 5 h. Then, a resulting mixture was naturally cooled to the room temperature. A yellow solid was washed three times with deionized water, and a yellow solid washed was centrifugally separated (at 12000 rpm for 10 min). A yellow solid centrifugally separated was dispersed in 40 mL of dimethyl formamide (DMF), and a suspension was stirred at the room temperature without light for 24 h. Then, the DMF was removed through centrifugation. The solid was dispersed in 40 mL of methanol, and a resulting solution was stirred at the room temperature without light for 24 h. Then, the methanol was removed through centrifugation. Finally, a product was vacuum-dried at 50°C for 24 h. A product vacuum-dried was collected to obtain NH2-MIL-53(Al) powder. An emission spectrum of NH2-MIL-53(A1) was measured as follows: fluorescence spectra of a 0.55 pg / mL NH2-MIL-53(A1) solution were record independently under excitation of 300 nm-360 nm. The results are shown in Fig. 2: when an excitation wavelength was 330 nm, it can be seen that a maximum peak was reached at 430 nm. Therefore, 330 nm is an optimal excitation wavelength for NH2-MIL-53(A1). Specific methods for determining the effects of different pH values, temperatures, ultraviolet irradiation, and storage times on the stability of a NH2-MIL-53(A1) solution were as follows: For pHs: NH2-MIL-53(A1) solutions were diluted to 0.55 pg / mL through solutions having different pHs, fluorescence intensities were tested through a microplate reader under excitation of 330 nm, and a fluorescence intensity at the peak 430 nm was recorded. For temperatures: 0.55 pg / mL NH2-MIL-53(A1) solutions were placed at different temperatures, fluorescence intensities were tested through the microplate reader under excitation of 330 nm, and a fluorescence intensity at the peak 430 nm was recorded. For ultraviolet irradiation: a 0.55 pg / mL NH2-MIL-53(A1) solution was irradiated with an ultraviolet light, a fluorescence intensity was tested through the microplate reader under excitation of 330 nm, and a fluorescence intensity at the peak 430 nm was recorded. For long-term storage: a 0.55 pg / mL NH2-MIL-53(A1) solution was placed at the room temperature, fluorescence stability of the solution was tested at day 1, 3, 5, 7, 15, and 30, and a fluorescence intensity was tested through the microplate reader under excitation of 330 nm. The stability of the NH2-MIL-53(A1) solution is as shown in Fig. 3: through the research on the fluorescence intensities of the NH2-MIL-53(A1) solution under different pHs, temperatures, ultraviolet irradiation, and long-term storage, it was found that the fluorescence intensity of the NH2-MIL-53(A1) solution maintain stable. It is shown that the NH2-MIL-53(A1) solution has excellent optical properties, and thus can be better configured to detect AFBi subsequently. An excitation spectrum, an emission spectrum, and an ultraviolet absorption spectrum of NH2-MIL-53(A1) were determined as follows: For the excitation spectrum: a 0.55 pg / mL NH2-MIL-53(A1) solution was added to a 96-well black microplate reader plate, and the excitation spectrum was recorded under emission of 430 nm. For the emission spectrum: a 0.55 pg / mL NH2-MIL-53(A1) solution was added to a 96-well black microplate reader plate, and the emission spectrum under excitation of 330 nm was recorded. For the ultraviolet absorption spectrum: 2 mL of a NH2-MIL-53(A1) solution were added to a quartz cuvette, the quartz cuvette added with the NH2-MIL-53(A1) solution was put into an ultraviolet spectrophotometer, and the ultraviolet absorption spectrum within a wavelength range of 200 nm-600 nm was recorded. The results that characterize the optical properties of NH2-MIL-53(A1) are as shown in Fig. 4. The ultraviolet absorption spectrum showed two characteristic absorption peaks at 220 nm and 330 nm. The absorption peak at 220 nm was caused by the 7t-7t* transition of a C=C group or the n-7t* transition of a C=O group. The characteristic absorption peak at 330 nm was attributed to the n-u* transition of the C=O / C-N group, which is consistent with the optimal excitation wavelength of the fluorescence spectrum. A method for determining an X-ray diffraction (XRD) pattern of NH2-MIL-53(A1) was as follows: an XRD pattern of NH2-MIL-53(A1) powder was measured through an X-ray diffractometer. The NH2-MIL-53(A1) powder was finely ground, an appropriate amount of the powder was put into a glass plate with a groove, and the glass plate with the powder was put into an instrument for testing. The results are as shown in Fig. 5: a precursor of a NH2-MIL-53(A1) nanosheet prepared was well crystallized. Typical peaks at 8.8°, 10.4°, 15.0°, 17.5°, 20.0°, and 26.4°also demonstrated that a material was successfully prepared. A method for measuring Fourier transform infrared spectra of NH2-MIL-53(A1) and NH2-BDC was as follows: the infrared spectra of NH2-MIL-53(A1) powder and NH2-BDC powder were measured through a Fourier transform infrared spectrometer. Appropriate amounts of the above two kinds of powder were placed on the instrument, and the infrared spectra were recorded after the background interference of air was eliminated. The results are as shown in Fig. 6: spectral bands at 3504 cm'1 and 3390 cm'1 corresponded to asymmetric stretching vibration of an N-H bond. It was indicated that the NH2-MIL-53(A1) nanosheets contained plenty of hydroxyl groups, which contributed to their remarkable water solubility. In addition, a new spectral band at 1000 cm’1-! 100 cm’1 was caused by stretching vibration of an Al-0 bond, further indicating that an atom O in NH2-BDC coordinated with Al3+ to form a metal-organic framework. A method for thermogravimetric analysis (TGA) of NH2-MIL-53(A1) was performed through a differential scanning calorimetry. First, at most 0.5 g of NH2-MIL-53(A1) powder was placed into a small crucible, the small crucible with the powder was put into the instrument, and a temperature range was set to 30°C-800°C, so as to test the thermal stability of the powder. The results are as shown in Fig. 7: through the research on the thermal stability of NH2-MIL-53(A1), TGA data revealed that the powder was thermally stable at a temperature up to 280°C. Example 2 An electrospun nanofiber membrane loaded with NH2-MIL-53(A1) is prepared as follows: First, 10 mg of the NH2-MIL-53(A1) powder prepared through the method in Example 1 and 1 g of polyacrylonitrile (PAN with Mw of 150000) were dissolved in 9 mL of DMF. A resulting solution was vigorously stirred at 90°C for 2 h to obtain a NH2-MIL-53(A1 ) / PAN solution. A 10-mL disposable needle tube was filled with the NH2-MIL-53(A1) / PAN solution. The disposable needle tube filled with the NH2-MIL-53(A1) / PAN solution was put into an electrospinning apparatus for spinning. A NH2-MIL-53(A1) nanofiber membrane was prepared through a YFSP-T electrospinning apparatus. The solution was injected into the needle tube at a rate of 0.002 mms'1 through an injection pump, where a high voltage was 30 Kv, and a rotation speed of a receiver was 0.1 r / min. Example 3 The application of NH2-MIL-53(A1) in detecting aflatoxin Bi was as follows. First, 5 mg of NH2-MIL-53(A1) prepared in Example 1 were dispersed in 10 mL of PBS (having a concentration of 0.0IM and a pH of 7.4) at the room temperature. A resulting solution was sonicated for 5 min. A sonicated solution was diluted to prepare a 0.55 pg / mL NH2-MIL-53(A1) dispersion. A sample to be detected was added to the NH2-MIL-53(A1) dispersion, and a mixed solution was incubated at the room temperature for 5 min. A fluorescence intensity of an incubated mixed solution at 430 nm under excitation of 330 nm was recorded. A content of the aflatoxin Bl in the sample to be detected was calculated through comparison with the standard curve between the fluorescence intensity and the AFBi concentration. A method for measuring ultraviolet absorption spectra of NH2-MIL-53(A1) and NH2-MIL-53(A1)+AFBi was as follows: 2 mL of a NH2-MIL-53(A1) solution and 2 mL of a NH2-MIL-53(A1)+AFBi mixed solution were added to the quartz cuvette. The quartz cuvette added with the solutions was put into the ultraviolet spectrophotometer. The ultraviolet absorption spectra within a wavelength range of 200 nm-600 nm were recorded. The results are as shown in Fig. 8: with the addition of AFBi, the absorption peak of NH2-MIL-53(A1) at 330 nm redshifted to 340 nm, which further demonstrated the strong interaction between NH2-MIL-53(A1) and AFBi. A method for acquiring a sensitivity graph and a color change of fluorescence detection of AFBi was specifically as follows: AFBi solutions having different concentrations were added to 0.55 pg / mL NH2-MIL-53(A1) solutions. Resulting solutions were mixed evenly, and mixed solutions were incubated at the room temperature for 5 min. Each solution was added to a 96-well black microplate reader plate, and fluorescence of each solution under excitation of 330 nm was recorded. The results are shown in Fig. 9: it can be seen that with the increase of an AFBi concentration, blue fluorescence of NH2-MIL-53(A1) was excited out; and the blue fluorescence becomes increasingly stronger, i.e., a peak at 430 nm is continuously enhanced. A linear relation of the AFBi concentration is as shown in Fig. 10: the peak at 430 nm without the addition of AFBi was taken as a base, i.e. Fo, and peaks of other concentrations were taken as F. F / F0 was calculated, which was in a linear relation with AFBi. R2=0.99 in the linear relation demonstrated that the linear relation was desirable, and data were meaningful. A linear range was 0 pM-40 pM, and a measurement limit was 3.1 ppb. Example 4 The application of NH2-MIL-53(A1) nanofiber membrane in detecting aflatoxin Bl was as follows. A NH2-MIL-53(A1) nanofiber was cut into disc-shaped nanofibers having a diameter of 1 cm. Then, 15 pL of AFBi solutions having different concentrations were dropwise added independently. After 5 min, fluorescence photos of resulting nanofibers were taken through the smart phone under irradiation with a 365-nm ultraviolet light. G data and B data of these photos were rapidly acquired through the color recognition APP. A value of G / B was calculated and substituted into the linear relation curve (having a linear range of 0 pM-30 pM and a measurement limit of 29.2 ppb, as shown in Fig. 11) between G / B and the AFBi concentration. An AFBi concentration in the substance was calculated. The detection results of AFBi through the NH2-MIL-53(A1) nanofibers are as shown in Fig. 12: the color change was observed under the irradiation with the 365-nm ultraviolet light. It could be clearly observed with eyes that the blue fluorescence became increasingly stronger with the increase of the AFBi concentration. Example 5 The specificity of NH2-MIL-53(A1) is determined as follows. First, 5 mg of NH2-MIL-53(A1) prepared in Example 1 were dispersed in 10 mL of PBS (having a concentration of 0.0IM and a pH of 7.4) at the room temperature. A resulting solution was sonicated for 5 min. A sonicated solution was diluted to prepare a 0.55 pg / mL NH2-MIL-53(A1) dispersion for a fluorescence experiment. Then, 50pL of an AFBi solution having a concentration of 100 pM were added to 900pL of the dispersion, so as to reach a final AFBi concentration of 5 pM. Other interferents such as ochratoxin (OTA), zearalenone (ZEN), Na+, K+, Ca2+, Zn2+, Mg2+, Mn2+, Hg2+, Co2+, Fe3+, Al3+, Ba2+, ascorbic acid (AA), gallic acid (GA), aspartic acid (Asp), tryptophan (Try), L-lysine (Lys), L-cysteine (Cys), L-glutamic acid (Glu), Glucose (GL), sucrose (SR), lactose (LC), fructose (FR), maltose (ML) were added to a solution containing AFBi. A mixed solution was incubated at the room temperature for 5 min. A fluorescence intensity of an incubated mixed solution at an emission peak 430 nm under excitation of 330 nm was recorded. A value of F / FO was calculated to form a graph accordingly. FO indicated a fluorescence intensity at 430 nm without the addition of AFBi. F indicated a fluorescence intensity at 430 nm with the addition of AFBi or other substances. All tests were repeated three times to ensure the statistical accuracy. The results are as shown in Fig. 13: NH2-MIL-53(A1) had a high response to the aflatoxin Bl, ochratoxin (OTA), and zearalenone (ZEN), and had the most sensitive response to AFBi. The immunity of NH2-MIL-53(A1) was determined as follows. First, 5 mg of NH2-MIL-53(A1) prepared in Example 1 were dispersed in 10 mL of PBS (having a concentration of 0.0IM and a pH of 7.4) at the room temperature. A resulting solution was sonicated for 5 min. A sonicated solution was diluted to prepare a 0.55 pg / mL NH2-MIL-53(A1) dispersion for a fluorescence experiment. Then, an AFBi solution having a concentration of 100 pM was added to the dispersion, so as to reach a final AFBi concentration of 5 pM. Other interferents such as ochratoxin (OTA), zearalenone (ZEN), Na+, K+, Ca2+, Zn2+, Mg2+, Mn2+, Hg2+, Co2+, Fe3+, Al3+, Ba2+, ascorbic acid (AA), gallic acid (GA), aspartic acid (Asp), tryptophan (Try), Ldysine (Lys), L-cysteine (Cys), L-glutamic acid (Glu), Glucose (GL), sucrose (SR), lactose (LC), fructose (FR), and maltose (ML) were added to a solution containing AFBi. Therefore, the immunity of NH2-MIL-53(A1) in the copresence of AFBi and the interferents was researched. The AFBi concentration was 5 pM. Concentrations of OTA and ZEN were also 5 pM. Concentrations other interferents were 250 pM. A mixed solution was incubated at the room temperature for 5 min. A fluorescence intensity of an incubated mixed solution at an emission peak 430 nm under excitation of 330 nm was recorded. A value of F / F0 was calculated to form a graph accordingly. F0 indicated a fluorescence intensity at 430 nm without the addition of AFBi. F indicated a fluorescence intensity at 430 nm with the addition of AFBi or other substances. All tests were repeated three times to ensure the statistical accuracy. The results are as shown in Fig. 14: NH2-MIL-53(A1) has desirable immunity in the copresence of AFBi and the interferents. Example 6 The application instance and stability of NH2-MIL-53(A1) in detecting AFBi in a practical sample were as follows. Preprocessing of a sample to be detected: a ground rice sample (200 g) was mixed with 400 mL of acetonitrile for 20 min, then a supernatant was rotatably evaporated to be approximately dry, and a supernatant approximately dry was dispersed in 100 mL of a PBS solution. A mixture was centrifuged (at 10000 rpm for 10 min), and a centrifuged mixture was filtered through a filter membrane of 0.22 pm, so as to obtain a sample solution to be detected. The sample solution to be detected was added to a NH2-MIL-53(A1) dispersion. A mixed solution was incubated at the room temperature for 5 min. A fluorescence intensity of an incubated mixed solution at 430 nm under excitation of 330 nm was recorded. A content of the aflatoxin Bi in the sample to be detected was calculated through comparison with the standard curve between the fluorescence intensity and the AFBi concentration. Alternatively, The sample solution to be detected was dropwise added to disc-shaped nanofibers having a diameter of 1 cm cut from a NH2-MIL-53(A1) nanofiber membrane. Fluorescence photos of nanofibers were taken through the smart phone after 5 min. G data and B data of these photos were rapidly acquired through the color recognition APP. A value of G / B was calculated and substituted into the linear relation curve between G / B and the AFBI concentration. An AFBi concentration in the substance was calculated. The stability of the detection method was as follows. A rice sample was processed through the above method. AFBi was added to all blank rice sample solutions independently, so as to make final concentrations be 0.1 pmolL1, 0.5 pmolL’1, I pmolL’1, 2.5 pmolL'1, and 5 pmolL'1. Resulting solutions were added to NH2-MIL-53(A1) dispersions. Mixed solutions were incubated at the room temperature for 5 min. Fluorescence intensities of incubated mixed solutions at 430 nm under excitation of 330 nm were recorded. Contents of aflatoxin Bl in samples to be detected were calculated through comparison with the standard curve between the fluorescence intensity and the AFBi concentration. Recovery rates of AFBi were calculated, with the results shown in Table 1. Table 1 Stability of detection method Samp Theoretical Actual concentration Recoveiy Deviation (%, le concentration (pmolL') (pmol 1 / ) rate (%) n=3) 0.1 0.10±0.001 98.80 1.81 0.5 0.49±0.01 99.70 0.88 Rice 1 0.99±0.03 99.62 2.93 2.5 2.45±0.07 97.94 3.10 5 4.90±0.14 98.01 2.84 It can be seen from Table 1 that the method of the present disclosure has the desirable stability, and thus can be configured to detecting AFBi in the practical sample. What are described above are merely preferred examples of the present disclosure, and are not intended to limit the present disclosure in other ways. Those skilled in the art may change or modify the examples into equivalent examples having equivalent changes on the basis of the technical contents disclosed above. However, any simple modification, equivalent change, or variation made to the above examples according to the technical essence of the present disclosure without departing from the contents of the technical solutions of the present disclosure still fall within the scope of protection of the technical solutions of the present disclosure.

Claims

25What is claimed is:

1. A method for detecting aflatoxin by using an electrospun nanofiber membrane loaded with NH2-MIL-53(A1), comprising dropwise adding a sample solution to be detected to the electrospun nanofiber membrane loaded with NH2-MIL-53(A1); incubating the electrospun nanofiber membrane added with NH2-MIL-53(A1) at a room temperature; then taking a fluorescence photo of a nanofiber; acquiring G data and B data of the photo through color recognition software; calculating a value of G / B, and substituting the value into a relation curve between G / B and an aflatoxin concentration; and calculating an aflatoxin concentration in the sample solution to be detected;wherein a method for preparing the electrospun nanofiber membrane loaded with NH2-MIL-53(A1) is as follows:dissolving NH2-MIL-53(A1) powder and polyacrylonitrile (PAN) in dimethyl formamide (DMF), and vigorously stirring a resulting solution at 90°C for 2 h to obtain a NH2-MIL-53(A1) / PAN solution; and filling a disposable needle tube with the NH2-MIL-53(A1) / PAN solution, and putting the disposable needle tube filled with the NH2-MIL-53(A1) / PAN solution into an electrospinning apparatus for spinning; andwherein a method for preparing the NH2-MIL-53(Al) powder is as follows:(1) dissolving AlCh 6H2O in ultrapure water, adding NH2-BDC under stirring, and stirring a resulting solution to obtain “solution 1”;(2) dissolving urea in ultrapure water to obtain “solution 2”;(3) gradually adding “solution 2” to “solution 1” under continuous stirring, evenly stirring and mixing a mixed solution, then maintaining a resulting solution at 150°C for 5 h, and naturally cooling an obtained solution to a room temperature, so as to obtain a yellow solid;(4) washing the yellow solid three times with deionized water before centrifugally separating the washed yellow solid from the deionized water, dispersing the said washed yellow solid in DMF to form a suspension, stirring the suspension at the room temperature without light for 24 h,19 03 25and then removing the DMF through centrifugation; and dispersing the solid in methanol, stirring a resulting solution at the room temperature without light for 24 h, and then removing the methanol through centrifugation;(5) vacuum-drying a product washed in step (4) at 50°C for 24 h to obtain the NH2-MIL-53(A1) powder.

2. The method for detecting aflatoxin by using an electrospun nanofiber membrane loaded with NH2-MIL-53(A1) according to claim 1, wherein the sample solution to be detected is prepared through a method as follows: mixing a ground sample with acetonitrile; rotatably evaporating a supernatant to make the supernatant substantially dry; dispersing the substantially dry supernatant in a poly butylene succinate (PBS) solution; and centrifuging a resulting solution, and filtering a centrifuged solution through a filter membrane of 0.22 urn to obtain the sample solution to be detected.

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