Method for colorimetric and photothermal dual-mode detection of aflatoxin b1 in coffee based on mxene@pt nanoszyme

Abstract

The application discloses a method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanozyme, wherein MXene is obtained by etching Ti3AlC2 with LiF and HCl, dopamine carbon dots and sodium borohydride are used as reducing agents, and in-situ reduction technology is adopted to synthesize MXene nanozyme modified with platinum nanoparticles (MXene@Pt). The MXene@Pt shows peroxidase-like activity and photothermal performance enhanced by near-infrared light stimulation, can catalyze the blue deepening of the substrate 3,3',5,5'-tetramethylbenzidine (TMB) and temperature rise, and when aflatoxin B1 exists, the POD-like activity of the MXene@Pt nanozyme is inhibited, and the colorimetric and temperature signals are reduced. The colorimetric and temperature dual-mode sensor detection method for AFB1 is established, and the method has the characteristics of high sensitivity, strong specificity, simple operation, rapidness and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical analysis and detection, and particularly relates to a method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanozyme. BACKGROUND

[0002] Aflatoxin B1 (AFB1) is a toxic metabolite produced by fungi under high temperature and humidity conditions, and pollutes various foods including corn, soybeans, peanuts and rice. AFB1 has also been detected in coffee. Therefore, AFB1 is classified as a class I and 2B strong carcinogen by the International Agency for Research on Cancer (IARC). The acceptable concentration of AFB1 in food and feed raw materials is 0.5-20 μg / kg and 5-50 μg / kg, respectively. Therefore, the analysis and detection of AFB1 in food and agricultural products are crucial for ensuring global food safety and public health safety. Common AFB1 analysis methods include high performance liquid chromatography (HPLC), ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS), thin layer chromatography (TLC), enzyme-linked immunosorbent assay (ELISA), colorimetric method (CL), fluorescence method (FL), electrochemical method (EC), etc. Among these methods, the colorimetric method is of great concern due to its simple operation, rapidness, low cost, and intuitive results. Temperature signal as another simple detection method is mainly generated through the photothermal conversion effect of signal tags. However, how to improve the sensing sensitivity and ensure the high specificity of AFB1 recognition is a key problem, which needs to be solved for the colorimetric and photothermal methods for on-site detection.

[0003] Recently, nano-materials with enzyme-like catalytic activity have been applied to develop sensors for analysis and detection, and nano-materials with peroxidase activity can oxidize TMB to blue oxidized TMB (oxTMB), while oxTMB shows strong NIR laser (808 nm) triggered light conversion efficiency in near infrared (NIR) spectrum, which is used for high-sensitivity quantitative photothermal detection. SUMMARY

[0004] The application discloses a method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanozyme, and the method comprises the following steps: etching Ti3AlC2 by LiF and HCl to obtain MXene, using dopamine carbon dots and sodium borohydride as reducing agents, and synthesizing MXene nanozyme (MXene@Pt) modified with platinum nanoparticles by in-situ reduction technology, wherein the MXene@Pt exhibits near-infrared (NIR) light-stimulated peroxidase-like (POD-like) activity and photothermal performance, and can catalyze the blue deepening of the substrate 3,3',5,5'-tetramethylbenzidine (TMB) and the temperature rise, and the result is attributed to the electron transfer between the platinum nanoparticles and the MXene. When aflatoxin B1 (AFB1) exists, the MXene@Pt surface is exposed to the interaction between AFB1 and the MXene@Pt sites, so that the POD-like activity of the MXene@Pt is inhibited, thereby affecting the generation of oxidized oxTMB and reducing the colorimetric and temperature signals. The colorimetric and temperature dual-mode sensor detection AFB1 method is established, the linear detection range is 0.12-11.67 ng / mL, the colorimetric detection limit is 0.03 ng / mL, and the temperature detection limit is 0.01 ng / mL. The sensor successfully detects AFB1 in a coffee spiked sample, has acceptable accuracy, and the method has the characteristics of high sensitivity, strong specificity, simple operation, rapidness and the like.

[0005] The method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanozyme is as follows:

[0006] (1) 1-2 g of LiF is added into 20-40 mL of 8-10 mol / L HCl solution, and after stirring for 1-1.5 h, 1-2 g of Ti3AlC2 is slowly added, and after mixing, continuous stirring is carried out at 30-40 DEG C for 48 h, and centrifugation is carried out at 3500-4000 rpm for 10-15 min, and the solid is washed with pure water until the pH of the washing liquid is 4-6, and then freeze-drying is carried out to obtain MXene;

[0007] (2) 20-30 mg of tannic acid, 2.0-3.0 g of dopamine and 50-100 muL of ethylenediamine are dissolved in 30-40 mL of deionized water, and after ultrasonic treatment and mixing, the mixture is reacted at a microwave power of 1.0-1.2 kW and 180 DEG C for 100-150 min, and after cooling, centrifugation is carried out at 6000-8000 rpm for 5-10 min, the supernatant is filtered through a 0.22 mm filter membrane, and vacuum drying is carried out to obtain dopamine carbon dots DA-CDs;

[0008] (3) 0.2 mg / mL DA-CDs 50-100 μL, 10 mg / mL chloroplatinic acid solution 200-300 μL, 10 mg / mL sodium citrate solution 200-300 μL were added to 30-40 mL of deionized water, and after ultrasonic treatment, 20 mmol / L sodium borohydride solution 200-300 μL, 4-6 mg MXene were added, stirred for 20-30 min, centrifuged at 6000-8000 rpm for 5-10 min, and the precipitate was obtained, and the precipitate was washed with anhydrous ethanol and deionized water for 3-4 times, centrifuged at 6000-8000 rpm for 5-10 min, and the solid product was dried at 80°C for 12-24 h, to obtain MXene@Pt nanoscale enzyme;

[0009] (4) MXene@Pt nanoscale enzyme solution was added to different concentrations of aflatoxin B1-AFB1 solution, then 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 were added, and the volume was made to 3 mL with pH 4.0 acetate buffer solution, shaken, and left for 5-10 min, and the absorbance was measured at 654 nm wavelength to determine the linear relationship between AFB1 concentration and absorbance value;

[0010] (5) MXene@Pt nanoscale enzyme solution was added to different gradient concentrations of AFB1 solution, then 3,3',5,5'-tetramethylbenzidine and H2O2 were added, and the volume was made to 3 mL with pH 4.0 acetate buffer solution, shaken, and after the reaction solution was irradiated with 808 nm NIR laser for 10-15 min, the temperature was recorded using a portable pen-type digital thermometer and the temperature change value ΔT was calculated, and the linear relationship between AFB1 concentration and temperature change value ΔT was determined, wherein ΔT=T0-T, T0 is the temperature of the reaction system without adding aflatoxin B1, and T is the temperature of the reaction system after adding aflatoxin B1;

[0011] (6) The sample liquid to be measured was operated according to steps (4) and (5), and the absorbance value and the temperature change value ΔT were determined, and the AFB1 content in the sample liquid to be measured was obtained according to the absorbance value and the temperature change value ΔT.

[0012] The concentration of the MXene@Pt solution is 0.6 mg / mL, the addition amount is 50-100 μL, the concentration of 3,3',5,5'-tetramethylbenzidine is 0.15 mmol / L, the addition amount is 50-100 μL, the concentration of H2O2 is 2 mmol / L, and the addition amount is 50-100 μL, and the power of 808 nm NIR is 1.5-2.0 W / cm 2 .

[0013] The advantages of the present application are:

[0014] 1. The platinum nanoparticle modified MXene nanoscale enzyme synthesized in the application has excellent photo-thermal conversion performance, and is based on the electron transfer between the platinum nanoparticles and the MXene, and the platinum nanoparticles reduced by the carbon dots enhance the infrared light absorption, so that the synthesized MXene@Pt nanoscale enzyme exhibits excellent peroxidase-like activity and photo-thermal performance; importantly, AFB1 interacts with the surface sites of the MXene@Pt nanoscale enzyme, so that the POD-like activity of the MXene@Pt nanoscale enzyme is inhibited; when the AFB1 is used to oxidize the substrate TMB into the oxidized form oxTMB, the color of the MXene@Pt nanoscale enzyme becomes lighter and the temperature signal decreases, so that a new method for detecting AFB1 by establishing a colorimetric temperature dual-mode sensor is provided; the linear detection range is 0.12-11.67 ng / mL, the colorimetric detection limit is 0.03 ng / mL, and the temperature detection limit is 0.01 ng / mL, so that a promising alternative method for simple, rapid, specific and sensitive colorimetric photo-thermal detection of AFB1 is provided.

[0015] 2. The detection method established in the application has a standard addition recovery rate of 90.6%-104.5% when used for detecting AFB1 in coffee samples with complex matrix and large interference, and has high system detection accuracy. DETAILED DESCRIPTION

[0016] Figure 1 It is a TEM diagram of the MXene nanoscale enzyme synthesized in Example 1.

[0017] Fig. 2 is a TEM diagram of the MXene@Pt nanoscale enzyme synthesized in Example 1.

[0018] Fig. 3 is an ultraviolet-visible absorption spectrum of MXene@Pt+H2O2+TMB and under 808 nm near-infrared light (NIR) irradiation in Example 1.

[0019] Figure 4 It is the Michaelis equation of the MXene@Pt nanoscale enzyme in Example 1 under the condition of changing the concentration of H2O2 while fixing the concentration of TMB.

[0020] Figure 5 It is the Michaelis equation of the MXene@Pt nanoscale enzyme in Example 1 under the condition of changing the concentration of TMB while fixing the concentration of H2O2.

[0021] Figure 6 It is the Michaelis equation of the MXene@Pt nanoscale enzyme under the condition of changing the concentration of H2O2 while fixing the concentration of TMB under 808 nm near-infrared light irradiation.

[0022] Figure 7 It is the Michaelis equation of the MXene@Pt nanoscale enzyme under the condition of changing the concentration of TMB while fixing the concentration of H2O2 under 808 nm near-infrared light irradiation.

[0023] Figure 8 The result of free radical capture in MXene@Pt catalytic process;

[0024] Figure 9 The UV-vis spectrum of the model electron transfer process of the oxidation of reduced cytochrome c in this Example 1; C

[0025] Figure 10 The temperature-time curve obtained after irradiation at 1.5 W / cm2, 808 nm after adding different concentrations of TMB under the same concentration of MXene@Pt in this Example 1; 2 , 808 nm;

[0026] Figure 11 The photothermal conversion efficiency of MXene@Pt in this Example 1;

[0027] Figure 12 The effect of AFB1 on the POD-like activity of MXene@Pt in this Example 1;

[0028] Figure 13 The colorimetric absorption spectrum (A) and linear fitting curve (B) of AFB1;

[0029] Figure 14 The linear fitting curve of temperature sensing of AFB1;

[0030] Figure 15 The effect of interfering substances on the photothermal and colorimetric detection system of AFB1;

[0031] Figure 16 The effect of coexisting ions on the photothermal detection system of AFB1;

[0032] Figure 17 The effect of coexisting ions on the colorimetric detection system of AFB1. DETAILED DESCRIPTION

[0033] The content of the present application is further illustrated by the following examples, but these examples do not limit the protection scope of the present application, and the methods in the examples are all conventional methods, and the reagents used are all conventional commercially available reagents or reagents prepared according to conventional methods unless otherwise specified;

[0034] Example 1: Determination of AFB1 in coffee samples

[0035] 1. Preparation of MXene

[0036] ​1g LiF and 9 mol / L HCl solution 20 mL were added into a polytetrafluoroethane beaker, 1 g of Ti3AlC2 was slowly added after stirring at 600 rpm for 1 h, and after mixing, it was continuously stirred at a temperature of 35 °C for 48 h, centrifuged at 4000 rpm for 10 min, and the solid was washed with pure water until the pH of the washing liquid was 5, and then freeze-dried to obtain MXene; the MXene was subjected to transmission electron microscopy (TEM) analysis, and the results are shown in Figure 1 Fig. 1, the synthesized MXene has a 2D sheet structure, and the MXene high-resolution TEM (HRTEM) image presents a lattice fringe with a spacing of 0.260 nm, which belongs to the (101) crystal plane of MXene.

[0037] 2. Preparation of DA-CDs

[0038] 25 mg of tannic acid, 2.5 g of dopamine and 70 μL of ethylenediamine were dissolved in 35 mL of deionized water, and after ultrasonic treatment and mixing, the mixture was reacted at a microwave power of 1.0 kW at 180 °C for 120 min, and after cooling, the reaction product was centrifuged at 7000 rpm for 6 min, the supernatant was filtered through a 0.22 mm filter membrane, and vacuum drying was performed to obtain DA-CDs.

[0039] 3. Preparation of MXene@Pt nanoszyme

[0040] 0.2 mg / mL DA-CDs 70 μL, 10 mg / mL chloroplatinic acid solution 250 μL, 10 mg / mL sodium citrate solution 250 μL were added to 35 mL of deionized water, and after ultrasonic treatment and mixing, 20 mmol / L sodium borohydride solution 250 μL and 5 mg Mxene were added, stirred for 20 min, centrifuged at 7000 rpm for 7 min to obtain a precipitate, the precipitate was washed with anhydrous ethanol and deionized water for 3 times, centrifuged at 7000 rpm for 7 min, and the solid product was dried at 80 °C for 15 h to obtain MXene@Pt nanoszyme; the prepared MXene@Pt nanoszyme was subjected to TEM analysis, and the results are shown in Figure 2 Fig. 2, the synthesized MXene@Pt nanoszyme presents a dendritic morphology, and small Pt NPs are uniformly distributed on the surface of MXene, and the clear lattice confirms that the prepared MXene nanosheet and MXene@Pt have high crystallinity, which can be seen from the high-resolution TEM (HRTEM) image, which indicates that after etching and reduction, the crystallinity can be well preserved.

[0041] 4. Evaluation of the peroxidase activity of MXene@Pt nanoszyme

[0042] The concentration of 0.2 mmol / L TMB 100 μL, 2 mmol / L H2O2 100 μL, 1 mg / mL MXene@Pt nanoscale enzyme solution 100 μL, 0.1 mmol / L pH 4.0 acetate buffer solution to 3 mL, shake, stand for 10 min, measure the absorbance at 654 nm wavelength, Figure 3 The results show that MXene@Pt nanoscale enzyme has good mimetic peroxidase activity, under the same conditions, the above reaction system is irradiated by near-infrared light with a power of 1.5 W / cm 2 2 for 10 min, the blue color of the system deepens obviously, proving that near-infrared light has the characteristics of activating MXene@Pt peroxidase-like activity.

[0043] This example also carries out Michaelis-Menten catalytic kinetics parameter determination, the results are shown in Figures 4-7 and Table 1, the Michaelis constant of MXene@Pt nanoscale enzyme for substrates TMB and H2O2 K m are 0.58 mmol / L and 0.49 mmol / L respectively, the reaction rate constant is 0.41×10 -7 mol / L·s and 0.62×10 -7 mol / L·s respectively, after near-infrared light irradiation, the K m of TMB and H2O2 are 0.38 mmol / L and 0.36 mmol / L respectively, the reaction rate constant is 3.34×10 -7 mol / L·s and 3.79×10 -7 mol / L·s respectively, indicating that the addition of near-infrared light irradiation greatly improves the affinity of MXene@Pt nanoscale enzyme with substrates TMB and H2O2, and the reaction speed is increased by 8 times and 6 times;

[0044] Table 1 Michaelis-Menten catalytic kinetics parameters

[0045] ;

[0046] Radical capture: in order to further study the ROS which plays a major role in the catalytic process, isopropyl alcohol (IPA), tryptophan, tempol, sodium oxalate (Na2C2O4) and Cr(Ⅵ) are used to capture ·OH, 1 O2, ·O2 - , h + and e - , the results are shown in Figure 8 After adding IPA, the absorbance of oxTMB decreases obviously. These results show that ·OH is the main active oxygen (ROS) in the catalytic reaction.

[0047] Simultaneously, possible electron transfer mechanisms were explored, and catalytic reactions involving electron transfer were accelerated. To confirm this, reduced cytochrome P450 was used. C Oxidation of (RCC) was used as a sensor reaction, based on RCC as an active intermediate that provides electrons. RCC has two absorption peaks at 520 nm and 550 nm; however, these peaks disappeared after incubation with MXene@Pt nanozymes, while a new peak was observed near 530 nm. Figure 9 The addition of AFB1 reduced the absorbance of the system near 530 nm, indicating an inhibitory effect of AFB1 on the catalytic system. The results show that the oxidation of RCC is achieved through electron transfer to the MXene@Pt nanozyme. Therefore, the catalytic mechanism involves ROS generation and strong electron transfer capabilities.

[0048] 5. Evaluation of the photothermal properties of MXene@Pt nanozymes

[0049] Solutions of 1 mg / mL MXene@Pt nanozymes containing different concentrations of TMB and 2 mmol / L H2O2 were exposed to a power source of 1.5 W / cm². 2 The sample was irradiated with an 808nm laser for 10 minutes, and the temperature change was recorded. A control group without TMB was also included. The results are shown in [Figure number missing]. Figure 10 As shown in the figure, the solution temperature gradually increases with time. The highest temperature reaches 59.8℃ when the TMB concentration is 0.5 mmol / L, while the system temperature is only 32.3℃ without TMB. Simultaneously, the photothermal conversion efficiency (η) of MXene@Pt is calculated to be 62.71% (…). Figure 11 MXene@Pt nanozymes exhibit excellent photothermal conversion capabilities after laser treatment.

[0050] 6. AFB1 Working Curve Creation

[0051] Based on the inhibitory effect of AFB1 on the activity of MXene@Pt nanozymes as peroxidases ( Figure 12), the method establishes a colorimetric and photo-thermal dual-mode detection method for AFB1. In a 5 mL stoppered colorimetric tube, 100 μL of 0.15 mmol / L TMB, 100 μL of 2 mmol / L H2O2, 100 μL of 0.6 mg / mL MXene@Pt nanoscale enzyme, and AFB1 solution were added. The reaction system was adjusted to 3 mL with 0.1 mmol / L pH 4.0 acetate buffer solution, and the concentration of AFB1 in the reaction system was 0.15-12.65 ng / mL. After shaking and standing for 10 min, the absorbance was measured at 654 nm. The standard curve was plotted with AFB1 concentration as the abscissa and absorbance value as the ordinate. The regression equation, correlation coefficient, relative standard deviation, and linear range are shown in Table 2, and the results are shown in Figure 13 ;

[0052] Meanwhile, in a 5 mL stoppered colorimetric tube, 100 μL of 0.15 mmol / L TMB, 100 μL of 2 mmol / L H2O2, 100 μL of 0.6 mg / mL MXene@Pt nanoscale enzyme, and AFB1 solution were added. The reaction system was adjusted to 3 mL with 0.1 mmol / L pH 4.0 acetate buffer solution, and the concentration of AFB1 in the reaction system was 0.030-11.95 ng / mL. After irradiation with an 808 nm NIR laser at a power of 1.5 W / cm 2 for 15 min, the temperature and ΔT were immediately recorded using a portable pen-type digital thermometer. The standard curve was plotted with AFB1 concentration as the abscissa and temperature ΔT as the ordinate. The regression equation, correlation coefficient, relative standard deviation, and linear range are shown in Table 2, and the results are shown in Figure 14 ; where ΔT = T0-T, T0 is the temperature of the reaction system without adding aflatoxin B1, and T is the temperature of the reaction system after adding aflatoxin B1;

[0053] Table 2 Linear equation, correlation coefficient, relative standard deviation, and linear range

[0054] .

[0055] 7. Investigation of method specificity

[0056] AFB1 was replaced by other interfering substances (aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), ochratoxin A (OTA)) and coexisting substances (glufosinate ammonium (GA), chlorogenic acid (CGA), citric acid (CA), tannic acid (TA), coumarin (CMA), glyphosate (Gly), L-aspartic acid (L-Asp), leucine (Leu), lysine (Lys), glucose (Glucose), Ca 2+ , Mg 2+ , K+ and Na + ), the effects of other interfering substances on the MXene@Pt nanoszyme catalytic system in the above colorimetric / photothermal detection system were detected, the final concentration of AFB1 was 5 ng / mL, and the final concentration of the above interfering substances was 50 ng / mL; the results are shown in Figure 15 、 Figure 16 and Figure 17 As can be seen from the figure, only AFB1 has a good inhibitory effect on the MXene@Pt nanoszyme catalytic system, and the results show that the nanoszyme has good selective specificity for AFB1.

[0057] 8. Determination of AFB1 in coffee samples

[0058] (1) Coffee sample treatment

[0059] 5.0 g (accurate to 0.01 g) of coffee powder was mixed with 20.0 mL of distilled water for 5 min, then centrifuged at 8000 rpm for 10 min in a 50 mL centrifuge tube. The sample extract was defatted with 20 mL of n-hexane, and then diluted 50 times with distilled water to reduce the sample matrix effect, and the sample extract was obtained;

[0060] (2) Coffee sample detection

[0061] In a 5 mL stoppered colorimetric tube, 100 μL of 0.15 mmol / L TMB, 100 μL of 2 mmol / L H2O2, and 100 μL of 0.6 mg / mL MXene@Pt nanoszyme were added, 1 mL of sample extract was added, 0.1 mmol / L pH 4.0 acetate buffer solution was added to 3 mL, shaken well, and allowed to stand for 10 min. The absorbance was measured at a wavelength of 654 nm, and the absorbance value was substituted into the regression equation in step 6. The AFB1 content in coffee was not detected;

[0062] Meanwhile, in a 5 mL stoppered colorimetric tube, 100 μL of 0.15 mmol / L TMB, 100 μL of 2 mmol / L H2O2, and 100 μL of 0.6 mg / mL MXene@Pt nanoszyme were added, 1 mL of sample extract was added, 0.1 mmol / L pH 4.0 acetate buffer solution was added to 3 mL, and the reaction system was irradiated with an 808 nm NIR laser with a power of 1.5 W / cm 2 After 15 min of irradiation, the temperature was immediately recorded using a portable pen-type digital thermometer and ΔT was calculated. The ΔT was substituted into the regression equation in step 6, and the AFB1 content in coffee was not detected;

[0063] (3) Recovery and precision experiment: add 3 different concentrations of AFB1 standard solution in coffee sample respectively; each concentration is determined in triplicate, calculate the recovery rate of standard addition, and calculate the relative standard deviation RSD, the results are shown in Table 3, the recovery rate of AFB1 standard addition is 83.0% to 111.0%, and the RSD is 0.90% to 3.21%, wherein the accuracy and precision of the photothermal method are better than those of the colorimetric method, and both methods have acceptable accuracy and precision.

[0064] Table 3 Sample recovery rate and RSD (n=3)

[0065] ;

[0066] The method of example 1 is compared with GB 5009.22-2016 "National food safety standard Determination of aflatoxin B and G in food", and the results are shown in Table 4; it can be seen from the results that the results of the two methods are consistent;

[0067] Table 4 Method comparison results

[0068]

[0069] The determination method of aflatoxin B1 established in the application has the advantages of less processing steps, rapidness, simplicity, no need of large-scale instrument equipment and professional operators of GB 5009.22-2016, short time, low processing cost, simple operation, and strong advantages in actual detection.

Claims

1. A method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanoszyme, characterized in that, The steps are as follows: (1) 1-2 g of LiF is added to 20-40 mL of 8-10 mol / L HCl solution, stirred for 1-1.5 h, then 1-2 g of Ti3AlC2 is slowly added, mixed well, and continuously stirred at 30-40℃ for 48 h, centrifuged, and the solid is washed with pure water until the pH of the washing liquid is 4-6, then freeze-dried to obtain MXene; (2) 20-30 mg of tannic acid, 2.0-3.0 g of dopamine, and 50-100 μL of ethylenediamine are dissolved in deionized water, ultrasonically treated and mixed to dissolve, then the mixture is reacted at 180℃ for 100-150 min under microwave, after cooling, centrifugation, and the supernatant is filtered through a 0.22 mm filter membrane, vacuum dried to obtain dopamine carbon dots DA-CDs; (3) 50-100 μL of 0.2 mg / mL dopamine carbon dots DA-CDs solution, 200-300 μL of 10 mg / mL chloroplatinic acid solution, and 200-300 μL of 10 mg / mL sodium citrate solution are added to deionized water, ultrasonically treated and mixed, then 200-300 μL of 20 mmol / L sodium borohydride solution and 4-6 mg of MXene are added, stirred for 20-30 min, centrifuged to obtain a precipitate, which is washed with anhydrous ethanol and deionized water for 3-4 times, centrifuged, and the solid product is dried to obtain MXene@Pt nanoscale enzyme; (4) MXene@Pt nanoscale enzyme solution is added to different concentrations of aflatoxin B1 solution, then 3,3',5,5'-tetramethylbenzidine and H2O2 are added, and the volume is made to 3 mL with pH 4.0 acetate buffer solution, shaken well, and allowed to stand for 5-10 min, then the absorbance is measured at 654 nm to determine the linear relationship between the concentration of aflatoxin B1 and the absorbance value; (5) MXene@Pt nanoscale enzyme solution is added to different concentrations of aflatoxin B1 solution, then 3,3',5,5'-tetramethylbenzidine and H2O2 are added, and the volume is made to 3 mL with pH 4.0 acetate buffer solution, shaken well, and after the reaction solution is irradiated with 808 nm NIR laser for 10-15 min, the temperature is recorded using a portable pen-type digital thermometer and the temperature change value ΔT is calculated to determine the linear relationship between the concentration of aflatoxin B1 and the temperature change value ΔT, wherein ΔT=T0-T, T0 is the temperature of the reaction system without adding aflatoxin B1, and T is the temperature of the reaction system after adding aflatoxin B1; (6) The sample solution is measured according to steps (4) and (5) to determine the absorbance value and the temperature change value ΔT, and the content of aflatoxin B1 in the sample solution is obtained according to the absorbance value and the temperature change value ΔT.

2. The method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanoszyme according to claim 1, characterized in that: The MXene@Pt nanoszyme solution concentration was 0.6 mg / mL, the added amount was 50-100 μL; the 3,3',5,5'-tetramethylbenzidine concentration was 0.15 mmol / L, the added amount was 50-100 μL; the H2O2 concentration was 2 mmol / L, the added amount was 50-100 μL, and the 808 nm NIR power was 1.5-2.0 W / cm2. 2 .

3. The method for colorimetric and photothermal dual-mode detection of aflatoxin B1 in coffee based on MXene@Pt nanoszyme according to claim 1, characterized in that: The microwave power is 1.0-1.2 kW.

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