Preparation method and application of MXene (at) ZIF-8 (at) AgNPs sensor

Abstract

The invention relates to the technical field of biosensors, in particular to a preparation method and application of an MXene (at) ZIF-8 (at) AgNPs sensor, and the preparation method comprises the step of loading ZIF-8 (at) AgNPs nanoparticles on MXene through electrostatic interaction to form the MXene (at) ZIF-8 (at) AgNPs sensor with excellent detection performance. According to the sensor, the sensitivity of detecting the estrogen drugs is greatly improved through a multiple synergistic enhancement effect brought by plasma enhancement generated by AgNPs and charge transfer of MXene (at) ZIF-8. According to SERS fingerprint characteristics and the Raman activity of target molecules, the estrogen drugs can be directly detected in a label-free manner, and complex and time-consuming pretreatment is avoided. The preparation method disclosed by the invention has the characteristics of simplicity, easiness in operation, rapidness in detection and low cost, and is beneficial to realizing efficient and accurate detection of the estrogen medicines in the complex food matrix.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of biosensors, in particular to a preparation method of an MXene@ZIF-8@AgNPs sensor and application thereof. BACKGROUND

[0002] In recent years, the accumulation of estrogen drugs in the human food chain has attracted increasing attention. As a key hormone that maintains the biological and physiological functions of the human body, estrogen plays an important role in the regulation of the reproductive system, cardiovascular and gastrointestinal function, bone strength, cognitive behavior and pregnancy maintenance. However, excessive exposure to estrogen may induce cardiovascular diseases, cause male reproductive system dysfunction and increase the risk of cancer. Therefore, it is crucial to strictly monitor the level of estrogen drugs in food matrices.

[0003] Currently, the detection of estrogen mainly adopts high-performance liquid chromatography, liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry technologies. Although these methods can achieve the detection of estrogen to a certain extent, they have the disadvantages of complex pretreatment, strong operation professionalism, large consumption of organic solvents, high instrument cost and low sensitivity, which seriously limit their application in actual sample detection. Therefore, it is still necessary to develop an economical and practical, simple, rapid and highly sensitive sensing method for detecting estrogen drugs in complex food matrices.

[0004] In recent years, near-infrared spectroscopy, Raman spectroscopy and laser-induced breakdown spectroscopy have attracted much attention in the field of food safety and quality detection. Among them, surface-enhanced Raman spectroscopy (SERS) has become an important technical means for label-free direct detection of hormone drugs due to its unique fingerprint identification characteristics. This technology not only enables real-time and non-destructive analysis, but also can quickly complete the detection even in a humid environment, and has the outstanding advantage of narrow spectral bandwidth. Through the combination of nanotechnology, SERS can significantly enhance the scattered signal intensity to 10 14 times. The enhancement effect of the substrate material on the SERS signal is crucial, and is the key to high-sensitivity detection of food pollutants. SERS enhancement substrates mainly include two categories: noble metal nanoparticles and semiconductor materials. The latest developed composite nanomaterials combine the physical enhancement of noble metal nanoparticles and the chemical enhancement characteristics of semiconductor materials, and can achieve ultra-high sensitivity detection of trace target small molecules. SUMMARY

[0005] The application aims at the problems of complex and time-consuming pretreatment, expensive instrument equipment and low detection sensitivity of existing analysis methods, and provides a preparation method of MXene@ZIF-8@AgNPs sensor and application thereof. The preparation method is based on MXene, and ZIF-8@AgNPs nanoparticles are loaded on the MXene to form a hybrid MXene@ZIF-8@AgNPs sensor. The plasmonic enhancement effect generated by AgNPs and the multiple synergistic enhancement effect caused by charge transfer of MXene@ZIF-8 provide a strong guarantee for SERS high-sensitivity detection. In addition, the ZIF-8 porous material in the sensor can enrich small molecule estrogens, and combined with its own Raman activity and SERS fingerprint characteristics, in-situ, label-free and high-sensitivity detection of estrogen drugs in food is realized.

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0007] A preparation method of MXene@ZIF-8@AgNPs sensor, the specific steps are as follows:

[0008] S1, synthesis of MXene: 1 g of lithium fluoride is fully dissolved in 10 mL of concentrated hydrochloric acid, and is magnetically stirred for 30 min, then 1 g of aluminum titanium carbide powder is gradually and slowly added to the above solution under stirring. The reactants are stirred at 35 DEG C for 24 h. After the reaction is completed, the obtained powder is washed with deionized water until the pH is about 7, and is centrifugally washed with ethanol three times, and finally the powder is dried in a vacuum oven at 60 DEG C overnight to obtain Ti3C2Tx powder.

[0009] S2, synthesis of ZIF-8: 2-methylimidazole (0.5 g) and zinc nitrate hexahydrate are respectively dispersed in 25 mL of methanol. The two solutions are mixed and stirred for 1 h, and the mixture is aged for 24 h and then centrifuged. Then, the two are washed twice with methanol, and dried at 60 DEG C for 12 h to obtain ZIF-8 powder.

[0010] S3, preparation of MXene@ZIF-8@AgNPs sensor: AgNPs are synthesized by heating reduction method. 100 mL of synthesized AgNPs are concentrated to 20 mL, 50 muL of EDC with a concentration of 2.0 mM and 50 muL of NHS with a concentration of 2.0 mM are added, and the mixture is reacted at room temperature for 4 h to obtain activated AgNPs. ZIF-8 is added to the above activated AgNPs solution, and the mixture is stirred at room temperature for a period of time to obtain ZIF-8@AgNPs. MXene is added to the ZIF-8@AgNPs solution, and the mixture is continuously stirred for a period of time to obtain MXene@ZIF-8@AgNPs sensor.

[0011] Preferably, in step S1, the concentration of the concentrated hydrochloric acid used is 12 mol / L.

[0012] Preferably, in step S2, the concentration of the zinc nitrate hexahydrate used is 0.0015 mol / L.

[0013] Preferably, in step S3, the mass of the ZIF-8 used is 0.2 mg, and the reaction time of the AgNPs with the ZIF-8 is 8 h.

[0014] Preferably, in step S3, the mass of the MXene used is 0.1 mg, and the reaction time of the ZIF-8@AgNPs with the MXene is 10 h.

[0015] The application further provides a use of the MXene@ZIF-8@AgNPs sensor obtained by the preparation method in detection of estrogen drugs.

[0016] Preferably, the specific steps are as follows: 10 muL of different types of estrogen drugs are respectively and in parallel dropped on the prepared MXene@ZIF-8@AgNPs sensor, and SERS detection is performed after reaction at room temperature for 2 h. The excitation wavelength used is 785 nm, the integration time is 15 s, and the integration number is 1.

[0017] By adopting the above technical solution: the ZIF-8@AgNPs nanoparticles are uniformly loaded on the surface of the MXene, and the MXene@ZIF-8@AgNPs sensor with super-high detection sensitivity is obtained. The ZIF-8 porous structure can efficiently enrich the target small molecules, and the simultaneous detection of multiple estrogen drugs can be realized according to the SERS fingerprint spectrum of different types of estrogen drugs.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] 1. The preparation method of the application has the characteristics of simplicity, easy operation, rapid detection, and low cost.

[0020] 2. The MXene@ZIF-8@AgNPs sensor prepared by the application can realize label-free direct detection of estrogen drugs, avoiding complex and time-consuming pretreatment.

[0021] 3. The multiple synergistic enhancement effect of the plasmonic enhancement generated by the AgNPs and the charge transfer of the MXene@ZIF-8 in the sensor greatly improves the sensitivity of the detection of estrogen drugs. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1(a) is a transmission electron microscope image of silver nanoparticles synthesized in the application; (b) is a scanning electron microscope image of synthesized ZIF-8; (c) is a scanning electron microscope image of synthesized MXene; (d) is a scanning electron microscope image of synthesized MXene@ZIF-8@AgNPs;

[0023] Figure 2 (a) is the SERS spectrum of 4-MBA with different concentrations in Example 3 of the application, (b) is the linear relationship diagram of the peak intensity of the probe molecule 4-MBA at 1587 cm -1 ;

[0024] Figure 3 (a) is the SERS spectrum of 4-MPy measured by the MXene@ZIF-8@AgNPs sensor prepared in the application after being placed for different time, (b) is the change diagram of the peak intensity of 4-MPy at 1575 cm -1 ;

[0025] Figure 4 SERS spectrum of DTNB measured by randomly selecting 10 points on the MXene@ZIF-8@AgNPs sensor prepared in the application;

[0026] Figure 5 SERS spectrum of the MXene@ZIF-8@AgNPs sensor for simultaneously detecting four kinds of estrogen drugs in milk. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the application will be described below in conjunction with the drawings, so that those skilled in the art can better understand the advantages and features of the application, and the protection scope of the application can be more clearly defined. The embodiments described in the application are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0028] Example 1: A preparation method of a MXene@ZIF-8@AgNPs sensor, the specific steps are as follows:

[0029] Synthesis of MXene: 1 g of lithium fluoride was dissolved in 10 mL of concentrated hydrochloric acid with a concentration of 12 mol / L, and stirred magnetically for 30 min. Then, 1 g of aluminum titanium carbide powder was gradually and slowly added to the above solution under stirring. The reactants were stirred at 35 °C for 24 h. After the reaction was completed, the obtained powder was washed with deionized water until the pH was about 7, and centrifugally washed with ethanol three times. Finally, the powder was dried in a vacuum oven at 60 °C overnight to obtain Ti3C2Tx powder.

[0030] Synthesis of ZIF-8: 2-methylimidazole (0.5 g) and zinc nitrate hexahydrate (0.0015 mol / L) were dispersed in 25 mL of methanol, respectively. The two solutions were mixed and stirred for 1 h, and the mixture was centrifuged after being aged for 24 h. Then, the ZIF-8 powder was obtained after being washed twice with methanol and dried at 60 °C for 12 h.

[0031] Preparation of MXene@ZIF-8@AgNPs sensor: AgNPs were synthesized by a heating reduction method. 100 mL of the synthesized AgNPs were concentrated to 20 mL, 50 μL of EDC with a concentration of 2.0 mM and 50 μL of NHS with a concentration of 2.0 mM were added, and the reaction was carried out at room temperature for 4 h to obtain activated AgNPs. 0.2 mg of ZIF-8 was added to the above activated AgNPs solution, and the reaction was carried out at room temperature for 8 h to obtain ZIF-8@AgNPs. 0.1 mg of MXene was added to the ZIF-8@AgNPs solution, and the reaction was continued to stir for 10 h to obtain the MXene@ZIF-8@AgNPs sensor.

[0032] Example 2: Characterization of MXene@ZIF-8@AgNPs sensor

[0033] Firstly, the morphology of the prepared AgNPs, ZIF-8 nanoparticles and MXene was characterized. As shown in FIG. 1a, the AgNPs prepared by the heating reduction method were spherical, and the particle size was about 30 nm. The synthesized ZIF-8 nanoparticles were in 12-hedron crystal structure (FIG. 1b), and the MXene showed a sheet structure (FIG. 1c). The morphology of the MXene@ZIF-8@AgNPs synthesized by amide bonding and electrostatic interaction is shown in FIG. 1d. A large number of ZIF-8 nanoparticles in 12-hedron crystal structure were uniformly distributed between the MXene surface and the layered structure, and the spherical AgNPs were loaded on the ZIF-8, which proved the successful preparation of the MXene@ZIF-8@AgNPs sensor. Figure 1 Figure 1 Figure 1 Figure 1

[0034] ​​​​Example 3: Evaluation of the sensitivity of the MXene@ZIF-8@AgNPs sensor

[0035] The detection sensitivity of the MXene@ZIF-8@AgNPs sensor was verified using the SERS probe molecule 4-mercaptobenzoic acid (4-MBA) as the research object. Figure 2 As shown in Figure a, this invention measured different concentrations of 4-MBA on the prepared MXene@ZIF-8@AgNPs sensor. Experimental results show that the SERS signal intensity of 4-MBA gradually increases with increasing concentration. (The last sentence appears to be incomplete and requires further context.) -1 A relationship was established between the SERS peak intensity and the 4-MBA concentration, revealing a good linear relationship between the two. Figure 2 b) The linear regression equation is y = 12404 + 1012x, and the correlation coefficient R0 is... 2 It is 0.971. When the signal-to-noise ratio is 3, the detection limit for 4-MBA using this method is 1.0 × 10⁻⁶. -11 M indicates that the MXene@ZIF-8@AgNPs sensor has high detection sensitivity.

[0036] Example 4: Evaluation of the stability of the MXene@ZIF-8@AgNPs sensor

[0037] In this invention, the SERS probe molecule β-mercaptopyridine (4-MPy) was used as the test object to verify the stability of the MXene@ZIF-8@AgNPs sensor. The prepared MXene@ZIF-8@AgNPs sensor was placed at room temperature for different times (0, 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77 days) to detect a concentration of 1.0 × 10⁻⁶. -8 M's 4-MPy, such as Figure 3 As shown, the 4-MPy SERS signal did not decrease significantly with prolonged placement time, indicating that the MXene@ZIF-8@AgNPs sensor has good stability.

[0038] Example 5: Evaluation of the detection reproducibility of the MXene@ZIF-8@AgNPs sensor

[0039] To demonstrate the detection repeatability of the prepared MXene@ZIF-8@AgNPs sensor, the SERS spectra of DTNB were measured at 10 randomly selected locations on the same sensor. The results are as follows: Figure 4 As shown, the SERS spectra of DTNB at different locations on the sensor show almost no difference. These results demonstrate that the MXene@ZIF-8@AgNPs sensor exhibits excellent detection reproducibility.

[0040] Example 6: SERS simultaneous detection of four kinds of estrogen drugs in milk

[0041] Four portions of skim milk were taken in parallel, and 1.0 x 10 -8 M of estradiol, estrone, diethylstilbestrol and ethinyl estradiol solution were added respectively. After mixing evenly, 10 μL of different types of estrogen drug solution was dropped on the prepared MXene@ZIF-8@AgNPs sensor in parallel, and reacted at room temperature for 2 h, and then SERS detection was carried out. The wavelength of the used laser was 785 nm, the integration time was 15 s, and the integration number was 1. The obtained SERS spectrum is shown in Figure 5 Different types of estrogen drugs have different SERS spectral peaks, which is due to the different molecular structural formula of estrogen drugs. According to the characteristics of SERS fingerprint spectrum combined with the prepared MXene@ZIF-8@AgNPs sensor in the application, four kinds of estrogen drugs existing in milk at the same time can be detected and distinguished.

[0042] In summary, the application is based on MXene, which is loaded with ZIF-8@AgNPs nanoparticles to form a hybrid MXene@ZIF-8@AgNPs sensor. The plasmonic enhancement generated by AgNPs and the multiple synergistic enhancement effect caused by the charge transfer of MXene@ZIF-8 provide a strong guarantee for SERS high-sensitivity detection. In addition, the ZIF-8 porous material in the sensor can enrich small molecule estrogens, combined with its own Raman activity and SERS fingerprint characteristics, to realize in-situ, label-free, high-sensitivity detection of estrogen drugs in food.

[0043] The description and practice disclosed in the application are easy to think and understand for ordinary skilled persons in the technical field, and several improvements and refinements can be made without departing from the principles of the application. Therefore, the modifications made without departing from the spirit of the application should be considered as the protection scope of the application.

Claims

1. A method for fabricating an MXene@ZIF-8@AgNPs sensor, characterized in that, The specific steps are as follows: AgNPs were synthesized using a heating reduction method. 100 mL of the synthesized AgNPs was concentrated to 20 mL, and 50 μL of 2.0 mM EDC and 50 μL of 2.0 mM NHS were added. The mixture was reacted at room temperature for 4 h to obtain activated AgNPs. ZIF-8 was added to the activated AgNPs solution, and the mixture was stirred at room temperature for a period of time to obtain ZIF-8@AgNPs. MXene was added to the ZIF-8@AgNPs solution, and the mixture was stirred for a period of time to obtain the MXene@ZIF-8@AgNPs sensor.

2. The method for fabricating an MXene@ZIF-8@AgNPs sensor according to claim 1, characterized in that, The mass of ZIF-8 used was 0.2 mg, and the reaction time of AgNPs with ZIF-8 was 8 h.

3. The method for fabricating an MXene@ZIF-8@AgNPs sensor according to claim 1, characterized in that, The mass of MXene used was 0.1 mg, and the reaction time between ZIF-8@AgNPs and MXene was 10 h.

4. The application of an MXene@ZIF-8@AgNPs sensor prepared by any one of claims 1-3 in the detection of estrogen drugs.

5. The application according to claim 4, characterized in that, 10 μL of different types of estrogen drugs were dropped in parallel onto the prepared MXene@ZIF-8@AgNPs sensor. After reacting at room temperature for 2 h, SERS detection was performed. The excitation wavelength was 785 nm, the integration time was 15 s, and the number of integrations was 1.

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