Preparation method of MXene-based composite SERS substrate and trace detection application thereof

Abstract

The application discloses a preparation method of a novel composite SERS substrate based on MXene and trace detection application thereof, and particularly relates to the technical field of nanomaterials and spectral detection technology, wherein the substrate takes single-layer MXene nanosheets as a carrier; after synthesis, ZnO crystal seeds are subjected to mediated growth, and the Zeta potential difference between the MXene nanosheets and the ZnO crystal seeds is utilized to make the ZnO crystal seeds loaded on the surface of the MXene nanosheets through electrostatic adsorption to obtain a MXene / ZnO composite material; an Ag@Au core-shell structure is modified on the MXene / ZnO composite material, and finally, a MXene / ZnO@Ag@Au composite material, namely the composite SERS substrate, is obtained.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials technology and spectroscopic detection technology, specifically to a method for preparing a composite SERS substrate based on MXene and its application in trace detection. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) has become an important tool for trace analysis due to its high sensitivity and fingerprint recognition characteristics. However, traditional SERS substrates have many limitations. Pure noble metal substrates (such as Au / Ag NPs) are widely used in the preparation of SERS substrates due to their excellent plasmonic properties, but they are costly, have poor uniformity, and low molecular adsorption selectivity. Bimetallic nanomaterials, composed of two different metals, have advantages over single-metal nanomaterials in SERS applications. While Ag@Au bimetallic structures may not achieve the same enhancement effect as single-metal silver nanostructures of the same size, their signal enhancement capabilities are superior to those of noble metal gold nanostructures. Compared to noble metal nanomaterials, traditional semiconductor substrates have higher flexibility and selective enhancement characteristics, but their enhancement factor (EF) effect is generally lower. Some two-dimensional materials have also been shown to have Raman signal enhancement properties. Studies have shown that MXene materials have good chemoselectivity and certain plasmonic properties in SERS applications. Although they have high conductivity and abundant surface functional groups (-O, -F, etc.), their SERS activity is insufficient when used alone. The synergistic effect of electromagnetic enhancement and chemical enhancement can endow this type of material with excellent enhancement factor.

[0003] Existing MXene composite substrates mostly employ single-metal modification, making it difficult to simultaneously achieve stability and enhancement effects, failing to solve the problem of synergistic enhancement and stability between noble metals and semiconductors. The invention patent with application number CN201910149418.1 uses Ag / MXene-Ti3C2 composites to prepare materials with high SERS activity, but fails to address the issue of Ag's susceptibility to oxidation and instability. Furthermore, the invention patent "Depositing Hydrophilic Ti3C2 on Superhydrophobic ZnO Nanorod Arrays" also addresses this issue. x To improve surface-enhanced Raman scattering properties (DOI: 10.1186 / s12951-022-01756-4), hydrophilic Ti3C2T x A SERS substrate was constructed by depositing superhydrophobic ZnO nanorods. While this substrate achieved high sensitivity through analyte concentration and interfacial charge transfer, its signal intensity was limited by the weak electromagnetic enhancement properties of ZnO, with an enhancement factor only 1 / 100th that of noble metal substrates. This invention addresses the problem of insufficient signal intensity by introducing an Ag@Au core-shell structure, which, while retaining the high adsorption capacity of MXene / ZnO, utilizes the metal LSPR effect to enhance the enhancement factor. Summary of the Invention

[0004] Therefore, this invention provides a method for preparing an MXene-based composite SERS substrate and its application in trace detection. By designing an MXene / ZnO@Ag@Au system, the sensitivity and stability of the substrate are significantly improved by utilizing the charge transfer capability of MXene, the exciton resonance effect of ZnO, and the bimetallic synergistic effect of Ag@Au, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing an MXene-based composite SERS substrate, wherein the substrate uses a single-layer MXene nanosheet as a carrier; mediated growth of synthesized ZnO seeds is performed, and the ZnO seeds are loaded onto the surface of the MXene nanosheets by electrostatic adsorption using the zeta potential difference between the MXene nanosheets and the ZnO seeds to obtain an MXene / ZnO composite material; an Ag@Au core-shell structure is modified on the MXene / ZnO composite material to finally obtain an MXene / ZnO@Ag@Au composite material, i.e., a composite SERS substrate.

[0006] Preferably, the monolayer MXene nanosheets are Ti3C2T. X T X This indicates a surface functional group, which is at least one of a hydroxyl group (-OH), an oxygen anion (-O), or a fluorine atom (-F).

[0007] Preferably, the Ag@Au bimetallic core-shell nanoparticles have a particle size of 50 nm and an Au shell thickness of 5 nm.

[0008] Preferably, the preparation steps of monolayer MXene nanosheets include:

[0009] In-situ HF etching of Ti3AlC2 MAX phase was performed using HCl / LiF. 2.4 g of LiF was added to a PTFE beaker and dissolved in 40 mL of 9 M hydrochloric acid solution. The mixture was magnetically stirred at room temperature for 20 minutes to prepare the HCl / LiF mixed etching solution. Then, 2 g of Ti3AlC2 MAX phase material was added to 40 mL of the etching solution, and etching was performed at 40 °C for 48 h. Monolayer MXene was obtained by ultrasonic exfoliation in an ice bath for 1 h under nitrogen protection. The supernatant was repeatedly washed with 2 M HCl solution and deionized water until the pH of the supernatant was above 6. The supernatant was centrifuged at 3500 rpm for 30 minutes, and the upper liquid was collected to obtain dark green monolayer MXene nanosheets. The method tended to retain large-sized monolayer or few-layer MXene (with larger lateral dimensions), while allowing some incompletely exfoliated multilayer structures to precipitate.

[0010] Preferably, the preparation steps of the MXene / ZnO composite material include:

[0011] ZnO nanoparticles were prepared by a seed growth method. Zinc acetate dihydrate (CH3COO)2Zn·2H2O was added to diethylene glycol DEG and heated to 160℃ in an oil bath under N2 protection. The resulting emulsion colloidal suspension was centrifuged at 8000 rpm, and the supernatant was used as ZnO seed crystals for subsequent reactions. (CH3COO)2Zn·2H2O was dissolved in diethylene glycol DEG and heated to 140℃ in an oil bath from room temperature. The obtained supernatant ZnO seed crystals were slowly added dropwise at a rate of 1 drop / min through a separatory funnel, and the temperature was gradually increased to 160℃. The mixture was stirred at this temperature for 1 h. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed with ethanol to obtain monodisperse ZnO nanoparticles. MXene / ZnO composite materials were formed by electrostatic adsorption self-assembly between MXene and ZnO.

[0012] Preferably, the zeta potential difference between MXene nanosheets and ZnO seeds is greater than 50 mV. Surface end-group modification: By controlling the reaction conditions during HF / HCl etching of the MAX phase, the MXene surface is enriched with -O / -F end groups, resulting in a zeta potential of approximately -30 mV. Synthesis process optimization: ZnO seeds are prepared using the sol-gel method. By adjusting the ratio of zinc acetate to the complexing agent, the ZnO surface is made positively charged, resulting in a zeta potential of approximately +30 mV.

[0013] Preferably, Ag nanoparticles are deposited on the oxygen vacancies of the MXene / ZnO composite material by reacting NaBH4 with AgNO3 at 70°C for 1 h, followed by deposition using 6.25 × 10⁻⁶ nanoparticles. -3 M NH2OH·HCl and 4.65×10 -4 The Au shell is formed by replacing the Ag seed crystal with M HAuCl4·4H2O for 45 min, thus achieving the coating of Au on the Ag seed crystal and finally forming the Au@Ag core-shell structure.

[0014] This invention also discloses an application whereby the composite SERS substrate prepared using the above method can synergistically enhance the Raman signal by combining the electromagnetic field enhancement of noble metals with the chemical enhancement of MXene charge transfer and semiconductor exciton resonance, exhibiting excellent enhancement effects and a detection limit of 6.53 × 10⁻⁶ for 4-NTPs. -13 M, RSD=1.95%.

[0015] Preferably, the prepared composite SERS substrate is used for the rapid detection of trace substances, including active ingredients in traditional Chinese medicine, fungal toxins, and pesticide residues.

[0016] The present invention has the following advantages:

[0017] This invention utilizes monolayer MXene nanosheets as a carrier; it mediates the growth of synthesized ZnO seeds; and leverages the Zeta potential difference between the MXene nanosheets and the ZnO seeds to electrostatically adsorb the ZnO seeds onto the surface of the MXene nanosheets, thus obtaining an MXene / ZnO composite material. An Ag@Au core-shell structure is then modified onto the MXene / ZnO composite material to finally obtain an MXene / ZnO@Ag@Au composite material, i.e., a composite SERS substrate. Compared with existing technologies, the preparation method of this invention is simple to operate, cost-controllable, and can be mass-produced. The prepared MXene / ZnO@Ag@Au composite material can serve as a substrate to enhance the signal of probe molecules, exhibiting excellent enhancement effects. Attached Figure Description

[0018] Figure 1 Zeta potential diagrams of MXene, ZnO, MXene / ZnO and MXene / ZnO@Ag@Au provided for this invention;

[0019] Figure 2 SEM characterization images of MXene, ZnO, MXene / ZnO and MXene / ZnO@Ag@Au provided for this invention;

[0020] Figure 3 UV maps of different MXene / ZnO ratios provided for this invention;

[0021] Figure 4 UV images of MXene, ZnO, MXene / ZnO, and MXene / ZnO@Ag@Au provided by this invention;

[0022] Figure 5 SERS diagrams of different ratios of MXene / ZnO detection probe molecules provided for this invention;

[0023] Figure 6 Comparison of SERS enhancement effects of MXene, ZnO, MXene / ZnO, Ag, Ag@Au and MXene / ZnO@Ag@Au for each material provided by this invention at the same concentration of 4-NTP;

[0024] Figure 7 Comparison of SERS enhancement effects of each material (MXene, ZnO, MXene / ZnO, Ag, Ag@Au, and MXene / ZnO@Ag@Au) at the 4-NTP characteristic peak provided by this invention;

[0025] Figure 8 The detection stability diagram of 4-NTPs on SERS substrates of different batches of MXene / ZnO@Ag@Au provided by this invention;

[0026] Figure 9 The repeatability test diagrams of SERS substrates for 4-NTPs from different batches of MXene / ZnO@Ag@Au provided by this invention are shown. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Figure 1 This is a zeta potential plot for MXene, ZnO, MXene / ZnO, and MXene / ZnO@Ag@Au. The horizontal axis represents the sample type (MXene, ZnO, MXene / ZnO, MXene / ZnO@Ag@Au), and the vertical axis represents the zeta potential (mV), indicating the charge properties of the material surface. Blue represents the zeta potential of MXene nanosheets, green represents the zeta potential of ZnO nanoparticles, orange represents the zeta potential of MXene / ZnO composites, and red represents the zeta potential of MXene / ZnO@Ag@Au. The zeta potentials of MXene and ZnO have opposite signs (MXene is negative, ZnO is positive), and the potential difference is greater than 50 mV. The MXene / ZnO potential falls between these two, indicating successful electrostatic adsorption and laying the foundation for subsequent composite substrate preparation. Ag@Au is a noble metal with an inherently negative potential; the negative potential of the MXene / ZnO@Ag@Au composite grown on MXene / ZnO increases.

[0029] Figure 2 SEM images of MXene, ZnO, MXene / ZnO, and MXene / ZnO@Ag@Au are shown. The MXene monolayer nanosheets exhibit a transparent, wrinkled, sheet-like structure. The ZnO nanoparticles are uniformly dispersed spherical particles. In the MXene / ZnO composite, ZnO particles are anchored to the surface of the MXene sheets, forming a dense load through electrostatic adsorption, providing a basis for subsequent charge transfer (CM). In the MXene / ZnO@Ag@Au composite, Ag@Au core-shell particles are uniformly distributed at the MXene / ZnO interface. This structure enhances SERS performance through a synergistic mechanism of Ag@Au's LSPR effect (electromagnetic enhancement) and MXene / ZnO interface charge transfer (chemical enhancement).

[0030] Figure 3UV spectra of probe molecules and different materials with different MXene / ZnO ratios are shown. The horizontal axis represents wavelength (nm), and the vertical axis represents absorbance OD (au). Multiple curves correspond to different MXene:ZnO mass ratios (80:20, 50:50, 20:80, 10:90) and the UV-Vis spectra of MXene, MXene / ZnO, MXene / ZnO@Ag, and MXene / ZnO@Ag@Au. The optimal MXene:ZnO ratio is 80:20. Absorbance decreases with increasing ZnO ratio, as excess ZnO may shield the active sites of MXene. 420 nm is the surface plasmon resonance (SPR) absorption peak of Ag nanoparticles, and the redshift of the absorption peak confirms the core-shell structure of Ag@Au.

[0031] Figure 4 These are UV maps of different materials measured when the optimal ratio of MXene to ZnO is 80:20.

[0032] Figure 5 SERS plots of probe molecules for different MXene / ZnO ratios. The horizontal axis represents the Raman shift (cm). -1 The vertical axis represents the Raman intensity (au). Multiple curves correspond to the SERS plots for different MXene:ZnO mass ratios (80:20, 50:50, 20:80, 10:90).

[0033] Figure 6 Comparison of SERS enhancement effects of the same concentration of 4-NTP for each material. The horizontal axis represents Raman displacement (cm). -1 The vertical axis represents Raman intensity (au). Pure MXene represents the baseline signal, ZnO exhibits a weak CM effect, MXene / ZnO is dominated by CM, and the MXene / ZnO@Ag@Au composite material shows a synergistic effect of EM and CM. The characteristic peak of 4-NTP is at 1340 cm⁻¹. -1 (NO2 symmetric stretching). MXene / ZnO@Ag@Au at 1340cm -1 The strength is 10. 5 Ag@Au, with an improvement of 100 times compared to MXene / ZnO. After the introduction of Ag@Au, the electromagnetic enhancement (EM) combined with the chemical enhancement (CM) of MXene / ZnO achieves an EF of 10. 8 ( Figure 7 verify).

[0034] Figure 7This is a comparison of SERS enhancement effects at the characteristic peaks of 4-NTP. The horizontal axis represents material type (MXene, ZnO, MXene / ZnO, MXene / ZnO@Ag@Au). The vertical axis represents Raman intensity (au). The histogram for 4-NTP detection by MXene / ZnO@Ag@Au is significantly higher than that of other materials. The stability reaches RSD=1.95%. Figure 8 and Figure 9 (), which is far lower than that of traditional precious metal substrates.

[0035] Comparative Group 1: Patent application CN201910149418.1 proposes an Ag / MXene-Ti3C2 composite material. This patent uses Ag nanoparticles to modify MXene to prepare a SERS substrate, utilizing the localized surface plasmon resonance (LSPR) effect of Ag to enhance the Raman signal. The specific method includes: loading Ag NPs onto the MXene surface via chemical reduction to form the Ag / MXene composite material. Tests show that the detection limit of this substrate for probe molecules (4-NTPs) can reach 10. -12 M, the enhancement factor (EF) is superior to pure MXene. However, it has certain limitations. For example, Ag NPs are easily oxidized to Ag₂O in air, leading to SERS signal attenuation and poor stability (signal intensity decreases by about 40% after 30 days). Relying solely on the electromagnetic enhancement of Ag, without combining it with the chemical enhancement of semiconductor materials, limits further improvement in sensitivity. This invention solves the Ag oxidation problem by introducing ZnO and Au shells, and simultaneously utilizes the exciton resonance of ZnO and the charge transfer of MXene to achieve multiple enhancements, reducing the detection limit (10). -14 M) is significantly superior to this patent.

[0036] Comparison Group 2: Journal of Nanobiotechnology, "Deposition of Hydrophilic Ti3C2T on Superhydrophobic Zn0 Nanorod Arrays" x A method for improving surface-enhanced Raman scattering performance using ZnO / Ti3C2T was proposed. x Composite material, hydrophilic Ti3C2T deposited on superhydrophobic ZnO nanorod array via hydrothermal method. x Nanosheets to construct ZnO / Ti3C2T x Composite SERS substrate. Its core innovations include: research shows that ZnO and Ti3C2T... x The interfacial charge transfer enhanced the chemical enhancement effect (CM), and the detection limit for R6G was 10. -11M. This substrate exhibits high molecular adsorption selectivity and uniformity, but its signal intensity is weak, far lower than that of noble metal substrates. The lack of electromagnetic enhancement (EM) in pure semiconductor systems leads to insufficient SERS signal intensity. This non-patent document does not introduce Ag / Au NPs, thus failing to utilize the LSPR effect. This invention introduces an Ag@Au core-shell structure based on ZnO / MXene, combining electromagnetic enhancement (Ag@Au) and chemical enhancement (ZnO / MXene), thereby increasing the enhancement factor and reducing the detection limit by two orders of magnitude (10). -14 M).

[0037] Example 1: Different masses of ZnO NPs were added to 2 mg / mL Ti3C2T X In MXene colloidal solution.

[0038] Ultrasonic mixing for 60 minutes yielded mixed suspensions with different ZnO NPs contents, including Ti3C2T. X The mass ratios of MXene to ZnONPs were 80:20, 50:50, 20:80, and 10:90, respectively.

[0039] Take pure Ti3C2T X The MXene solution was sonicated for 60 minutes to mix thoroughly and then dried at 60°C for 12 hours as a control sample.

[0040] 10 μL of 4-NTP solution was added to each MXene / ZnO composite material.

[0041] Adsorption was performed in the dark for 12 hours to ensure full loading of 4-NTPs.

[0042] Performance: Quality compared to Ti3C2T X The optimal ratio for MXene:ZnO is 80:20 for detecting 4-NTPs. Figure 5 The horizontal axis represents the charge Raman shift, and the vertical axis represents the Raman signal intensity, reflecting the SERS enhancement effect. Different curves correspond to the SERS spectra of different MXene:ZnO mass ratios (pure MXene, 80:20, 50:50, 20:80, 10:90), used to optimize the composite material ratio. MXene's high conductivity and abundant functional groups (-O / -F) promote charge transfer, while ZnO enhances molecular adsorption. Excessive ZnO will mask the active sites of MXene, weakening the CM effect. 80:20 is the optimal ratio, balancing the charge transfer of MXene and the exciton enhancement of ZnO (Example 1). The problem of Ag's easy oxidation and instability is solved. Ag is easily oxidized, leading to SERS signal attenuation. This invention forms an Au shell through a substitution reaction to prevent the oxidation of the Ag core. Under the same conditions, the RSD of MXene / ZnO@Ag@Au is 1.95% (… Figure 8and Figure 9 The Ag / MXene substrate has an RSD > 10%. This also solves the problem of insufficient substrate signal strength in the aforementioned ZnO / Ti3C2T substrate. x The substrate (DOI:10.1186 / s12951-022-01756-4) depends only on CM, EF=1.49×10 7 This invention introduces the LSPR effect (EM) through the growth of Ag@Au, resulting in increased peak intensity. The EF of MXene / ZnO@Ag@Au is 10. 8 Far exceeding MXene / ZnO and pure Ag@Au (10 6 The arithmetic sum of has a synergistic effect.

[0043] Example 2: MXene and ZnO were mixed at a mass ratio of 80:20, and then 1% AgNO3 and 0.1% NaBH4 were added to react and Ag NPs modified MXene / ZnO composite material was obtained.

[0044] Add 6.25×10 -3 M NH2OH·HCl and 4.65×10⁻ 4 Add M HAuCl4·4H2O (approximately 2 mL / min), stir for 45 min in the dark, centrifuge, and wash with deionized water.

[0045] Add 10 μL of 4-NTP solution to the MXene / ZnO@Ag@Au composite material.

[0046] Adsorption was performed in the dark for 12 hours to ensure full loading of 4-NTPs.

[0047] Results: The SERS signal of 4-NTP was significantly enhanced under 785nm laser light, with RSD=1.95%. (Figure) Figure 8 and Figure 9 ); Figure 8 and Figure 9 The stability and repeatability of MXene / ZnO@Ag@Au as the SERS substrate for 4-NTP detection were tested. The horizontal axis represents the test batch, and the vertical axis represents the Raman signal intensity. The results show that the signal intensity fluctuation is extremely small, with differences between batches <5% (RSD=1.95%). The horizontal axis represents the Raman displacement (cm). -1 The vertical axis represents the Raman intensity (au). Even after long-term storage, the signal showed no significant attenuation trend, proving that the Au shell effectively prevents Ag oxidation.

[0048] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a MXene-based composite SERS substrate, characterized by: The substrate takes monolayer MXene nanosheets as a carrier; mediated growth is carried out on the synthesized ZnO crystal seeds; the Zeta potential difference between the MXene nanosheets and the ZnO crystal seeds is utilized to make the ZnO crystal seeds loaded on the surface of the MXene nanosheets through electrostatic adsorption to obtain a MXene / ZnO composite material; an Ag@Au core-shell structure is modified on the MXene / ZnO composite material, and finally a MXene / ZnO@Ag@Au composite material, that is, a composite SERS substrate, is obtained. The single-layer MXene nanosheet is Ti3C2T X wherein T X represents a surface functional group, which is at least one of a hydroxyl group -OH, an oxygen negative ion -O, or a fluorine atom -F. Wherein, Ag@Au core-shell structure is modified on MXene / ZnO composite material, specifically: Ag nanoparticles are deposited on oxygen vacancies of MXene / ZnO composite material by reaction of NaBH4 and AgNO3 at 70°C for 1 h, then 6.25x10 -3 M NH2OH·HCl and 4.65x10 -4 M HAuCl4·4H2O are used to replace for 45 min to form Au shell, realize coating of Au on Ag seed, and finally form Au@Ag core-shell structure.

2. The method for preparing a composite SERS substrate based on MXene according to claim 1, characterized in that: The particle size of the MXene / ZnO@Ag@Au is 150 nm.

3. The method of claim 1, wherein: The monolayer MXene nanosheet preparation step includes: HCl / LiF in-situ generated HF etching Ti3AlC2 MAX phase, 2.4 g LiF was added in a polytetrafluoroethylene beaker, dissolved in 40 mL 9 M hydrochloric acid solution, magnetic stirring at room temperature for 20 minutes, preparation of HCl / LiF mixed etching solution, then 2 g Ti3AlC2 MAX phase material was added into 40 mL of the above etching solution, etching at 40 DEG C for 48 h, under the protection of nitrogen, ice bath ultrasonic stripping for 1 h, then the supernatant was collected to obtain dark green monolayer MXene nanosheets.

4. The method of claim 1, wherein: The MXene / ZnO composite material preparation step includes: ZnO nanoparticles were prepared by seed growth method, zinc acetate dihydrate (CH3COO)2Zn·2H2O was added into diethylene glycol (DEG), and the mixture was heated to 160 DEG C in an oil bath under N2 protection; the obtained milky colloidal suspension was centrifuged at 8000 rpm, and the supernatant was used as ZnO crystal seeds for subsequent reaction; (CH3COO)2Zn·2H2O was dissolved in diethylene glycol (DEG), and the mixture was heated from room temperature to 140 DEG C in an oil bath, the obtained supernatant ZnO crystal seeds were slowly added into the mixture through a separatory funnel at a rate of 1 drop / min, and the temperature was gradually increased to 160 DEG C, and the mixture was stirred for 1 h after reaction, then cooled to room temperature, and the product was washed with ethanol to obtain monodispersed ZnO nanoparticles; MXene / ZnO composite material was formed by electrostatic adsorption self-assembly between MXene and ZnO.

5. The method of claim 4, wherein the MXene-based composite SERS substrate is prepared by the following steps: (1) preparing a MXene solution; (2) mixing the MXene solution with a SERS substrate to form a mixture; (3) drying the mixture to obtain a MXene-based composite SERS substrate. The Zeta potential difference between the MXene nanosheets and the ZnO crystal seeds is greater than 50 mV.

6. Use of a composite SERS substrate prepared using the method according to any one of claims 1 to 5, characterized in that: The prepared composite SERS substrate is applied to rapid detection of trace substances, including traditional Chinese medicine efficacy substances, mycotoxins and pesticide residues, and the composite SERS substrate can synergize electromagnetic field enhancement of noble metals with chemical enhancement of MXene charge transfer and semiconductor exciton resonance, so as to enhance the Raman signal, and the detection limit of 4-NTP reaches 6.53x10 -13 M, RSD = 1.95%.

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