SPR sensor chip based on two-dimensional material as well as preparation method and application of SPR sensor chip

Abstract

The invention relates to the technical field of biosensors, and discloses a two-dimensional material-based SPR sensor chip and a preparation method and application thereof, the two-dimensional material-based SPR sensor chip comprises a prism, the prism is sequentially covered with a metal layer, an indium tin oxide layer and a two-dimensional material layer, and the two-dimensional material is an MXene two-dimensional material or a perovskite two-dimensional material. The invention has the following beneficial effects: by integrating the advantages of Ag, ITO, MXene or perovskite materials, multi-layer function enhancement is realized: the Ag layer provides a basis for SPR effect, ITO is a transparent conductive oxide, and in an SPR sensor, ITO is used as a substrate material, provides excellent optical transmission and conductivity, and is helpful for optimizing optical signal acquisition and enhancement effect of the sensor; the MXene layer or the perovskite layer has good adsorbability to various heavy metal ions, the MXene layer enhances charge transfer efficiency and chemical stability, and the perovskite layer optimizes optical signals and sensitivity. Due to the characteristics, the sensor has relatively high sensitivity in the aspect of plant heavy metal detection.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensors, and in particular to an SPR sensor chip based on two-dimensional materials, and a preparation method and application thereof. Background Art

[0002] Problems with the existing technology for detecting heavy metal ions in plant leaves: In the detection of heavy metal ions in plant leaves, traditional methods such as ion selective electrode measurement may have the following problems: (1) Complicated sample pretreatment: Traditional ion selective electrode measurement usually requires complex pretreatment processes such as sample preparation and ion extraction for plant leaf samples. The operation is complicated and prone to operational errors and sample contamination. (2) Low detection sensitivity: The detection sensitivity of traditional methods is limited and cannot meet the requirements for rapid and accurate detection of trace heavy metal ions. (3) Difficulty in real-time monitoring: Traditional ion selective electrode measurement methods usually require the destruction of sample structure and cannot perform real-time monitoring, making it difficult to understand the dynamic changes of heavy metal ions.

[0003] Surface plasmon resonance (SPR) refers to the phenomenon that the conduction band electrons of metal resonate on the metal surface under the stimulation of external electromagnetic field. The typical model of prism-type SPR is a total reflection prism, with one or more layers of metal film coated on the total reflection surface. When the incident angle of the light signal on the total reflection surface is greater than the critical angle, the light signal is totally reflected. Under this condition, the p-polarized light of the light signal transmits the light signal to the metal film medium at the interface between the total reflection surface of the prism and the metal film. The light signal is the evanescent wave, and its amplitude decays exponentially, causing the free electrons in the metal medium to form a surface plasmon wave. If the incident angle or wavelength of the light signal is adjusted to a certain value, the frequency of the surface plasmon wave is equal to the wave number of the evanescent wave, and they will be energy coupled and resonate. Then the energy of the incident light signal is absorbed, and the emission light intensity is reduced accordingly. When the reflected light energy decreases sharply within a certain angle, a resonance peak appears in the reflection spectrum. The corresponding incident angle that induces the complete disappearance of the reflected light is called the resonance angle.

[0004] Traditional SPR sensor chips are mainly based on metal film structures, with poor sensitivity, accuracy and FOM. There are several ways to improve the performance of SPR sensor chips, such as adding sensor materials, changing the geometry or increasing the number of channels. Among them, adding sensor materials is the most effective. However, existing research has found that adding ordinary bulk materials (MgF2, Si3N4, etc.) has little effect on performance improvement, especially on sensitivity and accuracy, which limits the development of SPR sensors. Summary of the invention

[0005] The purpose of the present invention is to improve the sensitivity and accuracy of SPR sensors in detecting heavy metal ions in plant leaves. In view of the above-mentioned shortcomings of the prior art, an SPR sensor chip based on two-dimensional materials and a preparation method and use thereof are proposed.

[0006] The SPR sensor based on two-dimensional materials comprises a prism, wherein the prism is sequentially covered with a metal layer, an indium tin oxide layer and a two-dimensional material layer, wherein the two-dimensional material is a MXene two-dimensional material or a perovskite two-dimensional material.

[0007] The preparation method of the perovskite two-dimensional material comprises the following steps: S1, modifying the perovskite nanomaterial with nanosilver and polyvinyl alcohol to obtain a modified perovskite nanomaterial; S2, solvent treatment and stripping: dispersing the modified perovskite nanomaterial in a stripping solution, promoting the stripping and dispersion of the modified perovskite nanomaterial under the action of ultrasound, and obtaining a dispersed solution of a single-layer modified perovskite two-dimensional material; S3, coating: coating the modified perovskite nanomaterial dispersion onto the surface of the indium tin oxide layer to form a uniform perovskite two-dimensional film or sheet structure on the substrate; S4. Heat treatment and crystallization: Heat treatment forms perovskite two-dimensional materials.

[0008] The above technical solution is further configured as follows: the thickness of the indium tin oxide layer is 1-5 nm.

[0009] The above technical solution is further configured as follows: the MXene two-dimensional material is provided with 1 to 2 layers, and the thickness of a single layer of the MXene two-dimensional material is 0.993 nm.

[0010] The above technical solution is further configured as follows: the perovskite two-dimensional material is provided with 1 to 8 layers, and the thickness of a single layer of the perovskite two-dimensional material is 1 nm.

[0011] The above technical solution is further configured as follows: the metal layer is an Ag film, and the thickness of the Ag film is 10-50 nm.

[0012] The above technical solution is further configured as follows: the prism is made of BK7 glass with a refractive index of 1.5151 and a thickness of 200 nm.

[0013] A method for preparing an SPR sensor chip based on two-dimensional materials, characterized in that it comprises the following steps: S1, selecting glass as the substrate material and depositing an Ag film on the surface of the substrate material; S2, depositing an ITO thin film on the Ag film; S3. Depositing MXene two-dimensional material or perovskite two-dimensional material on the ITO film to obtain an SPR sensor chip.

[0014] A two-dimensional material-based SPR sensor comprises a He-Ne laser, a polarizer, an SPR sensor chip, a rotating stage, a photodetector, a lens, a complementary metal oxide semiconductor device camera, a main control unit, and a display; the He-Ne laser is used to generate incident light, the incident light is incident into the SPR sensor chip through the polarizer, the SPR sensor chip is mounted on the rotating stage, the reflected light is captured by the complementary metal oxide semiconductor device camera through the photodetector and the lens, and then transmitted to the main control unit.

[0015] The method for detecting heavy metal ions in plant leaves by an SPR sensor device comprises the following steps: S1. Plants are cultivated in a greenhouse, and heavy metal reagents are regularly irrigated using an orthogonal experimental method to obtain plant leaves containing heavy metal ions at different concentrations; S2. Dissolve plant leaves containing heavy metal ions of different concentrations into standard liquid samples using plant-based solvents, and use SPR sensors to collect SPR spectral imaging data of the standard liquid samples at 632.8 nm in accordance with the concentration gradient of heavy metal ions in the standard liquid samples to prepare a standard curve; S3. After the plant leaves containing heavy metal ions to be tested are dissolved into a liquid sample to be tested using a plant-type solvent, an SPR sensor is used to collect SPR spectral imaging data of the liquid sample to be tested at 632.8 nm, and the heavy metal ion content in the plant leaves containing heavy metal ions is obtained according to the standard curve in step S2.

[0016] The above technical solution is further configured as follows: the heavy metal ions include Hg 2+ 、Cd 2+ , Pb 2+ Cr 2+ Cr 3+ Cr 6+ 、Zn 2+ , Cu 2+ One of them.

[0017] The beneficial effects of the present invention are: 1. The SPR sensor chip of the present invention realizes multi-level functional enhancement of the SPR sensor chip by integrating the advantages of Ag, ITO, MXene or perovskite materials: Ag film provides the basis of SPR effect; ITO is a transparent conductive oxide. In the SPR sensor chip, ITO is used as a substrate material to provide excellent optical transmittance and conductivity, which helps to optimize the optical signal acquisition and enhancement effect of the sensor; MXene two-dimensional material layer or perovskite two-dimensional material layer has good adsorption for heavy metal ions, which is conducive to the specific detection of heavy metal ions; MXene, as a two-dimensional material with excellent conductivity and chemical stability, is modified on the substrate surface of the SPR sensor chip, which can enhance the charge transfer efficiency of the SPR sensor chip, thereby improving the sensitivity of the sensor and enhancing the chemical stability of the SPR sensor chip; the perovskite two-dimensional material layer can optimize the optical signal and sensitivity. These characteristics make the SPR sensor have high sensitivity in plant heavy metal detection.

[0018] 2. Perovskite has high electron concentration, high mobility, optical and electronic properties, which help SPR sensors improve performance. Perovskite can form a local enhanced electromagnetic field effect (LSPR) on the surface of the SPR sensor chip, which can enhance the optical signal on the surface of the SPR sensor chip and improve the detection sensitivity of the SPR sensor chip to the target molecule.

[0019] When using perovskite as an SPR sensor chip material to detect heavy metals in plants, its biocompatibility is particularly important. Because perovskite has certain toxicity, it may interact with cells in plant samples, which will affect the accuracy and reliability of the test results. Modifying the perovskite surface with polyvinyl alcohol to form a stable coating can improve its stability and enhance its biocompatibility, avoid the interaction between perovskite and cells in plant liquid samples, and improve the detection accuracy of SPR sensor chips for heavy metals.

[0020] Nanosilver-modified perovskite can enhance some of its properties in surface plasmon resonance, mainly including the following aspects: Enhanced optical signal: Nanosilver-modified perovskite can be used as an enhancer for surface-enhanced Raman spectroscopy, enhancing the optical signal through the surface plasmon resonance effect and improving detection sensitivity and resolution.

[0021] Improved sensitivity: Nanosilver modification can enhance the light absorption of perovskite, thereby improving the sensitivity in SPR detection, enabling it to detect target molecules at lower concentrations.

[0022] Improve stability: Modifying the surface of perovskite with nanosilver particles to form a composite material can increase the specific surface area and active sites of the material, increase the contact area and interaction opportunities between the perovskite two-dimensional material and the target molecules, improve its stability and reliability in SPR detection, and reduce nonspecific adsorption and interference.

[0023] 3. As a highly sensitive, real-time monitoring, non-destructive biosensing technology, the SPR sensor has a simple sample pretreatment process, and only requires the plant leaves to be dissolved in a plant solvent, which can effectively overcome the above-mentioned problems of the traditional method and be applied to the detection and analysis of heavy metal ions in plant leaves. The SPR sensor of the present invention can monitor the presence of heavy metal ions in plant leaves in real time, quickly, and with high sensitivity, providing a powerful means for environmental monitoring and food safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the present invention.

[0025] Figure 2 The sensitivity of the SPR sensor BK7-Ag-ITO-MXene sensing medium structure in Example 1-5 (a) Blade 1.

[0026] Figure 3 (b) Blade 2 is the sensitivity of the SPR sensor BK7-Ag-ITO-MXene sensing medium structure in Example 1-5.

[0027] Figure 4 The sensitivity of the SPR sensor BK7-Ag-ITO-perovskite sensing medium structure in Example 6-13 (a) Blade 1.

[0028] Figure 5 (b) Blade 2 is the sensitivity of the SPR sensor BK7-Ag-ITO-perovskite sensing medium structure in Example 6-13.

[0029] Figure 6 The sensitivity of the SPR sensor BK7-Ag-ITO-perovskite sensing medium structure in Examples 14-21 (a) Blade 1.

[0030] Figure 7 (b) Blade 2 is the sensitivity of the SPR sensor BK7-Ag-ITO-perovskite sensing medium structure in Examples 14-21.

[0031] Figure 8 Comparative Examples 1-6 Sensitivity of SPR sensors with different Ag film thicknesses (a) Leaf 1 (△n=0.014).

[0032] Fig. 9Sensitivity of the conventional SPR sensor with different Ag thicknesses for ratios 1-6 (b) Leaf 2 (△n=0.024).

[0033] Fig.10 The sensitivity of the SPR sensor BK7-Ag-ITO sensing medium structure. DETAILED DESCRIPTION

[0034] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0035] like Figure 1 As shown in the figure, a 632.8nm band SPR spectral imaging system was built using a He-Ne laser (050-LHP-021, CVI Melles Griot Inc). The system uses a He-Ne laser as a light source. The light source is emitted into the SPR sensor chip through a polarizer. The SPR sensor chip is on a rotating platform. The reflected light is captured by a complementary metal oxide semiconductor device (CMOS) camera through a 10 GHz photodetector and lens and then transmitted to the main control unit. The spectrum and image are then displayed on a computer. The computer can control the angle of the rotating platform through the main control unit to make the SPR sensor chip resonate at a certain angle, thereby obtaining characteristics such as minimum reflectivity and corresponding sensitivity.

[0036] like Figure 1 As shown in the figure, the SPR sensor consists of a prism, an Ag film, an ITO (indium tin oxide) layer, a MXene two-dimensional material, and a perovskite two-dimensional material. In this experimental device, a sapphire semi-cylindrical prism is selected to increase the component of the incident light wave vector along the interface. The prism is made of BK7 glass with a refractive index of n1 = 1.5151 and a thickness of d A1 = 200 nm. In addition, sapphire has stable performance and low wear. The semi-cylindrical prism and the rotating stage (SGSP-60YAW-W-OB, Sigma Koki Co.) are coaxial, so when the incident light enters and exits the prism, the beam will not be deflected, which simplifies the calculation. In addition, in order to avoid frequent replacement of the prism, Ag / ITO / MXene or Ag / ITO / perovskite film is coated on the sapphire substrate, which is bonded to the prism with a matching liquid with a refractive index of 1.770. The substrate is small in size and easy to clean and coat. When the SPR sensor chip reacts with the sample to be tested (heavy metal ions in the plant liquid sample), the structure and thickness of the surface of the SPR sensor chip change accordingly, resulting in a change in the refractive index, which ultimately causes the resonance angle to drift. According to this principle, the incident angle is indicated at a specific position, and when the concentration of the sample to be tested changes, the light intensity of the SPR output signal changes accordingly.

[0037] The SPR sensor preparation method includes: (1) Substrate selection and surface treatment: First, a suitable substrate material is selected, such as glass or quartz, and a thin layer of silver (Ag) is deposited on the surface as the basis for the surface enhancement effect of the SPR sensor.

[0038] (2) ITO electrode deposition: A transparent conductive indium tin oxide (ITO) film is deposited on the Ag thin layer as an electrode material to provide excellent optical transmission and electrical conductivity properties.

[0039] (3) Deposition of MXene two-dimensional materials: Select the MXene precursor MAX phase, use HF to corrode the MAX phase, ultrasonically treat it, and filter and wash it to obtain MXene. Disperse MXene in N-methylformamide (NMF) to form a MXene dispersion, coat the MXene dispersion on the ITO surface, heat treat it at 100°C, and crystallize it to obtain a MXene two-dimensional material. As a two-dimensional material with excellent conductivity and chemical stability, MXene helps to enhance charge transfer efficiency and optical properties.

[0040] Or deposition of perovskite two-dimensional materials: disperse the modified perovskite two-dimensional material in stripping liquid toluene, promote the stripping and dispersion of the modified perovskite nanomaterial under the action of ultrasound, obtain a dispersed solution of a single layer of perovskite two-dimensional material, and coat the perovskite two-dimensional material dispersed solution on the ITO surface; perform heat treatment at 100°C to promote the formation of perovskite crystals and improve the stability of the material, and prepare the perovskite two-dimensional material.

[0041] (4) Depositing multiple layers of MXene two-dimensional materials or perovskite two-dimensional materials, comprising the following steps: repeating the coating step to form a multilayer structure, and performing heat treatment after each layer is coated to improve interlayer bonding and crystallinity.

[0042] The prepared Ag-ITO-MXene / perovskite film was comprehensively evaluated for its performance, including optoelectronic properties, stability, conductivity, etc. The sensitivity and selectivity of the sensor were optimized by adjusting the thickness and combination of each layer of materials. The SPR sensor with this structure achieved multi-level functional enhancement by integrating the advantages of Ag, ITO, MXene or perovskite materials: the Ag layer provides the basis for the SPR effect, the ITO layer provides good optical and electrical properties, the MXene layer enhances charge transport and stability, and the perovskite layer optimizes the optical signal and sensitivity. These characteristics make the sensor have broad application potential in the fields of biosensing, environmental monitoring and medical diagnosis.

[0043] The preparation method of perovskite two-dimensional material comprises the following steps: (1) Modification of perovskite nanomaterials: synthesizing perovskite nanomaterials by solvothermal method, hydrothermal method, sol-gel method and other methods, mixing or co-precipitating nanosilver with perovskite nanomaterials in a molar ratio of 1:5, so that the nanosilver particles adhere to the surface of the perovskite to form a nanoparticle-modified perovskite material; mixing the nanosilver particle-modified perovskite material with polyvinyl alcohol in a molar ratio of 1:1, so that the polyvinyl alcohol is coated on the surface of the perovskite, and obtaining a modified perovskite nanomaterial modified with nanosilver and polyvinyl alcohol; (2) Solvent treatment and stripping: The modified perovskite nanomaterials are dispersed in a low-grade stripping solution of toluene, and ultrasonic waves are applied to promote the stripping and dispersion of the modified perovskite nanomaterials to obtain a dispersed solution of a single layer or multilayer perovskite two-dimensional material.

[0044] (3) Coating: Coating the perovskite two-dimensional material dispersion onto the surface of the substrate to form a uniform perovskite two-dimensional dispersion film on the substrate.

[0045] (4) Heat treatment and crystallization: After coating, appropriate heat treatment and crystallization processes are carried out to promote the formation of perovskite crystals and improve the stability of the material.

[0046] The SPR sensor device detects copper heavy metal ions in potato leaves, comprising the following steps: S1. In order to reduce the interference of external factors on the growth of potato plants, the present invention cultivates the virus-free potato leaf experimental samples in the greenhouse of Inner Mongolia Agricultural University. The nutrient solution is prepared according to the Hoagland formula, and the heavy metal (Cu 2+ ) Timed irrigation of reagents; S2. After labeling potato leaf samples containing different concentrations of heavy metal ions in the laboratory, they were dissolved into liquid samples using plant-based solvents. The SPR spectral imaging data of the 632.8 nm band were collected in sequence using the SPR sensor device according to the heavy metal ion concentration gradient to prepare a standard curve. The SPR spectral imaging system device was placed on a small six-degree-of-freedom stable electrically controlled sample stage. The He-Ne light source was vertically irradiated at the center of the prism and formed an arbitrary angle with the horizontal plane of the prism. The rotation speed of the sample stage, the exposure time of the photodetector and the CMOS camera imager were set through preliminary experiments. S3, the Cu-containing 2+ After the potato leaves were dissolved into liquid samples using plant-based solvents, the SPR spectral imaging data of the 632.8 nm band was collected using an SPR sensor device, and the Cu in the potato leaves was obtained according to the standard curve in step S2. 2+ content.

[0047] After the detection is completed, the SPR sensor chip is cleaned with a strong acid or alkaline solvent to desorb heavy metals, such as hydrochloric acid, nitric acid, sodium hydroxide, etc. These solvents can effectively desorb heavy metal ions adsorbed on the surface of the SPR sensor chip and release them from the surface of the two-dimensional material.

[0048] Examples 1-5 The prism is made of BK7 glass with a refractive index of n1 = 1.5151 and a thickness of d A1 = 200 nm, the metal is Ag film, the plant liquid sample is potato leaves dissolved in plant solvent ethyl acetate, the mass ratio of ethyl acetate to potato leaves is 1:5, and different concentrations of Cu 2+ , prepare the SPR sensor.

[0049] The plant fluid samples to be tested included two samples containing different concentrations of Cu 2+ Potato leaves, where leaf 1: potato leaf refractive index n1 = 1.376, Cu 2+ Refractive index: n1' = 0.014; Leaf 2: potato leaf refractive index n2 = 1.368, Cu 2+ The refractive index is: n2' = 0.024.

[0050] In Examples 1-5, 1 to 5 layers of MXene two-dimensional materials are added to a 30nm thick Ag film and 5nm thick ITO, respectively, to obtain an SPR sensor with a BK7-Ag-ITO-Mxene sensing medium structure. A dispersed solution of MXene two-dimensional material is coated on ITO, and a single layer of MXene two-dimensional material is obtained after heat treatment and crystallization. The coating steps are repeated, and each layer is heat treated after coating to obtain a multilayer MXene two-dimensional material. The thickness of a single layer of MXene two-dimensional material is 0.993nm, and the refractive index at λ = 632.8 nm is 2.38+1.33i. Using the SPR sensor with the BK7-Ag-ITO-MXene structure in Examples 1-5, leaf 1 and leaf 2 are used as the plant liquid samples to be tested, respectively. The sensitivity and FOM of the obtained SPR sensor are shown in FIG. Figure 2 and Figure 3 .

[0051] The SPR sensor sensitivity detection method is as follows: To investigate the sensing performance, a detailed analysis was performed using the transfer matrix method (TMM) and the Fresnel equations based on the n-layer model. For each layer, the dielectric constant (ε = n2) and the thickness of the layer (d) are the determining factors, and all layers are optically isotropic and nonmagnetic. In the electromagnetic field, the first boundary Z1 is tangential to Z = Z1 = 0. Considering the last boundary Z n-1 Tangential field, we have the control points of the first boundary Z1 (1) Where H1 and H2 are the tangential components of the first and nth layers of the electric field, respectively; W1 and W N-1 are the tangential components of the first and nth layers of the boundary magnetic field respectively; M represents the combination of the transfer matrix (TM) layer structure. The excitation light can be determined by the following relationship: (2) Among them, M k Expressed as: (3) Where P k and α k Respectively expressed as: (4) (5) In the formula, ε k and d k are the dielectric constant and the thickness of the kth layer, θ1 and λ are the incident angle and wavelength, respectively. Figure 1 As shown. The matrix of total reflected polarized light (γp) can be expressed as: (6) Where p1 represents the relationship between the prism (first layer) and the dielectric constant, p N It represents the relationship between the analyte (nth layer) and the dielectric constant. Finally, the refractive index R of polarized light can be obtained. p : (7) (8) The resonance angle is the incident angle corresponding to the minimum reflectance. By detecting the change of the resonance angle (△θ) under different refractive indices (△n) of the sensing medium, the angular sensitivity (S A ): (9) from Figure 2 It can be seen that for blade 1, the sensitivity is highest when MXene is double-layered, and the highest sensitivity and FOM are 189.14° / RIU (△θ1= 2.648 ) and 17.89 RIU respectively. - 1 . As the number of layers increases, the sensitivity gradually decreases.

[0052] from Figure 3 It can be seen that for blade 2, the sensitivity is highest when MXene is double-layered, with a maximum sensitivity of 183.63° / RIU (△θ2= 4.407°) and a FOM of 17.16 RIU - 1. As the number of layers increases, the sensitivity gradually decreases, reaching 179.42° / RIU (MXene = 3), 145.5° / RIU (MXene = 4), and 124.17° / RIU (MXene = 5), respectively.

[0053] Embodiment 6-13 In Examples 6-13, 1 to 8 layers of perovskite two-dimensional materials are added to a 30nm thick Ag film and 5nm thick ITO, respectively, to obtain a BK7-Ag-ITO-perovskite structure SPR sensor. A dispersed solution of the perovskite two-dimensional material is coated on the ITO, and a single layer of perovskite two-dimensional material is obtained after heat treatment and crystallization. The coating steps are repeated, and each layer is heat treated after coating to obtain a multilayer perovskite two-dimensional material. The single layer thickness of the perovskite two-dimensional material is 1nm, and the refractive index at λ = 632.8 nm is 2.008+0.013i. Using the BK7-Ag-ITO-perovskite structure SPR sensor in Examples 6-13, leaf 1 and leaf 2 are used as the plant liquid samples to be tested, and the sensitivity and FOM of the obtained SPR sensor are shown in FIG. Figure 4 and Figure 5 .

[0054] from Figure 4 As can be seen, for leaf 1, when the perovskite increases from a single layer to 7 layers, the sensitivity increases from 177.70° / RIU to 267.21° / RIU. When the perovskite is 7 layers, the maximum sensitivity is obtained, and the FOM is 32.63 RIU. - 1 When the perovskite layer is 8 layers, the sensitivity is 196.14° / RIU.

[0055] from Figure 5 As can be seen from the figure, for leaf 2, when the perovskite increases from a single layer to 6 layers, the sensitivity increases from 172.67° / RIU to 279.29° / RIU. When the perovskite has 6 layers, the sensitivity is the highest, and the FOM is 29.46 RIU. - 1 . After exceeding 6 layers, as the number of perovskite layers increases, the sensitivity gradually decreases, reaching 246.42° / RIU (perovskite = 7) and 196.96° / RIU (perovskite = 8), respectively.

[0056] Examples 14-21 In the BK7-Ag-ITO-perovskite structure SPR sensor of Examples 14-21, the TIO thickness is 5nm, and the thicknesses of the Ag film + perovskite two-dimensional material are 64nm+1nm, 52nm+2nm, 43nm+3nm, 38nm+4nm, 35nm+5nm, 32nm+6nm, 29nm+7nm, and 27nm+8nm, respectively.

[0057] from Figure 6 It can be seen that when the Ag film is 64nm, the ITO layer thickness is 5nm, the perovskite two-dimensional material is a single layer, and leaf 1 is used as the plant liquid sample to be tested, the SPR sensor obtains the highest sensitivity and FOM. Figure 7 As can be seen, leaf 2 is used as the plant liquid sample to be tested. The Ag film thickness is 52nm, the ITO layer thickness is 5nm, and the perovskite is double-layer. The SPR sensor obtains the highest sensitivity and FOM, with a sensitivity of 265.79° / RIU and a FOM of 51.41RIU -1 .

[0058] Comparative Examples 1-6 The prism is made of BK7 glass with a refractive index of n1 = 1.5151 and a thickness of d A1 = 200 nm, the metal is Ag film, and the sensing medium is dissolved Cu 2+ Potato leaf liquid sample was used to prepare SPR sensor. The thickness of Ag film in Comparative Examples 1-6 was 10 nm, 20 nm, 25 nm, 30 nm, 40 nm and 50 nm, respectively.

[0059] The plant samples to be tested included two species containing different concentrations of Cu 2+ Potato leaves, where leaf 1: the refractive index of potato leaves is n1=1.376, and the refractive index of Cu ions is n1'=0.014; leaf 2: the refractive index of potato leaves is n2=1.368, and the refractive index of Cu ions is n2'=0.024.

[0060] Through simulation analysis, the sensitivity and FOM value of the SPR sensor in Examples 1-6 were detected.

[0061] Test results such as Figure 8 , Fig. 9 As shown, for blade 1 Figure 8 As shown, for a 10 nm thick Ag, the sensitivity of the SPR sensor is 71.64° / RIU and the FOM value is 6.57 RIU -1When the thickness of Ag is 20 nm, the sensitivity of the SPR biosensor is 62.9° / RIU. When the thickness of Ag is 25 nm, the sensitivity and FOM of the SPR biosensor are 142.85° / RIU and 20.15RIU, respectively. -1 When the Ag thickness is 30 nm, the sensitivity and FOM of the SPR biosensor are 146.86° / RIU and 22.68 RIU, respectively. -1 For Ag with a thickness of 40 nm, the sensitivity of the SPR biosensor is 140.16° / RIU and the FOM value is 20.14 RIU -1 The sensitivity and FOM of the Ag (50 nm) thin film SPR sensor are 135.14° / RIU and 19.83RIU, respectively. -1 The sensitivity and FOM of the SPR biosensor were the highest when the Ag thickness was 30 nm, and then the sensitivity and FOM values ​​of the SPR sensor gradually decreased with the increase of Ag thickness.

[0062] For leaf 2 Fig. 9 For Ag with a thickness of 10 nm, the sensitivity of the SPR sensor is 71.04° / RIU and the FOM value is 6.43 RIU -1 When the thickness of Ag is 20 nm, the sensitivity and FOM of the SPR biosensor are 62.7° / RIU. When the thickness of Ag is 25 nm, the sensitivity and FOM of the SPR biosensor are 138.25° / RIU and 19.38RIU, respectively. -1 When the Ag thickness is 30 nm, the sensitivity and FOM of the SPR biosensor are 144° / RIU and 27.64RIU, respectively. -1 For Ag with a thickness of 40 nm, the sensitivity of the SPR biosensor is 138.78° / RIU and the FOM value is 19.57RIU -1 The sensitivity and FOM of the Ag (50 nm) thin film SPR sensor are 131.38° / RIU and 18.48 RIU, respectively. -1 The sensitivity and FOM of the SPR biosensor were the highest when the Ag thickness was 30 nm, and then the sensitivity and FOM values ​​of the SPR sensor gradually decreased with the increase of Ag thickness.

[0063] Comparative Example 7 Based on Comparative Example 4, an ITO layer was added. A 5 nm thick ITO layer was added to a 30 nm thick Ag film to form a BK7 - Ag - ITO SPR sensor. The refractive index of ITO at λ = 632.8 nm was 1.858+0.058i. Using the BK7 - Ag - ITO SPR sensor, leaf 1 and leaf 2 were used as plant liquid samples to be tested. The sensitivity and FOM of the SPR sensor were shown in Figure 2. Figure 4 .

[0064] from Fig.10 As can be seen in the graph, for blade 1, the maximum sensitivity is 146.85° / RIU (△θ1 = 2.369°). Subsequently, for blade 2, the sensitivity is 164.95° / RIU (△θ2 = 3.954°).

[0065] It can be seen from the above embodiments and comparative examples that the optimal sensitivity can be obtained by adopting the BK7-Ag-ITO-perovskite structure, and the perovskite two-dimensional material can greatly improve the sensitivity of the SPR sensor chip.

[0066] For matters not mentioned above, the prior art applies.

[0067] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. An SPR sensor chip based on two-dimensional materials, characterized in that: It comprises a prism, on which a metal layer, an indium tin oxide layer and a two-dimensional material layer are sequentially covered, and the two-dimensional material is a MXene two-dimensional material or a perovskite two-dimensional material.

2. The SPR sensor chip based on two-dimensional materials according to claim 1, characterized in that: The preparation method of the perovskite two-dimensional material comprises the following steps: S1, modifying the perovskite nanomaterial with nanosilver and polyvinyl alcohol to obtain a modified perovskite nanomaterial; S2, solvent treatment and stripping: dispersing the modified perovskite nanomaterial in a stripping solution, promoting the stripping and dispersion of the modified perovskite nanomaterial under the action of ultrasound, and obtaining a single-layer modified perovskite two-dimensional material dispersion; S3, coating: coating the modified perovskite nanomaterial dispersion onto the surface of the indium tin oxide layer to form a uniform perovskite two-dimensional material dispersion film on the substrate; S4. Heat treatment and crystallization: Heat treatment forms perovskite two-dimensional materials.

3. The SPR sensor chip based on two-dimensional materials according to claim 1, characterized in that: The thickness of the indium tin oxide layer is 1-5 nm.

4. The SPR sensor chip based on two-dimensional materials according to claim 1, characterized in that: The MXene two-dimensional material has 1 to 5 layers, and the thickness of a single layer of the MXene two-dimensional material is 0.993 nm.

5. The SPR sensor chip based on two-dimensional materials according to claim 1, characterized in that: The perovskite two-dimensional material has 1 to 8 layers, and the thickness of a single layer of the perovskite two-dimensional material is 1 nm.

6. The SPR sensor chip based on two-dimensional materials according to claim 1, characterized in that: The metal layer is a Ag film, and the thickness of the Ag film is 10-50 nm.

7. A method for preparing a SPR sensor chip based on two-dimensional materials according to any one of claims 1 to 6, characterized in that: The steps include: S1, selecting glass as the substrate material and depositing an Ag film on the surface of the substrate material; S2, depositing an ITO thin film on the Ag film; S3. Depositing MXene two-dimensional material or perovskite two-dimensional material on the ITO film to obtain an SPR sensor chip.

8. An SPR sensor based on two-dimensional materials, comprising the SPR sensor chip according to any one of claims 1 to 6.

9. The method for detecting heavy metal ions in plant leaves using an SPR sensor according to claim 8, characterized in that: The following steps are involved: S1. Plants are cultivated in a greenhouse, and heavy metal reagents are regularly irrigated using an orthogonal experimental method to obtain plant leaves containing heavy metal ions at different concentrations; S2. Dissolve plant leaves containing heavy metal ions of different concentrations into standard liquid samples using plant-based solvents, and use SPR sensors to collect SPR spectral imaging data of the standard liquid samples at 632.8 nm in accordance with the concentration gradient of heavy metal ions in the standard liquid samples to prepare a standard curve; S3. After the plant leaves containing heavy metal ions to be tested are dissolved into a liquid sample to be tested using a plant-type solvent, an SPR sensor is used to collect SPR spectral imaging data of the liquid sample to be tested at 632.8 nm, and the heavy metal ion content in the plant leaves containing heavy metal ions is obtained according to the standard curve in step S2.

10. The method for detecting heavy metal ions in plant leaves using an SPR sensor according to claim 9, characterized in that: The heavy metal ions include Hg 2+ 、Cd 2+ , Pb 2+ Cr 2+ Cr 3+ Cr 6+ 、Zn 2+ , Cu 2+ One of them.

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