A bimetallic functionalized SERS substrate for trace detection of organophosphine nerve agents and a preparation method thereof

Abstract

The present invention belongs to the technical field of surface enhanced Raman scattering, and in particular, is a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents and a preparation method thereof. The present invention comprises a metal substrate, which is composed of a metal B as a base material and a metal A coated on the surface of the metal B, and the surface of the metal A is modified with a capture agent molecule that can be specifically chemically bonded with the nerve agent; the capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group. The present invention generates a local electric field by constructing a bimetallic contact potential, thereby enhancing the activity of the capture agent molecules on the surface of the noble metal, and thus realizing efficient detection of nerve agents such as sarin.

Description

Technical Field

[0001] The invention belongs to the technical field of surface enhanced Raman scattering, and in particular relates to a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents and a preparation method thereof. Background Art

[0002] Nerve agents such as sarin are highly lethal, and trace detection in complex environments such as water and atmosphere is of great significance to public safety. At present, traditional laboratory analysis techniques such as chromatography and mass spectrometry are highly sensitive, but the pre-treatment is cumbersome and time-consuming, making it difficult to apply them to rapid on-site detection; and the fluorescence method used for rapid on-site detection is easily interfered by analogs, resulting in false positives. Molecular detection technology based on precious metal surface enhanced Raman scattering (SERS) has the advantages of fast speed, fingerprint recognition, and sensitivity, and is expected to be used for accurate identification and trace detection of nerve agents in complex environments.

[0003] However, nerve agent molecules are typical weakly interacting molecules, and it is difficult to stably adsorb on the surface of precious metal substrates for direct detection. Therefore, researchers have proposed a SERS detection method based on chemical capture. For example, Qian Zhao et al. proposed in "SERS-based ultrasensitive detection of organophosphorus nerve agents via substrate's surface modification" (Journal of Hazardous Materials, 324, 2017, 194-202) that mercaptoethylamine is modified on the surface of the gold cone array as a capture agent molecule, and trace amounts of methylphosphonic acid (a sarin simulant) in the solution are captured on the substrate surface through an amide reaction, thereby achieving SERS detection. However, due to the insufficient bonding ability of mercaptoethylamine with the target molecule, a coupling agent with a strong activation effect is required to participate in the reaction process, so it can only be applied to the detection of targets in water environments, and the detection time is long.

[0004] Therefore, there is an urgent need for a bimetallic functionalized SERS substrate and a preparation method thereof for trace detection of organophosphine nerve agents to solve the above problems. Summary of the invention

[0005] In order to overcome the above defects in the prior art, the present invention provides a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents and a preparation method thereof. The present invention achieves efficient detection of nerve agents such as sarin.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents includes a metal substrate, which is composed of a metal B as a base material and a metal A covering the surface of the metal B. The surface of the metal A is modified with a capture agent molecule that can specifically chemically bond with the nerve agent; the capture agent molecule is composed of a thiol group, an aromatic ring, and a strong charge-donating functional group. Due to the steric hindrance effect, the capture agent molecule will be preferentially adsorbed on the A metal, and a small amount of the capture agent molecule will also be adsorbed on the B metal.

[0008] Preferably, the work function of metal A is smaller than the work function of metal B, so that a contact potential can be generated between metal B and metal A, providing a surface electrostatic field.

[0009] Preferably, metal B is one of gold, silver and copper.

[0010] Preferably, the aromatic ring is one or a combination of two or more of a benzene ring, a pyridine ring and a pyrrole ring.

[0011] Preferably, the strong charge-donating functional group is one or a combination of two or more of an amine functional group, an oxime functional group and an alkoxy functional group.

[0012] Preferably, the particle diameter of metal B is 50-150 nm.

[0013] Preferably, the particle diameter of metal A is 0.5-2 nm.

[0014] Preferably, the general structural formula of the capture agent molecule is:

[0015]

[0016] The value ranges of n1 and n2 are both 0-5, and n3 is 0 or 1.

[0017] To achieve the second objective, the present invention provides a method for preparing a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents, the specific steps of which are as follows:

[0018] S1. Preparing a Raman-active metal B on the surface of a substrate by a physical method or a chemical method;

[0019] S2, using a magnetron sputtering method to deposit metal A on the surface of metal B to obtain a metal substrate;

[0020] S3. Prepare a capture agent solution, immerse the metal substrate in the capture agent solution for 1-60 minutes, and obtain a bimetallic functionalized SERS substrate for trace detection of organophosphine nerve agents.

[0021] Preferably, the molar concentration of the capture agent solution is 10 -6 -10 -3 M.

[0022] Preferably, the substrate is one of a silicon wafer, a glass wafer and a quartz wafer, and the size of the substrate is 3-30 mm. 2 ; The sputtering current of magnetron sputtering is 1-10mA and the time is 10-200s.

[0023] The advantages of the present invention are:

[0024] (1) The bimetallic functionalized SERS substrate of the present invention is a new type of SERS substrate based on substrate component optimization. It generates a local electric field by constructing a bimetallic contact potential, thereby enhancing the activity of the metal surface capture agent molecules, thereby achieving efficient detection of nerve agents such as sarin.

[0025] (2) The thiol group in the capture agent molecule of the present invention is used to bind to the metal A substrate; the benzene ring / pyridine ring / pyrrole ring is used to increase the Raman scattering cross section to improve the detection limit; the amine group / oxime group / alkoxy group has a strong affinity for nerve agents and can covalently bond with the nerve agent molecules to achieve capture.

[0026] (3) The bimetallic functionalized SERS substrate prepared by the present invention is not only suitable for liquid phase environment detection, but also suitable for gas phase environment detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the bimetallic functionalized SERS substrate structure of the present invention.

[0028] Figure 2 This is a spectrum diagram of Example 1 of the present invention.

[0029] Figure 3 This is a spectrum diagram of Example 2 of the present invention.

[0030] Figure 4 This is a principle analysis diagram of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0032] like Figure 1-4 As shown, a bimetallic functionalized SERS substrate for the trace detection of organophosphine nerve agents, the surface of the metal substrate is modified with a capture agent molecule that can specifically chemically bond with the nerve agent. The metal substrate is composed of a metal B as a base material and a metal A coated on the surface of the metal B, and the capture agent molecule is composed of a thiol group, an aromatic ring, and a strong charge-donating functional group.

[0033] Based on the principle of classic oximation reaction, the capture agent molecule uses chlorocyanopyridine as raw material, firstly thiolates it through the action of a sulfiding agent, and then undergoes amidoximation through the action of hydroxylamine hydrochloride, thereby achieving the synthesis of pyridinethioamidoamidoximate, and finally obtaining the capture agent molecule of the present invention.

[0034] Example 1

[0035] An Ag-Pt solid substrate is used as the metal substrate.

[0036] Prepare capture agent solution:

[0037] The structural formula of the capture agent molecule is:

[0038]

[0039] S1. Weigh and dissolve the capture agent molecules in ethanol solvent and prepare 50mL of 10 molar concentration in a volumetric flask. -4 M capture agent molecule ethanol solution, as capture agent solution 1;

[0040] S2. Use a pipette to take 5 mL of the capture agent solution 1 to a 50 mL volumetric flask and dilute to the mark with anhydrous ethanol to obtain a molar concentration of 10 -5 M capture agent molecule ethanol solution, as capture agent solution 2;

[0041] S3, use a pipette to take 5mL of the capture agent solution 2 to a 50mL volumetric flask, and dilute to the mark with anhydrous ethanol to obtain a molar concentration of 10 -6 M capture agent molecule ethanol solution is used as capture agent solution 3.

[0042] Prepare organophosphorus nerve agent solution:

[0043] S1, weigh and use a volumetric flask to prepare 50mL of 10 -3 M of an organophosphorus nerve agent aqueous solution, as test solution 1;

[0044] S2. Use a pipette to transfer 5 mL of test solution 1 to a 50 mL volumetric flask and dilute to the mark with deionized water to obtain a molar concentration of 10 -4 M of an organophosphorus nerve agent aqueous solution, as test solution 2;

[0045] S3. Use a pipette to transfer 5 mL of test solution 1 to a 50 mL volumetric flask and dilute to the mark with deionized water to obtain a molar concentration of 10 -5 M of an organophosphorus nerve agent aqueous solution, as test solution 3;

[0046] S4. Use a pipette to transfer 5 mL of test solution 1 to a 50 mL volumetric flask and dilute to the mark with deionized water to obtain a molar concentration of 10-6 M of an organophosphorus nerve agent aqueous solution, as test solution 4;

[0047] S5. Use a pipette to transfer 5 mL of test solution 1 to a 50 mL volumetric flask and dilute to the mark with deionized water to obtain a molar concentration of 10 -7 M of an organophosphorus nerve agent aqueous solution, as test solution 5;

[0048] S6. Use a pipette to transfer 5 mL of test solution 1 to a 50 mL volumetric flask and dilute to the mark with deionized water to obtain a molar concentration of 10 -8 M of an organophosphorus nerve agent aqueous solution was used as the test solution 6.

[0049] Once you have prepared your capture agent solution and OPNA solution, follow these steps:

[0050] S1. Surface modification of metal substrate: The molar concentration of 10 -6 M(10 -4 M~10 -6 The capture agent molecule ethanol solution of (M) was transferred to a 100mL beaker, and the pure Ag solid substrate and the Ag-Pt solid substrate with Pt layer thickness of 1nm, 2nm and 3nm were uniformly dispersed and placed on the bottom of the beaker in turn, keeping the sensitive structure facing upward; then the modified solution beaker was placed in a 30℃ water bath and allowed to stand for 10 minutes; then the pure Ag solid substrate and the Ag-Pt solid substrate were taken out in turn with clean tweezers and dried naturally, and the samples were marked.

[0051] S2. Capture agent molecular spectrum collection: The modified pure Ag solid substrate and Ag-Pt solid substrate are transferred to a glass slide in turn, placed on the sample stage of a portable Raman spectrometer, the excitation wavelength is 785 nm, and appropriate test conditions are set (such as laser power 15 mW, integration time 5 s, integration times 1 time), and the Raman spectrum of the pure Ag solid substrate is collected (Ag-Pt is a metal and has no Raman signal).

[0052] S3, with organophosphorus nerve agents: the molar concentration of 10 -8 M(10 -3 M~10 -8 The organophosphorus nerve agent aqueous solution (M) is transferred to a 100mL beaker, and the solid substrates in step S2 are uniformly dispersed along the wall of the beaker and placed on the bottom of the beaker in turn, with the sensitive structure facing upward; then the test solution beaker is placed in a magnetic stirring water bath at 25°C and stirred for 20 minutes (speed 500r / min); then the pure Ag solid substrate and the Ag-Pt solid substrate are taken out in turn with clean tweezers and dried naturally, and the samples are marked.

[0053] S4. Collection of molecular spectra of organophosphorus agents: The pure Ag solid substrate and the Ag-Pt solid substrate after the reaction are transferred to a glass slide in turn, placed on the sample stage of a portable Raman spectrometer, and the Raman spectra of the pure Ag solid substrate and the Ag-Pt solid substrate are collected in turn according to the operation in step S2.

[0054] After the above steps, we can get Figure 2 The test results are shown in Figure 1. Spectrum line I is the SERS spectrum of the capture agent molecule collected on a pure Ag solid substrate before the reaction. Spectra lines II, III, IV, and V are the spectra of the pure Ag solid substrate and the Ag-Pt solid substrate with a Pt layer thickness of 1nm, 2nm, and 3nm respectively after the reaction with the organophosphorus nerve agent, located at 760cm -1 The Raman peak at represents the carbon-phosphine bond vibration of organophosphorus nerve agents (V C-P ), and the remaining Raman peaks are from the capture agent molecules. Compared with the pure Ag solid substrate, the carbon-phosphine bond vibration (V C-P ) intensity increases significantly with the increase of Pt layer thickness, indicating that the Ag-Pt heterostructure improves the reactivity of the capture agent molecules and nerve agent molecules and improves the capture efficiency. The Ag-Pt solid substrate can realize trace detection of organophosphorus nerve agents.

[0055] Example 2

[0056] An Ag-Pd solid substrate is used as the metal substrate.

[0057] First, prepare capture agent solution 1, capture agent solution 2, capture agent solution 3, test solution 1, test solution 2, test solution 3, test solution 4, test solution 5, and test solution 6 according to the steps in Example 1. Then perform the test according to the following steps:

[0058] S1. Surface modification of metal substrate: The molar concentration of 10 -6 M(10 -4 M~10 -6 The capture agent solution 1 (M) was transferred into a 100mL beaker, and the pure Ag solid substrate and the Ag-Pd solid substrate with Pd layer thickness of 1nm, 2nm and 3nm were uniformly dispersed and placed on the bottom of the beaker in turn, with the sensitive structure facing upward; then the modified solution beaker was placed in a 30°C water bath and allowed to stand for 10 minutes; then the pure Ag solid substrate and the Ag-Pd solid substrate were taken out in turn with clean tweezers and dried naturally, and the samples were marked.

[0059] S2. Collection of capture agent molecular spectra: The modified pure Ag solid substrate and Ag-Pd solid substrate were transferred to a glass slide in turn, placed on the sample stage of a portable Raman spectrometer, the excitation wavelength was 785 nm, appropriate test conditions were set (such as laser power 15 mW, integration time 5 s, integration times 1), and the Raman spectrum of the pure Ag solid substrate was collected (Ag-Pd is a metal and has no Raman signal).

[0060] S3, with organophosphorus nerve agents: the molar concentration of 10 -8 M(10 -3 M~10 -8 The organophosphorus nerve agent aqueous solution (M) is transferred to a 100mL beaker, and the solid substrates in step S2 are uniformly dispersed along the wall of the beaker and placed on the bottom of the beaker in turn, with the sensitive structure facing upward; then the test solution beaker is placed in a magnetic stirring water bath at 25°C and stirred for 20 minutes (speed 500r / min); then the pure Ag solid substrate and the Ag-Pd solid substrate are taken out in turn with clean tweezers and dried naturally, and the samples are marked.

[0061] S4. Collection of molecular spectra of organophosphorus agents: The pure Ag solid substrate and the Ag-Pd solid substrate after the reaction are transferred to a glass slide in turn, placed on the sample stage of a portable Raman spectrometer, and the Raman spectra of the pure Ag solid substrate and the Ag-Pd solid substrate are collected in turn according to the operation in step S2.

[0062] After the above steps, we can get Figure 3 The test results are shown in Figure 1. Among them, line I is the SERS spectrum of the capture agent molecule collected on the pure Ag solid substrate before the reaction. Line II, line III, line IV, and line V are the spectra of the pure Ag solid substrate and the Ag-Pd solid substrate with a Pd layer thickness of 1nm, 2nm, and 3nm respectively after the reaction with the organophosphorus nerve agent, located at 760cm -1 The Raman peak at represents the carbon-phosphine bond vibration of organophosphorus nerve agents (V C-P ), and the remaining Raman peaks are from the capture agent molecules. Compared with the pure Ag solid substrate, the carbon-phosphine bond vibration (V C-P ) intensity increases significantly with the increase of Pd layer thickness, indicating that the Ag-Pd heterostructure improves the reactivity of the capture agent molecules and nerve agent molecules and improves the capture efficiency. The Ag-Pd solid substrate can realize trace detection of organophosphorus nerve agents.

[0063] Analysis of the principle of detecting organophosphine nerve agents using bimetallic functionalized SERS substrates: When two metals B and the second phase with different work functions come into contact, electrons flow from the side with high chemical potential (W) to the side with low chemical potential, making the metal surface charged and generating different potentials VA and V B , called the contact potential [such as Figure 4 a]; Due to the existence of positive and negative charges on the surface, an electrostatic field with a specific intensity and direction will be generated within the spatial region of the metal heterostructure [as shown in Figure 4 [As shown in b]; therefore, when the capture agent molecules are adsorbed on the surface of the metal heterostructure, they will also be in this localized spatial electric field, which will affect their reaction activity.

[0064] like Figure 4 As shown: (a) Two metals with different work functions form a heterostructure. Electron migration causes the surface to carry positive and negative charges and generate contact potential; (b) COMSOL Multiphysics software is used to simulate the distribution of the in-situ spatial electric field of the gold-silver heterostructure.

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bimetallic functionalized SERS substrate for trace detection of organophosphine nerve agents, characterized in that: The invention comprises a metal substrate, wherein the metal substrate is composed of a metal B as a base material and a metal A covering the surface of the metal B, wherein the surface of the metal A is modified with a capture agent molecule that can specifically chemically bond with a nerve agent; the capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group; the work function of the metal A is smaller than the work function of the metal B; and the metal B is one of gold, silver and copper; The general structural formula of the capture agent molecule is: ； The value ranges of n1 and n2 are both 0-5, and n3 is 0 or 1.

2. The bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents according to claim 1, characterized in that: The particle diameter of the metal B is 50-150 nm; the particle diameter of the metal A is 0.5-2 nm.

3. A method for preparing a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents as claimed in any one of claims 1 to 2, characterized in that , the specific steps are as follows: S1. Preparing a Raman-active metal B on the surface of a substrate by a physical method or a chemical method; S2, using a magnetron sputtering method to deposit metal A on the surface of metal B to obtain a metal substrate; S3. Prepare a capture agent solution, immerse the metal substrate in the capture agent solution for 1-60 minutes, and obtain a bimetallic functionalized SERS substrate for trace detection of organophosphine nerve agents.

4. The method for preparing a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents according to claim 3, characterized in that The molar concentration of the capture agent solution is 10 -6 -10 -3 M.

5. The method for preparing a bimetallic functionalized SERS substrate for detecting trace amounts of organophosphine nerve agents according to claim 3, characterized in that The substrate is one of a silicon wafer, a glass wafer and a quartz wafer, and the size of the substrate is 3-30 mm. 2 ; The sputtering current of the magnetron sputtering is 1-10mA and the time is 10-200s.

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