A bimolecular co-modified metal SERS substrate for nerve agent detection and its preparation method

Abstract

The present invention belongs to the technical field of surface enhanced Raman scattering, and in particular, is a bimolecular co-modified metal SERS substrate for nerve agent detection and a preparation method thereof. The present invention includes a capture agent molecule for selectively capturing nerve agent molecules and an auxiliary enhancement molecule for enhancing the capture ability of the capture agent molecule. The capture agent molecule and the auxiliary enhancement molecule are both modified on a metal SERS substrate with Raman activity. The capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group, and the auxiliary enhancement molecule is composed of a thiol group and an electron-withdrawing group. The metal SERS substrate prepared by the present invention exhibits a specific electronic effect as a whole, realizes a gentle, convenient and efficient reaction rate regulation, and greatly improves the capture ability of the capture agent molecule and the target agent.

Description

Technical Field

[0001] The invention belongs to the technical field of surface enhanced Raman scattering, and in particular relates to a bimolecular co-modified metal SERS substrate for nerve agent detection and a preparation method thereof. Background Art

[0002] The interaction between nerve agents (sarin, tabun, soman, etc.) and the surface of metal SERS substrates is very weak, and they cannot be effectively enriched in the surface enhanced signal area, making it difficult to achieve efficient detection based on the surface enhanced Raman scattering (SERS) effect. Generally, modifying the surface of metal SERS substrates with organic molecules with specific bonding to indirectly capture and enrich target molecules is an effective way to achieve high-performance SERS detection of weakly interacting molecules. However, when the capturer molecules are modified on the metal surface, due to the electron transfer between the capturer molecules and the metal, and the influence of the substrate surface microstructure, the energy level structure, adsorption configuration and surface electrostatic potential of the molecules are greatly changed, thereby greatly reducing the chemical reactivity of the capturer molecules with the target agent and the bonding efficiency to the target molecule. However, there has long been a lack of effective technical approaches to regulate the reactivity of molecules on the surface of nanostructures, and only in recent years has some progress been made.

[0003] In chemical reactions, the transition, addition, and departure of electrons between reactants lead to the formation and breaking of chemical bonds. Based on this principle, if a specific electric field is applied to the reactant molecules on the metal surface and the movement of electrons is affected, it is expected that the reactivity can be regulated. It was not until 2016 that Spanish scholar Michelle L. Coote used a scanning tunneling microscope (STM) probe to precisely apply a directional electric field to the reactant molecules on the surface of the gold electrode, and for the first time experimentally observed the acceleration of the famous organic reaction Diels-Alder reaction under an external electric field; subsequently, in 2020, the Korean Mu-Hyun Baik team bonded the reactant molecules to the surface of the gold electrode, and successfully regulated the progress of three classic organic chemical reactions (ester hydrolysis, amide reaction, and cross-coupling reaction) by applying positive and negative voltages of specific strengths (-0.15V to 0.7V). These studies have shown that the external directional electric field has a significant regulatory ability on the chemical reactivity of surface molecules. However, since its regulatory efficiency strongly depends on the precise control of the external electric field strength and direction, it is necessary not only to consider the limited voltage tolerance of the molecules, but also to require the assistance of external complex equipment.

[0004] Therefore, there is an urgent need for a bimolecular co-modified metal SERS substrate for nerve agent detection and a preparation method thereof to solve the above problems. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned prior art, the present invention provides a bimolecular co-modified metal SERS substrate for nerve agent detection and a preparation method thereof. The metal SERS substrate of the present invention exhibits a specific electronic effect as a whole, realizes gentle, convenient and efficient reaction rate regulation, and greatly improves the capture ability of the capture agent molecules and the target agent.

[0006] To achieve one of the above purposes, the present invention adopts the following technical solution:

[0007] A bimolecular co-modified metal SERS substrate for nerve agent detection includes a capture agent molecule for selectively capturing nerve agent molecules and an auxiliary enhancement molecule for enhancing the capture ability of the capture agent molecule. Both the capture agent molecule and the auxiliary enhancement molecule are modified on a metal SERS substrate with Raman activity. The capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group, and the auxiliary enhancement molecule is composed of a thiol group and a charge-withdrawing group.

[0008] Preferably, the metal SERS substrate is one of gold, silver and copper.

[0009] Preferably, the aromatic ring is one or a combination of two or more of a pyridine ring and a pyrrole ring.

[0010] 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.

[0011] Preferably, the electron-withdrawing group is one or a combination of two or more of a sulfonic acid group, a cyano group, a nitro group and a trifluoromethyl group.

[0012] Preferably, the molar concentration of the capture agent molecules is 10 -2 mol / L-10 -6 mol / L.

[0013] Preferably, the molar concentration of the auxiliary enhancing molecule is 10 -2 mol / L-10 -6 mol / L.

[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] Preferably, the thiol groups in the capture agent molecules and the auxiliary enhancement molecules are chemically bonded to the surface of the metal SERS substrate to form metal-sulfur bonds, so that the capture agent molecules and the auxiliary enhancement molecules are self-assembled on the surface of the metal SERS substrate by a mixed solution co-adsorption method to form a mixed self-assembled monolayer.

[0018] To achieve the second objective, the present invention provides a method for preparing a bimolecular co-modified metal SERS substrate for nerve agent detection, the specific steps of which are as follows:

[0019] S1. Prepare the metal SERS substrate and configure 10 -2 mol / L-10 -6 mol / L molar concentration of capture agent molecules and 0 - 2 mol / L-10 -6 mol / L molar concentration of auxiliary enhancing molecules;

[0020] S2. Add auxiliary enhancement molecules to the capture agent molecules to obtain a mixed solution, and then place the metal SERS substrate in the mixed solution, and then take it out and dry it to obtain a metal SERS substrate.

[0021] Preferably, in step S2, the metal SERS substrate is placed in the mixed solution for 10 min to 24 h.

[0022] The advantages of the present invention are:

[0023] (1) The metal SERS substrate prepared by the present invention has auxiliary enhancement molecules with specific electrical effects inserted near the capture agent molecules on the surface of the nanostructure, and the electrical effect and insertion amount of the inserted auxiliary enhancement molecules are changed, so that the metal SERS substrate as a whole presents a specific electronic effect, achieving gentle, convenient and efficient reaction rate regulation, and greatly improving the capture ability of the capture agent molecules and the target toxic agent.

[0024] (2) The metal SERS substrate in the present invention has a strong Raman enhancement effect; the thiol group in the capture agent molecule is used to combine with the metal SERS 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 is used to covalently bond with the nerve agent molecule to achieve capture; the auxiliary enhancement molecule is composed of a thiol group and an electron-absorbing group (such as a sulfonic acid group, a cyano group, a nitro group, a trifluoromethyl group, etc.), which can transfer the electron-absorbing effect to the capture agent molecule through the metal SERS substrate, thereby enhancing its covalent bonding ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the present invention.

[0026] Figure 2It is a schematic diagram of the self-assembled monolayer of capture agent molecules and auxiliary enhancement molecules of different concentrations on the surface of the metal SERS substrate of the present invention.

[0027] Figure 3 This is a spectrum diagram of Example 1 of the present invention, that is, a spectrum diagram of the capture effect of a metal SERS substrate modified by a mixed modification solution of capture agent molecules and 4-nitrothiophenol at different molar ratios on nerve agents.

[0028] Figure 4 This is a spectrum diagram of Example 2 of the present invention, that is, a spectrum diagram of the capture effect of a metal SERS substrate modified by a mixed modification solution of capture agent molecules and sodium 2,3-dimercaptopropane sulfonate at different molar ratios on nerve agents.

[0029] Figure 5 This is a spectrum diagram of Example 3 of the present invention, that is, a spectrum diagram of the capture effect of a metal SERS substrate modified by a mixed modification solution of capture agent molecules and 4-(trifluoromethyl)thiophenol at different molar ratios on nerve agents. DETAILED DESCRIPTION

[0030] 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.

[0031] like Figure 1 As shown, a bimolecular co-modified metal SERS substrate for nerve agent detection is composed of a capture agent molecule, an auxiliary enhancement molecule and a metal SERS substrate. Both the capture agent molecule and the auxiliary enhancement molecule are modified on a metal SERS substrate with Raman activity. The capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group, and the auxiliary enhancement molecule is composed of a thiol group and a charge-withdrawing group.

[0032] Specifically, the thiol groups in the capture agent molecules and the auxiliary enhancement molecules are chemically bonded to the surface of the metal SERS substrate to form a metal-sulfur bond (i.e., gold-sulfur bond, silver-sulfur bond, or copper-sulfur bond, etc.); the capture agent molecules and the auxiliary enhancement molecules form a mixed self-assembled monolayer on the surface of the metal SERS substrate; Figure 2 As shown, I, II, III, and IV are molar concentrations of 10 -3 M, 10 -4 M, 10 -5 M, 10 -6 The modification state of the capture agent molecules M and the auxiliary enhancement molecules in appropriate proportion on the surface of the SERS substrate is as follows: Figure 2 It can be seen that as the concentration of capture agent molecules decreases, the self-assembled monolayer becomes increasingly sparse.

[0033] Furthermore, the general structural formula of the capture agent molecule is:

[0034]

[0035] The value ranges of n1 and n2 are both 0-5, and n3 is 0 or 1.

[0036] 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.

[0037] A method for preparing a bimolecular co-modified metal SERS substrate for nerve agent detection:

[0038] The preparation method of the metal SERS substrate is as follows:

[0039] A: Metal SERS substrate with array structure

[0040] First, based on the gas-liquid interface self-assembly method, polystyrene microspheres are self-assembled on a silicon wafer or a glass wafer to form a hexagonal close-packed array structure (the size of the polystyrene microspheres is 100nm~500nm); then, metal is sputtered on the polystyrene array structure by magnetron sputtering coating (sputtering target: gold, silver, copper or gold-silver alloy; sputtering current: 5mA~40mA) to obtain a metal SERS substrate with an array structure.

[0041] B: Sol-metal SERS substrate in the form of nanoparticles

[0042] Preparation method of gold sol SERS substrate:

[0043] S1. Preparation of 17 nm gold seeds: 48 mL of deionized water was added to a round-bottom flask and boiled; 0.5 mL of 0.5 wt% chloroauric acid solution was added under boiling conditions, and the mixture was stirred and boiled for 10 minutes; then 1.5 mL of 1.0 wt% sodium citrate solution was added, and the mixture was stirred and boiled for 30 minutes; the mixture was cooled to room temperature, and water was added to make the volume 50 mL to obtain 17 nm gold seeds;

[0044] S2. Preparation of 100 nm gold particles: 45 mL of deionized water was added to a round-bottom flask and boiled; 2 mL of 0.1 M tris(hydroxymethyl)aminomethane solution was added, stirred and boiled for 5 minutes; 0.5 mL of gold seeds and 2.0 mL of 0.5 wt % chloroauric acid solution were added, stirred and boiled for 30 minutes; cooled to room temperature, and water was added to make up to 50 mL to obtain 100 nm gold particles, i.e., a gold sol SERS substrate was obtained.

[0045] Preparation method of gold-silver sol SERS substrate:

[0046] S1. Preparation of 17 nm gold seeds: 48 mL of deionized water was added to a round-bottom flask and boiled; 0.5 mL of 0.5 wt% chloroauric acid solution was added under boiling conditions, and the mixture was stirred and boiled for 10 minutes; then 1.5 mL of 1.0 wt% sodium citrate solution was added, and the mixture was stirred and boiled for 30 minutes; the mixture was cooled to room temperature and the volume was adjusted to 50 mL to obtain 17 nm gold seeds;

[0047] S2. Preparation of 90 nm gold-silver particles: 1 mL of 0.1 M sodium citrate and 90 mL of deionized water were added into a 250 ml round-bottom flask. Under rapid stirring, 1 mL of gold seeds was added, and then 1.0 mL of 0.05 M silver nitrate solution and 1 mL of 0.05 M ascorbic acid solution were quickly added. The mixture was allowed to react for 30 minutes, and water was added to make the volume 100 mL to obtain 90 nm gold-silver particles, that is, a gold-silver sol SERS substrate was obtained.

[0048] Preparation method of silver sol SERS substrate:

[0049] S1. Preparation of 14 nm silver seeds: add 20 mL of 1.0 wt% sodium citrate solution to 75 mL of deionized water, heat to 70°C, add 1.7 mL of 1.0 wt% silver nitrate solution at one time, then add 2 mL of 0.1 wt% sodium borohydride solution, stir for one hour, then cool naturally to room temperature, add water to 100 mL to obtain 14 nm silver seeds;

[0050] S2. Preparation of 80 nm silver particles: Add 220 μL of 0.1 M sodium citrate and 93 mL of deionized water into a 250 ml round-bottom flask. Under rapid stirring, add 2 mL of silver seeds, and then quickly add 1.0 mL of 0.1 M silver nitrate solution and 1 mL of 0.05 M hydroquinone solution. Let the mixture react for 1 hour, add water to make the volume 100 mL, and obtain 80 nm silver particles, that is, obtain a silver sol SERS substrate.

[0051] C: Granular film metal SERS substrate

[0052] Using a rough glass or ceramic sheet as the substrate, magnetron sputtering is used to sputter metal (sputtering target: gold, silver, copper or gold-silver alloy; sputtering current: 5mA-40mA) on the polystyrene array structure to obtain a granular film metal SERS substrate.

[0053] Example 1

[0054] The structural formula of the capture agent molecule is:

[0055]

[0056] The molar concentration is 10 -4 M, a volume of 50 mL of mercaptopyridine amidoxime molecules (capture agent molecules), with a molar concentration of 10 -3 M of 4-nitrothiophenol (auxiliary enhancement molecule), adding 4-nitrothiophenol solution to the capture agent molecule, and preparing mixed solutions with volume molar ratios of capture agent molecule and 4-nitrothiophenol of 1:0, 1:1, 1:3, 1:5, and 1:10, respectively, and then placing the metal SERS substrate in the mixed solution for 30 minutes, taking it out and drying it, to obtain the metal SERS substrate 1.

[0057] The metal SERS substrate 1 is used to detect nerve agents. After the detection is completed, the metal SERS substrate 1 is subjected to Raman spectrum test to obtain the following Figure 3 Spectrum shown. Figure 3 In the figure, spectral lines I, II, III, IV and V are the spectral lines corresponding to the metal SERS substrate 1 prepared with the volume molar ratio of the capture agent molecules to 4-nitrobenzenethiophenol being 1:0, 1:1, 1:3, 1:5 and 1:10 respectively. It can be seen from the figure that with the increase of the molecular weight of the auxiliary enhancement molecule, the carbon-phosphine bond vibration (VC-P) intensity of the nerve agent gradually increases, indicating that the reactivity of the capture agent molecules and the nerve agent molecules is enhanced, thereby improving the capture efficiency.

[0058] Example 2

[0059] The structural formula of the capture agent molecule is:

[0060]

[0061] The molar concentration is 10 -4 M, the volume of the capture agent is 50mL, and the molar concentration is 10 -3 M of sodium 2,3-dimercaptopropane sulfonate (auxiliary enhancement molecule), adding different volumes of sodium 2,3-dimercaptopropane sulfonate solution to the capture agent molecule, and preparing mixed solutions with volume molar ratios of capture agent molecule and sodium 2,3-dimercaptopropane sulfonate of 1:0, 1:3, 1:5, 1:10, and 1:15, respectively, and then placing the metal SERS substrate in the mixed solution for 30 minutes, taking it out and drying it, to obtain the metal SERS substrate 2.

[0062] The metal SERS substrate 2 is used to detect nerve agents. After the detection is completed, the metal SERS substrate 2 is subjected to Raman spectrum test to obtain the following Figure 4 Spectrum shown. Figure 4In the figure, spectral lines I, II, III, IV and V are the spectral lines corresponding to the metal SERS substrate 2 prepared with the volume molar ratio of the capture agent molecules to 4-nitrobenzenethiophenol being 1:0, 1:3, 1:5, 1:10 and 1:15 respectively. It can be seen from the figure that with the increase of the molecular weight of the auxiliary enhancement molecule, the carbon-phosphine bond vibration (VC-P) intensity of the nerve agent gradually increases, indicating that the reactivity of the capture agent molecules and the nerve agent molecules is enhanced, thereby improving the capture efficiency.

[0063] Example 3

[0064] The molar concentration is 10 -4 M, the volume of the capture agent is 50mL, and the molar concentration is 10 -3 M of 4-(trifluoromethyl)thiophenol, adding different volumes of 4-(trifluoromethyl)thiophenol solution to the capture agent molecule, and preparing mixed solutions with a volume molar ratio of the capture agent molecule to 4-(trifluoromethyl)thiophenol of 1:0, 1:3, 1:5, 1:10, and 1:15, and then placing the metal SERS substrate in the mixed solution for 30 minutes, taking it out and drying it, to obtain the metal SERS substrate 3. The structural formula of the capture agent molecule is:

[0065]

[0066] The metal SERS substrate 3 is used to detect nerve agents. After the detection is completed, the metal SERS substrate 3 is subjected to Raman spectrum test to obtain the following Figure 5 Spectrum shown. Figure 5 In the figure, spectral lines I, II, III, IV and V are the spectral lines corresponding to the metal SERS substrate 3 prepared with the volume molar ratio of the capture agent molecules to 4-(trifluoromethyl)benzenethiol being 1:0, 1:3, 1:5, 1:10 and 1:15 respectively. It can be seen from the figure that with the increase of the molecular weight of the auxiliary enhancement molecule, the carbon-phosphine bond vibration (VC-P) intensity of the nerve agent gradually increases, indicating that the reactivity of the capture agent molecules and the nerve agent molecules is enhanced, thereby improving the capture efficiency.

[0067] 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 bimolecular co-modified metal SERS substrate for nerve agent detection, characterized in that: It includes a capture agent molecule for selectively capturing nerve agent molecules and an auxiliary enhancement molecule for enhancing the capture ability of the capture agent molecule, wherein the capture agent molecule and the auxiliary enhancement molecule are both modified on a metal SERS substrate with Raman activity, the capture agent molecule is composed of a thiol group, an aromatic ring and a strong charge-donating functional group, and the auxiliary enhancement molecule is composed of a thiol group and an electron-withdrawing group; 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 bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: The metal SERS substrate is one of gold, silver and copper.

3. The bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: The aromatic ring is one or a combination of two or more of a ring, a pyridine ring and a pyrrole ring.

4. The bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: 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.

5. The bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: The electron-withdrawing group is one or a combination of two or more of a sulfonic acid group, a cyano group, a nitro group and a trifluoromethyl group.

6. The bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: The molar concentration of the capture agent molecule and the auxiliary enhancement molecule are both 10 -2 mol / L-10 -6 mol / L.

7. The bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 1, characterized in that: The mercapto groups in the capture agent molecules and the auxiliary enhancement molecules are chemically bonded to the surface of the metal SERS substrate to form metal-sulfur bonds.

8. A method for preparing a bimolecular co-modified metal SERS substrate for nerve agent detection according to any one of claims 1 to 7, characterized in that: The specific steps are as follows: S1. Prepare the metal SERS substrate and configure 10 -2 mol / L-10 -6 mol / L molar concentration of capture agent molecules and 0 -2 mol / L-10 -6 mol / L molar concentration of auxiliary enhancing molecules; S2. Add auxiliary enhancement molecules to the capture agent molecules to obtain a mixed solution, and then place the metal SERS substrate in the mixed solution, and then take it out and dry it to obtain a metal SERS substrate.

9. The method for preparing a bimolecular co-modified metal SERS substrate for nerve agent detection according to claim 8, characterized in that: In step S2, the metal SERS substrate is placed in the mixed solution for 10 minutes to 24 hours.

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