A sers substrate for vocs detection and a preparation method thereof

Abstract

The application discloses a SERS substrate for VOC detection and a preparation method thereof, and belongs to the field of SERS detection.The substrate is characterized in that: metal monatomic atoms are loaded on a nanoparticle carrier to form composite nanoparticles, and then a layer of the composite nanoparticles is loaded on a chip with micro-nano structures.The precursor liquid of the metal monatomic atoms is mixed with the nanoparticle carrier or a nanoparticle carrier precursor to react and prepare the composite nanoparticles; the composite nanoparticles are dissolved or dispersed in water to obtain a composite nanoparticle solution; then the substrate with the micro-nano structures is placed on a heating table; and then the composite nanoparticle solution is dropped on the micro-nano structures of the substrate to form a composite nanoparticle layer, thereby preparing the SERS substrate.The SERS substrate can be used for detecting VOCs, especially butyl aldehyde, and can be used in a cancer early screening device; and the detection limit of butyl aldehyde can reach 10 ‑11 M.

Description

Technical Field

[0001] The present invention relates to the fields of early cancer screening, VOCs gas identification, and Raman spectroscopy, and more specifically to a SERS substrate manufacturing method for VOCs detection, which is suitable for large-scale mass production. Background Art

[0002] Since 1985, researchers have been committed to evaluating various diseases by analyzing the content of volatile organic compounds (VOCs) in exhaled breath, and have used it as a biomarker for lung cancer. The main volatile organic compounds in the exhaled breath of healthy people are isoprene (12-580ppb), acetone (1.2-1880ppb), ethanol (13-1000ppb), methanol (160-2000ppb) and other alcohols. In patients with lung cancer, the most common VOCs biomarkers are aldehydes. In theory, SERS technology can achieve single-molecule detection through the SPR phenomenon of precious metal nanostructures. However, due to factors such as poor absorption of VOCs and weak Raman scattering, the application of this technology in gas detection is limited.

[0003] In order to detect molecules with weak Raman intensity and improve the adsorption of VOCs on substrates, researchers have developed many new SERS substrates and detection strategies. For example, by coating metal organic frameworks (MOFs) in the nanostructure of SERS sensors, the adsorption of VOCs can be enhanced. However, it is very difficult to encapsulate noble metals into MOFs, and the shell thickness of MOFs cannot be effectively controlled. In addition, some researchers have explored new methods, such as using dual-mode sensing of fluorescence (FL) and surface-enhanced Raman spectroscopy (SERS) to achieve ultra-sensitive detection of volatile benzaldehyde, but this method is complicated to operate and the detection process is time-consuming. Some researchers have also synthesized dendritic Ag nanocrystals, which have many cavity traps. The reaction time of VOCs on the solid surface is extended through the "cavity vortex" effect, but the detection limit is only 10 -10 In general, existing technologies struggle to achieve both simple operation and superior performance, making on-site detection difficult. We leveraged the fundamental nature of SERS mechanisms, employing single-atom enhanced materials to enhance electron transfer between target molecules. Considering the challenges of monodisperse and stable metal loading, which hinder its application, we devised a rational loading method and solidified the substrate, enabling scalable mass production. Summary of the Invention

[0004] In view of this, the main purpose of the present invention is to provide a method for preparing a heterogeneous catalyst loaded with homogeneous phase points for detecting VOCs.

[0005] To achieve the above objectives, as one aspect of the present invention, the present invention provides a SERS substrate for VOC detection and a preparation method thereof.

[0006] A SERS substrate for VOC detection is characterized in that metal single atoms are loaded on a nanoparticle carrier to form composite nanoparticles, and then a layer of composite nanoparticles is loaded on a chip with a micro-nano structure.

[0007] The metal corresponding to the metal single atom is selected from one or more of tungsten, cerium, platinum, etc.;

[0008] The nanoparticle carrier is selected from one or more of silicon oxide, C material substrate, metal oxide (such as cobalt oxide, etc.), etc.

[0009] The chip is a periodic micro-nano structure matrix composed of a layer of Au nanoparticles loaded on the surface of a silicon substrate, forming a metal surface with a cleanliness level of SCP1 or above; the size of the Au nanoparticles is preferably 80-150nm, and the micro-nano structure is one or more of a linear matrix, a square micro-nano structure matrix, a pentagonal micro-nano structure matrix, and a hexagonal micro-nano structure matrix.

[0010] The above-mentioned method for preparing a SERS substrate for VOC detection is characterized by comprising the following steps:

[0011] (1) Preparation of composite nanoparticles

[0012] The metal salt or / and metal oxide corresponding to the prepared metal single atom is stably combined with an organic molecule having a -CH2CH2OH group in acidic water or / and an organic solvent to obtain a metal single atom precursor, and then the metal single atom precursor liquid is mixed with a nanoparticle carrier or a nanoparticle carrier precursor to react. After the reaction is completed, the mass percentage of the metal single atom in the composite nanoparticles is 10%-20%.

[0013] Among them, when using a nanoparticle carrier precursor, in order to form uniformly dispersed particles, a carbon adsorption material such as graphene oxide can be added as needed after the metal single atom precursor liquid is mixed with the nanoparticle carrier precursor; the reacted material is calcined to remove the adsorption material to finally obtain a composite nanoparticle powder. The specific temperature and time vary according to different materials. The nanoparticle carrier is preferably a metal oxide.

[0014] (2) The composite nanoparticles obtained in step (1) are dissolved or dispersed in water to obtain a composite nanoparticle solution, and then the substrate with the micro-nano structure is placed on a heating table, and then the composite nanoparticle solution is dropped on the micro-nano structure of the substrate to form a composite nanoparticle layer to prepare a SERS substrate.

[0015] Wherein: the metal salt or / and metal oxide is selected from metal oxyacid salt, chloride, such as sodium tungstate, CeCl2, H2PtCl6, etc.;

[0016] The acidic substance is selected from sulfuric acid.

[0017] The organic molecule with -CH2CH2OH group is selected from polyethylene glycol, PEO.

[0018] The SERS substrate obtained by the application is used for detecting VOCs, especially butyraldehyde, and can be used in a cancer early screening device.

[0019] Compared with the prior detection method, the application has the following advantages:

[0020] The application provides a SERS substrate manufacturing method for VOC detection.

[0021] The detection limit of butyraldehyde can reach 10 -11 M, which is 10 times lower than that in other documents, and the relative standard deviation is less than 10%, so the stability is good.

[0022] The application can finally be made into a solid-phase substrate, which is convenient to carry and has a relatively simple SERS detection process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Corresponding to Example 1, it is the precursor solution of single atom W and the picture after UV lamp irradiation, and it is found that obvious color change appears after 1 min of UV lamp irradiation, which indicates that single atom W is successfully synthesized.

[0024] Figure 2 Corresponding to Example 2, it is the HAADF-EDS image of single atom W loaded silica, and it can be found that the particles are uniformly distributed, and single atom W is successfully loaded on the surface of the carrier.

[0025] Figure 3 Corresponding to Example 2, it is the SERS detection result of butyraldehyde and the standard curve using the single atom W loaded silica substrate. -1 The SERS intensity at the characteristic peak and the concentration have a linear relationship; as can be seen from the (a) figure, with the decrease of the concentration of butyraldehyde, the peak intensity of the characteristic peak gradually decreases, and when the concentration of butyraldehyde is as low as 10 -11 M, the characteristic peak can still be obviously observed. As can be seen from the (b) figure, the SERS intensity of butyraldehyde at 1010cm -1The peak intensity of the characteristic peak at is linearly related to the butyraldehyde concentration, R 2 =0.99197.

[0026] Figure 4 : Corresponding to Example 2, different batches of silicon dioxide substrates loaded with single-atom W were used to compare 10 -11 Repeatability experiment of SERS detection of M butyraldehyde. As can be seen from the figure, the peak intensity of the butyraldehyde characteristic peak is not much different in the five batches, and the relative standard deviation of each batch of substrates is less than 10%.

[0027] Figure 5 : Corresponding to Example 3, this is a HAADF-STEM image of carbon nitride loaded with single-atom Ce. It can be seen that single-atom Ce is loaded on the surface of carbon nitride;

[0028] Figure 6 : Corresponding to Example 3, a carbon nitride substrate supporting single-atom Ce is used to 10 -4 SERS detection of M butyraldehyde;

[0029] Figure 7 : Corresponding to Example 4, this is a HAADF-STEM image of cobalt oxide loaded with single-atom Pt, showing that single-atom Pt is loaded on the surface of cobalt oxide;

[0030] Figure 8 : Corresponding to Example 4, a cobalt oxide substrate supporting single-atom Pt is used to 10 -4 SERS detection of M butyraldehyde. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0032] The specific technical solutions of the present invention are:

[0033] A method for preparing a SERS substrate for VOC detection comprises the following steps:

[0034] (1) Preparation of precursor solution:

[0035] (2) Single atom load:

[0036] In step (1), the precursor solution is prepared by adding corresponding metal oxoates and / or metal oxides such as sodium tungstate, strontium chloride, and H2PtCl6·6H2O to water or other organic liquids as needed.

[0037] Mix an organic polymer containing weakly bonded functional groups, such as polyethylene glycol or PEO, with an acid or an organic compound with acid groups and an inorganic acid, such as sulfuric acid. Dissolve and clarify the solution for later use.

[0038] In step (2), the single-atom loading method is as follows: ultrasonically or dissolving and dispersing the carrier material, such as freshly prepared silicon dioxide from tetraethyl orthosilicate, carbon-based materials such as carbon nitride, cobalt oxide, and graphene, in a solvent of similar polarity to the above-mentioned solvent to form a uniform mixture or a clear solution. The metal precursor liquid is mixed with the carrier material, stirred and dispersed for 4 hours or more, washed with the same type of solvent, and vacuum dried or calcined to obtain a bulk material or powder, thereby completing the loading.

[0039] (3) Detection:

[0040] The obtained single-atom loaded material was dissolved and 20 μL was dropped onto the micro-nano processed chip on a 60°C heating table and dried to prepare a SERS substrate. Butyraldehyde solutions of different concentrations were prepared and 20 μL was dropped onto the prepared substrate and dried before SERS detection. The characteristic peaks of the SERS spectrum were assigned, among which 1010 cm -1 is the stretching vibration of CC, 1350cm -1 For the C-H stretching vibration, we convert 1010 cm -1 As the characteristic peak of butyraldehyde.

[0041] The stability of the substrate is a key factor affecting practical applications. The relative standard deviation of each substrate was obtained by testing 5 substrates from different batches. During the test, the concentration of each substrate was randomly recorded at 10 -11 The SERS spectra of 20 points of M butyraldehyde are as follows Figure 4 The signal intensities of butyraldehyde at the same concentration on the substrate were basically consistent, and all RSDs were less than 10%.

[0042] The chip in the following embodiment is a periodic micro-nanostructure matrix composed of a layer of Au nanoparticles loaded on the surface of a silicon substrate, forming a metal surface with a cleanliness level of SCP1 or above; the Au nanoparticles are about 100 nm in size, and the micro-nanostructure is a hexagonal micro-nanostructure matrix with a size of about 10 μm and is densely arranged on the surface.

[0043] Example 1:

[0044] 1. Preparation and judgment of the precursor solution of single-atom W: Add 100 ml of deionized water to the reaction flask, then add 20 g of PEG (molecular weight 2w) and 2 g of sodium tungstate, and stir magnetically until completely dissolved.

[0045] 2. Add 2 mol / L dilute sulfuric acid to pH 1, maintain acidity, and completely dissolve. Let it stand for more than 12 hours without precipitation to obtain the precursor solution.

[0046] Judgment standard: at light intensity 10mW / cm 2After 1 minute of irradiation with UV light, there will be a visible color change from clear to blue.

[0047] Example 2

[0048] Silica loaded with single-atom W:

[0049] 1. Add 50 ml of deionized water and 25 ml of ethanol to the reaction flask to clarify the mixed solvent, disperse 12.5 ml of ethyl orthosilicate in 25 ml of ethanol, and stir magnetically until the two are colorless.

[0050] 2. Add 12.5 ml of the metal precursor liquid in Example 1 to 1 so that the final W loading is 10%, gradually stir and add 8 ml of 20% dilute sulfuric acid. After stirring for 4 hours, the liquid changes from initial turbidity to complete transparency, indicating uniform dispersion of the metal.

[0051] 3. Dry the liquid at 60-80°C to obtain white silicon dioxide containing single-atom W.

[0052] 4. Cut the micro-nano processed chip into regular squares of 5mm×5mm, wash it alternately with water and ethanol three times, and dry it in a vacuum oven at 60℃.

[0053] 5. Take 1 g of the powder in step 3 and dissolve it in 9 mL of ultrapure water. Stir for 10 min. Take out the chip in step 4 and place it on a 60°C heating table. Add 20 μL of the dissolved liquid and bake it dry. Add it three times in sequence to make the SRES substrate.

[0054] 6. Prepare butyraldehyde solutions of different concentrations and drop 20 μL onto the prepared substrate. After drying, perform SERS detection.

[0055] Example 3

[0056] Carbon nitride loaded with single-atom Ce

[0057] 1. Add 10 ml of water, 10 ml of PEG (molecular weight 200) and 0.2 g of CeCl2 to the reaction flask.

[0058] 2. Add 4 ml of 20% dilute sulfuric acid and stir magnetically to clean the liquid until it turns yellow. Centrifuge and filter to leave a clear yellow liquid, which is used as the precursor solution for monatomic Ce.

[0059] 3. Grind 2 g of carbon nitride powder and disperse it in 100 ml of water with ultrasonication. Add 15 ml of precursor liquid dropwise to achieve a final Ce loading of 10%. Stir and disperse at room temperature for 4 h and vacuum dry overnight to obtain a light yellow powder.

[0060] 4. Cut the micro-nano processed chip into regular squares of 5mm×5mm, wash it alternately with water and ethanol three times, and dry it in a vacuum oven at 60℃.

[0061] 5. Take 1 g of the powder in step 3 and dissolve it in 9 mL of ultrapure water. Stir for 10 min. Take out the chip in step 4 and place it on a 60°C heating table. Add 20 μL of the dissolved liquid and bake it dry. Add it three times in sequence to make the SRES substrate.

[0062] A butyraldehyde solution was prepared and 20 μL was dropped onto the prepared substrate. After drying, SERS detection was performed.

[0063] Example 4

[0064] Cobalt oxide loaded with single-atom Pt

[0065] 1. Prepare 25 mL of 1% H2PtCl6·6H2O solution (the solvent is water and methanol, with a volume ratio of 1:1).

[0066] 2. Take 5g of CoCl2 powder, put it into 1, mix, add 0.5g of graphene oxide and mix well, centrifuge, wash, and hydroheat at 180 degrees for 24h;

[0067] 3. Take 1 g of the above powder and dissolve it in 5 ml of ethanol and place it in a crucible. Rapidly burn it in a muffle furnace at 600 degrees for 2 minutes. After taking it out, quickly place it in cold water, centrifuge it, and wash it to obtain CoO loaded with single-atom pt.

[0068] 4. Cut the micro-nano processed chip into regular squares of 5mm×5mm, wash it alternately with water and ethanol three times, and dry it in a vacuum oven at 60℃.

[0069] 5. Take 1 g of the powder in step 3 and dissolve it in 9 mL of ultrapure water. Stir for 10 min. Take out the chip in step 4 and place it on a 60°C heating table. Add 20 μL of the dissolved liquid and bake it dry. Add it three times in sequence to make the SRES substrate.

[0070] A butyraldehyde solution was prepared and 20 μL was dropped onto the prepared substrate. After drying, SERS detection was performed.

Claims

1. A method for preparing a SERS substrate for VOCs detection, characterized in that: The following steps are involved: (1) Preparation of composite nanoparticles Stably combining a metal salt or / and a metal oxide corresponding to a metal single atom with an organic molecule having a -CH2CH2OH group in acidic water or / and an organic solvent to obtain a metal single atom precursor, and then mixing the metal single atom precursor liquid with a nanoparticle carrier or a nanoparticle carrier precursor to react to obtain composite nanoparticles; When a nanoparticle carrier precursor is used, in order to form uniformly dispersed particles, a carbon adsorption material is added as needed after the metal single atom precursor liquid and the nanoparticle carrier precursor are mixed; the reacted material is calcined to remove the adsorption material and finally a composite nanoparticle powder is obtained. The specific temperature and time vary depending on the material. (2) dissolving or dispersing the composite nanoparticles obtained in step (1) in water to obtain a composite nanoparticle solution, then placing a substrate having a micro-nano structure on a heating table, and then dropping the composite nanoparticle solution on the micro-nano structure of the substrate to form a composite nanoparticle layer to prepare a SERS substrate; the micro-nano structure of the substrate is a periodic micro-nano structure matrix composed of a layer of Au nanoparticles loaded on the surface of a silicon substrate to form a metal surface with a cleanliness level of SCP1 or above; the size of the Au nanoparticles is 80-150nm, and the micro-nano structure is one or more of a line matrix, a square micro-nano structure matrix, a pentagonal micro-nano structure matrix, and a hexagonal micro-nano structure matrix; The metal corresponding to the metal single atom is selected from one or more of tungsten, cerium, and platinum; The nanoparticle carrier is selected from one or more of silicon oxide, C material substrate and metal oxide.

2. The method according to claim 1, characterized in that The metal salt and / or metal oxide is selected from metal oxo salts and chlorides; The acidic substance is selected from sulfuric acid; The organic molecule having a -CH2CH2OH group is selected from: polyethylene glycol, PEO.

3. The method according to claim 2, characterized in that The metal salt and / or metal oxide is selected from sodium tungstate, CeCl2, and H2PtCl6.

4. The method according to claim 1, characterized in that The mass percentage of metal single atoms in the composite nanoparticles is 10%-20%.

5. A SERS substrate prepared according to the method of any one of claims 1 to 4.

6. Use of the SERS substrate prepared according to the method according to any one of claims 1 to 4 for detecting VOCs.

7. The use according to claim 6, for butyraldehyde detection.

8. Use of the SERS substrate prepared according to the method according to any one of claims 1 to 4 in early cancer screening equipment.

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