SERS substrate for VOCs detection and preparation method

Abstract

The invention discloses an SERS substrate for VOC detection and a preparation method, and belongs to the field of SERS detection. According to the substrate, metal single atoms are loaded on a nano-particle carrier to form composite nano-particles, and then a layer of composite nano-particles are loaded on a chip with a micro-nano structure. Mixing the precursor liquid of the metal monatomic with the nano-particle carrier or the nano-particle carrier precursor for reaction to prepare composite nano-particles; the preparation method comprises the following steps: dissolving or dispersing composite nanoparticles in water to obtain a composite nanoparticle solution, then placing a substrate with a micro-nano structure on a heating table, and then dripping the composite nanoparticle solution on the micro-nano structure of the substrate to form a composite nanoparticle layer, thereby preparing the SERS substrate. The fluorescent probe is used for detecting VOCs, especially butyraldehyde, and can be used in cancer early screening equipment, and the detection limit of butyraldehyde 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, the adsorption of VOCs is enhanced by coating metal organic frameworks (MOFs) in the nanostructure of the SERS sensor. However, it is very difficult to encapsulate precious 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 M. In general, it is difficult for existing technologies to achieve both simple operation and superior performance, and it is difficult to conduct on-site detection. Starting from the essence of the SERS mechanism, we use single-atom enhanced materials and electron transfer between target molecules, and considering that the monodispersity and stable loading of metals are the difficulties that restrict its application, we designed a reasonable loading method and solidified the substrate to enable large-scale 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] In order to achieve the above objective, 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.) and the like.

[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 to form 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, a hexagonal micro-nano structure matrix, etc.

[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 nanoparticle is 10%-20%.

[0013] Among them, when using a nanoparticle carrier precursor, in order to form evenly 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 the material, and the nanoparticle carrier is preferably a metal oxide.

[0014] (2) dissolving or dispersing the composite nanoparticles obtained in step (1) in water to obtain a composite nanoparticle solution, then placing a substrate with a micro-nano structure on a heating platform, 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.

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

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

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

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

[0019] Compared with the existing detection methods, the advantages of the present invention are:

[0020] The present invention provides a method for preparing a SERS substrate for VOC detection, which is to react metal single atoms with carrier materials to generate composite nanoparticles. Due to the presence of single atoms, the electron transfer between target molecules and the material surface can be enhanced. At the same time, the composite nanomaterial can adsorb VOC well, thereby enhancing the SERS performance. The regular substrate also improves the stability of the SERS performance.

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

[0022] The present invention can be finally made into a solid phase substrate, which is easy to carry and the SERS detection process is relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Corresponding to Example 1, it is a picture of the precursor solution of single-atom W and its UV light irradiation. It is found that after 1 minute of UV light irradiation, an obvious color change occurs, indicating that single-atom W is successfully synthesized;

[0024] Figure 2 : Corresponding to Example 2, it is a HAADF-EDS image of silicon dioxide loaded with single-atom W. It can be found that the particles are evenly distributed and the single-atom W is successfully loaded onto the carrier surface;

[0025] Figure 3 :Corresponding to Example 2, the SERS detection results and standard curve of butyraldehyde using a silicon dioxide substrate loaded with single-atom W; (a) SERS spectrum of butyraldehyde, (b) 1010cm -1 The linear relationship between the SERS intensity at the characteristic peak and the concentration; as shown in Figure (a), as the butyraldehyde concentration decreases, the peak intensity of the characteristic peak gradually decreases, as low as 10 -11 M, the characteristic peaks can still be clearly observed. As can be seen from Figure (b), butyraldehyde 1010cm -1The peak intensity of the characteristic peak at is linearly related to the butyraldehyde concentration. 2 =0.99197.

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

[0027] Figure 5 : Corresponding to Example 3, it is a HAADF-STEM image of carbon nitride loaded with single-atom Ce, and 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 carrying a single atom of Ce is used to 10 -4 SERS detection of M butyraldehyde;

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

[0030] Figure 8 : Corresponding to Example 4, a cobalt oxide substrate supporting a single atom of 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 scheme of the present invention is:

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

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

[0038] In the step (2), the single atom loading method is: in a solvent with similar polarity to the above, ultrasonically or dissolve and disperse the carrier material: such as silicon dioxide newly prepared from tetraethyl orthosilicate, carbon nitride and other C-based materials, cobalt oxide, graphene, and then 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, vacuum dried or calcined to obtain a bulk / powdered bulk material, and the loading is completed.

[0039] (3) Detection:

[0040] The obtained single-atom loaded material was dissolved, and 20 μL was dropped on the micro-nano processed chip on a 60°C heating table, and dried to make a SERS substrate. Different concentrations of butyraldehyde solution were prepared, and 20 μL was dropped on the prepared substrate, and SERS detection was performed after drying. The characteristic peaks of the SERS spectrum were assigned, among which 1010 cm -1 is the stretching vibration of CC, 1350cm -1 For the CH 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-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 about 100nm, and the micro-nano structure is a hexagonal micro-nano structure matrix with a size of about 10μm and is closely arranged on the surface.

[0043] Embodiment 1:

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

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

[0046] Judgment standard: at light intensity 10mW / cm 2After being irradiated with UV light for 1 minute, 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 clarify the mixed solvent in the reaction flask, disperse 12.5 ml of ethyl orthosilicate in 25 ml of ethanol, and stir the two magnetically until they 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 monatomic W.

[0052] 4. Cut the micro-nano processed chip into regular squares of 5 mm × 5 mm, wash it alternately with water and ethanol for 3 times, and dry it in a vacuum oven at 60 °C.

[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 a SRES substrate.

[0054] 6. Prepare butyraldehyde solutions of different concentrations and drop 20 μL on 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 into the reaction flask.

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

[0059] 3. Grind 2 g of carbon nitride powder and disperse it in 100 ml of water with ultrasound, drop 15 ml of precursor liquid to make the final Ce loading amount 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 5 mm × 5 mm, wash it alternately with water and ethanol for 3 times, and dry it in a vacuum oven at 60 °C.

[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 a SRES substrate.

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

[0063] Example 4

[0064] Cobalt oxide loaded with single Pt atoms

[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 CoCl2 powder, put it into 1, mix, add 0.5g graphene oxide and mix evenly, centrifuge, wash, and heat 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 5 mm × 5 mm, wash it alternately with water and ethanol for 3 times, and dry it in a vacuum oven at 60 °C.

[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 a SRES substrate.

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

Claims

1. A SERS substrate for VOC detection, 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.

2. A SERS substrate for VOC detection according to claim 1, characterized in that: The metal corresponding to the metal single atom is selected from one or more of tungsten, cerium, platinum, etc.; The nanoparticle carrier is selected from one or more of silicon oxide, C material substrate, metal oxide (such as cobalt oxide, etc.) and the like.

3. A SERS substrate for VOC detection according to claim 1, characterized in that: The chip 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 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, a hexagonal micro-nano structure matrix, etc.

4. A SERS substrate for VOC detection according to claim 1, characterized in that: The mass percentage of metal single atoms in the composite nanoparticles is between 10% and 20%.

5. The method for preparing a SERS substrate for VOC detection according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Preparation of composite nanoparticles Stably combining the metal salt or / and metal oxide corresponding to the prepared 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; Wherein, when a nanoparticle carrier precursor is used, in order to form dispersed and uniform 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, and the specific temperature and time vary according to different materials, and the nanoparticle carrier is preferably a metal oxide; (2) dissolving or dispersing the composite nanoparticles obtained in step (1) in water to obtain a composite nanoparticle solution, then placing a substrate with a micro-nano structure on a heating platform, 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.

6. The method according to claim 5, characterized in that The metal salt and / or metal oxide is selected from metal oxoacid salts and chlorides, such as sodium tungstate, CeCl2, H2PtCl6, etc.; The acidic substance is selected from sulfuric acid; The organic molecule having a -CH2CH2OH group is selected from: polyethylene glycol, PEO.

7. Use of a SERS substrate for VOC detection as claimed in any one of claims 1 to 4, for detecting VOCs, especially for butyraldehyde.

8. Use of a SERS substrate for VOC detection as described in any one of claims 1 to 4 in an early cancer screening device.

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