Method for SERS (Surface Enhanced Raman Scattering) detection of particulate matters in solution by using surfactant modified nanoparticles

Abstract

The invention provides a method for SERS (Surface Enhanced Raman Scattering) detection of particulate matters in a solution by using surfactant modified nanoparticles. The method comprises the following steps: providing an enhanced nanoparticle material; providing a surfactant, and coating the reinforced nanoparticle material with the surfactant to obtain a surfactant modified nanoparticle material; wherein the substance of the surfactant is determined according to the positive and negative of the surface charge of the detected particulate matter and background noise interference; providing a to-be-detected particulate matter solution sample, and uniformly mixing the to-be-detected particulate matter solution sample with the surfactant modified nanoparticle material to obtain a mixed solution; and performing Raman detection on the mixed solution. According to the invention, the effect of amplifying the signal of the detected particulate matter can be achieved, so that the purpose of online detection of the detected particulate matter (such as micro-nano plastic) in an aqueous solution is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of spectral analysis, and in particular to a method for using surfactant-modified nanoparticles for SERS detection of particles in a solution. Background Art

[0002] In the past few decades, microplastic pollution has attracted widespread attention from scientists, just like the serious problem of marine particle pollution. More and more studies have pointed out that the harm caused by decomposed plastics may even be greater than that of regular-sized plastics. Microplastics (MPs) and nanoplastics (NPs) are more likely to enter the human body through marine products, drinking water, and even atmospheric circulation than ordinary plastics. Whether it is the toxicity of the plastic itself or substances such as surfactants, stabilizers, and additives, they will accumulate in the organs and cause irreversible damage. In order to deeply and scientifically investigate the pollution problem of micro-nano plastics, it is urgent to conduct on-site detection of micro-nano plastics in water samples, and then understand the actual distribution, types, and transmission of plastic particles, obtain plastic pollution information in real time, and lay the foundation for subsequent governance.

[0003] Among the many optical detection methods currently available, Fourier transform infrared spectroscopy (FTIR) and surface enhanced Raman spectroscopy (SERS) are the two most commonly used non-destructive detection methods for spectral analysis of microplastics. However, the current FTIR and SERS detection of micro-nanoplastic particles requires pretreatment. For FTIR detection, membrane filtration is the first step in analyzing and identifying microplastics. As for SERS detection, although SERS has the ability to detect in aqueous solution, the current detection strategy requires drying samples on a precious metal substrate or enriching samples on a precious metal filter membrane. Such pretreatment requirements limit the in-situ detection capabilities of micro-nanoplastic particles. In order to improve the real-time detection capabilities of micro-nanoplastic particles, it is necessary to find a method to directly detect micro-nanoplastics in aqueous solution.

[0004] For commonly used Raman enhanced particles, the design and selection of materials have always been a research hotspot in the field of SERS detection. The preparation of enhanced particles with high synthetic stability and stable morphology has always been a very important part of SERS detection. However, since particles move randomly in aqueous solution, even if enhanced particles are added to the solution to amplify the signal intensity, it is still a challenge to detect particles in aqueous solution. Therefore, the detection specimen needs to establish an intermolecular interaction relationship with the enhanced particles to improve the signal intensity in order to achieve acceptable SERS performance. According to our previous patent (publication number: CN117740629A), the heterogeneous charge adsorption conditions between the oppositely charged enhanced particles and the measured particles have better SERS performance than the conditions of the same charge. However, the surface charge of the particles in the environment has strong uncertainty. In order to enhance the SERS detection signal and detect all the particles in the environment, it is necessary to synthesize and prepare enhanced particles with positive and negative charges at the same time to maximize the SERS detection performance. Based on the basic concept of redox reaction, the negatively charged enhanced particles only need one step of reduction to achieve the synthesis of particles, and such surface charged particles are often used in SERS detection. At present, positively charged enhanced particles are often used for small molecule biomarker detection, such as the content provided in patent US20070155021A1, Modification of metal nanoparticles for improved analyte detection by surface enhanced Raman spectroscopy (SERS), which establishes a relationship with the analyte through the binding of biological functional groups. However, for micron-sized particle analytes, their highly stable structure makes it much more difficult for biological modified functional groups to bind than small biological molecules, and it is impossible to establish a relationship between particles through chemical connection. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a method for using surfactant-modified nanoparticles for SERS detection of particles in solution.

[0006] In order to realize the online Raman detection of micro-nano plastics, the measured particles are uniformly dispersed in the aqueous solution and maintain irregular motion. Therefore, it is necessary to build a strong intermolecular interaction relationship to achieve stable detection of the measured particles. At the same time, since it is necessary to maintain a strong relationship between the measured particles and the enhanced particles, a surfactant is introduced to modify the surface charge of the enhanced particles, so that the measured particles and the enhanced particles form a heterogeneous charge attraction relationship, thereby forming a strong hot spot effect between the particles. This operation will lead to problems such as large background noise interference and weak inter-particle correlation. Therefore, it is necessary to screen surfactants based on the charge characteristics and Raman signals of the measured particles, so as to realize the online detection of particles in the environment based on charge-regulated SERS.

[0007] The present invention provides a method for using surfactant-modified nanoparticles for SERS detection of particles in a solution, comprising:

[0008] providing enhanced nanoparticle materials;

[0009] Providing a surfactant, and using the surfactant to coat the enhanced nanoparticle material to obtain a surfactant-modified nanoparticle material; wherein the substance of the surfactant is determined according to the positive or negative surface charge of the measured particle itself and the background noise interference;

[0010] Providing a sample of a particle solution to be measured, and uniformly mixing the sample of the particle solution to be measured with the surfactant-modified nanoparticle material to obtain a mixed solution;

[0011] The mixed solution is subjected to Raman detection.

[0012] Optionally, the enhanced nanoparticle material is provided, wherein: the enhanced nanoparticle material is a metal nanoparticle material, and the average particle size of the enhanced nanoparticle material is 20nm to 500nm.

[0013] Optionally, the reinforcing nanoparticle material is a nanomaterial that can be loaded in a mesoporous material or a metal organic framework structure.

[0014] Optionally, a surfactant is provided, wherein: the surfactant enhances the interaction with the measured particles through charge adsorption, thereby enhancing the detection signal.

[0015] Optionally, the surfactant is any one of sodium citrate, ascorbic acid, cetyltrimethylammonium bromide and polyethyleneimine.

[0016] Optionally, providing a sample of a solution of particles to be measured includes:

[0017] Evenly disperse the particles to be tested or the aqueous solution of the particles to be tested in the aqueous solution system;

[0018] Ultrasonic dispersion is performed in a constant temperature water environment at room temperature to obtain a sample of a solution of the particles to be measured, wherein the final concentration of the sample of the solution of the particles to be measured is not less than 0.01 wt.%.

[0019] Optionally, the average particle size of the measured particles is 1 nm to 100 μm.

[0020] Optionally, before uniformly mixing the particle solution sample to be tested with the surfactant-modified nanoparticle material, the method includes: concentrating the surfactant-modified nanoparticle material to obtain a concentrated surfactant-modified nanoparticle material solution.

[0021] Optionally, uniformly mixing the measured particle solution sample with the surfactant-modified nanoparticle material comprises: ultrasonically mixing the measured particle solution sample with the concentrated surfactant-modified nanoparticle material solution at a concentration ratio of 2:1 to 20:1.

[0022] Optionally, the ultrasonic mixing time is not less than 10 min.

[0023] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0024] The method provided by the present invention enhances the Raman characteristic peaks of the measured particles by uniformly mixing the surfactant-modified nanoparticle material with the measured particles. At the same time, the surfactant can reduce the interference of the background noise of the enhanced nanoparticle material itself and prevent the interference peak from covering the detection characteristic peak. Thus, the effect of amplifying the signal of the measured particles is achieved, and the purpose of online detection of the measured particles (such as micro-nano plastics, etc.) is achieved in the aqueous solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0026] Figure 1 It is a schematic diagram of a process of performing Raman enhanced detection on a mixed solution in one embodiment of the present invention;

[0027] Figure 2 The schematic diagram of the synthesis process of the surfactant-modified nanoparticle material in one embodiment of the present invention, wherein: A is a positively charged gold nanoparticle, and B is a negatively charged gold nanoparticle;

[0028] Figure 3 The Raman shift curves under different concentrations of the measured particles under the same experimental conditions in Example 1 of the present invention;

[0029] Figure 4The Raman signal intensity under different concentrations of the measured particles under the same experimental conditions in Example 1 of the present invention;

[0030] Figure 5 The electron microscope characterization result of the gold nanoparticles in Example 1 of the present invention;

[0031] Figure 6 The Raman shift curves under different concentrations of the measured particles under the same experimental conditions in Example 2 of the present invention;

[0032] Figure 7 The Raman signal intensity under different concentrations of the measured particles under the same experimental conditions in Example 2 of the present invention;

[0033] Figure 8 The electron microscopy characterization results of the surfactant-modified gold nanoparticles in Example 2 of the present invention;

[0034] Fig. 9 Comparison of Raman intensities of different gold nanoparticles detecting the same particle in one embodiment of the present invention Figure 1 ;

[0035] Fig.10 Comparison of Raman intensities of different gold nanoparticles detecting the same particle in one embodiment of the present invention Figure 2 ;

[0036] Fig.11 This is a comparison chart of the effects of different surfactants on Raman intensity in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0038] Figure 1 A schematic diagram of a method for SERS detection of particles in a solution using surfactant-modified nanoparticles in one embodiment of the present invention is shown. The method for SERS detection of particles in a solution using surfactant-modified nanoparticles provided in one embodiment of the present invention aims to enhance Raman characteristic peaks and reduce background noise interference, and can achieve regulation of the molecular relationship between the particles to be detected (such as micro-nano plastics, etc.) and the SERS-enhanced nanoparticles in the solution, and improve the ability to detect its Raman signal. The method comprises the following steps:

[0039] S1. providing enhanced nanoparticle materials;

[0040] S2, providing a surfactant, and using the surfactant to coat and enhance the nanoparticle material to obtain a surfactant-modified nanoparticle material; wherein the substance of the surfactant is determined according to the positive and negative surface charge of the measured particles themselves and the background noise interference;

[0041] S3, providing a sample of a particle solution to be measured, and uniformly mixing the sample of the particle solution to be measured with a surfactant-modified nanoparticle material to obtain a mixed solution;

[0042] S4. Perform Raman detection on the mixed solution.

[0043] In order to prepare SERS enhanced nanoparticle materials for subsequent surface enhanced Raman testing, a variety of enhanced nanoparticle materials are provided to improve the Raman detection capability of the object being tested. In some embodiments, the enhanced nanoparticle material is prepared by any one of a hydrothermal synthesis method, a vapor deposition method, a sol-gel method, and a redox method, and the enhanced nanoparticle material is a metal nanoparticle material. The enhanced nanoparticle material is usually a nanomaterial with an inert metal as the core, and can be modified and adjusted according to needs later.

[0044] In some other embodiments, in order to synthesize enhanced particles with different charge requirements, any one of hydrothermal / solvothermal synthesis, ultrasonic method, microwave heating method and electrochemical synthesis method is used to prepare enhanced nanoparticle material, which can be used directly, and the enhanced nanoparticle material is also a nanomaterial that can be loaded in a mesoporous material or a metal organic framework structure (MOF). The metal organic framework structure is a crystalline framework material with intramolecular pores formed by self-assembly of metal ions and organic ligands through coordination bonds under certain conditions. The positive and negative charges of the enhanced nanoparticle material and the metal framework structure nanomaterial need to be determined according to the charge on the surface of the measured particle, and the charge sign needs to be opposite to the charge of the measured particle. It should be noted that similar load structures can be used for this detection scheme, such as covalent organic framework structure (COF) materials, etc.

[0045] It should also be noted that, in some other embodiments, the SERS enhanced nanoparticles may also be obtained by other preparation methods, and are not limited thereto.

[0046] The morphology of the enhanced nanoparticle material can be a variety of structures. In some embodiments, the average particle size of the enhanced nanoparticle material is 20nm to 500nm, which is specifically set according to the particle size of the measured particles. The measured particles are limited to within 1um. If the particles are larger than 1um, the enhancement effect of the enhanced nanoparticle material is reduced. The determination method of the measured particles is DLS detection, which is achieved by measuring and counting the average particle size of the measured particles.

[0047] In the above embodiment of the present invention, in order to determine the surfactant required for the enhanced particles, thereby maximizing the enhancement of the characteristic signal of the measured particles, according to different detection characteristics of the measured particles, including charge detection and detection of characteristic signals of the measured particles, a surfactant for the characteristic signal of the measured particles is provided, and the surface of the enhanced nanoparticle material is modified by selecting a corresponding surfactant, and the surfactant enhances the interaction relationship with the measured particles through charge adsorption to enhance the detection signal, such as using any one of sodium citrate, ascorbic acid (AA), pentaethylenehexamine (PEHA), hexadecyltrimethylammonium bromide (CTAB) and polyethyleneimine (PEI) as a surfactant, adjusting the surface charge of the measured particles according to the needs, modifying the surface of the enhanced nanoparticle material, enhancing the signal of the measured particles, and reducing the interference of the background noise on the characteristic signal of the measured particles. In some other embodiments, if the detected particles are replaced, the corresponding surfactant needs to be reselected according to its charge and signal characteristics to achieve the best enhancement effect.

[0048] It should be noted that negatively charged enhanced particles do not need to be modified with surfactants if there is no additional modification or material requirement. Figure 2 As shown in Figure B, small nanometer negatively charged enhanced particles are prepared by using a negatively charged reducing agent to reduce the particles. To prepare surfactant-modified nanoparticles, such as Figure 2 As shown in A, during the growth of the seeds (gold nanoparticles), a surfactant is added. The surfactant will modify the enhanced particles as the gold nanoparticles grow, thereby preparing positively charged SERS enhanced nanoparticles.

[0049] In the above embodiments of the present invention, the screening and design of surfactants take into account the interference of background noise between the measured particles and the surfactants, and the surfactants are used to enhance the customized charge attachment of the particles. Through the screening and adjustment design of surfactants, it is possible to coat surfactants with different charges or modify groups with different charges, so as to form a heterogeneous charge adsorption relationship with the measured particles, thereby enhancing the particle signal.

[0050] In some embodiments, providing a solution sample of the particles to be tested includes: uniformly dispersing the particles to be tested or the aqueous solution of the particles to be tested in an aqueous solution system, preferably, the aqueous solution system is a purified ultrapure water system; performing ultrasonic dispersion in a constant temperature water environment at room temperature to obtain a solution sample of the particles to be tested, and considering factors such as the minimum detection limit, the final concentration of the solution sample of the particles to be tested is not less than 0.01wt.% to ensure the accuracy of the test results.

[0051] In some embodiments, the particle morphology of the measured particles can be a variety of structures, such as circular, elliptical, rectangular, polygonal and irregular morphologies, etc. Considering the influence of the laser spot size, the average particle size of the measured particles to be enhanced is 1nm to 100μm.

[0052] In some embodiments, before uniformly mixing the measured particle solution sample with the surfactant-modified nanoparticle material, the process includes: concentrating the surfactant-modified nanoparticle material in solution to obtain a concentrated surfactant-modified nanoparticle material solution, thereby regulating and enhancing the intermolecular relationship between the nanoparticle material and the measured particle, and enhancing the signal strength of the measured particle solution sample.

[0053] In some embodiments, the particle solution sample to be tested and the surfactant-modified nanoparticle material are uniformly mixed, including: ultrasonically mixing the particle solution sample to be tested and the concentrated surfactant-modified nanoparticle material solution at a concentration ratio of 2:1 to 20:1. Furthermore, the ultrasonic mixing time is not less than 10 minutes. Thus, sufficient and uniform mixing is achieved.

[0054] In some embodiments, the mixed solution is subjected to Raman detection using a Raman detector, and further reference is made to Figure 1 , exemplary, the Raman detector includes the following equipment: a laser transmitter, whose laser wavelength is 785nm and whose detection range is 500cm -1 ~2000cm -1 ; Raman fiber optic detection probe, used to detect the Raman signal of the object being measured, the probe position needs to be focused below the liquid surface of the sample pool; real-time reading software, instantly read the Raman signal of the object being measured and its detection intensity, and perform baseline subtraction and data processing, export and other functions; the placement rack can fix the sample pool and determine the focus position of the probe. Use laser excitation and use Raman spectrometer for data collection and analysis to achieve the detection of the measured particles.

[0055] The above embodiment of the present invention selects corresponding surfactants for different particles to be tested, enhances the Raman characteristic peaks of the particles to be tested, avoids interference signals, and realizes real-time on-site Raman detection of particles in aqueous solution. The above embodiment of the present invention does not need to dry the particles to be tested or enhance the aggregation of metal nano-microspheres. After uniformly mixing them with surfactant-modified nano-particle materials, high-resolution, high-sensitivity, and high-specificity micro / nano-particle detection can be performed. The method is simple and highly feasible.

[0056] The above-mentioned embodiment of the present invention utilizes enhanced particles with all possible charges including positive and negative surface charges to achieve the best enhancement. Compared with the enhanced particle design of CN117740629A, the above-mentioned embodiment of the present invention aims to use surfactants to perform customized modification on the charge of enhanced particles, and then utilize the charge adsorption effect to enhance the signal of the measured particles. Compared with US20070155021A1, the above-mentioned embodiment of the present invention focuses on the Raman detection of micro-nano particles rather than the detection of biological molecule signals. Compared with small biological molecules, the detection mechanism of large particles focuses more on the relationship between the measured particles and the enhanced particles.

[0057] The scheme of the present application will be explained below in conjunction with specific embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the documents in this area or the product specifications are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained through commercial channels.

[0058] Example 1

[0059] This embodiment provides a real-time detection method for nanoscale polystyrene microspheres in an aqueous solution, as follows:

[0060] S1. The particles to be tested are micro / nano plastic polystyrene microspheres with a size of 30nm. The surfaces of the two polystyrene particles carry negatively charged carboxyl groups and positively charged amino groups respectively. The initial concentration of the polystyrene microsphere solution is 5wt.%, and the solvent is ultrapure water. This concentration will be set as the initial concentration for subsequent tests.

[0061] At room temperature, a polystyrene microsphere solution of initial concentration was diluted to 1 wt.% using ultrapure water as the solvent.

[0062] S2. Prepare SERS enhanced nanoparticles by hydrothermal synthesis. Gold nanoparticles are prepared and modified by reducing agent sodium citrate. The core reaction is the redox reaction of tetrachloroauric acid and sodium citrate. The specific process is: add 50mL of 0.04wt.% tetrachloroauric acid solution to a three-necked flask in an oil bath heating environment, and keep the solution under continuous and uniform magnetic stirring. After the solution boils, quickly add 1wt.% 500μL of sodium citrate solution and continue to maintain magnetic uniform stirring for 1h. Within 5min after the reducing agent is added, the solution turns dark purple. After preparation, pipette into a centrifuge tube and cool the gold nanoparticle solution to room temperature. Keep this solution away from light and in a refrigerator at 4 degrees.

[0063] The prepared gold nanosphere solution needs to be concentrated by centrifugation. The gold nanosphere solution of the initial concentration is centrifuged, the upper clear liquid is removed, the bottom gold colloid is retained, and ultrapure water is added again to concentrate it 5 times.

[0064] S3. The concentrated metal nanomaterials were ultrasonically mixed with the polystyrene microsphere solution at a ratio of 10:1, and the ultrasonication lasted for 10 minutes. After mixing, 400 μL was transferred to a quartz cuvette and placed in the fixed frame of the Raman detector.

[0065] S4. Use a 785nm laser with a laser power of 300mW, an integration time of 20s, and an integration number of 1 to perform Raman detection on the mixed solution. After the detection is completed, the characteristic peaks and Raman intensities of the polystyrene microspheres under test can be read through the software.

[0066] Example 2

[0067] The difference between this embodiment and embodiment 1 is that the choice of gold nanosphere surfactant is different.

[0068] Prepare SERS enhanced nanoparticle solution by gold seed growth method. First, mix 600μL of 0.1M ascorbic acid, 80μL of 1M sodium hydroxide and 50mL ultrapure water at 1200rpm. Then quickly add 1wt.% 1mL of tetrachloroauric acid to the above solution system. After the gold seed synthesis is completed, 0.2wt.% 200μL of pentaethylenehexamine, 0.1M 1mL of hydroxylamine hydrochloride and 3mL of gold seed solution are mixed evenly with magnetic stirring. Then 0.05wt.% 20mL of tetrachloroauric acid is added to the above mixed solution at a uniform rate. After preparation, transfer the solution to a centrifuge tube and store it in a refrigerator at 4 degrees.

[0069] The remaining steps are the same as those in Example 1.

[0070] The different SERS enhanced nanoparticles in the above examples were used to detect the particles under test. The results are as follows: Figure 3 to Figure 8 According to the results, by mixing different gold nanoparticles with polystyrene microspheres, the characteristic peak signal of polystyrene can be clearly enhanced, and the minimum detection limit is 0.05wt.%, which can realize the real-time on-site detection of polystyrene microspheres in aqueous solution.

[0071] At the same time, if Figures 9-10 As shown, AuNP(-) and AuNP(+) refer to the nanoparticles prepared in Examples 1 and 2, respectively, and PS NPs are the particles to be tested. Different enhanced particles detect polystyrene microspheres of the same concentration, and their enhanced performances are significantly different. The different surface charges will directly affect the enhancement effect of gold nanoparticles on polystyrene Raman signals.

[0072] Reference Fig.11 By comparing the Raman signal intensities of polystyrene microspheres with the same concentration detected by SERS-enhanced nanoparticles modified with three different surfactants, it is proved that the surfactant has a direct effect on the signal of the object being measured: the choice of surfactant will directly affect the existence and intensity of the characteristic peak signal of the measured particles.

[0073] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A method for using surfactant-modified nanoparticles for SERS detection of particles in solution, characterized in that: include: providing enhanced nanoparticle materials; Providing a surfactant, and using the surfactant to coat the enhanced nanoparticle material to obtain a surfactant-modified nanoparticle material; wherein the substance of the surfactant is determined according to the positive and negative surface charges of the particles to be measured and the background noise interference; Providing a sample of a particle solution to be measured, and uniformly mixing the sample of the particle solution to be measured with the surfactant-modified nanoparticle material to obtain a mixed solution; The mixed solution is subjected to Raman detection.

2. The method according to claim 1, characterized in that The enhanced nanoparticle material is provided, wherein: the enhanced nanoparticle material is a metal nanoparticle material, and the average particle size of the enhanced nanoparticle material is 20nm to 500nm.

3. The method according to claim 1, characterized in that The enhanced nanoparticle material is a nanomaterial that can be loaded in a mesoporous material or a metal organic framework structure.

4. The method according to claim 1, characterized in that The surfactant is provided, wherein: the surfactant enhances the interaction relationship with the measured particles through charge adsorption, thereby enhancing the detection signal.

5. The method according to claim 4, characterized in that The surfactant is any one of sodium citrate, ascorbic acid, cetyltrimethylammonium bromide and polyethyleneimine.

6. The method according to claim 1, characterized in that The method of providing a sample of a particle solution to be tested comprises: Evenly disperse the particles to be tested or the aqueous solution of the particles to be tested in the aqueous solution system; Ultrasonic dispersion is performed in a constant temperature water environment at room temperature to obtain a sample of a solution of the particles to be measured, wherein the final concentration of the sample of the solution of the particles to be measured is not less than 0.01 wt.%.

7. The method according to claim 6, characterized in that The average particle size of the measured particles is 1 nm to 100 μm.

8. The method according to claim 1, characterized in that Before uniformly mixing the particle solution sample to be tested with the surfactant-modified nanoparticle material, the method includes: concentrating the surfactant-modified nanoparticle material to obtain a concentrated surfactant-modified nanoparticle material solution.

9. The method according to claim 8, characterized in that The particle solution sample to be tested is uniformly mixed with the surfactant-modified nanoparticle material, including: ultrasonically mixing the particle solution sample to be tested and the concentrated surfactant-modified nanoparticle material solution at a concentration ratio of 2:1 to 20:

1.

10. The method according to claim 9, characterized in that The ultrasonic mixing time is not less than 10 minutes.

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