High-sensitivity detection method for polystyrene plastic based on metal semiconductor composite material

Abstract

The invention discloses a method for high-sensitivity detection of polystyrene plastic based on a metal semiconductor composite material, and belongs to the technical field of nano plastic detection. The detection method comprises the following steps: synthesizing bismuth selenide nanosheets, adding water to disperse, centrifuging, re-dispersing to obtain dispersion liquid, and adding chloroauric acid to react to obtain a metal semiconductor composite material; and mixing the solution to be detected, the dispersion liquid of the composite material and the aggregation agent to form a mixed solution to be detected, and collecting an enhanced Raman spectrum signal of the mixed solution to be detected through a Raman spectrometer to realize the detection of the nano plastic. The metal semiconductor composite material is prepared by reducing chloroauric acid through the bismuth selenide nanosheets, the preparation method is simple, and the composite material can better realize aggregation of nano-plastics and combination with Raman spectrum, and realizes enrichment and high-sensitivity detection of nano-plastic particles in a nano-plastic solution.

Description

Technical Field

[0001] The present invention relates to the technical field of nanoplastics detection, and particularly to a method for highly sensitive detection of polystyrene plastics based on metal-semiconductor composite materials. Background Art

[0002] Nanoplastics are a new type of pollutant that has attracted wide attention at present and pose a threat to human health and the environment. Plastic materials are widely used in the packaging industry, especially in the cosmetics field, and plastic packaging may release nanoplastics into products. When people use cosmetics, even after repeated rinsing, the nanoplastics still adhere to cells, and these nanoplastics can cause ocular surface toxicity and ocular surface dysfunction. In addition, polystyrene plastic particles can enter the human bloodstream, thus affecting vascular health. Therefore, it is necessary to develop a rapid and sensitive method for detecting polystyrene nanoplastics in cosmetics.

[0003] Surface-enhanced Raman spectroscopy has advantages such as rich fingerprint spectra and excellent sensitivity. It realizes single-molecule sensitivity by coupling light into the collective oscillation of free electrons (i.e., surface plasmons) on the surface of nanostructured noble metals. Plasmon polaritons in metals and doped semiconductor materials show broad application prospects in Raman spectroscopy under enhanced field effects. As an alternative to plasmonic materials, topological insulators have attracted wide attention because they can not only support plasmon polaritons generated by mass carriers (such as electrons or holes), but also form corresponding plasmon polaritons by Dirac carriers.

[0004] Currently, the commonly used SERS substrates for detecting nanoplastics include noble metal nanoparticles (such as gold and silver nanoparticles), flexible substrates (such as SERS substrates modified with filter membranes and polymer films), etc. Although they have advantages such as simple preparation and large-area sampling, they have problems such as low sensitivity and large signal interference. Therefore, there is an urgent need to provide a more sensitive method for detecting nanoplastics in cosmetics. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method for highly sensitive detection of polystyrene plastics based on metal-semiconductor composite materials. The present invention prepares a novel metal-semiconductor composite material by reducing chloroauric acid with bismuth selenide nanosheets, and combines Raman spectroscopy to achieve the enrichment and highly sensitive detection of nanoplastics particles in a nanoplastics solution, so as to accurately detect the content of nanoplastics.

[0006] The technical solution of the present invention is as follows:

[0007] The first aspect of the present invention provides a method for detecting nanoplastics based on a metal-semiconductor composite material, and the detection method includes the following steps:

[0008] S1: Provide a test solution containing nanoplastics;

[0009] S2: Add water to disperse the metal-semiconductor composite material to obtain a composite material dispersion;

[0010] S4: Mix the test solution, the composite material dispersion and an aggregating agent to form a test mixture;

[0011] S5: Collect the enhanced Raman spectral signal on the surface of the test mixture through a Raman spectrometer to achieve the detection of nanoplastics;

[0012] Among them, the preparation method of the metal-semiconductor composite material is as follows:

[0013] Synthesize bismuth selenide nanosheets by solvothermal synthesis method, and add water to disperse to obtain a bismuth selenide nanosheet solution;

[0014] Centrifuge the bismuth selenide nanosheet solution and disperse it in a first solvent to obtain a dispersion, mix the dispersion with chloroauric acid for reaction, age, centrifuge, and wash to obtain the metal-semiconductor composite material.

[0015] Preferably, in step S2-1, the preparation method of the bismuth selenide nanosheets is as follows:

[0016] Dissolve bismuth salt and selenite in a reducing agent to obtain a first mixture. Under a nitrogen atmosphere, quickly inject the first mixture into a second mixture, let it stand for reaction and wash to obtain bismuth selenide nanosheets;

[0017] The second mixture is an ethylene glycol solution containing polyvinylpyrrolidone, ascorbic acid and hydrochloric acid.

[0018] Preferably, the reducing agent includes at least one of ethylene glycol, glycerol, diethylene glycol, and polyethylene glycol; and / or, in the first mixture, the bismuth salt is Bi(NO3)3·5H2O; the selenite is Na2SeO3; the mass-volume ratio of the bismuth salt, the selenite to the reducing agent is 5-25 mg: 2.7-13.5 mg: 1.5-7.5 mL; and / or,

[0019] The volume ratio of the reducing agent in the first mixture to the second mixture is 1.5-7.5: 10-50 mL; and / or,

[0020] The second mixture is obtained by mixing polyvinylpyrrolidone, ascorbic acid and hydrochloric acid and then adding ethylene glycol to make up to the required volume; wherein, the concentration of the hydrochloric acid is 10-12 mol / L; the mass-volume ratio of polyvinylpyrrolidone, ascorbic acid to hydrochloric acid is 11-55 mg: 0.67-3.35 g: 30-150 μL; and / or,

[0021] The time of the reaction is 10 to 20 min.

[0022] Preferably, in step S2-1, the bismuth selenide nanosheet solution is obtained by dispersing all the bismuth selenide nanosheets synthesized by solvothermal method in 6 to 30 mL of water.

[0023] In step S2-2, the first solvent includes an aqueous solution of polyvinylpyrrolidone; and / or,

[0024] The concentration of the aqueous solution of polyvinylpyrrolidone is 30 to 60 mg / mL; and / or,

[0025] The volume ratio of the first solvent to the bismuth selenide nanosheet solution is 1 to 5 mL: 0.4 to 2 mL.

[0026] Preferably, in step S2-2, the concentration of chloroauric acid is 10 mmol / L; and / or,

[0027] The volume ratio of the dispersion liquid to the chloroauric acid is 1 to 5 mL: 48.6 to 243 μL; and / or,

[0028] The time of the reaction is 6 to 8 h; and / or,

[0029] The aging time is 20 to 40 min.

[0030] Preferably, in step S1, the concentration of the test solution is 0.001 to 1 mg / mL.

[0031] Preferably, in step S2, the composite material dispersion liquid is obtained by adding 2 to 10 mL of water to the metal semiconductor composite material obtained by washing for dispersion.

[0032] Preferably, in step S4, the aggregating agent includes at least one of NaI solution, NaCl solution, NaBr solution, and KI solution;

[0033] Preferably, the aggregating agent is NaI solution; and / or,

[0034] The concentration of the aggregating agent is 0.1 to 1 mol / L; and / or,

[0035] The volume ratio of the nanoplastics solution, the composite material dispersion liquid to the aggregating agent is 100 to 160: 25 to 40: 25 to 40 μL.

[0036] Preferably, in step S5, the parameters of the Raman spectrometer are: the excitation power is 150 mW, the exposure time is 10 s, the laser wavelength of the laser light source is 785 nm, and the Raman shift range is 600 to 2000 cm -1 .

[0037] Preferably, before step S4, there is also step S3: the process of establishing a standard curve of the concentration of nanoplastics and the Raman spectral signal, which specifically includes the following steps:

[0038] S3: Provide standard solutions containing nanoplastics with different concentrations, and provide the composite material dispersion prepared in step S2; respectively mix the standard solutions containing nanoplastics with different concentrations with the composite material dispersion and the aggregating agent to obtain different standard mixed solutions; collect the surface-enhanced Raman spectral signals of the standard mixed solutions through a Raman spectrometer, and establish a standard curve of the concentration of nanoplastics and the Raman spectral signal;

[0039] Preferably, the volume ratio of the standard solution, the composite material dispersion, and the aggregating agent is 100 - 160:25 - 40:25 - 40 μL.

[0040] Preferably, step S5 further includes: collecting the enhanced Raman spectral signal on the surface of the test mixed solution through a Raman spectrometer, and comparing it with the standard curve, then the content of nanoplastics in the test solution can be obtained, realizing the detection of nanoplastics in the test solution.

[0041] The beneficial technical effects of the present invention are as follows:

[0042] In the present invention, a novel metal-semiconductor composite material is prepared by reducing chloroauric acid with bismuth selenide nanosheets. The preparation method is simple, and the composite material covers gold nanoparticles on the surface of the topological insulator. The topological insulator with internal insulation and surface conductivity has a better synergistic effect with the gold nanoparticles. When the Bi2Se3 nanosheets are combined with the gold nanoparticles, the low redox potential enables the Bi2Se3 nanosheets to act as electron donors, and its topological insulating property promotes the efficient transfer of electrons between the nanosheets and the surface of the gold nanoparticles, improving the sensitivity of Raman detection. At the same time, the composite material can also better realize the aggregation of nanoplastics. The present invention combines the novel metal-semiconductor composite material with Raman spectroscopy to achieve the enrichment and highly sensitive detection of nanoplastics particles in the nanoplastics solution, which can not only detect nanoplastics in the solution, but also more accurately detect the content of nanoplastics. Description of the Drawings

[0043] Figure 1 It is the characterization diagram of each material in Example 1 of the present invention.

[0044] In the figure: a. TEM image of Bi2Se3 NSs, and the inset is the black Bi2Se3 NSs solution. b. TEM image of Au-Bi2Se3 NSs, and the inset is the black-purple Au-Bi2Se3 NSs solution.

[0045] Figure 2The UV-Vis absorption spectra of the materials in Example 1 of the present invention.

[0046] Figure 3 The influence of the aggregating agent used in the present invention on the detection signal.

[0047] Figure 4 The Raman spectra and standard curves of the solutions containing different concentrations of polystyrene nanoplastics in the present invention.

[0048] In the figure: a, Raman spectrogram. b, Standard curve diagram.

[0049] Figure 5 The relative standard deviation of Raman spectroscopy detection in an embodiment of the present invention.

[0050] Figure 6 The SERS spectra of 1 mg / mL 89.3 ± 6.1 nm PS nanoplastics detected with different materials in the present invention.

[0051] Figure 7 The influence of the composite materials in Example 5 and Comparative Example 1 of the present invention on the strength of the Raman spectral signal.

[0052] Figure 8 The Raman responses and relative standard deviations of nanoplastics with different spiked concentrations in the present invention.

[0053] In the figure: a, Raman spectrograms of essence water and different spiked concentrations; b, RSD diagram at a spiked concentration of 0.125 mg / mL; c, RSD diagram at a spiked concentration of 0.375 mg / mL. Detailed implementation manners

[0054] The following describes the present invention in detail in conjunction with the embodiments.

[0055] Currently, the detection of polystyrene nanoplastics by Raman spectroscopy combined with topological insulators has unsatisfactory detection sensitivity and a relatively high detection limit. To solve the above problems, the present invention provides a method for the enrichment and highly sensitive detection of nanoplastics based on surface-enhanced Raman scattering technology. By preparing bismuth selenide nanosheets and using this substance as a reducing agent, chloroauric acid is reduced to gold nanoparticles while a layer of gold nanoparticles is formed on the surface of bismuth selenide. Then, the solution containing nanoporous polystyrene is mixed with the above complex with gold nanoparticles on the surface and an aggregating agent, and after enrichment on the surface of the tin foil, a laser light source is used to irradiate the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil. Finally, Raman spectroscopy detection is used to detect the enriched plastic, and the specific Raman peak signal of the polystyrene plastic is obtained.

[0056] The present invention uses Bi2Se3 as a topological insulator, and its internal insulation and surface conductivity characteristics are synergistic agents that can have a better synergistic effect with gold nanoparticles. When the Bi2Se3 nanosheets are combined with gold nanoparticles, the low redox potential enables the nanosheets to act as electron donors, and their topological insulation characteristics promote the efficient transfer of electrons between the nanosheets and the surface of gold nanoparticles. The composite material based on local surface plasmon resonance can detect nanoplastics in liquids, especially cosmetics, more sensitively, and can improve the sensitivity of Raman detection. In other words, by preparing Bi2Se3 nanosheets and in-situ growing gold nanoparticles on their surfaces, the present invention exhibits stronger Raman performance compared with individual gold nanoparticles. The reason is that Bi2Se3 as an electron donor enables electrons to transfer to the surface of Au NPs, providing better synergy with Au NPs. Bi2Se3 with a larger dielectric constant suppresses the attenuation of electromagnetic waves, further amplifying the SERS performance of the Au-Bi2Se3 nanostructure.

[0057] The detection method of the present invention is simple, and the detection sensitivity is improved by enrichment, and the detection limit is reduced.

[0058] On the one hand, the present invention provides a method for detecting nanoplastics based on surface-enhanced Raman scattering technology, including the following steps:

[0059] S1: Provide a test solution containing nanoplastics;

[0060] S2: Prepare a metal-semiconductor composite material, disperse the prepared metal-semiconductor composite material in water to obtain a metal-semiconductor composite material dispersion;

[0061] S4: Mix the test solution, the metal-semiconductor composite material dispersion and an aggregating agent to form a test mixture;

[0062] S5: Collect the enhanced Raman spectrum signal on the surface of the test mixture by a Raman spectrometer to realize the detection of nanoplastics;

[0063] Wherein, the preparation method of the metal-semiconductor composite material is:

[0064] S2-1: Synthesize bismuth selenide nanosheets by a solvothermal synthesis method, disperse them in water to obtain a bismuth selenide nanosheet solution, and set aside;

[0065] S2-2: Take a part of the bismuth selenide nanosheet solution prepared in step S2-1, centrifuge and disperse it in a first solvent to obtain a dispersion, mix the dispersion with chloroauric acid for reaction, age, centrifuge, and wash to obtain a metal-semiconductor composite material.

[0066] In some specific embodiments, in step S2-1, the preparation method of the bismuth selenide nanosheets is:

[0067] Dissolve bismuth salt and selenite in a reducing agent to obtain a first mixed solution. Under a nitrogen atmosphere, quickly inject the first mixed solution into a second mixed solution, let it stand for reaction and washing to obtain bismuth selenide nanosheets. Among them, the second mixed solution is an ethylene glycol solution containing polyvinylpyrrolidone, ascorbic acid and hydrochloric acid.

[0068] In some embodiments, the reducing agent includes at least one of ethylene glycol, glycerol, diethylene glycol, and polyethylene glycol; preferably, the reducing agent is ethylene glycol.

[0069] In some embodiments, in the first mixed solution, the bismuth salt is Bi(NO3)3·5H2O; the selenite is Na2SeO3; the mass-volume ratio of the bismuth salt, the selenite to the reducing agent is 5-25 mg: 2.7-13.5 mg: 1.5-7.5 mL.

[0070] In some embodiments, the volume ratio of the reducing agent in the first mixed solution to the second mixed solution is 1.5-7.5: 10-50 mL.

[0071] In some embodiments, the second mixed solution is obtained by mixing polyvinylpyrrolidone, ascorbic acid and hydrochloric acid and then making up the volume to the required volume with ethylene glycol; among them, the concentration of the hydrochloric acid is 10-12 mol / L; the mass-volume ratio of polyvinylpyrrolidone, ascorbic acid to hydrochloric acid is 11-55 mg: 0.67-3.35 g: 30-150 μL.

[0072] In some embodiments, the reaction time is 10-20 min.

[0073] In some embodiments, in step S2-1, the bismuth selenide nanosheet solution is obtained by dispersing all the bismuth selenide nanosheets synthesized by solvothermal method in 6-30 mL of water.

[0074] In some embodiments, in step S2-2, the first solvent includes an aqueous solution of polyvinylpyrrolidone.

[0075] In some embodiments, in step S2-2, the concentration of the aqueous solution of polyvinylpyrrolidone is 30-60 mg / mL.

[0076] In some embodiments, in step S2-2, the volume ratio of the first solvent to the bismuth selenide nanosheet solution is 1-5 mL: 0.4-2 mL.

[0077] In some embodiments, the concentration of chloroauric acid is 10 mmol / L.

[0078] In some embodiments, the volume ratio of the dispersion liquid to the chloroauric acid is 1 - 5 mL: 48.6 - 243 μL.

[0079] In some embodiments, the reaction time is 6 - 8 h.

[0080] In some embodiments, the aging time is 20 - 40 min.

[0081] In some embodiments, in step S2, the composite material dispersion liquid is obtained by adding 2 - 10 mL of water to the metal-semiconductor composite material obtained by washing and dispersing it.

[0082] In some embodiments, in step S1, the concentration of the test solution is 0.001 - 1 mg / mL.

[0083] It can be understood that the test solution described in the present invention includes a solution containing nanoplastics. Exemplarily, it can be an aqueous solution containing nanoplastics, cosmetics, such as essence, essence water, etc., and can realize the detection of nanoplastics in cosmetics.

[0084] In some embodiments, in step S4, the aggregating agent includes at least one of NaI solution, NaCl solution, NaBr solution, and KI solution.

[0085] In some embodiments, the aggregating agent is NaI solution.

[0086] In some embodiments, the concentration of the aggregating agent is 0.1 - 1 mol / L.

[0087] In some embodiments, the volume ratio of the nanoplastics solution, the metal-semiconductor composite material dispersion liquid to the aggregating agent is 100 - 160: 25 - 40: 25 - 40 μL.

[0088] In some embodiments, in step S5, the parameters of the Raman spectrometer are: the excitation power is 150 mW, the exposure time is 10 s; the laser wavelength of the laser light source is 785 nm, and the Raman shift range is 600 - 2000 cm -1 。

[0089] It can be understood that the present invention uses polystyrene as a representative for testing. The characteristic peak of polystyrene is most significant at 1001 cm -1 Therefore, this peak value is used as the characteristic peak, and the content of polystyrene is determined by the strength of the corresponding Raman signal.

[0090] It can be understood that through the above method, the present invention can realize the detection of nanoplastics in cosmetics and avoid the harm of nanoplastics in cosmetics to consumers' skin.

[0091] In some embodiments, the present invention can also quantitatively detect the nanoplastics in a sample by first constructing a standard curve of the nanoplastics concentration and the Raman spectroscopy signal. Meanwhile, in cooperation with the prepared composite material, a detection method with high enrichment and sensitivity is provided. The specific method is to add step S3 before the above step S4, and correspond the measured signal with the standard curve to achieve the quantitative detection of the sample. The specific steps are as follows:

[0092] S1: Provide a test solution containing nanoplastics;

[0093] S2: Prepare a dispersion of the metal-semiconductor composite material;

[0094] S3: Provide standard solutions containing nanoplastics with different concentrations and provide the metal-semiconductor composite material; respectively mix the standard solutions containing nanoplastics with different concentrations with the dispersion of the metal-semiconductor composite material and the aggregating agent to obtain different standard mixed solutions; respectively collect the surface-enhanced Raman spectroscopy signals of the standard mixed solutions by a Raman spectrometer, and establish a standard curve of the nanoplastics concentration and the Raman spectroscopy signal.

[0095] S4: Mix the test solution, the dispersion of the metal-semiconductor composite material and the aggregating agent to form a test mixed solution;

[0096] S5: Collect the enhanced Raman spectroscopy signal on the surface of the test mixed solution by a Raman spectrometer, and compare it with the standard curve, then the content of nanoplastics in the test solution can be obtained, and the detection of nanoplastics in the test solution is realized.

[0097] In some embodiments, in step S3, the standard solutions containing nanoplastics with different concentrations are several standard solutions containing nanoplastics with different concentrations taken in the range of 0.001 - 1 mg / mL as the standard solutions.

[0098] In some embodiments, the standard curve is y = 184.5 + 23752.4x, R 2 = 0.997; where x represents the concentration of the solution containing nanoplastics; y represents the spectral signal intensity.

[0099] In some embodiments, in step S5, the parameters of the Raman spectrometer are: the excitation power is 150 mW, the exposure time is 10 s; the optical resolution is 500 times (eyepiece 10x, objective 50x), the laser wavelength of the laser light source is 785 nm, and the Raman shift range is 600 - 2000 cm -1 .

[0100] It can be understood that through the above steps, the present invention can achieve the quantitative detection of nanoplastics in the solution to be measured. And by improving the substrate material, the detection accuracy is further improved.

[0101] It can be understood that to specifically illustrate the reliability of the detection method of the present invention, taking the detection of polystyrene nanoparticles as an example, the construction of the standard curve of the present invention, the preparation of the composite material and the research of the detection conditions will be analyzed and described in detail below.

[0102] The actual sample to be measured used in the present invention is commercially available essence water. The nanoplastics used to prepare the standard solution are polystyrene spheres with a particle size of 89.3 ± 6.1 nm. It can be understood that the present invention takes polystyrene spheres with a particle size of 89.3 ± 6.1 nm as an example for research, and the present invention is not limited to the above particle size, and the detection of polystyrene spheres with other particle sizes is also within the protection scope of the present invention. The raw materials used in the present invention are all commercially available products without special instructions. The polystyrene microspheres can be prepared by a conventional emulsion polymerization method. In some embodiments, the polystyrene microspheres used in the examples of the present invention can be prepared by the following method:

[0103] 0.05 g of SDS (sodium dodecyl sulfate), 44.3145 g of H2O and 0.02475 g of NaHCO3 were added to a flask and reacted at 85 °C. Then 5.63 g of styrene was added, and the mixture was stirred for 1 hour under a N2 atmosphere, and then 0.03275 g of K2S2O8 was introduced. After 12 hours, the product was centrifuged at 10000 rpm and washed three times with ethanol. The product was dried at 40 °C to obtain 89.3 ± 6.1 nm PS plastic for further use.

[0104] The following are specific examples.

[0105] Example 1

[0106] A method for enriching and highly sensitive detecting nanoplastics based on surface-enhanced Raman scattering technology, comprising the following steps:

[0107] S1: Bismuth selenide nanosheets were synthesized by a solvothermal synthesis method.

[0108] Dissolve 25 mg of Bi(NO3)3·5H2O and 13.5 mg of Na2SeO3 in 7.5 mL of ethylene glycol (EG). Then, under a nitrogen atmosphere at 180 °C, quickly inject this solution into a three-neck flask containing 50 mL of EG solution. Among them, the 50 mL EG mixed solution is obtained by taking 55 mg of polyvinylpyrrolidone (PVP), 3.35 g of ascorbic acid (AA), and 150 μL of HCl (11.8 M), and then adding ethylene glycol to make up to 50 mL and mixing. After injection, react for 15 minutes. The obtained bismuth selenide nanosheet seeds are washed once with ethanol, and the bismuth selenide nanosheets are dispersed in 30 mL of water to obtain a Bi2Se3 nanosheet solution.

[0109] Figure 1 Figure a in [reference] shows the TEM image of the bismuth selenide nanosheets. It can be seen from the figure that spherical Bi2Se3 NSs with an average size of 780.5 ± 61.6 nm are successfully synthesized in this example. Figure 2 The UV-visible absorption spectrum of Bi2Se3 NSs is given. It can be seen from the figure that Bi2Se3 NSs show a broad absorption range from 400 nm to 750 nm.

[0110] S2: Use Bi2Se3 nanosheets to directly reduce chloroauric acid to obtain a composite material with gold nanoparticles on the surface, that is, Au-Bi2Se3 NSs.

[0111] Take 2 mL of the above Bi2Se3 nanosheet solution, centrifuge it once, and then disperse it in 5 mL of deionized water containing 50 mg·mL -1 of polyvinylpyrrolidone. Without incubation, directly add 243 μL (10 mM) of HAuCl4 to the solution. Without using an external reducing agent, using Bi2Se3 as the reducing agent, let it stand at room temperature for 7 hours to reduce HAuCl4 to obtain a mixture with gold nanoparticles on the surface. The obtained mixture is aged for 30 minutes, centrifuged at 3000 r / min for 5 minutes, washed 3 times with deionized water to obtain Au-Bi2Se3 NSs, and dispersed in 10 mL of water to obtain an Au-Bi2Se3 NSs dispersion.

[0112] Figure 1 Figure b in [reference] shows the TEM image of Au-Bi2Se3 NSs. It can be seen from the figure that small-sized Au NPs are formed on the large surface area of Bi2Se3 NSs, and the average diameter of Au NPs is about 13.1 ± 3.5 nm. Figure 2 The UV-visible absorption spectrum of Au-Bi2Se3 NSs is given. It can be seen from the figure that Au-Bi2Se3 NSs have an absorption around 597 nm due to the formation of Au NPs.

[0113] S3: Prepare a mixture by mixing an aqueous solution containing polystyrene nanoparticles, the Au-Bi2Se3 NSs dispersion prepared in step S2, and an aggregating agent. Drop the mixture onto an aluminum foil to form water droplets and wait for them to aggregate. The specific method is as follows:

[0114] S3-1: Take 89.3±6.1 nm PS NPs (PS plastic), add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0115] S3-2: Mix 160 μL of the above-mentioned aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL and 40 μL of the Au-Bi2Se3 NSs dispersion prepared in step S2 with 40 μL of 1 M NaI, 40 μL of 1 M NaCl, 40 μL of 1 M NaBr, and 40 μL of 1 M KI respectively to obtain mixed solutions containing different types of aggregating agents; among them, the aggregating agent solution is obtained by dissolving the aggregating agent in water.

[0116] S3-3: Take 50 μL from each of the above-mentioned mixed solutions and drop them onto an aluminum foil to form droplets, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0117] S4: Use a laser light source to irradiate light at the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0118] S5: Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic.

[0119] Specifically, use a Renishaw micro-Raman spectrometer and a 785 nm argon ion laser to measure the Raman spectrum of the aggregated polystyrene nanoparticles to obtain the Raman peak signal of polystyrene plastic. The excitation wavelength of the Raman spectrum is 785 Nm, the excitation power is 150 mW, 500 times (eyepiece 10x, objective 50x), the Raman shift range is 600 to 2000 cm -1 , the exposure time is 10 s, each acquisition is repeated more than 5 times, and its average value is recorded. The Raman signals obtained from the mixed solutions with different types of aggregating agents are as Figure 3 shown. It can be seen from the figure that the characteristic peak of polystyrene is the most significant at 1001 cm -1 . Therefore, this peak value is used as the characteristic peak, and the content of polystyrene is determined by the strength of the corresponding Raman signal. At the same time, by comparing the characteristic peaks of different aggregating agents at 1001 cm -1 , it can be seen that NaI makes Au-Bi2Se3 NSs exhibit the strongest SERS performance. This is because during the salt-induced aggregation process, Na + can neutralize the negative charge and destroy the double electric layer. Introducing I -The impurities on the surface of gold nanoparticles are significantly removed, improving the contact between the PS surface and gold nanoparticles for SERS detection. Therefore, NaI is used as the aggregating agent in the subsequent experiments of the present invention.

[0120] After determining the optimal aggregating agent in Example 1 above, the present invention also investigated different detection conditions.

[0121] Example 2

[0122] A method for enriching and highly sensitive detecting nanoplastics based on surface-enhanced Raman scattering technology, comprising the following steps:

[0123] S1: Bismuth selenide nanosheets were synthesized by a solvothermal synthesis method.

[0124] 5 mg of Bi(NO3)3·5H2O and 2.7 mg of Na2SeO3 were dissolved in 1.5 mL of ethylene glycol (EG). Then, under a nitrogen atmosphere at 180 °C, the solution was rapidly injected into a three-necked flask containing 10 mL of EG solution. Among them, the 10 mL EG mixed solution was obtained by taking 11 mg of polyvinylpyrrolidone (PVP), 0.67 g of ascorbic acid (AA), and 30 μL of HCl (11.8 M), and then adding ethylene glycol to a constant volume of 10 mL. After injection, the reaction was carried out for 15 minutes. The obtained bismuth selenide nanosheet seeds were washed once with ethanol, and the bismuth selenide nanosheets were dispersed in 6 mL of water to obtain a Bi2Se3 nanosheet solution.

[0125] S2: The composite material with gold nanoparticles on the surface, namely Au-Bi2Se3 NSs, was obtained by directly reducing chloroauric acid with Bi2Se3 nanosheets.

[0126] 0.4 mL of the above Bi2Se3 nanosheet solution was centrifuged once and then redispersed in 1 mL of deionized water containing 50 mg·mL -1 of polyvinylpyrrolidone. Without incubation, 48.6 μL (10 mM) of HAuCl4 was directly added to the solution. Without using an external reducing agent, using Bi2Se3 as the reducing agent, it was left standing at room temperature for 7 hours to reduce HAuCl4 to obtain a mixture with gold nanoparticles on the surface. The obtained mixture was aged for 30 minutes, centrifuged at 3000 r / min for 5 minutes, washed 3 times with deionized water to obtain Au-Bi2Se3 NSs, and dispersed in 2 mL of water to obtain an Au-Bi2Se3 NSs dispersion.

[0127] S3: An aqueous solution containing polystyrene nanoparticles, Au-Bi2Se3 NSs, and an aggregating agent were mixed to prepare a mixture. The mixture was dropped on the aluminum foil to form water droplets and waited for them to aggregate. The specific method is as follows:

[0128] S3-1: Take 89.3 ± 6.1 nm PS NPs and add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0129] S3-2: Mix 100 μL of the above aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 25 μL of the Au-Bi2Se3 NSs dispersion, and 25 μL of 1 M NaI to obtain a mixed solution containing an aggregating agent; among them, the aggregating agent solution is obtained by dissolving the aggregating agent in water.

[0130] S3-3: Take 50 μL from the above mixed solution and drop it on the aluminum foil to form droplets, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0131] S4: Use a laser light source to irradiate light at the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0132] S5: Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The specific conditions for Raman detection are the same as those in Example 1.

[0133] Example 3

[0134] A method for the enrichment and highly sensitive detection of nanoplastics based on surface-enhanced Raman scattering technology, comprising the following steps:

[0135] S1: Bismuth selenide nanosheets were synthesized by a solvothermal synthesis method.

[0136] Dissolve 15 mg of Bi(NO3)3·5H2O and 8.1 mg of Na2SeO3 in 4.5 mL of ethylene glycol (EG). Then, under a nitrogen atmosphere at 180 °C, quickly inject this solution into a three-necked flask containing 30 mL of EG solution. Among them, the 30 mL EG mixed solution is obtained by taking 33 mg of polyvinylpyrrolidone (PVP), 2.01 g of ascorbic acid (AA), and 90 μL of HCl (11.8 M), and then adding ethylene glycol to a constant volume of 30 mL for mixing. After injection, react for 15 minutes, wash the obtained bismuth selenide nanosheet seeds once with ethanol, and disperse the bismuth selenide nanosheets in 18 mL of water to obtain a Bi2Se3 nanosheet solution.

[0137] S2: Use Bi2Se3 nanosheets to directly reduce chloroauric acid to obtain a composite material with gold nanoparticles on the surface, namely Au-Bi2Se3 NSs.

[0138] Centrifuge 1.2 mL of the above Bi2Se3 nanosheet solution once, and then disperse it in 3 mL of deionized water containing 50 mg / mL of polyvinylpyrrolidone. Without incubation, directly add 145.8 μL (10 mM) of HAuCl4 to the solution. Without an external reducing agent, using Bi2Se3 as the reducing agent, let it stand at room temperature for 7 hours to reduce HAuCl4 to obtain a mixture with gold nanoparticles on the surface. Age the obtained mixture for 30 minutes, centrifuge it at 3000 r / min for 5 minutes, wash it 3 times with deionized water to obtain Au-Bi2Se3 NSs, and disperse them in 6 mL of water to obtain an Au-Bi2Se3 NSs dispersion.

[0139] S3: Prepare a mixture by mixing an aqueous solution containing polystyrene nanoparticles, Au-Bi2Se3 NSs, and an aggregating agent. Drop the mixture on the aluminum foil to form water droplets and wait for them to aggregate. The specific method is as follows:

[0140] S3-1: Take 89.3 ± 6.1 nm PS NPs and add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0141] S3-2: Mix 120 μL of the above aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 30 μL of the Au-Bi2Se3 NSs dispersion, and 30 μL of 10 M NaI to obtain a mixed solution containing an aggregating agent; among them, the aggregating agent solution is obtained by dissolving the aggregating agent in water.

[0142] S3-3: Take 50 μL from the above mixed solution and drop it on the aluminum foil to form droplets, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0143] S4: Use a laser light source to irradiate light at the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0144] S5: Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The specific conditions for Raman detection are the same as those in Example 1.

[0145] Example 4

[0146] After determining the optimal aggregating agent in the above Example 1, the present invention also investigated the influence of aqueous solutions containing polystyrene nanoparticles with different concentrations on the detection sensitivity, in order to obtain a better detection concentration range, and established a standard curve of the nanoplastics concentration and the Raman spectrum response in this concentration range.

[0147] A method for the enrichment and highly sensitive detection of nanoplastics based on surface-enhanced Raman scattering technology is basically the same as that of Example 1, except for step S3. In this example, the influence of aqueous solutions containing polystyrene nanoparticles with different concentrations on the detection sensitivity is mainly investigated. Therefore, in step S3, aqueous solutions containing polystyrene nanoparticles with different concentrations are used for experiments. The specific steps of step S3 are as follows:

[0148] S3: Mix an aqueous solution containing different concentrations of PS NPs, Au-Bi2Se3 NSs, and an aggregating agent to prepare a mixture. Drop the mixture onto the aluminum foil to form water droplets and wait for them to aggregate. The specific method is as follows:

[0149] S3-1: Weigh different masses of 89.3 ± 6.1 nm PS NPs and add them to deionized water to obtain aqueous solutions containing polystyrene nanoparticles with concentrations of 1 mg / mL, 0.75 mg / mL, 0.5 mg / mL, 0.25 mg / mL, 0.050 mg / mL, 0.025 mg / mL, 0.01 mg / mL, and 0.001 mg / mL respectively, as standard solutions.

[0150] S3-2: Take 160 μL of the above-mentioned aqueous solutions containing polystyrene nanoparticles with different concentrations, mix them with 40 μL of the Au-Bi2Se3 NSs dispersion prepared in step S2 and 40 μL of 1 M NaI respectively to obtain mixed solutions with different concentrations of polystyrene nanoparticles;

[0151] S3-3: Take 50 μL from each of the above-mentioned mixed solutions and drop it onto the aluminum foil to form droplets, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0152] S4: Use a laser light source to irradiate light at the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0153] S5: Use Raman spectroscopy to detect the enriched plastics to obtain the specific Raman peak signals of polystyrene plastics, and different concentrations show different Raman signal intensities.

[0154] Specifically, a Renishaw micro-Raman spectrometer and a 785 nm argon ion laser are used to measure the Raman spectrum of the aggregated polystyrene nanoparticles to obtain the Raman peak signals of polystyrene plastics. The excitation wavelength of the Raman spectrum is 785 Nm, the excitation power is 150 mW, the Raman shift range is 600 to 2000 cm -1 , the exposure time is 10 s, and each acquisition is repeated more than 5 times, and its average value is recorded.

[0155] The obtained Raman signals are as Figure 4 shown, and are obtained from Figure 4As can be seen from Figure a, for PS NPs with a size of 89.3±6.1 nm, the peak intensity increases with the increase of concentration in the concentration range of 0.001 to 1 mg / mL. The detection limit of 89.3±6.1 nm PS NPs detected by the above method is 0.03 μg / mL.

[0156] Meanwhile, Figure 4 In Figure b, in the concentration range of 0.001 to 1 mg / mL, a good linear relationship (standard curve) was established between the intensity of the characteristic peak at 1001 cm -1 and the concentration of plasticizer. The linear relationship formula is: y = 184.5 + 23752.4x, where x is the PS concentration, unit: mg / mL; y is the spectral intensity, and the correlation coefficient R 2 = 0.997.

[0157] In the actual sample detection, the above standard curve can be used to obtain the corresponding concentration by detecting the intensity of the Raman spectrum corresponding to the actual sample.

[0158] To evaluate the reproducibility, five points were randomly selected from the aggregated matrix, and statistical analysis was performed on the peak intensity at 1001 cm -1 . The RSD of this method was 8.2%, as Figure 5 shown.

[0159] The present invention also compared the influence of different SERS substrates on the detection sensitivity, and compared the detection effects of Au-Bi2Se3 NSs prepared in Example 1 with individual Au NPs, Au NPs concentrated twice (Au NPs 2×), Bi2Se3 NSs, and the mixture of Au NPs and Bi2Se3 NSs, respectively. The aggregating agent used in all cases was NaI.

[0160] Comparative Example 1 (using Au NPs instead of Au-Bi2Se3 NSs in Example 1)

[0161] A method for enriching and highly sensitive detecting nanoplastics based on surface-enhanced Raman scattering technology is basically the same as that in Example 1, except that Au NPs are used instead of Au-Bi2Se3 NSs in Example 1, and only 40 μL of 1 M NaI is used as the aggregating agent. The detection method is as follows:

[0162] (1) Mix the aqueous solution, Au NPs and the aggregating agent to prepare a mixture. Drop the mixture on the aluminum foil to form a water droplet and wait for it to aggregate. The specific method is as follows:

[0163] (1-1) Take 89.3±6.1 nm PS NPs and add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0164] (1 - 2) Mix 160 μL of the aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 40 μL of the Au NPs dispersion, and 40 μL of 1 M NaI to obtain a mixed solution. Among them, the Au NPs dispersion is obtained by dispersing the Au NPs reduced from 250 μL of 24.28 mM HAuCl4 in 25 mL of water. The particle size of the Au NPs is 13.1 ± 3.5 nm.

[0165] (1 - 3) Take 50 μL from the above - mentioned mixed solution and drop it on the aluminum foil to form a droplet, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0166] (2) Use a laser light source to irradiate light at the center of the water droplet of the polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0167] (3) Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The parameters and conditions of Raman detection are the same as those in Example 1.

[0168] Comparative Example 2 (Effect of comparing the concentration of Au NPs)

[0169] A method for the enrichment and highly sensitive detection of nanoplastics based on surface - enhanced Raman scattering technology is basically the same as Comparative Example 1, except for the concentration of the Au NPs dispersion used. That is, take 80 μL of the Au NPs dispersion obtained in step (1 - 2) of Comparative Example 1, centrifuge it, and add 40 μL of water to disperse the Au NPs. The parameters and conditions of Raman detection are the same as those in Example 1.

[0170] Comparative Example 3 (Using Bi2Se3 NSs instead of the composite material)

[0171] A method for the enrichment and highly sensitive detection of nanoplastics based on surface - enhanced Raman scattering technology is basically the same as Example 1, except that it does not include step S2. Use the Bi2Se3 NSs prepared in step S1 to replace the composite material in Example 1, and only use 40 μL of 1 M NaI as the aggregating agent. The detection method is as follows:

[0172] S1: Synthesize bismuth selenide nanosheets by a solvothermal synthesis method. The specific method is the same as that in Example 1. Centrifuge the bismuth selenide nanosheets at 3000 r / min for 5 minutes, wash them 3 times with deionized water to obtain Au - Bi2Se3 NSs, and disperse them in 10 mL of water to obtain a Bi2Se3 NSs dispersion.

[0173] S2: Mix an aqueous solution containing polystyrene nanoparticles, a dispersion of Bi2Se3 NSs, and an aggregating agent to prepare a mixture. Drop the mixture onto aluminum foil to form water droplets and wait for them to aggregate.

[0174] S2-1: Take 89.3 ± 6.1 nm PS NPs and add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0175] S2-2: Mix 160 μL of the above aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 40 μL of the Bi2Se3 NSs dispersion, and 40 μL of 1 M NaI to obtain a mixed solution;

[0176] S2-3: Take 50 μL from the above mixed solution and drop it onto aluminum foil to form a droplet, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0177] S3: Use a laser light source to irradiate light at the center of the water droplet of polystyrene nanoparticles to be detected dropped on aluminum foil.

[0178] S4: Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The parameters and conditions of Raman detection are the same as those in Example 1.

[0179] Comparative Example 4 (using a mixture of bismuth selenide + Au NPs)

[0180] A method for enriching and highly sensitive detecting of nanoplastics based on surface-enhanced Raman scattering technology is basically the same as that in Example 1, except that it does not include step S2, and the composite material is a mixture of bismuth selenide nanosheets prepared in step S1 and Au NPs; at the same time, only 40 μL of 1 M NaI is used as the aggregating agent. The detection method is as follows:

[0181] S1: Synthesize bismuth selenide nanosheets by a solvothermal synthesis method. The specific method is the same as that in Example 1. Centrifuge the bismuth selenide nanosheets at 3000 r / min for 5 minutes, wash them 3 times with deionized water to obtain Au-Bi2Se3 NSs, disperse them in 10 mL of water to obtain a Bi2Se3 NSs dispersion. Obtain an Au NPs dispersion according to the method described in Comparative Example 1; take 1 mL of the Au NPs dispersion and mix it evenly with 1 mL of the bismuth selenide nanosheet dispersion to obtain a mixed material solution for standby.

[0182] S2: Mix an aqueous solution containing polystyrene nanoparticles, the mixed material solution, and an aggregating agent to prepare a mixture. Drop the mixture onto aluminum foil to form water droplets and wait for them to aggregate.

[0183] S2-1 Take 89.3 ± 6.1 nm PS NPs and add them to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0184] S2-2 Mix 160 μL of the above aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 40 μL of the mixed material solution, and 40 μL of 1 M NaI to obtain a mixed solution.

[0185] S2-3 Take 50 μL from the above mixed solution and drop it on the aluminum foil to form a droplet, and wait for 120 min for the polystyrene nanoparticles to aggregate.

[0186] S3 Use a laser light source to irradiate light at the center of the water droplet of polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0187] S4 Use Raman spectroscopy to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The parameters and conditions of Raman detection are the same as those in Example 1.

[0188] Figure 6 The detection results corresponding to different materials in Example 1 and Comparative Examples 1-4 are given. It can be seen from the figure that compared with single AuNPs and Au NPs concentrated twice (Au NPs 2×) or Bi2Se3 NSs, Au-Bi2Se3 NSs show the highest SERS enhancement, where 1001 cm -1The SERS intensities at [specific location] are 5.1 times and 10.2 times those of Au NPs and Bi2Se3 NSs, respectively. The physical mixture of Au NPs and Bi2Se3 NSs (Au NPs + Bi2Se3 NSs) also has lower SERS performance than Au-Bi2Se3 NSs. The heterostructure of Au NPs and Bi2Se3 NSs endows Au-Bi2Se3 NSs with enhanced SERS activity. This is due to the strong electromagnetic field and effective electron transfer mechanism. Compared with pure Au NPs, the high dielectric constant of Bi2Se3 NSs significantly enhances the magnetic field of Au NPs. This enhanced electromagnetic field endows the Au-Bi2Se3 composite with strong SERS performance. In addition, the enhancement of SERS activity is closely related to the electron transfer mechanism. The bandgap of Bi2Se3 is 1.2 eV. Under 785 nm (1.6 eV) laser irradiation, electrons are easily excited from the valence band to the conduction band, generating excited electrons. Electrons are more likely to transfer from a material with a lower work function to a material with a higher work function. The work functions of Bi2Se3 NSs and Au NPs are 4.4 eV and 4.9 eV, respectively, indicating that the electrons excited in the valence band (VB) of Bi2Se3 NSs can easily migrate to Au NPs through their strong interfacial connection, which also amplifies the electromagnetic field. This enhanced electromagnetic field endows the Au-Bi2Se3 composite with powerful SERS performance.

[0189] Example 5

[0190] A method for the enrichment and highly sensitive detection of nanoplastics based on surface-enhanced Raman scattering technology is basically the same as that in Example 1, except for step S2, and only 40 μL of 1M NaI is used as the aggregating agent. The detection method is as follows:

[0191] S1: Bismuth selenide nanosheets were synthesized by a solvothermal synthesis method. The specific method is the same as that in Example 1.

[0192] S2: The 2 mL of the above Bi2Se3 nanosheet solution was centrifuged once and then redispersed in 5 mL of deionized water containing 50 mg·mL -1 polyvinylpyrrolidone. Without incubation, 243 μL (10 mM) of silver nitrate was directly added to the solution. It was left standing at room temperature for 7 hours, then aged for 30 minutes, centrifuged at 3000 r / min for 5 minutes, and washed 3 times with deionized water to obtain Ag-Bi2Se3 NSs, which were dispersed in 10 mL of water to obtain an Ag-Bi2Se3 NSs dispersion.

[0193] S3: An aqueous solution containing polystyrene nanoparticles, the Ag-Bi2Se3 NSs dispersion, and the aggregating agent were mixed to prepare a mixture. The mixture was dropped on the aluminum foil to form water droplets and waited for them to aggregate.

[0194] In S3-1, 89.3 ± 6.1 nm PS NPs were taken and added to deionized water to obtain an aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL.

[0195] In S3-2, 160 μL of the above aqueous solution containing polystyrene nanoparticles with a concentration of 1 mg / mL, 40 μL of Ag-Bi2Se3 NSs dispersion, and 40 μL of 1 M NaI were mixed to obtain a mixed solution.

[0196] In S3-3, 50 μL was taken from the above mixed solution and dropped on an aluminum foil to form a droplet, and waited for 120 min to allow the polystyrene nanoparticles to aggregate.

[0197] In S4, a laser light source was used to irradiate light at the center of the water droplet of polystyrene nanoparticles to be detected dropped on the aluminum foil.

[0198] In S5, Raman spectroscopy was used to detect the enriched plastic to obtain the specific Raman peak signal of polystyrene plastic. The parameters and conditions of Raman detection were the same as those in Example 1.

[0199] Figure 7 Compared with Comparative Example 1 of single Ag NPs, in this example, Ag-Bi2Se3 NSs were used, showing stronger SERS enhancement. Among them, the SERS intensity at 1001 cm -1 was 4.73 times that of Ag NPs. However, the SERS intensity was reduced compared with that of Au-Bi2Se3, which was caused by the different sizes and loadings of Ag NPs loaded on Bi2Se3.

[0200] The present invention further investigated the use of actual samples and spiked actual samples for detection to investigate the spike recovery rate of essence water containing PS and the standard deviation in the detection of actual samples.

[0201] Example 6

[0202] Different amounts of 89.3 ± 6.1 nm PS spheres were added to essence water to obtain essence water with different spiked PS sphere concentrations (the spiked concentrations were 0.375 mg / mL and 0.125 mg / mL respectively). 160 μL of essence water containing different spiked PS concentrations and essence water without additional PS spheres added (as a blank) were taken respectively, and directly added to 40 μL of Au-Bi2Se3 material dispersion prepared in Example 1 and 40 μL of aggregating agent (NaI) of 1 mol / L without dilution to prepare a mixture.

[0203] 50 μL of the mixture was dropped on tin foil to form a water droplet. After waiting for it to aggregate, then the laser was focused on the top of the water droplet for SERS detection, and the detection conditions were the same as those in Example 1.

[0204] The test diagram and results are shown in Figure 8 The results show that Figure 8 In Figure a, the blank SERS of the essence water is at 1001 cm -1 There is no characteristic peak at 1001cm -1 A characteristic peak appeared at 100 nm, confirming the successful detection of polystyrene plastic. As the concentration increases, the Raman intensity also increases. When the spike concentration is 0.125 mg / mL, the detection concentration is calculated to be 0.118 ± 0.004 mg / mL based on the standard curve of 89.3 ± 6.1 nm PS NPs, with an RSD of only 5.5% ( Figure 8 When the spike concentration was 0.375 mg / mL, the detected concentration was 0.356±0.009 mg / mL, and the RSD was only 4.0% ( Figure 8 These results indicate that Au-Bi2Se3 nanosheets have high sensitivity and accuracy in detecting PS nanoplastics in cosmetics, showing great potential in detecting nanoplastics in cosmetics.

[0205] For samples with low polystyrene content, when direct detection is difficult to measure, the method of the present invention can be combined to establish a standard curve to obtain the spectral signal intensity at a specific standard concentration, and then add the standard concentration solution to the sample to be tested, test the spectral intensity of the sample to be tested at this time, and compare it with the spectral intensity of the standard solution alone, so as to obtain the concentration of the sample that is difficult to measure. At this time, the lower limit of the polystyrene plastic concentration in the sample that can be measured is 3×10 -4 mg / mL.

[0206] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A method for detecting nanoplastics based on a metal-semiconductor composite material, characterized in that, The detection method includes the following steps: S1: Provide a test solution containing nanoplastics; S2: Add water to disperse the metal-semiconductor composite material to obtain a composite material dispersion; S4: Mix the test solution, the composite material dispersion, and an aggregating agent to form a test mixture; S5: Collect the enhanced Raman spectroscopic signal on the surface of the test mixture by a Raman spectrometer to achieve the detection of nanoplastics; Among them, the preparation method of the metal-semiconductor composite material is: S2-1: Synthesize bismuth selenide nanosheets by a solvothermal synthesis method, and add water to disperse to obtain a bismuth selenide nanosheet solution; S2-2: Take the bismuth selenide nanosheet solution, centrifuge and disperse it in a first solvent to obtain a dispersion, mix the dispersion with chloroauric acid for reaction, age, centrifuge, and wash to obtain the metal-semiconductor composite material.

2. The nano-plastic detection method according to claim 1, characterized in that, In step S2-1, the preparation method of the bismuth selenide nanosheets is: Dissolve bismuth salt and selenite in a reducing agent to obtain a first mixture. Under a nitrogen atmosphere, quickly inject the first mixture into a second mixture, let it stand for reaction and wash to obtain bismuth selenide nanosheets; The second mixture is an ethylene glycol solution containing polyvinylpyrrolidone, ascorbic acid, and hydrochloric acid.

3. The nano-plastic detection method according to claim 2, characterized in that, The reducing agent includes at least one of ethylene glycol, glycerol, diethylene glycol, and polyethylene glycol; and / or, in the first mixture, the bismuth salt is Bi(NO3)3·5H2O; the selenite is Na2SeO3; the mass-volume ratio of the bismuth salt, the selenite, and the reducing agent is 5-25 mg: 2.7-13.5 mg: 1.5-7.5 mL; and / or, The volume ratio of the reducing agent in the first mixture to the second mixture is 1.5-7.5: 10-50; and / or, The second mixture is obtained by mixing polyvinylpyrrolidone, ascorbic acid, and hydrochloric acid, and then adding ethylene glycol to make up to the required volume; among them, the concentration of the hydrochloric acid is 10-12 mol / L; the mass-volume ratio of polyvinylpyrrolidone, ascorbic acid, and hydrochloric acid is 11-55 mg: 0.67-3.35 g: 30-150 μL; and / or, The reaction time is 10-20 min.

4. The nano-plastic detection method according to claim 1, characterized in that, In step S2-1, the bismuth selenide nanosheet solution is obtained by dispersing all the bismuth selenide nanosheets synthesized by solvothermal synthesis in 6-30 mL of water; In step S2-2, the first solvent includes an aqueous polyvinylpyrrolidone solution; and / or, The concentration of the aqueous polyvinylpyrrolidone solution is 30-60 mg / mL; and / or, The volume ratio of the first solvent to the bismuth selenide nanosheet solution is 1-5 mL: 0.4-2 mL.

5. The nano-plastic detection method according to claim 1, characterized in that, In step S2-2, the concentration of the chloroauric acid is 10 mmol / L; and / or, The volume ratio of the dispersion to the chloroauric acid is 1-5: 48.6-243 μL; and / or, The reaction time is 6-8 h; and / or, The aging time is 20-40 min.

6. The nano-plastic detection method according to claim 1, characterized in that, In step S1, the concentration of the test solution is 0.001-1 mg / mL; and / or, In step S2, the composite material dispersion is obtained by adding 2 - 10 mL of water to the metal semiconductor composite material obtained in step S2-2 and dispersing it.

7. The nano-plastic detection method according to claim 1, wherein In step S4, the aggregating agent includes at least one of NaI solution, NaCl solution, NaBr solution, and KI solution; Preferably, the aggregating agent is NaI solution; and / or the concentration of the aggregating agent is 0.1 - 1 mol / L; and / or the volume ratio of the nanoplastics solution, the composite material dispersion, and the aggregating agent is 100 - 160:25 - 40:25 - 40 μL.

8. The nano-plastic detection method according to claim 1, characterized in that, In step S5, the parameters of the Raman spectrometer are as follows: the excitation power is 150 mW, and the exposure time is 10 s; the laser wavelength of the laser light source is 785 nm, and the Raman shift range is 600 - 2000 cm -1 .

9. The nano-plastic detection method according to any one of claims 1-8, characterized in that, Before step S4, there is also step S3: the process of establishing a standard curve of nanoplastics concentration and Raman spectroscopy signal, which specifically includes the following steps: S3: Provide standard solutions containing nanoplastics with different concentrations and the composite material dispersion obtained in step S2; respectively mix the standard solutions containing nanoplastics with different concentrations with the composite material dispersion and the aggregating agent to obtain different standard mixed solutions; collect the surface-enhanced Raman spectroscopy signals of the standard mixed solutions through a Raman spectrometer respectively, and establish a standard curve of nanoplastics concentration and Raman spectroscopy signal; Preferably, the volume ratio of the standard solution, the composite material dispersion, and the aggregating agent is 100 - 160:25 - 40:25 - 40 μL.

10. The nano-plastic detection method according to claim 9, wherein, Step S5 further includes: collecting the enhanced Raman spectroscopy signal on the surface of the test mixed solution through a Raman spectrometer, and comparing it with the standard curve, then the content of nanoplastics in the test solution can be obtained, realizing the detection of nanoplastics in the test solution.

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