SERS-optimization algorithm detection method of silver nanowire network structure for nano-plastic
Through the combination of silver nanowire network structure and Raman spectroscopy, the challenges of nanoplastic detection in the prior art are solved, and efficient separation and analysis of nanoplastics are achieved, reducing costs and complexity.
Patent Information
- Application Number
- CN202411575355.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-06
- Publication Date
- 2025-02-11
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
When existing Raman spectroscopy is combined with scanning electron microscopy, although the spatial resolution can be reduced to 100 nm, more advanced instrumentation or pretreatment steps are required and are challenging to detect nanoplastics.
The silver nanowire network structure is combined with Raman spectroscopy, and nanoplastic molecules are captured by adjusting the density of the silver nanowire network structure, and the non-negative least squares method is used for identification and analysis.
It realizes the separation and analysis of a variety of nanoplastics, reduces the cost of equipment installation, is simple to operate, accurate and intuitive data, and is suitable for a wide range of inspection applications.
Smart Images
Figure CN119413776A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of Raman spectrum detection, and in particular relates to a SERS-optimization algorithm detection method for a silver nanowire network structure used in nanoplastics. Background Art
[0002] Plastic fragments with a diameter of less than 5 mm are usually called microplastics, and those with a diameter of less than 1um are called nanoplastics. They can enter the environment through various channels, including the atmosphere, water bodies and soil. The hazards of micro-nano plastics are mainly reflected in the following three aspects. The first is the harm to the environment. Micro-nano plastics can enter the food chain and affect the balance of the ecosystem. Second, they are particularly harmful to aquatic organisms because micro-nano plastics can be accidentally ingested, causing physical or chemical damage. They are also bioaccumulative. Micro-nano plastics can absorb other harmful chemicals, thereby increasing their impact on the environment and organisms. Third, the impact on human health. Nanoplastics are more easily entered into the human body through food and water. Although the direct impact of micro-nano plastics on human health is not yet fully understood, studies have shown that nanoplastics have been detected in various system tissues of the human body, and they may affect the digestive system, immune system and reproductive system; and due to their size, nanoplastics are more harmful and more difficult to detect. Due to their small size, micro-nano plastics are very challenging to detect. The main methods used are based on mass spectrometry and spectroscopy (FTIR, SERS), which are generally only used to detect microplastics at the micron level. However, mass spectrometry-based methods generally require complex pretreatment and enrichment steps, and cannot handle samples containing water.
[0003] Spectroscopic techniques usually involve the use of multiple instruments, such as FTIR or Raman spectroscopy combined with a microscope, but the resolution is only at the micron level, which is not suitable for the detection of nanoplastics. When Raman spectroscopy is combined with a scanning electron microscope (SEM), the spatial resolution can be reduced to 100nm, but more advanced instruments or pretreatment steps are required, and other substances in complex samples may interfere with spectral analysis. Summary of the invention
[0004] The present invention aims to provide a SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure, which has sensitive and rapid detection, low cost, and a wide range of applications, and solves the problem that when Raman spectroscopy is currently combined with a scanning electron microscope, the spatial resolution can be reduced to 100nm, but more advanced instruments or pretreatment steps are required.
[0005] To this end, the technical solution adopted by the present invention is: a SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure, comprising the following steps:
[0006] Step S1, washing the crude silver nanowire product with deionized water and drying it, performing plasma modification treatment, and then immersing it in an ethanol solution and drying it. The above operation is repeated until separated and purified silver nanowires are obtained, and the separated and purified silver nanowires are dissolved in an equal volume of anhydrous ethanol to generate a silver nanowire solution;
[0007] Step S2, uniformly dropping the prepared silver nanowire solution onto the microporous membrane, and simultaneously using a vacuum filtration device to perform vacuum filtration to obtain a microporous membrane with a silver nanowire network structure, and adjusting the density of the silver nanowire network structure according to the size of the micro-nano plastic molecules to capture all the micro-nano plastic molecules;
[0008] Step S3, dropping suspensions of micro-nano plastic molecules of different types and with the same concentration on the microporous membrane with the silver nanowire network structure in sequence using a glass micropipette, drying the microporous membrane, and then performing surface enhanced Raman spectroscopy detection and collection on the microporous membrane;
[0009] Step S4, use non-negative least squares method to identify the collected micro-nano plastic molecules, collect spectral data, and average the collected spectral data, set it as a standard spectral sample, and then use the mixed sample spectrum in the mixed data folder to calculate the contribution of each sample in the mixed sample; then use non-negative least squares method to solve the contribution coefficient of each sample, and output the main components and contribution of each mixed sample, and finally use python drawing to visualize the three-dimensional graph result output.
[0010] As a preferred embodiment of the above scheme, in step S2, the concentration of the silver nanowire liquid or the amount of silver nanowire liquid added is positively correlated with the density of the silver nanowire network structure. The more liquid is added or the higher the concentration is, the denser the grid structure is, and the less liquid is added or the lower the concentration is, the sparser the grid structure is. The density of the network structure can be selected according to the size of the micro-nano plastic molecules, so that the micro-nano plastic molecules can be completely captured.
[0011] More preferably, in step S2, the microporous membrane is made of organic nylon polytetrafluoroethylene, and the micropore diameter of the microporous membrane is 0.22 μm. After many experimental attempts, the size is reasonable.
[0012] Further preferably, in the step S3, the micro-nano plastic molecule suspensions are respectively polyvinyl fluoride PS suspension, polyethylene PE suspension, polypropylene PP suspension and mixed suspension, and the mixed suspension is prepared by mixing polyvinyl fluoride PS, polyethylene PE and polypropylene PP in a designed proportion, and different types of micro-nano plastic molecules are used for comparison, so as to compare the data analysis results of collecting different types of micro-nano plastic molecules by surface enhanced spectroscopy detection using the grid membrane, and the design is reasonable.
[0013] Further preferably, four polyvinyl fluoride PS plastic molecular sizes of 100nm, 500nm, 1um, and 4um are used to prepare four polyvinyl fluoride PS suspensions with the same concentration but different plastic molecular sizes, and 500nm polyethylene PE or polypropylene PP plastic molecular sizes are used to prepare polyethylene PE suspensions or polypropylene PP suspensions respectively. Polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecular size of 500nm are mixed in ratios of 1:1:1, 10:1:1, 100:1:1, 100:10:1, and 100:1:10 to prepare five mixed suspensions with the same concentration but different mixing ratios. The design is reasonable, and micro-nano plastic molecular suspensions of different sizes or different ratios are selected for data analysis, which is a reasonable design.
[0014] More preferably, in step S3, during the surface enhanced Raman spectroscopy detection and collection process, the parameters are selected as 50× objective lens and the collection wavelength range is 550cm -1 ~1800cm -1 The acquisition time was 10 s, and all Raman spectroscopy results were baseline corrected, and the parameters were reasonable.
[0015] Further preferably, in the step S1, the preparation steps of the silver nanowire crude product are as follows: measure 50 mL of ethylene glycol, slowly add 1.86 g of polyethylene PE pyrrolidone under stirring to prevent it from condensing into lumps, until the mixed system is evenly dissolved, then measure 50 mL of ethylene glycol to rinse the beaker, and pour all the mixed solution into a three-necked flask, drop 1 mL of a certain concentration of chloride control agent prepared, and heat the reaction in an oil bath at 160°C for 1 hour, then completely cover the beaker with tin foil, weigh 0.5 g of AgNO3 solid, and stir it into a uniform solution with 25 mL of ethylene glycol, after stirring, use a peristaltic pump to drop it into the three-necked flask at a speed of 75 mL / h, continue heating and reacting for 1.5 hours, and air cool the gray-green oily liquid obtained by the reaction to room temperature, then transfer it to a centrifuge tube, add anhydrous ethanol for multiple centrifugal washings, and the configuration is reasonable.
[0016] Beneficial effects of the present invention:
[0017] (1) Compared with the current combination of Raman spectroscopy and scanning electron microscopy (SEM), the spatial resolution can be reduced to 100 nm, but more advanced instruments or pretreatment steps are required. This solution does not require additional instruments. It cleverly uses the silver nanowire network structure used on the microporous membrane and combines it with Raman spectroscopy. The density of the silver nanowire network structure is adjusted according to the size of the micro-nano plastic molecules to capture all the micro-nano plastic molecules, thereby achieving the separation and analysis of a variety of nanoplastic targets. The equipment has low installation costs and is simple to operate.
[0018] (2) In order to analyze the problem of confirming the composition of nanoplastics in different types of micro-nanoplastic molecular suspensions, the non-negative least squares method was used to identify the collected micro-nanoplastic molecules and calculate the contribution of each sample in the mixed sample. The non-negative least squares method was also used to analyze the contribution coefficient of the same sample to various mixed data sets to determine the main components. The non-negative least squares method performs very well in this linear combination problem and can accurately estimate the contribution ratio of each component. It has great application potential. Finally, Python is used to draw a three-dimensional visualized graph to output the results, and the data is accurate and intuitive.
[0019] In summary, the present invention has the advantages of separation and analysis of various nanoplastic targets, low equipment installation cost, simple operation, huge application potential, accurate and intuitive data, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a scanning electron microscope characterization image of microplastic small molecules on the silver nanowire AgNws network structure.
[0021] Figure 2 This is a scanning electron microscope characterization image of microplastic macromolecules on the silver nanowire AgNws network structure.
[0022] Figure 3 These are the surface enhanced Raman spectroscopy test results of nanoplastics with network structures of different densities and molecular sizes of polyvinyl fluoride (PS) plastics.
[0023] Figure 4 The molecular weight of polyvinyl fluoride PS plastic is 1×10 -3 ~1×10 -6 Surface enhanced Raman spectroscopy over the (mg / mL) concentration range.
[0024] Figure 5 Surface-enhanced Raman spectra of nanoplastic molecules in suspensions mixed with five different mixing ratios.
[0025] Figure 6 Homogeneity of substrate for surface enhanced Raman spectroscopy.
[0026] Figure 7 It is the contribution of each plastic molecule of polyvinyl fluoride PS, polyethylene PE and polypropylene PP in five mixed suspensions mixed in different proportions using the non-negative least squares optimization algorithm, as well as the average value of the contribution.
[0027] Figure 8 This is a three-dimensional graph of the proportions of polyvinyl fluoride PS, polyethylene PE, and polypropylene PP plastic molecules in mixed suspensions with different mixing ratios. DETAILED DESCRIPTION
[0028] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:
[0029] Combination Figure 1 — Figure 8 As shown, a silver nanowire network structure is used for a SERS-optimized algorithm detection method of nanoplastics, and the specific implementation steps are as follows:
[0030] Step S1, washing and drying the crude silver nanowire AgNws product with deionized water, performing plasma modification treatment, and then immersing it in an ethanol solution and drying it. The above operation is repeated to obtain separated and purified silver nanowires AgNws, and the separated and purified silver nanowires AgNws are dissolved in an equal volume of anhydrous ethanol to generate a silver nanowire AgNws solution.
[0031] In step S1, the preparation steps of the crude product of silver nanowires AgNws are as follows: measure 50mL of ethylene glycol, slowly add 1.86g of polyethylene PE pyrrolidone under stirring to prevent it from condensing into lumps, until the mixed system is evenly dissolved, then measure 50mL of ethylene glycol to rinse the beaker, and pour all the mixed solution into a three-necked flask, drop 1mL of a certain concentration of chloride control agent prepared, and heat the reaction in an oil bath at 160°C for 1h, then completely cover the beaker with tin foil, weigh 0.5g of AgNO3 solid, and stir it into a uniform solution with 25mL of ethylene glycol. After stirring, use a peristaltic pump to drop it into the three-necked flask at a rate of 75mL / h, continue heating and reacting for 1.5h, and air cool the gray-green oily liquid obtained by the reaction to room temperature, then transfer it to a centrifuge tube, add anhydrous ethanol and perform multiple centrifugal washings.
[0032] Step S2, uniformly adding the prepared silver nanowire AgNws solution to the microporous membrane, and simultaneously using a vacuum filtration device for vacuum filtration to obtain a microporous membrane with a silver nanowire AgNws network structure, and adjusting the density of the silver nanowire AgNws network structure according to the size of the micro-nano plastic molecules to capture all the micro-nano plastic molecules.
[0033] In step S2, the concentration of the silver nanowire AgNws liquid or the amount of silver nanowire AgNws liquid added is positively correlated with the density of the silver nanowire AgNws network structure. The more liquid is added or the higher the concentration is, the denser the network structure is, and the less liquid is added or the lower the concentration is, the sparser the network structure is.
[0034] The silver nanowires AgNws prepared from the silver nanowire AgNws solution prepared as described above have a dense network structure.
[0035] In step S2, the microporous membrane is made of organic nylon polytetrafluoroethylene, and the micropore diameter of the microporous membrane is 0.22 μm.
[0036] Step S3, dropping different types of micro-nano plastic molecular suspensions of the same concentration on the microporous membrane with the silver nanowire AgNws network structure in sequence using a glass micropipette, drying the microporous membrane, and then performing surface enhanced Raman spectroscopy detection and collection on the microporous membrane;
[0037] In step S3, the micro-nano plastic molecule suspensions are polyvinyl fluoride PS suspension, polyethylene PE suspension, polypropylene PP suspension, and mixed suspension, and the mixed suspension is prepared by mixing polyvinyl fluoride PS, polyethylene PE, and polypropylene PP in a designed proportion.
[0038] Four polyvinyl fluoride PS suspensions with the same concentration but different plastic molecular sizes were prepared using four polyvinyl fluoride PS plastic molecular sizes of 100nm, 500nm, 1um, and 4um respectively. Polyethylene PE or polypropylene PP plastic molecular sizes of 500nm were used to prepare polyethylene PE suspensions or polypropylene PP suspensions respectively. Polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecular size of 500nm were mixed in ratios of 1:1:1, 10:1:1, 100:1:1, 100:10:1, and 100:1:10 respectively to prepare five mixed suspensions with the same concentration but different mixing ratios.
[0039] In step S3, during the surface enhanced Raman spectroscopy detection and collection process, the parameters are selected as 50× objective lens and the collection wavelength range is 550cm -1 ~1800cm -1 The acquisition time was 10 s, and all Raman spectra were baseline corrected.
[0040] Figure 1 Shown is a scanning electron microscope characterization of microplastic molecules on the silver nanowire AgNws network structure.
[0041] like Figure 1 As shown, it can be seen from the scanning electron microscope image that silver nanowires AgNws are stacked into a network structure, and the crossed silver nanowires AgNws produce irregular electric field enhancement. A large number of hot spots will be generated at the intersection of the silver nanowires AgNws to achieve electric field enhancement; the microplastic molecules are in the lattice gaps in the silver nanowire AgNws network structure, and the microplastic small molecules are in the hot spot area, which has a good surface enhanced Raman spectroscopy enhancement effect.
[0042] Figure 2 Shown is a scanning electron microscope characterization of microplastic macromolecules on the silver nanowire AgNws network structure.
[0043] like Figure 2 As shown, the microplastic macromolecules are located on the lattice points and cannot penetrate, resulting in a weaker enhancement effect.
[0044] Figure 3The results of surface enhanced Raman spectroscopy detection of nanoplastics by network structures of different densities and molecular sizes of polyvinyl fluoride (PS) plastics are shown.
[0045] like Figure 3 As shown, two polyvinyl fluoride PS suspensions with different plastic molecular sizes of 100nm and 4um were used for comparison.
[0046] Figure 4 The polyvinyl fluoride PS plastic molecule is shown in 1×10 -3 ~1×10 -6 Surface enhanced Raman spectroscopy in the concentration range of (mg / mL) showed that the -1 There are obvious Raman characteristic peaks.
[0047] The surface enhanced Raman spectroscopy measurement parameters were as follows: a 633 nm laser was used, and the acquisition time for each spot was 10 s.
[0048] Figure 5 The surface enhanced Raman spectra of nanoplastic molecules in mixed suspensions with five different mixing ratios are shown.
[0049] Figure 6 The overall homogeneity of the SERS substrate is shown.
[0050] like Figure 6 As shown, Figure 6 (a) means 1449.7cm -1 The logarithmic relationship between the concentration of the mixed suspension of polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecule size of 500nm and a mixture of 1:1:1 and the intensity of the surface enhanced Raman spectrum. Figure 6 (b) shows the SERS spectra of 5 randomly selected points on the SERS substrate for random detection. 6(c) shows 8 SERS spectra of the same hybrid nanoparticles.
[0051] Step S4, use non-negative least squares method to identify the collected micro-nano plastic molecules, collect spectral data, and average the collected spectral data, set it as a standard spectral sample, and then use the mixed sample spectrum in the mixed data folder to calculate the contribution of each sample in the mixed sample; then use non-negative least squares method to solve the contribution coefficient of each sample, and output the main components and contribution of each mixed sample, and finally use python drawing to visualize the three-dimensional graph result output.
[0052] Figure 7The results of data processing by the non-negative least squares optimization algorithm are shown. Polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecule size of 500nm are mixed in the ratio of 1:1:1, 10:1:1, 100:1:1, 100:10:1, and 100:1:10 to prepare five mixed suspensions with the same concentration but different mixing ratios.
[0053] like Figure 7 As shown in (a), 7(b), 7(c), 7(d), and 7(e), it can be seen that the contribution of each of the polyvinyl fluoride PS, polyethylene PE, and polypropylene PP plastic molecules in the five mixed suspensions mixed in the above proportions in sequence using the non-negative least squares optimization algorithm, as well as the average contribution.
[0054] After processing each mixed Raman data, the specific values of the three contributions of polyvinyl fluoride PS, polyethylene PE, and polypropylene PP plastic molecules are obtained, and then the values are presented on the graph in the form of a bar graph.
[0055] Figure 8 A three-dimensional graph showing the proportions of polyvinyl fluoride PS, polyethylene PE, and polypropylene PP plastic molecules in mixed suspensions with different mixing ratios.
[0056] like Figure 8 As shown, Figure 8 (a) Represents the proportion of various microplastics when polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecule size of 500nm are mixed in a ratio of 1:1:1. Figure 8 (b) shows the proportion of various microplastics when polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecule size of 500nm are mixed in a ratio of 10:1:1. Figure 8 (c) shows the proportion of various microplastics when polyvinyl fluoride PS, polyethylene PE, and polypropylene PP with a plastic molecule size of 500nm are mixed in a ratio of 100:1:1.
Claims
1. A SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure, characterized in that: The following steps are involved: Step S1, washing the crude silver nanowire product with deionized water and drying it, performing plasma modification treatment, and then immersing it in an ethanol solution and drying it. The above operation is repeated until separated and purified silver nanowires are obtained, and the separated and purified silver nanowires are dissolved in an equal volume of anhydrous ethanol to generate a silver nanowire solution; Step S2, uniformly dropping the prepared silver nanowire solution onto the microporous membrane, and simultaneously using a vacuum filtration device to perform vacuum filtration to obtain a microporous membrane with a silver nanowire network structure, and adjusting the density of the silver nanowire network structure according to the size of the micro-nano plastic molecules to capture all the micro-nano plastic molecules; Step S3, dropping suspensions of micro-nano plastic molecules of different types and with the same concentration on the microporous membrane with the silver nanowire network structure in sequence using a glass micropipette, drying the microporous membrane, and then performing surface enhanced Raman spectroscopy detection and collection on the microporous membrane; Step S4, use non-negative least squares method to identify the collected micro-nano plastic molecules, collect spectral data, and average the collected spectral data, set it as a standard spectral sample, and then use the mixed sample spectrum in the mixed data folder to calculate the contribution of each sample in the mixed sample; then use non-negative least squares method to solve the contribution coefficient of each sample, and output the main components and contribution of each mixed sample, and finally use python drawing to visualize the three-dimensional graph result output.
2. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 1, characterized in that: In the step S2, the concentration of the silver nanowire liquid or the amount of the silver nanowire liquid added is positively correlated with the density of the silver nanowire network structure. The more liquid is added or the higher the concentration is, the denser the network structure is, and the less liquid is added or the lower the concentration is, the sparser the network structure is.
3. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 1, characterized in that: In the step S2, the microporous membrane is made of organic nylon polytetrafluoroethylene, and the micropore diameter of the microporous membrane is 0.22 μm.
4. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 1, characterized in that: In step S3, the micro-nano plastic molecule suspensions are polyvinyl fluoride PS suspension, polyethylene PE suspension, polypropylene PP suspension, and mixed suspension, and the mixed suspension is prepared by mixing polyvinyl fluoride PS, polyethylene PE, and polypropylene PP in a designed proportion.
5. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 4, characterized in that: Four polyvinyl fluoride PS plastic molecular sizes of 100nm, 500nm, 1um and 4um are used to prepare four polyvinyl fluoride PS suspensions with the same concentration but different plastic molecular sizes. A polyethylene PE or polypropylene PP plastic molecular size of 500nm is used to prepare the corresponding polyethylene PE suspension or polypropylene PP suspension. Polyvinyl fluoride PS, polyethylene PE and polypropylene PP with a plastic molecular size of 500nm are mixed in ratios of 1:1:1, 10:1:1, 100:1:1, 100:10:1 and 100:1:10 to prepare five mixed suspensions with the same concentration but different mixing ratios.
6. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 4, characterized in that: In step S3, during the surface enhanced Raman spectroscopy detection and collection process, the parameters are selected as a 50× objective lens and the collection wavelength range is 550cm -1 ~1800cm -1 The acquisition time was 10 s, and all Raman spectra were baseline corrected.
7. The SERS-optimized algorithm detection method for nanoplastics using a silver nanowire network structure according to claim 1, characterized in that: In the step S1, the preparation steps of the silver nanowire crude product are as follows: measure 50mL of ethylene glycol, slowly add 1.86g of polyethylene PE pyrrolidone under stirring to prevent it from condensing into lumps, until the mixed system is evenly dissolved, then measure 50mL of ethylene glycol to rinse the beaker, and pour all the mixed solution into a three-necked flask, drop 1mL of a certain concentration of chloride control agent prepared, and heat the reaction in an oil bath at 160°C for 1h, then completely cover the beaker with tin foil, weigh 0.5g of AgNO3 solid, and stir it into a uniform solution with 25mL of ethylene glycol, and after stirring, use a peristaltic pump to drop it into the three-necked flask at a speed of 75mL / h, continue heating and reacting for 1.5h, and air cool the gray-green oily liquid obtained by the reaction to room temperature, then transfer it to a centrifuge tube, add anhydrous ethanol and perform multiple centrifugal washings.