A long-term monitoring method and device for water pollutants based on SERS technology

Abstract

The present invention relates to a long-term monitoring method and device for water pollutants based on SERS technology. This method can simply, accurately and low-costly monitor the situation of water pollutants in the long term, and at the same time avoid the problem of inaccurate monitoring caused by signal saturation or disappearance. In addition, by controlling the roller speed of the device, the pollutant monitoring concentration range can also be adjusted, making it more flexible and accurate. Generally speaking, this method has the advantages of simplicity, accuracy, wide monitoring range and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of water quality detection, and particularly relates to a long-term monitoring device for water pollutants based on SERS technology. Background Art

[0002] With the geometric growth of the population, the prosperous development of industry and the rapid production of agriculture, water pollution is becoming increasingly serious. Every year, about more than 420 billion m 3 (cubic meters) of sewage is discharged into rivers, lakes and seas, polluting 5.5 trillion m 3 of fresh water, which is more than 14% of the total global runoff. The World Health Organization has announced the top ten killers threatening human health, and water pollution ranks among them. According to statistics, more than 1 billion people globally do not have access to safe drinking water, and about more than 25 million people die each year from drinking unclean water, with an average of 5,000 children dying every day from diseases caused by water pollutants. Illegal discharge of harmful substances (pesticides, heavy metals, antibiotics, organic dyes, residual chlorine, etc.) is one of the main reasons for the rapid deterioration of water quality. Therefore, it is urgent to develop methods for long-term and effective monitoring of water pollution to prevent illegal discharges.

[0003] Surface Enhanced Raman Spectroscopy (SERS) technology can provide molecular-level information that is not easily obtained by other detection technologies, and has the advantages of short detection time, low water interference, direct in-situ analysis, high sensitivity and wide detection range, and is widely used in many fields such as analytical detection and environmental pollution monitoring. The current steps for detecting water pollutants by SERS technology are generally: taking a water sample to be tested and mixing it with a surface-enhanced Raman substrate to amplify the Raman signal of water pollutants, and then testing with a portable Raman instrument to confirm the information of water pollutants. Therefore, if long-term monitoring of water pollutants is to be achieved, continuous sampling must be carried out, making the operation process complex and difficult to implement. In recent years, researchers have developed lightweight SERS substrates that can float on the water surface to reduce the steps of frequent sampling. However, due to long-term floating, the signals on the SERS substrate are prone to saturation or complete disappearance, making it difficult to achieve long-term, effective and accurate monitoring. In addition, the concentration range of pollutants that can be monitored by this method is narrow, which is inconvenient in actual monitoring.

[0004] Therefore, it is necessary to provide a long-term monitoring device for water pollutants that is simple, fast, accurate, low-cost and has a wide monitoring range. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a long-term monitoring device for water pollutants that is simple, fast, accurate, low-cost and has a wide monitoring range.

[0006] To this end, the present invention provides a device for long-term monitoring of water pollutants based on SERS technology, characterized in that the device includes a motor (1), a roller (2), a flexible surface-enhanced Raman substrate film (3), a switch (4), a roller direction button (5), a roller speed adjustment button (6), an outer frame (7), and a filter screen (8). The motor can also be replaced with an electrode and a synchronous belt to prevent the roller from slipping. The motor is preferably a micro-motor. The power supply is preferably a button battery or a combination of solar energy and a storage battery.

[0007] In some embodiments of the present invention, the method for long-term monitoring of water pollutants includes the following steps: placing a Raman sensor in the water body to be monitored, allowing the pollutants to target-act with the surface-enhanced Raman substrate in the sensor, collecting the intensity and peak shape changes of the Raman signal peaks on the surface-enhanced Raman substrate after the action, and comparing them with the pollutant signal standard curve drawn under the same conditions to calculate the pollutant concentrations at different time points in the monitored water body, thereby achieving long-term monitoring of pollutants; the Raman sensor is a roller device that can float on the water surface, with a flexible surface-enhanced Raman substrate wound on the roller, and a partial area of the surface-enhanced Raman substrate is in contact with the water body to be monitored. As the roller rotates, the contact area between the substrate and the water sample to be monitored changes over time.

[0008] In some embodiments of the present invention, the entire sensor floats on the water surface, the bottom of the sensor is in contact with the water surface, there is an opening at the bottom of the sensor, and there is a roller at the opening. There is a flexible surface-enhanced Raman substrate film on the roller, and the flexible surface-enhanced Raman substrate film on the roller is in contact with the water body to be monitored, and the contact surface with the water surface is the side of the Raman-active nanoparticle assembly layer.

[0009] In some embodiments of the present invention, the flexible surface-enhanced Raman substrate is a film including a Raman-active nanoparticle assembly layer and a polymer support layer; the polymer semi-wraps the nanoparticles; the Raman-active nanoparticle assembly layer is semi-embedded in the polymer; the thickness of the Raman-active nanoparticle assembly layer is 40 - 100 nm; the thickness of the polymer support layer is 10 - 200 μm.

[0010] In some embodiments of the present invention, pollutant targeting molecules are modified on the flexible surface-enhanced Raman substrate, and the targeting molecules are at least one of 4-aminothiophenol, 4-nitrothiophenol, 4-mercaptopyridine, cysteine, glutathione, thiuram, mercapto cyclodextrin, and molecular imprinting; the specific modification method is to divide the areas along the short side direction of the substrate film, and different targeting molecules can be modified in each area.

[0011] In some embodiments of the present invention, the specific monitoring method is as follows: First, a series of pollutant solutions with known concentrations are detected, and then a standard curve of pollutant signals is plotted. Then, under the same conditions, the water body monitoring results are compared with the plotted standard curve to obtain the types and concentration information of pollutants in the monitored water body.

[0012] In some embodiments of the present invention, the flexible surface-enhanced Raman substrate film can be cleaned to reduce the background signal and can be recycled; the cleaning method is at least one of soaking with a cleaning solution, rinsing, and ultrasonic cleaning; the cleaning solution is at least one of NaBH4, ethanol, and water.

[0013] In some embodiments of the present invention, the Raman active particles in the flexible surface-enhanced Raman substrate are preferably nanogold, nanosilver, and nanocopper; the polymers are preferably polyurethane, rubber, cellulose, polyvinyl chloride, and polystyrene.

[0014] In some embodiments of the present invention, the flexible surface-enhanced Raman substrate film is prepared by liquid-liquid interface, gas-liquid interface, and liquid-solid interface methods.

[0015] In some embodiments of the present invention, the outer frame material of the sensor includes hollow plastics, wood, and metals; the upper surface and side surfaces of the outer frame are coated with a light-proof coating, and the lower surface is coated with a waterproof and hydrophobic coating; the sensor contains a light material to improve the water surface floating ability of the entire device; the mass density of the light material is less than 1 g / cm 3 。

[0016] In some embodiments of the present invention, solar panels and storage batteries are attached to the upper surface and side surfaces of the outer frame and are connected to electrodes or motors through wires to absorb solar energy as power.

[0017] In some embodiments of the present invention, at the bottom of the sensor, at the part where the surface-enhanced Raman substrate contacts the water surface, there is an ultra-fine filter that can filter out particulate matter, algae, suspended matter, and microorganisms in the water; the ultra-fine filter is made of polytetrafluoroethylene, stainless steel, plexiglass, polyvinylidene fluoride, cellulose, or ceramic.

[0018] In some preferred embodiments of the present invention, by adjusting the direction and speed of the roller, the retraction and release of the surface-enhanced Raman substrate film and the contact time with the water body can be controlled; the roller speed is 0.1 mm / hour to 1 m / hour; when the pollutant concentration is low, the roller speed is slowed down to 0.1 mm / hour to 1 cm / hour, and when the pollutant concentration is high, the roller speed is increased to 1 cm / hour to 1 m / hour; the roller direction is forward when monitoring and backward when collecting the substrate signal.

[0019] In some preferred embodiments of the present invention, pollutant targeting molecules are modified on the flexible surface-enhanced Raman substrate film. The targeting molecules are at least one of 4-aminothiophenol, 4-nitrothiophenol, 4-mercaptopyridine, thiuram, cysteine, and glutathione. When encountering pollutants containing strong oxidizing substances (such as residual chlorine, etc.) or strong reducing substances (such as NaBH4, etc.), the Raman signal intensity of the targeting molecules modified on the surface-enhanced Raman substrate film will be significantly reduced. At the same time, the concentration of pollutants can be judged according to the degree of reduction.

[0020] In some preferred embodiments of the present invention, pollutant targeting molecules are modified on the flexible surface-enhanced Raman substrate film. The targeting molecule is mercapto-cyclodextrin. When encountering hydrophobic pollutants (such as antibiotics, etc.), the Raman signal of the antibiotic on the surface-enhanced Raman substrate film will be significantly enhanced. At the same time, the concentration of pollutants can be judged according to the increased degree.

[0021] In some preferred embodiments of the present invention, 4-mercaptopyridine is modified on the flexible surface-enhanced Raman substrate film. When encountering inorganic mercury or organic mercury, the Raman characteristic peak of 4-mercaptopyridine will change. According to the change of the characteristic peak shape and intensity, the mercury pollution situation in water can be judged.

[0022] In some preferred embodiments of the present invention, pollutant targeting molecules are modified on the flexible surface-enhanced Raman substrate film. The targeting molecule is a molecular imprinting for a specific pollutant. When encountering a specific pollutant, the molecular imprinting layer will adsorb the pollutant, and the Raman signal of the pollutant on the surface-enhanced Raman substrate film will be significantly enhanced. At the same time, the concentration of pollutants can be judged according to the increased degree.

[0023] In some preferred embodiments of the present invention, no modification is made on the flexible surface-enhanced Raman substrate film. The film itself can adsorb and enrich pollutants (such as thiram). When encountering pollutants with a strong binding ability to the film, the pollutants will be enriched on the film surface, and the Raman signal of the pollutants on the surface-enhanced Raman substrate film will be significantly enhanced. At the same time, the concentration of pollutants can be judged according to the increased degree.

[0024] The beneficial effects of the present invention are as follows: 1. The method and device of the present invention are very portable, simple to operate, and low in cost. 2. This device is very small and easy to be placed in the water area to be monitored in the wild. 3. The surface-enhanced Raman substrate film can be modified in different regions to achieve simultaneous monitoring of multiple pollutants. 4. Through simple cleaning, the surface-enhanced Raman substrate film can be recycled, further reducing the cost. 5. The present invention can effectively prevent the problem that pollutants cannot be accurately detected after being diluted by water bodies after being discharged. 6. By adjusting the rotation speed of the roller, the part of the surface-enhanced Raman substrate in contact with the water surface changes over time, so that different parts of the substrate reflect the water quality of the water area to be monitored at different times. 7. According to the concentration of pollutants in the water sample to be measured, adjust the speed of the roller, control the contact time between the surface-enhanced Raman substrate and the water sample to be measured, improve the response sensitivity of the substrate to pollutants, and broaden the response range to pollutants (for example, when the concentration of pollutants is low, extend the contact time, enhance the signal value, and improve the sensitivity; when the concentration of pollutants is high, reduce the contact time, reduce the signal value, and prevent the signal from exceeding the threshold). 8. The device of the present invention can always float on the water sample to be measured to achieve continuous monitoring without frequent sampling. 9. The present invention solves the disadvantages of signal saturation or complete disappearance of pollutants during the monitoring process, and the monitoring is more accurate. Description of the Drawings

[0025] The present invention will be further described below with reference to the drawings.

[0026] Figure 1 It is a long-term monitoring device for water pollutants based on SERS technology.

[0027] Figure 2 It is a scanning electron microscope image of the surface-enhanced Raman substrate film (AuNPs / PU film).

[0028] Figure 3 It is a scanning electron microscope image of the surface-enhanced Raman substrate film (AgNPs / PVC+PU film).

[0029] Figure 4 It is a scanning electron microscope image of the surface-enhanced Raman substrate film (AgNPs / PU film).

[0030] Figure 5 It is a schematic diagram of the modification of the surface-enhanced Raman substrate film.

[0031] Figure 6 For the 1080 cm of 4-aminothiophenol on the AuNPs / PU film under the monitoring device -1 The characteristic peak intensity changes with time.

[0032] Figure 7 For the 1080 cm of 4-aminothiophenol on the AuNPs / PU film -1 The characteristic peak intensity changes with time.

[0033] Figure 8 For different Hg 2+ concentrations, the normalized Raman characteristic peak intensity diagram of 4-mercaptopyridine on the AuNPs / PVC film. Detailed implementation mode

[0034] Example

[0035] To make the present invention easier to understand, the present invention will be further described in detail below in conjunction with examples. These examples are only illustrative and are not limited to the application scope of the present invention. The raw materials or components used in the present invention can be obtained through commercial channels or conventional methods without special instructions.

[0036] Example 1: A long-term monitoring device for water pollutants based on SERS technology

[0037] A long-term monitoring device for water pollutants based on SERS technology of the present invention includes the following parts: a motor (1), a roller (2), a flexible surface-enhanced Raman substrate film (3), a switch (4), a roller direction button (5), a roller speed adjustment button (6), an outer frame (7), and a filter screen (8). In addition, solar panels and storage batteries can be attached to the upper surface and side of the outer frame of the device, and are connected to electrodes or motors through wires to absorb solar energy as power; small holes can be provided on the side of the device, and when the substrate film is not taken out, in cooperation with the reverse rotation of the roller, Raman signals on the substrate film can be directly collected through the small holes.

[0038] Example 2: Preparation of surface-enhanced Raman substrate film (AuNPs / PU film)

[0039] Construct an oil / water two-phase system, with the lower layer being a gold nanoparticle hydrosol (AuNPs) and the upper layer being a cyclohexanone solution of polyurethane (PU); add NaOH to adjust the pH of the AuNPs solution to above 9; gently stir to make the AuNPs float to the interface and perform self-assembly; wait until the cyclohexanone has completely volatilized, and the PU forms a film at the interface, fixing the AuNPs assembled at the interface; take out the PU film with the AuNPs assembled structure obtained at the interface to obtain the surface-enhanced Raman substrate film (AuNPs / PU film). The thickness of the AuNPs / PU film is 150 um, where the thickness of the AuNPs self-assembled layer is 100 nm; the thickness of the PU support layer is 150 um. The electron micrograph of the surface-enhanced Raman substrate material AuNPs / PU film is as Figure 2 shown.

[0040] Example 3: Preparation of surface-enhanced Raman substrate film (AuNPs / PVC film)

[0041] Construct an oil / water two-phase system, with the lower layer being a gold nanoparticle hydrogel (AuNPs) and the upper layer being a cyclohexanone solution of polyvinyl chloride (PVC); gently stir to make the AuNPs float to the interface and self-assemble; wait until the cyclohexanone has completely evaporated, and the PVC forms a film at the interface, fixing the AuNPs assembled at the interface; take out the PVC film with the AuNPs assembled structure embedded at the interface to obtain a surface-enhanced Raman substrate film (AuNPs / PVC film). The electron micrograph of the surface-enhanced Raman substrate material AuNPs / PVC film is as shown in Figure 3 shown.

[0042] Example 4: Preparation of a surface-enhanced Raman substrate film (AgNPs / PU + PVC film) Construct an oil / water two-phase system, with the lower layer being a silver nanoparticle hydrogel (AgNPs) and the upper layer being a cyclohexanone solution of polyurethane (PU) and polyvinyl chloride (PVC); gently stir to make the AgNPs float to the interface and self-assemble; wait until the cyclohexanone has completely evaporated, and the PU + PVC forms a film at the interface, fixing the AgNPs assembled at the interface; take out the PU film with the AgNPs assembled structure embedded at the interface to obtain a surface-enhanced Raman substrate film (AgNPs / PU + PVC film). The thickness of the AgNPs / PU + PVC film is 200 μm, and the thickness of the AgNPs self-assembled layer is 150 nm.

[0043] Example 5: Preparation of a surface-enhanced Raman substrate film (AuNPs / PU film)

[0044] Construct an oil / water two-phase system, with the lower layer being a HAuCl4 hydrogel with pH = 7 and the upper layer being a cyclohexanone solution; stir to promote the reduction of HAuCl4 by cyclohexanone to AuNPs and float them to the interface for self-assembly; then add a high-concentration PU cyclohexanone solution to the upper-layer cyclohexanone solution; wait until the cyclohexanone has completely evaporated, and the PU forms a film at the interface, fixing the AuNPs assembled at the interface; take out the PU film with the AuNPs assembled structure embedded at the interface to obtain a surface-enhanced Raman substrate film (AuNPs / PU film). The electron micrograph of the surface-enhanced Raman substrate material AuNPs / PU film is as shown in Figure 4 shown, where the AuNPs are a heterogeneous structure of composite large and small spheres.

[0045] Example 6: Cyclodextrin-modified AuNPs / PU film

[0046] Take ultrapure water, purge with N2 to remove O2, and prepare a 1 mM mercapto-cyclodextrin solution. Immerse the AuNPs / PU film prepared in Example 1 in the mercapto-cyclodextrin solution for 0.5 h, take out the AuNPs / PU film and wash it successively with ethanol and water to obtain a cyclodextrin-functionalized AuNPs / PU film.

[0047] Example 7: 4-Mercaptopyridine Modified AuNPs / PU Membrane

[0048] Take ultrapure water and prepare a 1 μM 4-mercaptopyridine solution. Immerse the AuNPs / PU membrane prepared in Example 1 in the 4-mercaptopyridine solution for 0.5 h. Take out the AuNPs / PU membrane and wash it successively with ethanol and water to obtain a 4-mercaptopyridine-functionalized AuNPs / PU membrane.

[0049] Example 8: 4-Aminothiophenol Modified AuNPs / PU Membrane

[0050] Take ultrapure water and prepare a 1 μM 4-aminothiophenol solution. Immerse the AuNPs / PU membrane prepared in Example 1 in the 4-aminothiophenol solution for 0.5 h. Take out the AuNPs / PU membrane and wash it successively with ethanol and water to obtain a 4-aminothiophenol-functionalized AuNPs / PU membrane.

[0051] Example 9: Molecularly Imprinted Modified AuNPs / PVC Membrane

[0052] Immerse the AuNPs / PVC membrane prepared in Example 3 in the molecular imprinting precursor. By applying a voltage to the AuNPs / PVC membrane, the molecular imprinting precursor monomer is electro-polymerized on the surface of the AuNPs / PVC membrane to form molecular imprinting. Apply a higher voltage to remove the template molecules to obtain a molecularly imprinted-functionalized AuNPs / PVC membrane.

[0053] Example 10: Multiply Modified AuNPs / PVC Membrane

[0054] Fold the prepared AuNPs / PU membrane to form 5 regions. Float the first region of the AuNPs / PU membrane in the system for forming molecular imprinting. Take out the thin film and wash it to remove the template molecules to form a very thin molecular imprinting layer on the surface of the first membrane region; float the second region of the thin film in the mercapto-cyclodextrin solution to form a layer of cyclodextrin molecules; float the fourth region of the thin film in the 4-aminothiophenol solution to form a layer of 4-aminothiophenol solution molecules; float the fifth region of the thin film in the 4-mercaptopyridine solution to form a layer of 4-mercaptopyridine molecules; do not make any modification to the third region of the thin film for use as a control; as shown Figure 5 as shown

[0055] Example 11: Monitoring the Free Chlorine Pollution in Water by Using a Device

[0056] Apply the 4-aminothiophenol-modified AuNPs / PU membrane prepared in Example 8 to the sensor. Place the sensor in the simulated flowing water sample to be detected and add free chlorine at different concentrations at different times. With 4-aminothiophenol at 1080 cm -1Taking the characteristic peak intensity as the measurement object, according to the attenuation amplitude of this peak intensity, comparing with the standard curve, calculate the free chlorine concentration during the monitoring period. Figure 6 In the simulated flowing water body, after adding free chlorine at different time points, the change diagram of the characteristic peak intensity of 4-aminothiophenol at 1080 cm -1 Characteristic peak intensity.

[0057] Example 12: Using AuNPs / PU membrane to monitor the pollution situation of free chlorine in water.

[0058] Directly place the 4-aminothiophenol-modified AuNPs / PU membrane prepared in Example 8 into the flowing water sample to be detected in Example 11. Taking the characteristic peak intensity of 4-aminothiophenol at 1080 cm -1 as the measurement object, according to the attenuation amplitude of this peak intensity, comparing with the standard curve, calculate the free chlorine concentration during the monitoring period. Figure 7 In the simulated flowing water body, after adding free chlorine at different time points, the change diagram of the characteristic peak intensity of 4-aminothiophenol at 1080 cm -1 Characteristic peak intensity change diagram. It can be seen from the figure that the intensity of the characteristic peak becomes weaker and weaker and finally disappears. Therefore, this method cannot accurately reflect the pollution situation of the water sample to be monitored in the later stage and has drawbacks.

[0059] Example 13: Using the device to monitor the pollution situation of Hg 2+ ion in water

[0060] Apply the 4-mercaptopyridine-modified AuNPs / PVC membrane prepared in Example 7 to the sensor, and place the sensor on the surface of Hg 2+ solutions with different concentrations. Taking the peak intensity of 4-mercaptopyridine at 1276 cm -1 as the control normalized intensity, and taking the characteristic peak intensity of 4-mercaptopyridine at 777 cm -1 as the measurement object, according to the attenuation amplitude of this peak intensity, comparing with the standard curve, calculate the Hg 2+ concentration. Figure 8 For the normalized diagram of the Raman characteristic peak intensity of 4-mercaptopyridine at different Hg 2+ concentrations.

[0061] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A long-term monitoring method for water pollutants based on SERS technology, comprising the following steps: A Raman sensor is placed in the water body to be monitored. Pollutants in the water body target-interact with the surface-enhanced Raman substrate in the sensor. By the intensity and shape changes of the Raman signal peaks collected on the surface-enhanced Raman substrate after the interaction, the concentration of pollutants in the water is calculated. The Raman sensor is a roller device floating on the water surface. A flexible surface-enhanced Raman substrate is wound on the roller. Part of the surface-enhanced Raman substrate is in contact with the water body to be monitored. By rotating the roller, the contact area between the substrate and the water body to be monitored changes with time. Raman signal data of all areas on the surface-enhanced Raman substrate are collected, which can reflect the situation of pollutants in the water at different time points and realize long-term monitoring of pollutants in the water. The flexible surface-enhanced Raman substrate is a thin film, which includes a Raman-active nanoparticle assembly layer and a polymer support layer. The polymer semi-wraps the Raman-active nanoparticles. The Raman-active nanoparticle assembly layer is semi-embedded in the polymer. The thickness of the Raman-active nanoparticle assembly layer is 40-100 nm. The thickness of the polymer support layer is 10-200 μm. The Raman-active nanoparticles in the flexible surface-enhanced Raman substrate are at least one of nanogold, nanosilver, and nanocopper. The polymer is at least one of polyurethane, rubber, cellulose acetate, polyvinyl chloride, and polystyrene. The flexible surface-enhanced Raman substrate thin film can be repeatedly stretched 0.1-6 times without breaking.

2. A long-term monitoring method for water pollutants based on SERS technology according to claim 1, which is implemented by a Raman sensor, characterized in that The Raman sensor includes a motor (1), a roller (2), a flexible surface-enhanced Raman substrate thin film (3), a switch (4), a roller direction button (5), a roller speed adjustment button (6), an outer frame (7), and a filter screen (8). The motor is a micro-motor, which can be replaced by an electrode and a synchronous belt. The power supply is a button battery or a combination of solar energy and a storage battery. The roller direction button and the roller speed adjustment button can adjust the roller direction and speed, and thus control the winding and unwinding of the surface-enhanced Raman substrate thin film and the contact time with the water body. The roller speed is 0.1 mm / hour to 1 m / hour. The roller direction is forward when monitoring and backward when collecting the substrate signal. The size of the sensor device is less than 10 cm * 10 cm * 20 cm.

3. The long-term monitoring method for water pollutants based on SERS technology according to claim 2, wherein The whole sensor floats on the water surface. The bottom of the sensor is in contact with the water surface. There is an opening at the bottom of the sensor, and there is a roller at the opening. There is a flexible surface-enhanced Raman substrate thin film on the roller. The flexible surface-enhanced Raman substrate thin film on the roller is in contact with the water body to be monitored, and the side in contact with the water surface is the Raman-active nanoparticle assembly layer side.

4. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, characterized in that Pollutant-targeting molecules are modified on the flexible surface-enhanced Raman substrate thin film. The targeting molecules are at least one of 4-aminothiophenol, 4-nitrothiophenol, 4-mercaptopyridine, cysteine, glutathione, thiuram, mercapto-cyclodextrin, and molecular imprinting. The specific modification method is to divide the area along the short side of the surface-enhanced Raman substrate thin film, and different targeting molecules are modified in each area.

5. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, characterized in that The specific monitoring method is as follows: First, a series of pollutant solutions with known concentrations are detected, and then a standard curve of pollutant signals is plotted. Then, under the same conditions, the water body monitoring results are compared with the plotted standard curve to obtain the types and concentration information of pollutants in the monitored water body.

6. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, characterized in that The flexible surface-enhanced Raman substrate film is prepared by a liquid-liquid interface or a gas-liquid interface or a liquid-solid interface method; the cleaning method is at least one of soaking, rinsing, and ultrasonic cleaning with a cleaning solution; the cleaning solution is at least one of NaBH4, ethanol, and water.

7. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, characterized in that The material of the sensor outer frame includes hollow plastic, wood or metal; the upper surface and the side surface of the outer frame are coated with a light-proof coating, and the lower surface is coated with a waterproof and hydrophobic coating; the sensor contains lightweight materials to improve the water surface floating ability of the entire device; the mass density of the lightweight material is less than 1 g / cm 3 ; at the bottom of the sensor, at the part where the surface-enhanced Raman substrate film contacts the water surface, there is an ultra-fine filter screen that can filter particulate matter, algae, suspended matter, and microorganisms in the water; the material of the ultra-fine filter screen is polytetrafluoroethylene, stainless steel, plexiglass, polyvinylidene fluoride, cellulose, or ceramic.

8. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, wherein a solar panel and a storage battery are attached to the upper surface and the side surface of the outer frame, and are connected to the electrode or the motor through wires to absorb solar energy as power; there is a small hole on the side surface of the outer frame, and the laser can pass through the small hole to collect Raman signals. With the reverse rotation of the roller, Raman signal information at all positions on the flexible surface-enhanced Raman substrate film can be directly obtained.

9. A long-term monitoring method for water pollutants based on SERS technology according to claim 2, characterized in that The speed of the roller is such that when the pollutant concentration is low, the roller speed slows down, from 0.1 mm / hour to 1 cm / hour, and when the pollutant concentration is high, the roller speed is adjusted to be faster, from 1 cm / hour to 1 m / hour.

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