WO2021179347A1 - 一种基于拉曼光谱的水中游离氯的检测方法 - Google Patents

一种基于拉曼光谱的水中游离氯的检测方法 Download PDF

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WO2021179347A1
WO2021179347A1 PCT/CN2020/080815 CN2020080815W WO2021179347A1 WO 2021179347 A1 WO2021179347 A1 WO 2021179347A1 CN 2020080815 W CN2020080815 W CN 2020080815W WO 2021179347 A1 WO2021179347 A1 WO 2021179347A1
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base material
enhanced raman
raman
marker
free chlorine
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PCT/CN2020/080815
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English (en)
French (fr)
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钟鹭斌
郑煜铭
吴鹏
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中国科学院城市环境研究所
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Publication of WO2021179347A1 publication Critical patent/WO2021179347A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons

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  • the invention belongs to the technical field of water quality detection, and specifically relates to a method for detecting free chlorine in water based on Raman spectroscopy.
  • Water is the foundation of life. There is limited fresh water on earth, and its quality is under constant threat. Maintaining the quality of fresh water is very important for the supply of drinking water, food production and recreational water. Infectious disease agents, toxic chemicals and radioactive hazards can affect water quality. Whether for drinking, household use, food production or recreational use, safe and readily available water is very important to public health. Improved water supply and sanitation, as well as better management of water resources, can boost the country’s economic growth and greatly contribute to poverty reduction.
  • Chlorine disinfection is currently the most widely used in drinking water disinfection process. If the residual chlorine content in the water is insufficient, it will not be able to kill microorganisms and pathogens in the water. If the residual chlorine content in the water is too high, it will affect the taste of the water and seriously cause a series of diseases such as human respiratory problems.
  • Existing free chlorine detection methods include iodometry, colorimetry, spectrophotometry, chemiluminescence, fluorescence quenching, electrochemistry, chromatography, etc.
  • the iodometric method is based on the reaction of residual chlorine and potassium iodide to produce quantitative iodine in an acidic solution environment.
  • the residual chlorine content is determined by titration with sodium thiosulfate standard solution.
  • Electrochemical methods include redox potential method and current method.
  • the redox potential method requires a redox electrode and a reference electrode. The potential balance is achieved by gaining and losing electrons in the reaction, and is generally only used for qualitative detection. During use, the electrode is easily covered by organic particles and needs to be cleaned frequently, and this method is susceptible to the influence of pH and needs to be calibrated regularly.
  • the current method generally includes a working electrode, a counter electrode, an electrolyte, and a microporous hydrophobic membrane.
  • HClO mainly exists in the form of ClO - , which has a greater impact on the measurement results.
  • fluorescence spectroscopy has high sensitivity, it is very inconvenient to avoid light during the whole operation.
  • Graphene oxide quantum dots (GQDs), carbon dots, ZnO quantum dots (ZnO QDs), etc. are commonly used luminescent substances in the fluorescence method.
  • the fluorescence method has the advantages of low detection limit, high sensitivity and rapid response, but it also has many shortcomings. Fluorometers are expensive, bulky, not suitable for on-site rapid detection, and difficult to regenerate. The material preparation process often needs to be separated and purified by column chromatography. Although a portable gel material has been prepared, rapid detection cannot be achieved.
  • SERS Surface-Enhanced Raman Scattering
  • the present invention provides a method for detecting free chlorine in water based on Raman spectroscopy.
  • the method is simple, fast, accurate, low interference, reproducible, low cost, high sensitivity, long-term monitoring, etc. advantage.
  • the present invention provides a method for detecting free chlorine in water based on Raman spectroscopy, which includes the following steps:
  • step S2 modifying the surface-enhanced Raman base material obtained in step S1 to obtain a surface-enhanced Raman base material with a marker;
  • step S3 using the surface-enhanced Raman substrate material with the marker obtained in step S2 to detect a series of sodium hypochlorite standard solutions of known concentration, and then draw a standard curve for free chlorine detection;
  • step S4 using the surface-enhanced Raman substrate material with markers obtained in step S2 to detect free chlorine in the water sample to be tested, and compare the detection result with the standard curve drawn in step S3 to obtain the water sample to be tested The concentration of free chlorine in.
  • step S1 the specific operation of step S1 is: adding an organic solution containing a high molecular polymer above the nanoparticle solution, and then the nanoparticle floats to the oil/water interface, and performs self-assembly; After the organic solvent is completely volatilized, the polymer forms a film at the interface to fix the assembled nanoparticles at the interface; the polymer film with the embedded nanoparticle assembly structure obtained at the interface is taken out to obtain a surface-enhanced Raman substrate Material.
  • the thickness of the surface-enhanced Raman base material is 10-300um.
  • the surface-enhanced Raman base material includes two layers, one of which is a nanoparticle self-assembled layer with a thickness of 20-300 nm, and the other layer is a polymer support layer with a thickness It is 10-300um; further preferably, the high molecular polymer support layer half wraps the nanoparticle self-assembly layer.
  • the nanoparticles are selected from at least one of gold, silver, copper, platinum, and alloys thereof.
  • the particle size of the nanoparticles is selected from 10 to 100 nm, preferably from 40 to 60 nm.
  • the high molecular polymer is preferably at least one of polyvinyl chloride, polyvinyl acetate, polystyrene, polyurethane, and polymethyl methacrylate.
  • the organic solvent is selected from at least one of cyclohexanone, ethyl acetate, toluene, and cycloethane.
  • step S2 the specific operation of step S2 is: immersing the surface-enhanced Raman base material prepared in step S1 in a marker solution, and then cleaning, to obtain a surface-enhanced Raman base material with markers .
  • the soaking time is 10-30 minutes.
  • the label in step S2, can react with free chlorine; preferably, the label is selected from 4-aminothiophenol and 4-nitrothiophenol , At least one of 4-mercaptopyridine, cysteine, glutathione and thiuram.
  • step S3 the specific operation of step S3 is: float the surface-enhanced Raman base material with the marker on the surface of a series of sodium hypochlorite standard solutions of known concentration, and then use a Raman spectrometer to detect the surface of the sodium hypochlorite standard solution.
  • the floating surface with the marker enhances the characteristic Raman signal peak of the marker on the Raman base material, and then draws a standard curve of the Raman signal peak-free chlorine concentration.
  • the concentration of the series of sodium hypochlorite standard solutions is 0 to 10.0 ppm.
  • the floating time is 1-10 minutes.
  • the specific operation of step S4 is: float the surface-enhanced Raman base material with the marker on the surface of the water sample to be tested, and then use the Raman spectrometer to detect the floating surface of the water sample.
  • the characteristic Raman signal peak value of the marker on the surface-enhanced Raman substrate material with the marker, and the detected Raman signal peak value is compared with the standard curve drawn in step S3 to obtain the concentration of free chlorine in the water sample to be tested ;
  • the floating time of the surface-enhanced Raman base material with markers in the water sample to be tested is the same as the floating time in the sodium hypochlorite standard solution.
  • the water being tested does not contain the H 2 O 2, O 3, Cr 2 O 7 2- and MnO 4 -.
  • the detection limit of the method is 0.01 ppm.
  • the floating time of the surface-enhanced Raman base material with the marker on the surface of the water sample to be tested in step S4 is extended, and the characteristic Raman signal peak value of the marker on the Raman base material is detected. Change, to achieve long-term monitoring of the water sample to be tested. That is, the free chlorine in the water sample during the floating time of the surface enhanced Raman base material can be monitored.
  • the base material used in the method of the present invention is simple to prepare, low in cost, light in weight, floatable, easy to carry, fast in detection and high in sensitivity, and is suitable for various extreme environments (high temperature, strong acid, Strong alkali) has good use effect and can be reused.
  • high temperature, strong acid, Strong alkali high temperature, strong acid, Strong alkali
  • Raman spectrometer With the help of a portable Raman spectrometer, on-site detection can be realized, and there is no need to tediously prepare a solution during the detection process, and the operation is convenient.
  • the substrate material can be floated on the surface of the water sample to be tested for in-situ testing (at the same time long-term monitoring can be achieved), or the substrate material can be removed from the water sample to be tested for testing, reducing the water environment (such as water turbidity) for testing The impact of results.
  • the method of the present invention has the advantages of simplicity, speed, accuracy, low interference, reproducibility, low cost, high sensitivity, long-term monitoring and the like.
  • Figure 1 is a schematic diagram of the AuNPs/PVC membrane preparation and detection principle.
  • Figure 2 is an electron micrograph of AuNPs/PVC film.
  • Figure 3 is an electron microscope image of a cross-section of the AuNPs/PVC film.
  • Figure 4 shows the Raman spectra of AuNPs/PVC films with 4-ATP immersed in different concentrations of sodium hypochlorite standard solutions.
  • Figure 5 is a graph showing the relationship between the concentration of sodium hypochlorite and the integral of the Raman peak area of 4-ATP.
  • Figure 6 is a graph showing the influence of different interfering ions on the process of detecting sodium hypochlorite solution on AuNPs/PVC membrane with 4-ATP.
  • FIG. 7 is a Raman spectrum chart of Example 5.
  • the present invention adopts surface enhanced Raman scattering (SERS) technology to detect free residual chlorine in water.
  • SERS surface enhanced Raman scattering
  • the invention prepares a novel SERS base material, and the base material is modified with a marker capable of reacting with free residual chlorine.
  • the free residual chlorine will react with the markers, causing the markers to fall off the SERS base material, and then by measuring the degree of reduction in the Raman signal of the markers on the SERS base material, and comparing it with the standard curve, you can Calculate the concentration of free residual chlorine in the water sample to be tested.
  • the base material When using SERS detection, the base material can be floated on the surface of the water sample to be tested for in-situ detection, and the base material can be taken out of the water sample to be tested, so that it will not be interfered by other substances such as water turbidity.
  • the method of the present invention collects the Raman spectra of the markers, which has molecular fingerprint specificity, has less interference and lower errors than other methods.
  • the SERS technology has a fast detection speed, Raman signals can be obtained in a few seconds, and the SERS base material can be simply regenerated for use, effectively reducing costs.
  • the SERS substrate material is flexible and ultra-light SERS substrate material
  • the SERS substrate can be floated on the water surface to monitor whether there is free residual chlorine discharge during the time period, which can effectively prevent excessive residual chlorine discharge. After being diluted by the water, it cannot The problem of accurate detection.
  • the method for detecting free chlorine in water based on Raman spectroscopy includes the following steps:
  • step S2 modifying the surface-enhanced Raman base material obtained in step S1 to obtain a surface-enhanced Raman base material with a marker;
  • step S3 using the surface-enhanced Raman substrate material with the marker obtained in step S2 to detect a series of sodium hypochlorite standard solutions of known concentration, and then draw a standard curve for free chlorine detection;
  • step S4 using the surface-enhanced Raman substrate material with markers obtained in step S2 to detect free chlorine in the water sample to be tested, and compare the detection result with the standard curve drawn in step S3 to obtain the water sample to be tested The concentration of free chlorine in.
  • the surface-enhanced Raman base material can be prepared by a liquid-liquid interface self-assembly method, specifically: adding an organic solution containing a high molecular polymer on top of the nanoparticle solution, and then the nanoparticle Float to the oil/water interface and perform self-assembly; after the added organic solvent is completely volatilized, the polymer forms a thin film at the interface to fix the assembled nanoparticles at the interface; the embedded nanoparticles obtained at the interface The polymer film of the assembled structure is taken out to obtain the surface-enhanced Raman base material.
  • the surface-enhanced Raman base material is an ultra-thin, light-weight, flexible and semi-transparent film.
  • the thickness of the surface-enhanced Raman base material may be 10-300um.
  • the surface-enhanced Raman base material includes two layers, one of which is a nanoparticle self-assembled layer with a thickness of 20-300 nm, and the other is a high molecular polymer support layer,
  • the thickness can be 10-300um; further preferably, the high molecular polymer support layer half wraps the nanoparticle self-assembly layer, that is, the nanoparticle self-assembly structure is half embedded in the high molecular polymer film, and part of The nanoparticle self-assembled structure is partially exposed.
  • the surface-enhanced Raman base material can remove excess high molecular polymer on the nanoparticle self-assembly layer by plasma technology, and further can control the wrapping state of the nanoparticle self-assembly layer by the high molecular polymer support layer.
  • the prepared surface-enhanced Raman substrate material Due to the local surface plasmon resonance (LSPR), the prepared surface-enhanced Raman substrate material has a significant enhancement effect on signal molecules under the test of the Raman spectrometer.
  • LSPR local surface plasmon resonance
  • the preparation method of the surface-enhanced Raman base material is not limited to the above-mentioned liquid-liquid interface, and can also be prepared by a gas-liquid interface method or a liquid-solid interface method.
  • the nanoparticles are selected from at least one of gold, silver, copper, platinum, and alloys thereof.
  • the nanoparticles used in the present invention can also be replaced by other nanoparticles with localized surface plasmon resonance (LSPR).
  • LSPR localized surface plasmon resonance
  • the selected nanoparticles are silver, the obtained surface-enhanced Raman base material has a stronger Raman signal, but silver is easy to oxidize. Therefore, when the selected nanoparticles are silver, the obtained surface-enhanced Raman base material Then soak it in a solution such as HAuCl 4 to coat it with gold to improve its antioxidant capacity.
  • the particle size of the nanoparticles is selected from 10-100 nm, preferably selected from 40-60 nm; most preferably 50 nm.
  • the high molecular polymer is preferably at least one of polyvinyl chloride, polyvinyl acetate, polyurethane, polystyrene, and polymethyl methacrylate.
  • the high molecular polymer selected in the present invention is not limited to the above materials, the selected high molecular polymer can also be polydimethylsiloxane, polypropylene, polycarbonate, acrylonitrile-butadiene-styrene copolymer (ABS resin), chlorohydrin rubber, nitrocellulose.
  • the organic solvent is selected from at least one of cyclohexanone, ethyl acetate, toluene, and cycloethane.
  • step S2 the specific operation of step S2 is: immersing the surface-enhanced Raman substrate material prepared in step S1 in a marker solution, and then cleaning, to obtain a surface-enhanced Raman substrate with a marker Material.
  • the soaking time is 10-30 minutes.
  • the label in step S2, can react with free chlorine.
  • the reaction is that the label forms a metal-S bond (such as Au-S) with the Raman substrate, which is In the presence of chlorine, Au-S is broken, which in turn causes the marker to fall off the SERS base material;
  • the marker is selected from 4-aminothiophenol, 4-nitrothiophenol, and 4-mercaptopyridine , At least one of cysteine, glutathione and thiuram.
  • step S3 the specific operation of step S3 is: float the surface-enhanced Raman substrate material with the marker on the surface of a series of sodium hypochlorite standard solutions of known concentration, and then use a Raman spectrometer to detect the surface of the sodium hypochlorite standard solution After the surface floats, the surface with the marker enhances the characteristic Raman signal peak of the marker on the Raman base material, and then draws a standard curve of the Raman signal peak-free chlorine concentration.
  • the concentration of the series of sodium hypochlorite standard solutions is 0 to 10.0 ppm. In some specific embodiments of the present invention, the concentration of the sodium hypochlorite standard solution may be 0, 0.05 ppm, 0.3 ppm, 0.5 ppm, 1.0 ppm, 1.5 ppm, 2.0 ppm, 5.0 ppm, 8.0 ppm or 10.0 ppm, etc.
  • the floating time is 1-10 minutes, preferably 3 minutes.
  • the specific operation of step S4 is: float the surface-enhanced Raman base material with the marker on the surface of the water sample to be tested, and then use the Raman spectrometer to detect the floating on the surface of the water sample to be tested
  • the characteristic Raman signal peak value of the marker on the surface-enhanced Raman substrate material with the marker, the detected Raman signal peak value is compared with the standard curve drawn in step S3 to obtain the free chlorine in the water sample to be tested Concentration;
  • the floating time of the surface-enhanced Raman base material with the marker in the water sample to be tested is the same as the floating time in the sodium hypochlorite standard solution.
  • the Raman base material is taken out and cleaned, so as to remove the physical substance in the detected water body.
  • the adsorbed interfering substances improve the accuracy and sensitivity of detection.
  • the water being tested does not contain the H 2 O 2, O 3, Cr 2 O 7 2- and MnO 4 -. Since this method also reacts to strong oxidizing substances such as H 2 O 2 , O 3 , Cr 2 O 7 2- and MnO 4 - , it is necessary to avoid H 2 O 2 , O 3, Cr 2 O 7 2- and MnO 4 - interference strong oxidizing substances, the test sample need not contain water H 2 O 2, O 3, 2 O 7 2- and MnO 4 Cr - and other strong oxidizing substance.
  • the method specifically includes:
  • step (3) Float the surface-enhanced Raman base material with marker prepared in step (2) in a series of sodium hypochlorite standard solutions of known concentration, take out the surface-enhanced Raman base material and clean it, and then use the Raman spectrometer Detecting the characteristic Raman signal peak of the marker on the surface-enhanced Raman substrate material with the marker floating on the surface of the sodium hypochlorite standard solution, and then drawing a standard curve of the Raman signal peak-free chlorine concentration;
  • step (3) Float the surface-enhanced Raman base material with marker prepared in step (2) in the water sample to be tested with unknown residual chlorine concentration for the same time, take out the surface-enhanced Raman base material and clean it, and then use it
  • the Raman spectrometer detects the characteristic Raman signal peaks of the markers on the surface-enhanced Raman substrate material with markers floating on the surface of the water sample to be tested, and compares the detected Raman signal peaks with those in step (3). Comparing the drawn standard curve to obtain the concentration of free residual chlorine in the water sample to be tested.
  • the detection limit of the method is 0.01 ppm.
  • the floating time of the surface-enhanced Raman base material with the marker on the surface of the water sample to be tested in step S4 is extended, and the characteristic Raman signal peak value of the marker on the Raman base material is detected. Change to determine whether there is residual chlorine discharge during the monitoring period, so as to achieve long-term monitoring of the water sample to be tested.
  • the present invention Compared with other residual chlorine emission monitoring methods, the present invention has the following advantages: First, the substrate can always float on the water sample to be tested to achieve continuous monitoring. Once residual chlorine is discharged, it can react with the substrate to accurately monitor the residual chlorine discharge. Without frequent sampling, you can know whether there is any residual chlorine emission during the monitoring period. Secondly, it can effectively prevent the sneak discharge. After the discharge, the water body is diluted and run away, which leads to the shortcomings of insufficient detection.
  • Example 1 Surface-enhanced Raman base material: Preparation of AuNPs/PVC film with 4-ATP
  • PVC polyvinyl chloride
  • the thickness of the AuNPs/PVC film is 110um, and the thickness of the self-assembled layer of gold nanoparticles is 150nm; the thickness of the polyvinyl chloride support layer is 110um.
  • the electron micrographs of the AuNPs/PVC film of the surface-enhanced Raman base material are shown in Figures 2 and 3.
  • the obtained AuNPs/PVC membrane was immersed in 4-aminothiophenol solution (4-ATP) for 20 minutes to obtain AuNPs/PVC membrane with 4-ATP with characteristic Raman signal around 1079 cm -1.
  • Example 3 Detection of the water sample to be tested
  • the AuNPs/PVC membrane with 4-ATP prepared in Example 1 was floated in a 20mL tap water sample for 3 minutes, the floating AuNPs/PVC membrane was taken out and washed, and the Raman spectrometer was used to detect the 4 of the floating AuNPs/PVC membrane. -The signal value of the ATP molecule near the Raman peak of 1079 cm -1 . Compare the detected Raman signal peak with the standard curve drawn in Example 2 to obtain the residual chlorine concentration in the tap water sample, which is 0.06 ppm.
  • Example 4 The influence of interfering ions on detection
  • the AuNPs/PVC membrane with 4-ATP prepared in Example 1 was floated in the sodium hypochlorite solution containing different interfering ions, and the 4-ATP molecules of the AuNPs/PVC membrane floating in the sodium hypochlorite solution of different interfering ions were detected by a Raman spectrometer. At the signal value near the Raman peak at 1079 cm -1 , the effect of different interfering ions on the process of detecting sodium hypochlorite solution on the AuNPs/PVC membrane with 4-ATP prepared in Example 1 was plotted, and the results are shown in FIG. 6. It can be seen from Figure 6 that different interfering ions have little effect on the detection results. It is explained that the method for detecting free chloride ions using the novel surface-enhanced Raman substrate material prepared by the present invention is less affected by the outside world.
  • Example 5 Detection effect of using gold nanoparticle sol as a marker substrate
  • the obtained AgNPs@Au/PU film was immersed in a 4-mercaptopyridine (4-Mpy) solution for 15 minutes to obtain a 4-Mpy AgNPs@Au/PU film with a characteristic Raman signal near 1096 cm -1.
  • the AgNPs@Au/PU membrane was floated on the outlet water surface of the sewage treatment plant for a period of time, and the characteristic peak of 4-MPy disappeared, indicating that there was free chlorine in the water during this period.
  • Example 7 Surface-enhanced Raman base material: Preparation of AuNPs/PVC film with 4-ATP
  • the preparation process is basically the same as in Example 1, the difference is that the amount of gold nanoparticle sol (AuNPs) added and the floating time are changed so that the thickness of the obtained AuNPs/PVC film is 110um, and the thickness of the gold nanoparticle self-assembled layer is 50nm ; The thickness of the PVC support layer is 110um.
  • AuNPs gold nanoparticle sol
  • Example 8 Surface-enhanced Raman base material: Preparation of AuNPs/PVC film with 4-ATP
  • the preparation process is basically the same as in Example 1. The difference is that the particle size, addition amount and floating time of the AuNPs sol (AuNPs) are changed so that the thickness of the AuNPs/PVC film obtained is 110um, and the self-assembly layer of the AuNPs The thickness is 20nm; the thickness of the polyvinyl chloride support layer is 110um.
  • the AuNPs/PVC membranes with 4-ATP prepared in Examples 1, 7 and 8 were used to detect the same series of water samples with different concentrations.
  • the test results showed the lowest detection line of the 4-ATP AuNPs/PVC membranes prepared in Example 1
  • the lowest detection line of the AuNPs/PVC film of 4-ATP prepared in Example 7 was 0.01 ppm
  • the lowest detection line of the AuNPs/PVC film of 4-ATP prepared in Example 8 was 0.05 ppm.
  • the AuNPs/PVC membrane with 4-ATP prepared in Example 1 was floated in the actual water sample containing 0.1ppm sodium hypochlorite, and the Raman spectrometer was used to detect the AuNPs/PVC membrane floating in the sodium hypochlorite water sample with different interfering ions for multiple times. -The signal value of the ATP molecule near the Raman peak at 1079 cm -1 , and its RSD is calculated to be 12.48%. According to the national standard "GB/T 14424-2008 Determination of Residual Chlorine in Industrial Circulating Cooling Water", the 0.01ppm sodium hypochlorite solution was measured. Repeated measurement results showed that its RSD was 43.30%. Compared with the results of Raman spectroscopy, this method has better repeatability in low concentration measurement.

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Abstract

一种基于拉曼光谱的水中游离氯的检测方法，其包括以下步骤：S1，通过界面自组装法制备表面增强拉曼基底材料；S2，对步骤S1制得的表面增强拉曼基底材料进行修饰，获得具有标记物的表面增强拉曼基底材料；S3，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对已知浓度的系列次氯酸钠标准溶液进行检测，进而绘制游离氯检测的标准曲线；S4，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对待测水样中的游离氯进行检测，并将检测结果与步骤S3中绘制的标准曲线进行比较，获得待测水样中游离氯的浓度，具有简单、快速、准确、干扰小、可再生、成本低、检出限低，可长期监测等优点。

Description

一种基于拉曼光谱的水中游离氯的检测方法
相关申请的交叉引用
本申请要求享有于2020年3月10日提交的名称为“一种基于拉曼光谱的水中游离氯的检测方法”的中国专利申请CN202010161006.2的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本发明属于水质检测技术领域，具体涉及一种基于拉曼光谱的水中游离氯的检测方法。
背景技术
水是生命的根本。地球上的淡水有限，而且其质量受到持续的威胁。保持淡水的质量对饮用水的供应、食品生产和娱乐用水十分重要。传染病因子、有毒化学品和放射性危害可影响水的质量。无论是饮用、家庭使用、粮食生产还是娱乐用途，安全和随时可用的水对于公共卫生来说都非常重要。经改善的水供应和环境卫生以及对水资源的更好管理，可以推动国家的经济增长并大力促进减贫。
氯消毒是目前饮用水消毒工艺中使用最广泛的。水中余氯含量不足，则无法杀灭水中的微生物和病原体，水中余氯含量过高，则会影响水的口感，严重会引起人体呼吸道问题等一系列疾病。
现有的游离氯检测方法有碘量法，比色法，分光光度法，化学发光法，荧光淬灭法，电化学法，色谱法等。碘量法是在酸性溶液环境下，根据余氯与碘化钾反应产生定量碘，通过硫代硫酸钠标准溶液进行滴定来实现余氯含量的测定。在国家标准GB/T5750.11—2006《生活饮用水标准检验方法消毒剂指标》中，使用N,N-二乙基对苯二胺(DPD)分光光度法和和3,3’,5,5’-四甲基联苯胺比色法检测水中游离余氯，前者需要配制较多的化学试剂，操作步骤繁琐，分析周期长，测量过程中，显色时间对测量结果影响较大，须严格控制，而后者主要是通过肉眼比色，误差较大，且国标方法对水质有一定要求，对于较浑浊的水样，测量结果准确度较低。目前对于DPD方法虽然在成本控制，检测pH范围，反应时间和保 存运输等方面已有一定改进，但仍然需要使用较多种类的化学试剂。电化学方法包括氧化还原电势法和电流法两种。氧化还原电势法需要氧化还原电极和参比电极，通过在反应中得失电子达到电势平衡，一般只用于定性检测。在使用过程中，电极容易被有机颗粒物覆盖，需要经常清洗，且此方法容易受到pH的影响，需要定期校准。电流法一般包含工作电极，对电极，电解液和微孔疏水膜，根据法拉第电解定律和菲克第一定律，在电极间提供恒定电压，使余氯浓度与电流成线性相关。此法虽然可以实时检测，但测量结果受水流影响较大，且微孔疏水膜只能让HClO选择性透过，在高pH下，HClO主要以ClO -形式存在，对测量结果影响较大。荧光光谱虽然具有较高的灵敏度，但是全程操作需要注意避光，非常不方便。氧化石墨烯量子点(GQDs)、碳点、ZnO量子点(ZnO QDs)等是荧光方法中普遍采用的发光物质，在激发光的作用下，它们会发射一定波长的光。ClO -的强氧化性能够破坏这些物质表面的钝化层或荧光基团的结构，削弱发射光的强度，从而可用于检测水中游离氯的浓度。和上述其他方法相比，荧光方法具有检测限低，灵敏度高，快速反应的优点，但同时也存在许多不足。荧光仪价格贵，体积大，不适宜现场快速检测，难于再生使用。在材料制备过程常常需要经过柱层析色谱分离纯化，虽然已有制备成便携的凝胶材料，但无法实现快速检测。
表面增强拉曼散射(Surface-Enhanced Raman Scattering，SERS)是指当待测物质吸附或贴近于金、银、铜等金属纳米结构表面时，其拉曼信号可以得到百万倍以上的增强。SERS技术由于其无需标记、无需复杂样品预处理、可精准提供分子信息、检测周期短和灵敏度高等特点，在生物检测、食品安全和环境污染物监测方面具有广泛应用。尤其随着拉曼仪器逐渐趋于便携化，使其越来越适合现场快速检测分析。
因此，提供一种简单、快速、准确、干扰小、可再生、成本低、灵敏高的水中游离氯的检测方法非常有必要，尤其还可以实现长期监测。
发明内容
本发明针对现有技术的不足，提供了一种基于拉曼光谱的水中游离氯的检测方法，该方法具有简单、快速、准确、干扰小、可再生、成本低、灵敏高，可长期监测等优点。
为此，本发明提供了一种基于拉曼光谱的水中游离氯的检测方法，其包括以下步骤：
S1，通过界面自组装法制备表面增强拉曼基底材料；
S2，对步骤S1制得的表面增强拉曼基底材料进行修饰，获得具有标记物的表面增强拉曼基底材料；
S3，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对已知浓度的系列次氯酸钠标准溶液进行检测，进而绘制游离氯检测的标准曲线；
S4，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对待测水样中的游离氯进行检测，并将检测结果与步骤S3中绘制的标准曲线进行比较，获得待测水样中游离氯的浓度。
在本发明的一些实施方式中，步骤S1的具体操作为：在纳米粒子溶液的上方加入含有高分子聚合物的有机溶液，然后纳米粒子上浮至油/水界面，并进行自组装；待加入的有机溶剂挥发完全后，高分子聚合物在界面形成薄膜，固定住界面处已组装的纳米粒子；将所述界面处获得的镶嵌纳米粒子组装结构的高分子薄膜取出，即得表面增强拉曼基底材料。
在本发明的一些优选的实施方式中，所述表面增强拉曼基底材料厚度为10～300um。
在本发明进一步优选的实施方式中，所述表面增强拉曼基底材料包括两层，其中一层为纳米粒子自组装层，厚度为20～300nm，另一层为高分子聚合物支撑层，厚度为10～300um；进一步优选地，所述高分子聚合物支撑层半包裹所述纳米粒子自组装层。
在本发明的一些实施方式中，所述纳米粒子选自金、银、铜、铂和它们的合金中的至少一种。
在本发明的一些具体实施方式中，所述纳米粒子的粒径选自10～100nm，优选选自40～60nm。
在本发明的另一些实施方式中，所述高分子聚合物优选自聚氯乙烯、聚乙酸乙烯酯、聚苯乙烯、聚氨酯和聚甲基丙烯酸甲酯中的至少一种。
在本发明的一些实施方式中，所述有机溶剂选自环己酮、乙酸乙酯、甲苯和环乙烷中的至少一种。
在本发明的一些实施方式中，步骤S2的具体操作为：将步骤S1制得的表面增强拉曼基底材料浸泡于标记物溶液中，然后进行清洗，获得具有标记物的表面增强拉曼基底材料。
在本发明的一些优选的实施方式中，所述浸泡的时间为10～30分钟。
在本发明的另一些优选的实施方式中，步骤S2中，所述标记物能与游离氯发生反应；优选地，所述标记物选自4-氨基苯硫酚、4-硝基苯硫酚、4-巯基吡啶、半胱氨酸、谷胱甘肽和秋兰姆中的至少一种。
在本发明的一些实施方式中，步骤S3的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于已知浓度的系列次氯酸钠标准溶液表面，然后使用拉曼光谱仪检测在次氯酸钠标准溶液表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，进而绘制拉曼信号峰值-游离氯浓度的标准曲线。
在本发明的一些优选的实施方式中，所述系列次氯酸钠标准溶液的浓度为0～10.0ppm。
在本发明的另一些优选的实施方式中，所述漂浮的时间为1～10分钟。
在本发明的一些实施方式中，步骤S4的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于待测水样表面，然后使用拉曼光谱仪检测在待测水样表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，将检测的拉曼信号峰值与步骤S3绘制的标准曲线进行比较，获得待测水样中游离氯的浓度；其中，具有标记物的表面增强拉曼基底材料在待测水样的漂浮时间与在次氯酸钠标准溶液的漂浮时间相同。
在本发明的一些实施方式中，所述方法对游离氯进行检测时，待测水样中不含有H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -。
本发明中，所述方法的检出限为0.01ppm。
在本发明的一些实施方式中，延长步骤S4中具有标记物的表面增强拉曼基底材料在待测水样表面的漂浮时间，通过检测所述拉曼基底材料上标记物的特征拉曼信号峰值变化，实现对待测水样的长期监测。即可监测表面增强拉曼基底材料漂浮时间段内水样中游离氯情况。
本发明的有益效果为：本发明所述方法所使用的基底材料制备简单、成本低，且质轻，可漂浮、易携带，检测速度快且灵敏度高，对于各种极端环境(高温、强酸、强碱)都具有较好的使用效果，且能重复利用。在便携式拉曼光谱仪的帮助下能够实现现场检测，且检测过程中无需繁琐配制溶液，操作便捷。检测时可以将基底材料漂浮于待测水样表面进行原位检测(同时可实现长期监控)，也可以将基底材料从待测水样中取出检测，减少水体环境(例如水浑浊度)对检测结果的影响。总之本发明所述方法具有简单、快速、准确、干扰小、可再生、成本低、灵敏高，可长期监测等优点。
附图说明
下面将结合附图对本发明作进一步说明。
图1为AuNPs/PVC膜制备及检测原理示意图。
图2为AuNPs/PVC膜的电镜图。
图3为AuNPs/PVC膜截面电镜图。
图4为不同浓度次氯酸钠标准溶液浸泡的具有4-ATP的AuNPs/PVC膜的拉曼光谱图。
图5为次氯酸钠浓度和4-ATP的拉曼峰面积积分的关系图。
图6为不同干扰离子对具有4-ATP的AuNPs/PVC膜检测次氯酸钠溶液过程产生的影响图。
图7为实施例5的拉曼光谱图。
具体实施方式
下面将对本发明作详细说明。
现有的国家标准GB/T5750.11—2006《生活饮用水标准检验方法消毒剂指标》，使用N,N-二乙基对苯二胺(DPD)分光光度法和3,3’,5,5’-四甲基联苯胺比色法检测水中游离余氯，前者需要配制较多试剂，操作步骤繁琐，测量过程中，显色时间对测量结果影响较大，后者通过肉眼比色，误差较大，且国标方法对水质有一定要求，对于较浑浊的水样，测量结果准确度较低。目前，这种方法只能作为定时取样，无法实现长期监测。
本发明针对上述缺点，采用表面增强拉曼散射(SERS)技术来检测水中的游离余氯。本发明制备一种新型SERS基底材料，基底材料上修饰有能与游离余氯发生反应的标记物。当游离余氯存在时，游离余氯会与标记物反应，使标记物从SERS基底材料上脱落，然后通过测定SERS基底材料上标记物拉曼信号的降低程度，并与标准曲线对比，即可计算出待测水样中游离余氯的浓度。
采用SERS检测时，既可以将基底材料漂浮于待测水样表面进行原位检测，又可以把基底材料从待测水样中取出，进而不会受到水体浑浊等其它物质干扰。此外，本发明所述方法采集的是标记物的拉曼光谱，其具有分子指纹特异性，与其它方法相比干扰小，误差低。再者，SERS技术检测速度快，几秒钟就可以获得拉曼信号，而且SERS基底材料可以简单再生使用，有效降低成本。当SERS基底材料采用柔性、超轻SERS基底材料时，可将SERS基底漂浮在水面，用于监控时间段内的是否有游离余氯排，可有效防止过量余氯排放，被水体稀释后，无法准确检测的问题。
因此，本发明所涉及的基于拉曼光谱的水中游离氯的检测方法，其包括以下步骤：
S1，通过界面自组装法制备表面增强拉曼基底材料；
S2，对步骤S1制得的表面增强拉曼基底材料进行修饰，获得具有标记物的表面增强拉曼基底材料；
S3，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对已知浓度的系列次氯酸钠标准溶液进行检测，进而绘制游离氯检测的标准曲线；
S4，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对待测水样中的游离氯进行检测，并将检测结果与步骤S3中绘制的标准曲线进行比较，获得待测水样中游离氯的浓度。
本发明的一些实施方式中，所述表面增强拉曼基底材料可以通过液-液界面自组装法进行制备，具体为：在纳米粒子溶液的上方加入含有高分子聚合物的有机溶液，然后纳米粒子上浮至油/水界面，并进行自组装；待加入的有机溶剂挥发完全后，高分子聚合物在界面形成薄膜，固定住界面处已组装的纳米粒子；将所述界面处获得的镶嵌纳米粒子组装结构的高分子薄膜取出，即得表面增强拉曼基底材料。所述表面增强拉曼基底材料为超薄、质轻、柔韧和半透光薄膜。
在本发明的一些优选的实施方式中，所述表面增强拉曼基底材料厚度可以为10～300um。
在本发明进一步优选的实施方式中，所述表面增强拉曼基底材料包括两层，其中一层为纳米粒子自组装层，厚度可以为20～300nm，另一层为高分子聚合物支撑层，厚度可以为10～300um；进一步优选地，所述高分子聚合物支撑层半包裹所述纳米粒子自组装层，即所述纳米粒子自组装结构半镶嵌在所述高分子聚合物薄膜中，部分纳米粒子自组装结构部分暴露。
本发明中，所述表面增强拉曼基底材料可通过等离子体技术去除纳米粒子自组装层上多余的高分子聚合物，进而可调控高分子聚合物支撑层对纳米粒子自组装层的包裹状态。
由于局域表面等离子共振(LSPR)，所制备的表面增强拉曼基底材料在拉曼光谱仪测试下对信号分子具有显著的增强效果。
值得注意的是：所述表面增强拉曼基底材料的制备方法不限于上述的液-液界面，还可以采用气-液界面法或液-固界面法进行制备。
在本发明的一些实施方式中，所述纳米粒子选自金、银、铜、铂和它们的合金中的至少一种。除了上述金属外，本发明所采用的纳米粒子还可以利用其他具有局域表面等离子共振效应(LSPR)的纳米粒子进行替换。当选用的纳米粒子为银时，获得的表面增强拉曼基底材料的拉曼信号更强，但是银易氧化，因此当选用的纳米粒子为银时，需要将制得的表面增强拉曼基底材料再浸泡于如HAuCl 4溶液中，使其包裹上金，提高其抗氧化能力。
在本发明的一些具体实施方式中，所述纳米粒子的粒径选自10～100nm，优选选自40～60nm；最优选为50nm。
在本发明的另一些实施方式中，所述高分子聚合物优选自聚氯乙烯、聚乙酸乙烯酯、聚氨酯、聚苯乙烯和聚甲基丙烯酸甲酯中的至少一种。本发明所选用的高分子聚合物不限于上述物质，所选用的高分子聚合物还可以为聚二甲基硅氧烷、聚丙烯、聚碳酸酯、丙烯腈-丁二烯-苯乙烯共聚物(ABS树脂)、氯醇橡胶、硝酸纤维素。
在本发明的一些实施方式中，所述有机溶剂选自环己酮、乙酸乙酯、甲苯和环乙烷中的至少一种。
在本发明的一些具体实施方式中，步骤S2的具体操作为：将步骤S1制得的表面增强拉曼基底材料浸泡于标记物溶液中，然后进行清洗，获得具有标记物的表面增强拉曼基底材料。
在本发明的一些优选的实施方式中，所述浸泡的时间为10～30分钟。
在本发明的一些实施方式中，步骤S2中，所述标记物能与游离氯发生反应，优选地所述反应为标记物与拉曼基底形成金属-S键(如Au-S)，在游离氯存在的情况下，Au-S断裂，进而使标记物从SERS基底材料上脱落；优选地，所述标记物选自4-氨基苯硫酚、4-硝基苯硫酚、4-巯基吡啶、半胱氨酸、谷胱甘肽和秋兰姆中的至少一种。
在本发明的一些具体实施方式中，步骤S3的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于已知浓度的系列次氯酸钠标准溶液表面，然后使用拉曼光谱仪检测在次氯酸钠标准溶液表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，进而绘制拉曼信号峰值-游离氯浓度的标准曲线。
在本发明的一些优选的实施方式中，所述系列次氯酸钠标准溶液的浓度为0～10.0ppm。在本发明的一些具体实施方式中，所述次氯酸钠标准溶液的浓度可以为0、0.05ppm、0.3ppm、0.5ppm、1.0ppm、1.5ppm、2.0ppm、5.0ppm、8.0ppm或10.0ppm等。
在本发明的另一些优选的实施方式中，所述漂浮的时间为1～10分钟，优选为3分钟。
在本发明的一些具体实施方式中，步骤S4的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于待测水样表面，然后使用拉曼光谱仪检测在待测水样表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，将检测的拉曼信号峰值与步骤S3绘制的标准曲线进行比较，获得待测水样中游离氯的浓度；其中，具有标记物的表面增强拉曼基底材料在待测水样的漂浮时间与在次氯酸钠标准溶液的漂浮时间相同。
在本发明的一些实施方式中，在使用拉曼光谱仪检测漂浮后的具有标记物的表面增强拉曼基底材料前，将所述拉曼基底材料取出并进行清洗，进而移除被检测水体中物理吸附的干扰物质，提高检测精准性和灵敏度。
在本发明的一些实施方式中，所述方法对游离氯进行检测时，待测水样中不 含有H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -。由于该方法对H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -等强氧化性物质也有反应，因此对待测水样中游离氯进行检测时，为了避免H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -等强氧化性物质的干扰，待测水样中需不能含有H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -等强氧化性物质。
在本发明的一些具体实施方式中，所述方法具体包括：
(1)取纳米粒子溶液缓慢搅拌，在溶液上方缓慢加入含有高分子有机物聚合物的有机溶液，诱导纳米粒子上浮至油/水界面，并进行自组装；待加入的有机溶剂挥发完全后，高分子聚合物在界面形成薄膜，固定住界面处已组装的纳米粒子；将所述界面处获得的镶嵌纳米粒子组装结构的高分子薄膜取出，即得表面增强拉曼基底材料；
(2)将上述表面增强拉曼基底材料浸泡在标记物溶液中，浸泡10-30分钟，清洗，得到具有标记物的表面增强拉曼基底材料；
(3)将步骤(2)制备的具有标记物的表面增强拉曼基底材料漂浮于已知浓度的系列次氯酸钠标准溶液中，取出所述表面增强拉曼基底材料并进行清洗，然后使用拉曼光谱仪检测在次氯酸钠标准溶液表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，进而绘制拉曼信号峰值-游离氯浓度的标准曲线；
(4)将步骤(2)制备的具有标记物的表面增强拉曼基底材料漂浮于未知余氯浓度的待测水样中相同时间，取出所述表面增强拉曼基底材料并进行清洗，然后使用拉曼光谱仪检测在待测水样表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，将所检测的拉曼信号峰值与步骤(3)所绘制的标准曲线对比，得到待测水样中游离余氯的浓度。
本发明中，所述方法的检出限为0.01ppm。
在本发明的一些实施方式中，延长步骤S4中具有标记物的表面增强拉曼基底材料在待测水样表面的漂浮时间，通过检测所述拉曼基底材料上标记物的特征拉曼信号峰值变化，来确定监测时间段内，是否有余氯排放，实现对待测水样的长期监测。
相对于其它余氯排放监测方法，本发有以下优势：第一，基底可一直漂浮于待测水样，实现不间断监测，一旦有余氯排放，即可与基底反应，准确监控余氯 排放，无需频繁取样，即可知道监测时间段内有无余氯排放。第二，可有效防止偷排，排放后因水体稀释、流走，导致检测不足的缺点。
实施例
为使本发明更加容易理解，下面将结合实施例来进一步详细说明本发明，这些实施例仅起说明性作用，并不局限于本发明的应用范围。本发明中所使用的原料或组分若无特殊说明均可以通过商业途径或常规方法制得。
实施例1：表面增强拉曼基底材料：具有4-ATP的AuNPs/PVC膜的制备
取金纳米粒子溶胶(AuNPs)缓慢搅拌，在溶液上方缓慢加入聚氯乙烯(PVC)的环己酮溶液，诱导金纳米粒子上浮至油/水界面，并进行自组装；待环己酮挥发完全，PVC在界面形成薄膜，固定住界面处已组装的金纳米粒子；将所述界面处获得的镶嵌金纳米粒子组装结构的PVC薄膜取出，得到表面增强拉曼基底材料AuNPs/PVC膜，所述AuNPs/PVC膜的厚度为110um，其中金纳米粒子自组装层的厚度为150nm；聚氯乙烯支撑层的厚度为110um。所述表面增强拉曼基底材料AuNPs/PVC膜的电镜图如图2和3所示。
将得到的AuNPs/PVC膜浸泡在4-氨基苯硫酚溶液(4-ATP)中，浸泡20分钟，得到在1079cm -1附近具有特征拉曼信号的具有4-ATP的AuNPs/PVC膜。
实施例2：拉曼信号峰值-游离氯浓度的标准曲线的绘制
将实施例1制备的具有4-ATP的AuNPs/PVC膜分别漂浮于20mL已知浓度的系列次氯酸钠标准溶液(0、0.05ppm、0.3ppm、0.5ppm、1ppm、1.5ppm)中3min，取出漂浮后的AuNPs/PVC膜并进行清洗，使用拉曼光谱仪检测漂浮于不同浓度的次氯酸钠标准溶液的AuNPs/PVC膜的4-ATP分子在拉曼峰1079cm -1附近信号值，进而绘制出拉曼信号峰值与次氯酸钠浓之间关系的标准曲线。其中，漂浮于不同浓度的次氯酸钠标准溶液的AuNPs/PVC膜的4-ATP分子在拉曼峰1079cm -1附近信号值如图4所示。绘制的次氯酸钠浓度与4-ATP的拉曼信号峰面积积分的关系图如图5所示。
实施例3：待测水样的检测
将实施例1制备的具有4-ATP的AuNPs/PVC膜漂浮于20mL的自来水样中3min，取出漂浮后的AuNPs/PVC膜并进行清洗，使用拉曼光谱仪检测漂浮后的AuNPs/PVC膜的4-ATP分子在拉曼峰1079cm -1附近信号值，将所检测的拉曼信号峰值与实施例2所绘制的标准曲线对比，获得自来水样中的余氯浓度，其为0.06ppm。
实施例4：干扰离子对检测的影响
将实施例1制备的具有4-ATP的AuNPs/PVC膜漂浮在含有不同干扰离子的次氯酸钠溶液之中，使用拉曼光谱仪检测漂浮于不同干扰离子的次氯酸钠溶液的AuNPs/PVC膜的4-ATP分子在拉曼峰1079cm -1附近信号值，绘制不同干扰离子对实施例1制备的具有4-ATP的AuNPs/PVC膜检测次氯酸钠溶液过程产生的影响，结果如图6所示。从图6可以看出，不同干扰离子对检测结果影响不大。说明，利用本发明制备的新型表面增强拉曼基底材料对游离氯离子进行检测的方法，其受外界的影响较小。
实施例5：使用金纳米粒子溶胶作为标记物基底的检测效果
取金纳米粒子溶胶(AuNPs)，加入4-ATP溶液，搅拌均匀，然后离心去除未链接的4-ATP，将沉淀的金纳米粒子重新分散于水中，使用便携式拉曼仪进行测量金纳米粒子溶胶加入4-ATP分子前后的拉曼信号，如图7所示，然后再往含4-ATP的金纳米粒子溶胶中加入1.5ppm次氯酸钠溶液，4-ATP分子拉曼信号并没有明显下降，如图7所示。说明使用金纳米粒子溶胶作为标记物基底的无法检测游离氯。这可能是因为金纳米粒子溶胶上的4-ATP虽然会被游离氯破坏Au-S，但是破坏后的4-ATP可能会通过物理吸附或静电作用，再吸附到金纳米粒子溶胶上，导致4-ATP的拉曼信号没有明显改变。此外，使用金纳米粒子溶胶时，易受到外界影响，导致金纳米粒子溶胶不稳定，团聚等问题，检测不准。
实施例6
取银纳米粒子溶胶(AgNPs)缓慢搅拌，在溶液上方缓慢加入聚氨酯(PU)的环己酮溶液，诱导银纳米粒子上浮至油水界面，并进行自组装；待环己酮挥发完全，将所述界面处获得的镶嵌银纳米粒子组装结构的PU薄膜取出，将得到的 表面增强拉曼基底材料AgNPs/PU膜；将得到的AgNPs/PU膜浸泡在HAuCl 4溶液中3分钟，得到AgNPs@Au/PU膜。将得到的AgNPs@Au/PU膜浸泡在4-巯基吡啶(4-Mpy)溶液中15分钟，得到在1096cm -1附近具有特征拉曼信号的具有4-Mpy的AgNPs@Au/PU膜。将上述AgNPs@Au/PU膜漂浮于污水处理厂出口水面一段时间，4-MPy的特征峰消失，说明该段时间内水体中有游离氯存在。
实施例7：表面增强拉曼基底材料：具有4-ATP的AuNPs/PVC膜的制备
制备过程基本同实施例1，不同之处在于改变金纳米粒子溶胶(AuNPs)的加入量和上浮时间，使得获得的AuNPs/PVC膜的厚度为110um，其中金纳米粒子自组装层的厚度为50nm；聚氯乙烯支撑层的厚度为110um。
实施例8：表面增强拉曼基底材料：具有4-ATP的AuNPs/PVC膜的制备
制备过程基本同实施例1，不同之处在于改变金纳米粒子溶胶(AuNPs)的粒径、加入量和上浮时间，使得获得的AuNPs/PVC膜的厚度为110um，其中金纳米粒子自组装层的厚度为20nm；聚氯乙烯支撑层的厚度为110um。
实施例9：
利用实施例1、7和8所制备的具有4-ATP的AuNPs/PVC膜分别检测同一系列不同浓度的水样，检测结果显示实施例1制备的4-ATP的AuNPs/PVC膜的最低检测线为0.01ppm，实例7制备的4-ATP的AuNPs/PVC膜的最低检测线为0.02ppm，实例8制备的4-ATP的AuNPs/PVC膜的最低检测线为0.05ppm。
实施例10
将实施例1制备的具有4-ATP的AuNPs/PVC膜漂浮在含有0.1ppm次氯酸钠的实际水样中，使用拉曼光谱仪多次检测漂浮于不同干扰离子的次氯酸钠水样的AuNPs/PVC膜的4-ATP分子在拉曼峰1079cm -1附近信号值，计算其RSD为12.48％。根据国标《GB/T 14424-2008工业循环冷却水中余氯的测定》的方法测量0.01ppm次氯酸钠溶液，多次重复测量结果，其RSD为43.30％。对比拉曼光谱测量的结果，本方法在低浓度测量中具有更好的重复性。
应当注意的是，以上所述的实施例仅用于解释本发明，并不构成对本发明的任何限制。通过参照典型实施例对本发明进行了描述，但应当理解为其中所用的词语为描述性和解释性词汇，而不是限定性词汇。可以按规定在本发明权利要求的范围内对本发明作出修改，以及在不背离本发明的范围和精神内对本发明进行修订。尽管其中描述的本发明涉及特定的方法、材料和实施例，但是并不意味着本发明限于其中公开的特定例，相反，本发明可扩展至其他所有具有相同功能的方法和应用。

Claims (20)

  1. 一种基于拉曼光谱的水中游离氯的检测方法，其包括以下步骤：
    S1，通过界面自组装法制备表面增强拉曼基底材料；
    S2，对步骤S1制得的表面增强拉曼基底材料进行修饰，获得具有标记物的表面增强拉曼基底材料；
    S3，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对已知浓度的系列次氯酸钠标准溶液进行检测，进而绘制游离氯检测的标准曲线；
    S4，利用步骤S2中获得的具有标记物的表面增强拉曼基底材料，对待测水样中的游离氯进行检测，并将检测结果与步骤S3中绘制的标准曲线进行比较，获得待测水样中游离氯的浓度。
  2. 根据权利要求1所述的方法，其特征在于，步骤S1的具体操作为：在纳米粒子溶液的上方加入含有高分子聚合物的有机溶液，然后纳米粒子上浮至油/水界面，并进行自组装；待加入的有机溶剂挥发完全后，高分子聚合物在界面形成薄膜，固定住界面处已组装的纳米粒子；将所述界面处获得的镶嵌纳米粒子组装结构的高分子薄膜取出，即得表面增强拉曼基底材料。
  3. 根据权利要求1或2所述的方法，其特征在于，所述表面增强拉曼基底材料厚度为10～300um。
  4. 根据权利要求1-3中任意一项所述的方法，其特征在于，所述表面增强拉曼基底材料包括两层，其中一层为纳米粒子自组装层，厚度为20～300nm，另一层为高分子聚合物支撑层，厚度为10～300um；优选地，所述高分子聚合物支撑层半包裹所述纳米粒子自组装层。
  5. 根据权利要求1-4中任意一项所述的方法，其特征在于，所述纳米粒子选自金、银、铜、铂和它们的合金中的至少一种。
  6. 根据权利要求1-5中任意一项所述的方法，其特征在于，所述纳米粒子的粒径选自10～100nm，优选选自40～60nm。
  7. 根据权利要求1-6中任意一项所述的方法，其特征在于，所述高分子聚合物选自聚氯乙烯、聚乙酸乙烯酯、聚氨酯和聚甲基丙烯酸甲酯、聚苯乙烯中的至少一种。
  8. 根据权利要求1-7中任意一项所述的方法，其特征在于，所述有机溶剂选自环己酮、甲苯、乙酸乙酯和环乙烷中的至少一种。
  9. 根据权利要求1-8中任意一项所述的方法，其特征在于，步骤S2的具体操作为：将步骤S1制得的表面增强拉曼基底材料浸泡于标记物溶液中，然后进行清洗，获得具有标记物的表面增强拉曼基底材料。
  10. 根据权利要求9所述的方法，其特征在于，所述浸泡的时间为10-30分钟。
  11. 根据权利要求1-10中任意一项所述的方法，其特征在于，所述标记物能与游离氯发生反应。
  12. 根据权利要求1-11中任意一项所述的方法，其特征在于，所述标记物选自4-氨基苯硫酚、4-硝基苯硫酚、4-巯基吡啶、半胱氨酸、谷胱甘肽和秋兰姆中的至少一种。
  13. 根据权利要求1-12中任意一项所述的方法，其特征在于，步骤S3的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于已知浓度的系列次氯酸钠标准溶液表面，然后使用拉曼光谱仪检测在次氯酸钠标准溶液表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，进而绘制拉曼信号峰值-游离氯浓度的标准曲线。
  14. 根据权利要求13所述的方法，其特征在于，所述系列次氯酸钠标准溶液的浓度为0～10.0ppm。
  15. 根据权利要求13或14所述的方法，其特征在于，所述漂浮的时间为1～10分钟。
  16. 根据权利要求1-15中任意一项所述的方法，其特征在于，步骤S4的具体操作为：将具有标记物的表面增强拉曼基底材料漂浮于待测水样表面，然后使用拉曼光谱仪检测在待测水样表面漂浮后的所述具有标记物的表面增强拉曼基底材料上的标记物的特征拉曼信号峰值，将检测的拉曼信号峰值与步骤S3绘制的标准曲线进行比较，获得待测水样中游离氯的浓度；其中，具有标记物的表面增强拉曼基底材料在待测水样的漂浮时间与在次氯酸钠标准溶液的漂浮时间相同。
  17. 根据权利要求13-16中任意一项所述的方法，其特征在于，在使用拉曼光谱仪检测漂浮后的具有标记物的表面增强拉曼基底材料前，将所述拉曼基底材料取出并进行清洗。
  18. 根据权利要求1-17中任意一项所述的方法，其特征在于，所述方法对游离氯进行检测时，待测水样中不含有H 2O 2、O 3、Cr 2O 7 2-和MnO 4 -。
  19. 根据权利要求1-18中任意一项所述的方法，其特征在于，所述方法的检出限为0.01ppm。
  20. 根据权利要求16所述的方法，其特征在于，延长步骤S4中具有标记物的表面增强拉曼基底材料在待测水样表面的漂浮时间，通过检测所述拉曼基底材料上标记物的特征拉曼信号峰值变化，实现对待测水样中游离氯的长期监测。
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