CN109884026B - Liquid-phase in-situ SERS detection method - Google Patents
Liquid-phase in-situ SERS detection method Download PDFInfo
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- CN109884026B CN109884026B CN201910054272.2A CN201910054272A CN109884026B CN 109884026 B CN109884026 B CN 109884026B CN 201910054272 A CN201910054272 A CN 201910054272A CN 109884026 B CN109884026 B CN 109884026B
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Abstract
The invention provides a liquid-phase in-situ SERS detection method, and belongs to the technical field of detection and analysis. The method comprises the steps of mixing an inducer and an organic solvent to obtain an oil phase mixed solution; immersing the detection end of the detection optical fiber into the oil phase mixed solution for infiltration, so that the detection end is wrapped with a layer of the oil phase mixed solution; the other end of the detection optical fiber is coupled with the Raman spectrometer; soaking the soaked detection optical fiber into a liquid to be detected, forming local water-oil interface self-assembly on the end face of a detection end by the noble metal nano particles and molecules of a substance to be detected under the action of an inducer, and then collecting a Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles. The method realizes the stable, in-situ and high-sensitivity detection of the SERS spectrum of the molecules of the object to be detected in the liquid phase environment, and has the advantages of simple operation, low cost and good repeatability.
Description
Technical Field
The invention relates to the technical field of detection and analysis, in particular to a liquid-phase in-situ SERS detection method.
Background
Surface Enhanced Raman Scattering (SERS) is currently the most commonly used Raman enhancement technique, which is based on the localized surface plasmon resonance effect of noble metal nanoparticles and can provide 106～1010The magnitude Raman signal enhancement has important application prospect in the fields of biomedicine, environmental monitoring, Internet of things and the like. The stability and in-situ detection of liquid-phase SERS spectrum are an important direction for the research of the current SERS technology.
The method utilizes an inducer to reduce the surface charge of noble metal nanoparticles in a solution or the thickness of an electric double layer around the particles, and realizes the self-assembly film formation of the noble metal nanoparticles on the water-oil interface so as to provide a large SERS enhancement factor. In order to realize in-situ detection of liquid-phase SERS (surface enhanced Raman scattering) spectrum, people try to directly focus Raman excitation light to a water-oil interface for Raman spectrum collection; however, the noble metal nanoparticle film on the water-oil interface is light in weight, and under the irradiation of the focused raman excitation light, the light momentum causes the nanoparticle drift, so that the detection stability of the SERS spectrum is greatly influenced. At present, the more common method is to transfer the noble metal nanoparticle thin film constructed on the water-oil interface to a planar substrate (such as a glass sheet, a silicon wafer and the like), and then perform the SERS spectrum detection to obtain a stable and reliable SERS spectrum; however, the thin film transfer method is difficult to realize in-situ detection of liquid-phase SERS spectra.
Disclosure of Invention
The invention aims to provide a liquid-phase in-situ SERS detection method which has the advantages of simplicity in operation, low cost and good repeatability.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a liquid-phase in-situ SERS detection method, which comprises the following steps:
mixing an inducer and an organic solvent to obtain an oil phase mixed solution;
immersing the detection end of the detection optical fiber into the oil phase mixed solution for infiltration; the other end of the detection optical fiber is coupled with the Raman spectrometer;
immersing the soaked detection end into a liquid to be detected, carrying out self-assembly, and then collecting a Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles.
Preferably, the inducer comprises ethanol or acetone.
Preferably, the organic solvent comprises cyclohexane, hexane or n-butanol.
Preferably, the volume ratio of the inducer to the organic solvent is 1: 1-10.
Preferably, the detection end of the detection optical fiber is a bare fiber.
Preferably, the soaking time is 10-30 min.
Preferably, the coupling connection mode is an optical fiber coupling mode using an FC/PC or SMA905 optical fiber interface, or a spatial optical path coupling mode.
Preferably, the raman spectrometer is a portable raman spectrometer.
Preferably, the noble metal nanoparticles are at least one of gold nanoparticles and silver nanoparticles; the particle size of the noble metal nano-particles is 10-60 nm.
The invention provides a liquid-phase in-situ SERS detection method, which comprises the following steps: mixing an inducer and an organic solvent to obtain an oil phase mixed solution; immersing the detection end of the detection optical fiber into the oil phase mixed solution for infiltration; the other end of the detection optical fiber is coupled with the Raman spectrometer; soaking the soaked detection optical fiber into a liquid to be detected, carrying out self-assembly, and collecting a Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles. According to the invention, the detection end is wrapped with a layer of oil phase mixed solution consisting of an inducer and an organic solvent, then the detection end with a thin layer of oil phase solution wrapped on the surface is inserted into the aqueous solution containing the object to be detected and the noble metal nanoparticles, and the noble metal nanoparticles and the molecules of the object to be detected form local water-oil interface self-assembly on the end surface of the detection end under the action of the inducer, so that a high-sensitivity SERS substrate is constructed, the stable, in-situ and high-sensitivity detection of the SERS spectrum of the molecules of the object to be detected in a liquid phase environment is realized, and the method has the advantages of simple operation, low cost and.
Drawings
FIG. 1 is a schematic diagram of a liquid-phase in-situ SERS detection method provided by the present invention;
FIG. 2 shows the liquid-phase in-situ SERS detection result of melamine molecules.
Detailed Description
The invention provides a liquid-phase in-situ SERS detection method, which comprises the following steps:
mixing an inducer and an organic solvent to obtain an oil phase mixed solution;
immersing the detection end of the detection optical fiber into the oil phase mixed solution for infiltration; the other end of the detection optical fiber is coupled with the Raman spectrometer;
immersing the soaked detection end into a liquid to be detected, carrying out self-assembly, and collecting a Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles.
According to the invention, the detection end with the surface wrapped by the thin oil phase solution is inserted into the aqueous solution containing the object to be detected and the noble metal nanoparticles, and the noble metal nanoparticles and the molecules of the object to be detected form local water-oil interface self-assembly on the end surface of the detection end, so that a high-sensitivity SERS substrate is constructed, the liquid-phase in-situ SERS detection is realized, and the method has the advantages of simplicity in operation, low cost and good repeatability.
The invention mixes the inducer and the organic solvent to obtain the oil phase mixed solution.
In the present invention, the inducing agent preferably includes ethanol or acetone. In the invention, the inducer can reduce the surface charge of the noble metal nanoparticles in a solution or the thickness of an electric double layer around the particles, so that the noble metal nanoparticles are self-assembled into a film at a water-oil interface in a subsequent step to provide a large SERS enhancement factor.
In the present invention, the organic solvent preferably includes cyclohexane, hexane or n-butanol. In the present invention, the organic solvent is used to form an oil-water interface in a subsequent step.
In the invention, the volume ratio of the inducer to the organic solvent is preferably 1: 1-10. In the invention, the oil phase environment is not easily damaged by the proportion, and the subsequent induction of the self-assembly of the noble metal nanoparticles on the water-oil interface is facilitated.
After the oil phase mixed solution is obtained, the detection end of the detection optical fiber is immersed in the oil phase mixed solution for infiltration; and the other end of the detection optical fiber is coupled and connected with the Raman spectrometer. In the invention, after the detection end is immersed in the oil phase mixed solution, the oil phase mixed solution can wrap the detection end under the action of surface tension to form a layer of oil phase mixed solution, thereby providing conditions for self-assembly of the precious metal nano particles and the object to be detected in the subsequent detection process.
In the present invention, the detection end of the detection optical fiber is preferably a bare fiber. The material of the detection optical fiber is not particularly limited, and the detection optical fiber can be made of a conventional optical fiber.
The structure of the detection end is not particularly limited in the present invention, and in the embodiment of the present invention, the detection end is preferably a flat end surface or a tapered structure.
In the invention, the soaking time is preferably 10-30 min.
In the invention, the coupling connection mode is preferably an optical fiber coupling mode by using an FC/PC or SMA905 optical fiber interface, or a space optical path coupling mode.
In the present invention, the raman spectrometer is preferably a portable raman spectrometer. In the invention, the portable Raman spectrometer can realize in-situ and high-sensitivity detection of the Raman spectrum of the molecules of the object to be detected, and is more convenient and rapid.
After the infiltration is finished, the invention immerses the infiltrated detection end into the liquid to be detected, carries out self-assembly and then collects the Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles. In the invention, after the detection end is immersed in the liquid to be detected, a local water-oil interface is formed near the end surface of the detection end due to the existence of an organic solvent; under the action of an inducer, the noble metal nanoparticles and the molecules of the object to be detected in the water phase move to the interface to carry out self-assembly (as shown in figure 1), and a noble metal nanoparticle thin film is formed to provide a large SERS enhancement factor.
The angle of the detection end immersed in the liquid to be detected is not particularly limited, and in the embodiment of the invention, the detection end is preferably immersed in the liquid to be detected in a manner of being vertical to the liquid level of the liquid to be detected.
The time of the self-assembly is not particularly limited in the present invention, and can be adjusted by those skilled in the art according to the actual circumstances of the experiment. In the embodiment of the present invention, the self-assembly time is preferably 30s to 20 min.
In the present invention, the noble metal nanoparticles are preferably at least one of gold nanoparticles and silver nanoparticles; the particle size of the noble metal nanoparticles is preferably 10nm to 60 nm. The source of the noble metal nano particles is not specially limited, and the noble metal nano particles can be prepared by commercial products or laboratories; in the present embodiment, a commercially available noble metal nanoparticle sol is preferably used; the optical density OD value of the noble metal nano particle sol is preferably 5-20; the content of the noble metal nanoparticles in the solution to be detected is not particularly limited, and a person skilled in the art can adjust the content of the appropriate noble metal nanoparticles by a conventional test means.
The concentration of the substance to be detected in the liquid to be detected is not particularly limited, and a person skilled in the art can adjust the concentration to obtain a proper concentration by a conventional technical means according to the sensitivity of the Raman spectrometer to different substances.
In the present invention, after completion of one test, it is preferable to cut off the used test end and then perform the next test with a new test end.
The following examples are provided to describe the method for detecting SERS in situ in liquid phase according to the present invention in detail, but they should not be construed as limiting the scope of the present invention.
Examples
Selecting ethanol as an inducer and cyclohexane as an organic solvent, and mixing the ethanol and the cyclohexane in equal volume to obtain an oil phase mixed solution; the concentration is 2 x 10-5Mixing the melamine aqueous solution of M and the gold nanoparticle sol in equal volume to obtain a solution to be detected, wherein the optical density OD value of the gold nanoparticle sol is 10; using optical fibers with the diameters of a fiber core and a cladding of 200 mu m and 220 mu m respectively as detection optical fibers; removing a cladding at one end of the detection optical fiber to serve as a detection end; the other end of the detection optical fiber is coupled and connected with the portable Raman spectrometer by using an FC/PC optical fiber interface; cutting the end face of the detection end into a flat end face by using an optical fiber cutter, then soaking the flat end face into the oil phase mixed solution for 15min, and taking out the flat end face; and inserting the soaked detection end into the liquid to be detected, carrying out self-assembly on the noble metal nano particles and the molecules to be detected on the local water-oil interface of the end face of the optical fiber, and opening the portable Raman spectrometer for Raman spectrum collection.
FIG. 2 shows the SERS spectrum of melamine molecules collected after 5min of self-assembly at water-oil interface, and it can be seen from FIG. 2 that the peak at 682cm is a characteristic peak-1Higher SERS signals are obtained, so that the feasibility of the method for realizing liquid phase in-situ detection is shown.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. The liquid-phase in-situ SERS detection method is characterized by comprising the following steps of:
mixing an inducer and an organic solvent to obtain an oil phase mixed solution; the organic solvent comprises cyclohexane, hexane or n-butanol; the inducer comprises ethanol or acetone;
immersing the detection end of the detection optical fiber into the oil phase mixed solution for infiltration; the other end of the detection optical fiber is coupled with the Raman spectrometer; the detection end of the detection optical fiber is a bare fiber;
immersing the soaked detection end into a liquid to be detected, carrying out self-assembly, and then collecting a Raman spectrum; the liquid to be detected is an aqueous solution containing an object to be detected and noble metal nano particles.
2. The detection method according to claim 1, wherein the volume ratio of the inducer to the organic solvent is 1:1 to 10.
3. The detection method according to claim 1, wherein the soaking time is 10-30 min.
4. The detection method according to claim 1, wherein the coupling connection mode is an optical fiber coupling mode using an FC/PC or SMA905 optical fiber interface, or a spatial optical path coupling mode.
5. The detection method according to claim 1 or 4, wherein the Raman spectrometer is a portable Raman spectrometer.
6. The detection method according to claim 1, wherein the noble metal nanoparticles are at least one of gold nanoparticles and silver nanoparticles; the particle size of the noble metal nano-particles is 10 nm-60 nm.
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