CN111272727B - Substrate material for detecting chiral compounds - Google Patents
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Abstract
The invention provides a substrate material for detecting chiral compounds, which is matched with a Raman spectrometer for use so as to detect the chiral compounds, and is characterized in that: the substrate material is a surface plasmon resonance material with chirality. The substrate material can enhance the specific Raman scattering signal of the chiral compound, and has different enhancement degrees on different enantiomers, so that the content ratio of the enantiomer can be calculated through the characteristic peak intensity in a Raman spectrum. Compared with the detection means in the prior art, the detection of the chiral compound can be realized by combining the substrate material with a Raman spectrometer, and the method has the advantages of low cost, simplicity in operation, small interference, accurate result, simplicity in operation, wide application and the like.
Description
Technical Field
The present invention relates to a substrate material for use in the detection of chiral compounds.
Background
Chiral compounds refer to a class of compounds that have the same molecular structure but mirror images of each other in their conformation. In the pharmaceutical and chemical field, a pair of chiral compounds which are mirror images of each other usually have different characteristics, for example, thalidomide has two enantiomeric conformations of S and R which are mirror images of each other, wherein R has a central sedative effect, and S has a strong teratogenic effect. Therefore, the separation between enantiomers and the detection of the content are crucial steps in the development and production process of chiral compounds.
In the prior art, methods for analyzing and detecting chiral compounds mainly include two types, namely spectra and chromatograms. The spectral method is mostly implemented by using optical rotation and circular dichroism (i.e., the characteristic that the interaction with left and right circularly polarized light is different to cause the deflection of the emergent light or the increase of ellipticity) of a chiral compound, cannot detect a racemic system and molecules without chromophoric groups, and is difficult to eliminate the interference of linearly polarized light generated in the process of switching left and right circularly polarized light. The chromatographic method mainly relies on different interactions of chiral compounds with different conformations and fixed on a chromatographic column for separation, however, the applicable range of the chromatographic method is limited, and the chromatographic method cannot separate compounds with overlarge molecular weight, undersize molecular weight or no polarity and the like.
Raman scattering refers to the fact that when laser with a certain frequency irradiates the surface of a substance, molecules in the substance absorb part of energy, vibration is generated in different modes and degrees, then light with lower frequency is scattered, the change of the frequency is determined by the characteristics of the scattering substance and is expressed as a characteristic 'fingerprint spectrum', the molecular structure of the substance is reflected, and the detection of unknown substances can be achieved by utilizing the principle. However, chiral compounds that are enantiomers of each other are identical in molecular structure and cannot be distinguished by ordinary raman spectroscopy.
In the prior art, a device (i.e., a raman optical active device, referred to as ROA device for short) for detecting a chiral compound by a raman spectrometer by using a circularly polarized light source or a circularly polarized light detector has appeared, and the detection result of the chiral compound, pinene, is shown in fig. 22. As can be seen from fig. 22, when the sample contains two enantiomers of pinene and the contents of the two enantiomers are different, the intensities of characteristic peaks detected by ROA are obviously different, so that the content ratio of chiral compounds with different conformations can be obtained. However, in such ROA apparatus, a circular polarized light filtering component (for respectively converting light generated by the light source into left and right circular polarized light) needs to be additionally arranged in the common raman spectrometer or a circular polarized light detector (for respectively detecting emitted left and right circular polarized light) needs to be used, so that the cost of the apparatus is high. In addition, the method for detecting chiral compounds by using the ROA equipment still has the problems of low signal intensity, easy interference of false signals and the like.
Disclosure of Invention
In order to solve the above problems, the inventors of the present invention have studied on raman optical properties of a chiral compound, and found that the chiral compound has the following properties: when the surface plasmon resonance material with chirality is used as a substrate material for raman scattering detection, the raman scattering intensity of the chiral compound is increased, and the raman scattering enhancement degree for different enantiomers is different. Moreover, the inventor also finds that the enhancing effect of the chiral surface plasmon resonance material on the chiral compound and the conformation proportion of the chiral enantiomer accord with a linear rule, so that the content proportion can be calculated according to the characteristic peak intensity corresponding to the chiral compound to be detected in the Raman spectrum.
Based on the above findings, the inventors propose a substrate material for detecting chiral compounds, and specifically adopt the following technical scheme:
the invention provides a substrate material for detecting chiral compounds, which is used for being matched with a Raman spectrometer to detect the chiral compounds, and is characterized in that: the substrate material is a plasma resonance material with chirality.
The substrate material for detecting the chiral compound provided by the invention can also have the technical characteristics that the incident light and the detection light of the Raman spectrometer are unpolarized light.
The substrate material for detecting the chiral compound provided by the invention can also have the technical characteristics that the substrate material is a micro-nano powder material or a micro-nano film material which is composed of metal or metal oxide and has a chiral structure.
The substrate material for detecting the chiral compound provided by the invention can also have the technical characteristics that the metal is one or a composition of more of gold, silver, copper and platinum.
The substrate material for detecting the chiral compound provided by the invention can also have the technical characteristics that the metal oxide is one or a combination of copper oxide, titanium oxide, zinc oxide, tin oxide, iron oxide and cobalt oxide.
The substrate material for detecting the chiral compound provided by the invention can also have the technical characteristics that the chiral structure is any one of a spiral fiber structure, a flower-shaped structure, a fan-shaped structure and a propeller-shaped structure.
The substrate material for detecting a chiral compound provided by the present invention may further have a technical feature in which the helical fiber structure is composed of a single-strand helix or a double-strand helix, the diameter of the single-strand helix and the diameter of the double-strand helix are 5nm to 20nm, and the pitch is 25nm to 85 nm.
Action and Effect of the invention
According to the substrate material for detecting the chiral compound, which is provided by the invention, as the substrate material is a plasma resonance material with chirality, the substrate material can be used as a substrate material for carrying out specific Raman scattering signal enhancement on the chiral compound during Raman scattering detection, so that chiral compounds which are enantiomers mutually generate Raman scattering signals with different intensities, and the enhancement degrees of the different enantiomers are different, and therefore, the content ratio of the enantiomers can be calculated through the characteristic peak intensity in a Raman spectrum. Compared with the detection means in the prior art, the detection of the chiral compound can be realized by combining the substrate material with a common Raman spectrometer, and the method has the advantages of low cost, simplicity in operation, small interference, accurate result, simplicity in operation, wide application and the like.
Drawings
FIG. 1 is a scanning electron micrograph of an L-shaped gold nano spiral fiber array according to a first embodiment of the present invention;
FIG. 2 is a high-power scanning electron micrograph of an L-shaped gold nano spiral fiber array according to a first embodiment of the present invention;
FIG. 3 is a low-power TEM image of an L-shaped Au nano spiral fiber array according to a first embodiment of the present invention;
FIG. 4 is a high-power TEM image of an L-shaped Au nano spiral fiber array according to a first embodiment of the present invention;
FIG. 5 is a circular dichroism spectrum of an L-shaped gold nano spiral fiber array according to a first embodiment of the present invention;
FIG. 6 is a Raman spectrum of a mixture of R-limonene and S-limonene detected by using the L-type gold nano spiral fiber array according to the first embodiment of the invention;
FIG. 7 is a linear fitting graph of Raman characteristic peak intensity and enantiomer content percentage obtained by Raman scattering detection of a mixture of R-limonene and S-limonene by using an L-type gold nano-spiral fiber array according to the first embodiment of the present invention;
FIG. 8 is a Raman spectrum of a mixture of L-cyclohexylglycine and D-cyclohexylglycine detected by using an L-type gold nano-spiral fiber array according to a first embodiment of the present invention;
FIG. 9 is a linear fitting graph of Raman characteristic peak intensity and enantiomer content percentage obtained by Raman scattering detection of a mixture of L-cyclohexylglycine and D-cyclohexylglycine using an L-type gold nano-spiral fiber array according to the first embodiment of the present invention;
FIG. 10 is a Raman spectrum of a mixture of L-phenylglycine and D-phenylglycine using an L-type gold nanospiral fiber array according to example one of the present invention;
FIG. 11 is a linear fitting graph of Raman characteristic peak intensity and enantiomer content percentage obtained by Raman scattering detection of a mixture of L-phenylglycine and D-phenylglycine using an L-type gold nano-spiral fiber array according to the first embodiment of the present invention;
FIG. 12 is a scanning electron micrograph of an L-shaped gold nano spiral fiber array with the dosage of 4-mercaptobenzoic acid being 3.45mM according to example II of the invention;
FIG. 13 is a high-power SEM (scanning Electron microscope) photograph of an L-type gold nano spiral fiber array with the use amount of 3.45mM of 4-mercaptobenzoic acid in example II of the present invention;
FIG. 14 is a scanning electron micrograph of an L-shaped gold nano spiral fiber array with 4.14mM 4-mercaptobenzoic acid used in example II of the present invention;
FIG. 15 is a high-power SEM (scanning Electron microscope) photograph of an L-type gold nano spiral fiber array with 4.14mM of 4-mercaptobenzoic acid in accordance with example II of the present invention;
FIG. 16 is a scanning electron micrograph of an L-shaped gold nano spiral fiber array with an amount of 2.76mM of 4-mercaptobenzoic acid according to example II of the present invention;
FIG. 17 is a high-power SEM (scanning Electron microscope) photograph of an L-type gold nano spiral fiber array with the use amount of 2.76mM of 4-mercaptobenzoic acid in example II of the present invention;
FIG. 18 is a Raman spectrum of a mixture of R-limonene and S-limonene using a gold-silver nanospiral fiber array according to example III of the present invention;
FIG. 19 is a linear fit graph of Raman characteristic peak intensity and chiral enantiomer content percentage obtained by Raman scattering detection of a mixture of R-limonene and S-limonene by using a gold-silver nano-spiral fiber array according to a third embodiment of the invention;
FIG. 20 is a Raman spectrum of limonene with a conventional Raman spectrometer according to a comparative example of the present invention;
FIG. 21 is a Raman spectrum of a conventional Raman spectrometer and a substrate without chirality used for detecting limonene according to a comparative example of the present invention;
fig. 22 is a spectrum diagram of pinene detection using ROA equipment.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
< example one >
In the embodiment, an L-type gold nano spiral fiber array is adopted as a substrate material. The L-shaped gold nano spiral fiber array is a membrane material, is prepared by adopting an induced growth method, and specifically comprises the following steps:
step S1, placing a clean silicon substrate in a mixed solution containing concentrated sulfuric acid and hydrogen peroxide, hydrophilizing, heating at 60 ℃ for 2 hours, carrying out ultrasonic treatment for half an hour, then taking out the substrate, and washing with deionized water for three times;
step S2, placing the hydrophilized substrate into 5mM amino silanization reagent, standing for 2 hours to perform amination, then taking out the substrate, and washing with deionized water for three times;
step S3, putting the aminated substrate into the gold seed solution, soaking for 2 hours, and loading the gold seeds on the surface of the substrate;
and step S4, placing the substrate loaded with the gold seeds in a chiral inducer (N-acetyl-L-cysteine or N-acetyl-D-cysteine) solution containing 3.45mM, 4-mercaptobenzoic acid of 2.76mM, chloroauric acid of 8.62mM and ascorbic acid solution of 20.69mM, reacting for 15 minutes, taking out, washing with ethanol for three times, and drying to obtain the chiral gold nano spiral fiber array.
And step S5, removing residual organic matters in the chiral gold nano spiral fiber array by adopting cyclic voltammetry.
In this example, an L-type (left-handed) gold nano-helical fiber array and an R-type (right-handed) gold nano-helical fiber array were prepared using two chiral inducers, N-acetyl-L-cysteine and N-acetyl-D-cysteine, respectively.
Fig. 1 is a low-power scanning electron microscope photograph of an L-type gold nano-spiral fiber array according to a first embodiment of the present invention, fig. 2 is a high-power scanning electron microscope photograph of an L-type gold nano-spiral fiber array according to a first embodiment of the present invention, fig. 3 is a low-power transmission electron microscope photograph of an L-type gold nano-spiral fiber array according to a first embodiment of the present invention, and fig. 4 is a high-power transmission electron microscope photograph of an L-type gold nano-spiral fiber array according to a first embodiment of the present invention.
The above-mentioned fig. 1-4 are all electron micrographs of the L-type gold nano spiral fiber array, and the appearance of the R-type gold nano spiral fiber array in the electron micrographs is similar to that of fig. 1-4, which is not listed here.
As can be seen from fig. 1 to 4, the gold nano-spiral fiber array is composed of single-strand gold spiral fibers arranged in a regular pattern, and each gold spiral fiber has a diameter of about 10 nm. The pitch of each gold spiral fiber was estimated to be about 50 nm.
FIG. 5 is a circular dichroism spectrum of an L-shaped gold nano spiral fiber array according to a first embodiment of the present invention. In FIG. 5, L-Au NHWs are L-type gold nano-spiral fiber arrays, and R-Au NHWs are R-type gold nano-spiral fiber arrays.
As shown in fig. 5, the L-type gold nanospiral fiber array and the R-type gold nanospiral fiber array have distinct circular dichroism, indicating that the two have opposite chirality.
In this embodiment, in order to illustrate the effect of the gold nano spiral fiber array, the L-shaped gold nano spiral fiber array is used as a substrate material, and a raman spectrometer is used to detect the chiral compound. The method comprises the steps of preparing a sample to be detected of a chiral compound into a solution with a proper concentration, dropwise adding the solution to an L-shaped gold nano spiral fiber array on a silicon substrate, and then placing the silicon substrate in a sample cell of a Raman spectrometer for Raman scattering detection.
FIG. 6 is a Raman spectrum of a mixture of R-limonene and S-limonene detected by using the L-type gold nano spiral fiber array of the first embodiment of the invention.
In FIG. 6, - < 100 > is a sample containing only R-limonene, 100 > is a sample containing only S-limonene, 50 > is a sample having a content ratio of R-limonene to S-limonene of 75:25, 0 > is a sample having a content ratio of R-limonene to S-limonene of 50:50, and 50 > is a sample having a content ratio of R-limonene to S-limonene of 25: 75.
Fig. 7 is a linear fitting graph of raman characteristic peak intensity and chiral enantiomer content percentage obtained by performing raman scattering detection on a mixture of R-limonene and S-limonene by using the L-type gold nano-spiral fiber array of the first embodiment of the present invention. In FIG. 7, the abscissa represents the percentage of chiral enantiomer content (ee value), and the ordinate represents the Raman characteristic peak intensity.
As shown in fig. 6 and 7, when an L-type gold nano spiral fiber array is used to detect a chiral compound, such as limonene, the raman signal intensity is in a direct proportion to the chiral enantiomer ratio in the sample. That is to say, when two limonene samples with unknown isomer contents need to be detected, the L-type gold nano spiral fiber array of the embodiment is used as a substrate material for raman scattering detection, and then the detection result is compared with a linear fitting graph formed by a standard substance, so that the content ratio of S-limonene to R-limonene in the sample to be detected can be calculated.
< example two >
In this embodiment, the same L-shaped gold nano spiral fiber array as in the first embodiment is used as a substrate material to detect cyclohexylglycine, and the preparation method of the L-shaped gold nano spiral fiber array is also the same as in the first embodiment, and is not described herein again.
FIG. 8 is a Raman spectrum of a mixture of L-cyclohexylglycine and D-cyclohexylglycine detected by using the L-type gold nanospiral fiber array according to the first embodiment of the present invention.
In FIG. 8, - (100%) is a sample containing only L-cyclohexylglycine, 100% is a sample containing only D-cyclohexylglycine, - (50%) is a sample having a content ratio of L-cyclohexylglycine to D-cyclohexylglycine of 75:25, 0% is a sample having a content ratio of L-cyclohexylglycine to D-cyclohexylglycine of 50:50, and 50% is a sample having a content ratio of L-cyclohexylglycine to D-cyclohexylglycine of 25: 75.
Fig. 9 is a linear fitting graph of raman characteristic peak intensity and chiral enantiomer content percentage obtained by performing raman scattering detection on a mixture of L-cyclohexylglycine and D-cyclohexylglycine using the L-type gold nanospiral fiber array according to the first embodiment of the present invention. In FIG. 9, the abscissa represents the percentage of chiral enantiomer content (ee value), and the ordinate represents the Raman characteristic peak intensity.
As shown in fig. 8 and fig. 9, when L-type gold nano spiral fiber array is used to detect cyclohexyl glycine, which is a chiral compound, the raman characteristic peak intensity is in direct proportion to the content percentage of chiral enantiomer in the sample. That is to say, when two cyclohexylglycine samples with unknown isomer contents need to be detected, the L-type gold nano-spiral fiber array of the embodiment is used as a substrate material for raman scattering detection, and then the detection result is compared with a linear fitting graph formed by a standard product, so that the content ratio of D-cyclohexylglycine to L-cyclohexylglycine in the sample to be detected can be calculated.
In addition, the inventor also adopts the gold nano spiral fiber array of the first embodiment as a substrate material and detects other chiral compounds by matching with a Raman spectrometer, and finds that the detection method can realize content ratio detection of different conformations.
For example, fig. 10 is a raman spectrum of a mixture of L-phenylglycine and D-phenylglycine using the L-type gold nanospiral fiber array of the first embodiment of the present invention, and fig. 11 is a linear fit graph of raman characteristic peak intensity and percentage of chiral enantiomer content obtained by performing raman scattering detection on the mixture of L-phenylglycine and D-phenylglycine using the L-type gold nanospiral fiber array of the first embodiment of the present invention.
As shown in fig. 10 and 11, when an L-type gold nano spiral fiber array is used to detect a chiral compound, such as phenylglycine, the raman characteristic peak intensity is in direct proportion to the content percentage of the chiral enantiomer in the sample.
Through verification, other various common chiral compounds can be subjected to content ratio detection by combining the gold nano spiral fiber array of the embodiment I with a Raman spectrometer, and the ee value and the characteristic peak intensity of the compounds are in a direct ratio relationship. The chiral compounds verified by the inventors are shown in table 1 below:
table 1 shows that chiral compounds capable of content ratio detection by combining gold nano spiral fiber array with Raman spectrometer
As can be seen from table 1, the chiral compounds capable of detecting the enantiomer content ratio by combining the gold nano spiral fiber array with the raman spectrometer are close to hundreds of pairs, and the chiral compounds have different characteristics. For example, the compounds with single chiral centers and compounds with multiple chiral centers are included in table 1, sorted by number of chiral centers; classified by polarity, polar compounds and non-polar compounds are included in table 1; in addition, table 1 also includes various chiral compounds of different types, such as molecules having chromophoric groups, molecules having no chromophoric groups, macromolecules, small molecules, and biomolecules. As can be seen, as long as the compound has Raman scattering characteristics, the enantiomer content ratio can be detected by combining the gold nano spiral fiber array with a Raman spectrometer.
< example three >
In this embodiment, in order to verify the influence of different preparation conditions on the gold nano-spiral fiber array, different gold nano-spiral fiber arrays are prepared under different conditions, and the gold nano-spiral fiber arrays are used as substrate materials to perform raman scattering detection tests respectively.
In this example, a total of three gold nano spiral fiber arrays were prepared, and the preparation processes of the three gold nano spiral fiber arrays were the same as those in the first example, but the conditions were different, and the following were specifically described:
the first method comprises the following steps: the dosage of the 4-mercaptobenzoic acid in the step S4 is changed to 3.45 mM;
and the second method comprises the following steps: the dosage of the 4-mercaptobenzoic acid in the step S4 is changed to 4.14 mM;
and the third is that: the amount of N-acetyl L-cysteine used in step S4 was changed to 2.76 mM.
FIG. 12 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with the dosage of 4-mercaptobenzoic acid being 3.45mM according to a second embodiment of the invention, and FIG. 13 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with the dosage of 4-mercaptobenzoic acid being 3.45mM according to a second embodiment of the invention.
As shown in FIGS. 12 and 13, when the amount of 4-mercaptobenzoic acid was 3.45mM, the diameter of each gold spiral fiber was about 12nm, and the pitch of each gold spiral fiber was about 60 nm.
FIG. 14 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with 4.14mM 4-mercaptobenzoic acid, and FIG. 15 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with 4.14mM 4-mercaptobenzoic acid.
As shown in fig. 14 and 15, when the amount of 4.14mM of 4-mercaptobenzoic acid was used, the diameter of each gold spiral fiber was about 15nm, and the pitch of each gold spiral fiber was about 75 nm.
FIG. 16 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with the dosage of 4-mercaptobenzoic acid of 2.76mM according to a second embodiment of the invention, and FIG. 17 is a scanning electron microscope micrograph of an L-shaped gold nano spiral fiber array with the dosage of 4-mercaptobenzoic acid of 2.76mM according to a second embodiment of the invention.
As shown in FIGS. 16 and 17, when the amount of 4-mercaptobenzoic acid was 2.76mM, the diameter of each gold spiral fiber was about 7nm, and the pitch of each gold spiral fiber was about 35 nm.
Through raman scattering detection tests, the three gold nano spiral fiber arrays can show the same characteristics as the gold nano spiral fiber array in the first embodiment. Namely, the gold nano spiral fiber arrays obtained under different preparation conditions can be used as a substrate material to be matched with a Raman spectrometer, so that the content ratio detection of enantiomers of chiral compounds with different conformations in a sample to be detected is realized.
< example four >
In order to verify whether other types of metal nano-spiral fiber arrays can also be used for chiral compound detection, the gold-silver nano-spiral fiber array is prepared and used as a substrate material to perform a raman scattering detection test.
In this example, the first four steps of the preparation method of the gold-silver nanospiral fiber array are the same as steps S1 to S4 of the example. The difference is that after step S4, a silver attaching step is performed, specifically as follows:
and (4) placing the gold nano spiral fiber array obtained in the step (S4) into a solution containing 5mM of silver nitrate and 10mM of ascorbic acid, standing for 5 minutes for reaction, taking out, washing with ethanol for three times, and drying to obtain the chiral gold-silver nano spiral fiber array.
Fig. 18 is a raman spectrum of a mixture of R-limonene and S-limonene detected by using the gold-silver nano-spiral fiber array of the third embodiment of the present invention, and fig. 19 is a linear fitting graph of raman characteristic peak intensity and chiral enantiomer content percentage obtained by performing raman scattering detection on the mixture of R-limonene and S-limonene by using the gold-silver nano-spiral fiber array of the third embodiment of the present invention.
As shown in fig. 18 and 19, when the gold-silver nano spiral fiber array is used to detect limonene, the raman signal intensity is also in direct proportion to the chiral enantiomer ratio in the sample. That is to say, the gold-silver nano spiral fiber array can also be used as a substrate material to be matched with a Raman spectrometer, so that the content ratio detection of enantiomers of chiral compounds with different conformations in a sample to be detected is realized.
< comparative example >
In order to illustrate the action and effect of the chiral plasmon resonance material of the present invention, the inventor further detected two limonene in the first embodiment by using a common plasmon resonance material and a common raman spectrometer.
Fig. 20 is a raman spectrum of limonene by a general raman spectrometer according to a comparative example of the present invention.
As shown in fig. 20, when a common raman spectrometer (without using a substrate material) is used to detect five limonene samples with the same total content but different ee values, the characteristic peak intensities of the limonene samples are completely the same, which indicates that the common raman spectrometer can qualitatively (by characteristic peak shift) and quantitatively (by characteristic peak intensity) the limonene samples, but cannot distinguish enantiomers, and thus cannot detect content ratios of different conformations. In addition, as can be seen from fig. 20, when the base material is not used, the intensity of the characteristic peak in the raman spectrum is low, and thus there is a problem that the signal is weak and it is difficult to characterize and quantify.
Fig. 21 is a raman spectrum of a comparative example of the present invention in which limonene was detected using a general raman spectrometer and a substrate material having no chirality.
As shown in fig. 21, when a common raman spectrometer and a plasma resonance material without chirality (in this comparative example, gold nanoparticles are used, and the gold nanoparticles are a plasma resonance material but do not have a chiral structure) are used to detect five limonene samples with the same total content but different ee values, the characteristic peak intensity of each limonene sample is overall stronger, but the five raman spectra are also completely the same, which indicates that the common raman spectrometer and the common plasma resonance material without chirality can well realize qualitative and quantitative determination, but cannot distinguish enantiomers, and cannot realize content ratio detection of different conformations.
Examples effects and effects
It can be seen from the above examples that when a chiral plasmon resonance material is used as a substrate material to perform raman scattering detection on a chiral compound, the enhancement effect of raman signals of different enantiomers of the chiral compound is significantly different, and the difference is reflected on a spectrogram, so that the intensities of characteristic peaks of different enantiomers are significantly different. Therefore, the content ratio can be calculated by the intensity of the characteristic peak in the Raman spectrum.
Comparing the first embodiment with the comparative example, it can be seen that when the chiral plasmon resonance material of the present invention is used as a substrate material and a raman spectrometer is used for detecting limonene, limonene samples with different ee values show different characteristic peak intensities, but common substrate materials do not have such characteristics. The inventor speculates that the reason for this phenomenon may be that the gold nano-spiral fiber array with chirality has the characteristics similar to those of chirality under the irradiation of detection light, and can specifically enhance the raman signal of a certain chiral conformation (for example, the L-type gold nano-spiral fiber array has stronger enhancing effect on S-limonene molecules) but has little enhancing effect on another chiral conformation.
In addition, the following results can be obtained from the second and third embodiments: 1. the substrate material of the gold nano spiral fiber array can detect hundreds of chiral compounds; 2. the detection method can realize the detection of chiral compounds even if other kinds of plasma resonance materials with chirality are replaced; 3. chiral plasma resonance materials with different morphologies (such as different diameters and different screw pitches) prepared under different conditions can realize chiral compound detection.
In combination with the inference of the above detection principle, it can be known that the substrate material can perform more or less specific enhancement on the raman signal of the chiral compound as long as the substrate material is a plasmon resonance material having chirality, and thus the detection of the enantiomeric content ratio of the chiral compound can also be realized in combination with the raman spectrometer. The chiral compound can be detected by matching the substrate material with a common Raman spectrometer, so that compared with the chiral compound detection means in the prior art, the method for detecting by combining the substrate material with the Raman spectrometer has the advantages of low cost, simplicity in operation, small interference, accurate result, simplicity in operation, wide application and the like.
The above examples are merely illustrative of specific embodiments of the present invention, and the substrate material for detecting chiral compounds of the present invention is not limited to the scope described in the above examples.
In the examples, the plasmon resonance material having chirality is gold nano spiral fiber array and gold-silver nano spiral fiber array. However, in the present invention, the plasmon resonance material with chirality may also be other kinds of plasmon resonance materials with chirality, including micro-nano material powder or micro-nano film material with a chiral structure composed of metal or metal oxide. Wherein, the metal can be one or a combination of more of gold, silver, copper and platinum, and the metal oxide can be one or a combination of more of copper oxide, titanium oxide, zinc oxide, tin oxide, iron oxide and cobalt oxide; the chiral structure may be a flower-shaped structure, a fan-shaped structure, a propeller-shaped structure, or the like, in addition to the nano-helical fiber structure (i.e., the helical fiber structure) of the embodiment. These materials are all chiral plasmon resonance materials, and can generate an electromagnetic field with chiral characteristics under the irradiation of detection light to specifically enhance a raman signal of a certain chiral conformation, so that the detection of chiral compounds can be realized.
Claims (6)
1. A substrate material for use in detecting a chiral compound for use with a raman spectrometer for detecting the chiral compound, wherein:
wherein the substrate material is a plasmon resonance material composed of a metal or a metal oxide having a chiral structure,
the chiral structure is any one of a spiral fiber structure, a flower-shaped structure, a fan-shaped structure and a propeller-shaped structure.
2. The substrate material for detecting a chiral compound according to claim 1, wherein:
the incident light and the detection light of the Raman spectrometer are unpolarized light.
3. The substrate material for detecting a chiral compound according to claim 1, wherein:
the substrate material is a micro-nano powder material or a micro-nano membrane material.
4. The substrate material for detecting a chiral compound according to claim 3, wherein:
wherein the metal is one or a combination of more of gold, silver, copper and platinum.
5. The substrate material for detecting a chiral compound according to claim 3, wherein:
wherein the metal oxide is one or a combination of more of copper oxide, titanium oxide, zinc oxide, tin oxide, iron oxide and cobalt oxide.
6. The substrate material for detecting a chiral compound according to claim 1, wherein:
wherein the helical fiber structure is composed of a single-strand helix or a double-strand helix,
the diameter of the single-strand spiral and the diameter of the double-strand spiral are 5 nm-20 nm, and the thread pitch is 25 nm-85 nm.
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