Circular dichroic spectroscopy measurement system based on linearly polarized light incident on one-dimensional periodic metal groove

Abstract

The invention relates to a circular dichroism measurement system based on the incidence of linearly polarized light to a one-dimensional periodic metallic channel. The circular dichroism measurement system comprises a light source, an adjustable polarizer, a one-dimensional metallic channel structure, a sample flow cell and a spectrograph, wherein the light source can generate continuous light of different wavelengths; the adjustable polarizer is used for modulating the incident non-polarized light to linearly polarized light with opposite symmetric polarization angles; the one-dimensional periodic metallic channel structure enables the incident light to be radiated in the channel and on the surface to generate a locally-enhanced chiral optical field; the sample flow cell is used for loading a liquid chiral sample to be measured and enabling the liquid chiral sample to be measured to flow by the surface of the one-dimensional periodic metallic channel structure at a constant speed when the one-dimensional period metallic channel structure is arranged in the sample flow cell, so that the signal stability in measurement can be guaranteed; and the spectrograph is used for detecting a spectral signal reflected by the one-dimensional periodic metallic channel structure. By virtue of twice incidence of linearly polarized light with opposite symmetric polarization angles to the one-dimensional periodic metallic channel structure, the difference of the reflected signal caused by different absorption light of the measured chiral sample under twice incidence is detected, so that the circular dichroism measurement for the sample can be realized.

Description

technical field [0001] The invention relates to the field of molecular spectroscopy, in particular to a circular dichroism spectrum measurement system based on linearly polarized light incident on a one-dimensional periodic metal groove. Background technique [0002] Chirality is an important feature in the structure of matter, that is, there are three-dimensional mirror enantiomers that cannot overlap. Their molecular formulas are exactly the same, but the configuration of atoms or atomic groups in space is different, and they are mirror images of each other. Many biomolecules such as proteins, DNA, amino acids, etc. cannot coincide with their own mirror images due to their spatial structure and structure characteristics, and we call them chiral molecules. The spatial chiral characteristics of these molecules are directly related to the functions of the molecules, so the chiral analysis of chiral molecules is very important. At present, the most direct and effective techni...

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Problems solved by technology

[0004] It can be seen that the traditional circular dichroism spectrometer has certain deficiencies that limit its wide application

First, it has certain requirements for the sample to be tested. Generally, it needs to put the solution sample into a centimeter-long sample cell for measurement, so it has a minimum requirement for the sample, so it cannot realize the detection of very few chiral samples. measurement; second, since the photoelastic modulator used can only modulate one specific wavelength at a time, the incident light must pass through the monochromator for wavelength scanning, and measure the circular dichroism value at a specific wavelength each time, so that Resulting in increased circular dichroism test times across the broad spectrum

Third, the complex system uses many optical devices, so commercial instruments are expensive and the follow-up maintenance costs are high

Although this scheme is feasible, there are still two very serious deficiencies: First, this scheme has relatively high requirements for sample processing, because the original absorption difference signal caused by chiral molecules itself is very weak, this scheme needs to be processed The mirror images of two mutually mirror-symmetrical samples are measured separately, so it is necessary to ensure that the two samples are strictly symmetrical in shape and in the same size, otherwise the measurement error caused by the sample processing error may overwhelm the original desired signal; the second , this scheme of enhancing circular dichroism spectrum still requires the use of left and right circularly polarized light, and it must be measured with the help of traditional circular dichroism spectroscopy system, so the cost is not reduced, but it is realized with the help of special micro-nano structure Enhanced detection of circular dichroism

[0007] In 2012, Schäferling et al. (Schäferling, Martin, Xinghui Yin, and Harald Giessen. "Formation of chiral fields in a symmetric environment." Opticsexpress 20.24 (2012): 26326-26336.) found that even if linearly polarized light is incident on the square micro-nano Metal sheets can also produce enhanced photoactivity near the four corners, but they have different chiral signs, that is, positive and negative values, so there is no net photoactivity increase overall

However, most of the current schemes for enhancing circular dichroism detection by using micro-nano metal structures must also use left and right circularly polarized light to interact with the sample to detect signals, that is, to use traditional circular dichroism spectrometers, Therefore, the cost of this circular dichroism scheme has not been reduced

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