Application of Raman spectrometer in various field

[literacy chapter] Application of Raman spectroscopy in various fields

Raman spectroscopy technology is widely used in the fields of chemistry, materials, physics, polymers, biology, medicine, geology and so on because of its unique advantages such as rich information, simple sample preparation, and small interference of water

1. Application of Raman spectroscopy in chemical research

Raman spectroscopy is mainly used as a means of structural identification and molecular interaction in organic chemistry. It complements infrared spectroscopy and can identify special structural features or characteristic groups. The magnitude and intensity of Raman shift and the shape of Raman peak are important basis for identifying chemical bonds and functional groups. Using the polarization characteristics, Raman spectroscopy can also be used as a basis for the determination of molecular isomers

in inorganic compounds, the covalent bonds between metal ions and ligands often have Raman activity, so Raman spectroscopy can provide information about the composition, structure and stability of coordination compounds. In addition, many inorganic compounds have a variety of crystal structures, which have different Raman activities. Therefore, Raman spectroscopy can be used to determine and identify the crystal structures of inorganic compounds that cannot be completed by infrared spectroscopy

in catalytic chemistry, Raman spectroscopy can provide structural information of the catalyst itself and the species on the surface, and can also study the preparation process of the catalyst in real time. At the same time, laser Raman spectroscopy is an important method to study the structure and properties of electrode/solution interface. It can deeply study the basic problems of electrochemical interface structure, adsorption and reaction at the molecular level, and can be applied to the fields of electrocatalysis, corrosion, electroplating and so on

2. The application of Raman spectroscopy in polymer materials

Raman spectroscopy can provide many important information about the structure of polymer materials. Such as molecular structure and composition, stereoregularity, crystallization and destination, molecular interaction, and the structure of surface and interface. The width of Raman peak can be used to characterize the stereochemical purity of polymer materials. For example, for random samples or samples with mixed head head and tail structures, Raman peaks are weak and wide, while highly ordered samples have strong and sharp Raman peaks

research contents include:

(1) chemical structure and stereoscopic judgment: C = C, C-C, S-S, C-S, N-N and other skeletons in polymers are very sensitive to Raman spectra, which are often used to study the chemical components and structures of polymers

(2) quantitative analysis of components: Raman scattering intensity has a linear relationship with polymer concentration, which brings convenience to the analysis of polymer component content

(3) characterization of crystalline and amorphous phases and monitoring of polymer crystallization process and crystallinity

(4) kinetic process research: the kinetic processes associated with polymer reactions, such as polymerization, cracking, hydrolysis and crystallization. The intensity of some characteristic bands of the corresponding Raman spectrum will change

(5) polymer orientation research: the anisotropy of polymer chain will inevitably lead to the anisotropy of light scattering. Measuring the Raman band depolarization ratio of molecules can obtain important information about molecular configuration or conformation

(6) study on the compatibility and molecular interaction of polymer blends

(7) monitoring of stress relaxation and strain process of composites

(8) monitoring of polymerization reaction process and polymer curing process

3. Application of Raman spectroscopy in material science

Raman spectroscopy is a powerful tool for the study of material structure in material science, and can do a lot of work in topics such as phase composition interface and grain boundary. Including:

(1) Raman study of thin film structural materials: Raman spectroscopy has become a means of detection and identification of thin films prepared by CVD (chemical vapor deposition). Raman can study the structure of single, multi, micro and amorphous silicon, as well as the structure of layered films such as boronized amorphous silicon, hydrogenated amorphous silicon, diamond and diamond-like carbon

(2) superlattice material research: the stress of the strained layer can be calculated by measuring the Raman frequency shift of the strained layer in the superlattice, and the integrity of the lattice can be known according to the symmetry of the Raman peak

(3) research on semiconductor materials: Raman spectroscopy can measure the damage distribution of semiconductors after ion implantation, the components of semi-magnetic semiconductors, the quality of epitaxial layers, and the component carrier concentration of epitaxial layer mixtures

(4) Raman study of phase structure of high temperature resistant materials

(5) Raman study of all carbon molecules

(6) study on quantum size effect of nano materials

4. Application of Raman spectroscopy in biological research

Raman spectroscopy is a powerful means to study biological macromolecules. Because the Raman spectrum of water is very weak and the spectrum is very simple, Raman spectroscopy can study the structure and changes of biological macromolecules in a close to natural and active state

Raman spectra of biological macromolecules can obtain many valuable information at the same time:

(1) protein secondary structure: α- Spiral β- Folding, random curling and β- Rotation

(2) protein main chain conformation: amide I, III, C-C, C-N stretching vibration

(3) protein side chain conformation: side chains of phenylalanine, tyrosine, tryptophan and the latter two conformations and existing forms change with their microenvironment

(4) carboxyl, sulfhydryl, S-S, C-S conformation changes sensitive to conformation changes

(5) fatty acid hydrocarbon chain rotational isomerization of biofilm

(6) DNA molecular structure and the interaction between DNA and other molecules

(7) study the interaction, structure and components of lipids and biofilm

(8) provide important information on the interaction between protein and lipid in biofilm

5. The application of Raman spectroscopy in the study of Chinese herbal medicine

various Chinese herbal medicines reflect the differences of Raman spectroscopy due to the different chemical components contained. The applications of Raman spectroscopy in the study of Chinese herbal medicine include:

(1) chemical composition analysis of Chinese herbal medicine

high performance thin layer chromatography (TLC) can effectively separate Chinese herbal medicine, but it is unable to obtain the structural information of each component compound, while surface enhanced Raman spectroscopy (SERS) has narrow peaks With the advantages of high sensitivity and good selectivity, it can detect the chemical components of Chinese herbal medicine with high sensitivity. The combination of TLC separation technology and SERS fingerprint identification is a new method for in-situ analysis of Chinese herbal medicine components by TLC

(2) nondestructive identification of Chinese herbal medicine

because the Raman spectrum is analyzed by pressing the button, there is no need to destroy the sample, so it can carry out nondestructive identification of Chinese herbal medicine samples, which is particularly important for the research of precious Chinese herbal medicine

(3) study on the stability of Chinese herbal medicine

using Raman spectroscopy to dynamically track the deterioration process of Chinese herbal medicine, which has a direct guiding role in predicting the stability of Chinese herbal medicine and monitoring the quality of Chinese herbal medicine

(4) optimization of traditional Chinese medicine

for the complex mixture system of traditional Chinese medicine and Chinese patent medicine and compound prescription, it does not need any component separation and extraction to directly interact with bacteria and cells. Raman spectroscopy is used to collect the spectrogram of bacteria and cells without damage, observe the damage degree of bacteria and cells, study their pharmacological effects, and carry out the optimization research of traditional Chinese medicine, Chinese patent medicine and prescriptions. It is necessary to replace the tubing with higher intensity

6. Application of Raman spectroscopy in gem research

Raman spectroscopy has been successfully applied to gemmological research and gem identification. Raman spectroscopy can accurately identify the inclusions in gemstones, provide information on the origin and origin of gemstones, and effectively, quickly, nondestructive and accurately identify the types of gemstones - natural gemstones, synthetic gemstones and optimized processed gemstones

(1) the application of Raman spectroscopy in the study of gem inclusions

Raman spectroscopy can be used for the qualitative and quantitative detection of the chemical composition of gem inclusions. Using Raman spectroscopy to study the characteristics of inclusions in minerals can obtain information about the genesis and origin of gem minerals

(2) application of Raman spectroscopy in gem identification

the micro area of Raman spectroscopy can reach um, which has obvious advantages in gem identification. It can detect extremely small impurities, micro inclusions and artificial dopants in gemstones, and can meet the requirements of nondestructive and rapid gem identification

in addition, the confoal design of Raman microscope can detect samples at different depths without destroying the samples, while completely eliminating the interference information of samples at other depths, so as to obtain the true information of samples at different depths, which is very useful in the analysis of multilayer materials. Confocal micro Raman spectroscopy has a good spatial resolution, which can obtain the changes of species and molecules, the corresponding species distribution, and the adsorption orientation of species and molecules in different areas of the interface

7. Raman has a "unique" advantage in the study of cultural relics

Raman spectroscopy is a molecular spectral analysis method based on Raman scattering. The cultural relics community chose Raman precisely because of its "unique" advantage - nondestructive. Moreover, Raman spectrum samples are less in demand, have high spatial resolution, and the detection process is simple. More and more are used in the field of cultural relics research

analysis direction of Raman spectroscopy

Raman spectroscopy analysis technology is a molecular structure characterization technology based on Raman effect. Its signal source is the vibration and rotation of molecules

Raman light traditional mechanical (wire) changes the analysis direction of the physical schematic diagram of the experimental machine:

qualitative analysis: different substances have different characteristic spectra, so qualitative analysis can be carried out through spectra

structure analysis: the analysis of spectral bands is also the basis of material structure analysis

quantitative analysis: according to the characteristics of the absorbance of substances to the spectrum, we can have a good ability to analyze the amount of substances

advantages and disadvantages of Raman spectroscopy for analysis

1. Advantages of Raman spectroscopy for analysis

the analysis method of Raman spectroscopy does not require pretreatment of samples, and there is no sample preparation process, which avoids some errors, and has the advantages of simple operation, short determination time, high sensitivity

2 Shortcomings of Raman spectroscopy for analysis

(1) Raman scattering area

(2) different vibration peak overlaps and Raman scattering intensity are easily affected by factors such as optical system parameters

(3) interference of fluorescence phenomenon on Fourier transform Raman spectroscopy analysis

(4) in Fourier transform spectroscopy analysis, there is often the problem of nonlinear curve

(5) the introduction of any substance will bring some degree of pollution to the measured body system, This is equivalent to introducing the possibility of some errors, which will have a certain impact on the analysis results