Raman spectroscopy technology has a wide range of applications in chemistry, materials, physics, polymers, biology, medicine, geology, and other fields due to its advantages of rich information, simple sample preparation, and minimal interference from water.
01. 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 functional groups. The size, intensity, and peak shape of Raman shift are important criteria for identifying chemical bonds and functional groups. By utilizing polarization characteristics, Raman spectroscopy can also serve as a basis for determining molecular isomers.
The covalent bonds between metal ions and ligands in inorganic compounds often exhibit Raman activity, and Raman spectroscopy can provide information about the composition, structure, and stability of coordination compounds. In addition, many inorganic compounds have multiple crystal structures with different Raman activities, so Raman spectroscopy can be used to determine and identify the crystal structures of inorganic compounds that infrared spectroscopy cannot achieve.
In catalytic chemistry, Raman spectroscopy can provide structural information of the catalyst itself and surface species, and can also be used for real-time study of the catalyst preparation process. Meanwhile, laser Raman spectroscopy is an important method for studying the structure and properties of electrode/solution interfaces, which can delve into fundamental issues such as electrochemical interface structure, adsorption, and reaction at the molecular level and be applied in fields such as electrocatalysis, corrosion, and electroplating.
02. Application of Raman Spectroscopy in Polymer Materials Research
Raman spectroscopy can provide many important information about the structure of polymer materials. Such as molecular structure and composition, stereoregularity, crystallization and orientation, molecular interactions, as well as surface and interface structures. The width of Raman peaks can characterize the stereochemical purity of polymer materials. For samples with irregular positions or mixed head head and tail structures, the Raman peak is weak and wide, while highly ordered samples have strong and sharp Raman peaks.
The research content includes：
(1) Chemical structure and stereoisomerism determination: Skeleton structures such as C=C, C-C, S-S, C-S, N-N in polymers are highly sensitive to Raman spectroscopy and are commonly used to study the chemical composition and structure of polymers.
(2) Quantitative analysis of components: Raman scattering intensity is linearly related to the concentration of polymer, which brings convenience to the analysis of polymer component content.
(3) Characterization of crystalline and amorphous phases, as well as monitoring of polymer crystallization process and crystallinity.
(4) Dynamics process research: Dynamics processes associated with polymer reactions such as polymerization, cracking, hydrolysis, and crystallization. Some characteristic spectral bands of the corresponding Raman spectrum will have intensity changes.
(5) Polymer orientation research: The anisotropy of polymer chains inevitably leads to anisotropy in light scattering. Measuring the Raman band depolarization ratio of molecules can provide important information on molecular configuration or conformation.
(6) Study on the compatibility and molecular interactions of polymer blends.
(7) Monitoring of stress relaxation and strain processes in composite materials.
(8) Monitoring of polymerization reaction process and polymer curing process.
03. Application of Raman Spectroscopy in Materials Science Research
Raman spectroscopy is a powerful tool for studying material structure in materials science, and can do a lot of work in topics such as phase composition interfaces and grain boundaries. including:
(1) Raman study of thin film structural materials: Raman spectroscopy has become a detection and identification method for CVD (chemical vapor deposition) preparation of thin films. Raman spectroscopy can be used to study the structures of single, multiple, micro, and amorphous silicon, as well as the structures of layered films such as boronated amorphous silicon, hydrogenated amorphous silicon, diamond, and diamond-like carbon.
(2) Research on superlattice materials: The stress of the strain layer can be calculated by measuring the Raman frequency shift of the strain layer in the superlattice, and the integrity of the lattice can be determined based on the symmetry of the Raman peaks.
(3) Research on semiconductor materials: Raman spectroscopy can measure the damage distribution of semiconductors after ion implantation, as well as the composition of semi magnetic semiconductors, the mass of epitaxial layers, and the carrier concentration of mixed components in epitaxial layers.
(4) Raman Study of Phase Structure of High Temperature Resistant Materials.
(5) Raman study of all carbon molecules.
(6) Research on quantum size effect of nanomaterials.
04. Application of Raman Spectroscopy in Biological Research
Raman spectroscopy is a powerful tool for studying biomolecules. Due to the weak Raman spectra and simple spectra of water, Raman spectroscopy can study the structure and changes of biomolecules in a near natural and active state.
Raman spectroscopy of biomolecules can simultaneously provide valuable information：
(1) Protein secondary structure: alpha helix, beta fold, random curl, and beta rotation.
(2) Protein main chain conformation: amide I, III, C-C, C-N stretching vibration.
(3) Protein side chain conformation: The side chains of phenylalanine, tyrosine, and tryptophan, as well as the conformations and forms of the latter two, vary with their microenvironment.
(4) Carboxyl, thiol, S-S, C-S conformational changes that are sensitive to conformational changes.
(5) The phenomenon of rotational isomerism of fatty acid carbon hydrogen chains in biofilms.
(6) The structure of DNA molecules and their interactions with other molecules.
(7) Study the interaction, structure, and composition of lipids and biofilms.
(8) Provide important information on the interaction between proteins and lipids in biological membranes.
05. Application of Raman Spectroscopy in Traditional Chinese Medicine Research
Various Chinese herbal medicines reflect differences in Raman spectra due to their different chemical compositions. The applications of Raman spectroscopy in the study of Chinese herbal medicine include:
(1) Analysis of Chemical Components in Chinese Herbal Medicine
Thin layer chromatography (TLC) can effectively separate Chinese herbal medicine but cannot obtain structural information of each component compound, while surface enhanced Raman spectroscopy (SERS) has the advantages of narrow peak shape, high sensitivity, and good selectivity, which can detect the chemical components of Chinese herbal medicine with high sensitivity. The combination of TLC separation technology and SERS fingerprinting identification is a new method for in situ analysis of Chinese herbal ingredients using TLC.
(2) Non destructive identification of Chinese herbal medicines
Due to Raman spectroscopy analysis, there is no need to destroy the sample, making it possible to perform non-destructive identification of Chinese herbal samples, which is particularly important for the study of precious Chinese herbs.
(3) Research on the Stability of Traditional Chinese Medicine
The use of Raman spectroscopy to dynamically track the deterioration process of Chinese herbal medicine has a direct guiding role in predicting the stability of Chinese herbal medicine and monitoring its quality.
(4) Optimization of Traditional Chinese Medicine
For the complex mixture system of Chinese herbal medicine, traditional Chinese patent medicines and simple preparations and compound medicine, it does not need any separation and extraction of ingredients to directly interact with bacteria and cells. The Raman spectrum is used to collect the spectrogram of bacteria and cells without damage, observe the degree of damage of bacteria and cells, study their pharmacological effects, and optimize Chinese herbal medicine, traditional Chinese patent medicines and simple preparations and prescription.
06. Application of Raman Spectroscopy in Gemstone Research
Raman spectroscopy technology has been successfully applied in the fields of gemological research and gemstone identification. Raman spectroscopy technology can accurately identify the inclusions inside gemstones, provide information on the origin and origin of gemstones, and can effectively, quickly, non destructively, and accurately identify the types of gemstones - natural gemstones, artificially synthesized gemstones, and optimized processed gemstones.
(1) Application of Raman Spectroscopy in the Study of Gemstone Inclusions
Raman spectroscopy can be used for qualitative and quantitative detection of the chemical composition of gemstone inclusions. By using Raman spectroscopy technology to study the characteristics of inclusions within minerals, information about the genesis and origin of gemstone minerals can be obtained.
(2) Application of Raman Spectroscopy in Gem Identification
The micro area of Raman spectroscopy testing can reach 1-2um, which has significant advantages in gemstone identification. It can detect extremely small impurities, microscopic inclusions, and artificial dopants in gemstones, and can meet the non-destructive and rapid requirements for gemstone identification.
In addition, the confocal design of Raman microscopy enables the detection of samples at different depths without damaging them, while eliminating interference from samples at other depths, thus obtaining true information of samples at different depths. This is particularly useful in analyzing multi-layer materials. Confocal Raman spectroscopy technology has excellent spatial resolution, which enables the acquisition of changes in species molecules during interface processes, corresponding species distributions, and adsorption orientations of species molecules in different regions of the interface.
Raman spectroscopy has a unique advantage in the study of cultural relics
Raman spectroscopy is a molecular spectroscopic analysis method based on Raman scattering. The cultural relics industry chose Raman because of its unique advantage - non-destructive. Moreover, Raman spectroscopy samples have low demand, high spatial resolution, and simple detection process, and are increasingly being applied in the field of cultural relic research.
Analysis direction of Raman spectroscopy
Raman spectroscopy analysis technology is a molecular structure characterization technique based on the Raman effect, and its signal comes from the vibration and rotation of molecules. The analysis directions of Raman spectroscopy include:
Qualitative analysis: Different substances have different characteristic spectra, so qualitative analysis can be conducted through spectra.
Structural analysis: The analysis of spectral bands is the basis for conducting material structure analysis.
Quantitative analysis: Based on the characteristics of the absorbance of a substance in the spectrum, it can have good analytical ability for the amount of substance.
Advantages and disadvantages of Raman spectrometer for analysis
1. The advantages of Raman spectroscopy for analysis
The Raman spectroscopy analysis method does not require pre-treatment of the sample, nor does it have a sample preparation process, which avoids the generation of some errors. It also has the advantages of easy operation, short measurement time, and high sensitivity in the analysis process.
2. Shortcomings of Raman Spectroscopy in Analysis
(1) Raman scattering area.
(2) The overlap of different vibration peaks and Raman scattering intensity are easily affected by factors such as optical system parameters.
(3) The interference of fluorescence phenomenon on Fourier transform Raman spectroscopy analysis.
(4) Nonlinear curves often occur during Fourier transform spectroscopy analysis.
(5) The introduction of any substance will cause some degree of pollution to the measured system, which is equivalent to introducing the possibility of some errors and will have a certain impact on the analysis results.