by Raman spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light, usually from a laser source. Incoming monochromatic radiation interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The laser light may be shifted to higher energy, and the difference in energy between the incident and shifted light is equal to the energy of a vibration mode in the molecule. This shift provides information about the vibrational modes in the system. The shift in energy gives information about the vibrational modes in the system.
Applications in Different Fields
Material Science: It has proven to be an extremely useful technique for materials characterization. It can be used to identify minerals, carbon forms like diamond and graphene, measure film thickness, degree of crystallinity, crystal orientation and other structural properties. Its non-destructive nature makes it suitable for in situ analysis of materials under varying conditions like temperature, pressure etc. allowing better understandings of structure-property-performance relationships.
Pharmaceutical: Pharmaceutical industries employ it for polymorph screening, blending uniformity analysis, and counterfeit drug detection. It can help accurately identify active pharmaceutical ingredients and excipients in drugs and supplements. This aids in quality control, process monitoring and formulations development. Non-invasive Raman spectroscopy integrated into tablets and capsules offers opportunities for real-time drug release monitoring and authentication.
Chemistry: In chemistry, it is widely utilized for molecular fingerprinting and identification of compounds. Specific vibrational modes of chemical bonds allow differentiation of structural isomers and conformers that are not distinct by infrared spectroscopy. It is useful for analyzing impurities, reaction monitoring and studying equilibrium and kinetics of chemical reactions. Surface-enhanced Raman scattering (SERS) drastically enhances weak Raman signals for ultra-sensitive detection of molecules.
Biology and Medicine: Biomedical applications of Raman spectroscopy have increased enormously in the last two decades. It serves as a label-free diagnostic tool by providing biochemical fingerprint of tissues and cells. Raman micro-spectroscopy and imaging enables non-destructive investigation of live cells and tissues for disease screening, pharmaceutical testing and toxicology. Raman endoscopic probes help visualize in vivo samples for medical diagnostics. SERS has potential for ultra-sensitive detection of biomarkers in complex biofluids and disease diagnostics.
Art and Archaeology: Cultural heritage science deploys Raman microscopy and hyperspectral imaging solutions to characterise pigments, dyes and other materials used in paintings, manuscripts, pottery, etc dating back hundreds or thousands of years. This aids preservation efforts and deters art forgery. In situ, non-invasive analysis provides insights into artwork provenance and evolution. Similar techniques are useful in archaeological prospecting of ancient tools, gems, glasses and help establish chronology and migration patterns.
Forensics: Identification of unknown trace substances is a critical forensic problem. It serves this purpose well with its fingerprinting capabilities. Databases of Raman spectra make it easy to identify questioned materials like explosives, narcotics, fibers, paints, soils that could link evidence to persons or places. Portable Raman devices enables rapid on-site examination of unknowns and swabs. Raman microscopy and imaging allows examination of samples otherwise invisible to the naked eyes.
Challenges and Advancements
A major drawback of conventional Raman spectroscopy is its weakness, with only about 1 in every 10 million photons undergoing Raman scattering. This necessitated long acquisition times or strong laser sources making it unsuitable for certain applications. Developments in instrumentation and new techniques have significantly enhanced sensitivity of Raman systems.
Introduction of Fourier transform Raman allowed collection of weak Raman signals more efficiently using an interferometer approach. Confocal Raman microscopy utilizing tiny pinholes enables high resolution 3D mapping of materials. Resonance Raman exploits resonance enhancement when laser wavelength matches electronic transitions. Surface-enhanced Raman scattering magnifies signals using nanostructured metal substrates or colloidal solutions of noble metal nanoparticles. Coherent anti-Stokes Raman scattering is a powerful nonlinear variant amplifying weak Raman signals. Raman endoscopy and microscopy probes help overcome depth penetration challenges in clinical diagnosis and surgeries. Widely tuneable lasers, imaging spectrometers, charge-coupled devices and networked data processing servers enable high-throughput hyperspectral Raman imaging and mapping of large samples. Advances in miniaturization have led to emergence of portable Raman spectrometers and microspectrometers facilitating field analysis and process monitoring. Better understanding of instrumentation parameters and multivariate data analysis methods address quantification challenges. Overall, rapid advancements in Raman techniques are expected to open avenues for many new applications across science, healthcare and technology.
Raman spectroscopy is an analytical technique with diverse applications across various scientific domains owing to its non-destructive molecular fingerprinting capabilities. Advancements in instrumentation are enhancing sensitivity, speed and portability of Raman systems to address newer challenges. It enables addressing questions like material identification, chemical structure, polymorphism, kinetics, phase transitions, structural changes etc. Emerging areas like SERS, CARS, TERS and other variants further improve detection limits. Integration of Raman techniques with microscopy and endoscopy expands biological and medical applications. Global availability of portable and handheld systems is enabling applications in field analysis, remote sensing and process monitoring. With continuous innovation, Raman spectroscopy is poised to revolutionize a wide range of fields including healthcare, pharmaceuticals, safeguards, cultural heritage preservation and scientific research.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
