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Material Synthesis and Methodologies
Published in It-Meng Low, Hani Manssor Albetran, Victor Manuel de la Prida Pidal, Fong Kwong Yam, Nanostructured Titanium Dioxide in Photocatalysis, 2021
It-Meng Low, Hani Manssor Albetran, Victor Manuel de la Prida Pidal, Fong Kwong Yam
To enhance the Raman signal, Ag nanoparticles were introduced within the TiO2 nanotube layers to create a surface-enhanced Raman scattering (SERS) effect [100]. Referring to the Raman spectra of the blank and Ag-nanoparticles-deposited TiO2 nanotube layers in Fig. 2.8, the presence of Ag nanoparticles intensified each of the Raman peaks of the nanotube layer. In addition, additional Raman active modes were observed in Ag-deposited layers annealed at both 500 and 700°C, due to the surface selection rules (SSRs) in SERS [101]. To recapitulate, the Raman scattering effect occurs when photons gain or lose energy due to vibrational excitations and a shift in the frequency of the scattered light [102]. The SERS effect is a combination of electronic and chemical SERS, arises when electronic interactions between molecules and metal alter the Raman scattering process. As a result, a total scattering larger than that of the scattering of solely molecules is recorded as an enhanced Raman signal [102].
Fibre Optic Beam Delivery
Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
In addition to the self-focusing effect described earlier, two other non-linear effects, stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), are also observed in fused silica optical fibres with a high peak power. For a full explanation see Nonlinear Fiber Optics by Agrawal [32]. Damage is not a problem with either of these processes; instead, the light is strongly coupled to other wavelengths. Brillouin scattering is an interaction of the laser beam with an acoustic wave, which couples the power into a frequency-shifted beam travelling in the opposite direction to the laser, thus greatly attenuating the light emerging from the output end of the fibre. Raman scattering, meanwhile, is the scattering of a photon from a molecule, with a change in vibrational energy level of the molecule and a consequent increase in the wavelength of the light. With SRS, the scattered beam normally travels in the same direction as the original beam. If a sufficient length of fibre is used, further scattering of the scattered light to longer wavelengths is observed, resulting in a spectrum with a number of broad peaks [33]. Since the scattered light propagates in the same direction as the original laser beam, SRS is not such a problem as SBS in wavelength-sensitive applications, as the power will still emerge from the far end of the fibre. However, the focusing optics at the output end must be free from chromatic aberration over the range of wavelengths produced.
Molecular Vibrational Imaging by Coherent Raman Scattering
Published in Shoogo Ueno, Bioimaging, 2020
Yasuyuki Ozeki, Hideaki Kano, Naoki Fukutake
Raman scattering is an inelastic light scattering phenomenon involving the molecular vibration of substances that interact with light, providing the vibrational spectrum of molecules. It has been applied to biological microscopic imaging to acquire the spatial distribution of biomolecules. However, the intensity of Raman scattering is quite weak, requiring a long acquisition time. Coherent Raman scattering (CRS) microscopy using two-color and/or broadband laser pulses drastically improved the imaging speed and sensitivity of Raman imaging. CRS microscopy can be classified into several types, including coherent anti-Stokes Raman scattering (CARS) microscopy [1,2] and stimulated Raman scattering (SRS) microscopy [3–5]. Recent advancements in the instrumentations of CRS microscopy have drastically enhanced its chemical specificity and imaging speed. Currently, the advantages and disadvantages of CARS and SRS are growing conspicuous: CARS microscopy is advantageous in acquiring broadband vibrational spectra [6,7], whereas SRS is useful for high-speed and sensitive analysis of vibrational spectra in a relatively narrow bandwidth [8–12]. Currently, CRS microscopy is widely applied to label-free imaging of metabolites and drugs in different types of biological cells and tissues. Furthermore, with the recent advent of Raman-detectable labeling technologies, CRS microscopy has been finding novel applications, such as metabolic analysis of small biomolecules [13–15], which were previously difficult with the earlier fluorescent labeling techniques.
Can Tritium Monitoring and Control Requirements for DEMO Be Met by Existing Technologies?
Published in Fusion Science and Technology, 2023
Raman spectroscopy is a method based on the inelastic Raman scattering of laser light off a sample, which can be in gaseous, liquid, or solid form. Raman spectroscopy can distinguish among all six hydrogen isotopologues due to the relatively large mass differences, making it suitable for qualitative measurements, and can be calibrated for taking quantitative measurements. However, it is unsuitable for monatomic species such as helium. Measurement times are typically of the order of seconds, making it suitable for continuous measurements.11 However, to increase accuracy, usually the average of several spectra is taken, increasing the measurement time. Raman spectroscopy is commercially available although developments are needed for gas phase detectors and to ensure tritium compatibility.
Effects on surface-enhanced Raman scattering from copper nanoparticles synthesized by laser ablation
Published in Radiation Effects and Defects in Solids, 2020
Rajesh Rawat, Archana Tiwari, Manish Kumar Singh, R. K. Mandal, A. P. Pathak, Ajay Tripathi
Surface enhanced Raman scattering (SERS) is a highly sensitive vibrational spectroscopy which utilized LSPR property of noble metal NPs to increase the intensity of Raman signal of probe molecules having low inherent Raman signal (4). Because of its highly sensitive and non-destructive nature, SERS has been widely used in various fields such as environmental monitoring, medical sciences, explosive detection and so on (9–12). Mostly Ag and Au NPs or combination of both are widely used candidates for observing SERS phenomena. This is because of their strong LSPR appearance and the stability in time (13,14). Owing to similar LSPR in the visible region, Cu NPs are not preferred in the first choice. This is due to the highly reactive nature of Cu with the ambient atmosphere which hampers its SERS quality. Although, there are several reports of Cu NPs being used as an SERS substrate (1,4), still these lack a proper understanding to comprehend the factors that affect the efficiency of SERS such as effects of size, shape and the method of preparation of Cu NPs. Since Cu is cheaper than Au and Ag and is rich in the earth's crust, we present Cu as a reliable candidate as new SERS substrate with greater stability which can replace these noble metals in wide range of applications.
Distributed fiber optics sensors for civil engineering infrastructure sensing
Published in Journal of Structural Integrity and Maintenance, 2018
The Raman technology utilizes the fact that high-frequency vibration of silica molecules generates inelastic process, in which the photons from the incident light interact with the optical phonons of the material structure (Boyd, 2008). There is an energy transfer between the incident light photon and the material optical phonon. In a simple quantum-mechanical concept, an incident light photon is wiped out to generate a photon with lower frequency (a Stokes wave) and, to conserve, the rest of the energy and momentum forms a phonon in the material structure. Inversely, a higher frequency photon (an anti-Stokes wave) is generated as the phonon provides energy and momentum to satisfy conservation. As a result, the Raman scattering process produces components in a broad band surrounding the exciting (pump) wavelength, containing Stokes (lower photon energy) and anti-Stokes (higher photon energy) emissions, as shown in Figure 12. The Stokes and anti-Stokes of the Raman scattering happens at about ± 13 THz away from the incident light frequency, which is in the order of 193.5 THz for 1554 nm laser.