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Plasmonic Materials and Their Applications
Published in Song Sun, Wei Tan, Su-Huai Wei, Emergent Micro- and Nanomaterials for Optical, Infrared, and Terahertz Applications, 2023
Jinfeng Zhu, Yinong Xie, Yuan Gao
Tip-enhanced Raman spectroscopy (TERS) is one of the newest Raman techniques, typically combining SERS with scanning probe microscopy (SPM). The electromagnetic field enhancement is strongly confined at the sharp metal tip to boost Raman intensity, providing not only rich spectral and structural information of trace amount of molecules but also a high spatial resolution of 10 nm–20 nm [149,150]. The localized electromagnetic field in the tip-substrate cavity can be enhanced by two orders of magnitude, and the spatial resolution is determined by the radius of curvature of the SPM tip and the tip-substrate distance. Compared with SERS technique which requires the substrate surface to be roughened or nanostructured, TERS naturally bypasses this limitation and obtains a more versatile substrate [151,152]. In addition, TERS combined with electrochemical methods can be used to situ monitor the surface plasmons-driven decarboxylation and resolve the spatial distribution of hot carriers, as shown in Figure 4.12(d), where the electric field distribution shows a very strong field enhancement at the tip (Figure 4.12(e)).
Raman Spectroscopy and Its Implementation
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
While in RRS, the enhancement of the line strength function Φ is influenced by the proximity of the photon energy to an allowed electronic transition, in surface-enhanced Raman spectroscopy—SERS, it is aided by placing the molecule under study in close proximity to a (most often colloidal) metal surface. When exposing this metal substrate to laser light, surface plasmons are excited and the electric fields close to the metal surface are greatly enhanced. Since the Raman process is proportional to the electric field, a large increase in the measured signal can be observed, which can be as large as up to 10 orders of magnitude. In a variant of SERS, known as tip-enhanced Raman spectroscopy—TERS, a metallic ultratip (usually etched from silver or gold wires) is used to push the spatial resolution into the nanoscale, reaching approximately the size of the tip apex of typically 20–30 nm. This is well beyond what can be resolved by “normal” Raman scattering from a diffraction-limited laser spot, which is of the order of 1 μm. Thus, TERS has particular potential for biomedical analysis applications (a few examples will be discussed in Chapter 19).
Raman spectroscopy in biomineralization
Published in Elaine DiMasi, Laurie B. Gower, Biomineralization Sourcebook, 2014
Karen Esmonde-White, Francis Esmonde-White
e future is bright for new applications of Raman spectroscopy in mineralized tissues. We see two exciting trends emerging from the past 5 years of research. The first trend is Raman microscopy approaching nanoscale spatial resolution. Tip-enhanced Raman spectroscopy (TERS) is a technique that adapts surface-enhanced Raman spectroscopy to scanning near- eld optical microscopy (Stockle et al. 2000). The fusion of nanometer spatial resolution with compositional information is a powerful tool for detailed analysis of macromolecular structure. An attractive feature of TERS is the capability to probe secondary structure in precise locations. For collagen, the normally broad amide I would present as discrete bands, enabling detailed characterization of protein secondary structure on the collagen bril surface (Gullekson et al. 2011). Application to mineralized collagen would be expected to yield similarly exciting results. The second trend is translation of Raman spectroscopy toward noninvasive mineral detection in a clinical setting using SORS. Since the first reports in 2006 by Matousek et al. and Schulmerich et al., technological advances in SORS have enabled Raman spectroscopy of buried tissue or layers in highly turbid systems. Measurements of mineral through centimeters of overlying soft tissue are now possible, enabling Raman analysis of bone or mineral without collecting a biopsy. Translation of the SORS technology to clinical use will need to address safety and e cacy requirements that are standard for regulatory approval of medical devices. Pilot clinical studies by us and other groups are establishing laser safety parameters, identifying suitable spectroscopic disease markers, and adapting technology for use in a clinician's office or surgical suite. It is exciting to envision a Raman intraoperative or bedside tool, providing real-time compositional analysis of tissue.
New perspectives on the nature and imaging of active site in small metallic particles: II. Electronic effects
Published in Chemical Engineering Communications, 2021
Recent advances in technology/instrumentation capabilities have led to the development of two other important spectroscopic imaging techniques, which combine vibrational spectroscopy (infrared and Raman) with scanning probe microscopes, to provide imaging at the nanoscale, or, with nanometer-scale resolution. These techniques, which include tip-enhanced Raman spectroscopy (TERS) and infrared scattering-type scanning near-optical microscopy (IR s-SNOM), provide unprecedented sensitivity, spatial resolution and chemical contrast, for nanoscale imaging. TERS provides an ultrasensitive approach for spectroscopic imaging at nanoscale, beyond the diffraction limit. It uses a nanostructured metallic scanning probe microscope tip to confine and enhance the electric field of the incident light at the tip apex, and generate enhanced Raman scattering from molecules within immediate proximity of the tip. By scanning a sample under the TERS tip, a Raman image with chemical-specific information can be obtained with spatial resolution on the scale of the confined near-field (Xiao and Schultz 2018). A novel application of TERS is for mapping the catalytic activities of surfaces and nanostructures with nanoscale spatial resolution. It is also possible to resolve site-specific electronic and catalytic properties of catalytic surfaces. TERS can now be routinely used to investigate heterogeneous catalysis at the nanoscale, with imaging of individual catalytic sites.
Application of SERS on the chemical speciation of individual Aitken mode particles after condensational growth
Published in Aerosol Science and Technology, 2020
Ryota Kunihisa, Ayumi Iwata, Masao Gen, Chak K. Chan, Atsushi Matsuki
These results demonstrated that the combination of the CGT sampler and the SERS substrate has sufficient sensitivity for semi-quantitatively detecting characteristic sulfate and organic signals from individual Aitken mode nanoparticles. Tip-Enhanced Raman Spectroscopy (TERS), which has the advantage of enhanced Raman signal and spatial resolution down to the nanometer scale, has already been applied for nanoparticles smaller than 100 nm in size (Ofner et al. 2016). However, TERS still involves many technical challenges, for example, one must ensure that the excitation laser spot be focused exactly at the probe tip of the scanning probe microscope (SPM) in contact with the analyte. Stable operation of TERS is still not readily achieved and requires highly trained personnel to ensure its reproducibility. In this respect, the proposed method is much quicker, robust and less labor intensive (e.g., does not require additional operation of SPM). Considering the fact that the previous works based on normal Raman and SERS dealt only with accumulation mode particles (>100 nm) or larger (Tirella et al. 2018), the detection of major chemical components from a small volume of nanoparticles as small as 20 nm by SERS can be a significant step forward in our pursuit of developing the more sensitive chemical analysis.