There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Surface-enhanced Raman scattering (SERS) has become a mature vibrational spectroscopic technique during the last decades and the number of applications in the chemical, material, and in particular life sciences is rapidly increasing. This Review explains the basic theory of SERS in a brief tutorial and-based on original results from recent research-summarizes fundamental aspects necessary for understanding SERS and provides examples for the preparation of plasmonic nanostructures for SERS. Chemical applications of SERS are the centerpiece of this Review. They cover a broad range of topics such as catalysis and spectroelectrochemistry, single-molecule detection, and (bio)analytical chemistry.

Surface-enhanced Raman spectroscopy: concepts and chemical applications.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

/pdf/present-and-future-of-surface-enhanced-raman-scattering-34aqgcm385.pdf

Present and Future of Surface-Enhanced Raman Scattering

https://cyberleninka.org/article/n/894179.pdf

Gold nanoparticles: Optical properties and implementations in cancer diagnosis and photothermal therapy

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Picosecond UV Kerr‐gated Raman Spectroscopy with 280 nm laser excitation

Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task both for modeling and experimental measurements. Here, we present a new implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual nanoparticles (NPs) from a single hyperspectral photoluminescence confocal image. The method is label-free, applicable to any NP with detectable anti-Stokes emission, and does not require any prior information about the NP itself or the surrounding media. With it, we first studied the photothermal response of spherical gold NPs of different sizes on glass substrates, immersed in water, and found that heat dissipation is mainly dominated by the water for NPs larger than 50 nm. Then, the role of the substrate was studied by comparing the photothermal response of 80 nm gold NPs on glass with sapphire and graphene, two materials with high thermal conductivity. For a given irradiance level, the NPs reach temperatures 18% lower on sapphire and 24% higher on graphene than on bare glass. The fact that the presence of a highly conductive material such as graphene leads to a poorer thermal dissipation demonstrates that interfacial thermal resistances play a very significant role in nanoscopic systems, and emphasize the need for in situ experimental thermometry techniques. The developed method will allow addressing several open questions about the role of temperature in plasmon-assisted applications, especially ones where NPs of arbitrary shapes are present in complex matrixes and environments.

In Situ Photothermal Response of Single Gold Nanoparticles Through Hyperspectral Imaging AntiStokes Thermometry

4-Nitrothiophenol (4-NTP) has been widely used in surface-enhanced Raman scattering (SERS)-based reduction studies for testing the catalytic performance of a variety of noble-metal nanoparticles using hydride or hydrogen as reducing agent. The catalytic conversion of 4-NTP to 4-aminothiophenol (4-ATP) strongly depends on the catalyst’s morphology, size, and material composition. This reduction reaction proceeds via a Langmuir–Hinshelwood mechanism, involving the formation of active Pt–H species. Two alternative reaction pathways with respect to the transferred hydrogen species are in principle possible. The first possible pathway describes the direct transfer of a hydrogen radical or hydride to the molecule (hypothesis 1), while the second pathway describes an electron transfer from the platinum to the 4-NTP followed by a proton transfer from the active species (hypothesis 2). To falsify one of these two contradicting hypotheses, we varied the position of the nitro group relative to the thiol groups and thereby the distance of the nitro group to the metal surface. The reduction kinetics of the three isomers of NTP (2-NTP, 3-NTP, and 4-NTP) on platinum-coated gold nanorods was monitored by SERS with molecular hydrogen as the reducing agent. On the basis of the experimental SERS kinetic data giving first-order rate constants in the order k2-NTP > k3-NTP > k4-NTP, we conclude that the reduction does not proceed via an electron transfer mechanism, but via hydrogen/hydride transfer. 

Reduction Kinetics of the Three Nitrothiophenol Isomers on Pt-Coated Gold Nanorods

Composés et marqueurs pour la diffusion Raman de surface améliorée

Toward coherent anti‐Stokes Raman scattering‐Raman optical activity for reaction monitoring in organocatalysis: Chiral vibrational signatures of the two atropisomers (R)‐ and (S)‐MOM‐BINOL in solution

Sebastian Schlücker

Papers

Picosecond UV Kerr‐gated Raman Spectroscopy with 280 nm laser excitation

In Situ Photothermal Response of Single Gold Nanoparticles Through Hyperspectral Imaging AntiStokes Thermometry

Reduction Kinetics of the Three Nitrothiophenol Isomers on Pt-Coated Gold Nanorods

Composés et marqueurs pour la diffusion Raman de surface améliorée

Toward coherent anti‐Stokes Raman scattering‐Raman optical activity for reaction monitoring in organocatalysis: Chiral vibrational signatures of the two atropisomers (R)‐ and (S)‐MOM‐BINOL in solution