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

Surface-enhanced Raman scattering (SERS) offers a tremendous multiplexing capacity for the selective detection of biomolecules in targeted research. SERS labels comprising self-assembled monolayers (SAMs) of Raman reporter molecules on the surface of metal nanoparticles are sensitive and robust probes. Advantages of a SAM include maximum sensitivity, minimal unwanted co-adsorption of molecules from the surroundings, and reproducible SERS spectra with only few dominant Raman bands—all of these independent of a particular SERS substrate. We demonstrate experimentally how to increase the multiplexing capacity of SERS labels by using mixed SAMs with up to three different Raman reporter molecules on the surface of the metal colloid. Type and stoichiometry of a particular Raman label in a multi-component SAM are additional parameters compared with one-component SAMs. All one-, two-, and three-component SAMs on gold nanospheres can be easily discriminated, either by their original SERS spectra or the corresponding bar codes.

Multiplexing with SERS labels using mixed SAMs of Raman reporter molecules.

A multilayer quasi-continuous density gradient centrifugation method for separating 20-250 nm metal colloids with high size resolution while maintaining particle stability is presented. Colloidal mixtures containing monodisperse gold nanospheres and clusters thereof, in particular, gold dimers, are purified with yields up to 94%. The rapid method uses standard laboratory equipment.

Fast and Cost‐Effective Purification of Gold Nanoparticles in the 20–250 nm Size Range by Continuous Density Gradient Centrifugation

Die oberflachenverstarkte Raman-Spektroskopie (SERS) hat sich in den letzten Jahrzehnten zu einer ausgereiften schwingungsspektroskopischen Technik entwickelt, und die Zahl der Anwendungen in der Chemie, den Material- und insbesondere den Lebenswissenschaften steigt rasant. Dieser Aufsatz erklart die theoretischen Grundlagen von SERS in einem kurzen Tutorium und fasst – basierend auf Ergebnissen aus Originalarbeiten der letzen Jahre – wichtige fundamentale Aspekte, die fur das Verstandnis von SERS wichtig sind, zusammen. Daran schliest sich ein Abschnitt uber neuere Ansatze zur Synthese und Praparation plasmonischer Nanostrukturen an. Chemische Anwendungen von SERS bilden das Herzstuck des Aufsatzes. Sie decken eine breite Spanne an Themen ab, von der Katalyse und Spektroelektrochemie bis hin zur Einzelmolekuldetektion und (bio)analytischen Anwendungen.

Oberflächenverstärkte Raman‐Spektroskopie: Konzepte und chemische Anwendungen

Self-assembled monolayers (SAMs) of Raman reporter molecules adsorbed to the surface of metal nanoparticles are labelling agents for the selective detection of biomolecules by surface-enhanced Raman scattering (SERS). Advantages of SAM-based SERS labels include maximum coverage with Raman reporter molecules combined with their uniform molecular orientation within the SAM as well as minimal co-adsorption of other molecules from the surrounding. Water solubility and stability together with the option for controlled bioconjugation are desired properties of SERS labels. We present an approach to synthesize hydrophilic SERS labels in which the colloidal particle is stabilized by two different ethylene glycols attached to the SAM. This guarantees water solubility, independent of the type of a particular Raman reporter molecule and its properties at the SAM/solvent interface. Our dual SAM design is based on two different ethylene glycol spacers covalently bound to the same type of reporter molecule: a short monoethylene glycol (MEG-OH) and a longer triethylene glycol (TEG-COOH) moiety. The terminal carboxy group of the TEG spacer allows subsequent conjugation to biomolecules such as antibodies. Controlled bioconjugation is possible by varying the stoichiometric ratio of both spacers. Finally, dual SAM SERS labels are used in immuno-SERS microscopy for selective imaging of prostate-specific antigen in the epithelium of biopsies from patients with prostate cancer.

Water soluble SERS labels comprising a SAM with dual spacers for controlled bioconjugation

Quantitative and accurate detection of multiple biomarkers would allow for the rapid diagnosis and treatment of diseases induced by pathogens. Monoclonal antibodies are standard affinity reagents applied for biomarkers detection; however, their production is expensive and labor-intensive. Herein, we report on newly developed nanoyeast single-chain variable fragments (NYscFv) as an attractive alternative to monoclonal antibodies, which offers the unique advantage of a cost-effective production, stability in solution, and target-specificity. By combination of surface-enhanced Raman scattering (SERS) microspectroscopy using glass-coated, highly purified SERS nanoparticle clusters as labels, with a microfluidic device comprising multiple channels, a robust platform for the sensitive duplex detection of pathogen antigens has been developed. Highly sensitive detection for individual Entamoeba histolytica antigen EHI_115350 (limit of detection = 1 pg/mL, corresponding to 58.8 fM) and EHI_182030 (10 pg/mL, corres...

https://pubs.acs.org/doi/pdf/10.1021/ac5027012

Sebastian Schlücker

Papers

Multiplexing with SERS labels using mixed SAMs of Raman reporter molecules.

Fast and Cost‐Effective Purification of Gold Nanoparticles in the 20–250 nm Size Range by Continuous Density Gradient Centrifugation

Oberflächenverstärkte Raman‐Spektroskopie: Konzepte und chemische Anwendungen

Water soluble SERS labels comprising a SAM with dual spacers for controlled bioconjugation

Duplex Microfluidic SERS Detection of Pathogen Antigens with Nanoyeast Single-Chain Variable Fragments