On the basis of different types of experiments, the authors develop implicitly the model of surface-enhanced Raman scattering (SERS) of adsorbates on metal surfaces. The long-range enhancement by resonances of the macroscopic laser and Stokes field is separated quantitatively from the metal electron-mediated resonance Raman effect. The latter mechanism proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to orbitals of the adsorbates. This model can account for the chemical specificity and vibrational selectivity of SERS and (partly) for the SERS specificity of the various metals.

https://iopscience.iop.org/article/10.1088/0953-8984/4/5/001/pdf

Surface-enhanced Raman scattering

The nature and properties of surface-enhanced vibrational spectra of molecules adsorbed on surfaces that can enhance the absorption and the emission of electromagnetic radiation are discussed. Examples of surface-enhanced resonant Raman scattering, surface-enhanced Raman scattering in the near-infrared and surface-enhanced infrared are given. The rough surfaces used are metal island films coated with a nanometric organic film using the Langmuir-Blodgett technique or deposited by vacuum evaporation.

/pdf/surface-enhanced-vibrational-spectroscopy-2cv91632hb.pdf

Surface enhanced vibrational spectroscopy

This review describes advances made toward the application of surface-enhanced Raman scattering (SERS) in sensitive analysis and diagnostics. In the early sections of this review we briefly introduce the fundamentals of SERS including a discussion of SERS at the single-molecule level. Applications relevant to trace analysis, environmental monitoring, and homeland security and defense, for example high explosives and contaminant detection, are emphasized. Because the key to wider application of SERS analysis lies in the development of highly enhancing substrates, in the second half of the review we focus our attention on the extensive progress made in designing innovative soluble, supported, and ordered SERS-active nano-architectures to harness the potential of this technique toward solving current and emerging analytical tasks. No attempt or claim is made to review the field exhaustively in its entirety nor to cover all applications, but only to describe several significant milestones and progress made in these important areas and to provide some perspective on where the field is quickly moving.

Progress in plasmonic engineering of surface-enhanced Raman-scattering substrates toward ultra-trace analysis.

Surface-enhanced Raman scattering (SERS) is one of the most straightforward applications of the so-called nanoplasmonics. This powerful molecular spectroscopy technique is based on the enhancement of the inelastic scattering from molecules located near nanostructured metallic surfaces when these are illuminated and surface plasmons are excited. The analytical applications of SERS are hindered when the Raman cross-section of the analyte is too low, which is often the case in inorganic molecular species. This problem is even more serious when atomic species are to be identified, since these cannot display a vibrational signal. Herein we discuss the recent advancements toward the SERS detection of small inorganic compounds, including both molecular and atomic species.

SERS Detection of Small Inorganic Molecules and Ions

Solid-state electrolytes are the key to the development of lithium-based batteries with dramatically improved energy density and safety. Inspired by ionic channels in biological systems, a novel class of pseudo solid-state electrolytes with biomimetic ionic channels is reported herein. This is achieved by complexing the anions of an electrolyte to the open metal sites of metal-organic frameworks (MOFs), which transforms the MOF scaffolds into ionic-channel analogs with lithium-ion conduction and low activation energy. This work suggests the emergence of a new class of pseudo solid-state lithium-ion conducting electrolytes.

Creating Lithium-Ion Electrolytes with Biomimetic Ionic Channels in Metal–Organic Frameworks

Raman and infrared spectroscopic studies and conductivity and viscosity measurements of propylene carbonate (PC) doped with various concentrations of lithium perchlorate are reported. The assignment of the vibrational modes was supplemented by AM1 normal coordinate analysis. Both Raman and infrared spectra showed band splitting in the fundamental vibrational frequencies of PC and perchlorate anion. Spectral curve fitting within the totally symmetric perchlorate band shape showed contributions of free ion, solvent-shared ion pairs, and contact ion pairs. Strong Li + -PC interaction was observed for the PC ring deformation band at 112 cm -1 . Ion pairing as deduced by spectroscopic techniques provided a rationale to account for conductivity and viscosity data

Vibrational studies of lithium perchlorate in propylene carbonate solutions

Surface-enhanced Raman spectra and gas chemisorption of Langmuir-Blodgett layers of lutetium and ytterbium diphthalocyanines

The reversibility of the adsorption of NO 2 /N 2 O 4 (NO x ) on a single Langmuir-Blodgett monolayer of phthalocyanine (Pc) complexes is demonstrated using surface-enhanced Raman scattering on Au island films. The effect of the adsorbate on the relative Raman intensity of characteristic vibrational fundamentals of the Pc molecule permits the monitoring of the kinetics and the nature of the small molecule-macrocycle interaction. The localization and strength of the interaction can be correlated with patterns observed in the change of the electronic and resonant Raman spectra in the series of Pc molecules

D. Battisti

Papers

Vibrational studies of lithium perchlorate in propylene carbonate solutions

Surface-enhanced Raman spectra and gas chemisorption of Langmuir-Blodgett layers of lutetium and ytterbium diphthalocyanines

Reversible adsorption on a single Langmuir-Blodgett monolayer

Spectroscopic characterization of rare-earth octa-tert-butylbisphthalocyanine complexes

Gas adsorption and electrical properties of two Langmuir-Blodgett layers of cerium bisphthalocyanine