4 research outputs found
Present and future of surface-enhanced Raman scattering
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
Combined SPR and SERS Microscopy in the Kretschmann Configuration
A novel hybrid spectroscopic technique is proposed, combining surface plasmon resonance (SPR) with surface-enhanced Raman scattering (SERS) microscopy. A standard Raman microscope is modified to accommodate the excitation of surface plasmon-polaritons (SPPs) on flat metallic surfaces in the Kretschmann configuration, while retaining the capabilities of Raman microscopy. The excitation of SPPs is performed as in standard SPR-microscopy; namely, a beam with TM-polarization traverses off-axis a high numerical aperture oil immersion objective, illuminating at an angle the metallic film from the (glass) substrate side. The same objective is used to collect the full Kretschmann cone containing the SERS emission on the substrate side. The angular dispersion of the plasmon resonance is measured in reflectivity for different coupling conditions and, simultaneously, SERS spectra are recorded from Nile Blue (NB) molecules adsorbed onto the surface. A trade-off is identified between the conditions of optimum coupling to SPPs and the spot size (which is related to the spatial resolution). This technique opens new horizons for SERS microscopy with uniform enhancement on flat surfaces
Tamm Plasmon Resonance in Mesoporous Multilayers: Toward a Sensing Application
A novel optical sensor is proposed,
based on the normal-incidence
excitation of Tamm plasmons at the interface between a multilayer
of porous SiO<sub>2</sub> and TiO<sub>2</sub>, acting as a permeable
Bragg reflector, and a flat gold film. Transmittance spectra reveal
a sharp Tamm mode within the stop-band of the distributed Bragg reflector,
the spectral position of which was monitored upon exposure to various
solvents, demonstrating the sensitivity of the device to changes of
refractive index
Interface-Dependent Selectivity in Plasmon-Driven Chemical Reactions
Plasmonic nanoparticles can drive chemical reactions
powered by
sunlight. These processes involve the excitation of surface plasmon
resonances (SPR) and the subsequent charge transfer to adsorbed molecular
orbitals. Nonetheless, controlling the flow of energy and charge from
SPR to adsorbed molecules is still difficult to predict or tune. Here,
we show the crucial role of halide ions in modifying the energy landscape
of a plasmon-driven chemical reaction by carefully engineering the
nanoparticleāmolecule interface. By doing so, the selectivity
of plasmon-driven chemical reactions can be controlled, either enhancing
or inhibiting the metalāmolecule charge and energy transfer
or by regulating the vibrational pumping rate. These results provide
an elegant method for controlling the energy flow from plasmonic nanoparticles
to adsorbed molecules, in situ, and selectively targeting
chemical bonds by changing the chemical nature of the metalāmolecule
interface