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.
The purpose of this tutorial review is to provide a comprehensive explanation of plasmon-enhanced spectroscopies, such as plasmon-enhanced Raman scattering, fluorescence, absorption, Rayleigh scattering, and hyper Raman scattering. Plasmon-enhanced spectroscopy implies the spectroscopy of enhanced optical responses of molecules in close proximity to plasmonic nanostructures, resulting in a strong enhancement in sensitivity. In this review, we explain the enhancement in plasmon-enhanced spectroscopy as an optical response of a molecule interacting with an optical resonator, which represents a plasmonic nanostructure, in analogy to cavity quantum optics to easily understand all types of plasmon-enhanced spectroscopy in the same manner. The keys to understanding the enhancement factor of each plasmon-enhanced spectroscopy are a quality factor and a mode volume of plasmonic resonators, which are well-known parameters in the Purcell effect of standard optical cavity resonators.
This paper recognizes the contribution of Professor Wilfried Haeberli for his inspiration and leadership in the field of permafrost science and his generous encouragement, both direct and indirect, to the ETH Researchers who have, through him, endeavoured to contribute to this fascinating research area. The multidisciplinary investigations described in this paper have focused on three rock glaciers, Muragl, Murtèl‐Corvatsch and Furggwanghorn, all of which have been subject to a varying degree of prior study, and which are continuing to attract new generations of researchers to understand and explain the processes and predict future behaviour. This paper marks a stage at which it is possible to summarize some advances in the state of the art and associated innovations that can be attributed to early motivation by Wilfried Haeberli and offers a tribute as well as gratitude for his ongoing feedback and advice. Some thoughts on the development of thermokarst due to water ponding and flow, and a conceptual model of geotechnical mechanisms that aim to explain some aspects of rock glacier kinematics, are also introduced.
Surface-enhanced Raman scattering (SERS) and tip-enhanced
Raman
scattering (TERS) have opened a variety of exciting research fields.
However, although a vast number of applications have been proposed
since the two techniques were first reported, none has been applied
to real practical use. This calls for an update in the recent fundamental
and application studies of SERS and TERS. Thus, the goals and scope
of this review are to report new directions and perspectives of SERS
and TERS, mainly from the viewpoint of combining their mechanism and
application studies. Regarding the recent progress in SERS and TERS,
this review discusses four main topics: (1) nanometer to subnanometer
plasmonic hotspots for SERS; (2) Ångström resolved TERS;
(3) chemical mechanisms, i.e., charge-transfer mechanism of SERS and
semiconductor-enhanced Raman scattering; and (4) the creation of a
strong bridge between the mechanism studies and applications.
For single colloidal Ag nanoaggregates, covered with either large or small amounts of citrate anions, blinking surface-enhanced Raman scattering (SERS) of anionic thiacyanine was measured and analyzed by a truncated power law. The power law without and with an exponential function reproduces a probability distribution for bright and dark SERS events versus their duration times, respectively. On the Ag surface, except for junctions of the nanoaggregate with a large or small amount of the citrate anions, two-dimensional fast or one-dimensional slow random walk of the anionic thiacyanine, respectively, was estimated by the exponents and the truncation times in the power law for the dark SERS events. In addition, the power law exponents for the bright SERS events were derived to be of similar values, indicating a similar molecular random walk near the junction, which may be dominated evenly by a surface-plasmon-enhanced electromagnetic field on the same-sized Ag nanoaggregate. Thus, not only the bright SERS, but also the dark SERS molecular behaviour on the Ag surface was investigated by the truncated power law analysis.
The spectral changes in surface-enhanced resonant Raman scattering (SERRS) and surface enhanced fluorescence (SEF) of single silver nanoparticle dimers adsorbed by near-single dye molecules are reproduced under strong coupling regimes. For the reproduction, the enhancement and quenching factors in SERRS and SEF are derived from the Purcell factors including both radiative and nonradiative plasmon modes. The Purcell factors are estimated using the coupling energies obtained by analyzing the spectral changes in plasmon resonance during SERRS and SEF decay processes on the basis of a classical hybridization model. The model is composed of a plasmon and a molecular exciton with phonon replicas accurately representing the molecular multi-level system. The reproduced SERRS spectral changes are consistent with the experimental ones. Furthermore, the calculated SEF spectral changes can reproduce the experimental ones by phenomenologically assuming transitions from ultra-fast SEF to conventional SEF with decreasing coupling energies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.