ABSTRACT
Raman spectroscopy is a powerful optical spectroscopic method
of chemical analysis with a wide field of applications, ranging
from pharmaceutical and biomedical studies to art and archaeology
[1-3]. These are based on the fingerprint-like information that
it provides by analyzing molecular vibrations. Its capabilities are
however outperformed in several applications where a very high
sensitivity is required, for example, for detecting molecular trace
amounts, mainly due to the very low efficiency of the Raman
scattering process. Surface-enhanced Raman spectroscopy (SERS)
provides the means for improving the sensitivity by amplifying the
original Raman scattering intensity for several up to ten orders of
magnitude. It was more than 30 years ago that an enhanced Raman
signal was observed from molecules adsorbed at roughened silver
electrode surfaces [4, 5]. Since then a huge amount of workwas done
in order to understand its multiple-faceted aspects, and develop
SERS applications, this work being still in progress. Although a big
part of the fundamentals of the technique had been established
in the 1980s, important contributions to the advancements have
been achieved during recent years, in which we have witnessed
an intense blooming in the development of SERS, mainly in direct
relationship with the rising field of plasmonics. In turn, this latter
was boosted by the rapid evolution of nanotechnology in general,
which provided nanofabrication and characterization methods of
continuously increasing performance. Current challenges addressed
in the last years, and ongoing, are both on controlling the fabrication
of SERS substrates with nanoscale precision and on furthering the
current understanding of the details of SERS effects.
