Biomedical Engineering Reference
In-Depth Information
11
Surface-enhanced raman
Scattering-BaSed Bioimaging
Limei Tian and Srikanth Singamaneni
Department of Mechanical Engineering and Materials Science,
Washington University, St. Louis, MO, USA
11.1
overview
Raman spectroscopy is a unique nondestructive tool for probing the structure and
properties of a wide variety of organic and inorganic materials. Raman spectroscopy
is based on the inelastic scattering of light that provides molecular fingerprint
related to the vibrational, rotational, and other low-frequency transitions of the
molecules [1, 2]. Despite the rich molecular information provided by Raman spec-
troscopy, the technique was not considered to be a handy analytical tool (let alone
imaging tool) due to the extremely weak signal intensity of normal Raman scattering,
a result of the extremely small scattering cross section for most molecules except
some special cases (e.g., resonance Raman scattering). Hence, for the longest period
after its discovery, Raman scattering has remained limited to “bulk” investigations.
Surface-enhanced Raman scattering (SERS), which involves dramatic enhance-
ment of the Raman scattering of an analyte that is adsorbed on or in close proximity
to a metal surface, overcomes the fundamental problem associated with normal
Raman scattering (i.e., weak signal). SERS is emerging as a powerful technique for
the trace-level detection of various biological and chemical species and believed to
make a huge impact on life sciences, environmental monitoring, and homeland secu-
rity [3-9]. Micro-Raman microscopy involves acquiring spatially resolved Raman
spectra by combining the conventional Raman spectrometer with a microscopic tool,
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