Surface Enhanced Raman Spectrum of Nanometric Molecular Systems

Abstract

Surface-enhanced Raman spectroscopy (SERS) was demonstrated to be a useful and sensitive structural spectroscopic tool for the characterization of different types of supramolecular architectures, ideally suited for trace analysis. SERS spectra allowed to distinguish cell membrane components of the biomining bacterium Acidithiobacillus ferrooxidans and their physical and chemical variations caused by different growth media. Several SERS spectral modifications were arguments to propose different structures for two isolated model blue cooper proteins, i.e., hemocyanins belonging to mollusc Concholepas concholepas (CCH) and Megathura crenulata (KLH). The complex structure of a humic acid was demonstrated to be highly sensitive to the pH of the medium; a globular conformation predominated at lower pH, while a decurled structure was observed at higher pH. Finally, the SERS technique using different excitation laser lines allowed to characterizing a carbon nanotube as a single-walled species, with metallic electronic characteristics; these species coexisted with different diameters.