Enhanced Raman spectroscopy: Single molecules or carbon?

The analysis of single molecules instead of a molecular ensemble provides a more detailed insight into molecular states and environment. Surface- and also tip-enhanced (resonance) Raman spectroscopy are becoming an interesting alternative to, in this respect, commonly employed fluorescence spectroscopy because of the much richer spectral information that is obtained from unmodified, label-free species. However, sometimes it is difficult to distinguish between the target molecule and contamination or decomposition of the sample, and unfortunately, it is not always ensured that the observed Raman features actually stem from the investigated species. The important question that arises in enhanced Raman studies addressed here is how to distinguish between the target molecule and the carbonaceous species.