ABSTRACT
Raman spectroscopy is one of the most promising analytical methods for detection and identification of chemical and biological substances, due to the correspondence of the vibrational Raman frequencies to certain types of chemical bonds. However, due to the very low cross-section of the Raman scattering process, the detection of substances of low concentration is complicated without special enhancement. This is why techniques to enhance the Raman scattering, such as the surface-enhanced Raman scattering (SERS), have been attracting great attention in the last years (Moskovits 2005). Surface-enhanced Raman spectroscopy or surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces or by nanostructures such as plasmonic-magnetic silica nanotubes. The enhancement factor can be as much as 1010 to 1011 (Evan et al. 2007, 2009), which means this technique gives the possibility of single molecule detection (Kneipp et al. 2006; Le Ru et al. 2006). Development of efficient and reliable SERS substrates is especially important for biological analysis applications because Raman spectroscopy provides highly resolved vibrational information at room temperature and does not suffer from rapid photobleaching commonly observed in fluorescence spectroscopy (Chan et al. 2003). For example, today, methods for rapid quantitative medical analysis based on SERS are used already for the analysis of lactic acid in blood (Chiang and Hsu 2005), creatine (Stosch et al. 2005), and real-time and high-sensitivity determination of glucose (Stuart et al. 2005) and drugs (Hellsten et al. 2012).
