M. Brehm, T. Taubner, R. Hillenbrand, and F. Keilmann
Nano letters 6, p.1307 (2006)
We demonstrate that scattering near-field microscopy (s-SNOM) can determine infrared “fingerprint” spectra of individual poly(methyl methacrylate) nanobeads and viruses as small as 18 nm. Amplitude and phase spectra are found surprisingly strong, even at a probed volume of only 10-20 l, and robust in regard to particle size and substrate. This makes infrared spectroscopic s-SNOM a versatile tool for chemical andin the case of proteinsecondary-structure identification.