A matter of scale: from far-field microscopy to near-field nanoscopy

Vibrational spectroscopy is a powerful analytical tool which provides chemical information about a sample without a priori knowledge. By combining vibrational spectroscopy with different microscopic techniques, scientists can visualize and characterize the chemical composition of a sample on length scales which cover many orders of magnitude; from far-field radiation used in microwave astronomy and Fourier transform infrared microscopy, to near-field scattering used in tip-enhanced Raman spectroscopy and scanning near-field optical or infrared microscopy. Here, various modern chemical mapping techniques are reviewed and their advantages and disadvantages are discussed. Also, a basic theoretical background is provided for each technique along with several illustrative examples.