Raman Spectroscopy of Nanomaterials
Raman spectroscopy has been used for decades as a powerful tool for variety of materials properties. Under Raman process one understands the inelastic scattering of light by molecular vibrations which results in generation of scattered light at new frequencies which are the combinations of the primary photon frequency and the vibrations. Tip-enhanced Raman spectroscopy originally came as an implementation of Raman near-field scanning optical microscopy, where the optical field is confined to a small aperture at the tip of a metal-coated optical fibre brought extremely close to the sample. Intensity of the electron-udinal optical (LO)-phonon coupling is frequently obtained from the ratio between LO fundamental and overtone Raman signals. Sensitivity of the Raman signal to the particle size follows from the Raman efficiency dependence on the quantum dots size. Confinement of vibrational modes is a key point strongly affecting Raman spectra resulting in their dependence upon average dimensions of the microscrystals.