Raman spectroscopy is a powerful tool to characterize the different types of sp2 carbon nanostructures, including two-dimensional graphene, one-dimensional nanotubes, and the effect of disorder in their structures. This work discusses why sp2 nanocarbons can be considered as prototype materials for the development of nanoscience and nanometrology. The sp2 nanocarbon structures are quickly introduced, followed by a discussion on how this field evolved in the past decades. In sequence, their rather rich Raman spectra composed of many peaks induced by single- and multiple-resonance effects are introduced. The properties of the main Raman peaks are then described, including their dependence on both materials structure and external factors, like temperature, pressure, doping, and environmental effects. Recent applications that are pushing the technique limits, such as multitechnique approach and in situ nanomanipulation, are highlighted, ending with some challenges for new developments in this field. 1. Introduction Raman spectroscopy is the inelastic scattering of light by matter, from molecules to crystals [1]. The effect is highly sensitive to the physical and chemical properties of the scattering material, as well as to any environmental effect that may change these properties. For this reason, the Raman spectroscopy is evolving into one of the most useful tools for the development of nanoscience and nanometrology. Raman spectrometers are widely available; the technique is relatively simple to perform, possible to carry out at room temperature and under ambient pressure, and requiring relatively simple or no specific sample preparation. Optical techniques (if not using high-energy photons) are nondestructive and noninvasive, as they use a massless and chargeless particle, the photon, as a probe, which is especially important for nanoscience due to the large surface-to-volume ratio in nanomaterials. Two-dimensional graphene, one-dimensional carbon nanotubes, and the related disordered materials, here all referred to as sp2 nanocarbons, are selected as the prototype materials to be discussed, first due to their importance to nanoscience and nanotechnology, second because their Raman spectra have been extremely useful in advancing our knowledge about these nanostructures. Nature shows that it is possible to manipulate matter and energy by assembling complex self-replicating carbon-based structures that are able to sustain life. On the other hand, carbon is the upstairs neighbor to silicon in the periodic table, with carbon having more flexible bonding and
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