A concise review of the Raman spectra of carbon allotropes

Raman spectroscopy has developed into a leading tool for characterizing organic materials based on their rotational and vibrational spectral signatures. This article summarises progress to date in the Raman spectroscopy of important new carbon allotropes and nanomaterials, many of which have been synthesised only in the last two decades. This includes allotropes such as carbynes, graphynes, graphdiynes, graphene, graphite, highlyoriented pyrolytic graphite (HOPG), common fullerenes, carbon nanotubes, carbon onions, diamond, lonsdaleite, nanodiamond, ultra-nanocyrstalline diamond (UNCD), amorphous carbon (a-C), tetrahedral amorphous carbon (ta-C), amorphous diamond (a-D), and diamond-like carbon (DLC). Key spectral features are summarised for each carbon allotrope, where experimental data is available. This work aims to provide a useful "field guide" to assist other researchers in identifying new or unusual pure carbon samples.