Vibrational and structural dynamics of graphyne

Graphyne (GYs) is a class of 2D carbon allotropes with highly π-conjugated structure consisting of sp- and sp2-hybridized carbon atoms, leading to unique molecular configuration and electronic structure, showing excellent electrical, mechanical, photoelectric and semiconducting properties, and having great potentials in gas–separation, chemical-reaction catalysis, energy–storage, and sensor applications. GYs can be classified into several structural forms, including graphdiyne (GDY) and graphtriyne (GTY). Structural characterisation is crucial for understanding the relationship between their structure and properties. At present, quite a few experimental methods, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nuclear magnetic resonance, infrared and Raman spectroscopies, have been used to characterise the structure of GYs. This review focuses on the structural and vibrational characterisations of GYs using Infrared (IR) and Raman spectroscopies. The vibrational signature, including linear and nonlinear IR characteristics of the periodically appearing C≡C bond, will be reviewed. The intensity enhanced C≡C stretching mode as an IR marker in monitoring vibrational energy redistribution and transfer in GYs will be discussed. This review will shed light on the understanding of the structures and structural distributions, and vibrational energy-transfer pathways of the GY systems, which are important for their design, fabrication and applications.