Two-dimensional (2D) carbon materials such as graphdiyne sheets have drawn much attention in recent years. However, the structural details of chemically synthesized graphdiyne sheets require further undstanding. In this work, typical graphdiyne substructures were designed as model systems with varying molecular size, in order to understand the conjugative effect on the vibrational properties of the C≡C groups that are connected two-dimensionally across such materials and hence may serve as a structural probe for them. Density functional theory predicted an abnormal enhancement in the infrared vibrational transition intensity of the C≡C stretch in large and perfect conjugated system, but not in defected system, which can be understood on the basis of effective electron delocalization and efficient vibrational intensity borrowing. Experimental linear infrared and ultrafast 2D infrared spectroscopies confirmed the enhancement of the C≡C stretch in a model compound, whose ultrafast vibrational excitonic relaxation was observed and characterized on the picosecond time scale by the latter method. Our work provides important spectroscopic measurements for better understanding the structural details and vibrational energy-transfer dynamics of graphdiyne and related 2D carton materials.

Two-dimensional excitonic energy relaxation in carbon material revealed by ultrafast two-dimensional vibrational spectroscopy

255th National Meeting (2018)

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