A non-dispersive Raman D-band activated by well-ordered interlayer interactions in rotationally stacked bi-layer Graphene

Raman measurements on monolayer graphene folded back upon itself as an ordered but skew-stacked bilayer (i.e. with interlayer rotation) presents new mechanism for Raman scattering in sp2 carbons that arises in systems that lack coherent AB interlayer stacking. Although the parent monolayer does not exhibit a D-band, the interior of the skewed bilayer produces a strong two-peak Raman feature near 1350 cm-1; one of these peaks is non-dispersive, unlike all previously observed D-band features in sp2 carbons. Within a double-resonant model of Raman scattering, these unusual features are consistent with a skewed bilayer coupling, wherein one layer imposes a weak but well-ordered perturbation on the other. The discrete Fourier structure of the rotated interlayer interaction potential explains the unusual non-dispersive peak near 1350 cm-1

Controlling nanothread backbone structure through precursor design

Nanothreads are 1D carbon-based nanomaterials produced by pressure-induced polymerization of multiply unsaturated (and typically aromatic) precursors with multiple bonds between adjacent precursors. We computationally design non-covalent interactions between functional groups on thread-forming monomers to control the relative stabilities of different nanothread backbones. In particular, functionalized furan or thiophene precursors are identified that favor nanothreads with oxygen or sulfur atoms arrayed along the same side of the thread backbone, rather than on alternating sides as currently seen experimentally for threads formed from unfunctionalized furan or thiophene. This heteroatom chain provides opportunities for unusual properties arising from a sterically compressed one-dimensional chain of p orbitals.Comment: 8 pages, 8 figure