Moiré patterns and carbon nanotube sorting

Moiré patterns (MPs), arising from the superposition of two lattices with close periods, are tightly related to the physicochemical properties of bilayer nanostructures. Here, we develop the theory of complex MPs emerging in twisted bilayer graphene and planar nets of double-walled nanotubes at significant relative twist and/or deformation of layers. The proposed theory clarifies the physicochemical regularities arising at sorting of single-walled carbon nanotubes (SWCNTs) by organic molecules, which self-assemble in regular coatings on both the tubes and planar graphene. We introduce and consider an outer tubular virtual lattice that is a parent structure for the deposited coating and due to this fact, its existence is crucial for the coating formation. As we show, such outer lattices exist only for successfully sorted SWCNTs and the superposition between the outer lattice and SWCNT forms a specific long-period MP. We explain known experimental results of SWCNT sorting by molecules of flavin group, poly(9,9-dioctylfluorene-2,7-diyl) (PFO), and poly [(m-phenylenevinylene)-alt-(p-phenylenevinylene)] (PmPV). Also, our approach points out other organic molecules and polymers suitable for effective CNT sorting.

Design and modeling of a planar graphene structure as a terahertz cyclotron radiation source

With incredibly high carrier mobility and saturation velocity, graphene would be an ideal candidate for a miniaturized solid-state cyclotron radiation source. A planar semicircular graphene arc geometry was investigated for emission in the 0.5–1.5 THz range. Analytical studies, confirmed by finite element simulations, show that the emitted THz frequencies are inversely proportional to the arc radius given a fixed charge-carrier velocity. The simulations show that the desired frequency spectrum can be obtained with design radii ranging from 50 to 150 nm. Interestingly, the radiated spectrum is independent of the frequency of the stimulation of the graphene nano-arcs. The simulations also indicate that the total output power correlates well with the Larmor formulation. The device is expected to emit 1 nW/cm2, which confirms the findings of existing research in this field. Such a design could yield a scalable and cost-effective THz source.

Design and modeling of a planar graphene structure as a terahertz cyclotron radiation source

With incredibly high carrier mobility and saturation velocity, graphene would be an ideal candidate for a miniaturized solid-state cyclotron radiation source. A planar semicircular graphene arc geometry was investigated for emission in the 0.5 THz to 1.5 THz range. Analytical studies, confirmed by finite element simulations, show that the emitted THz frequencies are inversely proportional to the arc radius given a fixed charge-carrier velocity. The simulations show that the desired frequency spectrum can be obtained with design radii ranging from 50 nm to 150 nm. Interestingly, the radiated spectrum is independent of the frequency of the stimulation of the graphene nano-arcs. The simulations also indicate that the total output power correlates well with the Larmor formulation. The device is expected to emit 1 nW/cm2, which confirms the findings of existing research in this field. Such a design could yield a scalable and cost-effective THz source.

Schwarzite nets: a wealth of 3-valent examples sharing similar topologies and symmetries

We enumerate trivalent reticulations of two- and three-periodic hyperbolic surfaces by equal-sided n -gonal faces, ( n , 3), where n = 7, 8, 9, 10, 12. These are the simplest hyperbolic generalizations of the planar graphene net, (6, 3) and dodecahedrane, (5, 3). The enumeration proceeds by deleting isometries of regular reticulations of two-dimensional hyperbolic space until the ( n , 3) nets can be embedded in euclidean three-space via periodic hyperbolic surfaces. Those nets are then symmetrized in euclidean space retaining their net topology, leading to explicit crystallographic net embeddings whose edges are as equal as possible, affording candidtae patterns for graphitic schwarzites. The resulting schwarzites are the most symmetric examples. More than one hundred topologically distinct nets are described, most of which are novel.