Plasmonic excitations in two-dimensional materials: effects of structural symmetry and material anisotropy

Plasmonics in two-dimensional materials, an emerging direction of nano-optics, has attracted great attention recently, which exhibits unique properties than that in noble metals. Extending its advanced features by different manipulations is very beneficial for its promotion. In this paper, we study plasmonic excitations in graphene and black phosphorus (BP) nanostructures, where the effects of structural symmetry and material anisotropy are discussed. We show that the two factors are crucial to mode excitations, e.g. the extinction can be dominated by higher order modes rather than dipole resonance. The behavior occurs only in the direction hosting larger resonance frequencies, e.g. armchair (AC) direction of BP and shorter side of graphene rectangles. In BP rectangles along AC direction, the two factors are competing, and thus can be applied cooperatively to tune plasmonic resonance, from dipole to higher order excitations. Besides, the manipulation can also be achieved by designing BP square rings, in which the interaction between outer and inner edges show great impact on mode excitations. Our studies further promote the understanding of plasmonics in two-dimensional materials, and will pave the way for particular plasmonic applications.

Effects of Structural Symmetry on NMR Spectra of 3,9-Diazatetraasteranes

The structural symmetry is of great significance on the unique physical and chemical properties that closely related to pharmacological applications. To investigate the effects of structural symmetry on the NMR spectra, C2-3,9-diazatetraasteranes and non-C2-3,9-diazatetraasteranes were selected as the research object. They were synthesized by the self-dimerization and cross-dimerization of diethyl 1,4-dihydropyridine-3,5-dicarboxylates, respectively. The differences and similarities in NMR spectra of these two types of 3,9-diazatetraasteranes were discussed by the 1D-NMR and 2D-NMR analysis. The single-crystal X-ray diffraction (XRD) was used to demonstrate directly their structural symmetry.

Design and kinematics of a novel double-ring truss deployable antenna mechanism

This paper aims to present the topological structure design and kinematic analysis of a novel double-ring truss deployable satellite antenna mechanism. First, a new topological scheme and a new rectangular prism deployable linkage unit are proposed for constructing the kind of antenna mechanisms. Second, the degree-of-freedom (DOF) of the deployable unit and the antenna mechanism are analyzed based on structure decomposition and screw theory. Third, the kinematic model of the double-ring truss deployable antenna mechanism is established based on its structural characteristics. Finally, a typical numerical example is used to illustrate the effectiveness of the designed mechanism and the established kinematic model. The new double-ring truss deployable antenna mechanism consists of the units with the better structural symmetry, and has simpler joint axis layouts, comparing with the same type of most existing mechanisms.