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The optical properties of metamaterials made by block copolymer self-assembly are tuned by structural and environmental variations. The plasma frequency red-shifts with increasing lattice constant and blue-shifts as the network filling fraction increases. Infiltration with dielectric liquids leads also to a red-shift of the plasma edge. A 300 nm-thick slab of gyroid-structured gold has a remarkable transmission of 20%.

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RESUMEN

The scattering of atomic and molecular beams from well-characterized surfaces is a useful method for studying the dynamics of gas-surface interactions, providing precise information on the energy and momentum exchange which occur in such encounters. We apply this technique to new systems including disordered films of macromolecules, complex interfaces of macromolecular systems, and hybrid organic-semiconductor interfaces. Time-lapse atomic force microscopy studies of diblock copolymer structural evolution and fluctuations complement the scattering data to give a more complete understanding of dynamical processes in these complex disordered films. Our new scattering findings quantitatively characterize changes in interfacial dynamics including confinement in thin films of poly(methyl methacrylate) and changes in the physical properties of poly(ethylene terephthalate) films as they transform from the glassy to their semicrystalline phase. Further measurements on a hybrid organic-semiconductor interface, methyl-terminated silicon (111), reveal that the surface thermal motion and gas-surface energy accommodation are dominated by local molecular vibrations while the interfacial lattice dynamics remain accessible through helium scattering. High temperature atomic force microscopy allows direct, real-time visualization of structural reorganization and defect migration in poly(styrene)-block-poly(methyl methacrylate) films, revealing details of film reorganization and thermal annealing. Moreover, we employed lithographically created channels to guide the alignment of polymer microdomains. This, in turn, allows direct observation of the mechanisms for diffusion and annihilation of dislocation and disclination defects. In summary, this paper elaborates on the power of combining atom scattering and scanning probe microscopy to interrogate the vibrational dynamics, energy accommodation, energy flow, and structural reorganization in complex interfaces.

RESUMEN

As part of an effort to design more efficient dyes for dye-sensitized solar cells (DSCs), structure-property relationships are established in the world's best-performing chemical series of dyes: 2,2'-bipyridyl-4,4'-carboxylatoruthenium(II) complexes. Statistical analysis, based on crystallographic data from the Cambridge Structural Database, is used to determine common structural features and the effects of structural change to its salient molecular constituents. Also included is the report of two new crystal structures for tris(2,2'-bipyridyl)dichlororuthenium(II)hexahydrate and tris(2,2'-bipyridyl)iron(II)dithiocyanate; these add to this statistical enquiry. Results show that the metal (M) core exhibits a distorted octahedral environment with M-N π-backbonding effects affording the propensity of the metal ion towards oxidation. The same characteristics are observed in iron-based analogues. The role of carboxylic groups in this series of dyes is assessed by comparing complexes which contain or are devoid of COOH groups. Space-group variation and large molecular conformational differences occur when COOH groups are present, while such structural features are very similar in their absence. The nature of the anion is also shown to influence the structure of COOH-containing complexes. These structural findings are corroborated by solution-based UV-vis absorption spectroscopy and DSC device performance tests. The presence of COOH groups in this series of compounds is shown to be mandatory for dye-uptake in TiO(2) in the DSC fabrication process. Throughout this study, results are compared with those of the world's most famous DSC dye, N3 (N719 in its fully protonated form): cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II). Overall, the molecular origins of charge-transfer in these complexes are ascertained. The findings have important implications to the materials discovery of more efficient dyes for DSC technology.

RESUMEN

Optical metamaterials have unusual optical characteristics that arise from their periodic nanostructure. Their manufacture requires the assembly of 3D architectures with structure control on the 10-nm length scale. Such a 3D optical metamaterial, based on the replication of a self-assembled block copolymer into gold, is demonstrated. The resulting gold replica has a feature size that is two orders of magnitude smaller than the wavelength of visible light. Its optical signature reveals an archetypal Pendry wire metamaterial with linear and circular dichroism.

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The condensation of linear diamine and dialdehyde subcomponents around copper(I) templates in the presence of bulky trioctylphosphine ancillary ligands gave a linear, conjugated polymeric material in DMSO solution. This polymer solution was observed to undergo sol-to-gel transition as the temperature was raised to 140 °C, in contrast with the behavior of most gel-forming polymers, which do so upon cooling. We attribute the sol-to-gel transition to the formation of Cu(I)N(4) cross-links as the equilibria 2[Cu(I)N(2)P(2)] ⇄ [Cu(I)N(4)] + [CuP(n)](+) + (4 - n)P favor the right-hand side at higher temperatures. The material was also observed to exhibit thermochromism and photoluminescence, with the color and intensity of both absorption and emission exhibiting temperature dependence. This material thus responds predictably to combinations of stimuli (heat, light, mechanical shear) in an interconnected way, as is required to generate complex function.