Advanced Materials

Martin Bastmeyer and co-workers report on p. 868 the fabrication of elastic structures with submicrometer thickness for cell culture that can be deformed by forces exerted by single cardiomyocytes. The cover illustrates a 3D reconstruction of cardiomyocytes labeled for f-actin (green) and a-actinin (red) growing in an Ormocomp scaffold consisting of posts connected by flexible beams. This method offers the possibility to study cell behavior in a 3D environment with defined geometries and physiologically-relevant stiffness values. Cover artwork by M.S. Rill.

Owing to the absence of dislocation defects and grain boundaries, the amorphous structure of metallic glass possesses superior mechanical properties compared to its crystalline counterparts. Koji Nakayama and co-workers present on p. 872 a method that is capable of producing metallic glass nanowires. The image shows that the free end wire in the center oscillates like a sine-wave pattern implying extremely high elasticity. The authors have succeeded to measure these mechanical properties at the nanoscale.

Elastic 3D scaffolds (see figure) are fabricated into a biocompatible photoresist using direct laser writing. These scaffolds can be rhythmically deformed by single beating cardiomyocytes and calibration with atomic force microscopy indicates that cellular forces down to 10–20 nN are detectable with the setup.

Extraordinary flexible, very long, and individual amorphous nanowires composed of metallic glasses are produced by the drawing process based on superplastic deformation above the glass transition temperature. The outstanding mechanical properties of metallic glasses including low Young's modulus and high strength can be inherited in nanowire.

A defect-free and electronically abrupt polymer/oxide interface can be achieved by spin-coating of PEDOT:PSS on ZnO-based heterostructures. The interface yielding Schottky contact leads to the successful modulation of quantum 2D transport in MgZnO/ZnO interfaces via the electric-field effect, which indicates that the polymer/oxide interface enables a high-mobility field-effect transistor.

A cooperative nanosystem consisting of two distinct nanomaterials works in vivo to detect tumor tissues and deliver drugs to the site. Gold nanorods (GNRs) localize to the tumor region, where they report their location and convert near-infrared radiation to thermal energy. Circulating thermally labile therapeutic liposomes respond to the thermal signal, releasing their drug payload selectively in the GNR-populated tumor.

A new potential utility of glass-forming cholesteric liquid crystal (G-CLC) oligomers for application in tunable solid-state laser is presented. The G-CLC is capable of tuning the photonic band gaps (PBGs) by way of the annealing temperature and preserving the tuned PBGs by a subsequent supercooling treatment. This G-CLC film enables the facile fabrication of a continuously gradated PGB structure and, thus, the continuous tuning of a single laser-emission peak (see figure).

Conductive “alkylated” graphene paper is prepared by post-fabrication modification of graphene oxide paper with hexylamine followed by hydrazine reduction in a one-pot process. The “alkylation” with hexylamine stabilizes the stacked paper structure during the reduction, maintaining its well-ordered morphology and resulting in uniform conductivity and good mechanical properties.

Stenciling graphene, carbon nanotubes, and fullerenes, all of which are in hydrazine, can be stenciled onto substrates using a thin elastiomeric membrane composed of poly(dimethylsiloxane) (see figure). This method represents a flexible route to stencil a family of carbon nanomaterials and could be used for patterning other solvent dispersed derivatives of fullerenes, carbon nanotubes, and graphenes.

The layer-by-layer formation and characterization of conformally smooth, uniform, and single-crystalline Ge(core)/Si–Ge–Si(multishell) and Si(core)/Ge–Si(multishell) nanowire heterostructures is reported. The modulation of their radial composition is well-defined and there is precise control over a wide range of shell thicknesses regardless of the initial nanowire core diameter.

The fabrication of bulk heterojunction organic solar cells from solution-casting techniques using low-cost materials makes them a promising new technology for converting sunlight into electricity. T.-Q. Nguyen, G. C. Bazan, et al. report on p. E63 that undesirable large-scale aggregation and phase separation that may arise during deposition can be reduced by incorporating a small amount of a well-chosen solvent additive.

The image shows a 3D representation of a new class of macromolecules for organic electronics formed by rigid polymeric backbones (blue) side-functionalized with thousands of polyaromatic, optically active molecules (red). In the background, the real polymer fibers as presented by V. Palermo, K. Müllen, D. Beljonne, R. H. Friend, A. E. Rowan, P. Samorì, et al. on p. E81 are visualized by AFM. The authors thank the ESF-SONS2 programme for financial support.

Recent progress in energy-efficient lighting using polymer white-light-emitting diodes (WPLEDs) and solar-energy production through photovoltaic devices based on poly(2,7-fluorene), poly(2,7-carbazole), and poly(2,7-dibenzosilole) derivatives, three promising classes of conjugated polymers based on bridged phenylenes, is reviewed.

Energy storage materials play a key role in efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energies. Strategies for developing advanced materials for hydrogen storage and electrode materials of lithium-ion batteries and supercapacitors are discussed. Future trends and prospects in the development of advanced energy storage materials are highlighted.

A high-boiling-point additive that favors both poly[(4,4-didodecyldithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzoxadiazole)-4,7-diyl] and PC₇₁BM in a bulk heterojunction solar cell is used to reduce large-scale aggregation and phase separation, which increases device performance. This is in contrast to the majority of high-boiling-point additives that improve performance by increasing phase separation.

Optimized tandem solar cells based on wide-and small-bandgap polymer semiconductor cells reach an efficiency of 4.9%. In this tandem cell the short-circuit current exceeds that of the current-limiting subcell. The recombination layer that connects the two subcells does not impose important losses.

Poly(alkylene biguanides) are novel high-temperature proton conductors. This long-known class of polymers is presented as surprisingly stable high-temperature proton-conducting materials in the form of water-free HCl conjugates. Proton conductivity is dominated by free volume relaxation. Application in the context of fuel-cell membranes is discussed.

Tandem solar cells have the advantage of enhancing the absorption range of polymer solar cells. A three-terminal tandem cell based on two polymer bulk heterojunctions that have complementary absorption profile is demonstrated. In this device configuration the two subcells are connected in parallel through a common semitransparent metal interlayer and an efficiency of 4.8% with short circuit current of 15.1 mA cm⁻² is achieved.

Accurate control over the position of functional groups can be obtained by developing ultrarigid synthetic macromolecular scaffolds exposing the functional groups of choice in the side-chains. This allows fine tuning of the electronic interaction between organic semiconducting moieties: the (opto)electronic properties of these new functional architectures are explored by constructing prototypes of field-effect transistors and solar cells.