Advanced Materials

Devitrification of bulk metallic glass leads to novel microstructures with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Xun-Li Wang and co-workers report on p. 305 that significant chemical segregation is revealed in unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments.

The cover shows a fluorescent microscopy image of co-assembly of streptavidin functionalized quantum dots (SA-QD) and fluorescein molecules self-assembled using biotinylated and conjugated quartz binding peptides (QBP-bio and QBP-fluorescein). Mehmet Sarikaya and co-workers describe how inorganic binding peptides can act as universal linkers on p. 295. Stamping of the QBP-bio using micro-contact printing is followed by directed assembly of SA-QD (red). The QBP-fluorescein is then immobilized on the bare silica (green) to generate uniform bifunctional micropatterns.

Methods of functionalizing nanoporous carbon materials are reviewed, including direct incorporation of heteroatoms during the carbon synthesis, surface oxidation and activation, halogenation, sulfonation, grafting, attachment of nanoparticles, and surface coating with polymers. Characterization techniques and advanced applications for functionalized nanoporous carbons are also highlighted.

Quartz-binding peptides (QBPs) are used as both ink and linker for microcontact printing and self-assembly, for the co-immobilization of streptavidin-coated quantum dots and fluorescein. Directed assembly of the quantum dots is carried out following microcontact printing of biotinylated QBP1 on a quartz surface. The remaining untouched regions are occupied by the mediated-assembly of fluorescein linked with QBP1.

Orthogonal wettability and topographical gradients in a combinatorial sample format are fabricated using plasma-polymer-coated microgrooved surfaces. Preferred cell proliferation is found on specific combinations of topography and chemistry. This proof-of-concept study demonstrates the potential applications of this sample format for investigating the relationship between multiple surface properties on cellular response in a high-throughput manner.

Devitrification of bulk metallic glass leads to a novel microstructure, with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Significant chemical segregation is revealed at unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mistery for over a decade.

A new photochromic diarylethene, 1,2-bis(5′-ethoxy-2′-(2″-pyridyl) thiazolyl) perfluorocyclopentene (1), is synthesized. Nanoparticles are obtained by laser ablation at both 355 and 532 nm, corresponding to the absorption wavelengths of the open and the closed forms. 1 can be reversibly photoswitched in various states: organic solution, bulk crystal, nanoparticle colloidal solution, and single nanoparticle, as demonstrated by dark-field scattering spectroscopy.

Zero-dimensional nanoparticle structures have a prominent role as building blocks for complex assemblies. However, major barriers to the construction of 1D assemblies using 0D elements exist. The fabrication of free-standing all-nanoparticles thin fibers is presented, where the fibers have a uniform diameter (1.5 µm) and a high aspect ratio (length/diameter ≥ 2500).

A 4-aminothiophenol self-assembled monolayer (see image) is prepared on top of a Au(111) crystal, which is subsequently metallized by a nearly closed Pd overlayer of monoatomic height. Analysis of its structural setup and electronic properties reveals that the monolayer consists of a minimum of two molecular layers, and strong chemical interactions between the metal overlayer and the amino groups are found to play a decisive role in determining the overall electronic, and thus the transport properties, of the layer/metal contact.

Arrays of Si rods are embedded in PDMS and removed from the rigid growth substrate, resulting in a composite material that merges the benefits of single-crystalline silicon with the flexibility of a polymer. With this technique, solar cell absorber materials with the potential to achieve high efficiency can be prepared by high-temperature processing and transformed into a flexible, processable form.

Novel ZrInZnO semiconductor materials to resolve transistor instability for active-matrix organic light-emitting diodes are proposed. The ZrInZnO film is preprared using a cosputtering method, and presents a nanocrystal structure embedded in an amorphous matrix. The thin-film transistors fabricated have good electrical performances as well as excellent stability under long-term bias stresses.

Strain rate effects on the mechanical properties of carbon nanotube forests are studied, and several related interesting new phenomena are reported. Dense vertically aligned foam-like forests of carbon nanotubes are anchored on a thin, flexible polymer layer to provide structural stability, particularly at the higher strain rates. Permanent deformation and for the first time the delamination and crumbling of carbon nanotube walls is observed.

Homoleptic iridium complexes with C^ˆN=N type ligands, i.e., 1,4-bis (phenyl) phthalazine (BPPa) and 3,6-bis(phenyl)pyridazine (BPPya), are strong phosphorescents, easy to synthesize, and thermally stable, thus having great potential in optical electronic applications, as demonstrated in Ir(BPPa)₃-based OLED devices. A quantum chemistry study shows that CˆN=;N type ligands can bond to Ir more strongly.

An organic field-effect transistor able to switch from depletion (normally on) to enhancement (normally off) mode was obtained thanks to the composition of the mixed semiconductor that forms the device channel. The threshold voltage of the device can be predictably tuned from positive to negative values by adjusting the composition of a mixture of sexithiophene derivatives that are able to achieve a perfect intercalation inside the thin film.

Multi-stranded threads are fabricated using AC electrospinning. The threads are 1–100 µm thick and are composed of interconnected ∼100 nm thick nanofiber strands. The ease of collection due to localization of the whipping instability leads to uncomplicated control and placement of the threads. The network structure has high mechanical integrity and allows for use in fabric weaving, filtration, and biomedical applications.

High solid-state quantum efficiency (Φ_PL ≈ 0.90) materials with attractive properties for OLED and laser applications are reported. Our results show that long fluorene chain-lengths are not a necessary prerequisite for efficient solid-state luminescence. Isolated-molecule-like solid-state emission, stable pure-deep-blue electroluminescence, and low-threshold lasing (λ^laser = 437 nm, E_th^laser ≈ 0.4 nJ/pulse, 1.3 µJ cm⁻²) are demonstrated.

A Li₂CO₃-doped water/alcohol-soluble neutral conjugated polymer is used as the electron-injection layer in a solution-processed polymer OWLED with very high efficiency. A maximum forward viewing luminous efficiency of 36.1 cd A⁻¹ and a power efficiency of 23.4 lm W⁻¹ were achieved, values comparable to those reported for the state-of-the-art vacuum deposited small -molecule OWLEDs.

Regenerated silk fibers extruded from fibroin solutions are highly lustrous and have uniform diameters and circular cross-sections. They are stronger, more extensible, and tougher than natural silkworm silk. These fibers can be spun under clean, sterile, and carefully regulated conditions, and may permit direct incorporation of drugs for controlled release, being suitable for biomedical applications.