Advanced Materials

The striking coloration of the weevil Lamprocyphus augustus is the result of exoskeleton photonic structures with a diamond-based lattice. Michael Bartl and co-workers report on p. 107 on the development of a sol–gel templating method to convert these unique biopolymeric structures into high-dielectric replicas. Theoretical, structural, and optical studies reveal these bioderived photonic crystals possess a complete bandgap at visible frequencies – the basis for novel optical phenomena based on light localization.

The desire exists to develop general biocompatible processes for the organization of unmodified biological systems that capitalize on the numerous highly specific interactions commonly found in nature, including DNA, antibodies, and protein complexes. To this end, on p. 111 Emmanuel Delamarche and co-workers report the fabrication of single virus arrays using the direct printing of unmodified anti-M13 bacteriophage antibodies on silicon with nanometer resolution and widely variable feature pitch.

As society's need for sources of energy continues to skyrocket, materials science is finding itself at the forefront of the search to provide technologies and methods that can meet the demand. As our authors and readers devote ever more effort to finding the answers, Advanced Materials has made a few developments to try and shed a little light on the subject.

Colloidal self-assembly is a well-known technique for the preparation of opal-based photonic crystals. However, it is equally well-suited for the fabrication of photonic glasses, a new photonic material whose principal characteristic is its internal disorder. These solid random dielectrics exhibit rich novel light-diffusion properties originating from the monodispersity of their building blocks. This novel material inaugurates a wide range of photonic materials with intriguing applications, such as resonant random lasers or Anderson localization.

Shrinking device dimensions allow us to probe the intrinsic behavior of organic materials and to improve their FET performance. However, these nanoscale devices still suffer from a number of problems, for example, increased contact resistance and poor large-area π–π stacking within the active layers. Therefore, we suggest that a holistic consideration of the appropriate choice of contact materials, interface structures, and device design may enable the realization of optimized nanoscale organic devices.

On p. 34, Hideo Takezoe and co-workers demonstrate shock-free homeotropic alignment of smectic liquid crystals onto the amorphous perfluoropolymer. The hydrophobic surface of perfluoropolymer as an alignment layer enables spontaneous recovery to the original vertical orientations from deformed smectic layers caused by mechanical shock, such as pressing with tweezers or crystallization.

Perfect homeotropic alignment of smectic liquid crystals is demonstrated using an amorphous perfluoropolymer as an alignment layer (see figure). The hydrophobic surface of the perfluoropolymer allows rapid recovery to the homeotropic orientation from the damaged layer structure caused by mechanical shock— for example pressing with tweezers— or crystallization.

Extraordinarily stable organic glasses are prepared by physical vapor deposition using indomethacin (IMC) or trisnaphthylbenzene. Utilizing Brillouin light scattering (BLS), the elastic moduli of these stable glasses (SG) are found to exceed those of ordinary glass (OG) by up to 19%. Such high-modulus glasses take more than 10⁴ times longer than the structural relaxation time to transform to the supercooled liquid (SCL).

A silver-intercalated fullerene (C₆₀) is fabricated by depositing Ag and C₆₀ simultaneously onto a substrate kept at low temperature (∼23 K), suppressing aggregation of cohesive Ag atoms. In situ conductivity measurements reveal a granular-metal state of Ag₇C₆₀ crystallites dispersed in an insulating C₆₀ phase (see image). Ag-doped C₆₀ will serve as a new platform for hydrogen-storage materials and novel superconductors.

The new concept of quasi-intercalation and the method of facile amorphization are demonstrated for layered orthorhombic ZnSb, orthorhombic-black P and rhombohedral-grey As. These anode materials showed excellent electrochemical properties. Application of this concept and method in layered materials will be a breakthrough for realization and mass production of next generation lithium ion batteries.

A broad and fast wavelength tuning of the photonic bandgap of a hybrid photonic band structure (PBS) formed from an achiral nematic liquid crystal and a polymer template. Remarkably, red-green-blue reflection from a single device and a single achiral nematic liquid crystal mixture is reported without any additional optical components such as a color filter.

A magnetically recyclable protein separation system has been designed and fabricated by combining ferrimagnetic magnetite cores and NiO nanoparticles decorated onto the mesoporous silica shell with a high surface area (see figure). The exposed NiO nanoparticles provide for the selective adsorption of the His-tagged protein from the mixed-protein solution, as well as cell lysate, and the magnetic core allows the particles to be separated from the solution by applying an external magnetic field.

A photocleavable, poly(ethylene-glycol)-based hydrogel is presented in which predictable, user-defined gradients in the network's structure can be fabricated in real time under cytocompatible conditions. This platform provides new opportunities to investigate how material structure influences cell function. Here, cell morphology is directed spatially by degradation-induced gradients in the local polymer density (see figure, scale bars: 50 μm).

An optical microscope-focused laser beam technique was employed to effectively microstructure uniform patterns on graphene oxide nanosheets in a fast and controlled manner.

A polyanionic electrolyte is used as gate insulator in top-gate p-channel polymer thin-film transistors. The high capacitance of the polyelectrolyte film allows the transistors and integrated circuits to operate below 1.5 V. Seven-stage ring oscillators that operate at supply voltages down to 0.9 V and exhibit signal propagation delays as low as 300 µs per stage are reported.

Organization of phosphorescent domains in seld-assembled block copolymers is demonstrated to yield dual emission for white electroluminescence. Our block- copolymer approach minimizes energy transfer between two colored species by site isolation through morphology control, allowing higher loading concentration of red emitters with improved device performance.

The rational structure optimization of a polythiophene containing benzo[2,1-b;3,4-b′]dithiophene on the molecular level leads to a polymer that is easily synthesized and processed. Fabricated on a flexible substrate, the polymer shows excellent device characteristics, good reproducibility, and charge-carrier mobilities up to 0.5 cm² V⁻¹ s⁻¹ without annealing.

Nitrogen-doped carbons are prepared by thermolysis of two organic, nitrogen-rich ionic liquids (see figure). The nitrogen content can be adjusted by the thermolysis temperature. As the precursors are liquids at room temperature they represent ideal precursors for the direct synthesis of carbon nanostructures and coatings with flexible geometry controlled by the processing of liquids.

Interface dynamic behavior between individual carbon nanotubes (CNTs) and tungsten (W) electrodes is observed directly at a nearly atomic resolution. The W tip-end absorbs the source CNT atoms, which then penetrate deep into its body, form a carbide, and finally precipitate as freshly formed graphitic tubular shells encapsulating the electrode. CNT wall-thickness shaping via stepwise absorption of the nanotube core shells into a W electrode is demonstrated for the first time. This work provides novel one-dimensional CNT–carbide–metal hetero-junctions, as well as new and detailed understanding of the CNT catalytic growth.

Low-dielectric-constant periodic mesoporous organosilica thin films are fabricated by vacuum-assisted aerosol deposition, a vapor-phase delivery technique favored by the semiconductor industry. The mesostructured films possess a combination of dielectric and mechanical properties that make them an ideal candidate for insulating materials on semiconductor chips (see image).

A single-layer graphene–CdS quantum dot nanocomposite is synthesized by a one-step reaction from graphene oxide, and thus avoids the low-yield production and the aggregation of single-layer graphene sheets. This new graphene-based material shows promising optoelectronic properties. Picosecond ultrafast electron transfer from the CdS quantum dots to the graphene sheets has been observed by time-resolved fluorescence spectroscopy.

Photonic crystal scales with a diamond-based lattice from the weevilLamprocyphus augustus are transformed into a high-dielectric titania replica by a biotemplating double-imprint route. Multidirectional optical reflectance spectroscopy of the replicated structure gives an angle-independent reflection band in the visible spectrum, in agreement with photonic band structure calculations, which reveal the formation of a complete photonic bandgap at visible frequencies.

The fabrication of single virus arrays is demonstrated using direct printing of unmodified anti-M13 bacteriophage antibodies onto silicon with nanometer resolution (see image), widely variable feature pitch, and flow alignment of the viruses. Organization of virus-based systems into functional, addressable arrays has many technological applications including microarray technology and bottom-up nanoassemblies.

Patterning of the secondary structure of silk films is achieved on the micrometer scale using a soft lithographic technique, as illustrated in the figure. The alternating areas of silk I and silk II structure have different mechanical, surface, and solubility properties but nominally the same chemical composition. This technique will enable the development of other tailored protein materials with selectively transformed localized secondary structure.

Synthetic protocells, artificial constructs that mimic the basic features of natural cells, such as a supported lipid bilayer and transmembrane proteins, are useful tools to develop new applications in bionanotechnology. Simple energy-converting protocells that incorporate membrane ion channels can convert transmembrane ion gradients into electricity by membrane-protein regulated ion transport. This work provides details on the critical parameters and electrogenic mechanism for droplet protocells and the factors that may be optimized to improve the electrogenic performance.