Advanced Materials

Reaction-diffusion processes initiated from the surfaces of small gel or polymer particles can fabricate complex three-dimensional structures inside these particles. Bartosz Grzybowski and co-workers show on page 1911 that the core/shell particles thus prepared can be further modified “remotely” by electrochemical exchange reactions. The image shows four cubical particles, each having a spherical core fabricated by reaction-diffusion and comprising copper nanoparticles.

Photoelectron spectromicroscopy studies revealed the morphology changes and the abundance of various oxygenated functional groups on individual multiwalled carbon nanotubes exposed to oxidizing environments. Alexei Barinov and co-workers show on page 1916 that carbonyl type bonding configurations prevail when fragmentation and extinction of the nanotubes occur.

Colloidal assemblies can be fabricated in a variety of structures, shapes and forms through a variety of physical processes that are still under extensive development. We survey the strategies for producing particle structures of different degrees of ordering and dimensionality, and the limitations and challenges in the practical fabrication of such assemblies.

The image shows the developing biocompatible molecules with controllable, accurate, and reproducible molecular motor functions for mobile nanodevices. Seon Jeong Kim and co-workers show on page 1907 that the attachment of fullerene moieties to a single-strand DNA significantly improves the molecular switching and stability of this pH driven enthalpic molecular machine. Hydrophobic interactions between the terminal fullerenes in the folded i-motif conformation increased the machines power stroke and force generated.

Fullerene moieties are attached to single-strand DNA and the pH-induced conformational changes are evaluated in detail. It is found that fullerene attachments significantly enhance the machine performance of the DNA strand by stabilization of internal structure through intramolecular hydrophobic interactions.

Reaction-diffusion (RD) processes initiated from the surfaces of mesoscopic particles can fabricate complex core-and-shell structures. The propagation of a sharp RD front selectively removes metal colloids or nanoparticles from the supporting gel or polymer matrix. Once fabricated, the core structures can be processed “remotely” via galvanic replacement reactions, and the composite particles can be assembled into open-lattice crystals.

The gasification process, which increases the number of broken CC bonds and the abundance of particular oxygenated functional groups, is shown to destroy carbon nanotubes (CNTs). The expansion of the defect density and dimensions leads to nonlinear consumption of the CNTs with increasing O dose. Some nanotubes are consumed faster than others, most probably due to higher defect densities.

By employing a block copolymer to spatially organize silver nanoparticles, laser light can be concentrated via plasmon resonance to locally expose a photoresist. By subsequent development, this plasmonic lithography can provide deep subwavelength scale features.

The amount of force one magnetic nanoparticle (MNPs) can deliver is calculated using Fe₃O₄ MNPs building blocks to modify glass fibers. Our results demonstrate that one weight unit of Fe₃O₄ MNPs can eventually drag ≈10 000 times its own weight on a water surface, a significant finding for the development of new magnetic delivery systems and micromanipulators.

Colloids of a highly flexible porous metal-organic framework (MOF) have been prepared using nontoxic and easily removable solvents. Furthermore, a simple dip-coating method for the preparation of optical-quality thin films of the MOF has been developed. The homogeneous thin film exhibits reversible flexibility, as has been proven by environmental ellipsometry.

Three-dimensional photonic crystals of ellipsoidal colloidal particles are prepared by direct convective self-assembly from suspension with the aid of a magnet. The magnetic field provides the orientational order, which is additionally needed for these colloidal particles with symmetry lower than spherical. The positional order is provided by the convection, just as for spherical colloids.

A thin capping layer of titanium sub-oxide (TiOx) prepared by sol–gel synthesis from titanium alkoxides extends the lifetime of organic FETs. The TiO_x layer functions as an ‘active’ passivation/barrier layer that actually removes oxygen and water vapor from the organic semiconductor. The results demonstrate a significant improvement in the lifetime of organic field-effect transistors when exposed to air.

Monodisperse rare-earth fluoride nanocrystals are synthesized and used as building blocks to fabricate dual-mode luminescent colloidal spheres, which are composed of two distinct units, one offering down-converting luminescence under UV excitation and the other providing up-converting luminescent emission when excited with a 980 nm laser, and have potential applications in multiplexed and highly sensitive bioassays.

Biphasic Janus particles with a precisely tunable internal morphology are fabricated using a novel, versatile, and robust technique. This technique can be used in conjunction with microfluidics to produce monodisperse particles, or can be combined with bulk emulsification techniques to produce large quantities of particles.

Organic thin-film field-effect transistor (OTFT) multibit storage devices are fabricated based on pentacene or copper phthalocyaine (CuPc) with normal polymer modifying layers of polystyrene (PS) or polymethylmethacrylate (PMMA). The devices shows excellent multibit storage properties in a single OTFT using electric and light-assisted programs.

Polymer microspheres with a bone-like mineral coatings are generated via a biomimetic process, and this biodegradable coating is used as a carrier for delivery of biological molecules. Acidic and basic proteins are controllably bound and released from these microspheres, suggesting that this approach can be used for binding and delivery of a broad range of biologically active molecules.

Perfectly aligned high-aspect-ratio TiO₂ nanotubes that are perpendicularly oriented to a substrate are obtained using a two-step anodization process in ethylene glycol containing 0.5 wt% NH₄F and 1 vol% HF, overcoming the bundling issue of TiO₂ NTs commonly observed in conventional approaches. They are then used as a template for the electrodeposition of Pt nanowires.

A multianalyte antibody array that is spotted on a poly(oligo(ethylene glycol) methacrylate) brush 100 nm thick, grown on glass via surface-initiated atom transfer radical polymerization, has femtomolar limit-of-detection (LOD) of cytokines in serum and whole blood, and a dynamic range of six orders of magnitude for a range of protein analytes.

By inserting a crosslinkable hole-transport layer as the buffer layer between the single-phase polymer active layer and the anode of this new type of polymer light-emitting electrochemical cells (PLECs), the interface properties are improved and the PLECs can be operated with enhanced stability.

Unprecedented electro-optic (EO) activity and excellent alignment stability at 85 °C are demonstrated through rational design of a new series of dendronized polyenic chromophores capable of supramolecular self-assembly directed by fine-tuned arene–perfluoroarene interactions. Analysis of the EO properties showed exceptional poling efficiency for these molecular glasses at high chromophore number density.

Applying an electrical field to a dielectric may induce a large entropy and temperature change which is attractive for solid-state cooling. We present the general considerations and review the experimental efforts to achieve large electrocaloric effect (ECE) in dielectrics. We show that by operating above the order-disorder transitions, a large ECE can be achieved in a ferroelectric polymer.