Advanced Materials

On p. 209, Wojciech Pisula, Klaus Müllen, and co-workers report on directionally oriented, high-performance polymer field-effect transistors for plastic electronics. The cover shows the applied alignment from solution, resulting in pronounced macroscopic ordering of the copolymer chains and finally in excellent transistor behavior, which is promising for applications in, for example, flexible displays.

The mechanical properties and degradation rate of elastomers can be tailored with nanoporosity. The elastomers described in this study by Guillermo Ameer and co-workers (p. 188) are based on citric acid and are biocompatible. The nanopores also facilitate the entrapment and slow release of macromolecular therapeutics. The inside cover depicts the nano- and microarchitecture of the elastomer prior to pore collapse.

The surface sensitivity of X-ray magnetic circular dichroism in extreme conditions has been exploited to investigate the first layers of bulk single-molecule magnets (SMMs), as reported by Roberta Sessoli and co-workers on p. 167. Striking differences have emerged between two classes of SMM having different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices.

Recent advances in bioapplications of carbon nanotubes are reported, including the chemical modification of carbon nanotubes targeting specifically their covalent and noncovalent conjugations with a variety of biological and bioactive species, and the significant recent development and progress in the use of carbon nanotubes for biosensors, drug and other delivery systems, bioimaging, etc. and in the understanding of in vivo biodistribution and toxicity of carbon nanotubes.

Reviewing the vapor–liquid–solid (VLS) mechanism suggests that the term preferential interface nucleation replace VLS-like names. There are many processes and details important to nanowire growth, but preferential nucleation at one interface while nucleation on others is suppressed is the general mechanism that describes why nanowires grow faster in one direction than in others. This mechanism also applies to other systems.

The surface sensitivity of X-ray Magnetic Circular Dichroism in extreme conditions is exploited to investigate the first layers of bulk single-molecule magnets (SMM). Striking differences emerge between two classes of SMM with different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices

A versatile platform for photodynamic therapy (PDT), mesoporous silica nanoparticles functionalized with protoporphyrin IX (PpIX-MSNs), has been developed. In vitro studies on HeLa cells show high uptake efficiency. Phototoxicity results give both irradiation time- and dosage-dependent cell death events. Because of the ease of incorporating other biomedical functional groups, we believe MSNs would be an ideal platform for biomedical applications.

Tunable memory characteristics are investigated according to the metal-nanoparticle species being used in memory devices. The memory devices are fabricated using diblock copolymer micelles as templates to synthesize nanoparticles of cobalt, gold, and a binary mixture thereof. Programmable memory characteristics show different charging/discharging behaviors according to the storage element configurations as confirmed by nanoscale device characterization.

Spherical Janus particles consisting of γ-Fe₂O₃ and SiO₂ bicompartments are effectively prepared through a flame synthetic route. The excellent colloidal stability of these particles offers versatile choices for further manipulating them to form different types of assembled structures. As an example, the synthesis of hollow capsules with a magnetic core and a soft Au/PVP-film shell is demosntrated.

A nanoporous biodegradable elastomer based on citric acid is described. Nanopores are used to control the mechanical and degradation properties of the elastomer. Furthermore, macromolecular drugs can be entrapped under mild conditions via pore collapse, which also delays the release of the drug. The nanoporous elastomer is biocompatible and a promising platform technology for engineering soft tissues.

Epitaxial metal nitride films are prepared using a general chemical solution approach. A polymer-assisted deposition to prepare epitaxial cubic TiN, metastable AlN, and ternary nitride Ti_1−xAl_xN films is demonstrated. The structural, optical and electrical properties of the films are investigated, and may be of interest for many technological applications.

The orientational transition of liquid crystals (LCs) is used as a label-free detection mechanism for immunoassays developed in microfluidic systems. LCs only show bright optical textures (visible to the naked eye) in the line-line intersections in which label-free antibodies bind to their surface-immobilized antigens, suggesting the feasibility of using LCs to detect specific antigen-antibody binding events in a high-throughput and multiplexed manner.

Domain orientation in polymer electrolyte membranes is tuned by controlling its sulfonation level and the moisture content of the air. At low sulfonation levels, highly ordered hydrophobic cylinders oriented perpendicular to the film surface are obtained, when the film is in humid air. Increasing the sulfonation level results in a transition from perpendicular to parallel orientation.

The influence of molecular packing on the performance of polymer organic field-effect transistors is illustrated in this work. Both close π-stacking distance and long-range order are important for achieving high mobilities. By aligning the polymers from solution, long-range order is induced, yielding hole mobilities of up to µ_sat = 1.4 cm² V⁻¹ s⁻¹ and current on/off ratios I_on/I_off of 10⁵.

The facile synthesis of a new five-ring-fused pentacene analog with four symmetrically fused thiophene ring units (Dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene, C_n-DTBDT) is presented. After aligning this material from solution, thin films for organic field-effect transistors were obtained, resulting in excellent hole mobilities of up to 1.7 cm²V⁻¹s⁻¹, and on/off ratio of 10⁷.

Novel dielectric nanocomposites composed of ferroelectric polymers and surface-functionalized TiO₂ nanoparticles with comparable dielectric permittivities and homogeneous nanoparticle dispersions are prepared and characterized. Enhancements in electric displacement and energy density at high electric fields are demonstrated.

A novel method for shaping and positioning ZnO nanoarchitectures using conventional lithography and catalyst-free metal organic vapor-phase epitaxy is demonstrated. Nanowalls and nanotubes of desired shapes and arrangements can be grown heteroepitaxially on Si substrates, and their electron-emission characteristics were optimized by changing their diameter and spacing. This method can be readily expanded to create many artificial 1D and 2D structures, as required for various device applications.

Nitride nanofibers have been synthesized based on a simple electrospinning technique for the first time. No catalysts or templates are needed in this new synthetic method. Highly oriented GaN nanofiber arrays, as well as a high-performance UV photodetector based on single GaN nanofiber assembled FET devices, can be facilely fabricated using this technique. Precise doping of other elements into the GaN nanofibers is easy by this solution-based synthetic method.

CdSeS/CdS/ZnS quantum dot thin films subjected to ZnO atomic layer deposition at 100°C shows photoluminescence (PL) modulation. The PL is quenched during each exposure to diethyl zinc. However, the PL is restored upon subsequent exposure to water.

A new family of oxypnictide superconductors, LaFeAsO_0.89F_0.11, brings new impetus to the field of high-temperature superconductivity. In this work, we show that the upper critical field values H_c2 (48 K) = 13 T and H_c2(0) can exceed 80–230 T in a high-pressure-fabricated NdO_0.82F_0.18FeAs bulk sample with T_c of 51 K. We also demonstrate the superior performance of supercurrent density in fields for this new superconductor.

Multifunctional responsive gel membranes present a new and promising platform for the development of “smart” devices for bioseparation, biosensors, and “smart” drug release. These membranes combine the functions of stimuli-responsive control and regulation of the mass transport with a range of properties, such as storage, catalysis of chemical reactions, antimicrobial activity, and optical signal transduction.