Advanced Materials

Joel Miller, Peter Stephens, and co-workers report on p. 2514 on Mn^II(TCNE)_3/2I_3/2(TCNE = tetracyanoethylene), which is a ferrimagnet at a surprisingly high temperature of 0 °C under pressure. It has a 3D network structure with each Mn ion coordinated to six TCNE radicals, leading to strong spin coupling and ferrimagnetic behavior. This composition/structure is the Rosetta stone for understanding several organic-based magnets by providing insight into the design/control of the magnetic interactions needed to develop enhanced materials combining magnetism with other technologically important properties.

Quasi-amorphous thin films of BaTiO₃, SrTiO₃, and BaZrO₃ are the only known examples of inorganic, non-crystalline, polar materials. Their polarity is the result of the orientational ordering of local bonding units but without any detectable spatial periodicity. The present report provides an overview of the essential features of these materials including preparation, structure, and chemical composition.

Progress in modeling the electronic properties of π-conjugated self-assembled monolayers (SAMs) on metals is reported. Particularly emphasized is the impact of the chemical composition of the SAM-forming molecules on key interfacial quantities such as the SAM-induced work-function modification and the energy-level alignment at metal/SAM and metal/SAM/organic-semiconductor junctions.

Mn^II(TCNE)_3/2(I₃)_1/2 and Mn^II(TCNE)[C₄(CN)₈]_1/2 [tetracyanoethylene (TCNE)] are organic-based magnets with 3D and 2D extended network structures with vastly different magnetic behavior. They have similar ferrimagnetic coupled layers of Mn^II(TCNE)^•− with different interlayer couplings, which lead, respectively, to net ferrimagnetic (T_c = 171 K) and antiferromagnetic (T_c = 68 K) order.

The effect quantum dots have on primary rat macrophages is investigated, and the findings are compared to in vivo data. In vitro uptake kinetics and degradation both reflect in vivo findings; therefore, primary macrophages are shown to be an appropriate system with which to investigate cellular responses to quantum dots and other nanoparticles in order to guide in vivo studies.

A mixed self-assembled monolayer containing aliphatic and electron-accepting (C₆₀) components is employed as an ultrathin molecular gate dielectric to facilitate reversible, nonvolatile electronic memory functionality in organic transistors at low supply voltages. By adjusting the stoichiometry of the monolayer components, the transistor and memory characteristics can be tuned.

Field-effect transistors built using the high superconducting transition temperature (high-T_c) superconductor YBa₂Cu₃O_7–x as the active conductor and electrolyte as the gate dielectric (see figure) show substantial and relatively robust modulation of conductivity with large increases in T_c of up to 38 K.

A nanogenerator based on a single piezoelectric fine wire producing an alternating current (AC) is successfully used for the harvesting of biomechanical energy under in vivo conditions. We demonstrate the implanting and working of such a nanogenerator in a live rat where it harvests energy generated by its breathing or heart beating. This study shows the potential of applying these nanogenerators for driving in vivo nanodevices.

A biocompatible method for general construction of 3D structures by aggregation of micrometric polymeric subunits is presented. Shape-controlled microgels are forced to self-assemble, in a structure similar to a brick wall, in different shapes by limiting their movement onto a surface. Scaffolds with high spatial resolution in the aggregation and composed by the addition of multiple layers are produced.

Ultrasensitive DNA detection using enhanced two-photon excited fluorescence: DNA detection systems formed on a highly regular gold nanopattern over a large area show enhanced sensitivity from high to ultralow concentrations (∼10−11 M, see figure) target molecules. The observed two-photon excited fluorescence on the gold patterned surface is enhanced over two orders of magnitude compared with the molecules on the glass surface.

High-quality single-crystalline centimeter-long V₂O₅ nanowires are produced using an environmental friendly hydrothermal approach without dangerous reagents or harmful solvents and surfactants. The field-emission, electrochemical, and electrical transport, and photoconductive properties are thoroughly investigated and suggest a high potential of utilizing these novel nanowires in field emitters, lithium ion batteries, interconnects, and optoelectronic devices.

The fabrication of photoresponsive supramolecular amphiphiles is demonstrated. The supramolecular amphiphile can self-assemble in water to form uniform nanofibers. Interestingly, the nanofiber can readily transform into vesicles in response to UV irradiation.

Reversibly crosslinked micellar nanoparticles that are capable of releasing encapsulated DNA in response to a reduction microenvironment and physiological ionic strength are synthesized for gene delivery. The dual-sensitive nanoparticles exhibit significantly enhanced complex and colloidal stability, yield more sustained DNA unpacking in cytosols, and mediate enhanced and more prolonged transgene expression for at least 10 days.

Transformation optics provides a new design methodology allowing unprecedented manipulation of light propagation. Traditionally, optical elements only involve stretching or compressing the optical space in one direction whereas the remaining dimensions are unaltered. However, space can be modified in all dimensions simultaneously so that the additional degrees of freedom provided by transformation optics can be used to imprint different elements into a single optical device.

High-dielectric-constant insulators, organic monolayers, and electrolytes have been successfully used to generate organic field-effect transistors operating at low voltages. Here, we report on a device gated with pure water. By replacing the gate dielectric by a simple water droplet, we produce a transistor that entirely operates in the field-effect mode of operation at voltages lower than 1 V. This result creates opportunities for sensor applications using water-gated devices as transducing medium.

Highly efficient plasmonic photocatalysts of AgCl:Ag hybrid nanoparticles are successfully synthesized via a one-pot synthetic approach involving a precipitation reaction followed by polyol reduction. The as-synthesized nanoparticles exhibit high catalytic performance under visible light and sunlight for decomposing organics, such as methylene blue.

A PM-β-CD/polyaniline polypseudorotaxane and its conjugate with multiwalled carbon nanotube were synthesized successfully and showed not only the satisfactory water solubilities but also the highly efficient stabilization to the radical cation form, i.e., the conductive doped form, of polyaniline.

A novel polar oxide of ZnSnO₃ with LiNbO₃-type structure has been investigated using first-principles density functional theory. The calculated pressure dependence of the phase stability in the ternary Zn²⁺Sn⁴⁺O²⁻ system confirms the experimental results and detailed mechanism of the pressure-induced phase transition (see Fig.). High spontaneous polarization of 56.9 °C cm⁻² is calculated by the Berry-phase approach, and it is attributed to the large displacement of Zn²⁺ and its strong ionicity. Further improvement of the spontaneous polarization is suggested by enhancing the covalency of Sn⁴⁺ sites.

High-density arrays of highly ordered ferritin nanocages are fabricated through the guided assembly of thiol-modified ferritin on prepatterned gold nanodots, which are prepared by block copolymer micelle lithography. One and only one ferritin nanocage is anchored to each gold nanodot, as confirmed by scanning electron and scanning force microscopy.