Advanced Materials

Microelectrodes implanted in the brain are increasingly being used to treat neurological disorders. However, robust and reliable chronic application of neural electrodes remains a challenge. Mohammed Reza Abidian and co-workers report on p. 3764 the use of conducting polymer nanotubes as highly selective neural interfaces for chronic neural recordings at the microscale. The quality of neuronal spike recordings was significantly improved relative to comparably sized metal electrode sites, primarily through a reduced noise level amidst maintained spike amplitudes.

The inside cover shows a scheme for the preparation of photonic dome patterns, SEM images of a dome pattern, and a single dome decorated with 2D colloid array, as fabricated in work reported on p 3771 by Seung-Man Yang and co-workers. The background is an optical microscopy image of patterned photonic domes, which can be used as a near-field microlens array. The greenish color of the domes corresponds to the photonic bandgap.

The aim of the present comment is to show that when both calorimetric and magnetization measurements are properly executed, there is no significant discrepancy in the entropy values obtained from the two methods, thus validating the use of the Maxwell relations, which is the most commonly used technique in the study of the magnetocaloric effect.

The magnetocaloric effect (MCE) of Ni₄₃Mn₄₆Sn₁₁ in the vicinity of a first-order martensitic phase transition is discussed by using magnetic measurements, heat capacity measurements and differential scanning calorimetry (DSC) measurements. The results confirm that the MCE of Ni₄₃Mn₄₆Sn₁₁ obtained by magnetic measurements (via the Maxwell relation) may be seriously overestimated and Ni-Mn-Sn alloys should be treated carefully.

The recent advancements in the large-scale integration of single crystalline, inorganic nanowire (NW) arrays for electronic and sensor applications are discussed, specifically involving the contact printing of NWs at defined locations. We address the advantages, limitations, and the state-of-the-art of this technology, and present an integration platform for future printable, heterogeneous sensor circuitry based on NW parallel arrays.

An approach to address the precise controllable patterned wettability transition on the superhydrophobic aligned photoconductive nanorod-array surface via a photoelectric cooperative wetting process is described. This work is promising to gear up the application of locally confining liquids at a desired location, such as liquid reprography by patterned-light illumination.

Substrates with arbitrary shapes covered by a linear polyethyleneimine layer can effectively afford complexly nanotextured silica/titania thin films on their surfaces when the substrates are dipped into the source solutions at room temperature. The nanotextured thin films can be turned into superhydrophobic surfaces after they are treated with alkylsilane.

AFM image of 17 nanodevices with a zoom-in cartoon schematically shows an individual crosspoint device consisting of two Pt metal electrodes separated by a TiO₂ bi-layer memristive material. By applying an electric field across the memristive material, oxygen vacancies can drift up and down, leading to four current-transport end-states. The switching between these end-states results in a family of nanodevices.

The charge-induced optical absorptions of two-dimensional polarons in semicrystalline, high-mobility conjugated polymers are investigated as a function of distance from an interface with polymer gate dielectrics of different dielectric constants. For high-k dielectrics, polarons in the accumulation layer at the interface are found to be more localized than those in the bulk.

Microelectrodes implanted in the brain are increasingly being used to treat neurological disorders. However, robust and reliable chronic application of neural electrodes remains a challenge. Here, we report, the use of conducting polymer nanotubes as highly selective neural interfaces for chronic neural recordings. Poly(3,4-ethylenedioxythiophene) nanotubes were formed on the chronic neural microelectrode. The quality of neuronal spike recordings was significantly improved relative to metal electrode sites.

Hierarchical dome patterns are prepared via a novel single-step patterning process. Photonic domes with isotropic reflection colors are patterned on a prepatterned glass substrate with a hydrophobic moiety using photocurable emulsion droplets of all-equal size, which contain concentrated silica particles. Furthermore, embossed domes are patterned with PS particle-stabilized photocurable emulsion droplets, which can act as a near-field microlens array.

A new ambipolar material bis(carbazolyl)benzodifuran (CZBDF) shows well-balanced and high carrier mobilities for both holes and electrons (>10⁻³ cm² V⁻¹ s⁻¹). This new material allows us to fabricate efficient p-i-n homojunction OLEDs that emit light across the full visible color range and perform at a level similar to state-of-the-art heterojunction devices.

Gd₅Si₂Ge₂ belongs to the class of materials known as metamagnets that show promise for application in room-temperature magnetic refrigeration using a phenomenon known as the magnetocaloric effect. Here we image the metamagnetic transition using a local scanning Hall probe and reveal how the microstructure controls the critical properties.

A new adamantane bent-core liquid crystal exhibiting a metastable ferroelectric phase with large polarization is synthesized and characterized. The material shows reversible switching between a birefringent (opaque) and an optically isotropic (clear) state. In the clear state, the observed piezoelectric constant is comparable to those of commercial solid-state piezotransducers.

Hollow ring arrays with an outer and inner diameter of 33 and 11 nm, respectively, are formed from a thin film of poly-(styrene-b-ferrocenylethylmethylsilane-b-2-vinyl pyridine) (PS-b-PFS-b-P2VP) triblock terpolymer with a core/shell cylindrical morphology. The PS minority block forms a core surrounded by a PFS shell in a P2VP matrix; the core/shell structure is oriented perpendicularly to the film surface. The PS core and P2VP matrix blocks are partly removed using oxygen reactive ion etching, leaving ring patterns made from oxidized PFS.

Vertical interface effect on the physical properties of epitaxial metal-oxide films is demonstrated. Self-assembled (BiFeO₃)_0.5:(Sm₂O₃)_0.5 nanocomposite films are fabricated with three-dimensional heteroepitaxy having an ordered nano-columnar structure on a large scale. The vertical interface effect on lattice parameters, dielectric properties, and leakage currents is investigated.

Basic principles of capillary-induced adhesion and roughness-enhanced hydrophobicity are utilized to design three superhydrophobic porous-nanostructure models whose adhesion forces ranged from strong to weak. The design idea is well-supported by experimental results, which indicated that adhesive forces may be tailored by modifying structural morphologies to manipulate solid–liquid contact behavior and air-pocket composition in open or sealed systems.

Silica “nanorattles” are fabricated by means of selective etching of ingeniously designed organic–inorganic hybrid silica spheres with a three-layer “sandwich” structure. The size (95–645 nm), shell thickness, and core diameter of the monodisperse nanorattles can be precisely controlled, even in gram-scale production. This method is also shown to be promising for development as a general method for synthesis of rattle-type functional nanomaterials.

The chalcopyrite-like structure of Cu₂MSnQ₄ is an ordered tetrahedral array of flattened CuQ₄ and undistorted MQ₄ and SnQ₄, with a low lattice thermal conductivity. The [Cu₂Q₄] tetrahedral layers are electrically conducting, and the [SnMQ₄] layers are electrically insulating.