Advanced Materials

An array of passive Au antennae (whose magnified image is shown in the background) fabricated on an all-protein-based silk substrate were conformally transferred and adhered to the surface of an egg by F. G. Omenetto and co-workers. The process allows for intimate contact of micro- and nanostructures that can probe their surrounding environment, and accordingly provides the opportunity for in-situ monitoring of food quality. This type of device is composed entirely of edible and biodegradable components, making it well suited for interfaces with biological matter. For more details, see page 1067.

Gecko-inspired reversible adhesive materials with unprecedented force capacities are described by D. Irschick, A. Crosby, and co-workers on page 1078. A simple scaling parameter, which describes both natural and synthetic reversible adhesive systems, leads to the development of unpatterned synthetic adhesive materials. Adhesive force capacities as high as 2950 N are achieved, not with fibrillar features, but through an integrated design with inextensible, draping fabrics, inspired by the skin-tendon morphologies found in the tokay gecko. The image presents an arm of a tokay gecko in front of a draping fabric.

on page 1084

Design of nanometer to micrometer thin films by spraying solutions of polyelectrolyte is a recent emerging concept in the field of surface coating. Herein the origin of this new process, the fundamental issues, and the resulting potential applications relative to spray assisted deposition from the current literature are reviewed.

Atomic layer deposition (ALD) is a thin film technology that in the past two decades rapidly developed from a niche technology to an established method. It has proven to be a key technology for the surface modification and the fabrication of complex nanostructured materials for energy and environmental applications. Figure reproduced with permission from [5].

On page 1034 W.-T. Pong, I. Manners, W.-Y. Wong, and co-workers report the simple and rapid fabrication of patterned L10-FePt alloy nanoparticles from a solution-processable bimetallic polyferroplatinyne polymer precursor. This approach holds great promise for fabricating L10-FePt-type bit-patterned media using high-throughput nanoimprint lithography, followed by controlled pyrolysis of the nanopatterned polymer. Each dot in the asgenerated FePt-containing nanodot array is magnetic, which can serve as a good platform for future ultrahigh-density perpen-dicular magnetic data recording systems.

A polyferroplatinyne polymer can be patterned on the surface of Si wafer in ordered nanoline or nanodot shapes with PDMS molds through nanoimprint lithography (NIL), and subsequent thermal treatment gives rise to the nanopatterned arrays of L1₀-FePt nanoparticles with the same periodicities. The method offers excellent potential to be utilized in the simple and rapid fabrication of bit patterned media for magnetic data recording.

A novel approach for the rational synthesis of low-defect density, patterned graphene from the bottom up, called barrier-guided chemical vapor deposition, is introduced. A patterned barrier layer impedes the growth of graphene in selected areas of the copper substrate, guiding the growth of graphene into desired micro- and nano- structures with control over placement, orientation, and spatial and lateral extent.

A series of multishelled ZnO hollow microspheres with controlled shell number and inter-shell spacing have been successfully prepared by a simple carbonaceous microsphere templating method, whose large surface area and complex multishelled hollow structure enable them load sufficient dyes and multi-reflect the light for enhancing light harvesting and realize a high conversion efficiency of up to 5.6% when used in dye-sensitized solar cells.

Toward a Smart Optical Biosensor Based on Nanoporous Anodic Alumina (NAA): By modifying the pore geometry in nanoporous anodic alumina we are able to change the effective medium at will and tune the photoluminescence of NAA. The oscillations in the PL spectrum are converted into exclusive barcodes, which are useful for developing optical biomedical sensors in the UV-Visible region.

A facile one step method for periodic nanostructuring of organic solar cells is presented. The nanostructured metal–organic interface delivers combined enhanced light trapping and improved charge extraction leading to up to a 10% increase in power conversion efficiency of already optimized planar devices.

A novel polymer, poly(2-(N -carbazolyl)ethyl methacrylate) end-capped with fullerene (PCzMA-C₆₀), has been synthesized via living anionic polymerization. Electrically programmable flash memory devices were easily fabricated with this polymer by using solution coating and metal deposition. This polymer was found in these devices to exhibit bipolar and unipolar switching behaviors with a high ON/OFF current ratio, a long retention time, high reliability, and low power consumption. The excellent properties and easy processability of this polymer open up the possibility of the mass production of high performance nonvolatile memory devices at low cost.

An array of passive metamaterial antennas fabricated on all protein-based silk substrates were conformally transferred and adhered to the surface of an apple. This process allows the opportunity for intimate contact of micro- and nanostructures that can probe, and accordingly monitor changes in, their surrounding environment. This provides in situ monitoring of food quality. It is to be noted that this type of sensor consists of all edible and biodegradable components, holding utility and potential relevance for healthcare and food/consumer products and markets.

A new manufacturing strategy for buckling of aligned carbon nanotubes is developed, which does not involve prestretching the substrate but relies on the interface interaction between the nanotubes and the substrate. More specifically, upon stretching the substrate the nanotubes slide on the substrate, but upon releasing the nanotubes buckle. Following this manufacturing strategy, stretchable conductors based on aligned carbon nanotubes are demonstrated.

Hand-sized gecko-inspired adhesives with reversible force capacities as high as 2950 N (29.5 N cm^-2) are designed without the use of fibrillar features through a simple scaling theory. The scaling theory describes both natural and synthetic gecko-inspired adhesives, over 14 orders of magnitude in adhesive force capacity, from nanoscopic to macroscopic length scales.

Highly photoactive, graphene-wrapped anatase TiO₂ nanoparticles are synthesized through one-step hydrothermal reduction of graphene oxide (GO) and TiO₂ crystallization from GO-wrapped amorphous TiO₂ NPs. Graphene-TiO₂ nanoparticles exhibit a red-shift of the band-edge and a significant reduction of the bandgap (2.80 eV). Graphene-TiO₂ nanoparticles possess excellent photocatalytic properties under visible light for the degradation of methylene blue.

A novel method to fabricate graphene paper with folded structured graphene sheets is described. When used as an electrode for LIBs and supercapacitors, the as-prepared graphene paper can show much higher performances compared to conventional graphene paper fabricated by a flow-directed assembly method. The unique graphene paper obtained here is promising to act as a new kind of flexible electrode for wearable or rolling-up devices.

Patchy particles are fabricated using a method of embedding-into and extracting-from thick, biocompatible, gel-like HA/PLL films. Control over the patchiness is achieved by adjusting the stiffness of films, which affects embedding and masking of particles. The stiffness is adjusted by the concentration of gold nanoparticles adsorbed onto the surface of the films.

The fabrication of fully three-dimensional photonic crystals with a bandgap at optical wavelengths is demonstrated by way of direct femtosecond laser writing of an organic-inorganic hybrid material with metal-binding moieties, and selective silver coating using electroless plating. The crystals have 600-nm intralayer periodicity and sub-100 nm features, and they exhibit well-defined diffraction patterns.

Nonvolatile ferroelectric random-access memory uses ferroelectric thin films to save a polar state written by an electric field that is retained when the field is removed. After switching, the high energy of the domain walls separating regions of unlike polarization can drive backswiching resulting in a loss of switched domain volume, or in the case of very small domains, complete retention loss.

Uniform urchin-like α-FeOOH hollow spheres assembled from nanoneedles have been synthesized via a facile and green one-pot method. By simply adjusting the amount of glycerol in the reaction system, hierarchical urchin-like α-FeOOH solid spheres or hollow spheres can be obtained. When evaluated for the potential use in water treatment, it is found that the as-obtained uniform urchin-like α-FeOOH hollow spheres exhibit excellent capability for removing both organic dye and heavy metal ions in waste water.

A method for forming organic single-crystal arrays from solution is demonstrated using an organic semiconductor, 3,9-bis(4-ethylphenyl)-peri-xanthenoxanthene (C₂Ph-PXX). Supersaturation of C₂Ph-PXX/tetralin solution is spatially changed by making a large difference in solvent evaporation to generate nuclei at the designated location. The method is simple to implement since it employs only a micropattern and control of the solvent vapor pressure during growth.

The nature and degree of supersaturation (DS) of CdSe monomers plays an essential role in the formation of CdSe magic-sized nuclei (MSN), magic-sized nanoclusters (MSCs), and regular nanocrystals (RNCs) in 1-octadecene (ODE) from reactions with cadmium acetate Cd(OAc)₂ as a Cd source. With low and high myristic acid to Cd(OAc)₂ feed molar ratios such as 1-to-2 and 3-to-1, the resulting Cd precursors are OAc-Cd-MA and MA-Cd-MA, respectively, which play an important role in the formation of the various CdSe NCs.