Antireflection (AR) coatings are indispensable requirements for many optical applications such as flat-panel displays, solar cells, lasers, and other optoelectronic devices. [1±4] Two approaches are available as model methods for achieving low surface reflectivity: 1) Fabrication of nanoporous layers using a particle coating, [5] phase separation of a binary polymer blend, [6] and polyelectrolyte multilayer coating. [7] These thin dielectric films with a low refractive index can improve light transmission via the destructive interference of the reflected light at the air±film and the film±substrate interfaces; 2) Fabrication of surface relief structures using holographic lithography, reactive-ion etching, [8] and plate embossing.[9] The array of conical protuberances having sinusoidal profiles cause variations in the refractive index between the air and substrate to be gradual, dramatically reducing the reflection losses at the surface. The former has considerable advantages in cost efficiency, a factor that is basically attributable to the simpler fabrication process involved. However, a lack of controllable factors relative to surface morphology, for example, domain size and air content, is a major drawback of this approach. In designing AR surfaces, it is important to have the surface structures under control, so as to tune the desired wavelength for peak performance.The latter approach, involving surface relief gratings, has many tunable factors, such as the grating spacing, depth, and cross-sectional geometry, in contrast to the former approach. In addition, it is well-known that such relief structures having a periodic sub-wavelength protuberance can behave as an ideal antireflection coating with nearly zero reflectance over a large range of wavelengths and fields of view.[10] These structures are commonly referred to as ªmotheyeº structures, because they have the same geometry as the corneal lenses of night-flying moths. In this communication, we report on attempts to design motheye-like colloidal patterns on a surface in an unprecedented way. Our approach is based on the layer-by-layer (LbL) self-assembly method [11] and consists of alternating layers of charged polymer colloids and polyelectrolytes (PE). Numerous approaches have been reported regarding the array of colloids over charged templates by the LbL approach.[12±16] Recently, colloidal coating as an AR surface has also been demonstrated to be a convenient and economical process.[5] Herein, we demonstrate that the AR efficiency of the colloidal layer can be improved by a novel colloid-on-colloid stamping method, which changes the common colloidal layer into a motheye-like structure with a graded index. A schematic representation of the fabrication process is illustrated in Figure 1. The process starts with a glass substrate on which a PE multilayer is grown by means of the LbL technique. The construction of this multilayer only requires alternate immersion of the substrate into aqueous solutions of the polycation, poly(allylamine hydrochloride)...

Utilizing the unparalleled theoretical capacity of sulfur reaching 1675 mAh/g, lithium-sulfur (Li-S) batteries have been counted as promising enablers of future lithium ion battery (LIB) applications requiring high energy densities. Nevertheless, most sulfur electrodes suffer from insufficient cycle lives originating from dissolution of lithium polysulfides. As a fundamental solution to this chronic shortcoming, herein, we introduce a hierarchical porous carbon structure in which meso- and macropores are surrounded by outer micropores. Sulfur was infiltrated mainly into the inner meso- and macropores, while the outer micropores remained empty, thus serving as a "barricade" against outward dissolution of long-chain lithium polysulfides. On the basis of this systematic design, the sulfur electrode delivered 1412 mAh/g sulfur with excellent capacity retention of 77% after 500 cycles. Also, a control study suggests that even when sulfur is loaded into the outer micropores, the robust cycling performance is preserved by engaging small sulfur crystal structures (S2-4). Furthermore, the hierarchical porous carbon was produced in ultrahigh speed by scalable spray pyrolysis. Each porous carbon particle was synthesized through 5 s of carrier gas flow in a reaction tube.

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Porous capsules composed of hematite, silica, and hematite–silica composites are prepared by a templated synthesis method. Polyelectrolyte multilayer‐coated particles (PEMPs) are used to synthesize goethite nanocrystals and the resulting goethite‐nanocrystal‐embedded PEMPs (PEMP–goethite) are then used as templates to form porous capsules. The surface morphology and surface area of the porous capsules can be controlled by the size of the PEMP–goethite template, which is determined by the extent of growth of the goethite nanocrystals. By controlling the surface morphology and area, it is also possible to tune the sensitivity of the hematite capsules for use as gas‐sensing materials. This surfactant‐free approach is also used to synthesize silica and silica‐based composite capsules with a controllable porous shell thickness. This straightforward approach can also be extended to the synthesis of other porous capsules or particles with a controllable surface morphology.

A one-step, template-free synthetic method for preparing polymeric microcapsules with iron oxide (γ-Fe 2 O 3 ) magnetic nanoparticles (MPs) embedded in the polymer shell is reported. Using a simple emulsification of the multiphase mixture containing liquid prepolymer and MPs in chloroform solution, double emulsions comprising a chloroform core and MPs/polymer shell were spontaneously formed. After exposure to UV light, these double emulsions converted to microcapsules with a polymerized composite shell. The evolution from the double emulsions to the microcapsules was examined by confocal laser scanning microscopy. One unusual feature of these microcapsules is the ability to change shape reversibly by osmotic swelling of the water core upon repetitive drying and hydration. The microcapsules had an intrinsic superparamagnetic response due to the presence of the magnetic nanoparticles and could be moved and collected by external magnetic fields.

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