We have developed a self‐assembly method for fabricating well‐ordered two‐dimensional (2D) and three‐dimensional (3D) colloidal crystal films. With a minute amount of a polystyrene colloidal suspension and without any special equipment, the proposed method can be used to rapidly deposit high‐quality colloidal crystal films over a large surface area. By controlling the lift‐up rate of the substrate, we modulate the meniscus thinning rate, which determines whether the colloidal particles are assembled into two or three dimensions. The proposed method can be used to fabricate not only monolayered colloidal crystals with colloidal particles of various sizes, but also multilayered colloidal crystals. In addition, the method enables us to fabricate binary colloidal crystals by consecutively depositing large and small particles.

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by a Teflon spacer, which also served to seal the cell. Inside the cell, a stainless steel piston on a spring within a polyvinyl chloride sleeve provided stack pressure (∼1 kg cm -2 ). The electrodes were formed by cutting lithium foil (Aldrich 99.9 %, thickness 180 Lm) with a 1.6 cm diameter stainless-steel punch, giving an electrode area of 2 cm 2 . A glass-fiber separator (Whatman GF/A type) was used to insulate the two electrodes. The lithium symmetrical cells were assembled in an argon-filled glove-box prior to removal for study. Galvanostatic cycling was performed using a Battery test unit 1470 interfaced to a Solartron 125 56 FRA using Corrware (version 2.7) from Scribner Associates. EIS measurements were obtained from 100-0.1 Hz with an amplitude of 5 mV vs V OC . Cell temperature was maintained at 40 and 80°C using a Heraeus oven calibrated to an accuracy of ± 0.5°C. Colloidal crystals comprised of two-or three-dimensionally ordered arrangements of monodisperse colloidal particles have been studied extensively over the past decade because of their potential applications. Received[1] Recently, colloidal crystals have attracted renewed interest because they provide a simple, fast and cheap approach to creating three-dimensional (3D) photonic crystals.[2]The majority of recently reported colloidal crystals, however, have been fabricated from uniformly sized colloidal particles. These crystals exhibit a limited range of crystal structures-mainly face-centered cubic (fcc), hexagonal closed-packed, or body-centered cubic (bcc) in a confined geometry-which are not ideal structures for investigating condensed-matter physics or for practical applications, especially the creation of 3D photonic crystals with full photonic bandgaps (PBGs). [3,4] Binary colloidal mixtures of large and small colloidal particles also form colloidal crystals. In contrast to the limited crystal structures formed by collections of uniformly sized colloidal particles, binary colloidal crystals show rather a rich array of crystal structures depending on the size ratio and concentrations of large and small particles. This range of structures makes binary systems a very interesting potential avenue for creating 3D photonic crystals with a full PBG. However, binary colloidal crystals are hard to grow and characterize, and thus they have not yet been extensively investigated. Recently, a few methods have been developed for constructing binary colloidal crystals: controlled drying, accelerated evaporation, and stepwise spin-coating. [4][5][6] Here, we present a method that provides a simple, fast, and cheap alternative approach to the fabrication of binary colloidal crystals. The method is referred to as "confined convective assembly", which is good for the rapid fabrication of well-ordered two-dimensional (2D) colloidal crystals with colloidal particles of various sizes over a large area. [7] This method has several advantages over previously reported procedures for fabricating binary colloidal crystals. Firstly, it can rapidly (in COMMUNICATI...

This paper presents a systematic study of the galvanic replacement reaction between 23.5 nm singlecrystal Ag nanospheres and HAuCl 4 in an aqueous medium. We have monitored both morphological and spectral changes as the molar ratio of HAuCl 4 to Ag is increased. The replacement reaction on single-crystal Ag nanospheres results in the formation of a series of hollow and porous nanostructures composed of Au-Ag alloys. By varying the molar ratio of HAuCl 4 to Ag, we are able to control the size and density of the pores. In addition, the localized surface plasmon resonance peaks of these nanostructures can be readily tuned from 408 to 791 nm as the product becomes increasingly more hollow and porous.

Soft materials with layered structure such as membranes, block copolymers and smectics exhibit intriguing morphologies with nontrivial curvatures. Here, we report restructuring the Gaussian and mean curvatures of smectic A films with free surface in the process of sintering, that is, reshaping at elevated temperatures. The pattern of alternating patches of negative, zero and positive mean curvature of the air–smectic interface has a profound effect on the rate of sublimation. As a result of sublimation, condensation and restructuring, initially equilibrium smectic films with negative and zero Gaussian curvature are transformed into structures with pronounced positive Gaussian curvature of layers packing, which are rare in the samples obtained by cooling from the isotropic melt. The observed relationship between the curvatures, bulk elastic behaviour and interfacial geometries in sintering of smectic liquid crystals might pave the way for new approaches to control soft morphologies at micron and submicron scales.

Herein, a facile, one‐step hydrothermal route to synthesize novel all‐carbon‐based composites composed of B‐doped graphene quantum dots anchored on a graphene hydrogel (GH‐BGQD) is demonstrated. The obtained GH‐BGQD material has a unique 3D architecture with high porosity and large specific surface area, exhibiting abundant catalytic active sites of B‐GQDs as well as enhanced electrolyte mass transport and ion diffusion. Therefore, the prepared GH‐BGQD composites exhibit a superior trifunctional electrocatalytic activity toward the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction with excellent long‐term stability and durability comparable to those of commercial Pt/C and Ir/C catalysts. A flexible solid‐state Zn–air battery using a GH‐BGQD air electrode achieves an open‐circuit voltage of 1.40 V, a stable discharge voltage of 1.23 V for 100 h, a specific capacity of 687 mAh g−1, and a peak power density of 112 mW cm−2. Also, a water electrolysis cell using GH‐BGQD electrodes delivers a current density of 10 mA cm−2 at cell voltage of 1.61 V, with remarkable stability during 70 h of operation. Finally, the trifunctional GH‐BGQD catalyst is employed for water electrolysis cell powered by the prepared Zn–air batteries, providing a new strategy for the carbon‐based multifunctional electrocatalysts for electrochemical energy devices.

The design and preparation of hollow nonspherical microparticles are of great significance for their potential applications, but the development of a facile synthetic method using only one production step remains a great challenge. In the current work, a new template-free method based on dispersion polymerization was successfully developed to produce anisotropic hollow polystyrene (PS) microparticles in a single step. In the synthesis, ammonium persulfate (APS) played a critical role in the formation and growth of highly uniform and stable hollow PS microparticles. By varying the concentration of APS and that of the stabilizer used, polyvinylpyrrolidone, we were able to control the average size of the PS particles and their degree of concavity. Based on our results and observations, a plausible mechanism for formation of these unusually shaped PS microparticles was proposed.

The fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene‐co‐vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1685–1693, 2004