Frank Marlow;Michael D. McGehee;东元 赵;Bradley F. Chmelka;Galen D. Stucky

Advanced Materials

1999-6-2

Renyuan Zhang;Yuanjin Du;Dan Li;Dengke Shen;Jianping Yang;Zaiping Guo;Hua Kun Liu;Ahmed A. Elzatahry;东元 赵

Advanced Materials

2014-10

东元 赵;Hiroshi Imahori;Christine Schmidt;Peter Skabara;Fiona McKenzie;Sam Kelti

Journal of Materials Chemistry C

2015-1-7

Silicon as an electrode suffers from short cycling life, as well as unsatisfactory rate-capability caused by the large volume expansion (~400%) and the consequent structural degradation during lithiation/delithiation processes. Here, we have engineered unique void-containing mesoporous carbon-encapsulated commercial silicon nanoparticles (NPs) in yolk-shell structures. In this design, the silicon NPs yolk are wrapped into open and accessible mesoporous carbon shells, the void space between yolk and shell provides enough room for Si expansion, meanwhile, the porosity of carbon shell enables fast transport of Li⁺ ions between electrolyte and silicon. Our ex-situ characterization clearly reveals for the first time that a favorable homogeneous and compact solid electrolyte interphase (SEI) film is formed along the mesoporous carbon shells. As a result, such yolk-shell Si@mesoporous-carbon nanoparticles with a large void exhibits long cycling stability (78.6% capacity retention as long as 400 cycles), and superior rate-capability (62.3% capacity retention at a very high current density of 8.4Ag^-1).

Jianping Yang;Yun Xiao Wang;Shu Lei Chou;Renyuan Zhang;Yanfei Xu;Jianwei Fan;Wei xian Zhang;Hua Kun Liu;东元 赵;Shi Xue Dou

Nano Energy

2015-11-1

Mesostructured composite materials, with features ranging from 20 to 500 Å in size, are obtained by the kinetically controlled competitive assembly of organic and inorganic species into nanostructured domains. Short-range order is limited, and long-range order is determined by weak forces such as van der Waals or hydrogen-bonding. Three-dimensional mesoporous materials obtained by removing the organic phase are of particular interest for applications such as catalysis and chemical sensing or separation, for which structural features such as cavity shape, connectivity and ordered bimodal porosity are critical. But atomic-scale structural characterization by the usual diffraction techniques is challenging for these partially ordered materials because of the difficulty in obtaining large (> 10 μm) single crystals, and because large repeat spacings cause diffraction intensities to fall off rapidly with scattering angle so that only limited small-angle data are available. Here we present a general approach for the direct determination of three-dimensional mesoporous structures by electron microscopy. The structure solutions are obtained uniquely without pre-assumed models or parametrization. We report high-resolution details of cage and pore structures of periodically ordered mesoporous materials, which reveal a highly ordered dual micro- and mesoscale pore structure.

Yasuhiro Sakamoto;Mizue Kaneda;Osamu Terasaki;东元 赵;Ji Man Kim;Galen Stucky;Hyun June Shin;Ryong Ryoo

Nature

2000-11-23

Because of its unmatched resource potential, solar energy utilization currently is one of the hottest research areas. Much effort has been devoted to developing advanced materials for converting solar energy into electricity, solar fuels, active chemicals, or heat. Among them, TiO₂ nanomaterials have attracted much attention due to their unique properties such as low cost, nontoxicity, good stability and excellent optical and electrical properties. Great progress has been made, but research opportunities are still present for creating new nanostructured TiO₂ materials. Core-shell structured nanomaterials are of great interest as they provide a platform to integrate multiple components into a functional system, showing improved or new physical and chemical properties, which are unavailable from the isolated components. Consequently, significant effort is underway to design, fabricate and evaluate core-shell structured TiO₂ nanomaterials for solar energy utilization to overcome the remaining challenges, for example, insufficient light absorption and low quantum efficiency. This review strives to provide a comprehensive overview of major advances in the synthesis of core-shell structured TiO₂ nanomaterials for solar energy utilization. This review starts from the general protocols to construct core-shell structured TiO₂ nanomaterials, and then discusses their applications in photocatalysis, water splitting, photocatalytic CO₂ reduction, solar cells and photothermal conversion. Finally, we conclude with an outlook section to offer some insights on the future directions and prospects of core-shell structured TiO₂ nanomaterials and solar energy conversion.

Wei Li;Ahmed Elzatahry;Dhaifallah Aldhayan;东元 赵

Chemical Society Reviews

2018-11-21

Light management is of paramount importance to improve the performance of optoelectronic devices including photodetectors, optical sensors, solar cells, and light-emitting diodes. Photonic crystals are shown as an effective metamaterial for trapping light among their various photon management functions. Herewith, it is demonstrated that spherical photonic crystals, or in other words, photonic beads, possess a stronger light-trapping effect compared to the planar counterpart. The photonic beads are fabricated by colloidal self-assembly under microdroplet confinement employing microfluidic devices. The light–matter interactions are illustrated by the emission intensity and lifetime of the embedded emitters, namely carbon dots and upconversion nanoparticles (UCNPs). The bandgaps of the photonic beads are selected according to the emission and excitation peaks of the light emitters, whereby the emission or excitation peak overlaps the blue edge or red edge of the photonic bands, respectively. Significantly stronger emission and extended luminescence lifetime are observed in photonic beads ensemble in comparison to the planar photonic crystals, demonstrating enhanced light trapping owing to the spherical geometry, which introduces additional microcavity effect. Photonic beads represent a perfect hierarchical light manipulation system. Combining both photonic and microcavity resonator effects, photonic beads potentially find applications in light harvesting, sensing, lighting devices, and light-triggered manipulations.

Nikhil Aravindakshan;Ehsan Eftekhari;Say Hwa Tan;Xiaomin Li;James St John;Nam Trung Nguyen;Huijun Zhao;东元 赵;Qin Li

Advanced Optical Materials

2020-4-1

Dendritic mesoporous silica-carbon nanospheres with a uniform size (∼100 nm), high surface area (646 m² g^-1), large pore volume (1.4 cm³ g^-1) and center-radial oriented open mesopore channels (7.3 nm) have been fabricated by combining an oil-water biphase stratification and an in situ carbonization of surfactant template strategy.

Jianping Yang;Wangyuan Chen;Dengke Shen;Yong Wei;Xianqiang Ran;Wei Teng;Jianwei Fan;Wei Xian Zhang;东元 赵

Journal of Materials Chemistry A

2014-8-7

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m² g⁻¹), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free-standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well-defined pore diameters for highly efficient nanosize-based separation at the macroscale.

Yupu Liu;Dengke Shen;Gang Chen;Ahmed A. Elzatahry;Manas Pal;Hongwei Zhu;Longlong Wu;Jianjian Lin;Daifallah Al-Dahyan;Wei Li;东元 赵

Advanced Materials

2017-9-20

Self-assembled lamellar silica-surfactant mesophase composites have been prepared with crystal-like ordering in the silica frameworks using a variety of cationic surfactant species under hydrothermal conditions. These materials represent the first mesoscopically ordered composites that have been directly synthesized with structure-directing surfactants yielding highly ordered inorganic frameworks. One-dimensional solid-state ²⁹Si NMR spectra, X-ray diffraction patterns, and infrared spectra show the progression of molecular organization in the self-assembled mesophases from structures with initially amorphous silica networks into sheets with very high degrees of molecular order. The silicate sheets appear to be two-dimensional crystals, whose structures and rates of formation depend strongly on the charge density of the cationic surfactant headgroups. Two-dimensional solid-state heteronuclear and homonuclear NMR measurements show the molecular proximities of the silica framework sites to the structure-directing surfactant molecules and establish local Si-O-Si bonding connectivities in these materials.

S. C. Christiansen;东元 赵;M. T. Janicke;C. C. Landry;G. D. Stucky;B. F. Chmelka

Journal of the American Chemical Society

2001