Chun Wang

A general chelate-assisted co-assembly to metallic nanoparticles-incorporated ordered mesoporous carbon catalysts for Fischer-Tropsch synthesis.

The organization of different nano objects with tunable sizes, morphologies, and functions into integrated nanostructures is critical to the development of novel nanosystems that display high performances in sensing, catalysis, and so on. Herein, using acetylacetone as a chelating agent, phenolic resol as a carbon source, metal nitrates as metal sources, and amphiphilic copolymers as a template, we demonstrate a chelate-assisted multicomponent coassembly method to synthesize ordered mesoporous carbon with uniform metal-containing nanoparticles. The obtained nanocomposites have a 2-D hexagonally arranged pore structure, uniform pore size (~4.0 nm), high surface area (~500 m(2)/g), moderate pore volume (~0.30 cm(3)/g), uniform and highly dispersed Fe(2)O(3) nanoparticles, and constant Fe(2)O(3) contents around 10 wt %. By adjusting acetylacetone amount, the size of Fe(2)O(3) nanoparticles is readily tunable from 8.3 to 22.1 nm. More importantly, it is found that the metal-containing nanoparticles are partially embedded in the carbon framework with the remaining part exposed in the mesopore channels. This unique semiexposure structure not only provides an excellent confinement effect and exposed surface for catalysis but also helps to tightly trap the nanoparticles and prevent aggregating during catalysis. Fischer-Tropsch synthesis results show that as the size of iron nanoparticles decreases, the mesoporous Fe-carbon nanocomposites exhibit significantly improved catalytic performances with C(5+) selectivity up to 68%, much better than any reported promoter-free Fe-based catalysts due to the unique semiexposure morphology of metal-containing nanoparticles confined in the mesoporous carbon matrix.

An Interface Coassembly in Biliquid Phase: Toward Core-Shell Magnetic Mesoporous Silica Microspheres with Tunable Pore Size.

Core-shell magnetic mesoporous silica microspheres (Magn-MSMs) with tunable large mesopores in the shell are highly desired in biocatalysis, magnetic bioseparation, and enrichment. In this study, a shearing assisted interface coassembly in n-hexane/water biliquid systems is developed to synthesize uniform Magn-MSMs with magnetic core and mesoporous silica shell for an efficient size-selective biocatalysis. The synthesis features the rational control over the electrostatic interaction among cationic surfactant molecules, silicate oligomers, and Fe3O4@RF microspheres (RF: resorcinol formaldehyde) in the presence of shearing-regulated solubilization of n-hexane in surfactant micelles. Through this multicomponent interface coassembly, surfactant-silica mesostructured composite has been uniformly deposited on the Fe3O4@RF microspheres, and core-shell Magn-MSMs are obtained after removing the surfactant and n-hexane. The obtained Magn-MSMs possess excellent water dispersibility, uniform diameter (600 nm), large and tunable perpendicular mesopores (5.0-9.0 nm), high surface area (498-623 m(2)/g), large pore volume (0.91-0.98 cm(3)/g), and high magnetization (34.5-37.1 emu/g). By utilization of their large and open mesopores, Magn-MSMs with a pore size of about 9.0 nm have been demonstrated to be able to immobilize a large bioenzyme (trypsin with size of 4.0 nm) with a high loading capacity of ∼97 μg/mg via chemically binding. Magn-MSMs with immobilized trypsin exhibit an excellent convenient and size selective enzymolysis of low molecular proteins in the mixture of proteins of different sizes and a good recycling performance by using the magnetic separability of the microspheres.

Magnetic yolk–shell mesoporous silica microspheres with supported Au nanoparticles as recyclable high-performance nanocatalysts

Correction for ‘Magnetic yolk–shell mesoporous silica microspheres with supported Au nanoparticles as recyclable high-performance nanocatalysts’ by Yonghui Deng et al., J. Mater. Chem. A, 2015, DOI: 10.1039/c4ta06967f.

A versatile ethanol-mediated polymerization of dopamine for efficient surface modification and the construction of functional core–shell nanostructures

A versatile ethanol-mediated oxidative polymerization of dopamine is demonstrated for the effective surface modification of nanomaterials. The presence of ethanol is found to significantly slow down the polymerization rate of dopamine and make the surface modification of nanomaterials with polydopamine more controllable in comparison to the water-phase polymerization. Various nanomaterials with different morphologies and surface properties, including one-dimensional (1-D) CNTs and iron oxide nanorods, 2-D nanodiscs, silver nanocubes and magnetite particles, were successfully modified by a layer of PDA with a controllable thickness from 5 to 100 nm, giving rise to PDA-shelled nanocomposites with well-defined structures and excellent water dispersibility. As exemplified by the case of magnetite particles, the PDA coating can dramatically reduce the cytotoxicity of nanomaterials and enhance their biocompatibility. This method is facile and particularly suitable for the surface engineering of nanomaterials, and thus promising for designing various functional nanostructures for a broad range of applications, such as drug delivery, protein purification, enzyme immobilization, and chemo/biosensing.

Magnetic yolk-shell structured anatase-based microspheres loaded with Au nanoparticles for heterogeneous catalysis

AbstractMagnetic yolk-shell structured anatase-based microspheres were fabricated through successive and facile sol-gel coating on magnetite particles, followed by annealing treatments. Upon loading with gold nanoparticles, the obtained functional magnetic microspheres as heterogeneous catalysts showed superior performance in catalyzing the epoxidation of styrene with extraordinary high conversion (89.5%) and selectivity (90.8%) towards styrene oxide. It is believed that the construction process of these fascinating materials features many implications for creating other functional nanocomposites.

Hollow TiO2–X porous microspheres composed of well-crystalline nanocrystals for high-performance lithium-ion batteries

Hollow TiO2–X porous microspheres consisted of numerous well-crystalline nanocrystals with superior structural integrity and robust hollow interior were synthesized by a facile sol-gel template-assisted approach and two-step carbonprotected calcination method, together with hydrogenation treatment. They exhibit a uniform diameter of ~470 nm with a thin porous wall shell of ~50 nm in thickness. The Brunauer-Emmett-Teller (BET) surface area and pore volume are ~19 m2/g and 0.07 cm3/g, respectively. These hollow TiO2–X porous microspheres demonstrated excellent lithium storage performance with stable capacity retention for over 300 cycles (a high capacity of 151 mAh/g can be obtained up to 300 cycles at 1 C, retaining 81.6% of the initial capacity of 185 mAh/g) and enhanced rate capability even up to 10 C (222, 192, 121, and 92.1 mAh/g at current rates of 0.5, 1, 5, and 10 C, respectively). The intrinsic increased conductivity of the hydrogenated TiO2 microspheres and their robust hollow structure beneficial for lithium ion-electron diffusion and mitigating the structural strain synergistically contribute to the remarkable improvements in their cycling stability and rate performance.

A Quasi-Solid-State Li-Ion Capacitor Based on Porous TiO2 Hollow Microspheres Wrapped with Graphene Nanosheets

The quasi-solid-state Li-ion capacitor is demonstrated with graphene nanosheets prepared by an electrochemical exfoliation as the positive electrode and the porous TiO2 hollow microspheres wrapped with the same graphene nanosheets as the negative electrode, using a Li-ion conducting gel polymer electrolyte. This device may be the key to bridging the gap between conventional lithium-ion batteries and supercapacitors, meanwhile meeting the safety demands of electronic devices.

Mesoporous TiO2 Mesocrystals: Remarkable Defects-Induced Crystallite-Interface Reactivity and Their in Situ Conversion to Single Crystals.

Oriented self-assembly between inorganic nanocrystals and surfactants is emerging as a route for obtaining new mesocrystalline semiconductors. However, the actual synthesis of mesoporous semiconductor mesocrystals with abundant surface sites is extremely difficult, and the corresponding new physical and chemical properties arising from such an intrinsic porous mesocrystalline nature, which is of fundamental importance for designing high-efficiency nanostructured devices, have been rarely explored and poorly understood. Herein, we report a simple evaporation-driven oriented assembly method to grow unprecedented olive-shaped mesoporous TiO2 mesocrystals (FDU-19) self-organized by ultrathin flake-like anatase nanocrystals (∼8 nm in thickness). The mesoporous mesocrystals FDU-19 exhibit an ultrahigh surface area (∼189 m2/g), large internal pore volume (0.56 cm3/g), and abundant defects (oxygen vacancies or unsaturated Ti3+ sites), inducing remarkable crystallite-interface reactivity. It is found that the mesocrystals FDU-19 can be easily fused in situ into mesoporous anatase single crystals (SC-FDU-19) by annealing in air. More significantly, by annealing in a vacuum (∼4.0 × 10–5 Pa), the mesocrystals experience an abrupt three-dimensional to two-dimensional structural transformation to form ultrathin anatase single-crystal nanosheets (NS-FDU-19, ∼8 nm in thickness) dominated by nearly 90% exposed reactive (001) facets. The balance between attraction and electrostatic repulsion is proposed to determine the resulting geometry and dimensionality. Dye-sensitized solar cells based on FDU-19 and SC-FDU-19 samples show ultrahigh photoconversion efficiencies of up to 11.6% and 11.3%, respectively, which are largely attributed to their intrinsic single-crystal nature as well as high porosity. This work gives new understanding of physical and chemical properties of mesoporous semiconductor mesocrystals and opens up a new pathway for designing various single-crystal semiconductors with desired mesostructures for applications in catalysis, sensors, drug delivery, optical devices, etc.

A Shear Stress Regulated Assembly Route to Silica Nanotubes and Their Closely Packed Hollow Mesostructures

Ready to load: A shear stress regulated assembly route has been used to fabricate silica nanotubes and hollow mesostructures thereof. The packed silica nanotubes were employed as support for loading gold nanoparticles for efficiently catalyzing the epoxidation of styrene with high conversion and selectivity towards styrene oxide.

A systematic investigation of the formation of ordered mesoporous silicas using poly(ethylene oxide)-b-poly(methyl methacrylate) as the template

Two different approaches, the conventional solvent evaporation induced self-assembly (EISA) and the novel solvent evaporation induced aggregating assembly (EIAA), were employed to synthesize ordered mesoporous silicas (OMSs), respectively, by using amphiphilic diblock copolymer poly(ethylene oxide)-b-poly(methyl methacrylate) as the template, with an aim to systematically investigate the difference of the two approaches and their effect on the textural properties of the obtained porous materials. The mesoporous silicas synthesized via the two methods possess face centered cubic (fcc) mesostructure, large pore size and high surface area. However, compared with the OMSs with a film-like morphology from EISA, the OMSs from the EIAA have a particle-like morphology, thinner pore wall and higher surface area, which is favorable for their applications. More importantly, the novel EIAA process is more versatile and can be used to synthesize ordered mesoporous silicas and silica-based nanostructured materials with different morphologies. By introducing ethanol as the additive in the EIAA system, unique mesoporous silica spheres with a diameter of 1–5 μm, large pore size (∼16.8 nm), huge window size (∼8.9 nm), and high surface area (∼482 m2 g−1) can be synthesized. Through increasing the content of water, uniform silica hollow spheres (20–40 nm in diameter) and silica nanotubes (diameter ∼30 nm) can be obtained by using templates with higher and lower molecular weight, respectively.