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Showing papers on "Mesoporous material published in 2010"


Journal ArticleDOI
TL;DR: It is shown that the capacitive charge-storage properties of mesoporous films of iso-oriented alpha-MoO(3) are superior to those of either Mesoporous amorphous material or non-porous crystalline MoO( 3).
Abstract: Capacitive energy storage is technologically attractive because of its short charging times and its ability to deliver more power than batteries. The capacitive charge-storage properties of mesoporous films of MoO3 with iso-oriented grains now lead to pseudocapacitive materials that offer increased energy density while still maintaining high power density.

2,643 citations


Journal ArticleDOI
TL;DR: A simple one-step NaCl-assisted microwave-solvothermal method has been developed for the preparation of monodisperse α-Fe2O3 mesoporous microspheres, and high photocatalytic activities in the degradation of salicylic acid are observed.
Abstract: A simple one-step NaCl-assisted microwave-solvothermal method has been developed for the preparation of monodisperse α-Fe2O3 mesoporous microspheres. In this approach, Fe(NO3)3 · 9H2O is used as the iron source, and polyvinylpyrrolidone (PVP) acts as a surfactant in the presence of NaCl in mixed solvents of H2O and ethanol. Under the present experimental conditions, monodisperse α-Fe2O3 mesoporous microspheres can form via oriented attachment of α-Fe2O3 nanocrystals. One of the advantages of this method is that the size of α-Fe2O3 mesoporous microspheres can be adjusted in the range from ca. 170 to ca. 260 nm by changing the experimental parameters. High photocatalytic activities in the degradation of salicylic acid are observed for α-Fe2O3 mesoporous microspheres with different specific surface areas.

2,381 citations


Journal ArticleDOI
TL;DR: Nonprecious-metal and metal-free catalysts for ORR have attracted enormous interest as an alternative to platinum-based catalysts and would aid attempts to elucidate the correlation between the structure, composition, and electrochemical activity of nitrogen-doped carbon materials.
Abstract: The cathodic oxygen-reduction reaction (ORR) is one of the most crucial factors in the performance of a fuel cell. The development of efficient ORR electrocatalysts is thus of great significance for the commercialization of fuel cells. Platinum-based materials have long been investigated as active catalysts for ORR; however, the large-scale application of fuel cells has been hampered by the high cost and inadequacy of this metal. Recently, nonprecious-metal and metal-free catalysts for ORR have attracted enormous interest as an alternative to platinum-based catalysts. In particular, nitrogen-doped carbon materials, which are typical metal-free catalysts, exhibit excellent electrocatalytic activity for ORR as a result of their unique electronic properties derived from the conjugation between the nitrogen lone-pair electrons and the graphene p system. Generally, nitrogen-doped carbon materials can be prepared by the pyrolysis of transition-metal macrocyclic compounds or mixtures of metal salts and nitrogen-containing precursors. In these processes, the transition metals play an important role not only in the formation of graphitic frameworks, but also in the introduction of nitrogen active sites. Drawbacks are the use of expensive precursors and the need for extra steps to remove metal species. Furthermore, metal nanoparticles encapsulated in the graphite framework still remain even after a tedious removal process. The nature of the nitrogen atoms in nitrogen-doped carbon materials and whether they are really the active catalytic sites is still controversial. Thus, the development of nitrogen-doped carbon materials with excellent electrochemical performance but without any metal components is an urgent issue. Such materials would not only be promising candidates for ORR catalysts but would aid attempts to elucidate the correlation between the structure, composition, and electrochemical activity of nitrogen-doped carbon materials.

1,320 citations


Journal ArticleDOI
TL;DR: The fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.
Abstract: The precise control of the size, morphology, surface chemistry, and assembly process of each component is important to construction of integrated functional nanocomposites. We report here the fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels. The well-designed microspheres have high magnetization (18.6 emu/g), large surface area (236 m(2)/g), highly open mesopores (approximately 2.2 nm), and stably confined but accessible Au nanoparticles and, as a result, show high performance in catalytic reduction of 4-nitrophenol (with conversion of 95% in 12 min), styrene epoxidation with high conversion (72%) and selectivity (80%), especially convenient magnetic separability, long life and good reusability. The unique nanostructure makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.

864 citations


Journal ArticleDOI
TL;DR: Mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm(-2) under standard conditions and a considerable change in the absorption coefficient and onset properties, critical aspects for hematites as a solar energy converter, as a function of the sintering temperature are revealed.
Abstract: Sustainable hydrogen production through photoelectrochemical water splitting using hematite (α-Fe2O3) is a promising approach for the chemical storage of solar energy, but is complicated by the material’s nonoptimal optoelectronic properties. Nanostructuring approaches have been shown to increase the performance of hematite, but the ideal nanostructure giving high efficiencies for all absorbed light wavelengths remains elusive. Here, we report for the first time mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm−2 under standard conditions (AM 1.5G 100 mW cm−2, 1.23 V vs reversible hydrogen electrode, RHE) and over 1.0 mA cm−2 before the dark current onset (1.55 V vs RHE). The sintering temperature is found to increase the average particle size, and have a drastic effect on the photoactivity. X-ray photoelectron spectroscopy and magnetic measurements using a SQUID magnetometer link this effect to the diffusion and incorp...

854 citations


Journal ArticleDOI
18 Nov 2010-Nature
TL;DR: This work describes the development of a photonic mesoporous inorganic solid that is a cast of a chiral nematic liquid crystal formed from nanocrystalline cellulose, and is the first materials to combine mesoporosity with long-range chiral ordering that produces photonic properties.
Abstract: Chirality at the molecular level is found in diverse biological structures, such as polysaccharides, proteins and DNA, and is responsible for many of their unique properties. Introducing chirality into porous inorganic solids may produce new types of materials that could be useful for chiral separation, stereospecific catalysis, chiral recognition (sensing) and photonic materials. Template synthesis of inorganic solids using the self-assembly of lyotropic liquid crystals offers access to materials with well-defined porous structures, but only recently has chirality been introduced into hexagonal mesostructures through the use of a chiral surfactant. Efforts to impart chirality at a larger length scale using self-assembly are almost unknown. Here we describe the development of a photonic mesoporous inorganic solid that is a cast of a chiral nematic liquid crystal formed from nanocrystalline cellulose. These materials may be obtained as free-standing films with high surface area. The peak reflected wavelength of the films can be varied across the entire visible spectrum and into the near-infrared through simple changes in the synthetic conditions. To the best of our knowledge these are the first materials to combine mesoporosity with long-range chiral ordering that produces photonic properties. Our findings could lead to the development of new materials for applications in, for example, tuneable reflective filters and sensors. In addition, this type of material could be used as a hard template to generate other new materials with chiral nematic structures.

801 citations


Journal ArticleDOI
TL;DR: The measure of hemolysis is used to evaluate the toxicity of nonporous and porous silica nanoparticles with varied sizes and investigates the effects of porous structure and integrity on the nanoparticle-cell interaction, revealing that pore structure is critical in cell-nanoparticle interactions.
Abstract: This paper uses the measure of hemolysis to evaluate the toxicity of nonporous and porous silica nanoparticles with varied sizes and investigates the effects of porous structure and integrity on the nanoparticle−cell interaction. The results show that both nonporous and porous silica cause red blood cell membrane damage in a concentration- and size-dependent manner. In the case of mesoporous silica nanoparticles, the size-dependent hemolysis effect is only present when the nanoparticles have long-range ordered porous structure, revealing that pore structure is critical in cell−nanoparticle interactions. Mesoporous silica nanoparticles show lower hemolytic activity than their nonporous counterparts of similar size, likely due to fewer silanol groups on the cell-contactable surface of the porous silica nanoparticles. The extent of hemolysis by mesoporous silica nanoparticles increases as the pore structure is compromised by mild aging in phosphate-buffered solutions, initiating mesopore collapse. The pore i...

717 citations


Journal ArticleDOI
26 Jan 2010-ACS Nano
TL;DR: A novel "structural difference-based selective etching" strategy has been developed to fabricate hollow/rattle-type mesoporous nanostructures, which show high loading capacity for anticancer drug (doxorubicin) and show ultrafast immobilization of protein-based biomolecules (hemoglobin).
Abstract: A novel "structural difference-based selective etching" strategy has been developed to fabricate hollow/rattle-type mesoporous nanostructures, which was achieved by making use of the structural differences, rather than traditional compositional differences, between the core and the shell of a silica core/mesoporous silica shell structure to create hollow interiors. Highly dispersed hollow mesoporous silica spheres with controllable particle/pore sizes could be synthesized by this method, which show high loading capacity (1222 mg/g) for anticancer drug (doxorubicin). Hemolyticity and cytotoxicity assays of hollow mesoporous silica spheres were conducted, and the synthesized hollow mesoporous silica spheres with large pores show ultrafast immobilization of protein-based biomolecules (hemoglobin). On the basis of this strategy, different kinds of heterogeneous rattle-type nanostructures with inorganic nanocrystals, such as Au, Fe(2)O(3), and Fe(3)O(4) nanoparticles, as the core and mesoporous silica as the shell were also prepared. This strategy could be extended as a general approach to synthesize various hollow/rattle-type nanostructures by creating adequate structural differences between cores and shells in core/shell structures in nanoscale.

600 citations


Journal ArticleDOI
01 Feb 2010-Carbon
TL;DR: In this article, five nanoporous carbons (NPCs) were prepared by polymerizing and then carbonizing carbon precursor of furfuryl alcohol accommodated in a porous metal-organic framework (MOF-5, [Zn4O(bdc)3], bdc = 1,4-benzenedicarboxylate) template.

596 citations


Journal ArticleDOI
03 Sep 2010-ACS Nano
TL;DR: The capability of Fe(3)O(4)@mSiO(2) nanocapsules as contrast agents of MRI was demonstrated both in vitro and in vivo, indicating the simultaneous imaging and therapeutic multifunctionalities of the composite nanocapules.
Abstract: A potential platform for simultaneous anticancer drug delivery and MRI cell imaging has been demonstrated by uniform hollow inorganic core/shell structured multifunctional mesoporous nanocapsules, which are composed of functional inorganic (Fe3O4, Au, etc.) nanocrystals as cores, a thin mesoporous silica shell, and a huge cavity in between. The synthetic strategy for the creation of huge cavities between functional core and mesoporous silica shell is based on a structural difference based selective etching method, by which solid silica middle layer of Fe2O3@SiO2@mSiO2 (or Au@SiO2@mSiO2) composite nanostructures was selectively etched away while the mesoporous silica shell could be kept relatively intact. The excellent biocompatibility of obtained multifunctional nanocapsules (Fe3O4@mSiO2) was demonstrated by very low cytotoxicity against various cell lines, low hemolyticity against human blood red cells and no significant coagulation effect against blood plasma. The cancer cell uptake and intracellular lo...

587 citations


Journal ArticleDOI
TL;DR: The reversible transformation between the microporous and mesoporous MOFs triggered by solvent or/and temperature perturbation is demonstrated and could be the stationary phase in high-performance liquid chromatography (HPLC) for size-exclusion separation of large dye molecules.
Abstract: For the first time, three novel metal−organic framework (MOF) isomers with hierachical channel sizes of nonpore or micropore or mesopore were successfully prepared by simply controlling the amounts of solvent or/and reaction temperatures/time. Strikingly, we have demonstrated the reversible transformation between the microporous and mesoporous MOFs triggered by solvent or/and temperature perturbation. The desolvated microporous MOF has been evaluated to be a promising luminescent probe for detecting small molecules, and the mesoporous MOF could be the stationary phase in high-performance liquid chromatography (HPLC) for size-exclusion separation of large dye molecules.

Journal ArticleDOI
TL;DR: In this article, the synthesis and characterization of monodisperse coreshell-structured Fe3O4/Er3+/Tm3+ nanocomposites with mesoporous, up-conversion luminescent, and magnetic properties were reported for controlled drug release.
Abstract: The synthesis (by a facile two-step sol-gel process), characterization, and application in controlled drug release is reported for monodisperse coreshell-structured Fe3O4@nSiO(2)@mSiO(2)@NaYF4: Yb3+; Er3+/Tm3+ nanocomposites with mesoporous, up-conversion luminescent, and magnetic properties. The nanocomposites show typical ordered mesoporous characteristics and a monodisperse spherical morphology with narrow size distribution (around 80 nm). In addition, they exhibit high magnetization (38.0 emu g(-1), thus it is possible for drug targeting under a foreign magnetic field) and unique up-conversion emission (green for Yb3+/Er3+ and blue for Yb3+/Tm3+) under 980 nm laser excitation even after loading with drug molecules. Drug release tests suggest that the multifunctional nanocomposites have a controlled drug release property. Interestingly, the up-conversion emission intensity of the multifunctional carrier increases with the released amount of model drug, thus allowing the release process to be monitored and tracked by the change of photoluminescence intensity. This composite can act as a multifunctional drug carrier system, which can realize the targeting and monitoring of drugs simultaneously.

Journal ArticleDOI
TL;DR: Owing to the covalent linkages between catalytic sites in the frameworks, FeP-CMP can be recycled with good retention of its porous structure and allows for large-scale transformation, demonstrating the usefulness of CMPs in the exploration of built-in heterogeneous catalysts.
Abstract: This article describes the synthesis and functions of a porous catalytic framework based on conjugated micro- and mesoporous polymers with metalloporphyrin building blocks (FeP-CMP). FeP-CMP was newly synthesized via a Suzuki polycondensation reaction and was developed as a heterogeneous catalyst for the activation of molecular oxygen to convert sulfide to sulfoxide under ambient temperature and pressure. FeP-CMP is intriguing because the polymer skeleton itself is built from catalytic moieties and serves as built-in catalysts, bears inherent open nanometer-scale pores that are accessible for substrates, and possesses large surface areas (1270 m2 g−1) that facilitate the transformation reaction. It is highly efficient with high conversion (up to 99%) and a large turnover number (TON = 97,320), is widely applicable to various sulfides covering from aromatic to alkyl and cyclic substrates, displays high selectivity (up to 99%) to form corresponding sulfoxides, and is highly chemoselective for the oxidation ...

Journal ArticleDOI
TL;DR: Results indicated that the crystal facet of Co(3)O(4) played an essential role in determining its catalytic oxidation performance, and was significantly more active for ethylene oxidation than the Co( 3)O (4) nanosheets.
Abstract: Low-temperature catalysts of mesoporous Co3O4 and AU/Co3O4 with high catalytic activities for the trace ethylene oxidation at 0 degrees C are reported in this paper. The catalysts were prepared by using the nanocasting method, and the mesostructure was replicated from three-dimensional (3D) cubic KIT-6 silicas. High resolution transmission electron microscopy (HRTEM) studies revealed that {110} facets were the exposed active surfaces in the mesoporous Co3O4, whereas the Co3O4 nanosheets prepared by the precipitation method exhibited the most exposed {112} facets. We found that the mesoporous Co3O4 was significantly more active for ethylene oxidation than the Co3O4 nanosheets. The results indicated that the crystal facet {110} of Co3O4 played an essential role in determining its catalytic oxidation performance. The synthesized Au/Co3O4 materials, in which the gold nanoparticles were assembled into the pore walls of the Co3O4 mesoporous support, exhibited stable, highly dispersed, and exposed gold sites. Gold nanoparticles present on Co3O4 readily produced surface-active oxygen species and promoted ethylene oxidation to achieve a 76% conversion at 0 degrees C, which is the highest conversion reported yet.

Journal ArticleDOI
TL;DR: The present approach using a zeolite structure-directing functional group contained in a surfactant would be suitable for the synthesis of other related nanomorphous zeolites in the future.
Abstract: Zeolite MFI nanosheets of 2-nm thickness have been hydrothermally synthesized via cooperative assembly between silica and an organic surfactant, which is functionalized with a diquaternary ammonium group. The zeolite nanosheets have been further assembled into their ordered multilamellar mesostructure through hydrophobic interactions between the surfactant tails located outside the zeolite nanosheet. This assembly process involves successive transformations from an initially hexagonal mesophase to a multilamellar mesophase without crystallinity and then to a lamellar mesophase with a crystalline zeolite framework. The mesopore volume in the interlamellar space could be retained by supporting the zeolite nanosheets with silica pillars, as in pillared clays, even after surfactant removal by calcination. The mesopore diameters could be controlled according to the surfactant tail lengths. Due to the interlamellar structural coherence, the hierarchically mesoporous/microporous zeolite could exhibit small-angle X-ray diffraction peaks up to the fourth-order reflections corresponding to the interlayer distance. In addition, an Ar adsorption analysis and transmission electron microscopic investigation indicated that the pillars were highly likely to be built with an MFI structure. The present approach using a zeolite structure-directing functional group contained in a surfactant would be suitable for the synthesis of other related nanomorphous zeolites in the future.

Journal ArticleDOI
TL;DR: This work presents a simple and robust, chemically controlled process for synthesizing size-controlled noble metal or bimetallic nanocrystallites embedded within the porous structure of ordered mesoporous carbon (OMC).
Abstract: Shape- and size-controlled supported metal and intermetallic nanocrystallites are of increasing interest because of their catalytic and electrocatalytic properties. In particular, intermetallics PtX (X 5 Bi, Pb, Pd, Ru) are very attractive because of their high activity as fuel-cell anode catalysts for formic acid or methanol oxidation. These are normally synthesized using high-temperature techniques, but rigorous size control is very challenging. Even low-temperature techniques typically produce nanoparticles with dimensions much greater than the optimum <6 nm required for fuel cell catalysis. Here, we present a simple and robust, chemically controlled process for synthesizing size-controlled noble metal or bimetallic nanocrystallites embedded within the porous structure of ordered mesoporous carbon (OMC). By using surface-modified ordered mesoporous carbon to trap the metal precursors, nanocrystallites are formed with monodisperse sizes as low as 1.5 nm, which can be tuned up to ∼3.5 nm. To the best of our knowledge, 3-nm ordered mesoporous carbon-supported PtBi nanoparticles exhibit the highest mass activity for formic acid oxidation reported to date, and over double that of Pt–Au.

Journal ArticleDOI
24 Feb 2010-ACS Nano
TL;DR: It is demonstrated, for the first time, how the preparation and application of templated carbide-derived carbon (CDC) can overcome the present limitations and show the route for dramatic performance enhancement.
Abstract: Microporous carbons, produced by selective etching of metal carbides in a chlorine-containing environment, offer narrow distribution of micropores and one of the highest specific capacitances reported when used in electrical double layer capacitors (EDLC) with organic electrolytes. Previously, the small micropores in these carbons served as an impediment to ion transport and limited the power storage characteristics of EDLC. Here we demonstrate, for the first time, how the preparation and application of templated carbide-derived carbon (CDC) can overcome the present limitations and show the route for dramatic performance enhancement. The ordered mesoporous channels in the produced CDC serve as ion-highways and allow for very fast ionic transport into the bulk of the CDC particles. The enhanced transport led to 85% capacitance retention at current densities up to ∼20 A/g. The ordered mesopores in silicon carbide precursor also allow the produced CDC to exhibit a specific surface area up to 2430 m2/g and a ...

Journal ArticleDOI
TL;DR: An attempt has been made to rationalize the synthesis of extra-large-pore zeolites in terms of the synthesis mechanism, the directing effect of the organic structure directing agent (OSDA), the framework atoms, and the gel concentration.
Abstract: The conditions required to produce zeolites with low framework density and extra-large pores are discussed. Correlations between framework stability and geometrical and topological descriptors are presented. An attempt has been made to rationalize the synthesis of extra-large-pore zeolites in terms of the synthesis mechanism, the directing effect of the organic structure directing agent (OSDA), the framework atoms, and the gel concentration. Extra-large-pore zeolites, including the recently discovered chiral mesoporous ITQ-37, are described and their catalytic and adsorption properties discussed. Finally, strategies are presented for the preparation of extra-large-pore zeolites with different pore topologies that can fulfill pre-established catalytic and adsorption targets.

Journal ArticleDOI
TL;DR: The approach presented in this study demonstrates that simultaneous control of the physical properties, including specific surface area, mesoporosity, crystallinity, morphology, and monodispersity, of the titania materials can be achieved by a facile sol-gel synthesis and solvothermal process.
Abstract: Monodisperse mesoporous anatase titania beads with high surface areas and tunable pore size and grain diameter have been prepared through a combined sol−gel and solvothermal process in the presence of hexadecylamine (HDA) as a structure-directing agent The monodispersity of the resultant titania beads, along with the spherical shape, can be controlled by varying the amount of structure-directing agent involved in the sol−gel process The diameter of the titania beads is tunable from ∼320 to 1150 nm by altering the hydrolysis and condensation rates of the titanium alkoxide The crystallite size, specific surface area (from 89 to 120 m2/g), and pore size distribution (from 14 to 23 nm) of the resultant materials can be varied through a mild solvothermal treatment in the presence of varied amounts of ammonia On the basis of the results of small-angle XRD, high-resolution SEM/TEM, and gas sorption characterization, a mechanism for the formation of the monodisperse precursor beads has been proposed to illust

Journal ArticleDOI
TL;DR: In this article, mesoporous beads are used as a scattering layer on top of a transparent, 6-μm-thick, nanocrystalline TiO 2 film.
Abstract: Submicrometer-sized (830 ± 40 nm) mesoporous TiO 2 beads are used to form a scattering layer on top of a transparent, 6-μm-thick, nanocrystalline TiO 2 film. According to the Mie theory, the large beads scatter light in the region of 600-800 nm. In addition, the mesoporous structure offers a high surface area, 89.1 m 2 g -1 , which allows high dye loading. The dual functions of light scattering and electrode participation make the mesoporous TiO 2 beads superior candidates for the scattering layer in dye-sensitized solar cells. A high efficiency of 8.84% was achieved with the mesoporous beads as a scattering layer, compared with an efficiency of 7.87% for the electrode with the scattering layer of 400-nm TiO 2 of similar thickness.

Journal ArticleDOI
TL;DR: Mesoporous LiFePO4/C nanocomposites exhibit superior electrochemical performance and ultra-high specific power density, which makes this architecture suitable for high power applications such as hybrid electric vehicles (HEVs) and stationary energy storage for smart grids.
Abstract: Hexagonally ordered mesoporous LiFePO4/C nanocomposites can be synthesized with LiFePO4 nanoparticles embedded in an interconnected carbon framework. Mesoporous LiFePO4/C nanocomposites exhibit superior electrochemical performance and ultra-high specific power density, which makes this architecture suitable for high power applications such as hybrid electric vehicles (HEVs) and stationary energy storage for smart grids.

Journal ArticleDOI
05 Feb 2010-Small
TL;DR: The results indicate the potential of Fe(3)O(4)@SiO(2) hollow mesoporous spheres for drug loading and delivery into cancer cells to induce cell death.
Abstract: Rattle-type Fe(3)O(4)@SiO(2) hollow mesoporous spheres with different particle sizes, different mesoporous shell thicknesses, and different levels of Fe(3)O(4) content are prepared by using carbon spheres as templates. The effects of particle size and concentration of Fe(3)O(4)@SiO(2) hollow mesoporous spheres on cell uptake and their in vitro cytotoxicity to HeLa cells are evaluated. The spheres exhibit relatively fast cell uptake. Concentrations of up to 150 microg mL(-1) show no cytotoxicity, whereas a concentration of 200 microg mL(-1) shows a small amount of cytotoxicity after 48 h of incubation. Doxorubicin hydrochloride (DOX), an anticancer drug, is loaded into the Fe(3)O(4)@SiO(2) hollow mesoporous spheres, and the DOX-loaded spheres exhibit a somewhat higher cytotoxicity than free DOX. These results indicate the potential of Fe(3)O(4)@SiO(2) hollow mesoporous spheres for drug loading and delivery into cancer cells to induce cell death.

Journal ArticleDOI
TL;DR: In this article, the authors used ordered mesoporous carbons at high temperature to create nitrogen-doped carbon materials that exhibit significant activity for oxygen reduction reaction in acidic media.
Abstract: Ammonia treatment of ordered mesoporous carbons at high temperature results in the formation of nitrogen-doped carbon materials that exhibit significant activity for oxygen reduction reaction in acidic media. The new material shows an onset potential of only 80 mV below that of a commercial Pt-based catalyst, but a better stability.

Journal ArticleDOI
TL;DR: In this article, a hierarchical three-dimensional (3-D) mesostructures with small and large mesopores with pore diameters centered at 4.0 and 43 nm, respectively, have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams as a hard template, and ethylenediamine and carbon tetrachloride as precursors.
Abstract: Porous carbon nitride (CN) spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams (MCFs) as a hard template, and ethylenediamine and carbon tetrachloride as precursors. The resulting spherical CN materials have uniform diameters of ca. 4 μm, hierarchical three-dimensional (3-D) mesostructures with small and large mesopores with pore diameters centered at ca. 4.0 and 43 nm, respectively, a relatively high BET surface area of ∼550 m2/g, and a pore volume of 0.90 cm3/g. High-resolution transmission electron microscope (HRTEM) images, wide-angle X-ray diffraction (XRD) patterns, and Raman spectra demonstrate that the porous CN material has a partly graphitized structure. In addition, elemental analyses, X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FT-IR), and CO2 temperature-programmed desorption (CO2-TPD) show that the material has a high nitrogen content (17.8 wt%) with nitrogen-containing groups and abundant basic sites. The hierarchical porous CN spheres have excellent CO2 capture properties with a capacity of 2.90 mmol/g at 25 °C and 0.97 mmol/g at 75 °C, superior to those of the pure carbon materials with analogous mesostructures. This can be mainly attributed to the abundant nitrogen-containing basic groups, hierarchical mesostructure, relatively high BET surface area and stable framework. Furthermore, the presence of a large number of micropores and small mesopores also enhance the CO2 capture performance, owing to the capillary condensation effect.

Journal ArticleDOI
TL;DR: A novel direct method for preparing mesoporous ZnGa2O4 with a wormhole framework by an ion-exchange reaction at room temperature involving a mesoborous NaGaO2 colloid precursor is reported, which provides a means to overcome the problems associated with synthesizing multimetal Mesoporous materials.
Abstract: Mesoporous materials are of scientific and technological interest due to their potential applications in various areas. Over the past two decades, significant effort has been devoted to the synthesis of mesoporous materials. For instance, mesoporous silica and phosphate metal oxides have been synthesized and applied widely in many industrial processes. However, little progress has been made in the synthesis of mesoporous metal oxides containing more than one type of metal. To date, a limited number of routes including evaporation-induced self-assembly (EISA) and nonaqueous solvent methods have been developed to synthesize multimetallic mesoporous materials such as Pb3Nb4O13, [3] Bi20TiO32, [4] SrTiO3, MgTa2O6, CoxTi1 xO2 x, [5] and Ce1 xZrxO2. [6] In these routes, introducing surfactant molecules or a template is a general method used to construct the mesostructures. Challenges in using the template method to synthesize multimetallic mesoporous materials are uncontrolled phase separation in the multicomponent reactions and poor thermal and chemical stability of the resulting mesoporous structure. Maintaining the complete mesostructure during removal of the template by heating or chemical treatment is a key process for obtaining the expected mesostructures, and increases the uncertainty in a given synthetic route. In addition, to obtain a crystalline mesoporous material, high-temperature heat treatment is usually required for crystallization of the product. However, this process probably induces collapse of mesostructures. Recently, we developed a synthetic route to mesoporous multimetal oxides that uses the inorganic starting reactants directly as pore makers which aid in building the mesoporous structures of multimetal oxides and improve the thermal stability of the resulting mesostructure. However, in these reported synthetic routes, postcrystallization and introducing or removing an exotemplate are usually needed. In recent years, a route that does not require template removal, which was named “reactive hard templating”, was developed to synthesize porous TiN/carbon composite materials. In this route, the template consists of nanostructures of porous graphitic C3N4, which thermally decomposes completely during formation of porous TiN. This route provides a means to overcome the problems associated with synthesizing multimetal mesoporous materials. A simplified soft-chemistry route based on a reactive template is expected to allow synthesis to proceed at room temperature without requiring the introduction or removal of a template. Here we report a novel direct method for preparing mesoporous ZnGa2O4 with a wormhole framework by an ion-exchange reaction at room temperature involving a mesoporous NaGaO2 colloid precursor. The method does not require any additional processes and can be extended to prepare other porous materials, such as CoGa2O4 and NiGa2O4. The X-ray diffraction (XRD) pattern of NaGaO2 powder, which can be indexed as the orthorhombic phase (JCPDS 762151), is presented in Figure 1. Scanning electron microscopy (SEM) revealed that the powder particles are irregular in shape with little agglomeration, and most of the particles are larger than 500 nm in diameter (see Supporting Information). The as-prepared NaGaO2 powder can be dispersed in water to form a suspension. When the NaGaO2 suspension is illuminated with a 532 nm laser, a Tyndall effect is observed, that is, the suspension behaves as a colloid (see Supporting Information). Multimodal measurements of particle size distribution by dynamic light scattering show that the NaGaO2 colloidal particles exhibit two peak distributions: 20 % of the particles have an average size of 70 nm, and 80 % an average size of 335 nm. Most particulate or macroscopic materials in contact with a liquid acquire an electric charge on their surfaces. The zeta potential is an important and useful indicator of this charge that can be used to predict the stability of colloidal suspensions. The zeta potential of NaGaO2 colloidal particles is 21.57 mV (pH 6). This is lower than the critical zeta potential of 30 mV for maintaining colloid stability in an aqueous system, that is, the colloidal particles are slightly [*] S. C. Yan, J. Gao, M. Yang, X. X. Fan, L. J. Wan, Prof. Y. Zhou, Prof. Z. G. Zou Ecomaterials and Renewable Energy Research Center National Laboratory of Solid State Microstructures, Nanjing University, 22 Hankou Road, Nanjing 210093 (China) E-mail: zgzou@nju.edu.cn

Journal ArticleDOI
Hyehyeon Kim1, Saehee Kim1, Chiyoung Park1, Hyemi Lee1, Heon Joo Park1, Chulhee Kim1 
TL;DR: Mesoporous silica nanoparticles have been demonstrated to be excellent hosts for molecules of various sizes, shapes, and functionalities and to provide Si-MPs with unique properties for stimuli-responsive controlled delivery applications.
Abstract: Mesoporous silica nanoparticles (Si-MPs) have been demonstrated to be excellent hosts for molecules of various sizes, shapes, and functionalities. [ 5 ] The organically functionalized Si-MPs have unique structural features such as environmentally stable mesoporous structures, large surface area, tunable pore size, and well-defi ned surface properties. [ 3 ] In particular, the facile surface functionalization of Si-MPs and their effi cient internalization into cells provided Si-MPs with unique properties for stimuli-responsive controlled delivery applications. [ 2 , 4 ]

Journal ArticleDOI
TL;DR: This construct allows effective dye sensitization, electrolyte infiltration, and charge collection from both the mesoporous and the PC layers, opening up additional parameter space for effective light management by harvesting PC-induced resonances.
Abstract: We present a material assembly route for the manufacture of dye-sensitized solar cells, coupling a high-surface mesoporous layer to a three-dimensional photonic crystal (PC). Material synthesis aided by self-assembly on two length scales provided electrical and pore connectivity at the mesoporous and the microporous level. This construct allows effective dye sensitization, electrolyte infiltration, and charge collection from both the mesoporous and the PC layers, opening up additional parameter space for effective light management by harvesting PC-induced resonances.

Journal ArticleDOI
TL;DR: It is demonstrated that these group V transition metal oxides can be readily produced with a high degree of crystallographic alignment on virtually any substrate in contrast to classical solution-phase epitaxy which requires the use of a single-crystalline substrate to achieve oriented crystal growth.
Abstract: Amphiphilic block copolymers are very attractive as templates to produce inorganic architectures with nanoscale periodicity because of their ability to form soft superstructures and to interact with inorganic materials. In this paper, we report the synthesis and electrochemical properties of highly ordered mesoporous T-Nb2O5, L-Ta2O5, and TaNbO5 solid solution thin films with iso-oriented layered nanocrystalline domains. These oxide materials were fabricated by coassembly of inorganic sol−gel reagents with a poly(ethylene-co-butylene)-b-poly(ethylene oxide) diblock copolymer, referred to as KLE. We establish that all materials employed here are highly crystalline and have an ordered cubic pore-solid architecture after thermal treatment. We also demonstrate that these group V transition metal oxides can be readily produced with a high degree of crystallographic alignment on virtually any substrate in contrast to classical solution-phase epitaxy which requires the use of a single-crystalline substrate to ac...

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TL;DR: Mesoporous α-Fe2O3 materials were prepared in large quantity by the soft template synthesis method using the triblock copolymer surfactant F127 as the template as mentioned in this paper.
Abstract: Mesoporous α-Fe2O3 materials were prepared in large quantity by the soft template synthesis method using the triblock copolymer surfactant F127 as the template. Nitrogen adsorption−desorption isothermal measurements and transmission electron microscope observation revealed that the as-prepared mesoporous α-Fe2O3 nanostructures have large mesopores in a wide size range of 5−30 nm. It has been found that the Morin transition depends on thermal history of mesoporous α-Fe2O3, which is driven by surface anisotropy. Superparamagnetic behavior of mesoporous α-Fe2O3 is also associated with surface spins with blocking temperature around 50 K. When applied as gas sensors, mesoporous α-Fe2O3 nanostructures exhibited high gas sensitivity toward acetic acid and ethanol gas. As anodes in lithium ion cells, mesoporous α-Fe2O3 materials show a high specific capacity of 1360 mAh/g with excellent cycling stability and high rate capacity.

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TL;DR: In this article, a review of recent developments in porous Si anodes, such as mesoporous nanowires, 3D porous particles, and nanotubes have been highlighted.
Abstract: Si anode materials for lithium rechargeable batteries have received much attention due to their high capacity. The Si itself can alloy with lithium up to Li4.4Si, corresponding to 4212 mAh/g (4.4Li + Si ↔ Li4.4Si). However, the large volume expansion of over 300% due to the formation of various LixSiy phases generates enormous mechanical stress within the ionic character material, which becomes pulverized during the first few cycles and loses electrical integrity. Although such a drastic volume change cannot be removed completely, the degree of the volume change can be effectively reduced to utilize its application in anode materials. In this regard, when porous particles contain ordered pores, these pores act as a buffer layer for volume changes, demonstrating another means of controlling the volume expansion/contraction. In this review, recent developments in porous Si anodes, such as mesoporous nanowires, 3D porous particles, and nanotubes have been highlighted.