Soft-template Route Research Articles

Investigation of radiofrequency induced release kinetics from magnetic hollow silica microspheres

Composite hollow silica microspheres containing embedded iron oxide nanoparticles for radiofrequency heating have been synthesised by a soft templating route. The influence of nanoparticle concentration on the microspheres size distribution, shell thickness, and heating rate was investigated. The structure of the hollow microspheres was characterised by SEM, confocal microscopy and BET analysis, and the temperature-dependence of release kinetics of a model substance (vitamin B12) from the microspheres was measured by time-resolved UV/Vis spectrophotometry. A mathematical model of the release process, based on simultaneous diffusion and adsorption/desorption of the solute in the mesoporous shell, has been developed and used to evaluate the dependence of the effective diffusivity in the mesoporous silica shell on temperature and preparation conditions.

Ordered mesoporous carbon nanoparticles with well-controlled morphologies from sphere to rod via a soft-template route

A facile soft-template method is used to synthesize highly ordered mesoporous carbon nanoparticles (MCNs) with well-controlled morphology from spherical to rod-like structures. Low-molecular-weight phenolic resol is used as carbon-yielding component and triblock copolymer Pluronic F127 as pore-forming component. The morphology of nanoparticles could be tuned by well controlling the concentration of F127. The results show that rod-shaped and worm-like mesoporous carbon nanoparticles can be obtained when the concentration of F127 is set at ∼12wt.% and 9wt.%, respectively. The spherical nanoparticles are obtained when the concentration is reduced to 6wt.%, and their size can be adjusted by further decreasing the F127 concentration. Moreover, the highly ordered mesostructure can be readily turned from 2D hexagonal (p6m) to 3D caged cubic (Im3¯m) along with the tuning of morphologies from rod-shaped to spherical. The as-obtained MCNs exhibit large surface area (∼1385m2/g), high pore volume (∼0.919cm3/g), highly ordered mesostructure, and continuous electron transport framework. Hence, the obtained mesoporous carbon materials show excellent capacitance (∼142F/g at loading current density of 0.5A/g) in the application of supercapacitors.

SYNTHESIS OF MESOPOROUS HYDROXYAPATITE THROUGH A SOFT TEMPLATE ROUTE USING NON-IONIC SURFACTANT

Conventional synthesis of mesoporous hydroxyapatite (HAp) commonly employs coprecipitation method using cationic surfactants such as CTAB. Such surfactants are expensive and create tinier mesopores without an interconnecting pore structure. Using non-ionic surfactants in the synthesis of mesoporous HAp, the pore formation could be induced to tailor desirable pore characteristics. This paper reports on synthesis of mesoporous HAp through soft template route using non-ionic surfactants P123, F127 and P123/F127. Calcination was carried out at 550 °C for 6 hours to reveal pores through the removal of the organic surfactant. The formation of HAp prior and subsequent to the calcination was evaluated through several materials characterization techniques. The X-ray diffraction (XRD) diffractograms revealed characteristic peaks of HAp corresponds to a typical HAp crystal phase, whereby a hexagonal lattice structure was deduced. SEM micrographs revealed rod-like HAp particles with diameter of approximately 24 nm and length ranging from 100 nm. TEM revealed the formation of nanopore channels within the rod-like structure, aligned in a lengthwise direction within the rods. The nanopore channels were consistent with the cavities being generated by the removal of non-ionic surfactant. The pores formed were found to be randomly distributed within the HAp structure.

High surface area mesoporous Co3O4 from a direct soft template route

Mesoporous Co3O4 with hexagonally ordered cylindrical channels has been synthesized by a single-step method using Pluronic soft micellar templates. The resulting material has been directly compared to isomorphous Co3O4 that was obtained via an established but laborious five-step nanocasting method. The soft template route employs only surfactant templates and a decane additive, which yields directly mesoporous Co3O4 by a gelling process in a carefully controlled basic (pH = 12.7) alcohol solution at 35 °C. The method is significantly faster and more economical than conventional nanocasting, and has similar overall reproducibility to the conventional multi-step route. The soft templated Co3O4 displays long-range ordered cylindrical microchannels with crystalline walls. Most importantly, it exhibits an unparalleled N2 BET surface area of 367 m2 g−1.

ChemInform Abstract: Ordered Mesoporous Non‐Oxide Materials

AbstractReview: 296 refs.

Synthesis of Ordered Mesoporous Carbon Loaded Fe, Co, Ni Nanocrystals by the Soft Templating Route and Their Characterization

报道了在有序介孔碳基体中一步合成负载Fe、Co、Ni纳米晶的方法．以间二苯酚和甲醛为碳源，F127为模板剂，Fe、Co、Ni的硝酸盐为前驱体，通过软模板组装路线在酸性条件下合成了负载型有序介孔碳复合材料．采用X射线衍射（XRD）、透射电镜（TEM）和氮气吸附等手段对所合成材料进行了表征．结果表明：合成的材料具有类似于SBA．15的有序介孔结构。有序介孔碳负载Fe、Co、Ni纳米晶复合材料的比表面积分别为586、626和698m2．g^-1．XRD和TEM表征结果证实了金属物种以高分散纳米晶的形式分布在介孔碳基体中．

Ordered mesoporous non-oxide materials

Ordered mesoporous inorganic non-oxide materials attract increasing interest due to their plenty of unique properties and functionalities and potential applications. Lots of achievements have been made on their synthesis and structural characterization, especially in the last five years. In this critical review, the ordered mesoporous non-oxide materials are categorized by compositions, including non-oxide ceramics, metal chalcogenides, metal nitrides, carbides and fluorides, and systematically summarized on the basis of their synthesis approaches and mechanisms, as well as properties. Two synthesis routes such as hard-templating (nanocasting) and soft-templating (surfactant assembly) routes are demonstrated. The principal issues in the nanocasting synthesis including the template composition and mesostructure, pore surface chemistry, precursor selection, processing and template removal are emphatically described. A great number of successful cases from the soft-templating method are focused on the surfactant liquid-crystal mesophases to synthesize mesostructured metal chalcogenide composites and the inorganic-block-organic copolymer self-assembly to obtain non-oxide ceramics (296 references).

Synthesis of highly ordered Fe-containing mesoporous carbon materials using soft templating routes

Highly ordered Fe-containing mesoporous carbon materials were directly synthesized through simple soft templating routes by using resorcinol–formaldehyde (RF) as a carbon precursor, triblock copolymer Pluronic F127 as a template agent and hydrated iron nitrite as an iron source. The main strategy of this approach is to use the acidity self-generated in the aqueous solutions of the iron precursors as the catalyst for RF polymerization and no any additional mineral acid was necessary. The resultant materials were characterized using nitrogen sorption, X-ray diffraction, and transmission electron microscopy. It was found that the final products with a highly ordered mesostructure were obtained when the Fe/R ratio was around 0.1. For those with Fe/R ratios smaller or greater than this value, the ordering decreased. Iron species in the mesoporous carbon matrix existed in two states, metallic Fe and γ-Fe2O3. Metallic Fe nanoparticles are dominantly buried in the walls of the mesoporous carbon while γ-Fe2O3 nanoparticles are mostly located on the surface. The resulting materials with Fe/R ratio of 0.1 (Fe/OMC-0.10) exhibit specific activity for the catalytic wet peroxide oxidation (CWPO) of phenol solution with hydrogen peroxide. The phenol and TOC conversion can reach to 93.0% and 61.7% within 180min at an initial of phenol 247ppm under very mild conditions (P=1atm and T=80°C).

Selective production of propylene from methanol: Mesoporosity development in high silica HZSM-5

The mesoporosity development in high silica HZSM-5 was carried out by alkaline desilication treatment and soft template method, and its relationship with the catalytic performance of the modified catalysts in methanol-to-propylene reaction was studied. High propylene selectivity (42.2%) and propylene/ethylene ratio (10.1) were observed on the high silica HZSM-5 catalyst modified by alkaline desilication. The enhanced catalytic performance can be attributed to the newly created open mesopores on the surface of the zeolite crystals together with the low Brønsted acidity. A greater amount of mesoporosity could be readily formed in HZSM-5 crystals via the soft template route. However, the mesopores formed in this method are randomly distributed in the zeolite crystals and play a minor role in the molecular transport of the reaction, so the improvement in propylene selectivity and propylene/ethylene ratio of the catalyst is less evident. The higher propylene selectivity and propylene/ethylene ratio on modified HZSM-5 (especially by alkaline treatment) than unmodified HZSM-5 could be also related to different contributions of the methylaromatics route and olefins methylation/cracking route in MTP reaction.

High dispersion platinum catalyst using mesoporous carbon support for fuel cells

Porous carbon with high surface area and pore volume can allow fine dispersion of metal nano-particles. Mesoporous carbon (MC) with high surface area was synthesized using soft colloidal template route. Pt/C catalysts with different platinum loadings were prepared from home-made MC and chloroplatinic acid solution using wet impregnation. The particle size calculated from TEM analysis showed the Pt particle size of 2.7, 3.4 and 3.6 nm for 20, 40 and 80 wt.% Pt/MC catalysts, respectively. The Pt particles on the porous carbon support were found to be in uniform shape and narrow range of particle size. The dispersion feature of MC-supported Pt catalysts was also compared with that of a home-made Pt catalyst supported on commercial Vulcan carbon. CO stripping and CV analysis of MC-supported Pt catalysts showed higher mass activity for electrochemical reactions under fuel cell conditions.

Micrometre-sized In2S3 half-shells by a new dynamic soft template route: properties and applications

A novel dynamic soft template solution route has been developed for the preparation of micrometre-sizedIn2S3 half-shells, assembled by fine nanoparticles. This novel half-shell nanostructure wascharacterized by electron microscopes, x-ray diffraction (XRD), x-ray photoelectron (XPS),and optical spectroscopes. The catalytic property in the electro-oxidation of the nitric oxide(NO) of the half-shells was also investigated, which could be drastically enhanced by theloading of Ag nanoparticles. Finally, the template-free, one-pot method describedhere is likely to be useful in the preparation of many other half-shell structures.

Preparation and characterization of shuttle-like α-Fe 2O 3 nanoparticles by supermolecular template

Shuttle-like α-Fe 2O 3 nanoparticles have been successfully synthesized via a new soft-template route using polyethylene glycol (PEG) as polymer, cetyltrimethylammonium bromide (CTAB) as surfactant and FeCl 3·6H 2O as iron source materials. Meanwhile, spherical α-Fe 2O 3 nanoparticles are also fabricated under the similar conditions without surfactant and polymer. The resultant products are characterized by means of thermalgravimetric analysis (TGA), powder X-ray diffraction (XRD), infrared (IR) spectroscopy, transmission electron micrograph (TEM), X-ray photoelectron spectra (XPS) and magnetization measurements. The homogeneous α-Fe 2O 3 nanoparticles with shuttle-like shape have an average length of 120 nm and a mean diameter of about 50 nm in the middle part (an average aspect ratio of about 2.5) whereas spherical α-Fe 2O 3 nanoparticles have a mean particle diameter of about 35 nm. Magnetic hysteresis measurements reveal that shuttle-like α-Fe 2O 3 nanoparticles display normal ferromagnetic behaviors while spherical α-Fe 2O 3 nanoparticles exhibit weak ferromagnetic behaviors at room temperature. The two types of α-Fe 2O 3 exhibit hysteretic features with the remanence and coercivity of 0.156 emu/g and 664 Oe, 0.048 emu/g and 110 Oe, respectively. The higher remanent magnetization and coercivity of shuttle-like α-Fe 2O 3 nanoparticles may be associated with the aspect ratio of α-Fe 2O 3 since shape anisotropy would exert a tremendous influence on their magnetic properties.

Mesoporous Carbons with Controlled Porosity as an Electrocatalytic Support for Methanol Oxidation

Mesoporous carbons with high surface area, large pore diameter, and enhanced mesoporosity have been synthesized by a soft colloidal template route with various aniline/cetyltrimethylammonium bromide (CTABr) ratios and investigated as an electrocatalytic support for methanol oxidation by cyclic voltammetry. The mesoporous carbons loaded with Pt catalysts exhibit two to three times higher mass activity (mA/mg Pt) for methanol oxidation than Vulcan XC 72R carbon loaded with Pt. The enhanced activity is attributed to a better dispersion and utilization of the catalysts, originating from a combination of high surface area and lower percentage of undesirable micropores. Both cyclic voltammetric and chronoamperametric measurements of the Pt-loaded carbon samples indicate that the mesoporous carbon possesses lower hydrophilicity compared to the conventional Vulcan XC 72R carbon. However, the hydrophilicity is found to depend on the aniline/CTABr ratios used during the synthesis of the mesoporous carbon samples.

Mesoporous Carbon with Larger Pore Diameter as an Electrocatalyst Support for Methanol Oxidation

Mesoporous carbons with high surface area, large pore diameter, and enhanced mesoporosity have been synthesized by a novel soft colloidal template route and investigated as an electrocatalyst support for methanol oxidation. The mesoporous carbon has been characterized by nitrogen adsorption measurements, transmission electron microscopy, and cyclic voltammetry. The mesoporous carbons loaded with Pt catalysts exhibit three times higher mass activity (mA/mg Pt) for methanol oxidation than Vulcan XC 72R loaded with Pt. The enhanced activity of the mesoporous carbon is attributed to a better dispersion and utilization of the catalysts, originating from a combination of high surface area and absence of undesirable micropores.