Ordered Pore Channels Research Articles

One-pot synthesis of silicon nanoparticles trapped in ordered mesoporous carbon for use as an anode material in lithium-ion batteries

Silicon nanoparticles trapped in an ordered mesoporous carbon composite were prepared by a one-step self-assembly with solvent evaporation using the triblock copolymer Pluronic F127 and a resorcinol–formaldehyde polymer as the templating agent and carbon precursor respectively. Such a one-pot synthesis of Si/ordered mesoporous carbon nanocomposite is suitable for large-scale synthesis. Characterization confirmed that the Si nanoparticles were trapped in the ordered mesoporous carbon, as evidenced by transmission electron microscopy, x-ray diffraction analysis and nitrogen sorption isotherms. The composite showed a high reversible capacity above 700 mA h g−1 during 50 cycles at 2 A g−1. The improved electrochemical performance of the composite can be ascribed to the buffering effect of spaces formed in the ordered pore channels during the volume expansion of silicon and the rapid movement of lithium ions through the uniform cylindrical pore structure of the mesopores.

Template synthesis of nanoparticle arrays of gold using highly ordered functional mesoporous silica thin films with high amino-groups content

The periodic disposed gold nanoparticle arrays (GNPAs) are very useful for wide range applications. Employing the neutralization reaction between chloroauric acid and amino groups, GNPAs were self-assembled inside pore channels of amino-functionalized mesoporous silica thin films (AF-MSTFs) which were produced by using the surface active agent CTAB (cetyltrimethyl ammonium bromide). The AF-MSTF samples were characterized by FTIR, XRD and TEM. The results show that the average diameter of quantum dots was controlled by the highly ordered pore channels. UV–vis absorption spectra of the GNPAs/AF-MSTF nanocomposites exhibit blue-shift and intensity decrease of absorption peaks as the neutralization reaction time decreases, representing the existence of GNPs and revealing an adjustable optical property.

A simplified synthesis of N-doped zeolite-templated carbons, the control of the level of zeolite-like ordering and its effect on hydrogen storage properties

Nitrogen-doped, microporous carbon materials have been prepared using zeolite EMC-2 as a hard template and acetonitrile as the carbon source via chemical vapour deposition (CVD) in the temperature range 700–950 °C. The carbon products exhibited high surface areas (up to 3360 m 2/g), high pore volumes (up to 1.71 cm 3/g) and had zeolite-like structural ordering derived from the template. The carbons had XRD patterns that exhibited two well resolved peaks and TEM images that showed well ordered pore channels. A high proportion of porosity (up to 85% of surface area and 73% of pore volume) for the best ordered carbon arose from micropores that exhibited narrow size distribution in the range 5–15 Å. The carbons generally retained the morphology of the template with solid-core particles at CVD temperatures up to 900 °C and hollow shells at 950 °C. The carbons had total hydrogen storage capacities up to 6.0 wt.% at −196 °C and 20 bar. The hydrogen uptake was found to be dependent on the level of zeolite-like ordering and the resulting textural properties. Particularly, high levels of zeolite-like ordering favoured micropores of size <15 Å which are favourable for higher hydrogen uptake capacities.

Influence of Pore Structure on Catalytic Properties of Mesoporous Silica‐supported Co‐B Amorphous Alloys in Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

AbstractCo‐B amorphous alloy catalysts supported on three kinds of mesoporous silica (common SiO2, MCM‐41 and SBA‐15) have been systematically studied focusing on the effect of pore structure on the catalytic properties in liquid‐phase hydrogenation of cinnamaldehyde to cinnamyl alcohol (CMO). Structural characterization of a series of different catalysts was performed by means of N2 adsorption, X‐ray diffraction, transmission electron microscopy, hydrogen chemisorption, and X‐ray photoelectron spectroscopy. Various characterizations revealed that the pore structure of supports profoundly influenced the particle size, location and dispersion degree of Co‐B amorphous alloys. Co‐B/SBA‐15 was found more active and selective to CMO than either Co‐B/SiO2 or Co‐B/MCM‐41. The superior catalytic activity could be attributed to the higher active surface area, because most of Co‐B nanoparticles in Co‐B/SBA‐15 were located in the ordered pore channels of SBA‐15 rather than on the external surface as found in Co‐B/SiO2 and Co‐B/MCM‐41. Meanwhile, the geometrical confinement effect of the ordered mesoporous structure of SBA‐15 was considered to be responsible for the enhanced selectivity to CMO on Co‐B/SBA‐15, inhibiting the further hydrogenation of CMO to hydrocinnamyl alcohol.

Fabrication and carbon monoxide sensing characteristics of mesostructured carbon gas sensors

We demonstrated a micro-chemoresistive gas sensing device using mesoporous carbon as the sensitive film and immobilized by dielectrophoresis (DEP) process. The mesoporous materials were characterized by X-ray diffraction (XRD) patterns, N 2 adsorption–desorption isotherms, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). N 2 adsorption–desorption isotherms shows the specific surface area of 1200 m 2/g, total pore volume is 1.2 cm 3/g of the mesoporous carbon, and the pore size distribution of mesoporous carbon yields an average pore size of 3 nm. SEM images show a rod-like morphology and TEM images show a highly ordered pore channel with linear arrays. CO gas sensor properties were measured and the resulting sensitivities were 5.7, 6.8, 8.8, 11.6, and 37.6% for concentrations of 30, 45, 60, 75, and 90 ppm, respectively. Additionally, this sensor also exhibited high sensitivity and fast response times for CO gas.

Morphology and dispersivity modulation of hollow microporous spheres synthesized by a hard template route

Uniform hollow microporous silica spheres (HMS) have been synthesized in an easy route using polystyrene spheres (PS) and cetyltrimethylammonium bromide (CTAB) as co-templates at room temperature in concentrated aqueous ammonia. The hexagonally ordered pore channels are formed on the shell of the HMS. Effects of various processing parameters such as the tetraethyl orthosilicate (TEOS) adding rate, the amount of aqueous ammonia and ultrasonic treatment, on the dispersivity and morphology, were investigated. The slow syringing addition of TEOS favors the formation of highly dispersed hollow spheres with a certain and uniform shell thickness. More aqueous ammonia and proper time of ultrasonic are helpful to the synthesis of uniform hollow silica spheres with good dispersivity. The morphology, dispersivity and micropore structure of as-synthesized HMS were characterized using X-ray diffraction, N 2 sorption isotherms, scanning electron microscope and transmission electron microscope.

Monodispersed nanoporous starburst carbon spheres and their three-dimensionally ordered arrays

Controlled syntheses of highly monodispersed nanoporous carbon spheres via a nanocasting route are described. Previously reported monodispersed super-microporous or mesoporous silica spheres with hexagonally ordered pore channels were used as sacrificial templates, and the effect of pore sizes of the templates on the porous properties of the nanocast carbon spheres was comprehensively studied. The resultant carbon spheres exhibited a unique starburst structure derived from radially-aligned pore channels in the silica template, and had a BET surface area of over 1000 m 2g −1. It was found out that the radial alignment and sufficiently large pore size of hexagonally ordered pore channels in the silica spheres were effective to enhance the degree of order of the starburst structure in the nanocast carbon spheres and that ordered nanoporous carbon spheres could be obtained even from the MCM-41-type mesoporous silica. The diameters of the nanoporous carbon spheres were controlled in the sub-micrometer range by changing the sizes of silica templates. Furthermore, three-dimensionally ordered arrays consisting of nanoporous carbon spheres were successfully fabricated via the self-assembly of mesoporous silica/carbon composite spheres and the subsequent dissolution of the silica templates.

Proton-Conducting Mesoporous Silica/Phosphate Composite Films Prepared by Vapor Phase Method

Mesoporous silica/phosphate composite films were synthesized from a vapor phase onto a Si substrate. Field emission scanning emission microscope and X-ray diffraction measurements show that the resultant films have ordered pore channels with a hexagonal arrangement parallel to the film surface. The proton conductivity for the mesoporous silica/phosphate composite films was 0.07-0.38 S cm -1 . The proton conductivity was not affected much by water vapor pressure. The activation energy for the proton conduction was low (13 kJ mol -1 ). The high P-OH group content and the ordered periodic mesostructure contributed to the high proton conductivity.

Synthesis of hydrothermally stable aluminium-containing ethane-silica hybrid mesoporous materials using different aluminium sources

Aluminium-containing ethane-silica hybrid mesoporous materials having ethane groups in the frame wall positions are synthesized using aluminium isopropoxide as well as aluminium nitrate as the aluminium sources. The materials were characterized in detail using powder XRD, N 2 adsorption–desorption, SEM, TEM, TG-DTG, TPD, 29Si, 13C and 27Al MAS NMR techniques. Characterization techniques revealed that aluminium isopropoxide was the appropriate source for the synthesis of organo aluminosilicas on considering the structural ordering, acidity as well as the percentage of aluminium incorporation into the ethane bridge. 27Al MAS NMR displays aluminium as tetrahedrally coordinated in both the aluminium-containing organosilicas. Unlike the conventional EtOH–HCl template extraction process, in the present studies, we had used EtOH–NH 4OH as the surfactant-extracting medium and chemical analysis results suggest that using this procedure the extent of dealumination can be greatly reduced. XRD and nitrogen physisorption studies further proved that the materials are hydrothermally stable, that the ordered pore channels retains its structure even after 150 h reflux in boiling water, while the conventional Al-MCM-41 catalyst collapsed its mesostructure after 50 h reflux in water. The improved hydrothermal stability of the hybrid materials, even in presence of sodium ions, is attributed to the thick pore walls as well as due to the presence of hydrophobic bridging ethane groups in the wall positions.

Preparation of novel hollow mesoporous silica spheres and their sustained-releaseproperty

Novel hollow mesoporous silica spheres (HMSs) with uniform size and morphology havebeen successfully synthesized in a facile route using poly(vinylpyrrolidone) (PVP) andcetyltrimethylammonium bromide (CTAB) as co-templates at room temperature. XRD,N2 adsorption–desorption analysis, FE-SEM, and TEM are used for the characterization of thestructure. The hexagonally ordered pore channels are formed on the shell. Ibuprofen (IBU)as a model drug is used to examine the storage capacity and the release behaviour of drugmolecules. The storage capacity of hollow mesoporous silica spheres can reach1133 ± 52.4 mg g−1 foribuprofen, which is three times higher than that of conventional mesoporous materials previously reported(337 mg g−1), and the storage capacity is adjustable in a wide range. Furthermore, this system alsoshows a sustained-release behaviour. The release rates from the IBU-HMSs system (IBUstored in HMSs) increase with the decrease of pH values and the release process follows aFick’s law.

A facile method to synthesize novel hollow mesoporous silica spheres and advanced storage property

Hollow mesoporous silica spheres with uniform size and morphology have been successfully synthesized in a facile route using PVP and CTAB as co-templates at room temperature. XRD, N 2 adsorption–desorption analysis, FE-SEM, TEM and UV–vis are used for the characterization. The hexagonally ordered pore channels are formed on the shell. These hollow mesoporous silica spheres have been proven to store much more guest molecules than conventional MCM-41, with more than half of them being held in the hollow cores.

Confinement of Cd3P2 nanoparticles inside ordered pore channels in mesoporous silica

Nano-sized Cd3P2 has been confined inside the pore channels of MCM-41 by a surface modification method. XRD, TEM, N2 adsorption/desorption, UV-vis absorption and photoluminescence (PL) spectroscopy, elemental analysis and XPS techniques were used to characterize the Cd3P2/MCM-41 composites. Cd3P2 nanoclusters were mostly confined and dispersed in the channels of mesoporous hosts. Their growth was clearly restrained by the channels and their size was estimated to be around 1.5 nm. Massive blue-shifts in the UV-vis absorption and room temperature PL spectra from Cd3P2 nanoclusters were observed. The results of fluorescence decay time measurement show that the nature of the photoluminescence of Cd3P2/MCM-41 can be mainly attributed to intrinsic radiation of Cd3P2 nanoparticles.

High density hexagonal nickel nanowire array

Nickel nanowires were grown in highly ordered pore channels of an alumina membrane using pulsed electrodeposition. A complete metal filling of the hexagonal arranged pores with a pitch of 100 nm and a monodisperse pore diameter of ≈30 nm was obtained. The bulk-magnetic behavior of the ferromagnetic nanowire arrays was characterized by SQUID-magnetometer measurements. Magnetic-force-microscopy investigation measurements with a variable external magnetic field were applied on magnetized and demagnetized samples. In addition, magnetic wires have been locally switched by a strong MFM tip and an external magnetic field. The MFM results show a good agreement with the bulk magnetic hysteresis loop.