Synthesis of Pt-containing ordered mesoporous carbons and their catalysis for toluene hydrogenation

Highly ordered Pt-containing mesoporous carbons (Pt-OMCs) have been synthesized by a multi-component co-assembly method followed by pyrolysis at high temperature. In this synthesis, resorcinol, formaldehyde and chloroplatinic acid were used as the carbon and Pt precursors. The triblock copolymer Pluronic F127 was used as the template. X-ray diffraction, N₂-adsorption measurements and transmission electron microscopy revealed that the Pt nanoparticles in about 1–3 nm were embedded in the highly ordered mesostructure carbon. The Pt3.1-OMC was used as the catalyst in the hydrogenation of toluene. By comparing with the traditional impregnated 3.3Pt/OMC catalyst to our catalyst, Pt3.1-OMC, the sample exhibited a much higher selectivity to methylcyclohexane.     

A novel activated carbon for supercapacitors

A novel activated carbon has been prepared by simple carbonization and activation of phenol–melamine–formaldehyde resin which is synthesized by the condensation polymerization method. The morphology, thermal stability, surface area, elemental composition and surface chemical composition of samples have been investigated by scanning electron microscope, thermogravimetry and differential thermal analysis, Brunauer–Emmett–Teller measurement, elemental analysis and X-ray photoelectron spectroscopy, respectively. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L^?1 potassium hydroxide. The activated carbon shows good capacitive behavior and the specific capacitance is up to 210 F g^?1, which indicates that it may be a promising candidate for supercapacitors.     

Blending effect of sucrose and surfactant templating agents on silica mesostructure

We report the blending effect of surfactant and sucrose as a nonsurfactant templating agent on the silica mesostructure. The CTAB/sucrose-templated mesoporous silica (SCS) was compared with CTAB-templated MCM-41. The MCM-41 showed spherical morphology with a particle diameter of 1.1–1.5 μm, and gave a bimodal size distribution, centered at 2.1 nm and 8.9 nm, which is assigned to hexagonally-arrayed cylindrical pores and interparticle-pores between small MCM-41 clusters, respectively. SCS gave unique and extraordinary morphology in which two different mesostructures have grown with both of them facing each other. The ordered MCM-41 pore structure clung to silica nanosphere-framed wormlike mesostructure, resulting in a bimodal pore size distribution centered at 2.1 nm and 7.0 nm. It was revealed that both of CTAB and sucrose act independently as a surfactant and a nonsurfactant template.     

Non-hydrothermal synthesis of mesoporous materials using sodium silicate from coal fly ash

Siliceous mesoporous materials with pores of ordered 2-D hexagonal structure were successfully prepared without hydrothermal treatment from condensation–polymerization of various concentration of quaternary ammonium salt as structure directing agents and silica precursor from the supernatant of coal fly ash (CFA) in the presence of catalyst. The synthesized materials had high surface area of ca. 740 m² g⁻¹ and pore volume of ca. 0.42 mL g⁻¹. The synthesized material exhibited a narrow size pore distribution and the mean pore diameter as measured by Dollimore–Heal method was about 2.3 nm. The formation of ammonium salt that act as precipitant during the synthesis enable the hydrolysis and co-condensation of the sodium silicate at room temperature.     

Selective adsorption and release of cationic organic dye molecules on mesoporous borosilicates

Mesoporous materials can play a pivotal role as a host material for delivery application to a specific part of a system. In this work we explore the selective adsorption and release of cationic organic dye molecules such as safranine T (ST) and malachite green (MG) on mesoporous borosilicate materials. The mesoporous silica SBA-15 and borosilicate materials (MBS) were prepared using non-ionic surfactant Pluronic P123 as template via evaporation induced self-assembly (EISA) method. After template removal the materials show high surface areas and in some cases ordered mesopores of dimensions ca. 6–7 nm. High surface area, mesoporosity and the presence of heteroatom (boron) help this mesoporous borosilicate material to adsorb high amount of cationic dye molecules at its surface from the respective aqueous solutions. Furthermore, the mesoporous borosilicate samples containing higher percentage adsorbed dyes show excellent release of ST or MG dye in simulated body fluid (SBF) solution at physiological pH = 7.4 and temperature 310 K. The adsorption and release efficiency of mesoporous borosilicate samples are compared with reference boron-free mesoporous pure silica material to understand the nature of adsorbate–adsorbent interaction at the surfaces.     

有序中孔炭球的自组装合成及其结构控制

以间苯二酚糠醛低聚物为炭前驱体,三嵌段共聚物F127为结构导向剂,通过悬浮辅助的蒸发诱导自组装乳化成球,高温炭化后得到有序中孔炭球. 考察了乳化剂用量和搅拌速度对有序中孔炭球的粒径和表面形貌影响,嵌段共聚物F127与间苯二酚摩尔比（F127/R）及间苯二酚糠醛反应时间对有序中孔炭球的微观结构影响. 结果表明：当乳化剂用量从0.1vol%增加到2.0vol%,有序中孔炭球的粒径从400μm减小到100μm;在乳化剂用量相同时,搅拌速度从100r/min增加到600r/min, 有序中孔炭球的粒径从341μm减小到60μm;当 F127/R的比值为0.008、0.015和0.025时,分别制得三维体心立方、二维六方和无序蠕虫结构的中孔炭球.     

Synthesis,characterization and magnetic performance of Co-incorporated ordered mesoporous carbons

Co-incorporated ordered mesoporous carbon (Co-OMC) with magnetic frameworks has been synthesized via a one-pot self-assembly strategy. The effects of cobalt loading on carbon matrix, adsorption properties and magnetic properties of the resultant mesostructured cobalt/carbon composites were investigated by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and magnetometer measurements. The results show that the mesoporous composites with a high cobalt content (such as 18.0 wt%) possess an ordered and uniform mesoporous structure (5.3 nm), high surface areas (up to 687 m²/g) and high pore volumes (up to 0.54 cm³/g). Cobalt nanoparticles of size 4–9 nm are confined inside the mesopores or walls of the mesoporous carbon. These materials exhibit typical ferromagnetic characteristics. The saturation magnetization strength can be easily adjusted by changing the content of cobalt. The carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMC also.     

Rapid synthesis of ordered hexagonal mesoporous silica and their incorporation with Ag nanoparticles by solution plasma

Rapid synthesis of silica with ordered hexagonal mesopore arrangement was obtained using solution plasma process (SPP) by discharging the mixture of P123 triblock copolymer/TEOS in acid solution. SPP, moreover, was utilized for Ag nanoparticles (AgNPs) incorporation in silica framework as one-batch process using silver nitrate (AgNO₃) solution as precursor. The turbid silicate gel was clearly observed after discharge for 1 min and the white precipitate formed at 3 min. The mesopore with hexagonal arrangement and AgNPs were observed in mesoporous silica. Two regions of X-ray diffraction patterns (2θ < 2° and 2θ = 35–90°) corresponded to the mesoporous silica and Ag nanocrystal characteristics. Comparing with mesoporous silica prepared by a conventional sol–gel route, surface area and pore diameter of mesoporous silica prepared by solution plasma were observed to be larger. In addition, the increase in Ag loading resulted in the decrease in surface area with insignificant variation in the pore diameter of mesoporous silica. SPP could be successfully utilized not only to enhance gelation time but also to increase surface area and pore diameter of mesoporous silica.     

Highly ordered mesoporous bioactive glasses with Im3m symmetry

Highly 3D body centered cubic (Im3m) ordered mesoporous bioactive glasses (MBG) were synthesized by evaporation-induced self-assembly (EISA) in the presence of a nonionic triblock copolymer, EO₁₀₀PO₆₅EO₁₀₀ (F127), template. The influence of the F127 concentration on the mesostructure was examined. MBG calcined at 600 °C possessed a large specific surface area (∼ 520 m² g^− 1) and pore volume (0.51 cm³ g^− 1) and a uniformly distributed pore size (5.4 nm). In vitro bioactivity studies were carried out in simulated body fluid (SBF).     

Application of low-voltage electrophoretic deposition to fabrication of direct methanol fuel cell electrode composite catalyst layer

In this study, the application of a low-voltage electrophoretic deposition (EPD) approach to the fabrication of DMFC electrode composite (i.e., catalyst/ionomer) catalyst layers using a CNT-supported PtRu (PtRu/CNT) anode nanocatalyst was investigated. In the operation of EPD, the PtRu/CNT electrocatalyst was first well mixed with a suitable amount of Nafion^® solution (ionomer dispersion) with or without the addition of HClO₄ as a supporting electrolyte and then electrophoretically deposited onto a non-catalyzed electrode base at a low applied DC voltage range of 0–5 V for 0–60 min. The resultant composite catalyst layer appeared to be thin and quite smooth exhibiting a lustrous texture particularly when the supporting electrolyte was employed in the suspension. Electrochemical impedance spectroscopy (EIS), however, showed that the coated composite catalyst layer exhibited a fairly high resistance indicating an excessive amount of ionomer was preferably deposited. Application of the fabricated electrode to a DMFC resulted in a cell performance with low but reasonable power density. These test results suggested that the low-voltage EPD could be a feasible approach to effective fabrication of DMFC electrode composite catalyst layers incorporated with CNT-supported electrocatalysts, although significant improvements are deemed to be necessary.     

Preparation of carbon aerogel microspheres by a simple-injection emulsification method

Carbon aerogel microspheres were successfully prepared using a simple-injection emulsification method, employing sol–gel polycondensation of a resorcinol–formaldehyde solution containing sodium carbonate as a catalyst. This process was followed by solvent exchange using acetone, supercritical drying with carbon dioxide and carbonization in a nitrogen atmosphere. The effect of curing time before starting injection, injection rate and agitation rate of continuous phase on the particle size and the porous properties of the carbon aerogel microspheres was investigated. Adsorption of phenol by using the prepared carbon aerogel microspheres was also examined. The diameter of carbon aerogel microspheres was controlled in the range of 20–55 μm by varying injection rate and agitation rate. The mean diameter of carbon aerogel microspheres decreased with increasing the injection rate and the agitation rate, whereas their mean diameter was independent of the curing time. The BET surface area and total pore volume of carbon aerogel microspheres increased with increasing the curing time. In contrast, their BET surface area and total pore volume decreased with increasing the injection rate and the agitation rate. The BET surface area, total pore volume, mesopore volume and micropore volume of the carbon aerogel microspheres with a mean diameter of 45 μm were 903 m²/g, 0.60 cm³/g, 0.31 cm³/g and 0.27 cm³/g, respectively. The phenol-adsorption capacity of these carbon aerogel microspheres was 29.3 mg phenol/g adsorbent.     

Mesoporous carbon spheres with uniformly penetrating channels and their use as a supercapacitor electrode material

An optimized nanostructure design for electrode materials of supercapacitors was realized by introducing furfuryl alcohol into as-prepared surfactant-containing spherical host and generating a robust mesoporous structure. The structural characterization shows that the carbon spheres inherit the regular mesopore structure and high surface area of the template and possess a uniform particle size containing well-ordered channels throughout the spheres. By adjusting the initial molar ratio of H₂O to tetraethyl orthosilicate (TEOS), the pore volumes of the templated carbons vary from 0.4 to 0.6 cm³·g^-1 and surface areas are in the range of 610 and 944 m²·g^-1. Furthermore, NiO nanoparticles were incorporated into the carbon spheres by air oxidation of the Ni-containing samples. The use of these spheres in electrode materials for electric double layer capacitors was investigated. The electrochemical measurements show that the specific capacitance of the ordered mesoporous carbon spheres (OMCs-2) can increase by 40% to 205.3 F·g^-1 by the addition of 3 wt% NiO.     

CdS nanoparticles incorporated onion-like mesoporous silica films: Ageing-induced large stokes shifted intense PL emission

CdS nanoparticles (NPs) were generated in onion-like ordered mesoporous SiO₂ films through a modified sol–gel process using P123 as a structure directing agent. Initially Cd²⁺ doped (12 equivalent mol% with respect to the SiO₂) mesoporous SiO₂ films were prepared on glass substrate. These films after heat-treatment at 350 °C in air yielded transparent mesoporous SiO₂ films having hexagonally ordered onion-like pore channels embedded with uniformly dispersed CdO NPs. The generated CdO NPs were transformed into CdS NPs after exposing the films in H₂S gas at 200 °C for 2 h. The as-prepared CdS NPs incorporated mesoporous SiO₂ films (transparent and bright yellow in color) showed a band-edge emission at 485 nm and a weak surface defect related emission at 530 nm. During ageing of the films in ambient condition the band-edge emission gradually weakened with time and almost disappeared after about 15 days with concomitant increase of defect related strong surface state emission band near 615 nm. This transformation was related to the decay of initially formed well crystalline CdS to relatively smaller and weakly crystalline CdS NPs with surface defects due to gradual oxidation of surface sulfide. At this condition the embedded CdS NPs show large Stokes shifted (∼180 nm) intense broad emission which could be useful for luminescent solar concentrators. The detailed process was monitored by UV–Visible, FTIR and Raman spectroscopy, XPS, XRD and TEM studies. The evolution of photoluminescence (PL) and life times of CdS/SiO₂ films were monitored with respect to the ageing time.     

Corrosion resistance of directionally solidified Al–6Cu–1Si and Al–8Cu–3Si alloys castings

The aim of this article is to compare the electrochemical corrosion resistance of two as-cast Al–6 wt.% Cu–1 wt.% Si and Al–8 wt.% Cu–3 wt.% Si alloys considering both the solutes macrosegregation profiles and the scale of the microstructure dendritic arrays. A water-cooled unidirectional solidification system was used to obtain the as-cast samples. Electrochemical impedance spectroscopy (EIS) and potentiodynamic anodic polarization techniques were used to analyze the corrosion resistance in a 0.5 M NaCl solution at 25 °C. It was found that the Al–8Cu–3Si alloy has better electrochemical corrosion resistance than the Al–6Cu–1Si alloy for any position along the casting length. At the castings regions where the Cu inverse profile prevailed (up to about 10 mm from the castings surface) the corrosion current density decreased up to 2.5 times with the decrease in the secondary dendrite arm spacing.     

Application of graphene–pyrenebutyric acid nanocomposite as probe oligonucleotide immobilization platform in a DNA biosensor

A stable and uniform organic–inorganic nanocomposite that consists of graphene (GR) and pyrenebutyric acid (PBA) was obtained by ultrasonication, which was characterized by scanning electron microscopy (SEM) and UV–vis absorption spectra. The dispersion was dropped onto a gold electrode surface to obtain GR–PBA modified electrode (GR–PBA/Au). Electrochemical behaviors of the modified electrode were characterized by cyclic voltammetry and electrochemical impedance spectroscopy using [Fe(CN)₆]^3 ?/4 ? as the electroactive probe. A novel DNA biosensor was constructed based on the covalent coupling of amino modified oligonucleotides with the carboxylic group on PBA. By using methylene blue (MB) as a redox-active hybridization indicator, the biosensor was applied to electrochemically detect the complementary sequence, and the results suggested that the peak currents of MB showed a good linear relationship with the logarithm values of target DNA concentrations in the range from 1.0 × 10^? 15 to 5.0 × 10^? 12 M with a detection limit of 3.8 × 10^? 16 M. The selectivity experiment also showed that the biosensor can well distinguish the target DNA from the non-complementary sequences.     

Development of amperometric laccase biosensor through immobilizing enzyme in copper-containing ordered mesoporous carbon (Cu-OMC)/chitosan matrix

A functionalized copper-containing ordered mesoporous carbon (Cu-OMC) which shows good electrical properties was synthesized by carbonization of sucrose in the presence of cupric acetate inside SBA-15 mesoporous silica template. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the Cu-OMC/chitosan (CS) film was developed. Laccase from Trametes versicolor was assembled on a composite film of Cu-OMC/chitosan (CS) modified Au electrode and the electrode was characterized. The optimum experimental conditions of biosensor for the detection of catechol were studied in details. Under the optimal conditions, the detection limit was 0.67 μM and the linear detection range was from 0.67 μM to 15.75 μM for catechol. The apparent Michaelis–Menten (K_M^app) was estimated using the Lineweaver–Burk equation and the K_M^app value was 40.2 μM. This work demonstrated that the Cu-OMC/CS composite provides a suitable support for laccase immobilization and construction of biosensor.     

Preparation of organic and carbon xerogels using high-temperature–pressure sol–gel polymerization

To prepare organic gels at temperatures higher than normal boiling point of solvent, a method was developed using sol–gel polymerization in atmosphere saturated by vapor of solvent. To illustrate the advantages of proposed method, two series of gels were prepared using the conventional (T_curing = 70 °C) and the high temperature (T_curing = 140–170 °C) sol–gel polymerization. While no drying shrinkage was observed in our proposed method, 5–18% linear shrinkage occurred in conventional method depending on resin concentration in sol. Moreover, rising of curing temperature reduced the required time for preparation of organic gels from 5 days to lower than 5 h. The effects of processing parameters were investigated on physical and mechanical properties of organic xerogels. The results revealed that resin concentration significantly affects both density and compressive strength of final xerogels. While the curing temperature had no obvious effect on density, the raising of curing temperature significantly enhance the strength of organic xerogels. Carbon xerogels prepared by pyrolysis of novolac aerogels in inert atmosphere. The textures of the carbon xerogels were denser than corresponding organic xerogels, as evidenced by scanning electron microscopy (SEM) images. N₂ adsorption tests indicated that carbon aerogels were mainly meso or macroporous depending on resin concentration in initial sol.     

Growing polystyrene chains from the surface of graphene layers via RAFT polymerization and the influence on their thermal properties

The polystyrene (PS) macromolecular chains were grafted on the surface of graphene layers by reversible addition-fragmentation chain transfer (RAFT) polymerization. In this procedure, a RAFT agent, 4-Cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid, was used to functionalize the thermal reduced graphene oxide (TRGO) to obtain the precursor (TRGO-RAFT). It can be calculated that the grafting density of PS/graphene (PRG) composites was about 0.18 chains per 100 carbons. Successful in-plain attachment of RAFT agent to TRGO and PS chain to TRGO-RAFT was shown an influence on the thermal property of the PRG composites. The thermal conductivity (λ) improved from 0.150 W m⁻¹ K⁻¹ of neat PS to 0.250 W m⁻¹ K⁻¹ of PRG composites with 10 wt% graphene sheets loading. The thermal property of PRG composites increased due to the homogeneous dispersion and ordered arrangement of graphene sheets in PS matrix and the formation of PRG composites.     

Fabrication and characterization of a zirconia/multi-walled carbon nanotube mesoporous composite

A zirconia/multi-walled carbon nanotube (ZrO₂/MWCNT) mesoporous composite was fabricated via a simple method using a hydrothermal process with the aid of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy (TEM), N₂ adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the as-made samples. The cubic ZrO₂ nanocrystallites were observed to overlay the surface of MWCNTs, which resulted in the formation of a novel mesoporous–nanotube composite. On the basis of a TEM analysis of the products from controlled experiment, the role of the acid-treated MWCNTs and CTAB was proposed to explain the formation of the mesoporous–nanotube structure. The as-made composite possessed novel properties, such as a high surface area (312 m² · g^? 1) and a bimodal mesoporous structure (3.18 nm and 12.4 nm). It was concluded that this composite has important application value due to its one-dimensional hollow structure, excellent electric conductivity and large surface area.     

Enhanced microwave absorbing properties of carbonyl iron-doped Ag/ordered mesoporous carbon nanocomposites

Microwave absorbing materials carbonyl iron (CI)-doped Ag/ordered mesoporous carbon (OMC) paraffin wax composites were prepared by colloidal deposition and impregnation methods, and their electromagnetic and microwave absorbing properties were investigated in the frequency ranging from 2 to 18 GHz. The microstructures and chemical compositions of the Ag/OMC and Ag/OMC-CI paraffin wax composites were characterized by TEM, XRD, XPS, SEM and EDS, respectively. The complex permittivity of the paraffin wax composites show dual resonance behavior, resulting from the multi-interfaces among Ag nanoparticles, OMC nanorods, CI and paraffin wax. The magnetic loss was mainly caused by natural resonance and eddy current loss, respectively. The minimum reflection loss (RL) value of Ag/OMC-CI was below ?10 dB at 12 GHz, which were superior to those of OMC-CI and Ag/OMC. This phenomenon is attributed to the enhancement of dielectric polarization and magnetic loss.