Dual template approach for the synthesis of hierarchically mesocellular carbon foams

We demonstrated a simple and effective dual-templating approach for the synthesis of hierarchically mesocellular carbon foams by using nonionic surfactant of sorbitan monooleate and silica colloid particles as sacrificial templates, and resorcinol/ formaldehyde as carbon source. The representative carbon foam has dual mesopore sizes of 4 and 10 nm, and possesses the specific surface area of 580 m2/g and the total pore volume of 0.80 cm3/g.     

Preparation of ordered mesoporous SiC from preceramic polymer templated by nanoporous silica

Highly ordered mesoporous SiC materials were prepared by infiltrating viscous liquid preceramic polymer, allylhydridopolycarbosilane, into two types of surface modified nanoporous silica templates: mesoporous silica SBA-15 and mesocellular siliceous foam. The silica templates were subsequently etched off after pyrolysis at 1000 degrees C under nitrogen atmosphere with the resultant formation of ordered mesoporous structures. The mesoporous SiC materials, synthesized from both types of templates possessed high Brunauer-Emmett-Teller (BET) surface areas in the range of 250-260 m(2)/g with pore sizes of 3.4-3.6 nm. The ordered structures of mesoporous SiC were exact inverse replicas of their respective silica templates, as characterized by small angle X-ray diffraction (XRD), transmission electron microscope (TEM) images, and the adsorption-desorption isotherm of nitrogen.     

Efficient enrichment and desalting of protein digests using magnetic mesocellular carbon foams in matrix-assisted laser desorption/ionization mass spectrometry

We demonstrate that magnetic mesocellular carbon foams (Mag-MCF-C) can be effectively used for enrichment and desalting of protein digests or peptides in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The large mesocellular pores and surface area of Mag-MCF-C are likely to mainly contribute to high efficiency in enrichment and desalting of protein digests. The magnetic property of Mag-MCF-C enabled easy and simple enrichment and desalting process comprising adsorption, washing, and separation steps by using an external magnet. Following elution from Mag-MCF-C by using a matrix solution (CHCA in 70% ACN/0.1% TFA), the peptides were subjected to MALDI-MS analysis. As a result, MALDI mass spectra of peptides or tryptic protein digests were distinct even at a peptide concentration as low as 50 pM. The use of Mag-MCF-C resulted in significantly improved sequence coverage for protein identification when compared to other conventional methods. Mag-MCF-C will find applications in mass spectrometric analysis of low abundance peptides or protein digests with high sensitivity.     

Synthesis of micron-sized hollow silica spheres with a novel mesoporous shell of MCF

Micron-sized hollow silica spheres whose shells are made up of mesocellular silica foams(MCFs) have been synthesized by one-pot sol-gel method in benzene/water/P123 emulsion.The material is characterized with SEM,TEM,BET and ~(29)Si MAS NMR. The results show that the MCFs of the unique shell of hollow silica spheres were connected by large windows with a narrow distribution of～10 nm in diameter,the inner space of the hollow sphere is accessible.And the formation mechanism of the hollow silica spheres is ...     

Nano-graphite functionalized mesocellular carbon foam with enhanced intra-penetrating electrical percolation networks for high performance electrochemical energy storage electrode materials

Mesocellular carbon foam (MSU-F-C) is functionalized with hollow nanographite by a simple solution-phase method to enhance the intrapenetrating electrical percolation network. The electrical conductivity of the resulting material, denoted as MSU-F-C-G, is increased by a factor of 20.5 compared with the pristine MSU-F-C. Hollow graphite nanoparticles are well-dispersed in mesocellular carbon foam, as confirmed by transmission electron microscopy (TEM), and the d spacing of the (002) planes is 0.343 nm, which is only slightly larger than that of pure graphite (0.335 nm), suggesting a random combination of graphitic and turbostratic stacking. After nanographitic functionalization, the BET surface area and total pore volume decreased from 928 m(2) g(-1) and 1.5 cm(3) g(-1) to 394 m(2) g(-1) and 0.7 cm(3) g(-1), respectively. Thermogravimetric analysis in air shows that the thermal stability of MSU-F-C-G is improved relative to that of MSU-F-C, and the one-step weight loss indicates that the nanographite is homogeneously functionalized on the MSU-F-C particles. When the resulting mesocellular carbon materials are used as electrode materials for an electric double layer capacitor (EDLC), the specific capacitances (C(sp)) of the MSU-F-C and MSU-F-C-G electrodes at 4 mV s(-1) are 109 F g(-1) and 93 F g(-1), respectively. The MSU-F-C-G electrode exhibited a very high area capacitance (C(area), 23.5 μF cm(-2)) compared with that of the MSU-F-C electrode (11.7 μF cm(-2)), which is attributed to the enhanced intraparticle conductivity by the nanographitic functionalization. MSU-F-C-G exhibited high capacity retention (52%) at a very high scan rate of 512 mV s(-1), while only a 23% capacity retention at 512 mV s(-1) was observed in the case of the MSU-F-C electrode. When applied as an anode in a lithium ion battery, a significant increase in the initial efficiency (44%), high reversible discharge capacity (580 mA h g(-1)) in the lower voltage region, and a higher rate capability were observed. The high rate capability of the MSU-F-C-G electrode as charge storage was due to the low resistance derived from the nanographitic functionalization.     

Macro-cellular silica foams: synthesis during the natural creaming process of an oil-in-water emulsion

The room-temperature synthesis of a macro-mesoporous silica material during the natural creaming process of an oil-in-water emulsion is reported. The material has 3-dimensional interconnected macropores with a strut-like structure similar to meso-cellular silica foams with mesoporous walls of worm-hole structure. The material has very high surface area (approximately 800 m2 g(-1)) with narrow mesopore size distribution.     

Bundling and diameter selectivity in HiPco SWNTs poly(p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene) composites

Temperature-dependent (TD) Raman measurements at laser excitation 514.5 nm were performed at different concentrations. The spectral profile of the radial breathing modes were investigated up to a polymer concentration of 1 g/L and were found to be dominated by approximately 1.2-1.4 nm diameter tubes at room temperature. Upon heating above the glass transition of the polymer (60 degrees C) the smaller tubes around approximately 0.9 nm increased significantly in relative intensity. This suggests that below the glass transition of the polymer (60 degrees C) RBMs within the composite are damped and spectral changes cannot be interpreted as diameter selective solubilization. The observed RBM damping at room temperature only occurred up to a concentration of approximately 1.2 x 10(-4) g/L and below this no damping was observed. Photoluminescence intensity (PL) measurements were taken for a range of PmPV concentrations, in which HiPco single walled carbon nanotubes (SWNTs) at 100%, 10%, 1%, 0.1%, 0.01%, and 0% mass fractions were added. Fitting of the concentration dependence to a dynamic absorption/desorption model indicates that the polymer interacts with nanotube bundles until a critical concentration of approximately 1.2 x 10(-4) g/L is reached, below which the nanotubes are isolated. The polymer and or solvent has a significant effect on the debundling and aggregation within these systems. Aggregation and/or interaction with the polymer at higher concentrations can effect the RBM profile in the composite at ambient temperatures, providing an incomplete representation of the selection of diameters present within composites at a particular wavelength.     

A novel magnetically separable laccase-mediator catalyst system for the aerobic oxidation of alcohols and 2-substituted-2,3-dihydroquinazolin-4(1H)-ones under mild conditions

In this study, a magnetically reusable artificial metalloenzyme has been constructed by co-immobilization of palladium nanoparticles as a strong oxidizing catalyst and laccase as an oxygen-activating enzyme into the cavities of magnetic mesocellular foams silica (Pd-Laccase@MMCF). The combination of Pd-Laccase@MMCF and hydroquinone (HQ) act as electron-transfer mediator system and make stepwise electron transfer from substrate to molecular oxygen. This catalyst system was used for the aerobic (i) oxidation of alcohols to the corresponding carbonyl compounds and (ii) dehydrogenation of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in phosphate buffer (0.1 M, pH 4.5, 4 mL)/THF (4%, 1 mL) as solvent under mild conditions. The co-immobilization of both laccase and Pd onto high surface area mesoporous support, high catalytic activity and magnetically separable and reusable make the present catalyst system superior to other currently available electron-transfer mediator systems.     

Mesoporous Nanofibers from Dual Structure‐Directing Agents in AAO: Mesostructural Control and their Catalytic Applications

Control yourself! The mesoporous silica nanofibers (MSNFs) from dual structure‐directing agents were fabricated inside the pores of porous alumina (AAO, see figure) by using vapor phase synthesis. The pore structures could be controlled to form a range of structures from mesocellular foams to cylindrical mesopores with long‐range order by adding cationic cosurfactants.

     

Studies of Hg2+ adsorption and desorption by mesocellular foams silica

MCFs (mesocellular foams) silica, a mesoporous material, was synthesized by the hydrothermal method using tri-block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic P123, EO₂₀-PO₂₀-EO₂₀) as a structuring agent and 1, 3, 5-trimethylbenzene as a pore-expanding agent and the product was characterized by powder X-ray diffraction and scanning electron microscopy. The prepared MCFs was employed as the adsorbent for a study of the adsorption of Hg²⁺. The adsorptive experimental results showed that the optimal adsorptive conditions were: pH = 5.0, MCFs amount 0.10 g, temperature 20°C, and adsorption time 40 min, when the initial concentration of Hg²⁺ is 1.0 mg mL^?1. The maximum adsorptive amount of Hg²⁺ was 124.5 mg Hg²⁺ g^?1 MCFs. The desorption studies found that the best desorbing agent is 0.10 M hydrochloric acid. The highest desorption rate of 80.61 % could be reached at a desorption duration of 3 h. The cost of the adsorbent used in this study is lower than that of activated carbon with a higher value of application.     

Immobilization of Pd Catalysts on Mesoporous Silica for Amine- and Copper-Free Sonogashira Coupling Reactions

Immobilization of catalysts on solid supports is a promising approach to combine the advantages of heterogeneous and homogeneous catalysts. Pd(PPh₃)₂Cl₂, known as an extremely active homogeneous catalyst for the Sonogashira coupling reaction, has been immobilized on high-surface-area MCF (mesocellular foams)–type mesoporous silica powder modified with 3-aminopropyltriethoxysilane and subsequently with diphenylphosphine. The functionalized MCF-type silica and supported catalysts have been characterized by x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), elemental analysis, nitrogen sorption porosimetry, and scanning electron microscopy (SEM). Such supported Pd catalysts have proven to be useful recyclable reagents for copper- and amine-free Sonogashira coupling reactions of haloaromatic compounds with terminal alkynes.     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Heterogeneous CaO(SrO,BaO)/MCF as highly active and recyclable catalysts for the glycolysis of poly(ethylene terephthalate)

Research on Chemical Intermediates - A new group of basic species, CaO(SrO and BaO), supported on mesocellular siliceous foam (MCF) has been prepared and used for catalyzing glycolysis of...     

Ultralow-density nanostructured metal foams: combustion synthesis, morphology, and composition

The synthesis of low-density, nanoporous materials has been an active area of study in chemistry and materials science dating back to the initial synthesis of aerogels. These materials, however, are most often limited to metal oxides, e.g., silica and alumina, and organic aerogels, e.g., resorcinol/formaldehyde, or carbon aerogels, produced from the pyrolysis of organic aerogels. The ability to form monolithic metallic nanocellular porous materials is difficult and sometimes elusive using conventional methodology. Here we report a relatively simple method to access unprecedented ultralow-density, nanostructured, monolithic, transition-metal foams, utilizing self-propagating combustion synthesis of novel transition-metal complexes containing high nitrogen energetic ligands. During the investigation of the decomposition behavior of the high-nitrogen transition metal complexes, it was discovered that nanostructured metal monolithic foams were formed in a post flame-front dynamic assembly having remarkably low densities down to 0.011 g cm(-3) and extremely high surface areas as high as 270 m(2) g(-1). We have produced monolithic nanoporous metal foams via this method of iron, cobalt, copper, and silver metals. We expect to be able to apply this to many other metals and to be able to tailor the resulting structure significantly.     

Polymer‐Derived Silicoboron Carbonitride Foams for CO2 Capture: From Design to Application as Scaffolds for the in Situ Growth of Metal–Organic Frameworks

A template‐assisted polymer‐derived ceramic route is investigated for preparing a series of silicoboron carbonitride (Si/B/C/N) foams with a hierarchical pore size distribution and tailorable interconnected porosity. A boron‐modified polycarbosilazane was selected to impregnate monolithic silica and carbonaceous templates and form after pyrolysis and template removal Si/B/C/N foams. By changing the hard template nature and controlling the quantity of polymer to be impregnated, controlled micropore/macropore distributions with mesoscopic cell windows are generated. Specific surface areas from 29 to 239 m² g^?1 and porosities from 51 to 77 % are achieved. These foams combine a low density with a thermal insulation and a relatively good thermostructural stability. Their particular structure allowed the in situ growth of metal–organic frameworks (MOFs) directly within the open‐cell structure. MOFs offered a microporosity feature to the resulting Si/B/C/N@MOF composite foams that allowed increasing the specific surface area to provide CO₂ uptake of 2.2 %.     

Effect of cationic polymers on foam rheological properties

We study the effect of two cationic polymers, with trade names Jaguar C13s and Merquat 100, on the rheological properties of foams stabilized with a mixture of anionic and zwitterionic surfactants (sodium lauryloxyethylene sulfate and cocoamidopropyl betaine). A series of five cosurfactants are used to compare the effect of these polymers on foaming systems with high and low surface dilatational moduli. The experiments revealed that the addition of Jaguar to the foaming solutions leads to (1) a significant increase of the foam yield stress for all systems studied, (2) the presence of consecutive maximum and minimum in the stress vs shear rate rheological curve for foams stabilized by cosurfactants with a high surface modulus (these systems cannot be described by the Herschel-Bulkley model anymore), and (3) the presence of significant foam-wall yield stress for all foaming solutions. These effects are explained with the formation of polymer bridges between the neighboring bubbles in slowly sheared foams (for inside foam friction) and between the bubbles and the confining solid wall (for foam-wall friction). Upon addition of 150 mM NaCl, the effect of Jaguar disappears. The addition of Merquat does not noticeably affect any of the foam rheological properties studied. Optical observations of foam films, formed from all these systems, show a very good correlation between the polymer bridging of the foam film surfaces and the strong polymer effect on the foam rheological properties. The obtained results demonstrate that the bubble-bubble attraction can be used for efficient control of the foam yield stress and foam-wall yield stress, without significantly affecting the viscous friction in sheared foams.     

A 1H magnetic resonance imaging study of porosity in polyurethane foams

¹H magnetic resonance imaging (MRI) is used to study the distribution of water in polyurethane foams. Flexible open-celled foams are easily distinguished from the closed-cell foams as the latter does not absorb any detectable amounts of water. Flexible foams degassed in vacuo revealed no structural detail due to the resolution limitation of approximately 100 μm. Incompletely degassed foams revealed considerable areas of trapped gas which were recorded as a function of distance beneath the water. Samples injected with water indicated that a tortuous flow pathway is taken due to the presence of cell windows. Samples with lower porosity had a higher resistance to flow.     

Polymer Foams Stabilized by Particles Adsorbed at the Air/Polymer Interface

In aqueous systems, partially hydrophobic particles are known to stabilize foams even in the absence of any added surfactant. This paper shows that the same principle can be applied to polymeric systems: particles that are partially wetted by a polymer melt can stabilize a foam of that polymer. The foam stability is attributable to the adsorption of the particles at the air/polymer interface. Remarkably, stable foams are realized even from polymers that are liquid at room temperature, and hence are otherwise unfoamable. The implications of this result to practical foaming operations are discussed.

     

Simultaneous anion and cation exchange chromatography of whey proteins using a customizable mixed matrix membrane

Membrane chromatography can overcome some of the limitations of packed bed column chromatography but preparation of adsorptive membranes usually involves complex and harsh chemical modifications. Mixed matrix membranes (MMMs) require only the physical incorporation of an ion exchange resin into the membrane polymer solution prior to membrane casting. An advantage of MMMs not previously exploited is that resins with differing adsorptive functionalities can be conveniently embedded within a single membrane at any desired ratio. This presents the opportunity to customize an adsorptive membrane to suit the expected protein profile of a raw feed stream e.g. bovine whey or serum. In this work, a novel mixed mode interaction MMM customized to extract all major proteins from bovine whey was synthesized in a single membrane by incorporating 42.5 wt% Lewatit MP500 anionic resin and 7.5 wt% SP Sepharose cationic resin into an ethylene vinyl alcohol base polymer casting solution. The mixed mode MMM developed was able to bind both basic and acidic proteins simultaneously from whey, with binding capacities of 7.16±2.24 mg α-lactalbumin g(-1) membrane, 11.40±0.73 mg lactoferrin (LF)g(-1) membrane, 59.21±9.90 mg β-lactoglobulin g(-1) membrane and 6.79±1.11 mg immunoglobulin Gg(-1) membrane (85 mg total protein g(-1) membrane) during batch fractionation of LF-spiked whey. A 1000 m(2) spiral-wound membrane module (200 L membrane volume, 1m(3) module volume) is predicted to be able to produce approximately 25 kg total whey protein per h.     

Ceramic Foams from a Preceramic Polymer and Polyurethanes: Preparation and Morphological Investigations

Open-cell ceramic foams were obtained from a preceramic polymer (silicone resin) and blown polyurethanes. The preceramic polymer, which is crosslinked by condensation of silanol groups, was dissolved in CH2Cl2 and added to a liquid polyol containing the surfactant and the amine catalyst. Isocyanate was then added to the mixture and the foam was obtained through a twofold blowing mechanism (physical and chemical blowing). The morphology of the expanded polyurethane, which can be flexible or semirigid, characterized the final structure of the ceramic foam. The materials obtained were pyrolyzed in a nitrogen flux at temperatures of 1000–1200°C, thus allowing for the polymer-to-ceramic transformation to occur in the preceramic polymer. The ceramic foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC). They presented a density ranging from 0.1 to 0.3 g/cm3. The average pore diameter ranged from 200 to 400 m and they possessed 80 to 90% open porosity.