微孔-介孔高比表面积佛手渣基活性炭的制备

在催化和吸附分离等领域,微孔-介孔结构活性炭有广阔的应用前景。以废弃的佛手渣为原料,运用氢氧化钾活化法制备微孔-介孔高比表面积活性炭。考察了炭化和活化等工艺条件对活性炭结构的影响。结果表明,较佳工艺条件下制备的活性炭碘值为1544mg·g-1,BET比表面积1676m2·g-1,微孔BET比表面积350m2·g-1,孔径集中分布在2～5nm之间。     

Fabrication of silica membranes with controlled pore structure

Alkaline leaching of porous glasses is shown to involve three consecutive steps: removal of secondary silica from the pores, disruption of the surface (boron-enriched) layer of the channel walls, and etching of the silica skeleton of the porous glass. The effect of the alkaline leaching time on the porosity and effective pore radius in the glasses depends significantly on the heat-treatment temperature of the parent sodium borosilicate glass, which enables control over the pore structure of membranes produced from such glasses. Original Russian Text ? M.V. Lyubavin, T.M. Burkat, V.N. Pak, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 2, pp. 248–252.     

Palladium infiltration in high surface area microporous silica nanoparticles

Metallic Pd clusters were embedded into a host matrix of microporous SiO₂ nanoparticles via a solution reduction of Pd(NO₃)₂ by hydrazine hydrate. The infiltration of 33 wt.% Pd leads to a 13% porosity loss of SiO₂ nanoparticles, which demonstrated an initial surface area of 748 m²/g. The presence of Pd in the pores was demonstrated by EDS spectroscopy and by X-ray diffraction. The metallic guest species presumably reside in the accessible micropores with an estimated size about 1.3 nm. Hydrogen uptake was measured for Pd-infiltrated SiO₂ nanoparticles. A possible mechanism for the formation of composite nanoparticles is proposed based on electrostatic interaction between Pd²⁺ and SiO₂ nanoparticles.     

Organic-inorganic hybrid silica monolith based immobilized trypsin reactor with high enzymatic activity

A novel kind of immobilized trypsin reactor based on organic-inorganic hybrid silica monoliths has been developed. With the presence of cetyltrimethyl ammonium bromide (CTAB) in the polymerization mixture, the hybrid silica monolithic support was prepared in a 100 microm i.d. capillary by the sol-gel method with tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. Subsequently, the monolith was activated by glutaraldehyde, and trypsin was covalently immobilized. By monitoring the reaction of a decapeptide, C-myc (EQKLISEEDL), the enzymatic activity of the immobilized trypsin was calculated, and the results showed that the digestion speed was about 6600 times faster than that performed in free solution. The performance of such a microreactor was further demonstrated by digesting myoglobin, with the digested products analyzed by microflow reversed-phase liquid chromatography coupled with tandem mass spectrometry (microRPLC-MS/MS). With a stringent threshold for the unambiguous identification of the digests, the yielding sequence coverage for on-column digestion was 92%, the same as that obtained by in-solution digestion, whereas the residence time of myoglobin in the former case was only 30 s, about 1/1440 of that performed in the latter case (12 h). Moreover, such an immobilized trypsin reactor was also successfully applied to the digestion of a mixture of model proteins and proteins extracted from E. coli.     

结构有序、双重孔隙中孔炭材料的合成与表征

采用纳米涂层技术,以介孔分子筛SBA 15为模板,在其纳米孔道内引入糠醇/草酸溶液,经原位聚合,炭化后制得炭/SBA 15复合物。采用化学法脱除模板后制得具有规则结构的中孔炭。高分辨TEM表征结果显示该中孔炭是由纳米炭管相互联接、堆积而成,且具有六方对称结构。氮吸附结果显示其比表面积高达2000m2/g,孔径呈双峰分布。孔径相对较大的孔隙来源于SBA 15孔道经纳米涂层后所保留的孔隙;孔径相对较小的孔隙来源于SiO2移除后遗留的纳米孔空间。该方法可应用于以其他多孔氧化硅为模板制备新型纳米复合物的研究过程。     

Stimulated osteoblastic proliferation by mesoporous silica xerogel with high specific surface area

Specific surface area is a critical parameter of mesoporous silica-based biomaterials, however, little is known about its effects on osteoblast responses in vitro. In the present study, mesoporous silica xerogels (MSXs) with different surface area (401, 647 and 810 m²/g, respectively) were synthesized by a sol–gel process. Surface silanol contents decreased with the increase of surface area with which protein adsorption capability positively correlated. And the apatite-like surface seemed to form faster on MSXs with higher surface area determined by XRD analysis. Using MG63 osteoblast-like cells as models, it was found that cell proliferations were promoted on MSXs with higher surface area, based on the premise that the effects of Si released from materials on osteoblast viability were excluded by real-time Transwell^? assay. RT-PCR results indicated cell adhesion-related integrin subunits α5 were up-regulated by higher surface area at day 1, which was further confirmed by flow cytometry analysis. The data suggest that increasing SSA of MSXs could promote surface cellular affinity by adsorbing serum proteins and accelerating apatite-like layer formation, which results in promoted osteoblastic proliferation via integrin subunit α5 at initial adhesion stage. Regulating SSA, an effective approach in designing mesoporous silica-based materials, provides an alternative method to obtain desirable tissue-response in bone regeneration and drug-delivery system.     

Fiber template approach toward preparing one-dimensional silica nanostructure with rough surface

Silica nanofibers were grown on the surface of chitosan nanofibers used as templates by coating the surface with silica derived from the hydrolysis and condensation of tetraethoxysilane using ammonium hydroxide as a catalyst. This was followed by the decomposition of the chitosan template. The relationship between different processing factors (type of templates as well as amounts of catalyst and template) and the formation of silica nanofibers was examined. Varying the processing factors was found to be effective in controlling the morphology of the silica nanofibers. The use of chitosan nanofibers effectively led to the formation of one-dimensional silica nanofibers as the positively charged chitosan nanofibers promoted the deposition of the negatively charged silica nanoparticles through electrostatic attractive forces. Therefore, the chitosan nanofibers acted as good deposition sites for interacting with silica nanoparticles. Although a large amount of catalyst promoted the sol-gel reaction, the silica nanoparticles grew excessively in the solvent. Therefore, the surface structure of the prepared silica nanofibers could be controlled by varying the amount of chitosan template as this also varied the formation mechanism of the silica nanofibers. The resultant samples had a rough silica wall composed of densely assembled silica nanoparticles, with a high specific surface area (338 m²/g).     

Grafting fluorescence molecules into the pore surface of bimodal mesoporous silicas with different routes

Novel luminescent hybrid silicas have been synthesized through one-step and two-step methods and their different luminescent properties have been investigated. The results showed that the samples synthesized with two-step procedure exhibited a more evident blue shift of photoluminescence performance resulting from the high efficiency of surface amine than that by one-step route. The structure characteristic and texture properties of resultant hybrid silicas were characterized by XRD, TEM, FT-IR and N₂ adsorption-desorption techniques, indicating that inorganic/organic nanocomposites could maintain the bimodal mesoporous structure. Finally, a possible involved mechanism has been put forward.     

Increasing surface area of silica nanoparticles with a rough surface

The silica nanoparticles with a rough surface were developed using a silane precursor in a reverse microemulsion followed by a drying treatment. The surface roughness of the nanoparticles was adjustable by changing the amount of the precursor. Within a certain range, the roughness increased as the amount of the silane precursor increased. The rough surface provided a larger surface area than the smooth one. The produced nanoparticles were characterized using the transmission electron microscopy, ultraviolet-visible spectroscopy, energy-dispersive X-ray elemental analysis, and Brunauer-Emmet-Teller analysis technique. Additionally, the amount of surface functional amino groups on the nanoparticles was detected using the traditional acid-base titration and the dissociation constant of this functional group was calculated. On the basis of the experimental results, the mechanism of the formation of the rough surface was proposed. Finally, the produced silica nanoparticles were utilized as a carrier for the chemical binding of a near-infrared dye molecule and the adsorption of the gold nanoparticles. The results demonstrated that the rough surface provide the silica nanoparticles with a high capacity of surface chemical and supramolecular reactions.     

A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure

Anionic surfactants are used in greater volume than any other surfactants because of their highly potent detergency and low cost of manufacture. However, they have not been used as templates for synthesizing mesoporous silica. Here we show a templating route for preparing mesoporous silicas based on self-assembly of anionic surfactants and inorganic precursors. We use aminosilane or quaternized aminosilane as co-structure-directing agent (CSDA), which is different from previous pathways. The alkoxysilane site of CSDA is co-condensed with inorganic precursors; the ammonium site of CSDA, attached to silicon atoms incorporated into the wall, electrostatically interacts with the anionic surfactants to produce well-ordered anionic-surfactant-templated mesoporous silicas (AMS). These have new structures with periodic modulations as well as two-dimensional hexagonal and lamellar phases. The periodic modulations may be caused by the coexistence of micelles that differ in size or curvature, possibly owing to local chirality. These mesoporous silicas provide a new family of mesoporous materials as well as shedding light on the structural behaviour of anionic surfactants.     

Short-period synthesis of high specific surface area silica from rice husk char

Porous silica with high specific surface areas is prepared from rice husk char within a short period by avoiding the commonly used hydrothermal treatment step and using polyethylene glycol (PEG, molecular weight = 20,000) as a template. The preparation process mainly involves sodium silicate production, precipitation with ortho-phosphoric acid, and calcination. The amount of used PEG significantly affects the silica textural properties like the specific surface area, total pore volume and mesopore volume. The reason should be attributed to the amount of PEG removed from the PEG-silica composites by calcination. By varying the PEG dosage from 100 to 176 mg, porous silica with specific surface areas ranging from 709 to 936 m²/g could be successfully prepared within 10 h.     

Continuous laser irradiation under ambient conditions: A simple way for the space-selective growth of gold nanoparticles inside a silica monolith

Thanks to the potential and various applications of metal-dielectric nanocomposites, their syntheses constitute an interesting subject in material research. In this work, we demonstrate the achievement of gold nanocrystals growth through a visible and continuous laser irradiation. The in situ and direct space-selective generation of metallic nanoparticles is localized under the surface within transparent silica monoliths. For that purpose, the porous silica monoliths are prepared using a sol-gel route and post-doped with gold precursors before the irradiation. The presence of Au nanoparticles inside the irradiated areas was evidenced using absorption spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The comparison between the results obtained after a laser irradiation and by a simple heat-treatment reveals that the local precipitation of gold nanoparticles by continuous photo-irradiation occurs following a photo-thermal activated mechanism.     

Preparation and characterization of high surface area nanosheet titania with mesoporous structure

High surface area nanosheet TiO₂ with mesoporous structure were synthesized by hydrothermal method at 130 °C for 12 h. The samples were characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50–100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO₂ had an average pore diameter about 3–4 nm. The BET surface area and pore volume of the sample are about 642 m²/g and 0.774 cm³/g, respectively.     

石墨纤维的比表面积与孔隙结构的测定与分析

为了定量地描述和分析石墨纤维的比表面积和孔隙结构,采用低温氮吸附法测定石墨纤维在液氮温度和不同压力条件下的氮气吸附-脱附等温曲线.研究表明石墨纤维属于微孔材料,含有大量的微孔和极少量的介孔;石墨纤维的BET比表面积、总孔体积和平均孔径分别为541.00m2/g、0.2436cm3/g、1.8010nm,其微孔的比表面积...     

Fe3O4纳米粒子作为催化剂和致孔剂制备高比表面积块体石墨化炭

报道了一种以Fe3O4纳米晶粒为催化剂和致孔剂制备具有高比表面积块体石墨化炭的方法.首先采用共沉淀法合成粒径＜10nm的Fe3O4纳米颗粒,然后将其均匀分散到以2,4-二羟基苯甲酸(D)、甲醛(F)为原料,无水Na2 CO3为催化剂形成的聚合物(DF)中,通过溶胶-凝胶过程和炭化过程得到掺杂Fe的石墨化炭.最后经过酸洗,得到纯的高比表面积块体石墨化炭.随炭化温度的升高(700℃～900℃),样品的石墨化程度增加.在800℃炭化,样品已具有明显的石墨化结构,且比表面积较大.     

Bending strength of silica gel with bimodal pores: Effect of variation in mesopore structure

Silica gels with both macropores and mesopores were prepared from water glass by fixing transitional structure of phase separation, and their strength was investigated. Pore structure of the gels was controlled by changing gel-preparation compositions, aging conditions and calcination temperature. Strength of the gels varies depending on the mesopore volume. At the same time, porosity of the gels decreases with decreasing mesopore volume, and correlation between strength and porosity is recognized like other porous systems. The strength of the bimodal porous silica gel is somewhat larger than that in literature for the silica aerogel with similar porosity.     

Synthesis of high surface area mesoporous carbonates in novel ionic liquid

High surface area mesoporous SrCO₃, CaCO₃ and MnCO₃ with straw-like bundles morphology were synthesized in a novel imidazolium pyruvate ionic liquid. These carbonates were characterized by X-ray diffraction, Fourier transform infrared spectra and transmission electron microscopy. The results revealed that these carbonates have pure orthorhombic and rhombohedral structures, respectively, and the prepared products all show the unique straw-like morphology. Mesoporous properties and high surface areas of SrCO₃(118 m²/g), CaCO₃(43 m²/g) and MnCO₃ (122 m²/g) were also confirmed by the corresponding N₂ sorption analyses.     

Hollow silica nanoparticles: A tiny pore with big dreams

Hollow nanoparticles exhibit unique functions such as thermal insulation, low dielectricity, and abnormal light scattering, especially when the inner size reaches less than twice the mean free path of air molecules (mean free path of air is 68 nm). It is easy to imagine that a nano-sized pore improves the thermal insulation performance due to less air convection flow inside. However, not only the hollow interior but also the shell microstructure (size, thickness, and density) strongly affect the functionalities. For example, a lower apparent shell density induces a higher thermal insulation probably due to phonon scattering on the siloxane bond cleavages. The best performance for the thermal conductivity of the hollow particle/polymer composite was 0.019 W/m·K, which is superior to air. The structure design of the hollow nanoparticle is quite important to produce this effect. In this review, based on important parameters, how to design the structure and wide applications of hollow nanoparticles are reviewed and a bright outlook for the future is expected.     

An emulsion method for producing fine,low density,high surface area silica powder from alkoxides

Fine silica powders were prepared by the hydrolysis and condensation of an emulsion of tetraethyl orthosilicate (TEOS) droplets in a continuous water phase. No additions of alcohol, as a mutual solvent for the TEOS and water, or of strong acid or base catalysts, as required in the more conventional sol-gel methods, were used. The emulsion was produced by mechanical mixing and was stabilized against separating out of the phases by increasing the viscosity of the water with a commercial thickening agent, Texipol.The TEOS/water emulsion reacted to form into a loose particulate gel, which could be crushed to a powder after drying at 40 °C. The amorphous silica powders produced had low tapping densities (approximately 0.2 g cm^–3), small particle sizes (<30 nm) and high specific surface areas (50–400 m²g^–1).