One-pot synthesis of ordered mesoporous carbon–silica nanocomposites templated by mixed amphiphilic block copolymers

Mixed amphiphilic block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) and polydimethylsiloxane-poly(ethylene oxide) (PDMS–PEO) have been successfully used as co-templates to prepare ordered mesoporous polymer–silica and carbon–silica nanocomposites by using phenolic resol polymer as a carbon precursor via the strategy of evaporation-induced self-assembly (EISA). The ordered mesoporous materials of 2-D hexagonal (p6m) mesostructures have been achieved, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen-sorption measurements. Experiments show that using PDMS–PEO as co-template can enlarge the pore sizes and reduce the framework shrinkage of the materials without evident effect on the specific surface areas. Ordered mesoporous carbons can then be obtained with large pore sizes of 6.7 nm, pore volumes of 0.52 cm³/g, and high surface areas of 578 m²/g. The mixed micelles formed between the hydrophobic PDMS groups and the PPO chains of the F127 molecules should be responsible for the variation of the pore sizes of the resulting mesoporous materials. Through the study of characteristics of mesoporous carbon and mesoporous silica derived from mother carbon–silica nanocomposites, we think mesoporous carbon–silica nanocomposites with the silica-coating mesostructure can be formed after the pyrolysis of the PDMS–PEO diblock copolymer during surfactant removal process. Such method can be thought as the combination of surfactant removal and silica incorporation into one-step. This simple one-pot route provides a pathway for large-scale convenient synthesis of ordered mesostructured nanocomposite materials.     

偕胺肟基螯合氧化硅的合成及其Cu2+亲和性能

以氯化钾为晶体结构导向剂, 以正硅酸乙酯和2-氰乙基三乙氧基硅烷为硅源, 聚(乙二醇)-聚(丙二醇)-聚(乙二醇)三嵌段共聚物为模板剂, 合成了偕胺肟基螯合氧化硅(AO-SBA-15)。通过X射线衍射(XRD)、低温氮气吸附-脱附、傅里叶红外光谱(FT-IR)、Zeta电位分析和元素分析技术对样品的结构、孔性质和螯合官能团等进行了表征。XRD分析结果表明, 偕胺肟基螯合氧化硅材料具有有序的二维六方结构, 通过氮气物理吸附数据计算得到材料的平均孔径和比表面积分别为3.96 nm和435 m²/g。FT-IR分析表明将氰基成功地引入材料中并转化为偕胺肟基螯合官能团, 元素分析发现材料的偕胺肟基含量约为1.6 mmol/g, 此外, Zeta电位分析表明材料呈现电负性。相对未改性的氧化硅材料(SBA-15), AO-SBA-15对铜离子吸附容量提高了2倍; 相对氰基功能化氧化硅(CN-SBA-15), AO-SBA-15吸附容量提高了3.6倍。这表明通过引入偕胺肟基螯合官能团, SBA-15对铜离子的亲和力得到显著提高。     

Cultivation of human fibroblasts and multipotent mesenchymal stromal cells on mesoporous silica and mixed metal oxide films

The application of mesoporous silica and silica–titania-mixed metal oxide films prepared via sol–gel processing as substrates for cell growth was investigated. A deliberate tailoring of the chemical composition of the porous substrates with different Si:Ti ratios was achieved by using a single-source precursor based on a titanium-coordinated alkoxysilane, resulting in mesoporous silica–titania films with hydrophilic surfaces. The different coatings were investigated with respect to their applicability in the cultivation of human cells such as human fibroblasts and multipotent mesenchymal stromal cells. It was found that they promoted cell adhesion and proliferation of human fibroblasts up to a period of 14 days. After 2 weeks only single apoptotic cells could be detected on silica–titania mixed oxide films in contrast to a somewhat higher amount on silica coatings. Furthermore, none of the films inhibited osteogenic differentiation of multipotent mesenchymal stromal cells.     

Synthesis of 3-dimensional mesoporous silica using a di-block copolymer template

Exploring polymeric surfactants as templates for synthesizing ordered mesoporous silicas has become increasingly important for both academic interests and industrial applications. In this work, we employed C₁₆EO₄₀, a di-block copolymer polyethylene-poly(ethylene oxide), as template in an attempt to synthesize a modified 3-dimensional wormhole mesoporous silicas (WMS-39). In addition, various synthesizing conditions were investigated, including pre-hydrolysis time of TEOS, reaction temperatures and the ratios of TEOS to template. The products were characterized using powder XRD, TEM, ²⁹Si MAS NMR and nitrogen adsorption measurements. The characteristics of as-synthesized mesoporous silica were compared with SBA-15, a highly ordered mesoporous silica, prepared using non-ionic tri-block copolymers of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) as templates. The WMS-39 materials have a BET surface area of 600–970 m²/g and narrowly distributed pore diameter around 3.9 nm. The morphology of WMS-39 was found to be wormhole framework as indicated in TEM diagrams. Thermal transformation of the as-synthesized mesoporous materials were carefully analyzed with TGA/DTA. Findings obtained from this work enable us to propose a modified assembly mechanism of mesoporous silicas.     

Elucidation of interactive effects of synthesis conditions on the characteristics of mesoporous silicas templated using polyoxide surfactant

A series of mesoporous silicas (MS-1-MS-9) were synthesized at different gel compositions using a triblock copolymer (TCP), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), as the surfactant. The interactive effects of acidity, the contents of tetraethyl orthosilicate (TEOS) and the surfactant, and the gelling temperature on the characteristics of the final material were simultaneously characterized. Increasing acidity favored mesopore formation. A material with a surface area of 760 m²/g, mostly in the mesoporous range, was obtained at 1.0(TEOS):0.017(TCP):7.3HCl:115.7H₂O. Mesopore formation was predominantly determined by the TEOS:TCP ratio and was promoted with its increase from 1.56:1 to 2.09:1. A further increase to 2.61:1 was detrimental. Whereas increasing the TCP content to 3.5% w/w improved micellization, a further increase to 4.6% should be avoided. Mesoporous silicas showed low crystallinity but a high degree of hexagonal mesoscopic organization. The weak surface acidity was attributed to surface silanols, the number of which was proportional to mesoporosity.     

Design of single-site Ti embedded highly hydrophilic silica thin films with macro-mesoporous structures

Single-site Ti-containing macroporous silica thin films with mesoporous frameworks were successfully prepared on quartz substrate with high transparency by using poly(methyl methacrylate) (PMMA) microspheres and organic surfactant as template of porous structures. The presence of mesoporous structure and the differences of macroporous structure of film surface were investigated by XRD and FE-SEM measurements. The local structure of Ti moieties embedded within silica matrixes were also confirmed by UV-vis investigations. It was found that the macroporous structure and the embedded single-site Ti moieties within mesoporous frameworks were quite effective for improvement of surface hydrophilicity, i.e., the water droplet was entirely spread on the film surface even before and after irradiation of UV light.     

A simple route to the synthesis of BaCrO4 microstructures at room temperature

BaCrO₄ with various morphologies such as X-shaped, shuttle, rhombus was produced by using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (P123) as a structure-directing agent at room temperature. The effects of experimental parameters on the morphology of BaCrO₄ were investigated. This synthetic route was also extended to the synthesis of BaWO₄ and Pb₂CrO₅. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform-infrared spectroscopy (FT-IR). The photoluminescence (PL) of the sample was investigated.     

Synthesis of mesostructured titanium dioxide films by surfactant-templated sol-gel method

Mesostructured titanium dioxide films have been synthesized by modifying sol-gel methods in the presence of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) block copolymer surfactants as a structure-directing agent. The synthesized films were analyzed using X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM) and selected area electron diffraction (SAED). XRD investigation revealed that as-deposited and as-dried films showed a hexagonal arrangement. With increasing heat-treatment temperature, the mesostructure of the films degraded. From TEM and SAED studies, the degradation of the mesostructure can be explained by the grain growth of microcrystalline titanium dioxide.     

Synthesis and characterization of ordered and cubic mesoporous silica crystals under a moderately acidic condition

Ordered and cubic mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer as template under a moderately acidic condition of 0.5 mol/l HCl solution. These mesoporous materials were characterized by Fourier transform (FT) IR spectroscopy, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements. The three-dimensional cage-like microporosity of the prepared mesoporous silica having ordered hexagonal mesoporous structure was evidenced by the well-defined XRD patterns combined with TEM photographs. SEM observation shows a highly regular cubic crystal structure for the prepared mesoporous silica. The size of these crystallites was maintained within the range between 4 and 6 μm, which is fairly important for the application to the stationary phase for separation. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica possesses a small pore diameter of 3.68 nm, a total surface area of 363.648 m²/g, a total pore volume of 0.379 cm³/g, and a pore-wall thickness of 6.63 nm. These features may lead to higher thermal and hydrothermal stability, excellent microporosity, and good connectivity. The mesoporous silica prepared in this study exhibits potential applications to catalysis, sensoring, and separation.     

New Triblock Copolymer Templates,PEO‐PB‐PEO,for the Synthesis of Titania Films with Controlled Mesopore Size,Wall Thickness,and Bimodal Porosity

The synthesis and properties of a series of new structure‐directing triblock copolymers with PEO‐PB‐PEO structure (PEO = poly(ethylene oxide) and PB = polybutadiene) and their application as superior pore‐templates for the preparation of mesoporous titania coatings are reported. Starting from either TiCl₄ or from preformed TiO₂ nanocrystalline building blocks, mesoporous crystalline titanium oxide films with a significant degree of mesoscopic ordered pores are derived, and the pore size can be controlled by the molecular mass of the template polymer. Moreover, the triblock copolymers form stable micelles already at very low concentration, i.e., prior to solvent evaporation during the evaporation‐induced self‐assembly process (EISA). Consequently, the thickness of pore walls can be controlled independently of pore size by changing the polymer‐to‐precursor ratio. Thus, unprecedented control of wall thickness in the structure of mesoporous oxide coatings is achieved. In addition, the micelle formation of the new template polymers is sufficiently distinct from that of typical commercial PPO‐PEO‐PPO polymers (Pluronics; PPO = poly(propylene oxide)), so that a combination of both polymers facilitates bimodal porosity via dual micelle templating.     

Superior anti-corrosion and self-healing bi-functional polymer composite coatings with polydopamine modified mesoporous silica/graphene oxide

In this article,graphene oxide (GO) and benzotriazole-loaded mesoporous silica nanoparticles (BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine (PDA),preparing a self-healing bi-functional GO (fGO) used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP) coatings.Scanning electronic microscopy (SEM) images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has pH-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42 × 107 Ω cm2) after 30 days immersion in 3.5 wt.％ NaCl solution revealed 2 orders of magnitude higher that of blank WEP (1.17 × 105 Ω cm2).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.     

Core/shell nanoparticles for pH-sensitive delivery of doxorubicin

Core/shell nanoparticles with lipid core were prepared and characterized as pH-sensitive delivery system of anticancer drug. The lipid core is composed of drug-loaded lecithin and the polymeric shell is composed of Pluronics (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer, F-127). Based on the preparation method in the previous report by us, the freeze-drying of drug-loaded lecithin was performed in the F-127 aqueous solution containing trehalose used as a cryoprotectant to form stabilized core/shell nanoparticles. For the application of core/shell nanoparticles as a pH-sensitive drug delivery system for anticancer drug, doxorubicin was loaded into the core/shell nanoparticles and the drug loading amount and drug release behavior in response to pH change were observed.     

Illumination-induced properties of highly ordered mesoporous TiO2 layers with controlled crystallinity

The evaporation-induced self-assembly method using a novel diblock (poly(ethylene-co-butylene)-b-poly(ethylene oxide)) copolymer (KLE) provides fully crystalline mesoporous layers of TiO₂ exhibiting high thermal stability up to 700 °C, high photocatalytic activity in the decomposition of methyl stearate and facile transformation into a substantially stable superhydrophilic state by 1 mW/cm² UV-illumination.     

Ordered mesoporous ZnO for gas sensing

We report on the synthesis and the gas-sensing properties (CO and NO₂ detection) of mesoporous zinc oxide. A two-step structure replication method for the synthesis is employed. In the first step mesoporous SBA-15 silica is prepared by the utilization of self-organization of amphiphilic organic agents. This mesoporous silica is used as the structure matrix for synthesizing mesoporous carbon CMK-3, which, in turn, is employed for yet another replication step, using zinc nitrate as the precursor. The resulting material is characterized by X-ray diffraction and nitrogen physisorption and its gas-sensing properties are compared with a non-porous ZnO sample.     

Precise control of the Pt nanoparticle size by seeded growth using EO13PO30EO13 triblock copolymers as protective agents

Here, we report an efficient way to produce homogeneous Pt nanoparticles within a well-defined size range (3.5-6.6 nm) as a result of the seeded growth procedure using Pluronic L64 polymer capping agent. First, small seeds (3.5 nm) were prepared by the reduction of H2PtCl6.6H2O in water with NaBH4 in the presence of the capping poly(ethylene oxide)13-poly(propylene oxide)30-poly(ethylene oxide)13 triblock copolymer at room temperature. Additional anionic Pt salt was then introduced under flowing H2 to obtain larger nanoparticles.     

Converting liability into asset: novel mesoporous zeotype from fly ash using silatrane chemistry

Fly ash has become a major liability. We report here a clean technology to convert this liability into an asset. Novel mesoporous zeotype, UDCaT-8 was synthesized by using a unique process based on silatrane chemistry. Instead of costly silanes and alkoxides, fly ash was utilized as a raw material. In this process, silicon and aluminium oxide dissolutions were carried out with ethylene glycol in the presence of amines as organic bases. The silatrane and alumatrane glycolate complexes thus formed were converted to a novel mesoporous zeotype via double-stage heating process (pyrolysis followed by oxidation).     

Hydrothermal preparation of mesoporous TiO2 powder from Ti(SO4)2 with poly(ethylene glycol) as template

Mesoporous titania powder with anatase structure was prepared by hydrothermal synthesis from low-cost Ti(SO₄)₂ water solution with nontoxic poly ethylene glycol (PEG) as a templating agent. The templating pathway was suggested to use hydrogen bonding interaction between the hydrophilic surfaces of flexible rod- or worm-like micelles and the hydrothermal products of Ti(OH)₄ to assemble an inorganic oxide framework. The mesoporous channel structures with diameters about 3 nm to 18 nm were achieved by adding appropriate amount of PEG with average moelcular weight of 200. The obtained powder showed good performance for the degradation of gaseous formaldehyde. These results suggested that hydrothermal synthesis with PEG templating provided a low-cost and convenient pathway to synthesis mesoporous TiO₂ powder from water solution system.     

Synthesis of mesoporous silica monoliths with embedded nanoparticles

Mesostructured silica-nanoparticle monolithic composites have been synthesized by dispersing prefabricated nanoparticles of gold or zeolite (silicalite) in ethanolic reaction mixtures containing SiCl4 and a Pluronic triblock copolymer template. Whereas silicalite nanoparticles were used directly, surface functionalization of the gold nanoparticles with either primed silicate ions or a discrete 3-5-nm-thick silica shell was required to increase the interfacial compatibility with the hydrophilic poly(ethylene oxide) blocks. Under these conditions, the resulting monoliths consisted of distributed nanoparticles within an ordered mesostructured silica matrix. Removal of the polymer template by calcination produced corresponding mesoporous silica-nanoparticle replicas. The combination of the structure and the porosity of the silica framework with the crystal chemical properties of the embedded nanoparticles suggests that such composites should be useful as multifunctional materials.     

Synthesis and sensitivity properties of Pd-doped tin oxide nanoparticles dispersed in mesoporous silica

Pd-doped tin oxide nanoparticles dispersed in mesoporous silica were prepared by a thermal-decomposing method and characterized by isothermal nitrogen adsorption measurement, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tin oxide nanoparticles grow up slowly owing to confinement of the pores of the mesoporous silica. Due to the unique microstructure of the mesoporous silica, the obtained nanocomposite consists of a three-dimensional web of interconnected crystallites of tin oxide and exhibits electronic conductivity when enough tin oxide is assembled in the silica pores. The obtained nanocomposite has also a large specific surface area, and the tin oxide nanoparticles have a free surface in contact with the ambient air. Therefore, the samples exhibit a high sensitivity to CO gas, and have potential application.     

Facile synthesis of ordered mesoporous silica with high γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> loading via sol-gel process

A series of ordered mesoporous silica loaded with iron oxide was synthesized by facile one-step sol-gel route using Pluronic P123 as the template, tetraethylorthosilicate as the silica source, and hydrated iron nitrite as the precursor under acid conditions. The as-synthesized materials with Fe/Si molar ratio ranging from 0.1 to 0.8 were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and N₂ adsorption porosimetry. All samples possess ordered hexagonal mesoporous structure similar to SBA-15, with a high surface area, large pore volume, and uniform pore size. Although higher iron content causes a distortion of hexagonal ordering structure to some extent, the materials still maintain the ordered mesopore structure even with Fe/Si molar ratio as high as 0.8. Pore structure and TEM data suggest that iron oxide nanoparticles are buried within the silica wall, and increasing the iron oxide loading has little effects on the pore structure of the mesoporous silica. VSM results show as-synthesized samples exhibit superparamagnetic behavior.