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.     

Synthesis of paramagnetic iron incorporated silica aerogels by ambient pressure drying

The iron incorporated silica aerogels were prepared under ambient pressure drying through a two-step sol-gel route by using tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and ferric nitrate as co-precursors, and hexamethyldisilazane (HMDZ) as a surface modification reagent. Compared with the silica aerogels modified by trimethylchlorosilane (TMCS) or HMDZ, the iron incorporated silica aerogels exhibited good integrity, paramagnetic behavior, and highly hydrophobicity which could be maintained up to 650 °C. However, the introduction of iron into silica aerogels resulted in more apparent volume shrinkage, higher density, lower porosity, and smaller pore diameter. It was found that a large amount of water was retained in the silica network, accordingly, the water containing iron oxides (Fe–OH) were more readily formed than water free iron oxides (Fe–O), which adversely affected the physical properties of iron incorporated silica aerogels.     

Synthesis, phase transition, and magnetic property of iron oxide materials: effect of sodium hydroxide concentrations

In this paper, a class of novel iron oxide particles has been fabricated through surfactant-directed structure approach in hydrothermal reaction. The obtained iron oxide nanostructures with distinct morphologies, such as rhombohedra, octahedral, plate-like, as well as dendritic, can be obtained by gradually increasing the concentrations of NaOH. The as-prepared iron oxide particles were characterized utilizing scanning electronic microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results reveal that the as-made particles, such as rhombohedra and octahedral, can be indexed as pure rhombohedral phase of hematite and show better single crystalline feature. In contrast, when NaOH concentrations are 1.05 and 6 M, respectively, we accordingly can obtain novel flake-like and dendrtic superstructure that possess a mean arm length of ~1.5 μm; both the as-made two samples can be easily indexed as a mixture of hematite and maghemite based on their XRD and TEM results. Additionally, it was found that the obtained iron oxide samples at different NaOH concentrations show obviously morphologies-dependent feature. Namely, the as-made samples can undergo transition from typical ferromagnetic to ferrimagnetic behavior when the NaOH concentrations are gradually increased. In general, the presented synthesis approach could be extended to prepare other metal oxides with specific morphology and structure.     

Synthesis of novel thiol-functionalized mesoporous silica nanorods and their sorbent properties on heavy metals

Novel thiol-functionalized mesoporous silica nanorods (MSNRs) were synthesized through a base co-condensation method, in which two organoalkoxysilanes, tetraethoxylsilane (TEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), were used as silica precursors simultaneously. TESPT was firstly used for both morphology control and inner surface functionalization of mesoporous silica hybrid materials. The microstructures as well as porous character of the MSNRs were characterized by means of SEM, XRD, TEM and N₂ sorption measurements. Infrared spectrum analysis and heavy metal ions (Ag⁺ and Cd²⁺) adsorption measurements were carried out to confirm the functionalized framework of MSNRs.     

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.     

Mixed micelle-template route to mesoporous silica

Mesoporous silica materials were prepared through a novel mixed micelle-template method which was employed by alkyl polyethylene oxide (C16,E20) and C2-ceramide. X-ray diffraction patterns clearly showed the formation of mesoporous silica by contribution of mixed micelle-template up to 3/1 weight ratio (C16E20/C2-ceramide). TEM and N2 adsorption isotherms analyses indicated that the mesoporous structure was maintained even after encased C2-ceramides. However, when the weight ratio of C16E20/C2-ceramide exceeds 2/2, less ordered and irregular pore structure was observed. According to the in-vitro experiment on cancer cells such as MCF-7, HOS, and HepG2, the simultaneously encapsulated C2-ceramide shows apoptosis. Therefore, the present results could provide a new method for mesoporous material as drug delivery system.     

Preparation of silica coated iron oxide nanoparticles using non-transferred arc plasma

Silica coated iron oxide nanoparticles were prepared using non-transferred arc plasma. The plasma was discharged with argon. Vapors of iron pentacarbonyl (Fe(CO)₅) and tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄) were injected into a plasma torch with carrier gas and reacted in the plasma chamber. In addition, two types of reaction chambers that are a hot wall reactor and a cold wall reactor were used to investigate the effect of temperature gradient on the synthesis of silica coated iron oxide nanoparticles. The synthesized nanoparticles were collected on the chamber wall and bottom. Phase compositions of the obtained nanoparticles were characterized by X-ray diffractometer (XRD) and the morphologies and the size distributions of the synthesized particles were analyzed by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Additionally, elements mapping of the coated particles was performed by energy dispersive spectroscopy (EDS). The phase composition of the prepared particles was mainly composed of amorphous silica and polycrystalline Fe₃O₄. It was confirmed that the silica was adsorbed on iron oxide particles or encapsulated iron oxide particles. Furthermore, the mechanism of the formation of silica coated iron oxide in the plasma chamber was predicted.     

中孔炭的水玻璃模板法制备、结构调控及球形功能化

以廉价水玻璃为原料, 通过控制水解条件, 合成出具有不同尺寸的SiO₂溶胶, 并与间苯二酚-甲醛(RF)溶胶形成均相的凝胶复合物, 经常压干燥、炭化、酸洗, 得到具有可控结构的中孔炭材料。考察了水解温度、水解时间和反应物组成对孔结构的影响, 并通过氮气吸附、扫描电镜和透射电镜对材料的微观结构进行了表征。结果表明: 中孔炭的孔隙反相复制于SiO₂凝胶网络, 其平均孔径随水解时间的延长或水解温度的升高而增大, 并在6~12 nm范围内精细调控, 而其总孔隙率可以通过改变炭、SiO₂前驱体比例调节。对液相复合溶胶通过悬浮聚合法和喷雾干燥法处理, 分别制备出毫米级和微米级的中孔炭球, 进而实现了中孔炭在宏观形貌上的调控。本工作为中孔炭的低成本制备、精细结构调控以及球形功能化提供了重要参考。     

Template synthesis of magnetic one-dimensional nanostructured spinel MFe2O4 (M = Ni, Mg, Co)

The iron nitrate and suitable salt of nickel, cobalt, or magnesium with molar ratio of 2:1 were introduced into the pores of mesoporous silica SBA-15 via two-solvent method. The thermal decomposition of the precursors and the formation of one-dimensional nanostructured spinel ferrite in SBA-15 pores were monitored by XRD, TG-DTA, N₂ adsorption-desorption, and TEM. The pure spinel MFe₂O₄ nanowires obtained through complete removal of the silica template with aqueous NaOH solution were confirmed by TEM and HRTEM. The spinel MFe₂O₄ nanowires showed increasing normal configuration and exhibited superparamagnetism in comparison with the bulk ones.     

Porous manganese oxide synthesized through organic-electrolyte templates and their catalytic applications

We report a facile approach to the preparation of porous manganese oxide materials by the organic-electrolyte templates based on strategy. The final products are thoroughly characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and Brunauer–Emmett–Teller (BET) techniques. The results reveal that porosity (pore size and distribution, surface area) of these manganese oxides has strong relationship with the templates used, which implies a simple way to obtain a series of porous materials. By comparing the catalytic effects of these manganese oxides in oxidation of indene and benzyl alcohol, we find that the pore size and distribution are also crucial to the catalytic properties of these porous materials.     

Synthesis of Fe-Ti-MCM-48 from silatrane precursor via sol-gel process and its hydrothermal stability

A series of bimetallic Fe–Ti-MCM-48 materials was successfully synthesized via sol–gel method using cetyltrimethylammonium bromide (CTAB) as a template and silatrane, iron (III) chloride, and titanium (IV) isopropoxide as silica, iron, and titanium sources, respectively. Scanning electron microscopy (SEM) showed the truncated octahedron morphology of Fe–Ti-MCM-48.X-ray diffraction (XRD) patterns showed well-defined, order cubic mesoporous structures. X-ray fluorescence (XRF) revealed the total metal content of the final product. UV–visible absorption spectra confirmed both iron (Fe³⁺) and cerium (Ti⁴⁺) species highly dispersed in the framework, while N₂ adsorption/desorption measurements indicated a high specific surface area. As metal content increased, the mesoporous order and surface area decreased. The synthesized Fe–Ti-MCM-48 with 0.01Fe/Si and 0.01Ti/Si ratio still retained a cubic structure after hydrothermal treatment at 100 °C for 72 h.     

Ultrasonic-assisted synthesis and magnetic studies of iron oxide/MCM-41 nanocomposite

Iron oxide nanoparticles were stabilized within the pores of mesoporous silica MCM-41 amino-functionalized by a sonochemical method. Formation of iron oxide nanoparticles inside the mesoporous channels of amino-functionalized MCM-41 was realized by wet impregnation using iron nitrate, followed by calcinations at 550 °C in air. The effect of functionalization level on structural and magnetic properties of obtained nanocomposites was studied. The resulting materials were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy and selected area electron diffraction (HRTEM and SAED), vibrating sample and superconducting quantum interface magnetometers (VSM and SQUID) and nitrogen adsorption–desorption isotherms measurements. The HRTEM images reveal that the most of the iron oxide nanoparticles were dispersed inside the mesopores of silica matrix and the pore diameter of the amino-functionalized MCM-41 matrix dictates the particle size of iron oxide nanoparticles. The obtained material possesses mesoporous structure and interesting magnetic properties. Saturation magnetization value of magnetic iron oxide nanopatricles stabilized in MCM-41 amino-functionalized by in situ sonochemical synthesis was 1.84 emu g⁻¹. An important finding is that obtained magnetic nanocomposite materials exhibit enhanced magnetic properties than those of iron oxide/MCM-41 nanocomposite obtained by conventional method. The described method is providing a rather short preparation time and a narrow size distribution of iron oxide nanoparticles.     

Multifunctional iron and iron oxide nanoparticles in silica

Iron and iron oxide nanoparticles in silica layers deposited by sol–gel techniques on Si wafers were formed and studied. It was shown that multifunctional nanoparticles of different iron oxides possessing various physical properties can be fabricated by means of post-growth annealing of (SiO₂:Fe)/SiO₂/Si samples in various atmospheres. The hematite, maghemite, and iron nanoparticles were found to be dominant upon annealing the samples in air, argon, and hydrogen atmosphere, respectively. The physical properties of produced hybrid structures were studied by Raman and FT-IR spectroscopy, spectroscopic ellipsometry, AFM, and magnetic measurements. The sol–gel technique with subsequent annealing procedure is demonstrated to be an effective method for the formation of multifunctional hybrid structures composed of iron or iron oxide nanoparticles in silica matrix.     

介孔氧化铁的制备与表征

以氢氧化钠和三氯化铁为原料,通过控制碱和铁盐的比例来制备铁的聚合物溶液,然后以十二烷基硫酸钠（SDS）为模板剂制备了介孔氧化铁. 通过X射线粉末衍射、热重分析、红外光谱、氮气吸附脱附方法对不同焙烧温度下样品的晶体结构和表面结构进行表征. 结果显示,OH^-/Fe³⁺摩尔比为2.0,焙烧温度为450℃时,样品完全转化为α-Fe₂O₃. 制备的介孔氧化铁有较大的表面积（146.5m²·g^-1）,BJH平均孔径为6.9nm,孔体积为0.27cm³·g^-1. 所制备的介孔氧化铁有较好的热稳定性,经550℃高温焙烧表面积仍有110.2 m²·g^-1.     

Multiscale Phase Separations for Hierarchically Ordered Macro/Mesostructured Metal Oxides

Porous architectures play an important role in various applications of inorganic materials. Several attempts to develop mesoporous materials with controlled macrostructures have been reported, but they usually require complicated multiple‐step procedures, which limits their versatility and suitability for mass production. Here, a simple approach for controlling the macrostructures of mesoporous materials, without templates for the macropores, is reported. The controlled solvent evaporation induces both macrophase separation via spinodal decomposition and mesophase separation via block copolymer self‐assembly, leading to the formation of hierarchically porous metal oxides with periodic macro/mesostructures. In addition, using this method, macrostructures of mesoporous metal oxides are controlled into spheres and mesoporous powders containing isolated macropores. Nanocomputed tomography, focused ion beam milling, and electron microscopy confirm well‐defined macrostructures containing mesopores. Among the various porous structures, hierarchically macro/mesoporous metal oxide is employed as an anode material in lithium‐ion batteries. The present approach could provide a broad and easily accessible platform for the manufacturing of mesoporous inorganic materials with different macrostructures.     

Arsenic removal by electrocoagulation using combined Al-Fe electrode system and characterization of products

Combination of electrodes, such as aluminum and iron in a single electrochemical cell provide an alternative method for removal of arsenic from water by electrocoagulation. The removal process has been studied with a wide range of arsenic concentration (1–1000 ppm) at different pH (4–10). Analysis of the electrochemically generated by-products by XRD, XPS, SEM/EDAX, FT-IR, and Mössbauer Spectroscopy revealed the expected crystalline iron oxides (magnetite (Fe₃O₄), lepidocrocite (FeO(OH)), iron oxide (FeO)) and aluminum oxides (bayerite (Al(OH)₃), diaspore (AlO(OH)), mansfieldite (AlAsO₄·2(H₂O)), as well as some interaction between the two phases. The amorphous or very fine particular phase was also found in the floc. The substitution of Fe³⁺ ions by Al³⁺ ions in the solid surface has been observed, indicating an alternative removal mechanism of arsenic in these metal hydroxides and oxyhydroxides by providing larger surface area for arsenic adsorption via retarding the crystalline formation of iron oxides.     

Porous graphitic materials obtained from carbonization of organic xerogels doped with transition metal salts

Porous carbons with a well developed graphitic phase were obtained via the pyrolysis of FeCl₃-, NiCl₂-, and CoCl₂-doped organic xerogels. Doping was realized through salt solubilization in a water/methanol solution of resorcinol and furfural. Carbon xerogels with tailored particles, porous morphology and various degrees of graphitization were obtained depending of the water/methanol ratio and the salt content and type in the starting solution of substrates. When obtained via pyrolysis, carbon xerogels retain the overall open-celled structure exhibiting depleted microporosity and a well-developed mesoporic region that expands into macropores. The removal of metal leads to carbon xerogels with specific surface areas between 170 and 585 m²/g and pore volume up to 0·76 cm³/g. The possibility of enhancing the porosity of xerogels via templating with colloidal silica was also investigated. It was assumed that from the three investigated salts, FeCl₃ makes the best choice for graphitization catalyst precursor to obtain uniformly graphitized mesoporous carbon xerogels. The obtained carbon samples were characterized by means of SEM, TEM, X-ray diffraction, Raman spectroscopy, N₂ physisorption and thermogravimetric analysis.     

Alignment under Magnetic Field of Mixed Fe2O3/SiO2 Colloidal Mesoporous Particles Induced by Shape Anisotropy

When using the bottom‐up approach with anisotropic building‐blocks, an important goal is to find simple methods to elaborate nanocomposite materials with a truly macroscopic anisotropy. Here, micrometer size colloidal mesoporous particles with a highly anisotropic rod‐like shape (aspect ratio ≈ 10) have been fabricated from silica (SiO₂) and iron oxide (Fe₂O₃). When dispersed in a solvent, these particles can be easily oriented using a magnetic field (≈200 mT). A macroscopic orientation of the particles is achieved, with their long axis parallel to the field, due to the shape anisotropy of the magnetic component of the particles. The iron oxide nanocrystals are confined inside the porosity and they form columns in the nanochannels. Two different polymorphs of Fe₂O₃ iron oxide have been stabilized, the superparamagnetic γ‐phase and the rarest multiferroic ε‐phase. The phase transformation between these two polymorphs occurs around 900 °C. Because growth occurs under confinement, a preferred crystallographic orientation of iron oxide is obtained, and structural relationships between the two polymorphs are revealed. These findings open completely new possibilities for the design of macroscopically oriented mesoporous nanocomposites, using such strongly anisotropic Fe₂O₃/silica particles. Moreover, in the case of the ε‐phase, nanocomposites with original anisotropic magnetic properties are in view.     

纳米白炭黑对介孔蒙脱石水热稳定性的增强作用

纯化学试剂合成的介孔分子筛, 由于水热稳定性较差、成本较高, 因而限制了其在催化、吸附等工业领域的大规模应用. 以廉价且高结晶度的天然矿物蒙脱石为原料, 选用硅酸钠和工业白炭黑作为补充硅源, 成功地合成了具有优异水热稳定性的介孔蒙脱石. 使用XRD、FTIR、TEM、N₂脱吸附等温线等手段对介孔蒙脱石的结构进行了分析, 并讨论了高能球磨、搅拌时间、补充硅源种类等因素对样品结构及水热稳定性的影响. 实验结果表明, 以硅酸钠-纳米白炭黑复合无机硅源制备的介孔粘土具有十分优异的稳定性, 样品水热反应10d后依然保持着规则的介孔结构, 且比表面积仍在580m²/g以上.     

Novel mesoporous composites based on natural rubber and hexagonal mesoporous silica: Synthesis and characterization

The present study is the first report on the synthesis and characterization of mesoporous composites based on natural rubber (NR) and hexagonal mesoporous silica (HMS). A series of NR/HMS composites were prepared in tetrahydrofuran via an in situ sol–gel process using tetraethylorthosilicate as the silica precursor. The physicochemical properties of the composites were characterized by various techniques. The effects of the gel composition on the structural and textural properties of the NR/HMS composites were investigated. The Fourier-transform infrared spectroscopy (FTIR) and ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR) results revealed that the surface silanol groups of NR/HMS composites were covered with NR molecules. The powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) data indicated an expansion of the hexagonal unit cell and channel wall thickness due to the incorporation of NR molecules into the mesoporous structure. NR/HMS composites also possessed nanosized particles (∼79.4 nm) as confirmed by scanning electron microscopy (SEM) and particle size distribution analysis. From N₂ adsorption–desorption measurement, the NR/HMS composites possessed a high BET surface area, large pore volume and narrow pore size distribution. Further, they were enhanced hydrophobicity confirmed by H₂O adsorption–desorption measurement. In addition, the mechanistic pathway of the NR/HMS composite formation was proposed.