A study on the structural properties of mesoporous silica spheres

The mesoporous silica spheres were prepared by using sodium silicate as silica precursor, and low concentration of CTAB and propanol as templating agents. The resulting spherical particles were characterised by low angle PXRD, N₂ adsorption-desorption studies, pore size distribution, BET-surface area, surface morphology analysis and FTIR. From PXRD data and electron probe microanalysis, it was observed that the propanol:CTAB molar ratio 8.5:1 is the optimum for preparing the mesoporous silica spheres. With excess of propanol the orderliness of mesoporous silica has been disturbed forming agglomerate particulates. Again the BJH pore diameter and cell parameter (a) go on decreasing with the increase in the propanol:CTAB molar ratio.     

双金属催化剂Ni-Co/SiO2空心球的可控制备及催化性能

以二氧化硅为模板, 采用牺牲模板/界面反应法制备具有介孔结构的碱式硅酸镍钴空心球。采用透射电子显微镜(TEM)、X 射线衍射(XRD)、氮气吸脱附曲线(BET)和程序升温还原(TPR)等方法, 对样品的结构和形貌进行了表征, 探索了碱式硅酸镍钴空心球还原规律, 并研究了双金属催化剂Ni-Co/SiO₂的催化性能。研究发现, 140℃下反应6 h, 产物为核壳结构, 反应12 h时变为空心球结构; 在氢气气氛中800℃下反应5 h, 碱式硅酸镍钴被完全还原为Ni-Co/SiO₂, 还原前后形貌基本不变, 但比表面积有所减小, 孔径增大。Ni-Co/SiO₂空心球用于催化硝基苯加氢反应1 h后, 硝基苯的转化率为67%, 比商用Raney Ni 提高约28%。     

介孔硅酸锰镁可充镁电池正极材料的制备及其电化学性能研究

采用介孔二氧化硅MCM-41作模板和硅源, 合成了具有介孔结构的可充镁电池正极材料硅酸锰镁. 分别用XRD、SEM、TEM和氮气吸脱附测试研究了合成材料的介孔结构, 并通过循环伏安、恒电流充放电测试比较了介孔与无孔硅酸锰镁材料的电化学性能. 由于介孔材料活性表面较大, 可增加电解液与活性材料的接触, 使材料具有较多的电化学反应位. 因而, 与相应的无孔材料相比, 具有介孔结构的硅酸锰镁材料呈现出较低的充放电极化、较大的放电容量和较高的放电电压平台. 在0.25 mol/L Mg(AlCl₂EtBu)₂/THF 电解液中, 0.2 C(约62.8 mA/g)充放电速率下, 介孔硅酸锰镁材料首次放电容量可达到241.8 mAh/g, 放电平台为1.65 V ( vs Mg/Mg²⁺). 设计具有介孔结构的材料为提高可充镁电池正极的电化学性能提供了一条有效的途径.     

Synthesis and photocatalytic oxidation properties of titania hollow spheres

The hollow spheres of anatase TiO₂ with higher photocatalytic activity have been fabricated by spherical CaCO₃ nanoparticles as a template, and titanium sulfate (Ti(SO₄)₂) as a precursor, and the CaCO₃ templates were dissolved subsequently in dilute HNO₃ solution. The TiO₂ hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption isotherms. The characterization results indicate that as prepared TiO₂ hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO₂ hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.     

Highly ordered three-dimensional macroporous carbon spheres for determination of heavy metal ions

An effective voltammetric method for detection of trace heavy metal ions using chemically modified highly ordered three dimensional macroporous carbon spheres electrode surfaces is described. The highly ordered three dimensional macroporous carbon spheres were prepared by carbonization of glucose in silica crystal bead template, followed by removal of the template. The highly ordered three dimensional macroporous carbon spheres were covalently modified by cysteine, an amino acid with high affinities towards some heavy metals. The materials were characterized by physical adsorption of nitrogen, scanning electron microscopy, and transmission electron microscopy techniques. While the Fourier-transform infrared spectroscopy was used to characterize the functional groups on the surface of carbon spheres. High sensitivity was exhibited when this material was used in electrochemical detection (square wave anodic stripping voltammetry) of heavy metal ions due to the porous structure. And the potential application for simultaneous detection of heavy metal ions was also investigated.     

A novel route to synthesis Aluminum silicate hollow spheres having ZSM-5 structure in absence of template

A novel route to synthesize Aluminum silicate hollow spheres with thick walls having ZSM-5 structure without using any template at 150 °C was presented. X-ray diffraction (XRD), Scanning electron microscopy (SEM), TG/DTA, FT-IR and nitrogen adsorption were employed to characterize the morphology and microstructures of the as-prepared silica hollow spheres. Experimental results indicated that the hollow spheres had an average diameter of nearly 200 nm with a surface area of 342 m²/g.     

Synthesis of silica nanoboxes via a simple hard-template method and their application in controlled release

Silica nanoboxes have been successfully synthesized via a simple hard-template method at room temperature. The MnCO₃ nanocubes are firstly employed as the hard template. Scanning electron microscopy (SEM) is used to characterize silica nanoboxes and indicates the hollow structure of products. The shell thickness of nanoboxes can be well controlled by the amount of tetraethylorthosilicate (TEOS) and the surface area is calculated through the N₂ adsorption-desorption isotherm. Based on these results, a plausible mechanism is proposed to explain the formation of silica nanoboxes. In addition, preliminary tests demonstrate that the silica nanoboxes are capable of being loaded and releasing Rhodamine B, thus showing a great potential in the controlled delivery applications.     

Highly ordered mesostructured silica spheres as template for polyaniline nanofibres: synthesis,characterisation and their electrochemical properties

Ordered micrometre-sized silica spheres with uniform morphology and mesoporous structures were prepared by a temperature-induced and polyethylene glycol-assisted assembly method. The porous surface of the silica spheres was used for the chemical polymerisation of aniline, as well as a sacrificial template for synthesis of polyaniline (PANI) nanofibres. The morphologies of PANI nanostructures were characterised by scanning electron microscopy and transmission electron microscopy. Microstructural analysis and properties evaluation of the as-prepared products were characterised by X-ray diffraction, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy and N₂ adsorption–desorption analysis. TGA results demonstrated that about 95% of the mesoporous material has been utilised for the synthesis of PANI nanofibres. Their electron transfer properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. CV experiment shows that the obtained PANI nanofibres have good electrochemical activity, which can be attributed to a higher number of accessible redox sites available during the synthesis process. The value of time constant (Γ) of PANI nanofibres based electrode was 0.0217?ms. The lower Γ-value is usually preferred for electrochemical capacitor for fast charge–discharge processes; hence, these PANI nanofibres based materials and their composites have the potential to be used as supercapacitor electrodes for supercapacitor applications.     

Fabrication of superparamagnetic hydroxyapatite with highly ordered three-dimensional pores

Hydroxyapatite (HA) with highly ordered three-dimensional pores, whose size is about 300 nm, was prepared by colloidal template method. The effect of the surface modification of silica spheres on the order degree of porous structure was investigated by field emission scanning electron microscopy (FESEM). Then, superparamagnetic Fe₃O₄ nanoparticles were fabricated via redox reaction, followed by coating with silica via a sol–gel process, in which a certain amount of TEOS was used in order to control the thickness of the silica shell. X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetometry were applied to characterize the properties. Finally, Fe₃O₄ magnetic nanoparticles coated with silica were adsorbed in the mesopores of HA with highly ordered three-dimensional pores by capillarity. The influence of dispersing agent on the adsorption results has been studied. Magnetometry was applied to characterize the magnetic properties of superparamagnetic HA. The quantities of adsorbed SiO₂/Fe₃O₄ nanoparticles with core–shell have been compared by variation of saturation magnetization before and after adsorption.     

One-step strategy for synthesis of yolk–shell silica spheres using trisiloxane-tailed ionic liquids as a template

Yolk–shell silica spheres consisting of a core and an outer shell were prepared by a one-step method using a new class of eco-friendly templates, trisiloxane-tailed surface active ionic liquids. The effects of pH, calcination, and template concentration were investigated in detail. Our results showed that yolk–shell silica spheres could be obtained only in alkaline conditions when using trisiloxane-tailed ionic liquids as templates. The particle diameter, core diameter, dimension of void space, and shell thickness, which we measured by transmission electron microscopy and nitrogen adsorption–desorption techniques, could be tuned by precisely varying the template concentration. The organosilicon component of the ionic liquid template contributes to the reaction during the formation of yolk–shell nanostructures, which leads to a firm silica sphere skeleton resulting in essentially identical morphology and void structure before and after calcination. This investigation provides a convenient approach to fabricate yolk–shell silica spheres, which may expand the application of organosilicon ionic liquids in the field of nanomaterials and could be expected to generate tailor-made yolk–shell silica with functionality in both the core and shell.     

P(St-EA-MAA)模板法制备中空二氧化硅微球

以种子乳液聚合制得的P(St-EA-MAA)共聚物微球为模板,γ-氨丙基三甲氧基硅烷(APS)为助结构导向剂,正硅酸四乙酯(TEOS)为硅源,制备了P(St-EA-MAA)/SiO2复合微球,经高温煅烧除去聚合物模板,得到了中空二氧化硅微球。热重分析(TGA)表明模板剂的最佳脱除温度为600℃。高分辨透射电镜(HRTEM)观察显示所制得的二氧化硅微球具有典型的中空结构和良好的单分散性,其尺寸主要取决于共聚物微球的大小,通过调节微球模板的尺寸可以有效控制中空微球的大小。N2吸附-脱附曲线显示二氧化硅壁具有丰富的微孔,比表面积、平均孔径和孔容分别为117.87m2/g、1.98nm和0.21cm3/g。在制备复合微球的过程中加入一定量的CTAB可以调整中空微球的壁厚和壁的孔结构,使其比表面积、平均孔径和孔容增加到219.79m2/g、3.89nm和0.25cm3/g。     

The size modulation of hollow mesoporous carbon spheres synthesized by a simplified hard template route

Hollow mesoporous carbon spheres (HMCSs) have been prepared by a simplified replication route from a solid silica core/mesoporous silica shell aluminosilicate (SCMS-Al) template, which was synthesized by directly incorporating aluminum species into the mesoporous framework during template synthesis. The size of HMCSs can be tuned between 80 and 470 nm by simply changing the diameters of SCMS-Al. The HMCSs have uniform mesopores with a narrow pore size distribution (3.4-4.1 nm), and high surface area, (890-1150 m²/g) and total pore volumes (0.75-1.15 cm³/g). The techniques of N₂ sorption isotherms, TEM, EDX and SEM were used to characterize the as-synthesized spheres.     

Fabrication of hollow silver spheres by MPTMS-functionalized hollow silica spheres as templates

In this study, we provide a strategy to prepare the hollow silver spheres by accumulating the silver nanoparticles on the surface of 3-mercaptopropyltrimethoxysilane (MPTMS)-functionalized silica as templates, which was accomplished by the chemisorption between silver nanoparticles and thiol groups. Then, the resulting hollow silver spheres were obtained through the chemical wet etching process with 10 M HF solution. In conventional method, the fabrication of hollow silver spheres from core-shell spheres was not easy due to the difficulties in retaining the shell structures during core removal. The method in this paper could overcome this limitation. The major focus of study is on understanding the mechanism of formation of the hollow silver spheres through the self-assembly behavior by chemisorption between silver nanoparticles and thiol groups. The silver-coated silica and hollow silver spheres were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and X-ray photoelectron spectroscopy (XPS).     

A novel synthesis of micrometer silica hollow sphere

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented.     

A new synthesis of lamellar-mesostructured silica by using poly(ethylene glycol) distearate as template

A lamellar-mesostructured silica has been synthesized by using poly(ethylene glycol) distearate as template in ethanol solution. Highly ordered lamellar mesostructure was confirmed by X-ray diffraction pattern, transmission electronic microscopy, and nitrogen adsorption-desorption isotherm. The material obtained in this work has a large interlayer distance, and good thermal and mechanical stabilities, which can favor the preparation of the in situ polymerized nanocomposites based on intercalation of polymers in the lamellar-mesostructured silica.     

SiO2空心微球的制备表征及摩擦性能

以分散聚合法制备的聚苯乙烯(PS)微球为有机模板, 以正硅酸四乙酯(C₈H₂₀O₄Si)为无机前躯体物料, 通过静电吸附作用成功地制备了纳米 PS-SiO₂ 复合微球和SiO₂单分散空心结构。通过红外(FTIR)、热重(TG)、透射电镜(TEM)、扫描电镜(SEM) 和热重分析仪(TGA)等手段对纳米复合材料进行了表征, 并对产物的抗磨性能进行了测试。结果表明, 该方法可一次性制备大量的复合微球, 这些微球的直径约为0.7 μm, 分散性能良好。在煅烧去除模板后, 得到了保持完整的空心纳米 SiO₂ 结构, 微球的球壳稳定性较好。摩擦实验表明, 添加了2 wt%空心微球的植物油在较低载荷工况下具有优异的减磨性能, 摩擦系数可低至0.058。      

Fabrication of hollow silica spheres and their application in polyacrylate film forming agent

Polystyrene (PS)/silica core/shell spheres were fabricated using mono-dispersed PS as templates by hydrolysis and condensation of two different silica precursors. The PS cores of PS/silica core/shell spheres were dissolved subsequently in the tetrahydrofuran medium to form mono-dispersed hollow silica spheres. The structures and morphologies of hollow silica spheres were characterized by scanning electron microscopy and transmission electron microscopy. Then, polyacrylate/hollow silica composite film forming agents were prepared via physical blending of polyacrylate and two different hollow silica spheres, and the water vapor permeability of their films were compared. The results showed that the structure of hollow silica spheres were very typical and obvious. The silica shell was continuous and uniform using tetraethylorthosilicate as precursor, which was accumulated by many silica seeds with size of 10–20 nm, and the thickness of silica shell was about 16.7 nm. However, the hollow silica spheres using tetraethylorthosilicate and vinyl triethoxysilane as precursors had mesoporous structure in the shell. The introduction of hollow silica spheres could significantly improve the water vapor permeability of polyacrylate film. At last, a possible mechanism for the formation of hollow silica spheres was proposed and the process of water vapor through polyacrylate/hollow silica composite films was modeled.     

Surface synthesis of PbS nanoparticles on silica spheres by a sonochemical approach

A simple sonochemical approach for the preparation of PbS nanoparticles homogeneously coated on sub-micrometer silica spheres has been described. The transmission electron microscopy and scanning electron microscopy images show that the PbS nanoparticles with size of 30 nm were coated on the silica spheres, without any free nanoparticles. X-ray diffraction reveals that the PbS nanoparticles are of cubic rock-salt structure. Moreover, by dissolving the silica cores with a diluted hydrofluoric acid solution, stable PbS hollow structures were obtained. It is considered that the sonochemical process in which triethanolamine acted as complex agent played an important role for the homogenouse coating of PbS nanoparticles on silica spheres.     

Self-assembly of modified silica nanospheres at the liquid/liquid interface

A stabilized 2 or 3D silica sphere structure was successfully prepared by a 3-step method. First, the surfaces of silica spheres were modified with a functional silane coupling agent 3-methacryloxypropyltrimethoxysilane (γ-MPS); then, the surface-modified silica spheres were self-assembled at the liquid/liquid interface to fabricate a two- or three-dimensional ordered structure; and finally, the formed ordered structure was stabilized by a stable polymerization reaction among the modified silica spheres. The polymerized silica sphere film can be transferred from solution to quartz substrates without destroying its ordered structure. This ordered structure could be potentially used as a photonic band gap material or the template for fabrication of other highly ordered structures.     

Hollow mesoporous aluminosilicate spheres with acidic shell

Hollow mesoporous aluminosilicate spheres (HMAS) with middle strong acidity have been successfully synthesized by simply hydrothermally treating mesoporous silica spheres (MSS) in zeolite precursor solution. Based on a set of time-dependent experiments, it was found that the hollowing process was associated with a progressive mass redistribution and changes of pores structures. The surfactant cetyltrimethylammonium bromide (CTAB) located in the pores of MSS protected the mesoporous silica spheres from dissolving into strongly basic zeolite precursor solution and acted as the template for mesoporous shell. Under the templating function of CTAB, primary zeolite units were introduced into the mesopore walls of HMAS. The acidity of the resultant samples HMAS was measured by NH₃-TPD techniques. Catalytic tests showed that the HMAS catalysts exhibited high catalytic activity compared with the MSS and Hβ zeolite for catalytic cracking of 1,3,5-triisopropylbenzene.