共聚物为模板制备草莓状二氧化硅空心球

成功地通过三嵌段共聚物聚乙二醇-聚丙二醇-聚乙二醇(PEG-PPG-PEG)为模板,正辛烷为壳材料来制备介孔外壳的草莓状二氧化硅空心球。其中正硅酸乙酯(TEOS)作为二氧化硅的前驱体。通过改变反应参数,我们发现当将反应最终溶液先室温下静置24h然后加热到较高温度12h可以获得草莓状结构。产物的表面形貌通过扫描电子显微镜(SEM)来分析;透射电子显微镜(TEM)表明空心球的平均直径为800nm,外壳为20nm;多孔性分析通过氮气吸附-解附法来测量,同时用Brunauer-Emmett-Tell-er(BET)的方法来测孔径大小。另外我们提出了二氧化硅的形成机理。     

Synthesis of hollow α-Fe2O3–silica composites templated by poly(acrylic acid) colloidal aggregates

The synthesis of inorganic hollow nanoparticles has attracted more and more attention in recent research. In this article, hollow α-Fe₂O₃–silica composites were synthesized by a modified Stöber method. Tetraethyl orthosilicate (TEOS) formed oil drops, and ammonia solution facilitated the hydrolysis polymerization of TEOS. In the hydrolysis process of TEOS, we used cetyltrimethylammonium bromide and poly(acrylic acid) colloidal aggregates as the surfactant and template, respectively. The diameters of the composites we obtained are about 20 and 180 nm, respectively, which are smaller than that of pure silica spheres (200 nm). Moreover, Brunauer–Emmett–Teller surface areas of hollow α-Fe₂O₃–silica composites were determined to be in the range of 377–498 m²/g, and their pore sizes are around 2 nm as were determined by BJH method. The mesoporous silica was successfully coated around the α-Fe₂O₃. The synthesis process of the composites is a simple, one-step route, which exhibits the potential need for a great amount of synthesis for future research.     

Exploring the Elastic Behavior of Core–shell Organic–Inorganic Spherical Particles by AFM Indentation Experiments

Monodispersed polystyrene (PS)-silica core–shell composite particles were synthesized via the hydrolysis and condensation of tetraethoxysilane (TEOS) on PS colloids at acidic medium. The thickness of silica coating was controlled by the amount of the addition of TEOS during the shell growth process. Transmission electron microscopy results confirmed that a continuous amorphous network of homogenous coating of silica was formed on the PS colloids. After coating by silica, the particle diameter increased from ca. 221 nm for uncoated PS cores to ca. 243–286 nm for PS-silica composite particles observed by scanning electron microscopy, indicating that the silica shell thickness was 11–32 nm. The elastic behavior of the obtained products was investigated by means of atomic force microscopy. The elastic moduli of samples were calculated by fitting the retract curves in force-separation plots based on the Hertzian contact model. The average moduli were 4–8 GPa for the PS-silica composite particles which were much lower than the that of the pure silica (72–75 GPa) and closed to that of the PS cores (2.1 ± 0.5 GPa). The elastic moduli of the PS-silica hybrids increased with increasing of silica shell thickness, suggesting that the elasticity of the PS-silica composite particles might be attributed to the PS cores and the silica shell was stiffening the polymer cores. These results provide a basis for exploring the mechanical properties of core–shell PS-silica hybrids in the application of novel abrasives for chemical mechanical polishing.     

Synthesis of stable hollow silica nanospheres

Hollow silica nanospheres with their size distribution ranging from 350 nm to 450 nm are synthesized by using polystyrene (PS) templates in the present study. On the basis of PS templates, silica, the hydrolyzate of TEOS(tetraethyl orthosilicate) under moist alkaline condition at ambient temperatures and atmospheric pressures, it is set to be coated on the surface of the PS spheres. Since the size of PS sphere core can be easily controlled, it is expected to serve various needs of different sized hollow silica nanospheres in industrial applications. It is proposed that the PS cores be removed by either thermal pyrogenation or solvent dissolved. Morphology of the hollow silica nanospheres is characterized by scanning electron microscopy (SEM).     

Sodium silicate route: fabricating high monodisperse hollow silica spheres by a facile method

This paper exhibits good example of high well-defined hollow silica spheres by using a low-cost sodium silicate precursor via a facile method. The N₂ adsorption isotherm shows that this hollow structure leads to a high Brunauer?CEmmett?CTeller specific area of ca. 217.755?m²?g^?1. Transmission electron microscopy and scanning electron microscopy images indicate that prepared hollow silica spheres have uniform morphology and narrow size distribution. Particle size analyzer measurement (polydispersity?=?0.005; GSD?=?1.073) also further confirms the fact that hollow silica spheres with high monodispersity have been successfully developed as expected.     

Preparation of hollow mesoporous silica spheres by a sol–gel/emulsion approach

Hollow mesoporous silica spheres were synthesized by a sol–gel/emulsion (oil-in-water/ethanol) approach, in which cetyltrimethylammonium bromide (CTAB) surfactant was employed to stabilize and direct the hydrolysis of oil droplets of tetraethoxysilane (TEOS). The diameters of the hollow spheres can be tuned in the range from 210 to 720 nm by varying the ratio of ethanol-to-water and their shell thickness can be mediated by changing the concentration of CTAB used in the system. BET surface areas of the hollow silica spheres are determined to be in the range of 924–1766 m² g^?1 and their pore sizes are around 3.10 nm as determined by BJH method.     

Preparation of dandelion-type silica spheres and their application as catalyst supports

Dandelion-type silica spheres with a dendrimer-like porous structure were prepared by adding pore modifiers into aqueous synthetic mixtures of tetraethylorthosilicate (TEOS), hexadecyltrimethylammonium bromide (CTAB), ammonium hydroxide, and acetone. The formation of silica spheres and their porous characteristics were investigated using various techniques, including electron microscopy, nitrogen adsorption, and thermogravimetric analysis. Benzyl acetate (BENA) was very effective in the formation of a dendrimer-like porous structure. However, the composition of TEOS, CTAB, acetone, and BENA strongly influenced the size and shape of the silica spheres and their porous structure. The synthetic mixture of 1 TEOS: 0.22 CTAB: 1.9 BENA: 0.32 NH₄OH: 36 acetone: 236 H₂O produced dandelion-type silica spheres with diameters of ~300 nm. The phosphazenium hydroxide (PzOH) catalyst supported on the dandelion-type silica spheres prepared by adding BENA showed high catalytic performance in the transesterification of soybean oil with methanol due to its high feasibility for rapid access of large triglyceride molecules into the basic PzOH moieties incorporated in the pores.     

Composite materials based on polydimethylsiloxane and in situ generated silica by using the sol–gel technique

A polydimethylsiloxane-α,ω-diol with molar mass M_n = 43,000 has been synthesized by cationic polymerization of octamethylcyclotetrasiloxane and reinforced with silica. Two pathways were used for incorporation of silica in the polymeric matrix: ex situ by mechanical blending of a pretreated fumed silica and in situ by adding tetraethyl-orthosilicate (TEOS) as silica precursor in the polymer matrix followed by their hydrolysis and condensation (sol–gel technique). The procedure occurred in the absence of solvent. Composites with different contents of silica were prepared and investigated by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The results were compared to those obtained on a model network based on the same polysiloxane without silica. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Hexagonal Mesoporous Silica with Noodle-Like Shape

Hexagonal mesoporous silica (HMS) was prepared at ambient temperature by using dodecylamine (DDA) as the surfactant and tetraethyl orthosilicate (TEOS) as the silica precursor. The HMS materials were characterized by X-ray powder diffraction, N₂ adsorption/desorption, scanning electron microscopy and transmission electron microscopy. The samples prepared at various addition rates of TEOS and various alcohol/water (R/H) ratios were investigated. As the addition rate of TEOS decreased, the size of HMS particles increased and the textural porosity decreased. Non-alcoholic solution was required to prepare non-spherical particles. The HMS with noodle-like structures was prepared in the absence of alcoholic solvent. These noodle-like particles were about 0.1m in diameter and about submicrometer to several micrometers in length.     

Preparation of poly-(NIPAM) grafted hybrid silica particles with hollow structure in emulsion

The successful preparation of hybrid silica particles was studied using 3-(trimethoxysilyl)propyl methacrylate (TMPM) and poly(N-isopropylacrylamide) (poly-(NIPAM)) in W/O (water-in-oil) emulsion. In general, hollow silica materials were made using a template method that was needed a process of template removal. However, in this paper, hollow particles grafted with organic materials were synthesized directly and the structure of particles was controlled by adjusting ratio of reactants. A large amount of thermo-responsive polymer such as poly-(NIAPM) can be formed at the surface of hollow silica particles because silica substrates have many methacrylate functional groups at surfaces. Detailed characterization of the hybrid silica particles was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to elucidate the morphologies and properties of the hybrid silica particles.     

Control of hydroxyl group content in silica particle synthesized by the sol-precipitation process

This study investigated the control of hydroxyl groups, one of key factors determining the surface properties of silica particles synthesized by the sol-precipitation of tetraethyl orthosilicate (TEOS). Thus, a thermal gravity analysis (TGA) was used to facilitate quantitative measurements of the hydroxyl groups on the silica particles, while BET and FT-IR were used to analyze the specific surface area and functional silane groups on the silica particles, respectively. In the sol-precipitation process, silanes that include various hydroxyl groups are formed as intermediates based on the hydrolysis and condensation of TEOS. Thus, NH₃, as a basic catalyst initiating the nucleophilic substitution of TEOS, was found to accelerate the hydrolysis and increase the hydroxyl group content on the silica particles. Plus, the hydroxyl group content was also increased when increasing the concentrations of TEOS and water as the hydrolysis reactants. However, the hydroxyl group content was reduced when increasing the temperature, due to the promotion of condensation. Based on the weight loss of the particles according to the thermal analysis, the hydroxyl group content on the silica particles varied from 5.6–42.7 OH/nm² under the above reaction conditions.     

免模板法制备锐钛型TiO2空心球

以草酸钛钾为钛源,利用一步免模板法在水热条件下制备出二氧化钛空心球,其形成机理建立在由里及外的“Ostwald ripening”理论上.在不同的反应时间下研究了二氧化钛从亚稳相逐渐向稳定相的锐钛型二氧化钛空心球转变的过程.结合SEM的观察发现二氧化钛由光滑的固态粒子逐渐转变为表面为纳米棒状的二氧化钛空心球,TEM证实了所制备的空心球的直径约为1微米,单晶衍射图案（SAED）表明棒状晶体沿[001]面生长.     

气溶胶辅助自组装制备中空球形二氧化硅材料的机理及应用

以正硅酸乙酯（TEOS）和甲基三乙氧基硅烷（MTES）为混合硅源,不同配比条件下采用气溶胶辅助自组装技术制备高比表面积的中空介孔二氧化硅纳米颗粒（HMSNs）,并应用于原花青素（PC）的负载,以期提高其生物利用度。利用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、红外图谱（FTIR）和粒径分析（DLS）等对载体颗粒的形成过程、结构特性以及负载性能进行探究,基于BET分析方法计算HMSNs的比表面积,并对孔径分布进行分析。结果表明,前体溶液水解的活性中间体缩合形成二氧化硅网络结构,同时雾化后的气溶胶液滴在径向浓度梯度自组装成球形结构,水解-缩合与自组装过程协同作用促进了分散性良好的介孔二氧化硅（MSNs）的形成。经退火处理、纯化操作去除模板剂NaCl和表面活性剂十六烷基三甲基溴化铵（CTAB）,最终获得具有中空结构的HMSNs。当TEOS/MTES的摩尔比为60/40时,HMSNs具有极大的比表面积（1083m²/g）和较大的孔容积（0.37cm³/g）,其孔径主要分布在2~4nm之间,PC在HMSNs上的负载量可达30.7mg/g。     

Efficient preparation of polymer‐based hollow spheres for the photocatalytic degradation of methylene blue

Titanium dioxide hollow spheres were synthesized by utilizing polystyrene‐co‐methacrylic acid latex particles coated with titanium isopropoxide. Hollow spheres prepared with different ruthenium salt concentrations showed considerable levels of organic pollutant degradation upon UV irradiation. In the present study, methylene blue (MB) was selected as a model for these pollutants. Thus its degradation indicated the activity of the hollow spheres as photocatalysts for decomposing the pollutants. The efficiencies of these photocatalysts were determined in terms of chemical oxygen demand removal. During these experiments, several conditions were monitored such as the effects of pH, ruthenium salt concentration, and initial MB load concentration. The prepared particles were characterized by using transmission electron microscopy and scanning electron microscopy. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Silica coated ferrite nanoparticles: Influence of citrate functionalization procedure on final particle morphology

In this paper, magnetic nanoparticles (Fe₃O₄ and NiFe₂O₄) were coated with a biocompatible silica shell via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the Stöber process. Magnetic nanoparticles, prepared by chemical co-precipitation from iron and nickel salts, were functionalized with citric acid, in order to provide their deagglomeration and to enable their coating with silica. The parameters of the functionalization procedure were varied (concentration–pH and type of treatment), in order to examine if and how this particular step of preparation affects the final morphology of the core-shell particles. Transmission electron microscopy, zeta potential and particle size measurements revealed that the morphology and the size of obtained core shell particles depend significantly on the core particle size, and thus on the parameters of the functionalization step.     

Synthesis of Organic Dye-Impregnated Silica Shell-Coated Iron Oxide Nanoparticles by a New Method

A new method for preparing magnetic iron oxide nanoparticles coated by organic dye-doped silica shell was developed in this article. Iron oxide nanoparticles were first coated with dye-impregnated silica shell by the hydrolysis of hexadecyltrimethoxysilane (HTMOS) which produced a hydrophobic core for the entrapment of organic dye molecules. Then, the particles were coated with a hydrophilic shell by the hydrolysis of tetraethylorthosilicate (TEOS), which enabled water dispersal of the resulting nanoparticles. The final product was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and vibration sample magnetometer. All the characterization results proved the final samples possessed magnetic and fluorescent properties simultaneously. And this new multifunctional nanomaterial possessed high photostability and minimal dye leakage.     

Synthesis and characterization of nanosilica/waterborne polyurethane end‐capped by alkoxysilane via a sol‐gel process

A novel method was used to synthesis nanosilica/waterborne polyurethane (WPU) hybrids by in situ hydrolysis and condensation of tetraethyl orthosilicate (TEOS) and/or 3‐aminopropyltriethoxylsilane bonding at the end of the WPU molecular chain. The hybrid was characterized by scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS). The results showed that the nanosilica/WPU hybrids with well‐dispersed nanosilica particles were synthesized, in which the particles had typical diameters of about 50 nm. In addition, XPS and FTIR analyses demonstrated that chemical interaction occurred between WPU and silica. The effects of TEOS on surface wettability, water resistance, mechanical strength, and thermal properties of the hybrid were also evaluated by contact angle measurements, water absorption tests, mechanical tests, and differential scanning calorimetry, respectively. An increase in advancing contact angles, water resistance, and tensile strength, as well as decrease in elongation at break and glass transition temperature, were obtained with the addition of TEOS. Water absorption decreased from 17.3 to 5.5%. The tensile strength increased to a maximum of 29.7 MPa, an increase of about 34%. Elongations at break of the hybrids decreased 191%. These results were attributed to the effects of the nanosilica and the chemical interaction between WPU and silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of CuS hollow spheres

CuS hollow spheres have been successfully prepared using styrene–acrylic acid copolymer (PSA) latex particles as template. The process involved the deposition of inorganic coatings on the surface of PSA latex particles and subsequent removal of the latex particles by dispersing in toluene. The synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and UV–vis absorption spectroscopy. The results showed the wall thickness of CuS shell to be about 20 nm and the pore diameter to be about 150 nm. The possible formation mechanism of CuS hollow spheres has been proposed.     

Hollow microspheres of NiO as anode materials for lithium-ion batteries

NiO hollow spheres are prepared by heating the NiCl₂/resorcinol-formaldehyde (RF) gel in argon at 700 °C for 2 h, and subsequently in oxygen at 700 °C for 2 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to characterize the structure and morphology of the as-prepared NiO hollow spheres. These hollow spheres have a diameter of about 2 μm, which are composed of NiO particles of about 200 nm. The electrochemical properties of these NiO hollow spheres are investigated to determine the reversible capacity and cycling performance as anode materials for lithium-ion batteries, and the advantages of their hollow spherical morphology to the electrochemical performance are discussed.     

Effects of water on the preparation,morphology, and properties of polyimide/silica nanocomposite films prepared by sol–gel process

Polyimide/silica (PI/SiO₂) nanocomposite films with 10 wt % of silica content were prepared by sol–gel process under the conditions with and without additional water. The presence of additional water has great effect on the silica particle size and thus on the properties of the prepared PI/SiO₂ films. The results indicated that with additional water, the silica particles formed before the imidization of poly(amic acid) (PAA) and aggregated with the increasing of temperature and degree of the proceeding imidization process. For the nonaqueous process, the hydrolysis condensation reaction of tetraethoxysilane (TEOS) did not occur until the imidization of PAA took place, and no silica particles were found in the unimidized PAA films. The hydrolysis–condensation reaction of TEOS was initiated simultaneously by the trace water released from the imidization reaction, the self‐catalysis mechanism of the approach provide a means of achieving uniformly dispersed silica particles formed in the PI matrix with particle size in the range of 30–70 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1579–1586, 2007