Size-controllable synthesis of monodispersed colloidal silica nanoparticles via hydrolysis of elemental silicon

A new method is presented for preparing monodisperse and uniform-size silica nanoparticles using a two-stage hydrolysis of silicon powder in aqueous medium. The influence of synthesis conditions including solution composition and temperature on the formation of silica nanoparticles were systematically investigated. The structure and morphology of the silica particles were characterized via transmission electron microscopy (TEM) and dynamic light scattering (DLS). Various-sized particles in the range 10–100 nm were synthesized. The size of the nanoparticles can be precisely controlled by using a facile regrowth procedure in the same reaction media.     

Hierarchically Structured Porous Films of Silica Hollow Spheres via Layer‐by‐Layer Assembly and Their Superhydrophilic and Antifogging Properties

Raspberrylike organic/inorganic composite spheres are prepared by stepwise electrostatic assembly of polyelectrolytes and silica nanoparticles onto monodisperse polystyrene spheres. Hierarchically structured porous films of silica hollow spheres are fabricated from these composite spheres by layer‐by‐layer assembly with polyelectrolytes followed by calcination. The morphologies of the raspberrylike organic/inorganic composite spheres and the derived hierarchically structured porous films are observed by scanning and transmission electron microscopy. The surface properties of these films are investigated by measuring their water contact angles, water‐spreading speed, and antifogging properties. The results show that such hierarchically structured porous films of silica hollow spheres have unique superhydrophilic and antifogging properties. Finally, the formation mechanism of these nanostructures and property–structure relationships are discussed in detail on the basis of experimental observations.     

Synthesis and utilization of monodisperse hollow polymeric particles in photonic crystals

We developed a process to fabricate 150-700 nm monodisperse polymer particles with 100-500 nm hollow cores. These hollow particles were fabricated via dispersion polymerization to synthesize a polymer shell around monodisperse SiO(2) particles. The SiO(2) cores were then removed by HF etching to produce monodisperse hollow polymeric particle shells. The hollow core size and the polymer shell thickness, can be easily varied over significant size ranges. These hollow polymeric particles are sufficiently monodisperse that upon centrifugation from ethanol they form well-ordered close-packed colloidal crystals that diffract light. After the surfaces are functionalized with sulfonates, these particles self-assemble into crystalline colloidal arrays in deionized water. This synthetic method can also be used to create monodisperse particles with complex and unusual morphologies. For example, we synthesized hollow particles containing two concentric-independent, spherical polymer shells, and hollow silica particles which contain a central spherical silica core. In addition, these hollow spheres can be used as template microreactors. For example, we were able to fabricate monodisperse polymer spheres containing high concentrations of magnetic nanospheres formed by direct precipitation within the hollow cores.     

由硅溶胶生长单分散颗粒的研究

针对现行单分散二氧化硅颗粒制备方法的粒径预见性差、步骤繁琐、收率低等问题，研究了一种用硅溶胶作为种子，在氨、水和乙醇的混合溶液中通过水解正硅酸乙酯（ＴＥＯＳ）生长出单分散颗粒的简便方法。该方法仅在初始的悬浮液中滴加ＴＥＯＳ即可使种子正常生长，无须补充氨水以修正体系浓度的变化。最终的分散相浓度可达１０％（质量分数）。可选择生长的粒径范围在１微米以内并可精确控制。所得颗粒粒径分布偏差于Ｓｔｏｂｅｒ方法     

A novel method for the fabrication of monodisperse hollow silica spheres

In this paper, we report a novel method for the fabrication of small monodisperse hollow silica spheres. In this approach, when silica shells were coated on polystyrene particles by the sol-gel method, the polystyrene cores were dissolved subsequently, even synchronously, in the same medium to form monodisperse hollow spheres. Neither additional dissolution nor a calcination process was needed to remove the polystyrene cores. Transmission electron microscopy, scanning electron microscopy, and porosity measurements were used to characterize the monodisperse hollow silica spheres.     

Close-packed colloidal crystalline arrays composed of silica spheres coated with titania

Titania coated monodisperse silica spheres have been synthesized and fabricated as a close-packed colloidal crystalline array. We have demonstrated that the coated colloidal sphere can be used to control the peak position of the optical stop band through variation of the coating thickness. The titania coated silica spheres were prepared by the layer-by-layer assembly coating process, which reciprocally laminates the cationic polyelectrolyte and the anionic titania nanosheets on a monodisperse silica spheres, and were sintered to change the titania nanosheets to anatase. The Bragg diffraction peak of the colloidal crystalline array shifted to the long wavelength region with an increase of thickness of the titania layer. Angle-resolved reflection spectra measurements clarified that the red shift was caused by increasing of the refractive index with increase of the thickness of the layer. The current work suggests new possibilities for the creation of advanced colloidal crystalline arrays with tunable optical properties from tailored colloidal spheres.     

A facile method for the preparation of monodisperse hollow silica spheres with controlled shell thickness

This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010     

Magnetic fluorescent delivery vehicle using uniform mesoporous silica spheres embedded with monodisperse magnetic and semiconductor nanocrystals

We synthesized uniform pore-sized mesoporous silica spheres embedded with magnetite nanocrystal and quantum dots. The magnetic separation, luminescent detection, and controlled release of drugs were demonstrated using the uniform mesoporous silica spheres embedded with monodisperse nanocrystals.     

一种制备单分散SiO2空心微球的新方法

在乙醇/氨水介质中, 分别以分散聚合和无皂乳液聚合方法制得的不同粒径聚苯乙烯(PS)微球为模板, 以正硅酸乙酯(TEOS)为前驱体, 通过控制介质中氨水的初始体积, 一步法制得了不同粒径的单分散SiO2空心微球. 整个过程无需添加其它溶剂溶解或高温煅烧的方法来除去模板微球. 对SiO2空心微球进行测试表征, 提出了SiO2空心微球的可能形成机制.     

Synthesis of aqueous CdTe quantum dots embedded silica nanoparticles and their applications as fluorescence probes

This paper presents the synthesis of aqueous CdTe QDs embedded silica nanoparticles by reverse microemulsion method and their applications as fluorescence probes in bioassay and cell imaging. With the aim of embedding more CdTe QDs in silica spheres, we use poly(dimethyldiallyl ammonium chloride) to balance the electrostatic repulsion between CdTe QDs and silica intermediates. By modifying the surface of CdTe/SiO₂ composite nanoparticles with amino and methylphosphonate groups, biologically functionalized and monodisperse CdTe/SiO₂ composite nanoparticles can be obtained. In this work, CdTe/SiO₂ composite nanoparticles are conjugated with biotin-labeled mouse IgG via covalent binding. The biotin-labeled mouse IgG on the CdTe/SiO₂ composite nanoparticles surface can recognize FITC-labeled avidin and avidin on the surface of polystyrene microspheres by protein-protein binding. Finally, the CdTe/SiO₂ composite nanoparticles with secondary antibody are used to label the MG63 osteosarcoma cell with primary antibody successfully, which demonstrates that the application of CdTe/SiO₂ composite nanoparticles as fluorescent probes in bioassay and fluorescence imaging is feasible.     

Architecture of micron-scale hollow spheres composed of silica nanoparticles and approach to luminescent spheres

Micron-scale hollow spheres were successfully constructed with silica nanoparticles by templating of polymer spheres. Subsequently, the use of 3-aminopropyltriethoxysilane (APTES) introduces carbon and oxygen defects in the silica nanoparticles resulting from calcination of the aminopropyl group. In this approach, the template of micron-scale polymer spheres was prepared from dispersion polymerization. Subsequent St?ber process results in the formation of a silica layer attached to the polymer sphere surfaces. After calcination, the obtained micron-scale hollow silica spheres were then studied on the relationship between the particle diameter and the surface morphology. The luminescence of hollow spheres was prepared through using APTES in St?ber process, and which of related the appearance of luminescence to the APTES concentration and calcination temperature. The results of this study can provide useful information for the structure of micron-scale hollow spheres and their application to luminescent materials.     

Thermo-sensitive colloidal crystals of silica spheres in the presence of large spheres with poly (N-isopropyl acrylamide) shells

Thermo-sensitive colloidal crystals are prepared simply by mixing colloidal silica spheres and large thermo-sensitive gel spheres. The thermo-reversible change in the lattice spacing of colloidal crystals of monodisperse silica spheres (CS82, 103 nm in diameter) depends on the size of the admixed temperature-sensitive gel spheres. For spheres with sizes less and greater than that of the silica spheres, the lattice spacing upon temperature increase above the lower critical solution temperature of poly(N-isopropyl acrylamide) decreases (cf. Okubo et al. Langmuir 18:6783, 2002) and increases, respectively. A mechanism, which is able to explain these experimental findings, is proposed. Moreover, crystal growth rates and the rigidities of the thermo-sensitive colloidal crystals are studied.     

Anisotropic magnetic porous assemblies of oxide nanoparticles interconnected via silica bridges for catalytic application

We report the microfluidic chip-based assembly of colloidal silanol-functionalized silica nanoparticles using monodisperse water-in-oil droplets as templates. The nanoparticles are linked via silica bridges, thereby forming superstructures that range from doublets to porous spherical or rod-like micro-objects. Adding magnetite nanoparticles to the colloid generates micro-objects that can be magnetically manipulated. We functionalized such magnetic porous assemblies with horseradish peroxidase and demonstrate the catalytic binding of fluorescent dye-labeled tyramide over the complete effective surface of the superstructure. Such nanoparticle assemblies permit easy manipulation and recovery after a heterogeneous catalytic process while providing a large surface similar to that of the individual nanoparticles.     

Reversible control of light reflection of a colloidal crystal film fabricated from monodisperse mesoporous silica spheres

In this letter, we report a novel method for controlling the light reflection of a colloidal crystal. Highly monodisperse mesoporous silica spheres have been successfully organized into a hexagonally close-packed colloidal crystal film. Just by introducing water vapor into the fabricated colloidal film, the structural color and reflection spectra were changed dramatically because of water vapor adsorption occurring in the mesoporous channels. This phenomenon can be observed reversibly over five cycles. We are convinced that this is the first report on controlling the light reflection of a colloidal crystal film dynamically by taking advantage of adsorption properties inherent to mesoporous silica spheres.     

One-step synthesis of highly monodisperse hybrid silica spheres in aqueous solution

An effective and reproducible method of preparing highly monodisperse organic-inorganic hybrid silica spheres was studied. One process, one precursor (organosilane) and one solvent (water) were used in our experiments. The size of hybrid silica spheres could be adjusted from 360 to 770 nm with relative standard deviation below 2% by controlling the concentration of the organosilane precursor and the ammonia catalyst. The increasing of the precursor concentration increases the particle size while the catalyst concentration has a reverse effect on the particle size. The concept of homogeneous nucleation and growth processes are introduced to explain the formation mechanism and the effect of reaction conditions. The scanning electron microscopy (SEM) images illustrate the copiousness in quantity and the uniformity in size/shape of the particles that could be routinely accomplished in this synthesis. Fourier transform infrared (FT-IR) and (29)Si nuclear magnetic resonance (NMR) spectra confirm the structure of vinyl hybrid silica spheres, where the vinyl group (-CH=CH(2)) exists and connects to the silicon atom. This method has also been extended to design and prepare other organic-inorganic hybrid materials especially in monodisperse surface-modified silica spheres.     

单分散介孔氧化硅纳米颗粒的制备及其在生物材料方面的应用

单分散介孔氧化硅纳米颗粒由于其自身的优点,在当前许多领域有着广泛的应用前景。本文综述了近十几年来单分散介孔氧化硅纳米颗粒的制备方法以及在生物材料方面的应用。在制备方法方面,根据其制备机理分为稀溶液法、微乳法、模板剂法以及向反应体系中加入不同的添加剂等方法,制备出分散性好、不同形态、孔径尺寸可调的介孔氧化硅纳米颗粒。在生物材料的应用方面,主要介绍了其在药物与生物活性分子的负载与控制释放、生物大分子的固载与分离、生物标记与临床诊断等方面的应用。     

Synthesis and antibacterial property of hollow SiO2/Ag nanocomposite spheres

This paper presents a novel and facile method to fabricate hollow silica/sliver (SiO(2)/Ag) nanocomposite spheres. In this approach, the monodisperse hollow SiO(2) colloids bearing quantenary ammonium groups were prepared by dispersion polymerization combined sol-gel process and used as templates. The Ag(+) ions were first adsorbed onto the surfaces of the hollow SiO(2) beads via electrostatic interaction and then in situ reduced by the deprotonated silanol groups of the hollow SiO(2) beads, no extra reducing agents or catalysts were added during the reduction process. TEM, SEM and EDX analyses indicated that Ag nanoparticles were successfully deposited onto the surfaces of hollow SiO(2) beads. Some influencing parameters, such as the amount of quantenary ammonium groups in the inner wall of hollow SiO(2) colloids, Ag(+) ions concentration and reaction temperature, on the deposition of Ag nanoparticles onto SiO(2) colloids were investigated. Preliminary antibacterial tests indicated that these hollow nanocomposite spheres showed excellent antibacterial ability.     

Preparation and characterization of thermosensitive polymers grafted onto silica-coated iron oxide nanoparticles

In this study, multifunctional nanoparticles containing thermosensitive polymers grafted onto the surfaces of 6-nm monodisperse Fe(3)O(4) magnetic nanoparticles coated by silica were synthesized using reverse microemulsions and free radical polymerization. The magnetic properties of SiO(2)/Fe(3)O(4) nanoparticles show superparamagnetic behavior. Thermosensitive PNIPAM (poly(N-isopropylacrylamide)) was then grafted onto the surfaces of SiO(2)/Fe(3)O(4) nanoparticles, generating thermosensitive and magnetic properties of nanocomposites. The sizes of fabricated nanoparticles with core-shell structure are controlled at about 30 nm and each nanoparticle contains only one monodisperse Fe(3)O(4) core. For thermosensitivity analysis, the phase transition temperatures of multifunctional nanoparticles measured using DSC was at around 34-36 degrees C. The magnetic characteristics of these multifunctional nanoparticles were also superparamagnetic.     

Synthesis of photoluminescent carbogenic dots using mesoporous silica spheres as nanoreactors

A novel and facile approach for preparing hydrophilic carbogenic dots (CDs) has been developed with mesoporous silica spheres as nanoreactors by using an impregnation method. The resulting highly efficient photoluminescent CDs without any further treatment are monodisperse, photostable and of low toxicity, and show excellent luminescence properties.     

由硅酸酯合成单分散二氧化硅中碳的化学形态

单分散二氧化硅是指尺寸分布十分狭窄的二氧化硅颗粒．单分散颗粒在科学研究及工业应用中得到了广泛的应用［1］．单分散二氧化硅由正硅酸有机酯在氨催化下于醇溶液中水解缩合得到．硅酸酯的水解和缩合反应可用如下反应描述．总的反应式为：nSi（OR）4＋2nH20→nSiO2＋4nROH1956年Kolbe［2］发现正硅酸乙酯（TEOS）在碱催化下于乙醇溶剂中水解反应有时会形成均一颗粒二氧化硅以来，许多学者对这一反应体系进行了较为广泛的研究，提出了双分子缩合成核机理、单分子叠加生长机理、表面反应控制生长机理、扩散控制生长机理和微晶核团聚生…