Size Of Silica Spheres Research Articles

Continuous synthesis of monodisperse silica microspheres over 1 μm size

This study presents a robust and scalable method for synthesizing continuously the silica microspheres via the Stober method. Owing to the superb mixing accessible with gas-liquid segmented flow in coiled microtube, satisfactory morphology and mono-dispersity of silica spheres was obtained. The continuous method was firstly optimized through investigating the effects of various operation parameters on the morphology, particle size, size distribution and chemical structure of silica spheres. Without the surfactant, the size of silica spheres was limited < 850 nm due to the partial blockage of microchannel when synthesizing larger silica spheres. The addition of surfactant migrated the clogging issue, enabling the reliable synthesis of microspheres with diameters over 1 μm within a four times shorter residence time (30 min). Moreover, the mono-dispersity of silica microspheres could be further improved by increasing the gas/liquid ratio in segmented flow due to the more intensified mixing in liquid segments, as verified in visual flow field investigation.

Feasibility of Macroporous CeO2 Photocatalysts for Removal of Lead Ions from Water

Removal of lead ions from water was conducted by a coupling approach of adsorption and photoelectrodeposition over a macroporous CeO2 photocatalyst loaded with ZnO. The photocatalyst was prepared by the hard template method and the impregnation method. The various size of silica spheres (0.05-0.4 µm) were used as a template for the photocatalyst, and the highest BET surface area (73.8 m2/g) was given in the sample prepared with the smallest silica sphere (0.05 µm). In the removal of lead ions, the porous sample showed a large amount of removal of lead ions. In addition, the ZnO loaded catalysts showed a larger amount of removal for lead ions than an unloaded catalyst under the UV light irradiation. In the reaction, since zinc ions were simultaneously dissolved to the solution, it was suggested that this reaction was the ion-exchange reaction between lead ions and zinc ions and was promoted by the UV light irradiation.

Fabrication and simulation of inverse poly(ferrocenylmethylvinylsilane)/silica opal structures and their optical properties

Photonic crystal structures were fabricated by the formation of periodic arrays of poly(ferrocenylsilane) (PFS) derivations and silica spheres. Here, we present the primary steps of a simulation-driven design of photonic crystal based on PFS as a potentially stimuli-responsive polymer, which can present predesigned color when subjected to the visible light. The poly(ferrocenylmethylvinylsilane) (PFMVS) was synthesized by photolytic anionic ring opening polymerization of methylvinylsila[1]ferrocenophane monomer under controlled condition and monodisperse silica spheres were synthesized by the Stober process. Bare silica opal was prepared by the convective self-assembly process of different sizes of silica spheres on glass substrate followed by infiltration of PFMVS to obtain PFMVS/silica opal and finally removal of the silica spheres by acid washing to attain the inverse PFMVS opal. The particle size of silica spheres along with the refractive indices contrast of different components forming photonic crystal played an important role in obtaining the maximum reflectance wavelength of the desired opal. Photonic crystal prepared by 210, 270, and 330 nm monodisperse silica spheres represents the blue, green, and red color, respectively. Simulation analyses of these opal structures were investigated by using the plane-wave expansion (PWE) method to assess the photonic crystal behavior versus the visible light. According to the simulation results, the photonic crystal structure was designed. The experimental reflectance outcomes of the three opal structures were in good agreement with the simulation analysis.

A Simple Approach to Fabricate CdS-SiO 2 Hybrid Microspheres by Producing CdS Nanoparticles on the Surface of Thiolated SiO 2 Microspheres

We have developed a simple synthetic method to prepare the hybrid microspheres of CdS nanoparticles on the surface of silica microspheres modified by(3-mercaptopropyl)trimethoxysilane(MPS). The—SH groups of MPS can bind with the Cd2+ ions on the surface of SiO2. When thioacetamide releases H2S, the nanosized CdS particles(1–6 nm) will successfully be generated on the silica surface under the experimental conditions. The size of the CdS nanoparticles was found to be related to the concentration of Cd2+ feed and the size of silica spheres, the higher the concentration of Cd2+ and the larger of silica microspheres, the bigger the size of CdS nanoparticles. Techniques including UV, PL, TEM and XPS were used to characterize the CdS-SiO2 hybrid microspheres.

Synthesis of nanostructured polymer materials with different morphologies: Nanoporous ordered networks and hollow capsules

Nanostructured polymer materials with interesting morphological variation, which include three dimensionally interconnected uniform nanoporous network arrays (volume- and surface-templated ordered arrays) and hollow core spheres were synthesized by inducing different polymerization process of phenol and formaldehyde as a precursor over silica templates (ordered silica colloidal crystals or individual silica particles). The pore sizes of the resulting nanostructured polymer materials can be easily controlled by monitoring the sizes of silica spheres, while their morphologies were modulated by controlling the initiation sites of the acid-catalyzed condensation reaction of the same polymer precursor and by modifying silica templates.

Formation and structure of artificial opal based on the colloidal silica sphere

Highly monodispersed colloidal silica spheres in submicrometer sizes were synthesized by a chemical method.The sizes of silica spheres measured by transmission electron microscopy range from 200 to 600 nm in diameter, and its distribution standard deviation is less than 5%.Scanning Electron Microscopy images show that using selfcrystallization of the silica spheres, we have successfully obtained artificial opals with the three dimensional closepacked, facecentered cubic (fcc) silica matrixes. Reflection spectra study reveals that artificial opals show (111) directional photonic bandgap features.

More direct evidence of the fcc arrangement for artificial opal

We present a scanning electron microscopy (SEM) investigation of artificial opals prepared by the sedimentation of suspension with sub-micrometer silica spheres. An analysis of the SEM images confirms that the fcc stacking is the most stable phase for the artificial crystals. Optical diffraction and transmission spectrum indicate a good alignment of the top (111) crystal plane. We also show that defects and dislocations of opal crystals are caused mainly by the irregular spheres. Slow sedimentation and uniform size of silica spheres may be the key factors for growing high quality opal crystals.

Sedimentation of monodisperse and bidisperse hard‐sphere colloidal suspensions

AbstractThe effect of concentration on the sedimentation rate of uncharged rigid spheres was investigated. Three submicron sizes of silica spheres were prepared according to the method of Stöber (1968). The particles were sterically stabilized by chemisorption of stearyl alcohol at their surface by the method developed by van Helden (1981). The sterically stabilized silica particles dispersed in cyclohexane are known to behave as hard spheres. Monodisperse gravity sedimentation experiments were carried out for the various particle species over a wide concentration range of ϕ = 0.003 to ϕ = 0.37, where ϕ is the particle volume fraction in cyclohexane. The data for dilute suspensions (ϕ &lt; 0.03) were found to be well described by Batchelor's equation: U/U0 = 1–6.55ϕ, where U is the sedimentation velocity and U0 is the Stokes velocity of a sphere in isolation. The data over the entire concentration range (0&lt;ϕ&lt;0.37) were found to be well described by the equation: U/U0 = (1–ϕ)6.55.Bidisperse sedimentation experiments were also carried out, and the dilute data were found to be well represented by Batchelor's 1982 theory for polydisperse suspensions. The high concentration data were analyzed in terms of a model that does not distinguish between interactions of like and unlike particles.