Monodispersed silica spheres

Stober, W Fink, A. and Bohn, E. (1968) Controlled growth of monodispersed silica spheres in the micron size range. Journal of... 

It is difficult to obtain meaningful results on colloidal interactions unless the samples have low polydispersity. Studies of colloidal interactions between whole casein micelles can be affected by the polydispersity of native casein micelles. (Stothart,1987b). To circumvent the problem of polydispersity, the food system can be deposited on monodisperse silica spheres (Rouw and de Kruif,1989). 

Another important method for photonic crystal fabrication employs colloidal particle self-assembly. A colloidal system consists of two separate phases a dispersed phase and a continuous phase (dispersion medium). The dispersed phase particles are small solid nanoparticles with a typical size of 1-1000 nanometers. Colloidal crystals are three-dimensional periodic lattices assembled from monodispersed spherical colloids. The opals are a natural example of colloidal photonic crystals that diffract light in the visible and near-infrared (IR) spectral regions due to periodic modulation of the refractive index between the ordered monodispersed silica spheres and the surrounding matrix. 

The monodisperse silica spheres were obtained by the controlled hydrolysis of TEOS in ethanol in presence of liquid ammonia [4]. The final size of the spheres depends on the concentration in liquid ammonia, the hydrolysis ratio and the temperature. Slabs (diameter 25 mm and thickness 2 mm) were obtained by pressing the monodisperse silica sphere powders at 300 MPa and 300°C with Mowioll as binding agent. The thermal treatment destroys the organic radicals present on the surface of the spheres. Samples with the following particle diameters were prepared SI = 8 nm, S2 = 16 nm, S3 = 25 nm, S4 = 40 nm, S5 = 64 nm, S6 = 102 nm, S7 = 206 nm. 

Stober W, Fink A and Bohn E 1968 Controlled growth of monodisperse silica spheres in the micron size range J. Colloid Interface Sci. 26 62-9... 

Crystalline colloidal arrays (CCA) are mesoscopically periodic fluid materials which efficiently diffract light meeting the Bragg condtion (/-. These materials consist of arrays of colloidal particles which self assemble in solution into BCC or FCC crystalline arrays (7,5) (Figure 1) with lattice constants in the mesoscale size range (50 to 500 nm). Just as atomic crystals diffract x-rays that meet the Bragg condition, CCA diffract UV, visible, and near IR light (2-4) the diffraction phenomena resemble that of opals, which are close-packed arrays of monodisperse silica spheres (6). 

H. Giesche, K.K. Unger, U. Muller, and U. Esser Hysteresis in nitrogen sorption and mercury porosimetry on mesoporous model adsorbents made of aggregated monodisperse silica spheres, CoUoids Surf., 37 (1989) 93-113... 

A. van Blaaderen and A. Vrij Synthesis and characterization of colloid dispersions of fluorescent, monodispersed silica spheres, Langmuir, 8 (1992) 2921-2931 J.D. Wells, L.K. Koopal, and A. de Keizer Monodisperse, nonporous, spherical silica particles, Colloids Surf. A Physicochem. Eng. Asp., 166 (2000) 171-176 Howard A. Ketelson, Robert Pelton, and Michael A. Brook Surface and colloidal properties of hydrosilane-modifledStOber silica. Colloids Surf. A Physicochem. Eng. Asp., 132 (1998) 229-239... 

The bet structure was also observed by using confocal scanning laser microscopy (581. The bet crystal structure of the monodispersed silica sphere of radius 0.525 pm dispersed into an index matched mixture of 16 wt.% water and 84 wt.% glycerol under an electric field 1 kV/mm is shown in Figure 8 for the suspension of the particle volume fraction about 10 vol%. When the particle volume fraction reaches 45 vol%, without an applied electric field the particles are arranged in fee structure as shown in Figure 9a. Under the reaction of the an electric field of 1 kV/mm and 500 kHz, the fee structure is transformed into the bet structure as shown in Figure 9b. These... 

Figure 8. Confocal scanning laser microscopy image of the body-ccntcrcd tetragonal crystal formed from the monodispersed silica spheres of radius 0.525 pm dispersed into an index match mixture of 16 wt.% water and 84 wt.% glycerol. The particle volume fraction is about 10 vol%, and the applied electric field is 1 kV/mm. a) A view along a plane parallel to the E field b) A view looking down the -field showing the square. Reproduced with permission from Dassanayake, S. Fraden, A. van Blaaderen, J. Chem. Phys. 112(2000)3851...

Tani T., Madler L., Pratsinis S.E., Synthesis of zinc oxide/silica composite nanoparticles by flame spray pyrolysis. J. Mater. Sci. 2002 37(21) 4627 632 Van Blaaderen A., Vrij A. Synthesis and characterization of colloidal dispersion of fluorescent, monodisperse silica spheres. Langmuir 1992a 8(12) 2921-2931 Van Blaaderen A.V., Van Geest J., Vrij A. Monodisperse colloidal silica spheres from tetraaUcoxysi-lanes Particle formation and growth mechanism. J. Colloid Interface Sci. 1992b 154(2) 481-501... 

Ghosh Chaudhuri R, Paria S (2012) Core/shell nanoparticles classes, properties, synthesis mechanisms, characterization, and applications. Chem Rev 112 2373-2433 Stober W, Fink A, Bohn E (1968) Controlled growth of monodisperse silica spheres in the micron size range. J Colloid Interface Sci 26 62-69... 

A widely used method for preparing monodisperse silica spheres, developed by Stober, Fink, and Bohn (SFB) [85], is to hydrolyze tetraethyl-... 

Van Blaaderen, A. and Vrij, A. (1992) Synthesis and characterization of colloidal dispersions of fluorescent, monodisperse silica spheres. Langmuir, 8, 2921-31. 

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