Stober silica spheres

APS is known for its stability in basic solutions (10). The amine functionality facilitates the coupling of other desired molecules to a particle. For these reasons, this alkoxide was chosen to coat the surface of the Stober silica spheres. A simple procedure was followed, first described by Philipse and Vrij (4), who used other coupling agents. Badley et al. (11) also described the coupling of APS and other organosilanes to silica. 

Surprisingly, all the quantitative spectra of the alcosol particles looked similar. As is also demonstrated in Table III, the siloxane structure of all the Stober silica spheres is more or less constant and independent of the particle size and thus the reaction conditions. Even the coated stearylsilica particle A3S is no exception, despite the 3 h at 200 °C necessary for the coating. Thus, the differences mentioned in the previous section in the particle morphology are not correlated with the siloxane structure. 

Hollow particles of crystalline layered silicate have also been reported. Hollow spheres consisting of nanosheets of nickel silicate (NiSiOs) can be formed using silica sphere templates. When Stober silica spheres (500 nm) were treated with a mixture of NiS04 and NHs a nickel silicate shell was formed on the surfece. 

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

Stober A process for making metal oxides in the form of small spheres of uniform diameter by the controlled hydrolysis of metal alkoxides. First used in 1968 to make silica spheres from alkyl silicates. The products can be used to make high quality oxide ceramics. See also Sol-Gel. 

The formation of ordered sphere-packing structures was observed in certain rheological experiments as just described. Due to the extremely uniform size of the particles, an ordered dense packing structure will develop during sedimentation of the Stober silica particles (see Fig. 2.1.12) when the dispersion is either sterically or electrostatically stabilized. The gemstone opal is essentially based on this principle (80-88). A transmission election replica picture is shown in Figure 2.1.13. The uniform... 

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... 

Controlled hydrolysis is one of the most popular methods for processing silica spheres in the range of 10-1,000 nm. The method was developed by Stober, Fink, and Bohn (SFB) [226-229] and is based on the hydrolysis of TEOS in a basic solution of water and alcohol. Particle size depends on the reactant concentration, i.e., the TEOS/alcohol ratio, water concentration, and pH (>7). This method has been extended to other metal oxide systems with similar success, particularly for Ti02 synthesis [85,230]. The hydrous oxide particles precipitated by the hydrolysis of an alkoxide compound have the same tendency to agglomerate as that described for metal colloid systems. Different stabilizers can be used to stabilize these particles and prevent coagulation (step 2). These stabilizers control coagulation by electrostatic repulsion or by steric effects [44], similarly to the metal colloid systems. 

Polystyrene (PS) spheres were prepared with emulsifier fiee emulsion polymerization. Silica spheres were prepared following the modified StOber method. All chemicals were used without further purification. 

Dense silica nanoparticles have received considerable attention since monodisperse colloidal silica spheres, obtained liom aimnoniacal TEOS solution, were reported in the late 1960s by Stober et aL [1]. These dense particles, more often being monodispersed with controlled particle size, a well-defined morphology, and a surface with silanol groups by which they could be functionalized, are used for a variety of commercial applications including colmants, fillers and pigments. 

Among metal oxide compositions, the chemistry of silica is the most widely studied and weU established, from the classical Stober synthesis of a silica sphere [23] to the recently developed surfactant-mediated synthesis of mesoporous silica [24, 25]. These developments were mainly enabled by the availability of stable silica precursors, their controllable hydrolysis and condensation, and the stable oxidation state of silica. Based on previously established chemistries, sol-gel or microemulsion methods were used to synthesize silica-shell-based core-shell NPs. 

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... 

Stober, W., A. Fink, and E. Bohn, Controlled Growth of Mtmodisperse Silica Spheres in the Micron Size Range. J. Coll. Int. Sci., 1968.26 p. 62. 

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

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