Latex/silica spheres, assembly

The method relies on the properties of monodispersed latex/silica spheres to assemble, through colloidal interactions, into a well-ordered, face-centered-cubic colloidal crystal upon centrifugation, sedimentation, electrophoresis, oscillatory shear or pressing in the form of pellets. Following pre-assembly of the colloidal crystal template, the precursor is infiltrated into the empty octahedral and tetrahedral interstitial sites that exist between the spheres. After conversion of the precursor to the desired material inside the voids, the template is removed leaving... 

Several approaches towards the synthesis of hierarchical meso- and macro-porous materials have been described. For instance, a mixture that comprised a block co-polymer and polymer latex spheres was utilized to obtain large pore silicas with a bimodal pore size distribution [84]. Rather than pre-organizing latex spheres into an ordered structure they were instead mixed with block-copolymer precursor sols and the resulting structures were disordered. A similar approach that utilized a latex colloidal crystal template was used to assemble a macroporous crystal with amesoporous silica framework [67]. 

In Fig. 6, we illustrate some different ways that the core-shell topology could be varied for silica and gold. So far we have considered the two normal core-shell structures. We now focus on the third example the assembly of Au Si02 nanoparticles onto spherical polystyrene latex colloids. The resulting spheres are also essentially different to continuous metal shells grown on colloid templates, which have been reported by Halas and colleagues [17] and by van Blaaderen and coworkers [18]. Such continuous shells display optical properties associated with resonances of the whole shell, and are therefore extremely sensitive to both core size and shell thickness, while in the system presented here... 

The assembly was initially performed for Au Si02 with very thin shells (ca. 2 nm) on 640 nm polystyrene spheres [19] and later extended for latex cores of various sizes and gold nanoparticles coated with thicker shells. Examples of nanostructured colloids formed by assembly of Au Si02 with identical cores but silica shells with various thickness are shown in Fig. 7. It is clear that, although the surface of the particles is rough, the resultant layers are very compact... 

Ordered macroporous particles of silica and titania were fabricated by colloidal templating. The colloidal templates were assembled through colloidal crystallisation of suspended PS latex sphere particles in aqueous droplets straddling an air-oil interface. The shape of the template was controlled by the presence of additive surfactant or by the action of an applied electric field. 30 refs. 

H. Mohwald, Electrostatic self-assembly of silica nanoparticle-polyelectrolyte multilayers on polystyrene latex spheres, J. Am. Chem. Soc. 1998, 120,8523 8524 (b) A.S. Susha, F. Caruso, AL Rogach, G.B. 

The mostly used methods to monitor LbL deposition on monodisperse PS-latex particles for various substances are SPLS method and microelectrophoresis. Inorganic (magnetite, silica, titania and fluorescent quantum dots) nanoparticles [32-34], lipids [35-37] and proteins (albumin, immunoglobulin and others) [29, 38, 39] were incorporated as building block for shell formation on colloidal particles. In paper [39] the construction of enzyme multilayer films on colloidal particles for biocatalysis was demonstrated. The enzyme multilayers were assembled on submicrometer-sized polystyrene spheres via the alternate adsorption of poly(ethyleneimine) and glucose oxidase. The high surface area bio-multilayer coated particles formed were subsequently utilized in enzymatic catalysis. The step-wise coating of different lipids alternated with polyelectrolytes was performed by adsorption of preformed vesicles onto... 

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