Sphere template

Lanthanide-doped inverse photonic crystals have been reported.282 The lattices were prepared by infilling self-assembled polystyrene sphere templates with a mixture of zirconium alkoxide and europium at 450 °C, the polystyrene spheres were burnt out leaving hollow spheres of air, and the infilled material was converted to Zr02 Eu3+. The PL properties of the resulting photonic lattice were reported.282 The possibility of including phosphors into photonic lattices could lead to many... 

Recently, a general method to prepare protein-based particles with tailored properties through MS sphere templating was reported [98]. In this approach, polyelectrolytes are infiltrated into the mesopores of MS spheres pre-loaded with... 

In this paper, we report the synthesis of mesoporous silica and alumina spheres with nanometer size (80 to 900 nm) in the present of organic solvent with aqueous ammonia as the morphological catalyst to control the hydrolysis of tetraethyl orthosilicate (TEOS) and aluminum tri-sec-butoxide.1181 Mesoporous silica spheres show hexagonal arranged pores with monodispersed pore sizes ( 2.4 nm) and high surface areas ( 1020 m2/g) similar to MCM-41. A large pore ( 10 nm) mesoporous alumina sphere templated by triblock copolymer is thermally stable. Calcined alumina sphere shows disordered mesoporous arrays with relatively uniformed pore size distribution and high surface areas ( 360 m2/g). 

In summary, nanometer-sized mesoporous silica and alumina spheres with tunable diameters (80 - 900 nm) can be synthesized in organic solvent. Mesoporous silica spheres templated by cationic surfactant (CTAB) have hexagonal array with monodispersed pore size (-2.4 nm), high surface areas (-1020 m2/g), and pore volume (1.02 cm3/g). Mesoporous alumina spheres templated by amphiphilic triblock copolymer show a large disordered mesopore (10.0 nm) and high BET surface area (360 m2/g). 

Stein A., Sphere templating methods for periodic porous solids, Micropor. Mesopor. Mater. 44-45 (2001), pp. 227-239. 

M.A. (2000) Electrochemical deposition of macroporous platinum, palladium and cobalt films using polystyrene latex sphere templates. Chemical Communications, 1671-1672. 

Fig. 7 Schematic representation of the procedure for encapsulating enzyme in polyelectrolyte microcapsules using MS spheres as templates (I) enzyme immobilization in MS spheres (II) LbL assembly of oppositely charged polyelectrolytes (PE) (III) MS sphere template dissolution using buffered hydrofluoric acid (IV) enzyme encapsulation in a polyelectrolyte microcapsule and (V) enzyme release via altering the shell permeability by pH or salt changes. Reprinted with permission from Advanced Materials [76]...

Inverse opal structures have been classified into three structures, the so-called residual volume structure , shell structure and skeleton structure . The residual volume structure is a perfect inverse opal structure, which can be produced if the whole space among the opal spheres is completely filled by the product materials. If the space is incompletely filled, the surface of the sphere template is covered by the product materials, and a shell structure is generated. Most amorphous compounds tend to form a shell structure. On the other hand, crystalline compounds tend to form a skeleton structure. 

The use of polymer microspheres as template has the advantage of eliminating the chemical dissolution step since the polymer template can simply wash away or burn off during the process. The use of polystyrene microspheres as template for the synthesis of ordered macroporous carbons was realised by Baumann and Satcher. Following infiltration of hydrogel into the interstitial spaces between polystyrene colloid spheres, the polystyrene sphere template was removed by washing with toluene, after which... 

Saul JM, Linnes MP, Ratner BD, Giachelh CM, Pun SH, Delivery of non-viral gene carriers fi om sphere-templated fibrin scaffolds for sustained transgene expression. Biomaterials, 2007, 28, 4705-16. 

Monodisperse latex spheres of a controlled size can be arranged into three-dimensional arrays and are used as templates to prepare well-defined cavities and structures once the latex sphere template has been removed. These latex spheres are identical to one another in size and shape and are often prepared from colloidal clusters resulting from the aggregation of sol-gel colloids (Section 5.6). The spherical polymer clusters can be fabricated by the slow addition of an aqueous solution into a reservoir of hydrophobic silicone liquid, forming emulsion droplets. This produces a highly structured porous matrix with a well-defined structure upon polymerisation. The size of the droplets is controlled by the concentration of the aqueous latex, the speed at which the suspension is stirred and the ratio between the silicone liquid and latex. As the concentration of the latex spheres increases to its critical concentration, i.e. the concentration at which the colloidal spheres start to order themselves into a close-packed structure, the balls are filtered off and are dried, ready to be used as templates. 

In this chapter, we provide an overview of the recent research and development in the preparation, characterization, and application of novel porous carbons using both the endotemplate and the exotemplate methods. A discussion of zeolite templates for microporous carbons is followed by that of ordered mesoporous silica templates for OMCs, nanoparticle templates for mesoporous carbons, sol-gel processed porous carbons, self-assembled colloidal crystal templates for ordered macroporous carbons, and colloidal sphere templates for hollow carbon spheres, as well as other templating approaches to preparing carbon nanostructures. Then,... 

FIGURE 2.47 FESEM images of (a) a silica sphere template and (b, c, and d) hollow carbon spheres of different magnifications. (From Wang, Y., Su, F., Lee, JY., and Zhao, X.S. Chem Mater 18 1347-1353, 2006. With permission.)... 

Figure 9.7. Scanning electron micrographs of macroporous platinum and cobalt films that were electrochemicaUy deposited through polystyrene latex spheres preassembled on gold electrode surfaces. Figures 9.7 (a) and (b) show formed cobalt films, while Figures 9.7 (c) and (d) show formed Pt films [75]. (Bartlett PN, Birkin PR, Ghanem MA, Electrochemical deposition of macroporous platinum, palladium and cobalt films using polystyrene latex sphere templates, Chem Commun 2000 17 1671 Figure 1. Reproduced by permission of The Royal Society of Chemistry.)...

Fig. 2 SEM micrographs showing the remaining titania skeleton after infiltration of the silica colloidal crystals and removing the silica by an etching process. Reprinted from Andreas Stein Sphere templating methods for periodic porous solids, Microporous Mesoporous Mater., 44- 45 (2001) 227-239, Copyright 2001 with permission from Elsevier Science...

Sihcate composites can provide an efficient size-exclnsion membrane. The pore size distribntion can be controlled, at least to some extent, by incorporation of water-solnble polymers such as poly(ethylene glycol) and their leaching after sol-gel formation or by pH control. On the low-pore-size side, low-pH silicate processing may yield silicate membranes that exhibit Knudsen flow and can separate nitrogen from air [245]. The npper limit for porous silicates probably lies in living cell templated materials [246,247] or latex sphere templates [248], and in sol-gel-derived ruthenium and vanadinm oxide aerogels for supercapacitor applications [249,250]. 

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