Silica sphere multilayers

Encapsulation via the layer-by-layer assembly of multilayered polyelectrolyte (PE) or PE/nanoparticle nanocomposite thin shells of catalase in bimodal mesoporous silica spheres is also described by Wang and Caruso [198]. The use of a bimodal mesoporous structure allows faster immobilization rates and greater enzyme immobilization capacity (20-40 wt%) in comparison with a monomodal structure. The activity of the encapsulated catalase was retained (70 % after 25 successive batch reactions) and its stability enhanced. 

Zhu Y, Shah NH et al (2002) Influence of thermal processing on the properties of chlorpheniramine maleate tablets containing an acrylic polymer. Phaim Dev Technol 7(4) 481-489 ZhuY, Shi J et al (2005) Stimuli-responsive controlled dmg release from a hollow mesoporous silica sphere/polyelectrolyte multilayer core-shell structure. Angew Chem Int Ed 44 5083-5087 Zhu Y, Shah NH et al (2006) Controlled release of a poorly water-soluble drug from hot-melt extrudates containing acrylic polymers. Drug Dev Ind Pharm 32 569-583... 

Abstract The self-assembled formation of PFDTS features on mono- and multilayered silica sphere arrays is studied. The multiscaled roughness induced by PFDTS nanostructures on multilayer arrays gives rise to superhydrophobic behaviour. In contrast to previous work, the role of PFDTS is two-fold it lowers the surface energy and simultaneously provides the essential roughness to achieve superhydrophobicity. The importance of water in the formation of the nanostructured surfaces is discussed. 

We investigated the effect of PFDTS treatment on monolayer and multilayer arrays of silica microspheres with varying diameters. Details pertaining to the preparation methods and experimental conditions are available elsewhere [15]. In Figure 1 the formation of a homogeneous layer on silica sphere monolayers and the formation of nanostructures on... 

Fig. 1 Schematic representation of the adsorption of PFDTS on mono-layer (left) and multilayer (right) arrays of silica spheres. The silica spheres are deposited by means of spin coating, while the PFDTS deposition is done by immersion into PFDTS-in-toluene solution...

Fig. 2 Top-view SEM images of monolayer (left) en multilayer (right) silica sphere arrays after PFDTS assembly. The silica sphere diameters amount to 140 nm (top), 440 nm (middle) and 830 nm (bottom). The insets show side-view images of cleaved samples, as well as the large static contact angles (8/tl droplets) revealing the (super) hydrophobicity of the superstructures...

Table 1 Water contact angles (CA) and sliding angle (SA) on PFDTS-treated mono- and multilayer arrays for different silica sphere diameters. Also, the surface coverages of PFDTS nanostructures are given...

We have investigated the effect of PFDTS deposition on monolayer and multilayer arrays of silica spheres having different sizes. PFDTS deposition under ambient conditions... 

Fig. 18 TEM images (a, b) of hollow mesoporous silica sphere (HMS) with a 3D pore network, core-shell structure, (c) with polyelectrolyte multilayer coating as a stimuli-responsive...

Y.F. Zhu, J.L. Shi, W.H. Shen, X.P. Dong, J.W. Feng, M.L. Ruan, and Y.S. Li, Stimuli-Responsive Controlled Drug Release from a Hollow Mesoporous Silica Sphere/Polyeleclrolyte Multilayer Core-Shell Structure, Angew. Chem. Ini. Ed., 44, 5083-5087(2005). 

J., Ruan, M., and Li, Y. (2005) Stimuli-responsive controlled drug release from a hollow mesoporous silica sphere/ polyelectrolyte multilayer core-shell structure. Angew. Chem., Int. Ed., 44, 5083-5087. 

Caruso, R.A., Susha, A. and Caruso, F. (2001) Multilayered titania, silica, and laponite nanopartides coating on polystyrene colloidal templates and resulting inorganic hollow spheres. Chemistry of Materials, 13, 400—409. 

Caruso, R. A. Susha, A. Caruso, F. Multilayered Titania, Silica, and Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres. Chem. Mater. 2001,13,400-409. 

Scheme 8 Formation of cross-linked hollow spheres by (a) silica nanopartide templated layer-by-layer (LbL) assembly of polyelectrolytes, (b) cross-linking of polymer multilayer assembly by TEC, (c) functionalization with PEG using residual thiol, and (d) removal of silica core by hydrofluoric acid (HF) etch. ...

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... 

Nano-Partide Controllable Assembly, Figure 7 Illustration of procedures for preparing hollow inorganic silica and inorganic-hybrid spheres through colloid-templated electrostatic LBL assembly of silica NP polymer multilayers, followed by the removal of the templating core and, opfionally, the polymer. Reproduced with permission from [17]... 

Caruso and Moehwald have demonstrated that colloidal particles can also be used as substrates for the nano-scaled layer-by-layer assembhes [227]. The size of the colloidal particles used as microtemplates ranges from tens of nanometers to submillimeters. The selective dissolution of the core template provides hoUow capsules of the multilayered assembhes, which can be employed as microreactors [228], Lvov et al. demonstrated the nano-coating of cohoid surface by polyion-nanoparticle multilayers. A silica latex of 300 nm in diameter was used as a microtemplate for layer-by-layer assembhes of 75-nm diameter sihca spheres [229]. 

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