Organic/inorganic composite colloids

Keywords Clays Emulsion polymerization Iron oxide Metals Organic/ inorganic composite colloids Particle morphology Pigments Quantum dots Silica Surface modification... 

Figure 4.27 Long-chain bolaamphiphiles with an electroneutral and a cationic head group form membranes around anionic polymers (here DMA) and colloids. Synkinesis of organic-inorganic composite materials in bulk aqueous media can thus be achieved. ...

The chemical s mthesis and analysis of properties of layered nanocomposites devoted tens publications. In the last decade for the synthesis of metal, oxide, hydroxide nanostructures used method of laser ablation of metals in a liquid medium [10-12]. However, the researches aimed at producing layered organic-inorganic composites by this flexible, simple method are not enough [13]. Practically important is also the question of the structural stability of these composites in the colloidal state under the influence, in particular, laser radiation optical range (colloidal stability of drugs, film, optical data carriers, etc.). 

The sol-gel technique has been used to prepare sub-micrometer metal oxide powders [5] with a narrow particle size distribution and unique particle shapes (e.g. AljOj, TiOj, ZrOj, Fe Oj). Uniform SiO spheres have been grown from aqueous solutions of colloidal SiO [6]. Metal-ceramic composites (e.g. Ni-Al Oj, Pt-ZrO ) can also be prepared in this manner [7]. Organic-inorganic composites have been prepared by the sot-gel route. By employing several variants of the basic sol-gel technique, a number of multicomponent oxide systems have been prepared. Some typical examples are SiO -B Oj, SiO -TiO, SiO -ZrO, SiO -Al Oj and ThO -UO. A variety of ternary and still more complex oxides such as PbTiOj, PbTij r 3 and NASICON have been prepared by this technique [1-3, 8]. 

S. Briat, C. Gauthier, G. Vigier, J. Perez, Composite polymer colloid nucleated by fimctionalized silica in Hybrid Organic-Inorganic Composites, Chap. 10, pp. 112-124, J.E. Mark, C.Y.-C. Lee, P.A. Bianconi (Eds.), ACS Symposium Series 585, Washington DC, 1995. 

Colloids are suspended particles in a solution medium and will not settle out over time. They are common in natural waters and can enhance the apparent solubility of a wide range of water pollutants, both organic and inorganic. Colloids maybe considered as an extension of the solid and aqueous phases and are formed by conditions that can be quite variable in time and space hence colloids can be dynamic. The composition of colloids can vary with the composition of the solid and aqueous phases. Colloids can be made up of organic, inorganic, or a mixture of materials. 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

Considerable research effort was focused on systems of colloidal gold of which a broad variety of synthetic procedures were reported [140 b, fj. While native colloidal gold solutions are only stable for a restricted time, Brust et al. [141] were able to overcome this problem by developing a simple method for the in situ preparation of alkyl thiol-stabihzed gold nanoparticles. This synthetic route yields air-stable and easy to handle passivated nanoparticles of moderate polydispersity, and is now commonly employed for the preparation of inorganic-organic core-shell composites. Such composites are used as catalytic systems with principally two different functions of the protective 3D-SAM layer. Either the metal nanoparticle core can be used as the catalytically active center and the thiol layer is only used to stabihze the system [142], or the 3D-SAM is used as a Hnker system to chemically attach further catalytic functions [143]. 

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