Core/shell composites

Electrically conducting polymers provide a new way to prepare conducting composites. It was shown in Chapter 11 how to prepare films of conducting polymers on non-conducting materials using adhesion promoters. The surface of the polymer became conducting. With the 

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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]. 

Hirakawa, T. and P.V. Kamat (2005). Charge separation and catalytic activity of Ag Ti02 core-shell composite clusters under UV-irradiation. Journal of the American Chemical Society, 127(11), 3928-3934. 

Several other examples of conducting-polymer/metal oxide nanocomposite materials also exist for chemical sensing of a range of analytes, including humidity [58,59], NO2, [60,61], CO and H2 [60], and H2O2 [62]. This latter example employed the use of Prussian blue, which is an iron complex with excellent catalytic properties, particularly towards O2 and H2O2. Miao et al. [62] stabilized nanoparticles of Prussian blue with polymerization of a PANI shell to form a Prussian blue/PANI core-shell composite. 

Yamaguchi K, Ito M, Taniguchi T, Kawaguchi S, Nagai K (2004) Preparation of core-shell composite polymer particles by a novel heterocoagulation based on hydrophobic interaction. Colloid Polym Sci 282(4) 366-372... 

Robert et al. [126] prepared PP/montmorillonite (MMT)/PPy ternary nanocomposites which exhibit high dielectric losses and absorption loss (SE ) of —67 dB in 0.1-1.5 GHz range. Xu et al. [76] prepared Microstructured Ni/PPy core/shell composites by varying the Ni pyrrole ratio and observed that permeability of Ni/PPy composites presents a natural magnetic resonance at 6.0 GHz. The Cole-Cole semicircle was applied to explain the permittivity and the reflection loss (R ) properties of Ni/PPy composites were enhanced substantially, as compared to those of pure Ni powder. The minimum reflection losses of Ni/PPy composites (Figure 9.31a) from Ni/Py )4 1,2 1,1 1, and 1 2 are -15.2, -14.8, -8.4, and -6.8 dB at 13.0, 14.4, 11.6, and 8.6 GHz, respectively, and EM absorption less than -10 dB is only formd for Ni/Py) 4 1 and 2 1, in the 11-15.4 GHz range for the former and 12-17.5 GHz for the latter. The EM absorption properties of Ni/PPy composites from Ni/Py) 4 1 and 2 1 are much better than those of Ni/PANl nanocomposites and BaTi03/PANI composites at... 

P. Xu, X. Han, C. Wang, D. Zhou, Z. Lv, A. Wen, X. Wang, B. Zhang, Synthesis of Electromagnetic Functionalized Nickel/Polypyrrole Core/Shell Composites./Phys ChemB 2008,112,10443-10448. 

Oka and co-workers [14] employed the Pickering emulsion technique to fabricate core-shell composite particles, composed of copolymer poly(3HB-co-3HV) particles and magnetic iron oxide nanoparticles, for targeted drug delivery based on magnetic guidance. Iron oxide... 

Wu et al. reported a polypyrrole-reduced graphite oxide core-shell composite fabricated through electrostatic interactions, and achieved a capacity of 557 F/g at a current density of 0.5 A/g, with 85% retention of capacity after 1000 charge-discharge processes [43]. 

Some non-carbon supports are also electrochemically unstable. For example, when TIC was used as a catalyst support to form Pt/TiC and PtsPd/TiC ORR catalysts, its electrooxidation at potential higher than 0.8 V vs RHE was found. When TiC Ti02 core—shell composite was used for the support, the electrochemical stabilities were significantly improved. 

Gan L, Heggen M, Rudi S, Strasser P (2012) Core-shell compositional fine structiffes of dealloyed PtxNii.x nanoparticles and their impact on oxygen reduction catalysis. Nano Lett 12(10) 5423-5430... 

SYNTHESIS AND PHYSICAL PROPERTIES OF THE CROSSLINKING POLY(BUTYL ACRYLATE)/POLYSTYRENE CORE-SHELL COMPOSITE LATEX... 

Polybutyl acrylate/polyglycidyl methacrylate core-shell latex was prepared by a two stage emulsion polymerisation. The formation of core-sheU morphology was confirmed by contact angle measuremoits. The impact properties of blends of polybutyl acrylate/polyglycidyl methacrylate core-shell composite particles with epoxy resin is discussed. 15 refs. 

The structure of core-shell composite particles was dien characterized by TEM. Figure 4 shows a TEM image for fully MZF coated Ni particles the dark spherical regions are die nickel cores, whereas the lighter areas are die MZF shell coatings. The MZF shell pardcle size can be seen to be 20 nm, and an electron diffraction pattern taken from a region containing only MZF... 

Nanoparticles can be composed of any substance, including metals [21, 22], semiconductors [23, 24], core-shell composite architectures [25—27], and organic polymers [28], These particles often display properties intermediate between quantum and bulk materials because of their intermediate size [29] and large surface area to volume ratio [30], Nanoparticle of different sizes and shapes exhibit different absorbance and fluorescence features and reveal polymerization effects [31], Some of the characteristics of metallic nanoparticles are shown in Table 1. 

There is technological interest concerning the use of composite particles in functional coatings, and a number of excellent reviews have been prepared on conductive nanocomposites [53-56]. Although the synthesis of composites always demands some entrapment (encapsulation) of polymers, the following sections will illustrate mainly the core-shell composite particles. These composite particles can be divided broadly into either organic-ICP or inorganic-ICP. 

For example, Chen et al. prepared zinc oxide whisker/ polyaniline core-shell composite material using in situ polymerization. The specific operation is as follows. A certain amount of treated zinc oxide whiskers, aniline, and ethanol are well mixed then the appropriate amount of 0.01 mol/L HCl is added dropwise with stirring in an ice bath of 0-2°C to initiate polymerization and the mixture is reacted for 10 minutes. The reaction mixture is centrifuged, filtered, and then dried in a vacuum furnace at 50°C for 24 h. 

S.I.U. Madrid, U. Pal, K. Umapada, Y.S. Kang, J. Kim, H. Kwon, J. Kim, Fabrication of Fe304 mSi02 core-shell composite nanoparticles for drug delivery applications. Nanoscale Res. Lett. 10, 1-8 (2015)... 

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