Core-shell particle nanoparticle

Suzuki, D. Kawaguchi, H., Modification of gold nanoparticle composite nanostructures using thermosensitive core shell particles as a template, Langmuir. 2005, 21, 8175 8179... 

Template core-shell particles with cores comprised mainly of poly(glycidyl methacrylate) (GMA) and shells consisting mainly of PNIPAM and amino or thiol-functionalized have been used for the synthesis of Au NPs. The obtained hybrid particles exhibited a reversible color change from red to purple, which originated from the surface plasmon resonance of gold nanoparticles and was temperature-dependent in the range 25-40 °C [96] (Scheme 3.15). 

The thickness of the imprinted polymer shell can be also tuned in the range 10—40 nm by changing the relative amounts of functionalised silica nanoparticles and polymer shell precursors. The resulting core-shell particles exhibit enhanced capacity of rebinding the TNT template over 2,4-dinitrotoluene in comparison to particles prepared by precipitation polymerisation. Nevertheless, this strategy, although leading to impressive results, cannot be easily applied to other templates and monomers. 

Fig. 10 Schematic description of the strategy followed by Whitcombe et al. for the preparation of core-shell MIP nanoparticles with imprinted sites located on the particle surface. Reproduced with permission from [124]...

Burns A Ow H Wiesner U, Fluorescent core-shell silica nanoparticles Towards Lab on a Particle architectures for nanobiotechnology, Chem. Soc. Rev., 2006, 35, 1028-1042. 

A variation of this approach towards redispersible PE-surf nanoparticles was presented by Hentze et al. [130]. Their particle formation procedure is as follows in a first step they prepared core-shell particles with a weakly cross-linked core of poly(styrene) and a shell of poly(ethylene oxide). Secondly, the cores were sulfonated to poly(styrene sulfonate). The cores were complexed with cationic surfactants in the third and final step. They became mesomorphous due to the complexation and show a characteristic length that varies between 2 and 4 nm depending on the alkyl chain length of the surfactant. The mean size of the whole particle is around 400 nm. 

Fig. 8 Composite particles consisting of thermosensitive core-shell particles in which metallic nanoparticles are embedded. Left The composite particles are suspended in water, which swells the thermosensitive network attached to the surface of the core particles. In this state, the reagents can diffuse freely to the nanoparticles, which act as catalysts. Right At higher temperatures (T > 32°C) the network shrinks and the catalytic activity of the nanoparticles is strongly diminished...

Suzuki D, Kawaguchi H (2005) Gold nanoparticle localization at the core surface by using thermo sensitive core-shell particles as a template. Langmuir 21 12016-12024... 

Lu Y, Mei Y, Drechsler M, Ballauff M (2006) Thermosensitive core-shell particles as carriers for Ag nanoparticles modulating the catalytic activity by a phase transition in networks. Angew Chem Int Ed Engl 45 813-816... 

Core-shell nanoparticles can also be fabricated using microemulsions. This was performed using a two-stage microemulsion polymerization beginning with a polystyrene seed [62]. Butyl acrylate was then added in a second step to yield a core-shell PS/PBA morphology. The small microlatex led to better mechanical properties than those of similar products produced by emulsion polymerization. Hollow polystyrene particles have also been produced by microemulsion polymerization of MMA in the core with crosslinking of styrene on the shell. After the synthesis of core-shell particles with crosslinked PS shells, the PMMA core was dissolved with methylene chloride [63]. The direct cross-... 

Among the synthetic methods, the reverse micelle technique shall only briefly be mentioned. It is based on the use of water droplets in an organic phase of a surfactant. bi Metal salts, dissolved in the water droplets, are reduced inside the nanometer-sized water volume, to result in nanoparticles trapped in the micelles. Alloy-like particles as well as bimetallic core-shell particles thus become available. Size distributions up to over 20% have to be put up with this technique. Another disadvantage of the reverse micelle procedure is the lack of crystallinity due to the low synthesis temperature (<100°C) requiring subsequent aimealing at 200-300 Fe, Co, and Ni... 

Bums A, Ow H, Wiesner U. Huorescent core-shell silica nanoparticles towards Lab on a Particle architectures for nanobiotechnology. Chem. Soc. Rev. 2006 35 1028-1042. Hindson BJ, Makarewicz AJ, Setlur US, Henderer BD, McBride MT, Dzenitis JM. APDS the autonomous pathogen detection system. Biosensors Bioelectron. 2005 20 1925-1931. 

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