Silica core-shell nanoparticles luminescent

F. Magnan, J. Gagnon, F.G. Fontaine, D. Boudreau, Indium silica core-shell nanoparticles as plasmonic enhancers of molecular luminescence in the UV region. Chem. Commun. 49, 9299-9301 (2013)... 

Santra S, Liesenfeld B, Bertolino C, Dutta D, Cao Z, Tan WH, Moudgil BM, Mer-icle RA (2006) Fluorescence lifetime measurements to determine the core-shell nanostructure of FlTC-doped silica nanoparticles An optical approach to evaluate nanoparticle photostability. J Luminesc 117 75-82... 

Inspired by the work of Liu and co-workers who have described a new kind of core-shell (sUica-PEG) nanoparticles as platform for dmg-delivery [71], we have very recently proposed [93] a synthetic strategy that affords monodispersed and ordered core-shell silica nanoparticles. Such systems allow the irreversible inclusion of dye molecules in the silica core and present a stable biocompatible and water soluble polymeric protective shell. For these reasons these materials appear particularly promising in the development of luminescent probes for in vitro and, hopefully, in vivo medical and bio-analytical applications. 

A dielectric oxide layer such as silica is useful as shell material because of the stability it lends to the core and its optical transparency. The thickness and porosity of the shell are readily controlled. A dense shell also permits encapsulation of toxic luminescent semiconductor nanoparticles. The classic methods of Stober and Her for solution deposition of silica are adaptable for coating of nanocrystals with silica shells [864,865]. These methods rely on the pH and the concentration of the solution to control the rate of deposition. The natural affinity of silica to oxidic layers has been exploited to obtain silica coating on a family of iron oxide nanoparticles including hematite and magnetite [866-870]. The procedures are mostly adaptations of the Stober process. Oxide particles such as boehmite can also be coated with silica [871]. Such a deposition process is not readily extendable to grow shell layers on metals. The most successful method for silica encapsulation of metal nanoparticles is that due to Mulvaney and coworkers [872—875]. In this method, the smface of the nanoparticles is functionalized with aminopropyltrimethylsilane, a bifunctional molecule with a pendant silane group which is available for condensation of silica. The next step involves the slow deposition of silica in water followed by the fast deposition of silica in ethanol. Changes in the optical properties of metal nanoparticles with silica shells of different thicknesses were studied systematically [873 75]. This procedure was also extended to coat CdS and other luminescent semiconductor nanocrystals [542,876-879]. 

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