Synthesis and Characterization of Monodispersed Core−Shell Spherical Colloids with Movable Cores

Abstract

Gold nanoparticles have been conformally coated with amorphous silica (using a sol-gel method) and then an organic polymer (via surface-grafted, atom transfer radical polymerization) to form spherical colloids with a core-double-shell structure. The thickness of silica and polymer shells could be conveniently controlled in the range of tens to several hundred nanometers by changing the concentration of the reagent and/or the reaction time. Selective removal of the silica layer (through etching in aqueous HF) led to the formation of hollow polymer beads containing movable gold cores. This new form of core-shell particles provides a unique system for measuring the feature size and transport property associated with hollow particles. In one demonstration, we showed that the thickness of a closed polymer shell could be obtained by mapping the electrons backscattered from the core and shell. In another demonstration, the plasmon resonance band of the gold cores was used as an optical probe to follow the diffusion kinetics of chemical reagents across the polymer shells.

Metal@Silica yolk-shell nanostructures as versatile bifunctional nanocatalysts

“…(benzyl methacrylate) yolk-shell nanoparticles [15]. This diffusion may result from the presence of defects or less polymerized sites in the amorphous silica.…”

“…Numerous methods for the synthesis of yolk-shell nanoparticles (or nanorattles) have been developed [15][16][17]; however, studies of their practical application in heterogeneous catalysis have rarely been reported. Yin et al studied the formation of metal oxide hollow nanoparticles using the Kirkendall effect, and employed it to synthesize Pt@CoO yolk-shell nanoparticles [13].…”

Activators Regenerated by Electron Transfer for Atom‐Transfer Radical Polymerization of (Meth)acrylates and Related Block Copolymers

“…[8][9][10] It has been very successfully applied to the preparation of many nanocomposites, hybrids, and bioconjugates. [11][12][13][14][15][16][17][18][19][20][21][22][23] The advantages of ATRP, in comparison with other CRP processes, include the large range of available monomers and (macro)initiators, the simplicity of reaction setup, and the ability to conduct the process over a large range of temperatures, solvents, and dispersed media. [6,7,24] ATRP (Scheme 1) is a repetitive atom-transfer process between a macromolecular alkyl halide P n ÀX and a redoxactive transition-metal complex Cu I ÀX/ligand in which P n C radicals propagate (rate constant of propagation k p ) and are reversibly formed (rate constants k a and k da ).…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…285,468 With the advent of nanotechnology, there has also been a continuous increase in organic and inorganic core-shell nanoparticle discoveries with exceptional properties. 8 This gave rise to the discovery of several types of core-shell microstructures, such as spherical 256,284,285,468 , hexagonal 469,470 , multiple cores within a single shell 471,472 , onion-like 473,474 , movable core within shell 475,476 , and 2-D structures such as rods [477][478][479] , among others. A general notation is described here in an attempt to standardize the nomenclature used to define core-shell microstructures.…”

“…An intentional engineered "void" or "hollow", such as in Refs. 475,476 is considered an extra constituent that can be either core and/or shell.…”