| Abstract
| - Size tunable and structure tailored core−shell−shell nanospheres containing silica cores, gold nanoparticle shells,and controlled thicknesses of smooth, corrugated, or porous silica shells over the gold nanoparticles have been synthesized.The synthesis involved the deposition of gold nanoparticles on silica cores, followed by sol−gel processing oftetraethoxysilane (TEOS) or sodium silicate to form dense or porous silica shells, respectively, over the gold nanoparticles.The structures and sizes of the resulting core−shell−shell nanospheres were found to heavily depend on the sizesof the core nanoparticles, the relative population of the gold nanoparticles on each core, and the concentration of TEOS.While a higher TEOS concentration resulted in thicker and more uniform silica shells around individual larger silicacores (approximately ≥250 nm in diameter), the same TEOS concentration resulted in aggregated and twin core−shell−shell nanostructures for smaller silica cores (approximately ≤110 nm in diameter). The thinner silica shellswere synthesized by using a lower TEOS concentration. By using sodium silicate (Ung et al. J. Phys. Chem. B1999,103, 6770), the porous silica shells were synthesized. Controlled chemical etching of the core−shell−shell nanoparticleswith an aqueous KCN solution resulted in corrugated silica shells around the gold nanoparticles or corrugated silicananospheres with few or no gold nanoparticles. This has allowed synthesis of new types of core−shell−shell nanoparticleswith tailored corrugated shells. The nanoporous silica shells provided accessible structures to the embedded metalnanoparticles as observed from the electrochemical response of the gold nanoparticles.
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