Controlled synthesis of the metal nanoparticles (NPs) is an important topic due to distinct optical properties of its metal NPs depend on their size, shape and surface morphology. Especially, nanoshell structure have interesting properties for their tunable surface plasmon resonance bands easily just by varying the ratio of core size to metallic shell thickness or controlling surface morphology of metallic shell. In that sense, a controlling surface morphology of metal nanoshell is one of the key factors to change surface plasmon resonance and scattering properties of such NPs. In general, surface morphology control of nanoshell has been studied by changing surfactant such as cetyltrimethylammonium bromide (CTAB) and their halide derivatives or introducing seed-mediated synthesis for kinetically controlled reaction. However, they have several problems such as a using excessive amount of bulky surfactant and time-consuming multi-step processes.
In this poster, we presented one-step and a surfactant-free synthesis for controlling morphology and thickness of silver nanoshells using alkylamines as a reductant and capping agent. As alkylamines, the butylamine, octylamine, dodecylamine, hexadecylamine, ethanolamine, 3-amino-1-propanol and tributylamine were used for studying on effects of an alkyl chain length, an existence of hydroxyl group, and the degree of alkyl chain in silver shell formation, which result in a change on surface morphology and thickness of silver nanoshell. This change were attributed to several factors such as selective capping properties, steric effect, reducing power along the alkylamine.
Confirming the enhanced scattering properties of synthesized silver nanoshell with different surface morphologies, optical properties of each silver nanoshells were investigated by observing Surface Enhanced Raman Scattering (SERS) at the single particle levels. According to nanoshell surface morphology, intense and uniform SERS signal was detected for single particle and their SERS enhancement factor for each particle were calculated up to ~107. This enhanced scattering properties of silver nanoshell showed a potential as ultra-high sensitive NIR SERS probe for in vivo or ex vivo targeting experiment.