Facile Synthesis and One-Dimensional Assembly of Cyclodextrin-Capped Gold Nanoparticles and Their Applications in Catalysis and Surface-Enhanced Raman Scattering

Controlled synthesis of ALL nanoparticles with adjustable sizes (10-50 nm) and narrow size distributions (<10% in standard deviation) was realized by reducing hydrochloroauric acid with alpha-cyclodextrin (alpha-CD) in an alkaline aqueous solution, which was very simple and green. It was revealed that a proper pH was essential to the formation of stable dispersions of nonaggregated ALL nanoparticles and a higher pH would lead to the welding of the ALL nanoparticles into one-dimensional (ID) wires or three-dimensional (3D) aggregates. Moreover, 1D assembly of alpha-CD-capped Au nanoparticles into nanochains was readily induced by partial removal of the organic stabilization shell, which resulted from the host-guest interactions between alpha-CDs capped on Au nanoparticle surfaces and toluene molecules. Finally, the as-prepared Au nanoparticles were found to serve as effective catalyst to activate the reduction of 4-nitrophenol in the presence of NaBH4, and the application of the assembled ALL nanoparticle thin film as a substrate for surface-enhanced Raman scattering (SERS) was also demonstrated.