Self-assembly of a micrometers-long one-dimensional network of cemented Au nanoparticles

The self-assembly of a necklace of Au nanoparticles on a flexible polymer chain that is mediated by a linker ion was investigated. A cadmium perchlorate hydrate solution was added dropwise, under constant stirring, to a citrate-functionalized 10-nm-Au-nanoparticle solution until a volume ratio of Cd solution was obtained. The color of the solution transformed from wine red to violet blue, which corresponded to a shift in the SPR (surface plasmon resonance) band from 525 nm for the Au nanoparticle solution. Cemented material was deposited by electrostatic attraction onto the oppositely charged substrate surface between Au electrodes. TEM and optical spectroscopy were used to confirm that replacing Cd²⁺ salt with similar concentration of monovalent salt, does not lead to any bridging of Au nanoparticles. Elemental analysis by energy dispersive X-ray indicated the presence of CdS in the necklace.