title: Interfacial liquid-state surface-enhanced Raman spectroscopy.
abstract: Oriented assemblies of functional nanoparticles, with the aid of external physical and chemical driving forces, have been prepared on two-dimensional solid substrates. It is challengeable, however, to achieve three-dimensional assembly directly in solution, owing to thermal fluctuations and free diffusion. Here we describe the self-orientation of gold nanorods at an immiscible liquid interface (that is, oleic acid-water) and exploit this novel phenomenon to create a substrate-free interfacial liquid-state surface-enhanced Raman spectroscopy. Dark-field imaging and Raman scattering results reveal that gold nanorods spontaneously adopt a vertical orientation at an oleic acid-water interface in a stable trapping mode, which is in good agreement with simulation results. The spontaneous vertical alignment of gold nanorods at the interface allows one to accomplish significant additional amplification of the Raman signal, which is up to three to four orders of magnitude higher than that from a solution of randomly oriented gold nanorods.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742, Korea.
authors.forename: Kihoon
authors.initials: K
authors.lastname: Kim
authors.forename: Hye Soo
authors.initials: HS
authors.lastname: Han
authors.forename: Inhee
authors.initials: I
authors.lastname: Choi
authors.forename: Chiwon
authors.initials: C
authors.lastname: Lee
authors.forename: SoonGweon
authors.initials: S
authors.lastname: Hong
authors.forename: Sang-Hee
authors.initials: SH
authors.lastname: Suh
authors.forename: Luke P
authors.initials: LP
authors.lastname: Lee
authors.forename: Taewook
authors.initials: T
authors.lastname: Kang