title: Localized surface plasmon resonance nanosensor: a high-resolution distance-dependence study using atomic layer deposition.
abstract: Atomic layer deposition (ALD) is used to deposit 1-600 monolayers of Al(2)O(3) on Ag nanotriangles fabricated by nanosphere lithography (NSL). Each monolayer of Al(2)O(3) has a thickness of 1.1 A. It is demonstrated that the localized surface plasmon resonance (LSPR) nanosensor can detect Al(2)O(3) film growth with atomic spatial resolution normal to the nanoparticle surface. This is approximately 10 times greater spatial resolution than that in our previous long-range distance-dependence study using multilayer self-assembled monolayer shells. The use of ALD enables the study of both the long- and short-range distance dependence of the LSPR nanosensor in a single unified experiment. Ag nanoparticles with fixed in-plane widths and decreasing heights yield larger sensing distances. X-ray photoelectron spectroscopy, variable angle spectroscopic ellipsometry, and quartz crystal microbalance measurements are used to study the growth mechanism. It is proposed that the growth of Al(2)O(3) is initiated by the decomposition of trimethylaluminum on Ag. Semiquantitative theoretical calculations were compared with the experimental results and yield excellent agreement.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA.
authors.forename: Alyson V
authors.initials: AV
authors.lastname: Whitney
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Elam
authors.forename: Shengli
authors.initials: S
authors.lastname: Zou
authors.forename: Alex V
authors.initials: AV
authors.lastname: Zinovev
authors.forename: Peter C
authors.initials: PC
authors.lastname: Stair
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.forename: Richard P
authors.initials: RP
authors.lastname: Van Duyne
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods; D012680:Sensitivity and Specificity; D020349:Surface Plasmon Resonance
chemical_list: D000537:Aluminum Oxide