title: Collective plasmon modes excited on a silver nanoparticle 2D crystalline sheet.
abstract: This paper describes unique plasmonic characteristics of two dimensional (2D) crystalline sheets composed of homogeneous Ag nanoparticles (AgNPs) fabricated by the Langmuir-Schaefer method at an air-water interface. The localized surface plasmon resonance (LSPR) band of the Ag nanosheet was tuned by changing the interparticle distance of AgNPs via the length of the organic capping molecules. Red shift of the LSPR band of the AgNPs sheet followed an exponential law against the interparticle distance in a similar manner to the previous reports of metal nanodisc pairs. However, the shift was much larger and less dependent on the interparticle separation gap. This phenomenon is reasonably interpreted as the long-range interaction of LSPR in the 2D sheet ('delocalized' LSPR) confirmed by simulation using the finite difference time domain (FDTD) method. The FDTD simulation also revealed additional enhancement of local electric fields on the 2D sheet compared to those on the single or paired particles.
authors.affiliation: Department of Electronic Chemistry, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midoriku, Yokohama 226-8502, Japan.
authors.forename: Mana
authors.initials: M
authors.lastname: Toma
authors.forename: Koji
authors.initials: K
authors.lastname: Toma
authors.forename: Kanae
authors.initials: K
authors.lastname: Michioka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ikezoe
authors.forename: Daiki
authors.initials: D
authors.lastname: Obara
authors.forename: Koichi
authors.initials: K
authors.lastname: Okamoto
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tamada