title: Surface assembly and plasmonic properties in strongly coupled segmented gold nanorods.
abstract: An assembly strategy is reported such that segmented nanorods fabricated through template-assisted methods can be robustly transferred and tethered to a pre-functionalized substrate with excellent uniformity over large surface areas. After embedding the rods, sacrificial nickel segments were selectively etched leaving behind strongly coupled segmented gold nanorods with gaps between rods below 40 nm and as small as 2 nm. Hyper-spectral imaging is utilized to measure Rayleigh scattering spectra from individual and coupled nanorod elements in contrast to common bulk measurements. This approach discerns the effects of not only changing segment and gap size but also the presence of characteristic defects on the plasmonic coupling between closely spaced nanorods. Polarized hyper-spectral measurements are conducted to provide direct observation of the anisotropic plasmonic resonance modes in individual and coupled nanorods, which are close to those predicted by computer simulations for nanorods with ideal shapes. Some common deviations from ideal shape such as non-flat facets and asymmetric tails are demonstrated to result in the appearance of characteristic plasmon resonances, which have not been considered before. The large-scale assembly of coupled noble nanostructures with fine control over geometry and high uniformity provides means to strongly tune the scattering, absorption, and near-field plasmonic properties through the geometric arrangement of precisely controlled nanorod segments.
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology Atlanta, GA 30332, USA.
authors.forename: Maneesh K
authors.initials: MK
authors.lastname: Gupta
authors.forename: Tobias
authors.initials: T
authors.lastname: König
authors.forename: Rachel
authors.initials: R
authors.lastname: Near
authors.forename: Dhriti
authors.initials: D
authors.lastname: Nepal
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Drummy
authors.forename: Sushmita
authors.initials: S
authors.lastname: Biswas
authors.forename: Swati
authors.initials: S
authors.lastname: Naik
authors.forename: Richard A
authors.initials: RA
authors.lastname: Vaia
authors.forename: Mostafa A
authors.initials: MA
authors.lastname: El-Sayed
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Tsukruk
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold
keywords: gold nanorods; hyperspectral imaging; plasmon coupling; surface assembly; templated assembly