Collective Plasmonic Properties in Few-Layer Gold Nanorod Supercrystals.
Gold nanorod supercrystals have been widely employed for the detection of relevant bioanalytes with detection limits ranging from nano- to picomolar levels, confirming the promising nature of these structures for biosensing. Even though a relationship between the height of the supercrystal (i.e., the number of stacked nanorod layers) and the enhancement factor has been proposed, no systematic study has been reported. In order to tackle this problem, we prepared gold nanorod supercrystals with varying numbers of stacked layers and analyzed them extensively by atomic force microscopy, electron microscopy and surface enhanced Raman scattering. The experimental results were compared to numerical simulations performed on real-size supercrystals composed of thousands of nanorod building blocks. Analysis of the hot spot distribution in the simulated supercrystals showed the presence of standing waves that were distributed at different depths, depending on the number of layers in each supercrystal. On the basis of these theoretical results, we interpreted the experimental data in terms of analyte penetration into the topmost layer only, which indicates that diffusion to the interior of the supercrystals would be crucial if the complete field enhancement produced by the stacked nanorods is to be exploited. We propose that our conclusions will be of high relevance in the design of next generation plasmonic devices.
Bionanoplasmonics Laboratory, CIC biomaGUNE , Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain.
Cyrille
C
Hamon
Bionanoplasmonics Laboratory, CIC biomaGUNE , Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain.
Sergey M
SM
Novikov
Bionanoplasmonics Laboratory, CIC biomaGUNE , Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain.
Leonardo
L
Scarabelli
Department Teoría de la Señal y Comunicaciones, University of Vigo , 36301 Vigo, Spain.
Diego M
DM
Solís
EMAT-University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Thomas
T
Altantzis
EMAT-University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Sara
S
Bals
Department Tec. Computadoras y Comunicaciones, University of Extremadura , 10003 Cáceres, Spain.
José M
JM
Taboada
Department Teoría de la Señal y Comunicaciones, University of Vigo , 36301 Vigo, Spain.
Fernando
F
Obelleiro
Bionanoplasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain; Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain.
Luis M
LM
Liz-Marzán
MLFMA; SERS; electron tomography; gold nanorods; method of moments; supercrystal; superlattice; surface enhanced Raman scattering