Collective Plasmonic Properties in Few-Layer Gold Nanorod Supercrystals

Abstract

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.

Nucleation of Amyloid Oligomers by RepA‐WH1‐Prionoid‐Functionalized Gold Nanorods

“…Additionally,w eu sed SERS spectroscopy to explore the transition from a-helix to b-sheet conformation (a signature for amyloidogenesis) in the oligomers obtained after the incubation of H6-RepA-WH1(A31V) with AuNRs.T he SERS spectra of the native proteins and their oligomers were obtained using citrate-coated AuNPs (60 nm Ø) (Figure 3A,s ee the Supporting Information), because of their high performance and plasmonic efficiency in SERS when aggregated on as ubstrate. [21] SERS spectra were collected using 785 nm laser light as the excitation source,a tl ow intensity (1.4 mWcm À2 )toavoid damaging the samples.Under such conditions,the typical band broadening characteristic of the Raman spectra of proteins was observed. [22] SERS spectra were obtained for the native protein and at the initial (1 day) and final (22 days) stages of oligomerization.…”

SQUEEZING MAXWELL'S EQUATIONS INTO THE NANOSCALE (Invited Paper)

“…It has become a powerful spectroscopy technique for the ultrasensitive detection of a variety of organic molecules at low concentrations [23,64]. Currently, much effort is being put in devising pathways that allow for the detection of small inorganic molecules and ions too [65].…”

“…They enable the accurate simulation of larger plasmonic systems, assisting in the interpretation of experimental results [22]. They can also provide a priori information that reliably predicts the optical response from complex plasmonic assemblies, aiding the devise of new systems and increasing the possibilities for new fruitful discoveries [23].…”

“…This methodology was applied for the solution of problems such as the design of nanoantennas [33,34] and optical wireless interconnects [35]. But among all the possible applications, we have concerned ourselves especially with biosensing, and particularly with surface enhanced Raman scattering (SERS) based spectroscopy [23,[36][37][38].…”

Individually Silica‐Embedded Gold Nanorod Superlattice for High Thermal and Solvent Stability and Recyclable SERS Application

“…[1][2][3][4][5] This tunability of GNRs can be further enriched by collective plasmon coupling through the formation of periodic arrays of GNRs, [6,7] and thus provides potential applications such as sensors, [8][9][10][11][12][13] broadband absorbers, [14] plasmonic catalysts, [15] and other plasmonic devices. [1][2][3][4][5] This tunability of GNRs can be further enriched by collective plasmon coupling through the formation of periodic arrays of GNRs, [6,7] and thus provides potential applications such as sensors, [8][9][10][11][12][13] broadband absorbers, [14] plasmonic catalysts, [15] and other plasmonic devices.…”