Solvent-Assisted Self-Assembly of Gold Nanorods into Hierarchically Organized Plasmonic Mesostructures

Abstract

Plasmonic supercrystals and periodically structured arrays comprise a class of materials with unique optical properties that result from the interplay of plasmon resonances, as well as near- and far-field coupling. Controlled synthesis of such hierarchical structures remains a fundamental challenge, as it demands strict control over the assembly morphology, array size, lateral spacing, and macroscale homogeneity. Current fabrication approaches involve complicated multistep procedures lacking scalability and reproducibility, which has hindered the practical application of plasmonic supercrystal arrays. Herein, these challenges are addressed by adding an organic solvent to achieve kinetic control over the template-assisted colloidal assembly of nanoparticles from aqueous dispersion. This method yields highly regular periodic arrays, with feature sizes ranging from less than 200 nm up to tens of microns. A combined experimental/computational approach reveals that the underlying mechanism is a combination of the removal of interfacial surfactant micelles from the particle interface and altered capillary flows. Assessing the efficacy of such square arrays for surface-enhanced Raman scattering spectroscopy, we find that a decrease of the lattice periodicity from 750 nm down to 400 nm boosts the signal by more than an order of magnitude, thereby enabling sensitive detection of analytes, such as the bacterial quorum sensing molecule pyocyanin, even in complex biological media.

Multiplex SERS Detection of Metabolic Alterations in Tumor Extracellular Media

“…[ 23,24 ] We tested two types of plasmonic substrates, which were previously optimized for the detection of bacterial Quorum sensing signaling molecules. [ 25,26 ] Although both strategies involve the deposition of 30 nm spherical Au nanoparticles (AuNPs) on glass substrates, the different methodologies (see “Experimental Section” for detailed descriptions) result in radically different distributions of AuNPs on the substrate. [ 25,26 ] On the one hand, the standard polyelectrolyte layer‐by‐layer (LbL) assembly methodology was used to produce homogeneous (disordered) multilayers of AuNPs on a glass cover slip (a schematic description of the fabrication is shown in Figure S1a in the Supporting Information).…”

“…[ 25,26 ] Although both strategies involve the deposition of 30 nm spherical Au nanoparticles (AuNPs) on glass substrates, the different methodologies (see “Experimental Section” for detailed descriptions) result in radically different distributions of AuNPs on the substrate. [ 25,26 ] On the one hand, the standard polyelectrolyte layer‐by‐layer (LbL) assembly methodology was used to produce homogeneous (disordered) multilayers of AuNPs on a glass cover slip (a schematic description of the fabrication is shown in Figure S1a in the Supporting Information). On the other hand, a recently developed template‐assisted self‐assembly process resulted in the formation of hierarchical nanostructured substrates, comprising square arrays of hexagonally packed AuNP clusters (see Figure a), so‐called plasmonic superlattices (a graphical representation of the fabrication procedure is shown in Figure S1b in the Supporting Information).…”

DNA‐Origami‐Based Assembly of Au@Ag Nanostar Dimer Nanoantennas for Label‐Free Sensing of Pyocyanin

“…The array of Au@SiO 2 supercrystal developed by Bodelon et al [56] . and Au nanorods by Hanske et al [57] . yielded 10 −14 M and 10 −12 M sensitivity respectively, but the fabrication of such supercrystal and assembled SERS substrates required complex, expensive and time‐consuming lithographic technique.…”

Quantifying Strain and Dislocation Density at Nanocube Interfaces after Assembly and Epitaxy

“…Self-assembly of nanocrystals and successive epitaxy by either dissolving the capping ligands in a suitable solvent or via a chemical trigger has emerged as a promising route to make single crystals with complex nanoscale geometries. 1 − 10 This approach is very flexible, including variants where particles are both assembled and epitaxially connected in solution—usually called oriented attachment 7 , 9 , 11 − 15 —or where assembly first occurs at an interface (liquid–liquid, liquid–solid, or liquid–vapor) 1 , 9 , 10 , 16 − 25 followed by the epitaxy step (thermal, chemical, or optical). 3 , 4 , 10 , 15 , 26 − 30 Interfacial assembly via aforementioned techniques can lead to 2D films with nanoscale patterns determined by the shape and surface energetics of the particle, such as a 2D honeycomb lattice, or to more complex nanopatterns formed by capillary assembly.…”