Gold Nanoparticle Plasmonic Superlattices as Surface-Enhanced Raman Spectroscopy Substrates

Abstract

Metal colloids are of great interest in the field of nanophotonics, mainly due to their morphology-dependent optical properties, but also because they are high-quality building blocks for complex plasmonic architectures. Close-packed colloidal supercrystals not only serve for investigating the rich plasmonic resonances arising in strongly coupled arrangements but also enable tailoring the optical response, on both the nano- and the macroscale. Bridging these vastly different length scales at reasonable fabrication costs has remained fundamentally challenging, but is essential for applications in sensing, photovoltaics or optoelectronics, among other fields. We present here a scalable approach to engineer plasmonic supercrystal arrays, based on the template-assisted assembly of gold nanospheres with topographically patterned polydimethylsiloxane molds. Regular square arrays of hexagonally packed supercrystals were achieved, reaching periodicities down to 400 nm and feature sizes around 200 nm, over areas up to 0.5 cm. These two-dimensional supercrystals exhibit well-defined collective plasmon modes that can be tuned from the visible through the near-infrared by simple variation of the lattice parameter. We present electromagnetic modeling of the physical origin of the underlying hybrid modes and demonstrate the application of superlattice arrays as surface-enhanced Raman scattering (SERS) spectroscopy substrates which can be tailored for a specific probe laser. We therefore investigated the influence of the lattice parameter, local degree of order, and cluster architecture to identify the optimal configuration for highly efficient SERS of a nonresonant Raman probe with 785 nm excitation.

Engineering State‐of‐the‐Art Plasmonic Nanomaterials for SERS‐Based Clinical Liquid Biopsy Applications

“…a) Beveled gold triangular prism assembly via droplet evaporation. [54] Copyright 2018, American Chemical Society. Reproduced with permission.…”

“…[53] The chemical synthesis involves self-assembly of in situ-formed gold nanoparticles driven by solvophobic interactions between nanoparticles and solvent. [54] The whole fabrication process only requires 1 h. The supercrystals possess well-defined collective plasmon modes that can be tailored from visible through NIR regions by simple modification of the lattice parameter via specific polydimethylsiloxane patterns. [54] The whole fabrication process only requires 1 h. The supercrystals possess well-defined collective plasmon modes that can be tailored from visible through NIR regions by simple modification of the lattice parameter via specific polydimethylsiloxane patterns.…”

“…For example, electron-beam lithography has advantages in fabricating a wide range of 2D periodic geometries with ultrafine features, good reproducibility, and large-scale uniformity, such as the nanoantenna dimer arrays, [59] ordered nanopillars, [60] nanostar dimer arrays, [61] and 3D multipetal flower arrays. Recently, the construction of nanostructure arrays with uniform nanogaps (10-20 nm) has been engineered by many alternative time-and cost-effective technologies, including template-assisted assembly, [54] laser interference lithography, [63] and laser-assisted nanoreplication methods. Recently, the construction of nanostructure arrays with uniform nanogaps (10-20 nm) has been engineered by many alternative time-and cost-effective technologies, including template-assisted assembly, [54] laser interference lithography, [63] and laser-assisted nanoreplication methods.…”

Shaping Metallic Nanolattices: Design by Microcontact Printing from Wrinkled Stamps

“…Such properties can render these structures suitable candidates for sophisticated further applications, which comprise, e.g., the fields of biosensing, [ 7–9 ] information storage, [ 10,11 ] or optoelectronics. [ 12–14 ] Thereby, templating by surface patterns represents a popular method to obtain fine metallic nanostructures. Different types of advanced lithographic techniques have been utilized to fabricate functional surface patterns, such as photo‐, [ 15,16 ] electron‐beam or dip‐pen lithography, [ 6,17–20 ] self‐assembly patterns (SAPs) of (macro‐)molecules, [ 21–24 ] soft lithography and others.…”

Sensitive and Reliable SERS Substrates Based on Hierarchical Nanoparticle Arrays Fabricated by Confined Spheroidization

“…Here, inspired by the confinement effect and the fact that metal films can form spherical particles with larger surface area after high temperature annealing, we came up with the idea of ‘confined spheroidization'. Moreover, to our knowledge, 2D nanoparticle arrays have been fabricated widely mainly by self‐assembly, but reports about 3D ordered nanoparticle arrays are rare. Based on these considerations, a series of studies on confined spheroidization were carried out.…”