Plasmonic Nanostructure Engineering with Shadow Growth

Abstract

Physical shadow growth is a vacuum deposition technique that permits a wide variety of 3D‐shaped nanoparticles and structures to be fabricated from a large library of materials. Recent advances in the control of the shadow effect at the nanoscale expand the scope of nanomaterials from spherical nanoparticles to complex 3D shaped hybrid nanoparticles and structures. In particular, plasmonically active nanomaterials can be engineered in their shape and material composition so that they exhibit unique physical and chemical properties. Here, the recent progress in the development of shadow growth techniques to realize hybrid plasmonic nanomaterials is discussed. The review describes how fabrication permits the material response to be engineered and highlights novel functions. Potential fields of application with a focus on photonic devices, biomedical, and chiral spectroscopic applications are discussed.

Intrinsic Optical Properties and Emerging Applications of Gold Nanostructures

“…[101] In particular, direct fabrication of chiral AuNPs with helical or twisted structures has attracted significant attention in recent years. [102,103] Achiral gold nanoparticles are also self-assembled into chiral geometries to produce chiral gold nanostructures. [104,105] The helical arrangement of AuNPs offers an effective way to introduce chirality via strong interparticle dipole-dipole interaction (i.e., plasmon-plasmon interaction) at a very close distance between achiral AuNPs, which is much smaller than the size of AuNPs.…”

“…Inspired by the importance of optical chirality in photonics, biochemistry, [140] medicine, and catalysis, substantial efforts have been made to construct mirror asymmetry of AuNPs or their assemblies in helical or twisted structures endowed with intrinsic chirality. [57,141] Various nanofabrication approaches have been applied to directly create chiral gold nanostructures with well-defined structures, including direct-laser writing and electroplating, [142] shadow deposition, [103] and directed growth using chiral molecules or micelles. [143] Various chiral templates, such as liquid crystals, peptides, and polymers, have been used to assemble achiral AuNPs, enabling the construction of asymmetric gold nanostructures.…”

Chiral Plasmonic Hybrid Nanostructures: A Gateway to Advanced Chiroptical Materials

“…These hybrids possess tunable optical, electric, magnetic, and mechanical properties and are currently receiving growing attention. [11] Chiral plasmonic hybrid nanostructures, an emerging class of chiral families, incorporate multiple engineerable compositions (e.g., semiconductors, metals, magnets) in an individual system, enabling novel chiral light-matter interactions. By coupling different physical quasiparticles, such as chiral plasmons, electron spin, and polarized photons, or particles at strongly confined length scales, these hybrids confer chiral light-matter interactions.…”

Plasmonic Nano‐Rotamers with Programmable Polarization‐Resolved Coloration

“…Here we demonstrate a wafer-scale "lithography-free" parallel fabrication scheme to realize 3D-shaped Mg nano-rotamers acting as a dual functional plasmonic architecture, allowing us to program both linear and circular polarization-resolved coloration, which is challenging to achieve otherwise. Using a physical shadow growth technique known as glancing angle deposition (GLAD), [30,31] we demonstrate controlled precise variations in the dihedral angles of an array of nano-rotamers across from achiral C 2v to various types of chiral C 2 symmetric structures. This engineering flexibility results in wafer-level polarization-resolved coloration for both linearly and circularly polarized lights, spanning from transparent to visible colors, opening up numerous possibilities for a wide range of nanophotonic applications.…”