Detailed mechanism for the orthogonal polarization switching of gold nanorod plasmons

Abstract

In this work, we describe an electro-optic material capable of orthogonally switching the polarization of the localized surface plasmon resonance scattering of single gold nanorods, independent of their orientation. Liquid crystal samples are prepared in a sandwich configuration with electrodes arranged so that an applied voltage induces alignment-switching of the liquid crystal molecules covering individual gold nanorods. Due to the birefringence of the nematic liquid crystal, the reorientation in the nematic director alignment causes a change in the output polarization of the scattered light. We propose the underlying mechanism to be based on a homogeneous nematic to twisted nematic phase transition and provide support for it via Jones calculus by modelling the effect of ideally aligned homogeneous nematic and twisted nematic phases on polarized light transmitted through the sample. In the model, we include the effects of sample thickness and surface plasmon resonance wavelength, expressed in terms of the phase retardation, χ, on the observed output polarization. We find four distinctively different trends for the output polarization as a function of the incident polarization as χ is varied. Two of these cases provide reproducible orthogonal polarization switching of the surface plasmon resonance while maintaining a high degree of polarization. These results are verified experimentally with liquid crystal cells of different thicknesses. The deviation of the experimental samples from ideal behaviour can be explained by the inherent variations in the surface plasmon resonance maximum and local cell thickness.

Vivid, full-color aluminum plasmonic pixels

“…The colors of these pixels are determined by diffractive coupling and are tunable through a combination of nanorod length l, D x , and D y , resulting in bright, vivid RGB pixels compatible with additive color schemes. Because of the use of nanorods as the basic component, the signal is strongly polarized, making these Al plasmonic pixels compatible with liquid crystal switching technology (49)(50)(51). For display purposes, a viewing angle-dependent signal would be problematic but could be remedied by placing a diffusing layer on top of the pixel layer.…”

Single-Particle Plasmon Voltammetry (spPV) for Detecting Anion Adsorption

“…An underlying 2 nm Ti adhesion layer was first deposited to ensure good film quality. [36][37][38] In contrast to the weakinteractive relationship between nanoparticle plasmons and ITO, Au thin film plasmons and nanoparticle plasmons interact strongly to produce rich optical properties. 28-31, 36, 39-44 Also unlike the ITO substrate, anions readily adsorb to gold at anodic potentials [45][46][47] causing large changes in optical and electronic properties of the thin film.…”

“…The second substrate was composed of a 20 nm Au thin film evaporated onto a glass coverslip. An underlying 2 nm Ti adhesion layer was first deposited to ensure good film quality. − In contrast to the weak interactive relationship between nanoparticle plasmons and ITO, Au thin film plasmons and nanoparticle plasmons interact strongly to produce rich optical properties. − ,,− Also unlike the ITO substrate, anions readily adsorb to gold at anodic potentials − causing large changes in optical and electronic properties of the thin film. − Au nanoparticle monomers and chemically assembled dimers were deposited onto the two substrates, and surface ligands were chemically removed from the monomers and dimers to leave the nanoparticles in electrical contact with the substrates (Methods). The thin film substrates with attached Au nanoparticle monomers and dimers were then used as the working electrode in thin optically transparent three-electrode spectroelectrochemical cells (Figure A, Methods).…”

Tailored Surfaces/Assemblies for Molecular Plasmonics and Plasmonic Molecular Electronics

“…It is especially significant because both plasmonic and electric signals can be guided in the same metallic circuitry. The effects of integrating liquid crystals (LCs) with AuNPs (95), gold nanodots (96), gold nanorods (97,98), and nanohole arrays (99) were investigated. In all cases, the SPR depends on the applied voltage.…”