Electrically Controlled Plasmonic Behavior of Gold Nanocube@Polyaniline Nanostructures: Transparent Plasmonic Aggregates

Abstract

We demonstrate the electrically controlled and reversible plasmonic signature of hybrid polymer–metal nanostructures composed of core/shell nanostructures: gold nanocubes (AuNCs) coated with electrochromic polyaniline (PANI) shells. A reversible tuning of the localized surface plasmon resonance (LSPR) peak of the AuNC core was obtained by applying an electrical potential that caused a reversible oxidation state change in the electroactive PANI nanoshell. A significant shift of the main LSPR peak was achieved with high reversibility and electrochemical stability due to the interplay of the local decay of the electromagnetic field and the controlled thickness of the surrounding polymer shell. Here, the PANI shell acts as an electroactive medium as well as a physical spacer to prevent uncontrollable plasmonic coupling. The most efficient LSPR shift can be induced by the refractive index change of nanoscale PANI shell thickness lower than the electromagnetic field decay length of the given gold nanoparticles. Single particle studies showed that coupling of plasmon resonances of densely packed nanocubes with thicker PANI shells was prevented and the extinction signature of individual core/shell nanocubes remained mostly unchanged after their assembly into densely packed aggregates. Therefore, these core/shell structures could preserve the original plasmonic signature of individual nanostructure by damping plasmonic coupling between AuNC cores.

Active Electrochemical Plasmonic Switching on Polyaniline‐Coated Gold Nanocrystals

“…The results indicate that the PANI shells coated on the Au nanocrystal samples in our study are thick enough for realizing large plasmon shifts during electrochemical switching. This point is also supported by a recent work on the plasmonic switching of (Au nanocube)@PANI nanostructures, where the plasmonic shift increases largely with the PANI shell thickness when the thickness is below 13 nm, but it only increases slightly when the PANI shell is thickened above 13 nm.…”

“…Three types of colloidal Au nanocrystals, namely, NSs, NRs, and NBPs, were synthesized by the seed‐mediated growth method . PANI coating on the Au nanocrystals were realized by surfactant‐assisted chemical oxidative polymerization . All of the preparation, characterization, and measurement details are provided in the Supporting Information.…”

From active plasmonic devices to plasmonic molecular electronics

“…(a) Extinction UV–visible spectra of Au nanocubes with PANi (26 nm) core–shell nanostructures at various voltages with 0.5 mol L −1 NaCl in 0.01 mol L −1 HCl solution (adapted from reference ; copyright 2016 American Chemical Society). (b) Optical transmission spectra of PolyProDOT coated Al‐nanoslit structures with values of the slit period 240, 270, 300, 330, 360 and 390 nm along with corresponding optical micrographs of device areas imaged in transmission (adapted from reference ; copyright 2016 Nature).…”

“…29 Gold nanocubes coated with electrochromic PANi shells and deposited on an ITO electrode were also reported. 30 The LSPR peak of the gold nanocube core was reversibly tuned by applying an electrical potential that caused a reversible redox change in the PANi nanoshell ( Fig. 2(a)).…”

Poly(N‐octadecylaniline) Synthesized at the Air‐Water Interface: Aligned Nanofibers and Gold Nanocomposite Assembly via the Langmuir‐Blodgett Technique

“…Composites of π‐conjugated polymers and noble metal nanoparticles with localized surface plasmon resonance (LSPR) extinction, exhibit enhancement of the unique characteristics of each, and synergistic effects ,. PANI−Au is perhaps the most extensively explored system, finding use as sensor, nonvolatile memory and actuator, as well as displaying attributes like tunable LSPR response and plasmonic hot hole generation . Interesting morphologies of PANI include helical and chiral ones, induced by chiral monomers and counterions, or mesostructures …”