(260ax) Dual-Responsive Plasmonic Behavior of Gold Nanorods@PANI Core/Shell Nanostructures

Reversible tuning of plasmonic properties is becoming important to develop a new series of adaptable devices for plasmonic switches, modulators, and tunable lasers and tunable optical filters. Here, we demonstrate dual-responsive plasmonic systems consisting of gold nanorod (AuNR) cores and responsive polyaniline (PANI) shells. The plasmonic properties of AuNR@PANI core/shell nanostructures can reversibly modulated using two different stimuli: electrical potential and pH change. The PANI shell can change its oxidation and doping state between emeraldine salt (ES), emeraldine base (EB), and leucoemeraldine base (LB) depending on the surrounding chemical environments. The refractive indices of three different PANI states were obtained using spectroscopic ellipsometry, which showed that highest localized plasmonic resonance (LSPR) shift can be obtained by changing local pH surrounding AuNRs. Extremely high LSPR shift around 100 nm was achieved with very thin PANI shells (8 nm) by changing the pH environment. This highly sensitive AuNR@PANI core/shell nanostructures can potentially be used for a variety of applications including photovoltaics, nanophotonics, and optoelectronics.