Development of Rotaxanes as E-Field-Sensitive Superstructures in Plasmonic Nano-Antennas

Abstract

We present the concept of electrostatic field driven supramolecular translation within electrically connected plasmonic nano-antennas. The antenna serves as anchoring point for the mechanically interlocked molecules, as electrode for the electrostatic field, and as amplifier of the antenna-enhanced fluorescence. The synthesis of a push-pull donor-π-acceptor chromophore with optical properties aligned to the antenna resonance is described and its immobilization on the surface demonstrated. Photoluminescence experiments of the chromophore on a gold nanoantenna are shown, highlighting the molecule-antenna coupling and resulting emission intensity increase. The successful synthesis of an electrostatic field sensitive [2]rotaxane in water is described and the tightrope walk between functionality and water solubility is illustrated by unsuccessful designs. In solution, enhanced fluorescence quantum yield is observed for the chromophore comprised in the mechanically interlocked [2]rotaxane in water and DMSO compared to the reference rod, ideal for future experiments in plasmonic nano-antennas.

Site-selective functionalization of in-plane nanoelectrode-antennas

“…1). 35 A dodecaethyleneglycol chain with a protected terminal thiol group is intended to act as an anchor to the gold (111) surface. The long chain ensures sufficient emitter-metal distance and minimizes quenching once the molecules are immobilized upright standing on the gold.…”

“…Once immobilized with a clearly defined orientation, such molecules can perform defined and directed motions controlled by the nanoelectrodes. 35…”