Mapping nanoscale hotspots with single-molecule emitters assembled into plasmonic nanocavities using DNA origami

TL;DR

This study demonstrates precise placement of single molecules within plasmonic nanocavities using DNA origami, enabling detailed mapping of optical modes with nanometer resolution and significant enhancement of emission.

Contribution

The paper introduces a DNA-origami based self-assembly method for positioning single emitters in nanocavities with sub-5nm accuracy, allowing nanoscale optical mode mapping.

Findings

Achieved >4000x emission enhancement with high quantum yield.

Mapped local density of optical states with ±1.5 nm resolution.

Modified plasmon resonance by positioning single molecules.

Abstract

Fabricating nanocavities in which optically-active single quantum emitters are precisely positioned, is crucial for building nanophotonic devices. Here we show that self-assembly based on robust DNA-origami constructs can precisely position single molecules laterally within sub-5nm gaps between plasmonic substrates that support intense optical confinement. By placing single-molecules at the center of a nanocavity, we show modification of the plasmon cavity resonance before and after bleaching the chromophore, and obtain enhancements of $\geq4\times10^3$ with high quantum yield ($\geq50$%). By varying the lateral position of the molecule in the gap, we directly map the spatial profile of the local density of optical states with a resolution of $\pm1.5$ nm. Our approach introduces a straightforward non-invasive way to measure and quantify confined optical modes on the nanoscale.