Semiconductor Bowtie Nanoantenna from Coupled Colloidal Quantum Dot Molecules

TL;DR

This paper reports the synthesis of the smallest colloidal quantum dot bowtie nanoantenna, demonstrating enhanced polarized emission and localized electric-field hotspots useful for sensing and photocatalysis.

Contribution

It introduces a novel bottom-up fabrication method for quantum dot bowtie nanoantennas with functional optical and catalytic properties.

Findings

Enhanced emission polarization along the bowtie axis.

Formation of an electric-field hotspot at the bowtie center.

Selective light-induced photocatalytic metal growth at the hotspot.

Abstract

Top-down fabricated nanoantenna architectures of both metallic and dielectric materials demonstrated powerful functionalities for Raman and fluorescence enhancement with relevance to single molecule sensing, while inducing directionality of chromophore emission with implications for single photon sources. Herein, we synthesize the smallest bowtie nanoantenna by selective tip-to-tip fusion of two tetrahedral colloidal quantum dots (CQDs) forming a dimer. While the tetrahedral monomers emit non-polarized light, the bowtie architecture manifests nanoantenna functionality of enhanced emission polarization along the bowtie axis as predicted theoretically and revealed by single particle spectroscopy. Theory also predicts the formation of an electric-field hotspot at the bowtie epicenter. This is utilized for selective light induced photocatalytic metal growth at that location, unlike growth on the free tips in dark conditions thus demonstrating the bowtie dimer functionality as a photochemical reaction center. Our findings pave a path for additional bottom-up bowtie architectures applicable in optics, sensing and photocatalysis.