Coupling effects in QD dimers at sub-nanometer interparticle distance

Carlo Nazareno Dibenedetto,Annamaria Panniello,Elisabetta Fanizza,Yuval Kolodny,Roberto Comparelli,Shira Yochelis,Sergei Remennik,Yossi Paltiel,Maria Lucia Curri,Angela Agostiano,Marinella Striccoli,Rosaria Brescia,Nicoletta Depalo

doi:10.1007/s12274-020-2747-3

Abstract

Currently, intensive research efforts focus on the fabrication of meso-structures of assembled colloidal quantum dots (QDs) with original optical and electronic properties. Such collective features originate from the QDs coupling, depending on the number of connected units and their distance. However, the development of general methodologies to assemble colloidal QD with precise stoichiometry and particle-particle spacing remains a key challenge. Here, we demonstrate that dimers of CdSe QDs, stable in solution, can be obtained by engineering QD surface chemistry, reducing the surface steric hindrance and favoring the link between two QDs. The connection is made by using alkyl dithiols as bifunctional linkers and different chain lengths are used to tune the interparticle distance from few nm down to 0.5 nm. The spectroscopic investigation highlights that coupling phenomena between the QDs in dimers are strongly dependent on the interparticle distance and QD size, ultimately affecting the exciton dissociation efficiency.

Highlights

Research on nanomaterials and their technological application is rapidly increasing in the last few years
The spectroscopic investigation highlights that coupling phenomena between the quantum dots (QDs) in dimers are strongly dependent on the interparticle distance and QD size, affecting the exciton dissociation efficiency
The dimeric structures are fabricated by using bifunctional alkyl ligands with an A-Y-A structure, able to directly replace the pristine ligands at the CdSe QDs surface and connect the two QDs by means of the “A” head group, being “Y” the alkyl chain acting as a spacer to define the interparticle distance

Summary

Introduction

Research on nanomaterials and their technological application is rapidly increasing in the last few years. Colloidal semiconductor quantum dots (QDs) are used for application in a plethora of photonic [1] and optoelectronic [2, 3] devices, ranging from commercial TV displays [4] to LEDs [5], solar cells [6, 7], miniaturized sensors [8], biochips [9], etc. Most of such optoelectronic and sensing applications require an efficient coupling among the QDs deposited in solid disordered aggregates, with limited success. The electronic structure, and the optical properties of the QDs, strongly depends on the surface

Methods

Results

Conclusion