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Updated: Jan 1, 2026
12:57
Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection
Published on: October 13, 2017
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Exciton Coherence Length and Dynamics in Graphene Quantum Dot Assemblies.
Varun Singh1,2, Marija R Zoric1,2, George N Hargenrader1,2
1Department of Chemistry , University of Illinois at Chicago , 845 West Taylor Street , Chicago , Illinois 60607 , United States.
The Journal of Physical Chemistry Letters
|December 18, 2019
Summary
Exciton delocalization in graphene quantum dots (HBC and CQD) was studied. Hexabenzocoronene (HBC) showed longer exciton diffusion lengths (16 nm) compared to carbon quantum dots (CQD) (3 nm).
Area of Science:
- Materials Science
- Physical Chemistry
- Nanotechnology
Background:
- Graphene quantum dots (GQDs) are promising nanomaterials for optoelectronic applications.
- Understanding exciton behavior in GQD assemblies is crucial for device performance.
- Hexabenzocoronene (HBC) and carbon quantum dots (CQDs) represent distinct GQD architectures.
Purpose of the Study:
- To investigate and compare exciton size and dynamics in ordered HBC fibers and less-ordered CQD assemblies.
- To determine the influence of GQD size and assembly structure on exciton delocalization and diffusion.
Main Methods:
- Bottom-up chemical synthesis of HBC (42 C atoms) and CQD (78 C atoms).
- Characterization of GQD assembly using UV/vis spectroscopy, X-ray scattering, and electron microscopy.
- Time-resolved laser spectroscopy and exciton-exciton annihilation measurements to study exciton dynamics.
Main Results:
- HBC formed long, ordered fibers, while CQDs exhibited poor assembly.
- Excitons delocalized over approximately 1-2 molecular units in both systems at early times (∼100 fs).
- Exciton diffusion lengths were measured as 16 nm for HBC and 3 nm for CQD.
Conclusions:
- The confined nature of excitons in carbon-based materials limits early-time delocalization.
- Ordered assembly of HBC significantly enhances exciton diffusion compared to disordered CQDs.
- Graphene quantum dot assembly structure is a critical factor for efficient exciton transport.
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