Tuning Quantum-Dot Organization in Liquid Crystals for Robust Photonic Applications

Mesogenic ligands have the potential to provide control over the dispersion and stabilization of nanoparticles in liquid crystal (LC) phases. The creation of such hybrid materials is an important goal for the creation of soft tunable photonic devices, such as the LC laser. Herein, we present a compa...

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Bibliographic Details
Published in:Chemphyschem 2014-05, Vol.15 (7), p.1413-1421
Main Authors: Rodarte, Andrea L., Nuno, Zachary S., Cao, Blessing H., Pandolfi, Ronald J., Quint, Makiko T., Ghosh, Sayantani, Hein, Jason E., Hirst, Linda S.
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Fluorescence
ligand exchange
Ligands
Liquid crystals
Materials science
Nanoscale materials and structures: fabrication and characterization
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Other topics in nanoscale materials and structures
Photoluminescence
Physics
Quantum dots
Structure of solids and liquids
crystallography
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Summary:Mesogenic ligands have the potential to provide control over the dispersion and stabilization of nanoparticles in liquid crystal (LC) phases. The creation of such hybrid materials is an important goal for the creation of soft tunable photonic devices, such as the LC laser. Herein, we present a comparison of isotropic and mesogenic ligands attached to the surface of CdSe (core‐only) and CdSe/ZnS (core/shell) quantum dots (QDs). The mesogenic ligand′s flexible arm structure enhances ligand alignment, with the local LC director promoting QD dispersion in the isotropic and nematic phases. To characterize QD dispersion on different length scales, we apply fluorescence microscopy, X‐ray scattering, and scanning confocal photoluminescent imaging. These combined techniques demonstrate that the LC‐modified QDs do not aggregate into the dense clusters observed for dots with simple isotropic ligands when dispersed in liquid crystal, but loosely associate in a fluid‐like droplet with an average interparticle spacing >10 nm. Embedding the QDs in a cholesteric cavity, we observe comparable coupling effects to those reported for more closely packed isotropic ligands. Dots with liquid‐crystalline ligands are synthesized and dispersed in the nematic and cholesteric phases at different concentrations. Fluorescence microscopy, scanning confocal photoluminescence microscopy, and X‐ray diffraction reveal details of the quantum‐dot (QD) cluster packing. Spectroscopic measurements demonstrate the applicability of the QDs for photonic applications.
ISSN:1439-4235
1439-7641
DOI:10.1002/cphc.201301007