White-emitting conjugated polymer nanoparticles with cross-linked shell for mechanical stability and controllable photometric properties in color-conversion LED applications

Date
2011
Advisor
Instructor
Source Title
ACS Nano
Print ISSN
1936-0851
Electronic ISSN
1936-086X
Publisher
Volume
5
Issue
4
Pages
2483 - 2492
Language
English
Type
Article
Journal Title
Journal ISSN
Volume Title
Abstract

We report on the synthesis and characterization of water-dispersible, mechanically stable conjugated polymer nanoparticles (CPNs) in shelled architecture with tunable emission and controllable photometric properties via cross-linking. Using a reprecipitation method, whiteemitting polymer nanoparticles are prepared in different sizes by varying the concentration of polymer; the emission kinetics are tuned by controlling the shell formation. For this purpose, polyfluorene derivatives containing azide groups are selected that can be decomposed under UV light to generate very reactive species, which opportunely facilitate the inter- and intra-cross-linking of polymer chains to form shells. Nanoparticles before and after UV treatment are characterized by various techniques. Their size and morphologies are determined by using dynamic light scattering (DLS) measurements and imaging techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM). For optical characterization, UV vis and steady-state and timeresolved fluorescent spectroscopies are performed. Solid-state behaviors of these CPNs are also investigated by forming films through drop-casting. Moreover, the photometric calculations are also performed for films and dispersions to determine the color quality. A device has been constructed to show proof-of-principle white light generation from these nanoparticles. Additionally, mechanical stability studies are performed and demonstrated that these nanoparticles are indeed mechanically stable by removing the solvent after cross-linking using a freeze-dryer and redispersing in water and THF. Optical and imaging data confirm that the redispersed particles preserve their shapes and sizes after cross-linking.

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Book Title
Keywords
Color conversion, Conjugated polymer nanoparticles, Cross-linked shell, White light emission, Azide group, Before and after, Color conversions, Color quality, Conjugated polymer nanoparticles, Cross-linked shells, Different sizes, Drop-casting, Emitting polymers, Imaging data, Mechanically stable, Optical characterization, Photometric properties, Polyfluorene derivative, Polymer chains, Polymer nanoparticles, Proof of principles, Reactive species, Reprecipitation methods, SEM, Shell formation, State behavior, Time-resolved fluorescent spectroscopy, Tunable emissions, UV light, UV treatment, Water dispersible, White light emission, White-light generation, Atomic force microscopy, Casting, Color, Dynamic light scattering, Imaging techniques, Light emission, Mechanical properties, Mechanical stability, Nanoparticles, Photometry, Scanning electron microscopy, Shells (structures), Conjugated polymers
Citation
Published Version (Please cite this version)