Blaudeck, Thomas and Zenkevich, Eduard I. and Abdel-Mottaleb, Mohamed and Szwaykowska, Klementyna and Kowerko, Danny and Cichos, Frank and von Borczyskowski, Christian (2012) Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules. ChemPhysChem, 13 (4). pp. 959-972. ISSN 1439-4235 http://resolver.caltech.edu/CaltechAUTHORS:20120501-084329044
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Functional dye molecules, such as porphyrins, attached to CdSe quantum dots (QDs) through anchoring meso-pyridyl substituents, form quasi-stable nanoassemblies. This fact results in photoluminescence (PL) quenching of the QDs both due to Förster resonance energy transfer (FRET) and the formation of non-radiative surface states under conditions of quantum confinement (non-FRET). The formation process is in competition with the ligand dynamics. At least two timescales are found for the formation of the assemblies: 1) one faster than 60 s attributed to saturation of empty attachment sites and 2) one slower than 600 s, which is attributed to a reorganisation of the tri-n-octylphosphine oxide (TOPO) ligand shell. Finally, this process results in almost complete exchange of the TOPO shell by porphyrin dye molecules. Following a Stern–Volmer analysis, we established a microscopic description of PL quenching and assembly formation. Based on this formalism, we determined the equilibrium constant for assembly formation between QDs and the pyridyl-functionalised dye molecules to be K ≈ 10^5 - 10^7 M^(−1), which is several orders of magnitude larger than that of the TOPO ligands. Our results give additional insights into the non-FRET PL quenching processes involved and show that the QD surface is inhomogeneous with respect to the involved attachment and detachment processes. In comparison with other methods, such as NMR spectroscopy, the advantage of our approach is that ligand dynamics can be investigated at extremely low ratios of dye molecules to QDs.
|Additional Information:||© 2012 Wiley-VCH Verlag GmbH & Co. Received: September 16, 2011. Published online on December 23, 2011. We acknowledge financial support by the Volkswagen foundation (Priority program “Physics, Chemistry and Biology with Single Molecules”, grant I/79435 to T.B. and M.A.-M.), the German Science Foundation (DFG, Graduate College 829 to T.B.), INTAS (grant R.03-05-4540 to E.I.Z.), BRFFI (grant ϕ10CO-005: E.I.Z.), and the German Academic Exchange Service (DAAD, grant 325 to E.I.Z. and RISE program 2005 to K.S.).|
|Subject Keywords:||FRET; ligand effects; photoluminescence quenching; quantum dots; self-assembly; semiconductors|
|Official Citation:||Blaudeck, T., Zenkevich, E. I., Abdel-Mottaleb, M., Szwaykowska, K., Kowerko, D., Cichos, F. and von Borczyskowski, C. (2012), Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules. ChemPhysChem, 13: 959–972. doi: 10.1002/cphc.201100711|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||01 May 2012 16:18|
|Last Modified:||01 May 2012 16:18|
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