Ligand exchange dynamics and temperature effects upon formation of nanocomposites based on semiconductor CdSe/ZnS quantum dots and porphyrins: Ensemble and single object measurements
2012 (English)In: Macroheterocycles, ISSN 1998-9539, Vol. 5, no 2, 98-114 p.Article in journal (Refereed) Published
Dye molecules with pyridyl side substituents (porphyrins and heterocyclic perylene diimides) coordinatively attached to semiconductor CdSe/ZnS quantum dots (QDs) surface form quasi-stable QD-Dye nanocomposites of various geometry in the competition with capping molecules (tri-n-octyl phosphine oxide or long chain amines) exchange. This results in photoluminescence (PL) quenching of the QDs both due to Foerster resonance energy transfer and formation of non-radiative surface states. QD surface is inhomogeneous with respect to the involved attachment and detachment processes. The formation of QD-Porphyrin nanocomposites is realized at least two time scales (60 and 600 s), which is attributed to a reorganisation of tri-n-octylphosphine oxide capping shell. In a low temperature range of 220÷240 K related changes in QD absorption and emission reveal a phase transition of the capping shell (tri-n-octyl phosphine oxide and amine). In QD-Dye nanocomposites, this phase transition is enhanced considerably by only a few attached dye molecules and has impact on the QD core structure followed by changes of PL quenching and exciton-phonon coupling. A combination of ensemble and single molecule spectroscopy of QD-Dye nanocomposites reveals that few or even only one attached dye molecule change the surface distribution and energy of dye related surface trap states considerably. © ISUCT Publishing.
Place, publisher, year, edition, pages
2012. Vol. 5, no 2, 98-114 p.
Fluorescence resonant energy transfer; Ligand dynamics; Photoluminescence quenching; Porphyrins; Self-assembly; Semiconductor quantum dots; Single objects spectroscopy; Surface traps; Temperature surface phase transition
Engineering and Technology Natural Sciences
IdentifiersURN: urn:nbn:se:liu:diva-100947DOI: 10.6060/mhc2012.120571zOAI: oai:DiVA.org:liu-100947DiVA: diva2:664510