Time-resolved fluorescence and absence of Förster resonance energy transfer in ferroelectric liquid crystal-quantum dots composites

Abstract

The present article deals with the interaction of octadecylamine (ODA) capped cadmium selenide quantum dots (CdSe QDs) and two ferroelectric liquid crystals (FLCs) having different values of spontaneous polarization (Ps). The pristine FLCs and FLC-QDs composites have been investigated by using steady-state and time-resolved fluorescence spectroscopic techniques. Stokes shift and the preferred alignment of FLC molecules in the presence of QDs are found to depend on the secondary order parameter of FLCs (i.e. Ps). The secondary fluorescence emissions have been strongly influenced by the concentration of QDs. The Förster resonance energy Transfer (FRET) was absent in both the composites. This article discloses the role of various factors, like relative orientation, dipolar interaction between donor and acceptor and the proximity of QDs (>10 nm), which might be responsible for the absence of FRET. FLC-QDs composites do not form a new class of luminescent material though the fluorescence properties of host FLCs are tailored in the presence of QDs by means of the change in molecular alignment. The change in lifetimes of FLC-QDs composites has not been observed.