While time-resolved luminescence spectroscopy is commonly used as a quantitative tool for the analysis of the dynamics of photoexcitation in colloidal semiconductor quantum dots, the interpretation of the virtually ubiquitous nonexponential decay profiles is frequently ambiguous, because the assumption of multiple discrete exponential components with distinct lifetimes for resolving the decays is often arbitrary. Here, an interpretation of the roomtemperature luminescence decay of CdSe/ZnS semiconductor quantum dots in colloidal solutions is presented based on the Kohlrausch relaxation function. It is proposed that the decay can be understood by using the concept of Förster resonance energy transfer (FRET) assuming that the role of acceptors of photoexcitation energy is played by highfrequency anharmonic molecular vibrations in the environment of the quantum dots. The term EVFRET (ElectronicVibrational Förster Resonance Energy Transfer) is introduced in order to unequivocally refer to this energy transfer process.Since the seminal works reporting a quantum size effect in semiconductor nanocrystals in 1981 [1] and luminescence from semiconductor colloidal solutions in 1982 [2,3] colloidal semiconductor quantum dots have become the subject of intensive experimental and theoretical research due to their wide range of size-tunable properties, notably optical properties [4-6] which make them potential candidates for applications in areas such as biolabeling, bioimaging, bio-and chemo-sensing, theranostics, lasing, photovoltaic energy conversion, photodetection, and light-emitting diodes among others [7][8][9][10][11][12][13][14][15].The understanding of the principles governing luminescence in colloidal quantum dot systems is necessary in order to envisage ways of controlling their properties. At the same time, the room-temperature luminescence decays of quantum dots are typically nonexponential, [7,[16][17][18] which may lead to ambiguity in their interpretation as the assumption of multiple discrete exponential components with distinct lifetimes for resolving the decays is often arbitrary. Indeed, pre-exponential factors and decay times in nonexponential luminescence decays have clear physical meaning only in the simplest cases [19]. On the other hand, while the intrinsic exciton dynamics of CdSe colloidal semiconductor quantum dots, by far the most extensively investigated quantum dot system, is generally understood [20,21], the same cannot be said about the effects of extrinsic factors, such as capping layer or colloidal solution environment, which are expected to play a prominent role in the photophysical processes in those systems [22].The Kohlrausch or stretched exponential relaxation function, exp [−(t/τ ) β ], where 0 < β ࣘ 1 and τ has the dimensions of time, has been in use for over 150 years to describe relaxation processes in electronic and molecular systems [23], including luminescence decay in condensed matter, most remarkably by Alfred Werner in 1907 and Theodor Förster in 1949 [24]. The stretching p...

A novel homogeneous composite material, consisting of luminescent CdSe/ZnS quantum nanorods, embedded in the nematic liquid crystal 5CB, has been prepared. Liquid crystal cells and free-standing stretched polymer films incorporating this composite material were characterized using polarized micro-photoluminescence and electro-optical measurements under an applied electric field. A liquid crystal induced, macroscopic orientation of the nanorods in a thin layer of the material has been demonstrated. A conventional liquid crystal cell, filled with this composite, exhibits 40% modulation of the nanorod's photoluminescence intensity when subjected to an external electric field. These results indicate that quantum nanorods may have practical applications in photonic devices.

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