Abstract
This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polymer film containing CdTe/CdS quantum dots leads to a significant decrease in the photoluminescence intensity together with the “blue shift” of the photoluminescence peak energy associated with quantum dot photooxidation. The mechanisms of the CdTe/CdS core/shell quantum dot photooxidation and photomodification in a polymer matrix are discussed. We have found a correlation between the photostability of the quantum dots and the CdS shell thickness as well as the ratio of core elements.
Highlights
Semiconductor nanocrystals or quantum dots (QDs) possess different optical, chemical, and electrical properties from the bulk materials due to quantum confinement effects
The photomodification of QDs appears as the significant increase of the Pl integral intensity while the photooxidation is accompanied by the decrease of the Pl intensity and “blue shift” of the Pl energy (Fig. 1)
The photooxidation and photomodification of the CdTe/CdS quantum dots embedded in the polymer matrix has been investigated
Summary
Semiconductor nanocrystals or quantum dots (QDs) possess different optical, chemical, and electrical properties from the bulk materials due to quantum confinement effects. QDs are highly luminescent materials with size-dependent emission and absorption spectra [1,2,3]. They can be used as active materials in optical and optoelectronic devices such as optical switches, sensors, and lasers [4,5,6]. A special attention should be paid to solid composites of QDs which are functional materials for luminescence solar light concentrators and spectrum converters [10,11,12,13] that are more effective and photostable than those containing organic dyes. The CdTe/CdS QDs are especially interesting in terms of creating luminescence light concentrators because they can be prepared in large quantity in water and have a high fluorescence quantum yield [14]. CdTe/CdS QDs in aqueous solution have a large effective surface charge that allows their implementation in a polymer matrix with the use of highly flexible and inexpensive layer-by-layer electrostatic assembly [15]
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