Synthesis of tetrahedral quasi-type-II CdSe–CdS core–shell quantum dots

Abstract

Synthesis of colloidal nanocrystals of II-VI semiconductor materials has been refined in recent decades and their size dependent optoelectronic properties have been well established. Here we report a facile synthesis of CdSe-CdS core-shell heterostructures using a two-step hot injection process. Red-shifts in absorption and photoluminescence spectra show that the obtained quantum dots have quasi-type-II alignment of energy levels. The obtained nanocrystals have a heterostructure with a large and highly faceted tetrahedral CdS shell grown epitaxially over a spherical CdSe core. The obtained morphology as well as high resolution electron microscopy confirms that the tetrahedral shell have a zinc blende crystal structure. A phenomenological mechanism for the growth and morphology of the nanocrystals is discussed.

Deposition of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shells around CdSeTe alloyed core quantum dots: effects on optical properties

“…This occurs because the spatially indirect core-shell transition has a lower transition matrix element than the spatially direct transitions in the core. This is in contrast to type II QDs with a larger band offset in which the absorption spectrum of the QDs is evidently broadened with a long red tail and spatially indirect transitions prevail for QDs of larger shell thickness (18,32).…”

Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots

“…The shell thickness was determined by TEM analysis and comparison with TEM analysis of the core QDs. Details of the fabrication process are described elsewhere [16]. A typical TEM image of an ensemble of the CdSe cores and the CdSe-CdS core-shell QDs is shown in Figs.…”

Optical properties of CdSe nanoparticles synthesized by hot injection in air

“…al. under two different atmospheres [42]. In the first case, the synthesis was prepared in an inert atmosphere, while the second synthesis was conducted in air.…”