Preparation of Highly Luminescent CdTe/CdS Core/Shell Quantum Dots

Abstract

An effective shell-coating route is developed for covering oil-soluble CdTe quantum dots (QDs), which usually tend to aggregate during the heating-up process involved in shell formation. The new route is based on balancing the coordinating capacity and the activation effect of selected surfactants. The thus obtained highly luminescent CdTe/CdS core/shell QDs exhibit photoluminescence quantum yields as high as 92%--among the best results obtained so far for luminescent semiconductor nanocrystals. By changing the size of the CdTe core, or the thickness of the CdS shell, the emission colors of the obtained core/shell nanocrystals can be tuned between the visible and near-infrared regions of the spectrum following an identical procedure.

High-efficiency CdTe/CdS core/shell nanocrystals in water enabled by photo-induced colloidal hetero-epitaxy of CdS shelling at room temperature

“…A general trend is the red shift of the PL for CdTe/CdS QDs and blue shift of PL for the reference CdTe QDs. A red shift for the core/shell CdTe/CdS QDs has been frequently reported, as a supporting evidence of the shell formation [16,44,45]. The reason is the type II band alignment of the CdTe/CdS core/shell, which results in partial leakage of exciton to the CdS shell [26,43,46].…”

“…Nano Res. The growth of an inorganic shell on QDs is known to improve the stability of QDs [26,44,46,49]. Here the effect of CdS shell on the thermal stability of QDs was further evaluated by depositing QDs on a glass substrate (The purification of CdTe/CdS QDs is not possible by acetone, therefore they were transferred to chloroform solvent by cetyltrimethylammonium bromide (CTAB) and then were spin coated on a glass) and measurement of PL QY for the solid film samples after 20 min at different temperatures (in oven).…”

Effect Of Cross Linking On the Toxicity of CDTE QDS in Solid/ Liquid Medium

“…2(b)). This can be attributed to the presence of sulfur obtained from dissolution of GSH forming CdS layer over the CdTe QDs having a prevalent hexagonal structure [9,10] …”

Photoluminescence quenching of CdTe/CdS core-shell quantum dots in aqueous solution by ZnO nanocrystals

“…The PL QY and photostability of CdTe QDs as an important type of nanomaterials were improved dramatically by growing a CdS shell on the CdTe core [11][12][13][14][15][16][17][18][19][20]. CdTe/CdS core-shell QDs with a core of smaller than 1.5 nm in diameter were considered to be type II nanocrystals [19], in which the hole is mostly confined to the CdTe core, while the electron is mostly confined to the CdS shell due to their band offsets [17][18][19][20].…”