Colloidal ZnSe quantum dots were successfully synthesized from ZnO in a lauric acid/hexadecylamine mixture. X-ray diffraction patterns indicated that the ZnSe quantum dots possess a wurtzite structure. Transmission electron microscope images of the quantum dots showed that the average diameter are in the range of 25∼60 Å. The size-dependent photoluminescence was controlled from 400 to 440 nm with the quantum yields of 6∼10% at room temperature. After passivation with 1.8 monolayer of ZnS overcoat by a traditional two-step method, the quantum yields of ZnSe/ZnS QDs are increased ∼4.5-fold (quantum yield ∼32%). An in-situ method of overcoating was done by directly injecting TOPS into the flask containing ZnSe, ZnO/lauric acid/ hexadecylamine, and TOPSe. The photoluminescence quantum yields were improved ∼3.8-fold after introduction of 1.6 monolayer ZnSeS overcoat to the ZnSe QDs.

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Luminescence D 6540 Colloidal ZnSe, ZnSe/ZnS, and ZnSe/ZnSeS Quantum Dots Synthesized from ZnO. -Colloidal ZnSe quantum dots are synthesized from ZnO powder in a lauric acid/hexadecylamine mixture. The quantum dots show controlled photoluminescence emission from 400 to 440 nm with quantum yields from 6 to 10% at room temperature. By coating ZnSe with ZnS the photoluminescence quantum yield of ZnSe/ZnS quantum dots increases ca. 4.5-fold, whereas ZnSeS coated ZnSe/ZnSeS quantum dots exhibit ca. 3.8-fold increased photoluminescence quantum yields. The results show a potential for the preparation of colloidal ZnSe, ZnSe/ZnS, and ZnSe/ZnSeS quantum dots from cheap and nontoxic ZnO. -(CHEN*, H.-S.; LO, B.; HWANG, J.-Y.; CHANG, G.-Y.; CHEN, C.-M.; TASI, S.-J.; WANG, S.-J.