Synthesis of LiGaO2 nanocrystals and their application toward bright UV emission from ZnO quantum dots

Inorganic capping material for ZnO quantum dots (QDs) was designed on the basis of the crystal and electronic structures, and a ternary β-LiGaO2 was proposed as a candidate. Two reaction routes to the β-LiGaO2 nanocrystals (NCs), the alkylhalide elimination reaction between gallium iso-propoxide and lithium bromide and the thermolysis of gallium and lithium acetylacetonates, were investigated. The alkylhalide elimination reaction resulted in near-stoichiometric β-LiGaO2 NCs; however, it was not applicable to fabricate composite NCs with ZnO, because ZnO dissolved in the β-LiGaO2 reaction solution upon heating. Based on the thermolysis formation of β-LiGaO2, composite NCs of ZnO with β-LiGaO2 were successfully obtained. The high resolution transmission electron microscopy and X-ray photoelectron spectroscopy results indicated that the composite was a ZnO/LiGaO2 core/shell nanostructure consisting of ∼3.5 nm diameter core ZnO and ∼0.5 nm thick β-LiGaO2 shell layers. Because the photoluminescence of the core/shell QDs was dominated by the core ZnO, the type-I quantum well structure of the core/shell QDs, in which the core ZnO part forms the potential well, was strongly suggested.

► We have proposed β-LiGaO2 as a shell material for the ZnO quantum dots (QDs). ► Fabrication of the ZnO/LiGaO2 core/shell QDs was demonstrated. ► Results indicated that ZnO was capped with ∼0.5 nm thick β-LiGaO2 layer. ► Optical spectra suggested a type-I quantum well structure of the core/shell QDs.