Water-soluble, high-quality ZnSe@ZnS core/shell structure nanocrystals

Water-soluble and high photoluminescence (PL) efficiency ZnSe@ZnS core/shell quantum dots were synthesized by a facile aqueous phase route in the presence of additional glutathione ligand as a stabilizer and thiourea as a sulfur source. The structure and optical properties of the obtained ZnSe@ZnS nanocrystals were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, PL spectroscopy, and Fourier transform infrared spectrometer. The ZnSe@ZnS shows a cubic zinc-blende crystal phase and has a narrow size distribution. Experimental results indicate that the ZnS shell plays a pivotal role in determining optical features. With the reaction time from 0 to 3 h, the fluorescence emissions of ZnSe@ZnS nanocrystals are tunable between 372 and 380 nm. The high quantum yields are calculated to be in the range of 23%–62.8%. The mechanism for the resulting high-quality optical properties is also elucidated.