Gradated alloyed CdZnSe nanocrystals with high luminescence quantum yields and stability for optoelectronic and biological applications

Graded, high-quality ternary CdZnSe quantum dots (QDs) have been successfully prepared by the alloying of CdSe/ZnSe core/shell QDs at high temperatures. By increasing the alloying time, a gradient distribution of components was obtained, which leads to tunable emission across most of the visible spectrum through a systematic blue-shift in emission wavelength. The resultant alloyed QDs show a gradated quasi core/shell structure in which the core is CdSe rich and the shell is rich in ZnSe. This distinctive structure results in a photoluminescence (PL) quantum yield (QY) up to 55% and moreover, the alloyed nanocrystals can retain their high luminescence when dispersed in aqueous solutions. They also demonstrate high photo and thermal stability. The peak shape and spectral position remains unchanged under all experimental conditions undertaken in this study.