Synthesizing CdTe Magic-Sized Clusters with a Secondary Phosphine

Saryvoudh A. Mech

University of Florida

CdTe magic-sized clusters (MSCs) are II-VI semiconductor nanocrystals below 3 nm in size that are differentiated from standard larger quantum dots (QDs) via their quantized growth and sharp absorbance peaks. Because of their highly reproducible syntheses and sizes, they offer more consistent optoelectronic properties for devices than their larger QD contemporaries. CdTe has seen less attention compared to its fellow cadmium chalcogenides (CdE, E = S, Se, Te) due to the difficulty of Te conversion chemistry. Understanding the role of the chemicals used in synthesis will allow for more control over the final product. Diphenylphosphine (DPP), a secondary phosphine, is a suitable replacement for trioctylphosphine (TOP) due to its high reactivity – microliters of DPP can be used instead of milliliters of TOP while also increasing the yield of  a dot shaped MSC species with a first excitonic absorbance at 449 nm (E₁). The high reactivity of DPP enables the synthesis to be performed at a lower temperature, which also leads to the smaller dot shaped MSC species with E₁ peaks at 373 nm and 420 nm by tuning the temperature and oleylamine used in the reaction. This information furthers the understanding of these systems, allowing for enhanced control on the synthesis of this promising class of nanocrystal.