Mark Hendricks (Owen Group)
2:00pm - 3:00pm
Colloidal semiconducting nanocrystals, or quantum dots, are beginning to find applications in biological imaging, solar cells, and as down-converters for LED-driven light bulbs and displays. This talk will discuss various experimental endeavors that explore the role of the precursors used to make these nanocrystals, with a special interest in the kinetics of their reactivity.
I will briefly describe the synthesis of cadmium bis(diphenyldithiophosphinate) (Cd(S2PPh2)2) from secondary phosphine sulfides and its conversion to cadmium sulfide nanocrystals. Interestingly, the final diameter of nanocrystals produced from this reaction is insensitive to the reaction conditions, including the total concentration of precursors, which we attribute to the rate of precursor conversion. The CdS nanocrystals are also used as a model system to discuss the surface chemistry of metal chalcogenides nanocrystals.
Next, I will introduce a novel method of controlling the number and size of nanocrystals through the use of a precursor library. Specifically, the substitution pattern of thioureas can be used to control their conversion reactivity over more than five orders of magnitude. Tunable kinetics allows the nanocrystal concentration to be adjusted and a desired crystal size to be prepared at full conversion. Controlled precursor reactivity and quantitative conversion improve the batch-to-batch consistency of the final nanocrystal size at industrially relevant reaction scales. It also opens up new synthetic routes towards commercially-relevant core/shell heterostuctures and new methods of studying nanocrystal reactions.