Investigation of Indium Phosphide Quantum Dot Nucleation and Growth Utilizing Triarylsilylphosphine Precursors

Abstract

We have developed a two-phosphine strategy to independently tune nucleation and growth kinetics based on the relative reactivity of each precursor in the synthesis of indium phosphide (InP) quantum dots (QDs). This approach was allowed by the exploration of the synthesis and reactivity of a series of sterically encumbered triarylsilylphosphines substituted at the para position of the aryl group, P(Si(C 6 H 4 -X) 3 ) 3 (X = H, Me, CF 3, or Cl), as a contrast to P(SiMe 3 ) 3, the P 3– source commonly employed in such syntheses. UV–vis absorption spectroscopy of aliquots taken during InP QD growth revealed a stark contrast between triarylsilylphosphines with electron-donating and electron-withdrawing groups in both the rate of InP formation and the final particle size. 31 P{ 1 H} nuclear magnetic resonance spectroscopy confirmed that precursor conversion remains rate-limiting throughout the nanocrystal synthesis when P(SiPh 3 ) 3 is incorporated as the sole phosphorus precursor; however, this is insufficient for effective separation of nucleation and growth in this system because of the slow nucleation rates that result. In all cases, syntheses that employ a single chemical species as the P 3– source were found to suffer from a poor match in reactivity with In(O 2 C(CH 2 ) 12 CH 3 ) 3 as they either fail to separate nucleation from growth because of slow precursor conversion rates [P(SiPh 3 ) 3 and P(Si(C 6 H 4 -Me) 3 ) 3 ] or preclude size selective growth from rapid precursor conversion [P(SiMe 3 ) 3, P(Si(C 6 H 4 -Cl) 3 ) 3, and P(Si(C 6 H 4 -CF 3 ) 3 ) 3 ]. To balance these two extreme cases, we developed a novel approach in which two different P 3– sources were introduced to segregate nucleation and growth based on the relative reactivity of each precursor.