Resolving the Chemistry of Zn₃P₂ Nanocrystal Growth

[EtZnP­(SiMe₃)₂]₃ has been identified as a competent intermediate for the growth of stoichiometric α-Zn₃P₂ nanocrystals from Zn-rich zinc phosphide seeds as determined by powder X-ray diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy, and transmission electron microscopy analysis. Solution-phase NMR data show that this trimer forms <i>in situ</i> upon reaction of P­(SiMe₃)₃ and ZnEt₂ in the presence of Zn­(O₂CR)₂ under zinc carboxylate-limited conditions. [EtZnP­(SiMe₃)₂]₃ can also be used to nucleate zinc phosphide; however, in comparison to a previously examined nucleation pathway involving (Et₂Zn)­P­(ZnO₂CR)₂(SiMe₃), a decrease in relative reactivity leads to fewer nuclei and larger, more crystalline particles. These data, in combination with previous literature on the synthesis of zinc phosphide nanocrystals, were then aggregated to propose a set of design principles for the synthesis of zinc phosphide nanocrystals using P­(SiMe₃)₃ as the phosphorus precursor

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

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 <i>para</i> position of the aryl group, P­(Si­(C₆H₄-X)₃)₃ (X = H, Me, CF₃, or Cl), as a contrast to P­(SiMe₃)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. ³¹P­{¹H} nuclear magnetic resonance spectroscopy confirmed that precursor conversion remains rate-limiting throughout the nanocrystal synthesis when P­(SiPh₃)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(O₂C­(CH₂)₁₂CH₃)₃ as they either fail to separate nucleation from growth because of slow precursor conversion rates [P­(SiPh₃)₃ and P­(Si­(C₆H₄-Me)₃)₃] or preclude size selective growth from rapid precursor conversion [P­(SiMe₃)₃, P­(Si­(C₆H₄-Cl)₃)₃, and P­(Si­(C₆H₄-CF₃)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

Synthesis of Zn₃As₂ and (Cd_<i>y</i>Zn_1–<i>y</i>)₃As₂ Colloidal Quantum Dots

Synthesis of Zn₃As₂ and (Cd_<i>y</i>Zn_1–<i>y</i>)₃As₂ Colloidal Quantum Dot