Mechanistic Insights into Size-Focused Growth of Indium Phosphide Nanocrystals in the Presence of Trace Water

Abstract

Indium phosphide (InP) nanocrystals have emerged as a viable alternative to heavy metal-based colloidal quantum dots for optoelectronic applications. Traditionally, the presence of trace amounts of water during the synthesis of colloidal quantum dots is considered an undesired impurity because it prevents or slows down colloidal growth and alters the surface properties. Here, we report that fine-tuning the amount of trace water is the key for achieving sizefocused growth of monodisperse InP nanocrystals synthesized using aminophosphine precursors. Using solid-state and solution nuclear magnetic resonance, we investigated the role of trace amounts of water in surface oxidation and precursor conversion reactions. Molecular insights from UV−vis spectroscopy and NMR revealed a profound contrast between the growth rates of the nanocrystals upon the addition of water to the reaction system. We demonstrate that by addition of a specific amount of water, the reactivity of the phosphorous precursor can be tuned to enable a constant supply of monomer throughout the reaction. Under an optimal precursor conversion rate, a size-focused growth behavior that is rare for InP nanocrystals is observed, suggesting the presence of an artificial LaMer-like growth regime.

Continuous Nucleation and Size Dependent Growth Kinetics of Indium Phosphide Nanocrystals

“…38,39 Finally, a recent study has shown that trace water improves the size distribution obtained from InX 3 /P(NR 2 ) 3 , a variable not explored in our work. 40 The kinetics of InP formation is monitored by measuring the optical absorption (λ = 413 nm) of timed aliquots. 27 Although large cluster intermediates (>[InP] 20 ) could, in principle, contribute to the absorption at this wavelength, no spectroscopic signatures of clusters were observed herein nor has any evidence for InP clusters been reported for syntheses conducted with InX 3 /P(NR 2 ) 3 .…”

Tailored growth of single-crystalline InP tetrapods

“…On the other hand, colloidal semiconductor nanocrystals (NCs) have been exploited in academic and industrial sectors for more than 30 years, mainly via trial-and-error basis synthetic development owing to their unresolved reaction kinetics and thermodynamics 3 – 11 . Due to the co-existence of metastable states with similar energy, unraveling the reaction pathways in full detail has been difficult 12 – 16 .…”

Synergistic Effect of Halogen Ions and Shelling Temperature on Anion Exchange Induced Interfacial Restructuring for Highly Efficient Blue Emissive InP/ZnS Quantum Dots

“…[15][16][17][18] To date, considerable research has focused on growth kinetics and synthetic strategies of InP QDs. [19][20][21][22][23][24][25] Apart from the common method where indium acetate and tris(trimethylsilyl)phosphine ((TMS) 3 P) are utilized, indium halide is widely employed in the preparation of InP/ ZnS QDs combining with zinc halide and amino phosphine recently owing to its low cost and safety. As has been reported, halide plays a critical role in its nucleation and surface chemistry.…”