Session: Chemistry of Materials:

We report aminophosphines derived from N,N’-disubstitutedethylenediamines (R–N(H)CH₂CH₂N(H)–R; R = ortho-tolyl, phenyl, benzyl, iso-propyl, n-octyl) that adjust the kinetics of InP nanocrystal formation by more than an order of magnitude. UV-Visible absorption and ³¹P nuclear magnetic resonance measurements demonstrate that the rate of nanocrystal formation is limited by the precursor reactivity. At low temperature (180 °C) crystal nucleation is concurrent with growth throughout the reaction, rather than occurring in a burst at early times. Higher temperatures (up to 270 °C) promote growth to larger sizes and shorten the nucleation period, creating conditions where the final size is controlled by the precursor conversion reactivity. The narrow size distributions obtained from reactions without separation of nucleation and growth and the influence of temperature on the final size can be explained by monomer attachment kinetics that are more rapid at small crystal sizes.

Jonathan Owen

Columbia University

Appearances