| Abstract | Zinc phosphide may have potential for photovoltaic applications due to its high absorptivity of visible light and the earth abundance of its constituent elements. Two different solution-phase synthetic strategies for phase-pure and crystalline Zn3P2 nanoparticles (∼3-15 nm) are described here using dimethylzinc and vary with phosphorus source. Use of tri-n-octylphosphine (TOP) with ZnMe2 takes place at high temperatures (∼350 C) and appears to proceed via rapid in situ reduction to Zn(0), followed by subsequent reaction with TOP over a period of several hours to produce Zn3P2 nanoparticles. Some degree of control over size was obtained through variance of the TOP concentration in solution; the average size of the particles decreases with increasing TOP concentration. With the more reactive phosphine, P(SiMe3)3, lower temperatures, ∼150 C, and shorter reaction times (1 h) are required. When P(SiMe3)3 is used, the reaction mechanism most likely proceeds via phosphido-bridged dimeric Zn(II) intermediates, and not metallic zinc species, as is the case with TOP. In all cases, the nanoparticles were characterized by a combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and solution and solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) analyses. Surface investigation through a combination of MAS 31P NMR and XPS analyses suggests that the particles synthesized with TOP at 350 C possess a core-shell structure consisting of a crystalline Zn3P 2 core and an amorphous P(0)-rich shell. Conversely, the ligand and phosphorus sources are decoupled in the P(SiMe3)3 synthesis, resulting in significantly reduced P(0) formation. © 2014 American Chemical Society. |
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