Zinc–Phosphorus Clusters for Solution Synthesis of Zinc Phosphide Nanoparticles
Abstract
Synthesis of zinc phosphide (Zn3P2) nanoparticles is an emerging topic of investigation as Zn3P2 is a candidate material for the next generation solar cells. Despite the early discovery of its favorable electronic properties that are well-suited for photovoltaic applications, a major focus of synthetic strategy was with vapor/chemical deposition methods. Solution methods with greater control over size, crystal structure and composition at a lower production cost, has been underdeveloped in comparison. In this context, this thesis describes the synthesis, characterization and reactivity of zinc phosphido clusters: [Zn2(μ-PPh2)2(PPh2)2(NC5H5)2], [Zn4(μ-PPh2)4(OAc)4(NC5H5)2] and a phosphinidene cluster: [Zn6(μ3-PSiMe3)4(OAc)4(NC5H5)5] as potential single source precursors for solution synthesis of Zn3P2 nanoparticles. The clusters were prepared by reacting zinc acetate with silylphosphines and fully characterized via multinuclear NMR spectroscopy, single crystal XRD, melting point and combustion analysis. Use of the pyridine solvent was critical as pyridine ligands provided the necessary ligand stabilization for the isolation and crystallization of the clusters. When the zinc phosphido clusters were thermolyzed in pyridine, they yielded metallic zinc nanocrystals via a redox process. When the thermolysis was carried out with white phosphorus as an additive, soluble, zinc rich aggregates of zinc phosphides were produced. [Zn4(μ-PPh2)4(OAc)4(NC5H5)2] showed reactivity with P(SiMe3)3, but a larger cluster framework could not be isolated. When thermolyzed in oleylamine, [Zn6(μ3-PSiMe3)4(OAc)4(NC5H5)5] produced highly crystalline, non-luminescent and soluble zinc phosphide nanoparticles, a first example of a direct cluster to nanoparticle conversion for Zn3P2.