Incorporation of Metal Phosphide Domains into Colloidal Hybrid Nanoparticles

Colloidal hybrid nanoparticles have generated considerable attention in the inorganic nanomaterials community. The combination of different materials within a single nanoparticle can lead to synergistic properties that can enable new properties, new applications, and the discovery of new phenomena. As such, methodologies for the synthesis of hybrid nanoparticles that integrate metal-metal, metal chalcogenide, metal oxide, and oxide-chalcogenide domains have been extensively reported in the literature. However, colloidal hybrid nanoparticles containing metal phosphide domains are rare, despite being attractive systems for their potentially unique catalytic, photocatalytic, and optoelectronic properties. In this Forum Article, we report a study of the synthesis of colloidal hybrid nanoparticles that couple the metal phosphides Ni₂P and CoP with Au, Ag, PbS, and CdS using heterogeneous seeded-growth reactions. We also investigate the transformation of Au-Ni heterodimers to Au-Ni₂P, where phosphidation of preformed metal-metal hybrid nanoparticles offers an alternative route to metal phosphide systems. We also study sequential cation-exchange reactions to target specific metal phosphide hybrids, i.e., the transformation of Ni₂P-PbS into Ni₂P-Ag₂S and then Ni₂P-CdS. Throughout all of these pathways, the accompanying discussion emphasizes the synthetic rationale, as well as the challenges in synthesis and characterization that are unique to these systems. In particular, the observation of oxide shells that surround the phosphide domains has implications for the potential photocatalytic applications of these hybrid nanoparticles.