Due to the presence of accessible d-electrons, the phase diagram of transition-metal pnictides is rich with structures and stoichiometries. These phases exhibit a wide range of magnetic and electronic properties of fundamental and practical interest including superconductivity, ferromagnetism, magneto-striction, magneto-optics, and semiconductivity, and are also of interest as hydrodesulfurization (HDS) or hydrodenitration catalysts for petroleum processing. However, despite overwhelming interest in their main group analogs (e.g. GaAs, InP), transition metal pnictide nanoparticles remain essentially unexplored until recently (Senevirathne et. al. J. Solid State Chem. 2008, 181, 1552-1559, doi:10.1016/j.jssc.2008.03.012). The introduction of size control as a synthetic variable is expected to produce a unique class of materials with properties that are tunable with size. We have developed arrested precipitation methods that enable us to form narrow polydispersity nanoparticle samples of phases including FeP, Fe2P, MnP, MnAs and Ni2P. In addition to developing new synthesis methods, we have also been extensively exploring how size limitation impacts magnetic exchange (in collaboration with Gavin Lawes, Physics, WSU) and HDS catalytic activity (in collaboration with Mark Bussell, Western Washington University). These studies have implications for the development of magnetic hard drives and next generation catalysts.
1) Isovalent Doping Strategy for Manganese Introduction into III-V Diluted Magnetic Semiconductor Nanoparticles – InP:Mn (Somaskandan et. al. Chem. Mater. 2005, 17, 1190) 10.1021/cm048796e
2) Controlled Synthesis of MnP Nanorods: The Effect of Shape Anisotropy on Magnetization (Gregg et. al. Chem. Mater. 2006, 18, 879) 10.1021/cm052080h
3) Synthesis and Characterization of Discrete Nickel Phosphide Nanoparticles: Effect of Surface Ligation Chemistry on Catalytic Hydrodesulfurization of Thiophene. (Senevirathne et. al. Advanced Functional Materials, 2007, 17, 3933-3939) DOI: http://dx.doi.org/10.1002/adfm.200700758
4) Discrete, Dispersible MnAs Nanocrystals from Solution Methods: Phase Control on the Nanoscale and Magnetic Consequences. (Senevirathne et.al. ACS Nano, 2009, 3, 1129-1138) http://pubs.acs.org/doi/pdf/10.1021/nn900194f
5) Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe2P and FeP. (Muthuswamy et. al. ACS Nano, published on the web on 4th AUG 2009) http://pubs.acs.org/doi/full/10.1021/nn900574r