Form and Function: X-Ray Scattering and Spectroscopy of Transition Metal-Based Nanoparticles

In recent decades, nanoparticles have been found to possess unique, tunable properties with an enormous variety of applications. The atomic and nanoscale structures govern these functional properties, and structural deviations from the bulk, in part, are responsible for the vast technological uses of nanoparticles. This dissertation tackles the understanding of structure in a number of metal, metal phosphide, and metal oxide nanoparticle systems. Additionally, the syntheses of monodispersed nanoparticle systems allow for correlating their structure with functional properties. Real space analysis using pair distribution functions of monometallic (Ni, Pd) nanoparticles of less than 5 nm in diameter revealed a deviation from the bulk face-centered cubic structure. Their local atomic packing disorder and lack of long-range order resemble that of bulk metallic glasses, which often consist of complex mixtures of a multitude of elements. Bulk metallic glasses have high mechanical strength and can sustain elastic deformations. The significant connection between these two seemingly disparate systems lie in the short-range ordering of their atomic packing motifs, which consist of icosahedral symmetry as seen in their pair distribution functions. Cobalt phosphide (Co2P) nanorods are promising as inexpensive, earth abundant catalysts for the oxygen reduction reaction in fuel cells. Additionally, their 1-D structures demonstrated greater stability as compared to conventional Pt catalysts. Their structure was investigated using high-resolution electron microscopy and a suite of X-ray scattering and absorption techniques. The dynamic structural nature of the solid-solid phase transition in vanadium dioxide (VO2) thin films was investigated using X-ray absorption fine structure spectroscopy. Substitution of transition metal dopants into lattice sites revealed the structurally-driven depression of the metal-to-insulator transition temperature. Bridging form and function, this dissertation reports the colloidal synthesis of monodispersed nanoparticles alongside structural investigations and functional testing