UNCOVERING STRUCTURE-PROPERTY RELATIONSHIPS OF INORGANIC NANOMATERIALS VIA TRANSMISSION ELECTRON MICROSCOPY

The rapid increase of research in nanoscale devices and nanotechnology in the past few decades has revealed that nanomaterials may possess exceptional properties that are significantly different from the bulk counterpart, due to local rearrangements of the atoms at surfaces and defects. Transmission electron microscopy (TEM) is an indispensable tool when it comes to the characterization of nanomaterials, primarily due to its ability to resolve the local-structure of materials at the atomic-scale. To study dynamic processes, however, regular TEM experiments are inadequate, as they provide only before and after information rather than the real-time data essential to understanding a reaction or phase-transformation mechanism. This dissertation describes developments and applications of high- resolution and in situ TEM techniques to track the atomic rearrangements of nanomaterials in real-time, to determine the structure-property relationships of nanomaterials as they change during structural-transformations such as chemical reactions. The four chapters in this dissertation will focus on the synthesis and characterization of nanomaterials with unique properties. The first project concentrates on designing a novel synthesis method to control the morphology of iron(II) sulfide (FeS) nanoplatelets by varying the starting material (Fe source) or the surfactant employed in the hydrothermal synthesis. The following three chapters cover detailed TEM analyses of three distinctive nanomaterials: catalytic hetero-atom doped carbon nano-onions, thermoelectric La3-xTe4 with Ni nanoparticle inclusions, and dielectric cubic HfO2. The work presented here gives insights on a novel morphology-controlled hydrothermal synthesis of FeS nanoplatelets and demonstrates the utilization of advanced electron microscopic techniques such as aberration-corrected TEM/Scanning TEM (STEM) and in situ TEM, to elucidate structure-property relationships of nanomaterials in atomic-resolution and in real-time