Anton Kovyakh

A thesis for the degree of Doctor of Philosophy defended in August 2018.

The PhD School of Science, Faculty of Science, X-ray and Neutron Science, Niels Bohr Institute, University of Copenhagen

Academic advisor:
Robert Feidenhans'l
Kell Mortensen

X-ray Pair Distribution Function Analysis of Transition and Noble Metals for Industrial Applications in Sensing and Catalysis

Understanding structures and properties of nanoscale materials is increasingly important in contemporary technological development. The presented work investigates the applications of x-ray pair distribution function (PDF) analysis in a number of industrial research projects. The viability of the method is explored in the areas of instrumentation, catalysis, time-resolved measurements and novel data reduction protocols.

Obtaining quantitative structural information efficiently is essential for studying materials synthesized using combinatorial methods. To address this we propose a protocol for measuring and analyzing data from such high-throughput experiments. For this study, a combinatorial array containing catalytic nanoparticles was prepared from liquid precursors, directly on-chip, using an ink-jet liquid handling system. The array was then measured at the x-ray powder diffraction beamline (NSLS-II) and analyzed by the PDF technique using a software implementation of the proposed protocol. The developed protocol software can handle semi-automated data reduction, normalization and modeling. A comprehensive collection of metadata and analysis results is generated from user-defined recipes. By slicing this collection using the included functions it is possible to determine the distribution of material on the array, highlight regions with heterogeneity, and visualize spatially varying structural parameters. The modular design of the software is intended to be transparent and extensible, with potential applications to other experimental techniques.

Copper nanoparticles have the potential to completely replace silver in applications of printed electronics. A cost effective and environmentally-safe method of manufacturing nanoparticles using glucose reduction of copper in an aqueous media is studied in detail using synchrotron x-ray PDF. Nanoparticle growth is observed in-situ, utilizing a new setup for continuous flow characterization. The limiting factor for the reactions is found in the chemical kinetics. Meanwhile, the reducing agent is found to be an effective capping agent. The methodology is successfully tested together with novel data reduction and
analysis methods.