Insights into the Synthetic Mechanisms behind Ligand-free Metal Nanoparticle Formation
Open Access
- Author:
- Veghte, Rosemary Marie
- Graduate Program:
- Chemistry
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- January 26, 2016
- Committee Members:
- Thomas E Mallouk, Thesis Advisor/Co-Advisor
- Keywords:
- nanoparticle
sintering
transmission electron microscopy
x-ray diffraction
solid state - Abstract:
- The reactions catalyzed by metal nanoparticles are of great importance in a number of industries that range from synthesizing methanol to designing more efficient catalytic converters. An issue facing many of these processes comes in the form of nanoparticle sintering: coarsening and growth of metal nanoparticles caused by their need to lessen overall surface energy. The resulting nanoparticle growth that arises from this energetic need dramatically diminishes their catalytic activity. This, in turn, costs major industries time and money as they work to replenish the catalyst. Past work has been done to more fully understand catalytic systems involving metal oxide/hydroxide nanoparticles deposited on a variety of early transition metal oxide supports. Through this work, it was found that an anomalous stabilization of the metal nanoparticles was possible when they were deposited on certain types of metal oxide supports. These studies were then expanded to include preliminary periodic trends that have been garnered from work done by high resolution transmission electron microscopy (TEM), isothermal titration calorimetry (ITC), and X-Ray diffraction (XRD). More recently, ligand-free, OH- - stabilized Pt and Pd nanoparticles have been synthesized and characterized via the methods listed above. These ligand-free nanoparticles hold greater catalytic relevance because of their lack of bulky surface ligands, granting them with a higher available surface area for large-scale industrial reactions. While the synthesis of these OH- - stabilized ligand-free metal nanoparticles is of great importance, it is also necessary to understand their behavior in solution – how they form, how they remain dispersed, and so on – in order to formulate conditions that will preserve their stability. Presented here is work done to synthesize and characterize ligand-free Pt and Pd metal nanoparticles. Their reaction progress was monitored by UV-Visible spectroscopy, and intermediate reaction species will soon be determined by 195Pt NMR. The final product was confirmed via TEM and XRD. The metal nanoparticles were then deposited onto sheets of calcium niobate (KCa2Nb3O10), and the resulting reaction setup was exposed to temperatures up to 900°C to monitor their sintering under harsh conditions, with the overarching goal of understanding how metal nanoparticles interact with their support systems.