Cottrell Scholar Awards - 2015
Using Metal-Ligand Chemistry to Understand, Form, and Tailor Nanoscale Alloys
Matter behaves differently at the nanoscale – a realm smaller than bacteria but larger than atoms. At this level, matter, freed from the crowd as it were, behaves in ways not seen in “bulk” materials, that is, in bigger lumps of stuff.
Jill Millstone, assistant professor of chemistry, University of Pittsburgh, has received a Cottrell Scholar funding to study metal alloys – mixtures of different metals -- at the nanoscale.
“Throughout history,” Millstone said, “from bronze to steel, alloys have defined the technological capabilities of their times. They have been some of the most transformative and most thoroughly studied materials, and scientific descriptions of bulk alloy formation are now well-established.”
But, she added, these descriptions break down when the dimensions of the material are reduced to the nanoscale. Millstone theorizes this disconnect may be attributed to the large surface-to-volume atom ratios at the nanoscale. And her research is focused on two primary factors that result from these differences in atom populations: surface energy and solid state atom diffusion.
Atoms at a surface, be it a block of wood or a bronze ingot, are less stable than the atoms within the material; and this is why droplets tend to collect into one big drop or why oil and vinegar always go back to two separate phases. “Solid state atom diffusion” refers to the tendency of atoms to move within the uniformly ordered crystalline lattice of atoms that compose metals and metal alloys, a process that is accelerated by heat.
Specifically, Millstone’s work involves attempting to create alloys not by the heat of the forge traditionally used for making bulk metals, but by using “ligand chemistry” at the nanoscale. A “ligand,” is a chemistry term for any molecule or ion that binds to a central metal atom. In some cases, she predicts, the chemical method of making alloys at the nanoscale will overcome difficulties encountered through the traditional method of combining molten metals, thus producing innovative new alloys.
“Nanoparticle alloys promise to provide improved catalysts for efficient use of chemical feedstocks, as well as new tools for biomedical applications,” Millstone said.
Millstone said she will also use some of her Cottrell Scholar funding to develop independent curriculum modules in materials chemistry that can be easily integrated into a variety of existing courses at many levels.
“Materials chemistry is a crucial tool in solving global technology challenges in energy, water and food supplies,” she said. “Although it is now becoming a core discipline in chemistry departments across the nation, it still comprises a small percentage of core course work in undergraduate chemistry degrees.”