The Determinants of Crystalline Phase in Bottom-Up Nanocrystal Synthesis

Vanderbilt University, Nashville TN

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Janet Macdonald, from Vanderbilt University aims to help elucidate how nanocrystals form, as well as provide insight into their structure and hidden properties. The properties of all solids are determined by the elements that comprise them and their arrangement. Even a simple combination of two elements, like iron sulfide, can produce as many as nine different crystal formations with vastly different chemical and magnetic behavior, conductivity, color, other properties, and potential uses. This complexity makes crystalline science incredibly intriguing. The knowledge to be gained from this research project is expected to help in the discovery of conditions to produce individual nanocrystal types in pure form. Focusing research on nanocrystalline inorganic materials could ultimately unleash potentially disruptive technologies as this size of crystal generally has a great potential for applications in solar cells, batteries, medical magnetic imaging, semiconductors, and novel catalysts. One outreach activity of the project, involves using the knowledge gained on iron chemistry to rediscover long-lost methods for preparing ancient rock art of the Anishinaabe. In addition, this project will provide a rigorous research training for graduate and undergraduate students to help build the future workforce in science. Under this award, Professor Macdonald and her team will perform a wide, sweeping, and systematic study of the phase-controlled synthesis. Manganese, iron, cobalt, nickel, and copper chalcogenides (sulfides, selenides and tellurides) be examined in particular because they have particularly complex phase diagrams. Libraries of organochalcogenides will be employed to separate the role of the kinetic rate from the decomposition mechanism of the precursors in phase determination. Maps will be drawn of the phase landscape that will provide guidance for targeted synthetic changes to achieve one phase over another. The second aim strives to resolve a long-standing debate about how polytypes are controlled in nanocrystal synthesis. Tools gleaned from molecular coordination chemistry will be employed with the goal of achieving polymorphic phase control more broadly across the periodic table to target "ghost phases" that have been predicted but never seen. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.