Transient Physicochemical Properties of Nanomaterials

Northwestern University, Evanston IL

Investigators

Abstract

With support from the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Richard Schaller from Northwestern University will investigate crystal lattices, surfaces, and surface ligand behavior of semiconductor and metal nanoparticles to advance understanding of their physicochemical properties. Semiconductor and metal particles with nanometer-scale features offer beneficial attributes that can be exploited for solid-state lighting, displays and photovoltaics to bio/chem sensors. The studies of this research project will experimentally elucidate equilibrium- and time-evolution of key properties under conditions that either push nanomaterials to performance limits or expressly target particle fusion. This project will support training for future researchers in areas of advanced experimental methods and data analysis and offers advances in communal knowledge regarding promising materials systems. Research methods and findings from the lab will be incorporated into the classroom and presented in public venues. Member of the Schiller group will engage in outreach to community colleges and public schools. The response of nanoparticles and surface ligands to intense excitation and elevated temperature, whether pulsed or sustained, impacts optoelectronic characteristics as well as influences the solid produced during additive manufacturing. Planned studies aim to both evaluate this impact but more importantly offer insights as to evolution of such systems using approaches spanning transient x-ray diffraction and stimulated Raman to selected area electron diffraction and nuclear magnetic resonance for a range of excitation conditions. The proposed effort seeks to evaluate processes and relevance of ligand re-partitioning, surface activity, lattice disordering, de-mixing of particular compositions, and evolution of phonon distributions. Insights can offer means to increase stability of as-designed nanoparticles to extreme conditions or conversely facilitate incorporation into a sintering ensemble of particles. Several earth abundant and low toxicity compositions will be investigated. The overall objective is to discern and learn to predict how nanoparticle structure and chemical ligand motif impact static and dynamic physicochemical properties under technologically relevant conditions. 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.