Cation Exchange Pathways for Constructing Metal Chalcogenide Nanoparticle Libraries

Non-Technical SummaryNew materials drive innovation in science and technology. Scientists are becoming better and better at predicting new materials, but it can often be challenging to make them. In this project, which is funded by the Solid State and Materials Chemistry program in the Division of Materials Research, Professor Ray Schaak and his group at Penn State University use simple chemical reactions to replace certain elements in a nanoparticle material with other elements. These reactions transform simple nanoparticles into nanoparticles that are much more complex. The researchers are studying how these reactions occur and how they can be used to make new types of nanoparticles that could help to advance applications in clean energy. This project is establishing new rules for how to control the arrangements of atoms and materials within a nanoparticle that contains various metals along with sulfur, selenium, tellurium, and/or oxygen. The PI and his group are applying these rules to many different materials so that they can make large collections of nanoparticles using the same methods. This knowledge will allow researchers to more quickly make and study new materials that are predicted but have remained out of reach. The PI and his group are partnering with a network of faculty and students at local colleges and are providing new educational resources for helping students to understand how atoms arrange in solid-state materials.Technical SummaryThere is a growing disconnect between the scope of materials that can be predicted, including computationally, and those that can be made experimentally. Many materials of interest, especially metastable phases and complex nanoparticles, have no known pathways for synthesizing them. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, uses cation exchange reactions to modify the compositions of nanoparticles, producing large libraries of previously inaccessible nanoparticle materials through rational synthetic pathways. The PI and his group are establishing when and why existing synthetic guidelines break down and defining an expanded set of design rules that are broadly applicable across diverse metal chalcogenide and oxychalcogenide systems, including semiconductors having tunable band gaps. The researchers are studying how interfaces in heterostructured nanoparticles form and evolve and how layered intergrowth and superlattice compounds can be targeted through partial and complete cation exchange reactions that are chemo- and regio-selective. They are developing rational pathways to heterostructured nanoparticle megalibraries having millions of possible members, as well as new chemical reactions that break symmetry and introduce new structural motifs. This project is helping to bridge the gap between materials that can be predicted and those that can be synthesized, which will help to accelerate rational materials development. The PI and his group are partnering with a network of faculty and students at local colleges and are developing resources for visualizing crystal structures and their interrelationships, which allow students to analyze materials and understand their reactivity.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.