CAREER: Unveiling the structure and stability of prenucleation clusters and their roles in crystallization pathway and final crystal structure

NON-TECHNICAL SUMMARY

For over a century, scientists have been studying nucleation because it greatly affects various aspects of our lives, such as public health through drug production and dealing with urinary stones, as well as impacting industries like fertilizers and foods. Despite the long history of research, understanding the mechanism and influence of nucleation on crystal structures is still challenging due to the difficulty in characterizing tiny and random phenomena at the sub-nanoscale level.

This CAREER award, jointly funded by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR), aims to figure out how the structure of salt solutions changes as their concentration increases and how this structure affects the final crystal formation. To overcome the challenges, a levitation technique and powerful X-ray and neutron scattering will be combined, collaborating with Argonne National Laboratory and Oak Ridge National Laboratory.

The outcomes of this study will significantly enhance our understanding of the complex process of crystallization and its impact on the final crystal structure. This knowledge could benefit industries like pharmaceuticals, fertilizers, and batteries. Throughout the project, a consortium will be formed as an educational platform to promote diversity in the STEM field, educate young scientists and engineers, and share our findings with K-12 students, teachers, and parents in Iowa through existing outreach programs led by Iowa State University.

TECHNICAL SUMMARY

Nucleation dominates the subsequent crystallization, crystal growth, and the structure and properties of final crystals. Recently, nucleation has been reported to occur in multiple steps, forming pre-nucleation clusters (PNCs). It is apparent that PNCs play a critically important role in multi-step nucleation and the final crystal structure, yet their nature is poorly understood.

The rationale for the proposed research is that a mechanistic understanding of complex crystallization will likely provide new opportunities to develop a method to control the nucleation and growth of desired crystal phases. For this reason, this CAREER award, jointly funded by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR), aims to identify the concentration-dependent structural evolution of PNCs in aqueous salt solutions and the influence of solution structure on the crystallization pathways and the final crystal structure.

The current experimental obstacles will be overcome by integrating the solution electrostatic levitator (SEL) with synchrotron X-ray scattering at Argonne National Laboratory and neutron scattering at Oak Ridge National Laboratory. The long-term goal of the project is to develop a predictive framework to anticipate and control the multi-pathway and multi-step crystallization in various aqueous solutions to obtain desired microstructures in the final crystal products.

The proposed research will lead to a vertical-step advancement toward elucidating the mechanism of complex crystallization in electrolyte solutions and its influence on the final crystal structure.

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.