Uncovering Reaction Pathways in Solution-Phase Materials Synthesis

PART 1: NON-TECHNICAL SUMMARY Modern technologies depend on new materials for advanced energy technologies, better catalysts, improved separations, and advanced manufacturing. Many of these materials form through reactions in solution where dissolved ions and molecules assemble into solid products. These reactions can access wide-ranging materials, but they are difficult to control because synthesis is often treated as a "black box". Most often, researchers choose starting chemicals and reaction conditions, then study the final material after the reaction is complete. What remains hidden is the sequence of steps that connects the starting mixture to the final product. Small changes in chemicals, additives, solvent, temperature, or reaction environment can redirect this pathway and lead to different products. This blind spot limits the ability to understand why a synthesis succeeds, why it fails, or why nominally identical experiments produce different outcomes. This project, supported by the Solid State and Materials Chemistry Program in NSF’s Materials Research Section A, opens the black box by watching how materials form as reactions proceed. It combines time-lapse optical imaging, X-ray measurements, and custom reactors that allow many reactions to be compared under controlled conditions. By following reaction evolution over time, Dr. Karena Chapman and researchers in her group identify when particles first form, how they grow and settle, and how different pathways produce different final materials. This approach provides a basis for moving synthesis away from trial-and-error and toward reproducible control of material formation. The project serves the national interest by advancing the reliable preparation of sustainable, earth-abundant materials relevant to advanced energy technologies. It trains graduate students and postdoctoral researchers in materials synthesis, advanced characterization, reactor design, data analysis, and scientific communication. A key broader impact is the development of low-cost time-lapse imaging methods using simple web cameras. These tools make reaction monitoring accessible to laboratories without advanced facilities, broaden participation across institutions, and create open protocols, analysis tools, and instructional resources for the wider community. PART 2: TECHNICAL SUMMARY Solution-phase synthesis provides access to inorganic and hybrid materials whose properties depend on phase, particle size, crystallinity, and defect structure, yet reaction outcomes are often difficult to predict or reproduce. This project, with support from the Solid State and Materials Chemistry Program in NSF’s Materials Research Section A, establishes a pathway-based approach to understanding and controlling solution-phase materials synthesis. By integrating time-resolved X-ray scattering, X-ray spectroscopy, and time-lapse optical imaging with multiplexed reactors, the project provides a uniquely powerful platform for resolving reaction pathways that have previously been hidden. These measurements help uncover how nucleation, growth, phase selection, and defect incorporation evolve under controlled perturbations to precursor chemistry, additives, solvent composition, temperature profile, and reactor environment. Optical imaging provides continuous, full-field monitoring of reaction kinetics and emergent heterogeneity across many reaction conditions in parallel. Depth-resolved scattering of undisturbed product columns reconstructs the sequence of phase formation and sedimentation. Targeted synchrotron X-ray diffraction, pair distribution function analysis, small-angle X-ray scattering, and X-ray absorption spectroscopy provide structural and chemical information on selected pathways, transient species, nuclei, and products. The project focuses on nanoscale metal oxides and metal-organic frameworks as model systems. Expected outcomes include reproducibility benchmarks, mechanistic links between reaction conditions and product structure, and design rules for selective synthesis of metastable and functional materials. The project establishes a mechanistic framework that advances beyond empirical trial-and-error approaches, enabling the rational design of solution-phase synthesis. 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.