Establishing the synthesis/structure relationship of molybdenum/lead chalcogenide quantum dot mesocrystals

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Non-technical summaryWith this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Professor Tobias Hanrath at Cornell University will explore the synthesis-structure relationships of a novel class of materials that combines nanoparticles with two-dimensional (2D) materials. By analogy to the rock-paper-scissors game, the investigators will use colloidal nanoparticles (i.e., rocks) to template the formation of molybdenum sulfide sheets (i.e., paper) on specific sections of the nanoparticle. Instead of scissors, the proposed synthesis approach leverages the well-defined nanoparticle shape (e.g., truncated cubes) to define the geometry of the particle-sheet composite. This project will have significant broader impact beyond the creation of new knowledge of scientific and societal importance, potentially leading to the development of new nanostructured composite materials with unique optical, electronic, and catalytic properties. Graduate students will receive extensive training and experience at the confluence of material fabrication and characterization approaches to investigate, understand and predict the formation of composite nanostructures. Outreach and education are closely integrated with the scientific work. The investigators will develop a ‘back-to-the-future’ workshop to engage participants by developing their vision for the future of their specific research field, the broader technological implications, and their personal roles and opportunities in bringing this future to fruition. Technical Summary The overarching objective of the proposed project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, is to establish the foundational synthesis/structure relationship of molybdenum/lead chalcogenide quantum dot mesocrystals. Mesocrystals are defined as assemblies of smaller constituent crystals arranged with high degree of translational and orientational ordering in their superlattice sites. Access to colloidal quantum dot (QD) building blocks with precisely defined size, shape, and composition as well as concurrent progress in understanding of and control over directed assembly and attachment have enabled remarkable advances in QD mesocrystals. Currently available QD mesocrystals are limited to single composition structures, yet the scientific and technological evolution of isolated QDs has taught us that moving from single-components to multi-composition heterostructures (e.g., core-shell or Janus-like) introduces advanced and programmable functionalities. The PI has identified the synthesis and analysis of heterostructured QD mesocrystals as a scientifically interesting and technologically important research challenge. The PI embraces the challenge of establishing processing/structure relationships as an opportunity to closely integrate synthesis, assembly, and materials characterization. The proposal presents a hypothesis-driven approach with three complementary objectives focused on formation of facet-specific PbX-(MoS2)m misfit layer heterostructures, and directed assembly of isolated PbX-(MoS2)m into a new class of superstructures. The proposed research presents an exciting opportunity to significantly improve upon the knowledge of QD mesocrystals with properties by design. The goals of the proposed research are ambitious, and the generated knowledge will significantly advance basic understanding, design, predictability and control over heterostructured QD mesocrystals with compelling far-reaching prospects for future advances in electrocatalysis and optoelectronicsThis 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.