ABSTRACT

With support from the Macromolecular, Supramolecular and Nanochemistry (MSN) Program in the Division of Chemistry, Professors Robinson and Dshemuchadse at Cornell University are exploring how the atomic organization in nanoclusters?the missing link between few-atom molecules and larger crystals?can change, depending solely on their size. The atomic arrangement of most materials, from nanoparticles to everyday bulk materials, is known. But for nanoclusters, which are smaller than nanoparticles, surface effects can have a large influence on the stability of the atomic structure. The origin of the atomic stability in magic-sized clusters is investigated with experimental techniques and computer simulations. The detailed control of nanocluster structures and the ability to precisely manipulate the defined and rapid changeover from one atomic arrangement to another could have applications in optical communications, energy harvesting, or quantum computing. Professor Dshemuchadse and her group are working on the visualization of nanoparticle growth simulations to be made available to the public as interactive educational online materials. Additionally, Professors Robinson and Dshemuchadse are designing a demonstration kit on crystal structures, which illustrates the ordering principles that govern the structure of materials for K-12 teachers across the US.

The objective of the project is to determine the relationship between the atomic ordering and isomerization in inorganic nanoclusters and nanoparticles. In cadmium sulfide, nanoclusters of very specific atomic arrangements of so-called "magic" sizes have been observed to transform their structure. When cadmium chalcogenides are synthesized into discrete cluster sizes, forming so-called "magic-sized nanoclusters", they are able to coherently transform between two distinct structures, or isomerize. This project is investigating the geometric frustration induced by the atomic structural arrangements, and how the frustration may influence isomerizations. The origin of this behavior is being investigated experimentally through nanocluster synthesis and post-synthetic modifications, as well as Monte-Carlo simulations to model the stability of different cluster configurations. Understanding and being able to control the reversible crossover from local-cluster to bulk-crystalline behavior in nanoparticles can lead to inorganic materials undergoing solid-solid transitions designed for switching or sensing behavior, which can find application in energy harvesting or quantum computing. The team is making nanoscience accessible to the public by creating visualizations of self-assembly simulations and providing interactive online materials. They are also designing an educational demonstration kit on crystal structures and their relationship with materials properties for lending library modules.

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.

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