Understanding How Ligands Dictate Nanocrystal Shape Using Force Spectroscopy

University Of California-San Diego, La Jolla CA

Investigators

Abstract

With the support of the Chemical Measurement and Imaging Program and the Macromolecular, Supramolecular & Nanochemistry Program, both in the Division of Chemistry, Professor Andrea R. Tao of the University of California, San Diego, will develop new methods and tools to understand how molecules stick and arrange themselves on nanoscale particles. While these particles are used in a variety of applications ranging from medicine to chemical processing, little is known about how molecules interact with their surfaces and how these interactions can lead to particles with specific geometric shapes. Professor Tao will study how these molecular interactions change when particles are in either air or liquid, which should address long-standing questions about how shaped particles form during chemical synthesis. This project will provide unique research opportunities for undergraduates, graduates, and high school students to learn about nanomaterials and surface chemistry. This project will contribute directly to workforce development in nanomaterials, materials processing, and advanced characterization tools. This project will also support outreach efforts and student exchanges with two partner R2 institutions. Shape-directing ligands such as surfactants, polymers, and chiral molecules play a critical role in directing the nucleation and growth of anisotropic nanocrystals (NCs). This project will develop a new understanding of how molecular agents and surface ligands influence the shape of inorganic NCs using liquid-phase and in situ atomic force microscopy (AFM) mapping and force spectroscopy measurements. This work will develop techniques such as NC immobilization that will enable nanoscale spatial resolution for chemical imaging of NC surfaces and for probing different ligand interactions. A major novelty of this work is AFM imaging of single NCs that is near or at the single-molecule limit and is conducted in different solvent environments. These experiments will address long-standing questions regarding the key interfacial phenomena that dictate ligand shell structuring and NC shape control, including the role of solvent in cooperative ligand-ligand interactions. The outcomes of this project will provide insights into NC growth, chemical reactivity, and the role of supramolecular order in NC behavior. This research will also lead to new tools and techniques that can be broadly applied to the study of inorganic-organic interfaces, correlating atomic and molecular behavior to nano- and macroscale phenomena. 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.