Developing a Mechanistic Picture of the Synthesis and Assembly of Inorganic Nanomaterials

The properties of inorganic nanoscale particles are largely determined by their surfaces, as the fraction of surface atoms can approach unity as the size approaches 1 nm. As a result, the coordination of ligands to the particle surface can quickly become the dominant energetic contribution to the system and therefore provides an opportunity to use molecular design principles to control the formation of well-defined inorganic materials. However, challenges in characterizing the ligand-particle interface and a lack of mechanistic understanding of the role of ligands in surface reactions has limited the implementation of these structures in a variety of applications. In this talk, I will discuss recent efforts by my group to address fundamental questions in nanoscale surface chemistry and leverage these insights to construct nanoparticle-based materials with novel properties. First, I will show that advanced cryogenic and liquid-phase transmission electron microscopy techniques can be used to map the spatial distribution of ligands on a nanoparticle surface and directly observe the dynamics of symmetry breaking during particle growth. Second, I will report our finding that the “seed” nanoparticle that has been widely used as a precursor in anisotropic gold particle syntheses over the last two decades is, in fact, an atomically-precise inorganic cluster consisting of a 32 atom Au core with 8 halide ligands and 12 neutral ligands constituting a bound ion pair between a halide and the cationic surfactant: Au₃₂X₈[AQA⁺•X^-]₁₂ (X = Cl, Br; AQA = alkyl quaternary ammonium). This result establishes a molecular precursor with well-defined surface ligands as the progenitor to larger nanostructures and is a critical first step in understanding particle growth mechanisms. Finally, I will show how control over the surface chemistry of tetrahedron-shaped particles facilitates their assembly into novel superlattices with chiral and quasicrystalline order. These materials, whose construction is enabled by the atomic-scale understanding developed in my lab, will form the basis for future optical and/or mechanical metamaterials, highlighting the power of molecular control over inorganic matter.

Biography

Matt Jones is an Assistant Professor of Chemistry and Materials Science & Nanoengineering at Rice University. The expertise of his research group covers the fields of inorganic nanoparticle synthesis, surface chemistry, liquid-phase transmission electron microscopy, and nanoscale self-assembly. Matt is known for discovering an atomically-precise gold nanocluster as a precursor in the synthesis of anisotropic nanostructures and developing methods to assemble nanoparticles into chiral superlattice phases for the high-throughput fabrication of plasmonic metamaterials. He is the recipient of numerous awards and honors including the Packard Fellowship for Science & Engineering, an NSF CAREER award, a Victor K. LaMer Award Finalist, an Arnold O. Beckman Postdoctoral Fellowship, and an NSF Graduate Research Fellowship. He graduated from Carneige Mellon University with B.S. degrees in both Materials Science and Biomedical Engineering, he received his Ph.D. from Northwestern University under the guidance of Chad Mirkin, and completed a postdoctoral fellowship with Paul Alivisatos at UC Berkeley before starting his independent career at Rice.