EAGER: Emergent Quantum Confinement-Induced Properties of a New Class of Aromatic Ligand-Passivated Hybrid ITO Nanocrystals

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NON-TECHNICAL SUMMARY Nanocrystals (NCs) have inorganic core dimensions on the order of a billionth of a meter. It is challenging to assemble them into larger superstructures. Along these lines, this award, which is supported by the Solid State and Materials Chemistry program in the Division of Materials Research, addresses the forefront of modern nanoscience and nanotechnology-related research. Using polymers as solvents to synthesize ultrasmall tin-doped indium oxide (ITO) NCs this project targets a material with potential applications in fabrication of improved optoelectronic devices such as photovoltaics, light-emitting diodes, photodetectors, and photocatalytic solar fuel production. The project investigates how surface attachment of appropriately chosen organic molecules produces hybrid-ITO NCs (artificial molecules), and as a consequence alters the optoelectronic and electrochemical properties of the individual ITO NCs and their assemblies. Traditionally these properties are varied by changing the inorganic core size of NCs. Because of the different underlying mechanism to tune properties, the impact of this research is expected to be far-reaching in the context of new materials design, advancing molecular level understanding in nanoscience and materials chemistry, and economic expansion and sustainability. Additionally, this project provides multidisciplinary research training opportunities, including inorganic chemistry, materials science and nanotechnology, for graduate and undergraduate students. Through these activities the principle investigator fosters the next generation STEM educators and innovators. TECHNICAL SUMMARY Ligand-passivated nanocrystals (NCs) are of immense interest to chemists, physicists, and materials scientists, because NC-ligand interfacial electronic interactions and bonding greatly impact their chemical and physical properties. Through this Solid State and Materials Chemistry-funded project the principle investigator synthesizes and characterizes a new class of ultrasmall, quantum confined hybrid-ITO NCs. Functionalizing the NC core with uniquely designed aromatic ligands allows the researchers to manipulate the interaction and electronic coupling of interfacial energetic states between the inorganic (ITO core) and organic surface ligands. This leads to new structure-function relationships, which are fundamentally different from those previously characterized in traditional larger ITO NCs. Specific objectives of this project include: (1) experimentally characterizing the optoelectronic properties of this new class of hybrid-ITO NCs, both to understand the fundamental chemical and structural processes that exist at the NC-ligand interface and to control electronic coupling between individual energetic state of the NC and ligands, (2) correlating experimental spectroscopic data with computational models to predict the effects of the NC size and the electronic and/or chemical structure of surface ligands on optoelectronic properties, and (3) predictably assembling hybrid ITO-NCs into artificial solids and then measuring charge transfer and transport properties in the solid-state with the aim of understanding mechanisms controlling such phenomena. Taken together, results from this project are crucial in ultimately guiding the preparation of novel inorganic-organic hybrid nanomaterials to increase efficiency of solid-state optoelectronic devices and photocatalysts.