Mid-infrared Intraband and Localized Surface Plasmon Resonance Spectroscopies of Doped Semiconductor Nanocrystals

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The Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry supports Professor Masaru Kuno and his research group at the University of Notre Dame to study the optical properties of semiconductor nanocrystals. Molecules and semiconductor nanocrystals react with light to exhibit unique "fingerprints" that can be used in their identification. Professor Kuno's research contributes to the development of new analytical detection technologies for monitoring trace amounts of chemical and biological substances that are important to health, safety, and national security. Understanding fundamental optical properties of semiconductor nanocrystals also has implications in the development of low cost infrared cameras in cellphones and infrared detectors that can operate at room temperature. Professor Kuno and his group develop hands-on outreach activities such as thermal imaging kits to bring interest lower income and minority students in the South Bend Community School system in STEM careers. Recent advances in nanocrystal (NC) synthesis have enabled the development of stable, self-doped semiconductor NCs with significant doping densities. These NCs exhibit mid-infrared intrabands and localized surface plasmon resonances (LSPRs). However, little is understood about their dependence on the NC size, shape, surface chemistry, and doping density/dopant activation. This is due to the inhomogeneities present in doped NC ensembles, which is unavoidable in current colloidal NC syntheses. Limited means exist for conducting highly sensitive, mid-infrared optical measurements of single NCs. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Kuno’s research team addresses this important need in the field. The research team employs a newly developed, super-resolution infrared absorption technique, called infrared photothermal heterodyne imaging (IR-PHI), to measure the local absorption of self-doped NCs. These measurements, in turn, can enable better understanding of the fundamental properties of these semiconductor NCs and of the evolution of intraband transitions into collective LSPRs at high doping densities.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.