Controlling the Synthesis and Placement of Organic Color-Centers with Light

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With support from the Macromolecular, Supramolecular and Nanochemistry (MSN) program in the Division of Chemistry, Professor YuHuang Wang of the University of Maryland College Park will address the synthetic challenge of the controlled placement of organic color-centers, also known as quantum defects, on the surface of single-walled carbon nanotubes. These atomic defects can emit photons—the elementary particles of light—one at a time, creating a source of single photons; however, they typically exist randomly within the solid, lacking the synthetic control required for achieving control over atomic structure, placement on the surface and color tuning. Controlled placement of organic color-centers on the surface of single-walled carbon nanotubes would enable the nanotubes to emit single, short wave infrared photons at room temperature. Success in accomplishing the objective of the project would enable the creation and tuning of identical organic colo- centers emitting single wavelengths for emerging applications in bio-imaging, molecular sensing, and quantum information science. In addition to the involvement of graduate and undergraduate students, particularly from under-represented groups, in cutting-edge research, the project will also involve developing engaging nanoscience and technology demonstrations based on project results and sharing these with others in community outreach events. In this project, Professor Wang and his team will synthesize model defect color-centers by covalently attaching small functional groups to semi-conducting carbon nanotube hosts using organic chemistry. When the nanotube is excited, the resulting excitons—or electron-hole pairs—are harvested by the organic color-center to produce bright shortwave-infrared single photons whose “color” sensitively depends on the atomic configuration of the defect site. The team will use this optical fingerprint to study how these organic color-centers can be generated, erased, or corrected on the carbon lattice of the nanotube semiconductor using light. This work, if successful, will pave the way to attaining atomic control and deterministic placement of these defect color-centers. The team will also work to advance a method to enable tracing of dark excitons and quantification of the exciton-to-photon conversion efficiency at the defect—a property of fundamental importance to quantum light sources and to the understanding of the excited states of these nanostructures.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.