PROGRAMMABLE QUANTUM DEFECTS FOR MOLECULARLY SELECTIVE NEAR-INFRARED SENSING

Abstract

This dissertation establishes a unified framework for engineering programmable quantum defects in low-dimensional nanomaterials as a platform for near-infrared (NIR) nanosensing. Organic color centers (OCCs), formed through covalent sp³ functionalization, create localized electronic states that enable tunable defect photoluminescence (PL). By controlling defect electronic structure, chemical environment, and spatial location, this work demonstrates that quantum defects can function as robust NIR sensing elements. First, defect pairing in boron nitride is shown to generate deeply localized mid-gap states that enable strong NIR transitions (0.21–0.63 eV) with oscillator strengths up to 6.5 times higher than pristine band-gap transitions. Defect–defect coupling further enables continuous tuning of optical properties through spatial control. Second, a molecular wedging strategy overcomes van der Waals bundling in carbon nanotubes, enabling sonication-free dispersion of long, individualized nanotubes with enhanced photoluminescence quantum yield. Wedging also improves chemical accessibility, enabling homogeneous defect incorporation and control over defect pairing chemistry. Finally, endocavity defects introduce spatially defined quantum states within nanotubes, enabling sensing of confined chemical environments and molecular transport. Complementary edge-localized defect systems further demonstrate high-throughput sensing capabilities, where multiple nanotube edges can be simultaneously monitored to detect environmental changes such as pH through defect PL shifts. Taken together, these results establish programmable quantum defects as a foundation for robust and tunable NIR nanosensing platforms.