Synthesis and imaging of near-infrared I and II quantum dot heterostructures
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Citation
Abstract
Quantum dots (QDs) are remarkable optically active nanomaterials that present excellent brightness and photostability, emission wavelength tunability, and versatile functional groups in near-infrared (NIR) fluorescence imaging. These qualities have enabled preclinical imaging of anatomical features and therapeutic delivery. Since the first synthesis of colloidal QDs thirty years ago, advances in QD chemistry techniques have produced innovative QD core/shell structures, but most of the benefits from these developments have been realized in optoelectronic applications such as solar cells and displays. There remains an ongoing need for more powerful QD contrast agents in biomedical imaging applications with improved chemical and optical stability, tunability within the NIR-I (700–900 nm) and NIR-II (1000–1700 nm) biological imaging windows, and simpler synthesis methods. In this thesis, I present innovations to the synthesis and imaging of QDs to improve their accessibility and utility in NIR biological imaging. First, I design an alternative synthesis for inverted indium phosphide QDs emitting in the NIR-I bioimaging window by utilizing stable, non-pyrophoric indium phosphide clusters acting as single source precursors. Careful study of cluster reactivity allows for production of thick indium phosphide shells while limiting nucleation-based side reactions. Second, I develop biostable, NIR-II lead-sulfide quantum dots by adding a zinc sulfide shell layer through multiple synthesis variations. In contrast to typical high-temperature (200 > °C) zinc sulfide syntheses, highly reactive precursors at low temperatures (120 < °C) produce sufficiently thick outer shells while preserving the integrity of the optically active lead sulfide core. The zinc sulfide shell maintains QD optical stability in harsh, lysosomal-like environments. Lastly, I improve the dynamic range of a preclinical imager outfitted with an InGaAs camera to enhance imaging of our bright, NIR-II-emitting QDs in small animal models. I modify classical high dynamic range (HDR) imaging methods by accounting for exposure time-dependent InGaAs camera noise with dynamic denoising and pixel weighting range adjustment. This HDR imaging workflow produces quantitatively accurate radiance maps that reflect true incident light at each pixel without worry of sensor saturation from high local fluorophore concentrations, such as in the liver or spleen.
Description
2026
License
Attribution 4.0 International