Investigation of\nthe Structure and Optical Properties\nof Polymethine-Based NIR-II Fluorophores Using Many-Body Perturbation\nTheory: GW-BSE Approaches

Fluorescence imaging is a widely used technique for detecting\npathophysiological\nmicroenvironments and guiding fluorescence-guided therapy owing to\nits noninvasiveness, high spatiotemporal resolution, ease of operation,\nand real-time monitoring capabilities. In particular, NIR-II materials\nare promising for fluorescence imaging applications because they exhibit\nreduced light scattering and absorption by biological tissues, enabling\ndeeper imaging with improved spatial resolution and contrast compared\nto visible or first near-infrared imaging. NIR-II materials refer\nto those that emit in the second near-infrared region of the electromagnetic\nspectrum, spanning wavelengths from approximately 1000 to 1700 nm.\nThe emission peaks of organic fluorophores within the NIR-II window\nare of particular interest due to their minimal biotoxicity, in vivo\nbiocompatibility, and biodegradability. In this study, we investigated\na new series of NIR-II fluorescent polymethine-based dyes and their\nNIR-II absorption properties using density functional theory and the\nGW-BSE approximation. Our calculated maximum absorption peak under\nthe GW-BSE approximation showed good agreement with experimental results,\ndemonstrating the potential of these dyes for NIR-II fluorescence\nimaging applications.