Investigation of the Structure and Optical Properties of Polymethine-Based NIR-II Fluorophores Using Many-Body Perturbation Theory: GW-BSE Approaches

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