2025/09/24 by Xinqi Zhou, Kayla J. Belavek, Ruwen Yin +10 · 1 voice
Chemical Engineering · Materials Science · Engineering · #Analytical Chemistry and Sensors #Luminescence and Fluorescent Materials #Nanoplatforms for cancer theranostics
paper · doi:10.26434/chemrxiv-2025-f17vm
openalex publication_date 2025/09/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/15
Near-infrared (NIR) fluorophores are foundational for fluorescence imaging in multicellular organisms. However, their fluorescence brightness, defined as the product of the molar extinction coefficient (ε) and fluorescence quantum yield (ΦF), often pales when compared to that of visible dyes. Although strategies exist to substantially enhance the brightness of visible dyes, when applied to NIR dyes, these approaches lead to only marginal gains. Here, we report a novel and generalizable strategy to improve NIR fluorophore brightness by leveraging the multiple resonance effect (MRE). Using a library of NIR xanthenes as a proof-of-principle, we demonstrate the ability to enhance fluorescence brightness up to ~240 fold by simultaneously improving ε and ΦF. Experimental and computational studies indicate that increased fluorescence brightness is achieved through a decrease in vibronic coupling of the dye, leading to reduced rates of non-radiative decay. Thorough photophysical studies provide a dataset that can be used to accurately predict the properties of new NIR dyes. Using insights from the MRE approach to rhodamine, we developed a new, MRE-inspired oxazine which shows substantial improvement in whole-mouse imaging. This MRE-inspired approach to organic NIR fluorophores improves existing NIR scaffolds and provides a conceptual framework for guiding the design of organic fluorophores in the NIR and visible windows.