Novel Long-Wave Near-Infrared Fluorescence Bands in Tricarbocyanine Dyes

Long-wave near-infrared (LWNIR) dyes have garnered significant attention, particularly in biomedical applications, due to their ability to enhance light absorption, making them highly effective for in vivo imaging and phototherapy. Among these dyes, cyanines are notable for their broad tunability across the ultraviolet (UV) to LWNIR spectrum and their ability to form J-aggregates, which result in narrow absorption and enhanced emission peaks, often accompanied by a red-shift in their spectra. In this study, we investigate the fluorescence properties of three known tricarbocyanine dyes, uncovering new emission bands in the LWNIR region. These dyes exhibit two distinct fluorescence peaks between 1605 and 1840 nm, with an emission tail extending up to ~2200 nm. The intensity of these peaks varies depending on dye concentration. Furthermore, we assess the photostability, pH sensitivity, and thermal stability of the dyes, providing key insights into their potential for stable and efficient biomedical applications. Our study provides a deep investigation of the spectral characteristics of these dyes, seeking to enhance their potential application in biomedical imaging.