Used as a near-infrared fluorescent dye in biological imaging due to its deep tissue penetration and low autofluorescence. Commonly applied in in vivo imaging, tumor detection, and lymph node mapping. Also utilized in laser dyes and as a spectral sensitizer in photodynamic therapy research. Its strong fluorescence makes it suitable for tracer studies and cellular labeling. May be used in some chemical sensors responsive to environmental changes like pH, though primarily for imaging applications.