Alexa Fluor 680 Carboxylic Acid (AF680 COOH) is the carboxylic acid derivative of Alexa Fluor 680, emitting near-infrared fluorescence with bright, stable signals and excellent photostability. Its spectral properties are similar to Cy5.5, with excitation/emission maxima around 680/705 nm, providing reliable detection in fluorescence imaging. It is a widely used functional near-infrared fluorescent probe in life science research.