Widely used as a fluorescent probe in biological and analytical applications due to its pH-sensitive emission properties. It is commonly employed in intracellular pH measurements and membrane permeability studies. Its carboxyl group allows for conjugation to biomolecules such as proteins, antibodies, and nucleic acids, making it useful in labeling and detection techniques including fluorescence microscopy, flow cytometry, and immunoassays. Also utilized in environmental studies to trace fluid flow and detect leaks in water systems owing to its high visibility and stability in dilute solutions.