DDAO is a promising near-infrared (NIR) red fluorescent probe with tunable excitation wavelength (600-650nm) and longemission wavelength(λem=656nm). DDAO can de desiged for detection of the activities of different enzymes such asβ-galactosidase,sulfatase, proteinphosphatase2A, carboxylesterase 2, humanalbumin andesterases.