N-Phenylnaphthalen-1-amine can be used as a hydrophobic fluorescent probe for detecting the critical micelle concentration of surfactants, the concentrations of organolithium and organomagnesium reagents, and phase transitions of membrane lipids in cells. It is a fluorescent probe for odour-binding proteins (OBP), with a dissociation constant of 1.67 μM, an excitation wavelength of 337 nm, and an emission wavelength of 407 nm.