Pyrene photochemical species in commercial clays

► Pyrene photochemistry on three commercial clays was investigated. ► Fluorescence monomers and excimers from pyrene were detected. ► Excimer formation is function of the amount Pyrene of adsorbed on the clay. ► Emission from pyrene crystals was detected for high loading samples. ► Lifetime distribution analysis identified all pyrene emissions and their lifetimes.