Effects of photochemical reactions of pyrene in alcohol and aqueous solvent systems on spectroscopic analyses

Although pyrene is a popular fluorescent molecular probe in analytical and bioanalytical chemistry, its photostability is hardly understood. This paper reports a surprising finding that pyrene undergoes significant photochemical reactions in alcohol and aqueous solvents under the condition of exposing a sample solution to excitation irradiation in an emission spectrometer for a short period of time. The reactions yield at least two photoproducts, whose fluorescence spectra overlap severely with that of pyrene. Implications of pyrene photochemical reactions in alcohol and aqueous solvent systems to existing and future applications of pyrene as a fluorescent molecular probe are discussed.