EFFECT OF CHLORINATED HYDROCARBONS ON THE FLUORESCENCE EMISSION-SPECTRA OF 1,3-BIS-(1-PYRENE) PROPANE IN SOLUTIONS AND POLY(VINYL ALCOHOL) FILMS

This paper reports on our investigation of 1,3-bis-(1-pyrene)propane ( bpp) as a potential probe for chlorinated hydrocarbons. Changes in the emission spectra of bpp in methanol solutions, upon addition of methy lene chloride, chloroform, or carbon tetrachloride, are described. Dra matic changes in the emission spectrum were noted for CCl4, compared t o the other additives. These effects are explained by the preferential solvation of bpp by CCl4 and the formation of an excited-state comple x (exciplex), leading to quenching of the excimer emission and, ultima tely, the monomer emission. When solutions of bpp in the neat chlorina ted hydrocarbons were exposed over time to 350-nm light, changes in th e emission spectrum were noted for all solvents. Changes in both the e xcitation and emission spectra of bpp in CCl4 are related to exciplex formation, leading to irreversible formation of photochemical products . Poly(vinyl alcohol) films containing bpp were exposed to CH2Cl2, CHC l3 or CCl4 vapors, and trends consistent with the solution study were observed. A rapid decrease in bpp excimer emission, upon exposure to C Cl4 vapors, was observed. The effects of CCl4 in air and argon atmosph eres on the bpp/PVA films were also investigated, with oxygen quenchin g limiting the ability of this system to detect low concentrations of CCl4.