Fluorescence and photophysical properties of xylene isomers in water: with experimental and theoretical approaches.

ABSTRACT: A thorough analysis of the photophysical properties involved in electronic transitions in excitation-emission spectra of xylene isomers has been carried out using the time-dependent density functional theory (PBEPBE/6-31?+?G(d,p)) method. For the first time a structural and spectroscopic investigation to distinguish isomers of xylene, a widespread priority pollutant, was conducted experimentally and theoretically. The fluorescence properties of xylene isomers (sole and mixture (binary and ternary)) in water were studied. The fluorescence peak intensities of xylenes were linearly correlated to concentration, in the order of p-xylene?>?o-xylene?>?m-xylene at an excitation/emission wavelength (ex/em) of 260?nm/285?nm for o-, m-xylene and ex/em 265?nm/290?nm for p-xylene at the same concentration. The theoretical excitation/emission wavelengths were at ex/em 247?nm/267?nm, 248?nm/269?nm and 251?nm/307?nm for o-, m- and p-xylene, respectively. The vertical excitation and emission state energies of p-xylene (ex/em 4.94?eV/4.03?eV) were lower and the internal conversion energy difference (0.90?eV) was higher than those of m-xylene (ex/em 5.00?eV/4.60?eV) (0.4?eV) and o-xylene (ex/em 5.02?eV/4.64?eV) (0.377?eV). The order of theoretical emission and oscillator strength (0.0187?>?0.0175?>?0.0339) for p-xylene?>?o-xylene?>?m-xylene was observed to be in agreement with the experimental fluorescence intensities. These findings provide a novel fast method to distinguish isomers based on their photophysical properties.

SUBMITTER: Khan MFS 

PROVIDER: S-EPMC5830770 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature