Experimental and theoretical study of o-substituent effect on the fluorescence of 8-hydroxyquinoline

Photoantibacterial Poly(vinyl)chloride Films Applying Curcumin Derivatives as Bio-Based Plasticizers and Photosensitizers

Herein we describe the design of natural curcumin ester and ether derivatives and their application as potential bioplasticizers, to prepare photosensitive phthalate-free PVC-based materials. The preparation of PVC-based films incorporating several loadings of newly synthesized curcumin derivatives along with their standard solid-state characterization is also described. Remarkably, the plasticizing effect of the curcumin derivatives in the PVC material was found to be similar to that observed in previous PVC-phthalate materials. Finally, studies applying these new materials in the photoinactivation of S. aureus planktonic cultures revealed a strong structure/activity correlation, with the photosensitive materials reaching up to 6 log CFU reduction at low irradiation intensities.

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

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.