RESUMEN
A blue-emitting phosphor designed by lanthanum (III) coordinated with two 1,10-Phenanthroline and three nitrate ligands, [La(Phen)2(NO3)3], was obtained by an effective and simple precipitation method. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) revealed the coordination modes in the compound and the chemical structure, crystallizing in a monoclinic system in the C2/c space group. The luminescence properties, absolute quantum yield (Ï), and luminescence lifetime decay (τ) were determined by photoluminescence spectroscopy. Under a 350 nm excitation, the sample presents three emission bands corresponding to the π* â π transitions belonging to the organic ligand. The luminescence lifetime (τ) was determined through a monoexponentially fit, obtaining a value of 5616 ns. The [La(Phen)2(NO3)3] complex exhibits an absolute quantum yield of 3 % with the same excitation conditions. In addition, the photometric analysis shows that the luminescent response to a 350 nm excitation is that of a blue-emitting high-purity phosphor with 96 % and chromatic coordinates of 0.15, 0.05. The temperature-dependent luminescence properties revealed considerable thermal stability in the 20-150 °C range with a signal loss of 47 % and an activation energy of thermal quenching (ΔE) of 0.13 eV, the first value reported for a lanthanum complex based on 1,10-Phenanthroline.
RESUMEN
Quercetin, rutin, naringin, hesperidin and chrysin were tested as substrates for chloroperoxidase to produce reactive quinones to graft onto chitosan. Quercetin and rutin quinones were successfully chemically attached to low molecular weight chitosan. The quercetin-modified chitosan showed an enhancement of plastic, antioxidant and antimicrobial properties as well as of thermal degradability. Finally, chitosan-quercetin films visibly decreased enzymatic oxidation when applied to Opuntia ficus indica cladodes.
