RESUMO
In the present work, attempts have been made to prepare scintillating nanoparticle composite films of Ce3+ -doped Y3 Al5 O12 (YAG:Ce) embedded in a polystyrene (PS) polymer. A YAG:Ce phosphor has been previously synthesized using the sol-gel method. YAG:Ce-PS composite films of 250 ± 30 µm thickness were prepared using a solvent casting procedure with different PS/solvent concentration and a different mass ratio between nanoparticles of YAG:Ce and PS. X-ray diffraction analysis confirmed that the YAG:Ce powders were successfully prepared. Using thermogravimetric analyses and differential scanning calorimetry, we found that the glass transition temperature (Tg) and thermal degradation were shifted to higher temperatures for composite films relative to pure PS. Photoluminescence showed the yellow emission of the Ce3+ -doped YAG phosphors, which was attributed to the 5dâ4f transition of Ce3+ ion and the intensity of the emissions changed with the mass ratio of the YAG:Ce nanoparticles incorporated in the polymer and with the concentration of the polymer solution.
RESUMO
An efficient in situ condensation of citronellal, the main constituent of Eucalyptus citriodora essential oil (51%), with different amine derivatives of 2,3-diaminomaleonitrile and 3-[(2-aminoaryl)amino]dimedone has led to novel chiral benzodiazepine structures. All reactions were precipitated in ethanol and pure products were obtained in good yields (58-75%) without any purification. The synthesized benezodiazepines were characterized by spectroscopic techniques, namely 1H-NMR, 13C-NMR, 2D NMR and FTIR. Differential Scanning Calorimetry (DSC) and HPLC were used to confirm the formation diastereomeric mixtures of benzodiazepine derivatives.