Abstracts
Optical spectroscopy of inorganic phosphors
Structural and Spectroscopic Studies of Rare Earth-doped Polyphosphate CoacervatesRoberta S. Pugina1, Renan M. Caldeira1, Sidney J. L. R.1, Douglas F. F.1
1Universidade Estadual Paulista (UNESP), Instituto de Química de Araraquara
E-mail: roberta.pugina@hotmail.com
The Coacervation process refers to the aggregation of colloidal particles in solution. In this case, the droplets of dense polymeric phase formed during liquid-liquid phase separation also called coacervates are extended by colloidal particles. An example of a material that can be formed by this process is polyphosphate coacervates, which have glassy characteristics. In this work, polyphosphate coacervates doped with paramagnetic Ln3+ ions (Ln = Dy, Ho and Tb) were prepared with the aim of obtaining materials in the form of films that present magneto-optical properties to be explored. The coacervation process was induced by adding a solvent with a high dielectric constant, such as ethanol, to a solution of Ln-polyphosphate. The materials obtained were structurally characterized via FTIR, XRD and Raman spectroscopy. Undoped coacervates generally have amorphous structures. XRD analyzes showed that after the addition of Ln3+ ions, the formation of ortho and pyrophosphate crystalline phases occurred. From Raman scattering, we identified that the precursor presents two main specific vibration modes at 743 cm-1 and 1009 cm-1, attributed to the symmetrical stretches in P-O-P (bridges) and P-O (terminal), respectively. For samples containing Ln3+, it was observed that the υs(P-Ot) band shifted from 1009 to 1017 cm-1. The spectroscopic properties of Ln3+ ions were evaluated via photoluminescence spectroscopy. In the emission spectra of samples containing Dy3+ and Ho3+ ions, it was possible to observe, in a more pronounced way, an emission band centered at 576 nm and 669 nm, referring to the transitions 7F9/2 → 6H13/2 and 5F5 → 5I8, respectively. The samples doped with Tb3+ ions showed atypically intense emission in the region close to 491, 546 and 686 nm, due to the transitions 5D4 → 7F6, 7F5, 7F4. In sequence, these materials will be evaluated for their magneto-optical properties via Faraday rotation angle experiment.
Keywords: Coacervate, Lanthanide Spectroscopic
Acknowledgments: Chemistry Institute of Araraquara, Universidade Estadual Paulista (UNESP) CNPq FAPESP