Abstracts

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 υ_s(P-O_t) 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 ⁷F_9/2 → ⁶H_13/2 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.