The binary system NaPO3-WO3 has been widely studied for its specific properties of photochromism and non-linear absorption. The controlled growth of metallic nanoparticles in glasses is also a very interesting, innovative and current research theme since they can aggregate new properties to the glasses due to their characteristic surface plasmon resonance (SPR). For instance, SPR can enhance the non-linear optical properties and the luminescence efficiency of trivalent rare earth ions - important laser emitters, increase the intensity of Raman scattering and add different thermal properties to the samples. Recently, some collaborators have successfully prepared homogeneous and transparent glasses of sodium polyphosphate and tungsten oxide, in the binary system NaPO3-WO3, with WO3 concentrations of 30, 40 and 50 mol% and containing Au, Pt and Ag nanoparticles. The characteristic SPR bands of each nanoparticle were observed in the UV-VIS spectral region for all the studied samples. The samples presented different thermal behavior when compared to those undoped, such as lower glass transition temperature Tg values and the shift of crystallization peak Tx to lower temperatures suggesting that the nanoparticles act as seeds for volumetric crystallization. Raman studies suggested that the sample doped with Au nanoparticles could be potential candidates for Surface Enhanced Raman Spectroscopy (SERS) due to overlap of Raman and SPR bands. In this project, we intend to further explore these systems with the addition of trivalent rare earth (RE) ions to the glasses. On one side, we intend to investigate the structure of the undoped NaPO3-WO3 samples as a function of composition through solid state NMR of the component nuclei 23Na and 31P (183W has very low sensitivity, but if possible will also be measured). Once selection can be made of the most favorable composition to host the metallic nanoparticle and rare-earth ions, different sets of samples with varying concentration of NPs and RE will be prepared, so as to allow systematic photophysical studies. The phenomenon of luminescence enhancement by SPR will be investigated for samples doped with different ions (Eu3+, Er3+, Nd3+).
News published in Agência FAPESP Newsletter about the scholarship: