In situ formation of rare-earth-doped nanoparticles in a silica matrix from Molecular Dynamics simulations

Abstract

Developing new rare-earth-doped optical glasses with "enhanced" spectroscopic properties requires the elaboration of new glass compositions. To overcome some typical limitations of silica glass, a strategy consists in encapsulating rare-earth (RE) ions within oxide nanoparticles (NPs) through a phase separation mechanism. In this paper, Molecular Dynamics simulations were performed using an interatomic potential reproducing the phase separation within a MgO-SiO2 binary melt to obtain RE-codoped glass models with RE = Eu or Er. In these structures, we observed that Mg-rich regions, included into a silica-rich matrix and identified as NPs, are amorphous and exhibit a large range of sizes. We showed that such nanoparticles are the host of a depolymerization phenomenon of the NPs' SiO4 tetrahedral network leading to a release of nonbridging oxygen atoms. In the NPs, the MgO concentration increases and the doping RE ions are mainly located into the NPs where they are over-concentrated compared with the nominal doping concentration.However, the induced clustering effect is limited because of the non-bridging-oxygen-rich environment encountered in the NPs. This numerical analysis allows to give an insight on the chemical composition of the NPs, and especially on the local environment of the encapsulated rare-earth ions.

Phase-separated Ca and Mg-based nanoparticles in SiO$$_{2}$$ glass investigated by molecular dynamics simulations

“…Consequently, Molecular Dynamics (MD) simulations turn out to be a helpful alternative to obtain information on the structural properties at the nanoscale. In a previous work, from MD simulations of rare-earth doped NPs formed in a Mg-silicate matrix 9 we have shown an over-concentration of the rare-earth ions within the NPs and a reduction of the clustering effect in comparison with a simple rare-earth doped silica glass. A size-dependent composition of these NPs was also observed, in agreement with the experimental measurements of Blanc et al 10 .…”

“… (eV) (Å ) (Å) (eV Å ) Si –O 0.340554 2.006700 2.100000 1.0 Ca –O 0.033747 1.646077 3.303187 0.0 Mg –O 0.209290 1.376871 2.733041 0.0 O –O 0.042395 1.379316 3.618701 22.0 Ca–O interaction parameters are represented in bold text. Mg potential parameters (italic text) are also reported from previous study 9 , 17 . The non-coulombic interactions were zero for all cation-cation interactions.…”

“…Therefore, it appears interesting to study the influence of the metal oxide on the structural properties of the NPs. In this context, MD simulations were performed using the modified version of the Pedone potential refined by Bidault et al 9 to reproduce a phase separation mechanism. By this way, Ca-based nanoparticles were formed in situ in a silica matrix glass of 0.10CaO–0.90SiO chemical composition and elaborated through the classical melt/quench procedure.…”

“…Afterwards, the structural and compositional properties of these NPs, as well as the local environment encountered by Ca cation were analyzed in detail. Finally, the NPs’ structural properties and the Ca behavior in the host matrix were compared with those encountered in Mg-based nanoparticles within a previously modeled 0.10MgO–0.90 SiO glass structure 9 .…”

Refractive Index and Temperature Sensing Performance of Microfiber Modified by UV Glue Distributed Nanoparticles

“…also exhibit excellent sensing performance [13,14]. Various NPs have been doped into silica or polymer optical fibers for determination of bio-molecular or chemical composition [15][16][17], where internal doping and surface coating have become the most typical modification methods. Compared with crystal or dielectric materials, the scattering loss of metal particles is extremely serious.…”