Upconversion luminescence properties of Gd2O3: Er3+ Nanospheres and Gd2O3: Er3+@Silica nanocomposites

Abstract

The upconversion luminescence (UCL) of Gd2O3: Er3+ monodisperse nanospheres, synthesized by multistep chemical method, and nanoparticles, produced by combustion synthesis, are presented for comparison. The UCL of nanospheres Gd2O3: Er3+ and Gd2O3: Er3+@Silica have shown strong red or green emission under excitation at 976 nm or 980 nm by a diode laser with a remarkable increase of the bright red color in the nanospheres. In the core/shell structured nanospheres Gd2O3: Er3+@Silica, we find a higher intensity of upcoversion emission, increased stability and better dispersion capability in solvents and water. The UCL intensities of green and red color while 976 nm or 980 nm excitation were dependent on the diode laser power. The slope values of Er3+ ion’s transitions 2H11/24I15/2, 4S3/24I15/2 and 4F9/24I15/2 in the silica-coated nanospheres are 1.99, 1.62 and 1.66 respectively, which properly indicate the two-photon mechanism of upconversion emission. The synthesized Gd2O3 nanospheres codoped with Yb and Er show strong UCL intensity than those of Gd2O3: Er3+. The obtained Gd2O3: Er3+ nanospheres and nanoparticles, as well as Gd2O3: Yb3+, Er3+ and its silica-coated versions, are promising materials to develop with potential application in high technology and biomedicine. [doi:10.2320/matertrans.MT-MN2019021]