Bright white upconversion emission from Yb3+, Er3+, and Tm3+-codoped Gd2O3 nanotubes

Yb3+, Er3+, and Tm3+-codoped Gd2O3 nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 degrees C. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), upconversion (UC) emission spectra, and kinetic decay were used to characterize the samples. Bright white UC luminescence in the nanotubes was observed under diode laser excitation of 980 nm. The white light consists of the blue ((1)G(4) --> H-3(6) of Tm3+), green (H-2(11/2)/S-4(3/2) --> I-4(15/2) of Er3+), and red (F-4(9/2) --> I-4(15/2) of Er3+) UC emissions. As the excitation power density changed in the range of 20-200 W cm(-2), the calculated CIE color coordinates shift only slightly and fall well within the white region. This material may be a potential candidate for applications of color displays, lighting and photonics.