Fluorescence upconversion in Sm-doped Gd 2 O 3

We report the observation of efficient fluorescence upconversion in Sm-doped Gd 2 O 3 nanopowders prepared by the spray pyrolysis method. The blue upconversion emission was observed with low-power continuous-wave excitation at 514, 561, 594, and 633 nm and with a pulsed femtosecond at 710 nm , in a laser scanning confocal microscope. This result indicates that Sm-doped Gd 2 O 3 has the potential as a fluorescent label that may be excited in red, yellow, and green with blue emission.