Upconversion luminescence properties of Y₂O₃:Yb ³⁺, Er³⁺ nanostructures

Cubic Y₂O₃ nanostructures doped with Yb³⁺ and Er³⁺ ions were synthesized by a facile hydrothermal method. Three distinct shapes such as nanotubes, nanospheres and nanoflakes formed in the products by adjusting the pH value of reacting solution. Powder X-ray diffraction analyses indicate that all the three nanostructures are pure cubic phase, while electron microscopy measurements confirm the formation of different morphologies. These nanostructures exhibit strong visible upconversion luminescence under the excitation of a 978-nm diode laser. In Yb³⁺- and Er³⁺- codoped Y₂O₃ nanocrystals, the relative intensity of green emission became stronger as the size and morphology of sample changed from tubes to flakes.