Effect of OH on the upconversion luminescent efficiency of Y2O3:Yb, Er nanostructures

In this work, we used the hydrothermal method to synthesize Yb³⁺ and Er³⁺ ions doped cubic Y₂O₃ nanostructures, which is an upconversion luminescent material. 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 were 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. The FTIR and fluorescent decay measurements at the size and morphology of sample changed from tubes to flakes indicate that the OH⁻ group is the origin of luminescent efficiency change. OH⁻ ions with high vibration frequency provide an efficient means to quench the luminescence. However, the relative intensity and pump-power dependence of the green and red emissions varies with the three nanostructures possessing different size and morphology.