Microwave-assisted synthesis of erbium-doped yttrium oxide nanoparticles and their upconversion properties

A time- and energy-saving microwave (MW)-assisted method was adopted to synthesise yttrium oxide (Y₂O₃):erbium (Er) nanoparticles with upconversion (UC) luminescence properties within a few minutes, followed by a post-calcination treatment. It was demonstrated that calcination of nanoparticles at 800°C fully removed the organic groups from them and consequently produced crystalline Y₂O₃ nanoparticles, which was evident from X-ray diffraction (XRD) and Fourier transform infrared analysis. The energy-dispersive X-ray spectroscopy and XRD analysis confirmed that the Er element was successfully doped in Y₂O₃ nanoparticles. The growth process was monitored by time-dependent experiments, during which ultra-small particles would form first and then gradually dissolved and re-growed on surfaces of big particles. A two-photon process was demonstrated in the fabricated Y₂O₃:Er nanoparticles. As a cost-effective and highly-efficient method, the MW method can facilitate mass production and further application of UC nanomaterials into a variety of fields including solar cells, flat panel displays, sensors and UC lasers.