Wide band gap (3.37 eV) and high exciton binding energy (60 meV) make ZnO a promising candidate for ultraviolet (UV) light-emitting diodes (LEDs) and low-threshold lasing diodes (LDs).Meanwhile,NaYF4 upconversion (UC) nanoparticles doped with rare-earth ions have shown great potential as optical imaging probes for biomedical applications because of their unique merits such as high-efficiency luminescence,good photostability and multicolored emissions with low cost near-infrared excitation.Herein,we will present our recent studies on ZnO-based UV LEDs and rare-earth doped NaYF4 UC nanoparticles.