Novel phase transition method of upconversion nanocrystals with enhanced luminesecnce intensity

Lanthanide-doped upconversion nanocrystal (UCN) show anti-Stokes effect that absorbs near-infrared (NIR) light and emit visible luminescence. Nowadays, UCN have been used in bio-imaging, drug delivery and photovoltaics because it offers high photo-stability, low toxicity and absence of autofluorescence. In order to become practical application, controlling luminescence color of UCN is required. However, most of modulating method of UCN luminescence color rely on synthetic process. Herein, we suggest novel method for manipulating optical and chemical properties of UCN. It induces color and crystal phase transition with dramatically enhanced luminescence intensity