Blue, green, and red emission from undoped and doped ZnGa2O4 colloidal nanocrystals

Undoped, Tb3+- and Eu3+-doped ZnGa2O4 colloidal nanocrystals were synthesized by a nonhydrolytic hot solution chemistry. Undoped nanocrystals exhibited an intrinsic blue emission peaking at 437 nm by self-activated transition. The emissions of Tb3+- and Eu3+-doped ZnGa2O4 nanocrystals consisted of their own characteristic green and red line peaks (D-5(4)-F-7(j) transitions), respectively. Synthetic parameters such as activator concentration and reaction time were varied to investigate their effects on luminescent properties. Tb3+-doped colloidal nanocrystals synthesized for a short reaction time showed an unprecedented, exclusively green luminescence with the host blue emission effectively suppressed. On the other hand, the emission of Eu3+-doped ones was weak with the host emission persistently present regardless of reaction time.