Triple excitation with dual emission in paramagnetic ZnO:Er3+ nanocrystals

Abstract

ZnO nanocrystals have been made excitable under UV as well as near and far infrared (IR) wavelengths (980 nm, 1550 nm) through doping of rare earth ion Er³⁺ thus making it a triple excitation nanophosphor. Whereas the visible emission under UV is broad due to intrinsic donor acceptor pair recombination, the sharp green and red emission peaks under IR are characteristic of f–f transitions of the Er³⁺ ion. Thus both down and upconversion fluorescence in ZnO could be realised through doping of rare earth ion Er³⁺ that also makes ZnO:Er³⁺ nanocrystals paramagnetic. To the best of our knowledge we are reporting upconversion at 1550 nm in ZnO:Er³⁺ for the first time.