A strategy to enhance Eu 3+ emission from LiYF 4:Eu nanophosphors and green-to-orange multicolor tunable, transparent nanophosphor-polymer composites

Abstract

LiYF 4:Eu nanophosphors with a single tetragonal phase are synthesized, and various strategies to enhance the Eu 3+ emission from the nanophosphors are investigated. The optimized Eu 3+ concentration is 35â €...mol%, and the red emission peaks due to the 5 D 0 â †' 7 F J (J = 1 and 2) transitions of Eu 3+ ions are further enhanced by energy transfer from a sensitizer pair of Ce 3+ and Tb 3+. The triple doping of Ce, Tb, and Eu into the LiYF 4 host more effectively enhances the Eu 3+ emission than the core/shell strategies of LiYF 4:Eu(35%)/LiYF 4:Ce(15%), Tb(15%) and LiYF 4:Ce(15%), Tb(15%)/LiYF 4:Eu(35%) architectures. Efficient energy transfer from Ce 3+ to Eu 3+ through Tb 3+ results in three times higher Eu 3+ emission intensity from LiYF 4:Ce(15%), Tb(15%), Eu(1%) nanophosphors compared with LiYF 4:Eu(35%), which contains the optimized Eu 3+ concentration. Owing to the energy transfer of Ce 3+ †' Tb 3+ and Ce 3+ †' Tb 3+ â †' Eu 3+, intense green and red emission peaks are observed from LiYF 4:Ce(13%), Tb(14%), Eu(1-5%) (LiYF 4:Ce, Tb, Eu) nanophosphors, and the intensity ratio of green to red emission is controlled by adjusting the Eu 3+ concentration. With increasing Eu 3+ concentration, the LiYF 4:Ce, Tb, Eu nanophosphors exhibit multicolor emission from green to orange. In addition, the successful incorporation of LiYF 4:Ce, Tb, Eu nanophosphors into polydimethylsiloxane (PDMS) facilitates the preparation of highly transparent nanophosphor-PDMS composites that present excellent multicolor tunability.