Han Yingdong, Li Hongyu, Wang Yangbo, Pan Yue, Huang Ling, Song Feng, Huang Wei
School of Physics & The Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, Nankai University, Tianjin, 300071, China.
Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P.R. China.
Sci Rep. 2017 May 2;7(1):1320. doi: 10.1038/s41598-017-01611-9.
Lanthanide-doped upconversion nanomaterials are emerging as promising candidates in optoelectronics, volumetric display, anti-counterfeiting as well as biological imaging and therapy. Typical modulations of upconversion through chemical methods, such as controlling phase, composition, morphology and size enable us to rationally manipulate emission profiles and lifetimes of lanthanide ions by using continuous-wave laser excitation. Here we demonstrate that under pulsed laser excitation the emission color of NaYF:Er/Tm (2/0.5%)@NaYF core-shell nanoparticles has an obvious transformation from green to red colors. Moreover, both pulse duration and repetition frequency are responsible for manipulating the upconversion emission color. The mechanism of the phenomena may be that the pulsed laser sequence triggers the emission levels to non-steady upconversion states first, and then cuts off the unfinished population process within the pulse duration. This pump source dependent and resultant tunable fluorescence emission enables NaYF:Er/Tm (2/0.5%)@NaYF nanoparticles as a promising fluorophore in the transparent anti-fake printing.
镧系元素掺杂的上转换纳米材料正在成为光电子学、立体显示、防伪以及生物成像与治疗等领域中很有前景的候选材料。通过化学方法对上转换进行典型调制，例如控制相、组成、形态和尺寸，使我们能够通过连续波激光激发合理地操纵镧系离子的发射光谱和寿命。在此我们证明，在脉冲激光激发下，NaYF:Er/Tm（2/0.5%）@NaYF核壳纳米颗粒的发射颜色有从绿色到红色的明显转变。此外，脉冲持续时间和重复频率都对操纵上转换发射颜色起作用。该现象的机制可能是脉冲激光序列首先将发射能级触发到非稳态上转换状态，然后在脉冲持续时间内切断未完成的布居过程。这种依赖泵浦源且由此产生的可调谐荧光发射使NaYF:Er/Tm（2/0.5%）@NaYF纳米颗粒成为透明防伪印刷中一种很有前景的荧光团。
