Luo Qi, Chen Yanrui, Li Zhiqiang, Zhu Feng, Chen Xiaohong, Sun Zhuo, Wei Yunle, Guo Hai, Wang Zeng Bo, Huang Sumei
Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, North Zhongshan Rd. 3663, Shanghai 200062, People's Republic of China.
Nanotechnology. 2014 May 9;25(18):185401. doi: 10.1088/0957-4484/25/18/185401. Epub 2014 Apr 15.
Four-layered plasmonic structures of glass/Au/TiO2/NaYF4:Yb, Er, Gd nanorods were fabricated and tremendous improvement in upconversion luminescence (UCL) was observed under infrared 980 nm excitation. The TiO2 film was used as an oxide spacer. The emission intensity of the upconversion (UC) nanorods was strongly modulated by the thickness of the TiO2 layer. The extent of modulation depended on the separation distance between the Au layer and UC nanorods. A maximum UCL enhancement of 192-fold was observed for one green emission (540 nm) when a 10 nm-thick TiO2 film was used; 150-fold was observed for the other green emission (521 nm) at the same thickness of TiO2; and 105-fold was observed for the red emission (654 nm) when a 7.5 nm-thick TiO2 film was used. Alteration of the radiative decay rate was demonstrated for the first time in measurements of the decay times of UC nanorods positioned at various distances from the Au layer. The light interaction and coupling between metal Au and UC nanorods is numerically studied. The UCL mechanisms of multilayer plasmonic structures are discussed. Experimental results are explained and correspond well with those of theoretical calculations.
制备了玻璃/Au/TiO₂/NaYF₄:Yb,Er,Gd纳米棒的四层等离子体结构，并观察到在980 nm红外激发下，上转换发光（UCL）有显著改善。TiO₂薄膜用作氧化物间隔层。上转换（UC）纳米棒的发射强度受到TiO₂层厚度的强烈调制。调制程度取决于Au层与UC纳米棒之间的间距。当使用10 nm厚的TiO₂薄膜时，一种绿色发射（540 nm）的UCL增强最大值为192倍；在相同TiO₂厚度下，另一种绿色发射（521 nm）的增强为150倍；当使用7.5 nm厚的TiO₂薄膜时，红色发射（654 nm）的增强为105倍。在测量位于距Au层不同距离处的UC纳米棒的衰减时间时，首次证明了辐射衰减率的改变。对金属Au与UC纳米棒之间的光相互作用和耦合进行了数值研究。讨论了多层等离子体结构的UCL机制。实验结果得到了解释，并且与理论计算结果吻合良好。
