基于贵金属表面局域等离子体共振(LSPR)调控上转换荧光的研究绝大部分集中于纳米颗粒或纳米棒, 即使同一复合结构对上转换荧光(UCL)也有或增强或猝灭的截然相反的报道, 而对于进一步提高上转换荧光材料的效率和强度以满足更广泛的应用需求则越来越引起人们高度关注。本文通过构筑两种纳米金/上转换纳米晶复合结构, 系统研究了各自的表面局域等离激元对上转换荧光的增强和猝灭效应, 基于微结构表征及对稳态、瞬态荧光光谱的分析, 阐述了波长依赖的上转换荧光增强和猝灭机理。结果显示超薄纳米金壳结构对Ho3+、Fe3+共掺杂纳米晶的绿光发射选择性地增强了25倍, 源于激发光能量与LSPR能量匹配的激发增强机制, 而在覆盖有超薄纳米金膜的上转换纳米晶复合结构中却观察到了金膜引起的Er上转换荧光猝灭, 同时红绿比随金膜厚度增加而增大, 来自于金膜对激发光的散射、金膜的LSPR吸收带与绿光发射能级耦合引起无辐射跃迁几率增加, 绿光上转换荧光强度下降相对显著, UCL寿命变短。

Two types of plasmonic nanostructure i.e. the ultra-thin gold nanoshell and the sputtered gold nanofilm combined with upconverting nanocrystals are designed and fabricated. The enhancing effect of gold nanoshells on the upconversion luminescence (UCL) and the quenched UCL induced by the gold nanofilm are observed, respectively. The wavelength dependent enhancement and quenching mechanisms are elucidated on the basis of the microstructure characterizations, steady state and transient spectral analysis. Green emission of Ho ions has been selectively enhanced by the ultra-thin gold nanoshell outside of NaYF4∶Yb, Ho,Fe nanocrystals, and the excitation enhancement mechanism is stemmed from the coupling of LSPR with NIR excitation energy. In contrast, sputtered gold film on the top of the NaYF4∶Yb,Er@SiO2 nanocrystal exhibits the quenching effect, likely originating from the scattering of the excitation light and the increase of nonradiative transition probability of the green emission state due to its coupling with LSPR absorption band, which is responsible for the decline of UCL intensity as well as the shortened green UCL lifetime.