Lin Hao, Xu Dekang, Li Yongjin, Yao Lu, Xu Liqin, Ma Ying, Yang Shenghong, Zhang Yueli
School of Physics and Electronic Engineering , Guangzhou University , Guangzhou 510006 , P. R. China.
School of Chemistry and Materials Engineering , Huizhou University , Huizhou 516007 , P. R. China.
Inorg Chem. 2018 Dec 17;57(24):15361-15369. doi: 10.1021/acs.inorgchem.8b02654. Epub 2018 Nov 27.
Luminescence efficiency of trivalent lanthanide-doped upconversion (UC) materials is significantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er-sensitized NaLuF UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by confining the excitation energy in the Er activator after introducing the Tm or Ho energy trapping center. The enhanced red UC emission (Er: 660 nm) mainly comes from the effective excitation energy confinement by Tm and Ho trapping centers through an easy energy transfer between Er and Tm/Ho: I (Er) → H (Tm) → I (Er) and I (Er) → I (Ho) → I (Er). It is found that the confining efficiency of excitation energy in Er-sensitized NaLuF crystals is higher than that in Yb/Er cosensitized NaLuF crystals, and the luminescence efficiency of Er-sensitized NaLuF crystals is much higher than that of Er-based host sensitization UC crystals (NaErF). Moreover, Er-sensitized UC particles can be efficiently excited by three different wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.
三价镧系元素掺杂的上转换（UC）材料的发光效率受到发光浓度猝灭的显著限制。在这项工作中，通过在多个激发波长下的能量俘获，在铒敏化的NaLuF UC晶体中红色UC发射显著增强。在引入铥或钬能量俘获中心后，通过将激发能量限制在铒激活剂中，交叉弛豫猝灭和向内部晶格缺陷的能量迁移同时受到抑制。增强的红色UC发射（铒：660 nm）主要来自铥和钬俘获中心通过铒与铥/钬之间的容易的能量转移（I(Er)→H(Tm)→I(Er)和I(Er)→I(Ho)→I(Er)）对激发能量的有效限制。发现铒敏化的NaLuF晶体中激发能量的限制效率高于镱/铒共敏化的NaLuF晶体，并且铒敏化的NaLuF晶体的发光效率远高于基于铒的主体敏化UC晶体（NaErF）。此外，铒敏化的UC颗粒可以被三种不同波长（808、980和1532 nm）有效激发，这表明在生物成像、防伪和太阳能电池应用中具有巨大优势。
