Chen Daqin, Xu Min, Ma Mengfan, Huang Ping
College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018, P. R. China.
Dalton Trans. 2017 Nov 14;46(44):15373-15385. doi: 10.1039/c7dt02915b.
In upconversion nanocrystals where Er acts as the activator, concentration quenching will easily occur when the content of Er is high (generally >5mol%), and the Er spatial distribution which is a key factor affecting the concentration quenching is an important issue that must be considered. Herein, we selected Yb:NaErF as a light-emitting layer and investigated its upconversion performance and temperature sensing behaviors in two kinds of core-shell nanoarchitectures. Yb and Er activators were distributed in a three-dimensional sphere and two-dimensional thin layer in Yb:NaErF@Yb/Nd:NaYF@NaGdF and NaGdF@Yb:NaErF@Yb/Nd:NaYF@NaGdF core-shell nanocrystals, respectively. The difference in Er spatial distribution in the core-shell structure resulted in significant modification of red-to-green ratios and decay behaviors upon excitation at 376 nm, 808 nm, 980 nm and 1532 nm, and the related mechanisms were systematically investigated. In addition, the spatial distribution of Er was demonstrated to have no obvious effect on the transitions of Er thermally coupled H → I and S → I and the relative sensitivity for temperature determination under 808 nm laser excitation.
在以铒（Er）作为激活剂的上转换纳米晶体中，当铒的含量较高（通常>5mol%）时，容易发生浓度猝灭，而铒的空间分布作为影响浓度猝灭的关键因素，是一个必须考虑的重要问题。在此，我们选择Yb:NaErF作为发光层，并研究了其在两种核壳纳米结构中的上转换性能和温度传感行为。在Yb:NaErF@Yb/Nd:NaYF@NaGdF和NaGdF@Yb:NaErF@Yb/Nd:NaYF@NaGdF核壳纳米晶体中，Yb和Er激活剂分别分布在三维球体和二维薄层中。核壳结构中Er空间分布的差异导致在376nm、808nm、980nm和1532nm激发下红/绿比和衰减行为发生显著变化，并对相关机制进行了系统研究。此外，在808nm激光激发下，Er的空间分布对Er热耦合H→I和S→I跃迁以及温度测定的相对灵敏度没有明显影响。
