BAM Federal Institute for Materials Research and Testing, Division 1.2 Biophotonics, Richard-Willstätter-Str. 11, 12489 Berlin, Germany.
Methods Appl Fluoresc. 2019 Feb 6;7(2):024001. doi: 10.1088/2050-6120/ab023b.
We present here a systematic analysis of the influence of Tm doping concentrations (x ) on the excitation power (P)-dependent upconversion luminescence and -performance of hexagonal-phase NaYF: 20% Yb, x % Tm upconversion nanoparticles (UCNPs) for x of 0.2, 0.5, 0.8, 1.2, and 2.0, respectively. Our results reveal the influence of these different Tm doping concentrations with respect to optimized upconversion quantum yield (Φ ) values of the various Tm upconversion emission bands, with the highest Φ values of the Tm emission bands above 700 nm resulting for different x values as the Tm emission bands below 700 nm. This underlines the potential of Tm dopant concentration for colour tuning. Special emphasis was dedicated to the spectroscopic parameters that can be linked to the (de)population pathways of the various Tm energy levels, like the P- and x -dependent slope factors and the intensity ratios of selected emission bands. The evaluation of all parameters indicates that not only energy transfer upconversion-, but also cross-relaxation processes between neighbouring Tm ions play a vital role in the (de)population of the excited energy levels of Yb, Tm codoped nanocrystals.
我们在这里呈现了一个关于 Tm 掺杂浓度（x）对六方相 NaYF：20%Yb、x%Tm 上转换纳米粒子（UCNP）的上转换发光和性能的激发功率（P）依赖性的系统分析。结果揭示了不同 Tm 掺杂浓度对上转换量子产率（Φ）值的影响，不同的 x 值导致了 700nm 以上 Tm 上转换发射带的最高Φ值，而 700nm 以下的 Tm 发射带则较低。这强调了 Tm 掺杂浓度在颜色调谐方面的潜力。特别强调了与各种 Tm 能级的（去）种群途径相关的光谱参数，如 P 和 x 依赖性斜率因子以及选定发射带的强度比。所有参数的评估表明，不仅能量传递上转换过程，而且相邻 Tm 离子之间的交叉弛豫过程在 Yb、Tm 共掺杂纳米晶体中激发能级的（去）种群中也起着至关重要的作用。
