Multiband emission from single β-NaYF4(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies
Multiband emission from single β-NaYF4(Yb,Er) nanoparticles at high excitation power densities and comparison to ensemble studies
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DOI：
10.1007/s12274-021-3350-y
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发表时间：
2021-02-24
期刊：
影响因子：
9.9
通讯作者：
Resch-Genger, Ute
中科院分区：
文献类型：
--
作者：
Frenzel, Florian;Wuerth, Christian;Resch-Genger, Ute
在6个数量级的激发功率密度（P）范围内对掺杂有20%Yb 3+和1%或3%Er 3+的核和核-壳β-NaYF4：Yb，Er上转换纳米颗粒（UCNP）的激发功率密度（P）依赖的上转换发光（UCL）进行的包封和单粒子研究揭示了在P> 1 kW/cm（2）时来自高能Er 3+能级的发射的贡献增加。这会将整体发射颜色从最初的黄色上的绿色更改为白色。虽然最初的绿色和增加的P红色发光占主导地位的系综测量在P <1千瓦/厘米（2），人口的增加更高的Er 3+能级的多光子过程在更高的P在单粒子研究中的结果在紫外/可见光/近红外（UV/可见光/NIR）的大量发射带伴随着减少的贡献的红色发光。基于对UCL的P依赖性的全面分析，将在高P下激活的发射带分组并分配给2 - 3、3 - 4和4个光子过程，包括能量转移（ET）、激发态吸收（ESA）、交叉弛豫（CR）、反向能量转移（BET）和非辐射弛豫过程（nRP）。这强调了UCNP亮度和颜色的P-可调谐性，并突出了P-依赖性测量的潜力，用于显示不同Er 3+水平的群体途径所需的机制研究。
Ensemble and single particle studies of the excitation power density (P)-dependent upconversion luminescence (UCL) of core and core-shell beta-NaYF4:Yb,Er upconversion nanoparticles (UCNPs) doped with 20% Yb3+ and 1% or 3% Er3+ performed over a P regime of 6 orders of magnitude reveal an increasing contribution of the emission from high energy Er3+ levels at P > 1 kW/cm(2). This changes the overall emission color from initially green over yellow to white. While initially the green and with increasing P the red emission dominate in ensemble measurements at P < 1 kW/cm(2), the increasing population of higher Er3+ energy levels by multiphotonic processes at higher P in single particle studies results in a multitude of emission bands in the ultraviolet/visible/near infrared (UV/vis/NIR) accompanied by a decreased contribution of the red luminescence. Based upon a thorough analysis of the P-dependence of UCL, the emission bands activated at high P were grouped and assigned to 2-3, 3-4, and 4 photonic processes involving energy transfer (ET), excited-state absorption (ESA), cross-relaxation (CR), back energy transfer (BET), and non-radiative relaxation processes (nRP). This underlines the P-tunability of UCNP brightness and color and highlights the potential of P-dependent measurements for mechanistic studies required to manifest the population pathways of the different Er3+ levels.