K离子掺杂增强NaErF4体系上转换发光

制备了一系列Na_1-xK_xErF₄@NaLuF₄的核壳纳米结构，核中K⁺掺杂摩尔分数变化范围为0%~8%。XRD分析结果揭示这些具有不同K掺杂浓度的纳米粒子均为β-相纳米结构。研究结果表明：随着K⁺浓度的增加，纳米结构中Er³⁺~650 nm处的红带发光强度呈现先增强后减弱的规律，当K⁺摩尔分数为4%时，Na_0.96K_0.04ErF₄@NaLuF₄纳米晶的发光强度达到最大，为未掺杂K⁺的NaErF₄@NaLuF₄纳米晶发光强度的3.7倍。其发光增强的原因在于K⁺的掺杂降低了Er³⁺微环境晶场宇称对称性，提高了Er³⁺离子⁴F_9/2→⁴I_5/2能级辐射跃迁几率，进而增强了Er³⁺的650 nm红带的上转换发光强度。

Enhancement of NaErF4 Nanostructure Upconversion Luminescence with K+ Doping

The nanostructures composing of Na_1-xK_xErF₄@NaLuF₄ core@shell were synthetized with 0%-8% K⁺ doping mole fraction in the cores. XRD results reveal that all of the nanoparticles are the hexagonal structure. The research results show that the intensity of UCL at~650 nm increases at first and then decreases with K⁺ concentration under 980 nm excitation. The intensity is enhanced 3.7 times with 4% K⁺ doping, compared with that of NaErF₄@NaLuF₄ core@shell without K⁺ doping. Furthermore, the slopes of relationship between UCL intensity and pumping power are from 1.91 to 1.76, for the two nanostructures undoped and doped with 4% K⁺, respectively. Our results suggest that the strategy of K⁺ doping in NaErF₄@NaLuF₄ nanoparticles is an efficient solution to improve the luminescence efficiency of NaErF₄@NaLuF₄ nanosystem.