Devesa Susana, Rodrigues Joana, Teixeira Sílvia Soreto, Rooney Aidan P, Graça Manuel P F, Cooper David, Monteiro Teresa, Costa Luís C
Centre for Physics University of Coimbra (CFisUC), Physics Department, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal.
i3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal.
Nanomaterials (Basel). 2021 Mar 8;11(3):660. doi: 10.3390/nano11030660.
Tetragonal ErNbO and monoclinic ErNbO micro- and nanoparticles were prepared by the citrate sol-gel method and heat-treated at temperatures between 700 and 1600 °C. ErNbO revealed a spherical-shaped crystallite, whose size increased with heat treatment temperatures. To assess their optical properties at room temperature (RT), a thorough spectroscopic study was conducted. RT photoluminescence (PL) spectroscopy revealed that Er optical activation was achieved in all samples. The photoluminescence spectra show the green/yellow H, S→I and red F→I intraionic transitions as the main visible recombination, with the number of the crystal field splitting Er multiplets reflecting the ion site symmetry in the crystalline phases. PL excitation allows the identification of Er high-energy excited multiplets as the preferential population paths of the emitting levels. Independently of the crystalline structure, the intensity ratio between the green/yellow and red intraionic transitions was found to be strongly sensitive to the excitation energy. After pumping the samples with a resonant excitation into the G excited multiplet, a green/yellow transition stronger than the red one was observed, whereas the reverse occurred for higher excitation photon energies. Thus, a controllable selective excited tunable green to red color was achieved, which endows new opportunities for photonic and optoelectronic applications.
通过柠檬酸盐溶胶 - 凝胶法制备了四方相ErNbO和单斜相ErNbO的微米和纳米颗粒，并在700至1600°C的温度下进行热处理。ErNbO呈现出球形微晶，其尺寸随热处理温度的升高而增大。为了评估它们在室温（RT）下的光学性质，进行了全面的光谱研究。室温光致发光（PL）光谱表明，所有样品中均实现了Er的光学激活。光致发光光谱显示，绿色/黄色的H、S→I和红色的F→I离子内跃迁是主要的可见复合过程，晶体场分裂的Er多重峰数量反映了晶相中的离子位点对称性。PL激发能够识别出Er的高能激发多重峰，作为发射能级的优先填充路径。与晶体结构无关，发现绿色/黄色和红色离子内跃迁之间的强度比强烈依赖于激发能量。在用共振激发将样品泵浦到G激发多重峰后，观察到绿色/黄色跃迁比红色跃迁更强，而对于更高的激发光子能量则出现相反的情况。因此，实现了可控的选择性激发可调谐绿色到红色发光，这为光子和光电子应用带来了新的机遇。
