Kamińska Izabela, Jankowski Dawid, Sikora Bożena, Kowalik Przemysław, Minikayev Roman, Wojciechowski Tomasz, Chojnacki Michał, Sobczak Kamil, Rybusiński Jarosław, Szczytko Jacek, Zajdel Karolina, Suchocki Andrzej, Paszkowicz Wojciech, Frontczak-Baniewicz Małgorzata, Fronc Krzysztof
Institute of Physics Polish Academy of Sciences, al. Lotników 32/46, Warsaw 02-668, Poland.
Research Foundation Baltic Institute of Technology, al. Zwycięstwa 96/98, 81-451 Gdynia, Poland.
Nanotechnology. 2020 May 29;31(22):225711. doi: 10.1088/1361-6528/ab73b9. Epub 2020 Feb 7.
The paramagnetic Y ErYb AlO (x = 0.02, 0.06, 0.10, 0.12, 0.18, 0.20) nanocrystals (NCs) were synthesized by the microwave-induced solution combustion method. The XRD, TEM and SEM techniques were applied to determine the NCs' structures and sizes. The XRD patterns confirmed that the NCs have for the most part a regular structure of the YAlO (YAG) phase. The changes of the distance between donor Yb (sensitizer) and acceptor Er (activator) were realized by changing the donor's concentration with a constant amount of acceptor. Under 980 nm excitation, at room temperature, the NCs exhibited strong red emission near 660 and 675 nm, and green upconversion emission at 550 nm, corresponding to the intra 4f transitions of Er (F H, S) → Er (I). The strongest emission was observed in a sample containing 18% Yb ions. The red and green emission intensities are respectively about 5 and 12 times higher as compared to NCs doped with 2% of Yb. In order to prove that the main factor responsible for the increase of the upconversion luminescence efficiency is reduction of the distance between Yb and Er, we examined, for the first time the influence of hydrostatic pressure on luminescence and luminescence decay time of the radiative transitions inside donor ion. The decrease of both luminescence intensity and luminescence decay times, with increasing hydrostatic pressure was observed. After applying hydrostatic pressure to samples with e.g. 2% and 6% Yb, the distance between the donor and acceptor decreases. However, for higher concentrations of the donor, this distance is smaller, and this leads to the effective energy transfer to Er ions. With increasing pressure, the maximum intensity of near infrared emission is observed at 1029, 1038 and 1047 nm, what corresponds to F → F transition of Yb.
通过微波诱导溶液燃烧法合成了顺磁性Y ErYb AlO（x = 0.02、0.06、0.10、0.12、0.18、0.20）纳米晶体（NCs）。应用X射线衍射（XRD）、透射电子显微镜（TEM）和扫描电子显微镜（SEM）技术来确定NCs的结构和尺寸。XRD图谱证实，NCs在很大程度上具有YAlO（YAG）相的规则结构。通过在受体量恒定的情况下改变供体的浓度，实现了供体Yb（敏化剂）和受体Er（激活剂）之间距离的变化。在980 nm激发下，室温下，NCs在660和675 nm附近表现出强烈的红色发射，在550 nm处表现出绿色上转换发射，对应于Er（F H，S）→Er（I）的4f内跃迁。在含有18% Yb离子的样品中观察到最强发射。与掺杂2% Yb的NCs相比，红色和绿色发射强度分别高出约5倍和12倍。为了证明上转换发光效率提高的主要因素是Yb和Er之间距离的减小，我们首次研究了静水压力对供体离子内部辐射跃迁的发光和发光衰减时间的影响。观察到随着静水压力的增加，发光强度和发光衰减时间均降低。对例如含有2%和6% Yb的样品施加静水压力后，供体和受体之间的距离减小。然而，对于更高浓度的供体，该距离更小，这导致了向Er离子的有效能量转移。随着压力增加，在1029、1038和1047 nm处观察到近红外发射的最大强度，这对应于Yb的F→F跃迁。
