Enhanced frequency upconversion in Ho3+/Yb3+/Li+:YMoO4 nanophosphors for photonic and security ink applications
Enhanced frequency upconversion in Ho3+/Yb3+/Li+:YMoO4 nanophosphors for photonic and security ink applications
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DOI：
10.1063/1.4971966
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发表时间：
2016-12-21
影响因子：
3.2
通讯作者：
Akash, R.
中科院分区：
文献类型：
--
作者：
Mondal, Manisha;Rai, Vineet Kumar;Akash, R.
采用化学共沉淀法合成了Ho3+/Yb3+/Li+共掺杂的YMoO4纳米荧光粉，并用X射线衍射仪、场发射扫描电子显微镜和透射电子显微镜对其结构进行了表征。透射电子显微镜的亮场成像表明，所制备的纳米荧光粉为结晶型，颗粒尺寸约为45 nm。在较低的泵浦功率(=900 mW)下，观察到了纳米荧光粉在980 nm处的上转换(UC)发射光谱，在400-900 nm范围内有一个强的宽带，并有一个紫外带。与Ho3+单掺纳米荧光粉相比，Ho3+-Yb3+-Li+共掺纳米荧光粉的绿带强度提高了约104倍。这种增强是由于Yb3+离子向Ho3+离子的能量转移，改变了稀土离子周围形成的局域晶场。在Ho3+-Yb3+-Li+共掺纳米荧光粉中，在944 mW-1200 mW泵浦功率范围内有一个较高的斜率(n类似于6.38)，这是由于参与了光子雪崩布居过程，而与黑体辐射无关。宽带发射的564 nm和648 nm的强发射峰是由共掺纳米荧光粉的电荷转移发光引起的，这与MoO4基团中的氧离子和Yb3+离子有关。本文所描述的观察结果可能对开发可见上变频器、安全墨水以及用于低泵功率和高泵浦功率区域的新型显示器件具有重要意义。由AIP出版公司出版。
The YMoO4 nanophosphors codoped with Ho3+/Yb3+/Li+ ions synthesized by the chemical coprecipitation method have been structurally characterized by using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM) techniques. The TEM bright field imaging shows that the developed nanophosphors are crystalline in nature with particle size similar to 45 nm. The upconversion (UC) emission spectra upon excitation at 980 nm of the nanophosphors at low pump power (= 900 mW) an intense broad band ranging from 400-900 nm along with a UV band has been observed. The enhancement of about similar to 104 times corresponding to the green band in the Ho3+-Yb3+-Li+ codoped nanophosphors compared to that of the Ho3+ singly doped nanophosphors has been observed. This enhancement is caused by the energy transfer from the Yb3+ to Ho3+ ions and modified the local crystal field developed around the rare earth ions. A higher value of the slope (i.e., n similar to 6.38) for broad band emission within the 944 mW-1200 mW pump power region in the Ho3+-Yb3+-Li+ codoped nanophosphors is found to be due to the involvement of the photon avalanche population process but it is not related to the black body radiation. The intense peak at similar to 564 nm and similar to 648 nm for the broad band emission is attributed to the charge transfer luminescence of codoped nanophosphors, which is related to the oxygen ion present in the MoO4 group and Yb3+ ion. The observations described in this paper may be of significant interest for developing the visible upconverters, security ink, and novel devices for displays in the low and high pump power region. Published by AIP Publishing.