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2. First-principles study on luminescence properties of Eu-doped defect pyrochlore oxide KNbWO$_6\cdot$H$_2$O:Eu$^{3+}$

Author

Choe, Song-Hyok, Yu, Chol-Jun, Choe, Myong, Kye, Yun-Hyok, Han, Yong-Nam, and Pang, Guangsheng

Subjects
Condensed Matter - Materials Science
Abstract

Defect pyrochlore oxides have attracted a great interest as promising luminescent materials due to their flexible composition and high electron/hole mobility. In this work, we investigate the structural and electronic properties of lanthanide-doped (Ln) defect pyrochlore oxides \ce{KNbWO6}:0.125Ln$^{3+}$ by using first-principles calculations. We perform structural optimizations of various defect pyrochlore models and calculate their electronic structures, revealing that hydration has a significant influence on both local symmetry around Eu$^{3+}$ ion and band structures with an alteration of their luminescent behaviour. In the hydrated compounds, the electric-dipole $^5$D$_0-^7$F$_2$ transition is found to be partially suppressed by the raised local symmetry, and the water molecules in the compounds can mediate the non-radiative energy transfer between the activator Eu$^{3+}$ ions and the host, resulting in the quenching effect. It turns out that the oxygen vacancies are detrimental to luminescence as they reduce the Eu$^{3+}$ ion in its vicinity to Eu$^{2+}$ ion and also serve as traps for conduction electrons excited by incident light. Our calculations for \ce{KNbWO6}:0.125Ln$^{3+}$ (Ln = Ce, Pr, Nd, Pm, Sm) support that defect pyrochlore oxide \ce{KNbWO6} can also be used as luminescence host for Ln$^{3+}$ ion doping, giving a valuable insight into a variation trend in luminescent properties of these materials at atomic level.

Published
2019
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38. Functional Aerogels Composed of Regenerated Cellulose and Tungsten Oxide for UV Detection and Seawater Desalination.

Author

Tang, Yanjin, Lai, Yuhan, Gao, Ruiqin, Chen, Yuxuan, Xiong, Kexin, Ye, Juan, Zheng, Qi, Fang, Zhenxing, Pang, Guangsheng, and Lee, Hoo-Jeong

Subjects
AEROGELS, CELLULOSE, TUNGSTEN oxides, SALINE water conversion, PHOTOCHROMISM
Abstract

Functional aerogels composed of regenerated cellulose and tungsten oxide were fabricated by implanting tungsten-oxide nanodots into regenerated cellulose fiber. This superfast photochromic property benefitted from the small size and even distribution of tungsten oxide, which was caused by the confinement effect of the regenerated cellulose fiber. The composite was characterized using XRD and TEM to illustrate the successful loading of tungsten oxide. The composite turned from pale white to bright blue under ambient solar irradiation in five seconds. The evidence of solar absorption and electron paramagnetic resonance (EPR) demonstrated the fast photochromic nature of the composite and its mechanism. Furthermore, carbon fiber filled with preferential growth tungsten-oxide nanorods was obtained by annealing the photochromic composite in a N2 atmosphere. This annealed product exhibited good absorption across the whole solar spectrum and revealed an excellent photothermal conversion performance. The water evaporation rate reached 1.75 kg m−2 h−1 under one sun illumination, which is 4.4 times higher than that of pure water. The photothermal conversion efficiency was 85%, which shows its potential application prospects in seawater desalination. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Preparation and characterization of monodispersed YSZ nanocrystals

Author

Pang, Guangsheng, Chen, Siguang, Zhu, Yingchun, Palchik, Oleg, Koltypin, Yuri, Zaban, Afie, and Gedanken, Aharon

Subjects
Crystallization -- Research, Surface chemistry -- Research, Zirconium oxide -- Optical properties, Chemicals, plastics and rubber industries
Abstract

A new method is applied for preparation of yttria-stablilized zirconia(YSZ) nanocrystals. While crystallization occurs on the surface and interface of SrCO(sub 3) nanoparticles, the agglomeration of YSZ particles is inhibited.

Published
2001

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