Tens of micron-sized unilamellar nanosheets of Y/Eu layered rare-earth hydroxide: efficient exfoliation via fast anion exchange and their self-assembly into oriented oxide film with enhanced photoluminescence

• Main Authors: Qi Zhu, Ji-Guang Li, Xiaodong Li, et al.
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2014-01-01
• Series: Science and Technology of Advanced Materials
• Online Access: http://dx.doi.org/10.1088/1468-6996/15/1/014203
• ISSN: 1468-6996; 1878-5514

Layered rare-earth hydroxide (LRH) crystals of (Y0.95Eu0.05)2(OH)5NO3centerdotnH2O with a lateral size of ~ 300 μm and a thickness of ~ 9 μm have been synthesized via a hydrothermal reaction of mixed nitrate solutions in the presence of mineralizer NH4NO3 at 200 °C for 24 h. LRH exhibits the ability to undergo intercalation and anion exchange with DS− (C12H25OSO3−) via hydrothermal treatment. Compared with traditional anion exchange at room temperature, hydrothermal processing not only shortens the anion exchange time from 720 to 24 h but also increases the basal spacing. The arrangements of DS− in the interlayer of LRH are significantly affected by the DS− concentration and reaction temperature, and the basal spacing of the LRH-DS sample in the crystal edge is assumed to be larger than that in the crystal center. A higher DS− concentration and reaction temperature both induce more intercalation of DS− anions into the interlayer gallery, thus yielding a larger basal spacing. Unilamellar nanosheets with a lateral size of ≥60 μm and a thickness of ~ 1.6 nm can be obtained by delaminating LRH-DS in formamide. The resultant unilamellar nanosheets are single crystalline. Transparent (Y0.95Eu0.05)2O3 phosphor films with a uniform [111] orientation and a layer thickness of ~ 90 nm were constructed with the nanosheets as building blocks via spin-coating, followed by proper annealing. The oriented oxide film exhibits a strong red emission at 614 nm (the 5D0–7F2 transition of Eu3+), whose intensity is ~ 2 times that of the powder form owing to the significant exposure of the (222) facets.