Energy-Cascaded Upconversion in an Organic Dye-Sensitized Core/Shell Fluoride Nanocrystal

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• 作者：Guanying Chen ; Jossana Damasco ; Hailong Qiu ; Wei Shao ; Tymish Y. Ohulchanskyy ; Rashid R. Valiev ; Xiang Wu ; Gang Han ; Yan Wang ; Chunhui Yang ; Hans 脜gren ; Paras N. Prasad
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：November 11, 2015
• 年：2015
• 卷：15
• 期：11
• 页码：7400-7407
• 全文大小：430K
• ISSN：1530-6992

文摘

Lanthanide-doped upconversion nanoparticles hold promises for bioimaging, solar cells, and volumetric displays. However, their emission brightness and excitation wavelength range are limited by the weak and narrowband absorption of lanthanide ions. Here, we introduce a concept of multistep cascade energy transfer, from broadly infrared-harvesting organic dyes to sensitizer ions in the shell of an epitaxially designed core/shell inorganic nanostructure, with a sequential nonradiative energy transfer to upconverting ion pairs in the core. We show that this concept, when implemented in a core鈥搒hell architecture with suppressed surface-related luminescence quenching, yields multiphoton (three-, four-, and five-photon) upconversion quantum efficiency as high as 19% (upconversion energy conversion efficiency of 9.3%, upconversion quantum yield of 4.8%), which is about 鈭?00 times higher than typically reported efficiency of upconversion at 800 nm in lanthanide-based nanostructures, along with a broad spectral range (over 150 nm) of infrared excitation and a large absorption cross-section of 1.47 脳 10^鈥?4 cm² per single nanoparticle. These features enable unprecedented three-photon upconversion (visible by naked eye as blue light) of an incoherent infrared light excitation with a power density comparable to that of solar irradiation at the Earth surface, having implications for broad applications of these organic鈥搃norganic core/shell nanostructures with energy-cascaded upconversion.