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Date: Tuesday, February 21, 2017
Time: 11:00 am
Speaker: Guanying Chen, Harbin Institute of Technology
Title: Dye-Sensitized Lanthanide-Doped Inorganic Core/Shell Nanostructures in the Near Infrared Range
Location: 67-3111 Chemla Room


Lanthanide-doped upconverting and downshifting nanoparticles hold promises for applications ranging from solar cells to bioimaging. However, their emission brightness and excitation wavelength range are limited by the weak and narrowband absorption of the doped lanthanide ions, creating a long-standing obstacle for a comprehensive range of technolgical applications. This limitation primarly associates with the parity-forbidden nature of the 4f-4f electronic transitions of trivalent lanthanide ions. Here, I present our recent progress on exploiting hybrid inorganic-organic systems to address this problem, which consist of an epitaxial core/shell inorganic nanocrystal and near infrared (NIR) dyes anchored on the core/shell nanocrystal surface. We employed the dye attena effect to broadly and strongly harvest NIR light first, and then directed the harvested energy to migrate across both the organic-inorganic (dye/shell) interface and the inorganic core/shell interface, and finally to activate the emitting lanthanide ions positioned the inorganic core in a designated way. This strategy allows us to yield 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, and to produce tunable narrow-band downshifting photoluminescence for deep tissue bioimaging in the second biological window.