4 years ago

Single step synthesis of Er(3+) and Yb(3+) ions doped molybdate/Gd2O3 core-shell nanoparticles for biomedical imaging.

Grzegorz Wilczyński, Zofia Felcyn, Wojciech Paszkowicz, Jakub Mikulski, Mariusz Łapiński, Bozena Sikora, Piotr Stępień, Przemysław Kowalik, Izabela Kaminska, Anna Konopka, Wojciech Zaleszczyk, Krzysztof Fronc, Mirosława Pawlyta, Tomasz Wojciechowski, Piotr Samol, Małgorzata Baniewicz, Karolina Zajdel, Kamil Ciszak, Danek Elbaum, Maciej Szewczyk, Grzegorz Gruzeł, Mikołaj Donten, Roman Minikayev
Nanostructures as color-tunable luminescent markers have become major, promising tools for bioimaging and biosensing. The separated molybdate/Gd2O3 doped rare earth ions (erbium, Er(3+) and ytterbium, Yb(3+)) core-shell nanoparticles (NPs), were fabricated by a one step homogeneous precipitation process. Emission properties were studied by cathodo- and photoluminescence. The scanning electron and transmission electron microscopes were used to visualize and to determine the size and shape of the NPs. The spherical NPs were obtained. Their core-shell structures were confirmed by XRD and EDS measurements. We postulate that the molybdate rich core is formed due to high segregation coefficient of the Mo ion during the precipitation. The calcination process resulted crystallization of δ/ξ (core/shell) NPs doped Er and Yb ions , where δ - gadolinium molybdates and ξ - molybdates or gadolinium oxide. We confirmed two different upconversion mechanisms. In the presence of molybdenum ions, in the core of the NPs, Yb(3+)-MoO4(2-) (|(2)F7/2,(3)T2>) dimers were formed. As a result of a two 980 nm photons absorption by the dimer, we observed enhanced green luminescence in the upconversion process. But for the shell formed by the Gd2O3: Er,Yb NPs (without the Mo ions), the typical energy transfer upconversion (ETU) takes place which results in red luminescence. We demonstrated that the NPs were transported into cytosol of the HeLa and astrocytes cells by endocytosis. The core-shell NPs are sensitive sensors for the environment prevailing inside (shorter luminescence decay) and outside (longer luminescence decay) of the tested cells. Toxicity of the NPs was examined using MTT assay.

Publisher URL: http://doi.org/10.1088/1361-6528/aa9974

DOI: 10.1088/1361-6528/aa9974

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