Size and shape effects in beta-NaGdF4: Yb3+, Er3+ nanocrystals

作者：Noculak Agnieszka; Podhorodecki Artur^*

来源：Nanotechnology, 2017, 28(17): 175706.

DOI：10.1088/1361-6528/aa6522

• nanocrystals
• lanthanides
• aggregation
• spectroscopy

Three sets of. beta-NaGdF4: Yb3+, Er3+ nanocrystals (NCs) with different shapes ( spherical and more complex flower shapes), different sizes (6-17 nm) and Yb3+ concentrations (2%-15%) were synthesized by a co-precipitation method using oleic acid as a stabilizing agent. The uncommon, single-crystalline flower-shaped NCs were obtained by simply adjusting the fluorine-to-lanthanides molar ratio. Additionally, some of the NCs with different sizes have been covered by the un-doped shell. The crystal phase, shapes and sizes of all NCs were examined using transmission electron microscopy and x-ray diffraction methods. Simultaneously, upconversion luminescence and lifetimes, under 980 nm excitation, were measured and the changes in green to red (G/R) emission ratios as well as emission decay times were correlated with the evolution of nanocrystal sizes and surface to volume ratios. Three different mechanisms responsible for the changes in G/R ratios were presented and discussed.

• 出版日期2017-4-28