Self-assembly of Eu$_{2}$O$_{3}$ nanoneedles and nanocrystals

Growth of anisotropic nanostructures starting from isotropic nanostructures is observed in Eu$_{2}$O$_{3}$ system. Anisotropic structures, like nanoneedles and nanospindles, are grown from the concentrated solution of Eu$_{2}$O$_{3}$ nanocrystals. This process involved the stepwise thermal growth of nanocrystals into ordered, high aspect ratio, one dimensional nanoneedles and the subsequent assembly of said nanoneedles into larger, oriented bundles (nanospindles). The Eu$_{2}$O$_{3}$ nanocrystals were synthesized following a room temperature, colloidal chemistry procedure, adapted from the synthesis of G. Wakefield \textit{et al}.$^{1}$ We present the results of this self-assembly phenomenon using 4-nm Eu$_{2}$O$_{3}$ nanocrystals. High resolution transmission electron microscopy was employed to characterize the approximate shape, size distribution, and crystallinity of the nanostructures. Absorption and photoluminescence measurements were performed to investigate what effect the size and shape of materials has on optical properties. 1. G. Wakefield, H. A. Keron, P. J. Dobson, and J. L. Hutchison, J. of Coll. Interf. Sci. \textbf{215}, 179, 1999.