Controlled Self-Assembly of Sm₂O₃ Nanoparticles into Nanorods: Simple and Large Scale Synthesis using Bulk Sm₂O₃ Powders

Abstract

Monodisperse samaria nanospheres and nanorods have been synthesized from commercial bulk Sm2O3 powders and various capping long-chain alkyl acids (e.g., oleic acid, myristic acid, decanoic acid). The synthesized materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform IR, thermogravimetric analysis, and N2 adsorption/desorption isotherms was employed to characterize these materials. The results revealed that the synthesis of nanorods consists of two steps of growth: (i) the nanoparticles were formed at relatively low temperature (120−140 °C) by Ostwald ripening and (ii) were followed by oriented attachment of these nanoparticles at higher temperature (160−200 °C) to produce the nanorods (average size of 7 nm × 160 nm). Furthermore, the width of nanorods can be controlled by the length of capping alkyl chain agents; on the basis of the experimental results, it seems that a longer alkyl chain agent leads to thinner nanorods; however, the length of nanorods remains unchanged. For the whole process, the possible Ostwald ripening and oriented attachment mechanisms were also discussed. The XPS results for the calcined nanorods sample shows the presence of two oxidation states, Sm3+/Sm2+ (it is found to be 40% Sm2+), and three components by deconvolution of O 1s peak indicating the defected structure. The surface chemical composition is found to be Sm2O3−x (x = 1.8). We believe that this synthetic method is simple, highly reproducible, inexpensive, and applicable for large-scale production.