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Synthesis of Uniformly Sized Manganese Oxide Nanocrystals with Various Sizes and Shapes and Characterization of Their T 1 Magnetic Resonance Relaxivity
Author(s) -
An Kwangjin,
Park Mihyun,
Yu Jung Ho,
Na Hyon Bin,
Lee Nohyun,
Park Jongnam,
Choi Seung Hong,
Song In Chan,
Moon Woo Kyung,
Hyeon Taeghwan
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201101193
Subject(s) - nanocrystal , chemistry , manganese , oxide , crystallography , nuclear magnetic resonance , nanotechnology , materials science , organic chemistry , physics
We synthesized manganese oxide (MnO and Mn 3 O 4 ) nanocrystals with various sizes and shapes by the thermal reaction of a Mn II –oleate complex through a “heat‐up process”. When a Mn II –oleate complex was thermally decomposed in non‐coordinating hydrocarbon solvents, uniformly sized MnO nanocrystals with cubic and octahedral shapes were produced. We were able to synthesize anisotropic, multibranched MnO nanocrystals by the oriented attachment of MnO truncated‐nanocube building blocks. When the Mn II –oleate complex was heated in 1‐hexadecene in the presence of strongly coordinating carboxylic acid surfactants, spherical nanocrystals were generated, and their diameter was controlled in the range 3–13 nm by varying the chain length of the carboxylic acid. When oleyl alcohol was added to the Mn–oleate complex in phenyl ether, tetrahedral MnO nanocrystals were synthesized. The as‐synthesized MnO nanocrystals were oxidized in air to Mn 3 O 4 or MnO/Mn 3 O 4 core–shell structures, which exhibited exchange coupling with shifted magnetic hysteresis loops. The effect of the size and shape of the phospholipid‐capped manganese oxide nanocrystals on their applicability as T 1 contrast agents in magnetic resonance imaging (MRI) were examined. As the size of the nanocrystals decreased, their relaxivities increased, thereby generating brighter MR images. In particular, spherical 3 nm‐sized Mn 3 O 4 nanocrystals had a high specific relaxivity ( r 1 ) of 2.38 m M –1 s –1 , clearly demonstrating their potential for use as an efficient T 1 MRI contrast agent.