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Large-Scale Synthesis of Ultrathin Manganese Oxide Nanoplates and Their Applications to T1 MRI Contrast Agents

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Mihyun Park†‡, Nohyun Lee†‡, Seung Hong Choi§, Kwangjin An†‡, Seung-Ho Yu‡, Jeong Hyun Kim†‡, Seung-Hae Kwon

, Dokyoon Kim†‡, Hyoungsu Kim§, Sung-Il Baek

, Tae-Young Ahn

, Ok Kyu Park

, Jae Sung Son†‡, Yung-Eun Sung‡, Young-Woon Kim

, Zhongwu Wang#, Nicola Pinna‡

, and Taeghwan Hyeon*†‡

National Creative Research Initiative Center for Oxide Nanocrystalline Materials, and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea

World Class University (WCU) Program of Chemical Convergence for Energy & Environment (C2E2), and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea

Diagnostic Radiology, Seoul National University Hospital, and Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul 110-744, Korea

School of Materials Science & Engineering, Seoul National University, Seoul 151-744, Korea

Korea Basic Science Institute, Chuncheon 200−701, Korea

Cornell High Energy Synchrotron Source and Wilson Laboratory, Cornell University, Ithaca, New York 14853, United States

Department of Chemistry and CICECO, University of Aveiro, 3810-193 Aveiro, Portugal

Chem. Mater., 2011, 23 (14), pp 3318–3324

DOI: 10.1021/cm200414c

Publication Date (Web): June 30, 2011

E-mail: thyeon@snu.ac.kr.

Section:

Inorganic Chemicals and Reactions

Abstract

Lamellar structured ultrathin manganese oxide nanoplates have been synthesized from thermal decomposition of manganese(II) acetylacetonate in the presence of 2,3-dihydroxynaphthalene, which promoted two-dimensional (2-D) growth by acting not only as a strongly binding surfactant but also as a structure-directing agent. Ultrathin manganese oxide nanoplates with a thickness of about 1 nm were assembled into a lamellar structure, and the width of the nanoplates could be controlled from 8 to 70 nm by using various coordinating solvents. X-ray absorption near-edge structure (XANES) spectra at the Mn K edge clearly showed that the nanoplates are mainly composed of Mn(II) species with octahedral symmetry. These hydrophobic manganese oxide nanoplates were ligand-exchanged with amine-terminated poly(ethyleneglycol) to generate water-dispersible nanoplates and applied to T1 contrast agents for magnetic resonance imaging (MRI). They exhibited a very high longitudinal relaxivity (r₁) value of up to 5.5 mM^–1s^–1 derived from their high concentration of manganese ions exposed on the surface, and strong contrast enhancement of in vitro and in vivo MR images was observed with a very low dose.