Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structure

다국어 초록 (Multilingual Abstract)

<P>Spherical mesoporous magnetite (Fe<SUB>3</SUB>O<SUB>4</SUB>) aggregates with a wormhole-like pore structure were successfully synthesized for the first time using a single iron precursor (iron(<SMALL>III</SMALL>) ethoxide) and an amphiphilic poly(ethylene oxide)-<I>block</I>-poly(propylene oxide)-<I>block</I>-poly(ethylene oxide) triblock copolymer (PEO<SUB>100</SUB>–PPO<SUB>65</SUB>–PEO<SUB>100</SUB>) as a soft template. In this synthesis, the interaction between the iron precursor and the triblock copolymer self-assemblies in ethanol leads to the assembly of magnetite nanocrystals into spherical mesoporous aggregates. These aggregates were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, standard and high-resolution transmission electron microscopy, <SUP>57</SUP>Fe Mössbauer spectroscopy, and X-ray diffraction, confirming the formation of pure-phase Fe<SUB>3</SUB>O<SUB>4</SUB> particles with monodisperse morphology (about 130 nm in diameter), three-dimensional wormhole-like mesopores, and highly crystalline spinel structure. In addition, a formation mechanism for this material in the present system is proposed, based on the analysis of results. The mesoporous magnetite has a high specific surface area of 165.6 m<SUP>2</SUP> g<SUP>−1</SUP>, and relatively large pores with a mean size of 5.2 nm. The magnetic susceptibility data demonstrate that this material exhibits superparamagnetic behavior.</P> <P>Graphic Abstract</P><P>The individual spinel-structured magnetite nanocrystals (about 5 nm in diameter) self-assemble into spherical aggregates (∼ 130 nm in diameter) with a three-dimensional wormhole-like mesopore structure.
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