Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structureElectronic supplementary information (ESI) available: Fig. S1: schematic diagram for a unit cell of magnetite (Fe3O4); Fig. S2: TGA and DSC curves of as-prepared mesoporous magnetite before calcination; Table S1: the standard 2 values and relative intensity for magnetite (Fe3O4) with respective diffraction planes (JCPDS file, No. 19-0629); Table S2: the standard 2 values and relative in

Spherical mesoporous magnetite (Fe 3 O 4 ) aggregates with a wormhole-like pore structure were successfully synthesized for the first time using a single iron precursor (iron( iii ) ethoxide) and an amphiphilic poly(ethylene oxide)- block -poly(propylene oxide)- block -poly(ethylene oxide) triblock copolymer (PEO 100 -PPO 65 -PEO 100 ) 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, 57 Fe Mössbauer spectroscopy, and X-ray diffraction, confirming the formation of pure-phase Fe 3 O 4 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 2 g −1 , and relatively large pores with a mean size of 5.2 nm. The magnetic susceptibility data demonstrate that this material exhibits superparamagnetic behavior. 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.