Sep 14, 2011
High-yield graphite-encapsulated FeCo nanoparticles prepared for MRI test
Graphite-encapsulated metal alloy magnetic nanoparticles are attractive for various bio-applications including diagnostic and therapeutic uses thanks to the high magnetization of the encapsulated material. Scientists have explored a number of synthesis routes, but often encounter limitations in terms of scalability and economics because of demanding process conditions and low yields. Now, researchers from the Korea Research Institute of Chemical Technology have shown that well controlled graphite-encapsulated FeCo core-shell nanoparticles can be made via a hydrothermal method by simply mixing Fe/Co with sucrose as a carbon source.
The team, which includes scientists from the Nano-Bio Fusion Research Center, is focused on the development of nanomaterials for molecular imaging and biocompatible structures. A simple hydrothermal reaction and heat-treatment process is used to form the graphite encapsulated FeCo core-shell nanoparticles.
In a typical reaction, a mixture, consisting of Fe, Co species and sucrose as a carbon source, is stirred vigorously to form a clear solution. The contents are then placed in a 45 ml capacity Teflon-lined stainless steel autoclave, which is heated in an oven to 190 °C for 9 h. This method provides well controlled graphite-encapsulated FeCo core-shell nanoparticles and offers high production yields with reduced production costs. The technique also benefits from the use of simple equipment, readily available source materials, an absence of explosive or corrosive gases, and the use of de-ionized water as the reaction medium.
In their study, the researchers describe the potential use of graphite-coated FeCo nanoparticles as MRI contrast agents in terms of various Fe/Co metal ratios. To make the graphite-encapsulated nanoparticles soluble in water, the material was surface functionalized with a surfactant – sodium dodecylbenzene-sulfonate (NaDDBS).
The magnetization values and relaxivity coefficients of the nanoparticles are dependent on the Fe/Co ratio. FeCo/C nanoparticles with a Fe/Co ratio of 0.6/0.4 showed the largest magnetization value (230 e.m.u./g) and relaxivity coefficient (392 mM–1S–1).
More details can be found in the journal Nanotechnology.
About the author
The study was conducted by scientists from the Nano-Bio Fusion Research Center at the Korea Research Institute of Chemical Technology (KRICT) and the MRI Research Team at the Korea Basic Science Institute (KBSI), Korea. S J Lee is a PhD candidate in the J K Park group at the KRICT (group members: J K Park, J J Jung, S J Lee, M A Kim). They are currently exploring T1 MRI and T2 MRI contrast agents, and are paying attention to the application of multimodal particulate agents that combine fluorescence and MRI. The team focuses on new large-scale synthesis of monodisperse and single-crystalline magnetic nanomaterials by hydrothermal synthesis, which is very suitable for the preparation of large amounts of metal compounds, metal oxides and other types of quantum dots.