No abstract

The rapidly growing applications of nanomagnets require acid/base stable, oxidation-resistant shells with chemically controlled surface structure. An ideal core should be metallic and highly magnetic. We demonstrate the production of iron-based nanoparticles, ranging from iron oxide to iron and iron carbide, by systematically modifying the degree of reduction during flame spray synthesis under a controlled atmosphere. At a laboratory scale, continuous production yields iron-based particles of 20-50 nm at a production rate of >10 g h -1 . Carbon-encapsulated iron carbide (C/Fe 3 C) combines exceptionally high saturation magnetization (140 emu g -1 ), air stability (up to 200°C), and resistance against acidic dissolution (1 week in 24% HCl). The top graphene-like carbon layer could be covalently functionalized with various linkers, thus allowing us to chemically design the particle surface. Activity was demonstrated by reacting 2-phenyl ethyl amine functionalized nanomagnets with carboxylic acid chlorides as a model reaction. The present nanomagnets consist of biologically well-accepted constituents. They combine the required chemical reliability, improved magnetization if compared to magnetite with the potential for technical scale manufacturing, and therefore open stable nanomagnets to a broad range of fascinating separation problems (extraction/water treatment) and biomedical research.

Magnetic nanomaterials fi nd increasing application as separation agents to rapidly isolate target compounds from complex biological media (i.e., blood purifi cation). The responsiveness of the used materials to external magnetic fi elds (i.e., their saturation magnetization) is one of the most critical parameters for a fast and thorough separation. In the present study, magnetite (Fe 3 O 4 ) and non-oxidic cementite (Fe 3 C) based carbon-coated nanomagnets are characterized in detail and compared regarding their separation behavior from human whole blood. A quantifi cation approach for iron-based nanomaterials in biological samples with strong matrix effects (here, salts in blood) based on platinum spiking is shown. Both materials are functionalized with polyethyleneglycol (PEG) to improve cytocompatibility (confi rmed by cell toxicity tests) and dispersability. The separation performance is tested in two setups, namely under stationary and different fl ow-conditions using fresh human blood. The results reveal a superior separation behavior of the cementite based nanomagnets and strongly suggest the use of nanomaterials with high saturation magnetizations for magnetic retention under common blood fl ow conditions such as in veins.