Aggregation of Authigenic, Ferromagnetic-diamagnetic Nano-FexSy

Abstract Relevant to energy production is the aggregation of FexSy, which has received scant attention. This communication reports on the aggregation behaviour of FexSy by scanning and transmission electron microscopy. Micrographs confirmed authigenic FexSy to be composed of a mixture of FeS2 and Fe3S4. That is, ferromagnetic and diamagnetic properties prevailed. Meanwhile, ubiquitously found, thus stable, were 40-nm particles (NPs), 40-nm × l nanorods (linear aggregates of NPs), five-branched arrays (FBAs), and ≤ 2-μm densely packed icosahedral clusters (ISCs). NPs acted as buildings units, bricks or bridges between ISCs. Novel structures, FBAs, showing double stacked NPs. Stemming from prevailing magnetic properties was an unprecedented aggregation behaviour, evidenced by random ordering of NPs, coercivity at nanorods ends, and the formation of FBAs. We anticipate that our assays will be a starting point for more sophisticated experiments to address the aggregation mechanism(s) of authigenic FexSy, and consequent transport and transformation processes.