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Abstract: Mackinawite, a metastable 1:1 compound of iron and sulfur that adopts an anti-PbO-type structure, is of interest because of its relationship to known iron chalcogenide superconductors, as well as its biogeochemical relevance. Colloidal nanosheets of mackinawite-type FeS were synthesized by first generating an amorphous Fe–S precursor via the aqueous room-temperature co-precipitation of Fe2+ and S2−, then solvothermally crystallizing it in ethylene glycol at 200°C in an autoclave. The product is highly crystalline, with lattice constants of a=3.674(3)Å and c=5.0354(3)Å. The nanosheets, with their surface normal oriented along the [001] direction, are irregularly faceted with edge lengths that range from 100nm to over 1μm and average thicknesses of approx. 30nm. The samples showed a ferromagnetic background signal with no evidence of superconductivity. [Copyright &y& Elsevier]

Two-dimensional (2D) alignment and crystallization of membrane proteins (MPs) is increasingly important in characterizing their three-dimensional (3D) structure, in designing pharmacological agents, and in leveraging MPs for biomimetic devices. Large, highly ordered MP 2D crystals in block copolymer (BCP) matrices are challenging to fabricate, but a facile and scalable technique for aligning and crystallizing MPs in thin-film geometries would rapidly translate into applications. This work introduces a novel method to grow larger and potentially better ordered 2D crystals by performing the crystallization process in the presence of a strong magnetic field. We demonstrate the efficacy of this approach using a ß-barrel MP, outer membrane protein F (OmpF), in short-chain polybutadiene-poly(ethylene oxide) (PB-PEO) membranes. Crystals grown in a magnetic field were up to 5 times larger than conventionally grown crystals, and a signal-to-noise (SNR) analysis of diffraction peaks in Fourier transforms of specimens imaged by negative-stain electron microscopy (EM) and cryo-EM showed twice as many high-SNR diffraction peaks, indicating that the magnetic field also improves crystal order. [ABSTRACT FROM AUTHOR]