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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 β-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.

Controlling the composition and phase formation of bulk and nanoscale solids underpins efforts to control physical properties. Here, we introduce a powerful new chemical pathway that facilitates composition-tunable synthesis, post-synthesis purification, and precise phase targeting in metal chalcogenide systems. When metal selenides and sulfides react with trioctylphosphine (TOP) at temperatures that range from 65 to 270 °C, selenium and sulfur are selectively extracted to produce the most metal-rich chalcogenide that is stable in a particular binary system. This general approach is demonstrated for SnSe(2), FeS(2), NiSe(2), and CoSe(2), which convert to SnSe, FeS, Ni(3)Se(2), and Co(9)Se(8), respectively. In-depth studies of the Fe-Se system highlight the precise phase targeting and purification that is achievable, with PbO-type FeSe (the most metal-rich stable Fe-Se phase) forming exclusively when other Fe-Se phases, including mixtures, react with TOP. This chemistry also represents a new template-based nanoparticle "conversion chemistry" reaction, transforming hollow NiSe(2) nanospheres into hollow NiSe nanospheres with morphological retention.

Multisegment template-grown metal nanowires have become important one-dimensional materials for a variety of applications in chemistry, physics, engineering, biology, and medicine. Segmented nanowires are traditionally fabricated in anodic alumina membranes using electrodeposition, and this technique is applicable to a range of metals, alloys, and semiconductors. Here we report an alternative and simple solution chemistry strategy for incorporating multimetal components of controllable length and composition into template-grown metal nanowires. By reacting membrane-confined nanowires with metal salt solutions under reducing conditions, site-specific diffusion occurs to convert one or both nanowire tips or the entire nanowire into a variety of multimetal phases. Platinum-based intermetallic compounds were chosen as targets for demonstrating the feasibility of the on-wire conversion chemistry.