Colloidal assembly into chiral superstructures is usually accomplished with templating or lithographic patterning methods that are only applicable to materials with specific compositions and morphologies over narrow size ranges. Here, chiral superstructures can be rapidly formed by magnetically assembling materials of any chemical compositions at all scales, from molecules to nano- and microstructures. We show that a quadrupole field chirality is generated by permanent magnets caused by consistent field rotation in space. Applying the chiral field to magnetic nanoparticles produces long-range chiral superstructures controlled by field strength at the samples and orientation of the magnets. Transferring the chirality to any achiral molecules is enabled by incorporating guest molecules such as metals, polymers, oxides, semiconductors, dyes, and fluorophores into the magnetic nanostructures.

The wide accessibility to nanostructures with high uniformity and controllable sizes and morphologies provides great opportunities for creating complex superstructures with unique functionalities. Employing anisotropic nanostructures as the building blocks significantly enriches the superstructural phases, while their orientational control for obtaining long-range orders has remained a significant challenge. One solution is to introduce magnetic components into the anisotropic nanostructures to enable precise control of their orientations and positions in the superstructures by manipulating magnetic interactions. Recognizing the importance of magnetic anisotropy in colloidal assembly, we provide here an overview of magnetic field-guided self-assembly of magnetic nanoparticles with typical anisotropic shapes, including rods, cubes, plates, and peanuts. The Review starts with discussing the magnetic energy of nanoparticles, appreciating the vital roles of magneto-crystalline and shape anisotropies in determining the easy magnetization direction of the anisotropic nanostructures. It then introduces superstructures assembled from various magnetic building blocks and summarizes their unique properties and intriguing applications. It concludes with a discussion of remaining challenges and an outlook of future research opportunities that the magnetic assembly strategy may offer for colloidal assembly.

Steelmaking contributes 8% to the total CO ₂ emissions globally, primarily due to coal-based iron ore reduction. Clean hydrogen-based ironmaking has variable performance because the dominant gas–solid reduction mechanism is set by the defects and pores inside the mm- to nm-sized oxide particles that change significantly as the reaction progresses. While these governing dynamics are essential to establish continuous flow of iron and its ores through reactors, the direct link between agglomeration and chemistry is still contested due to missing measurements. In this work, we directly measure the connection between chemistry and agglomeration in the smallest iron oxides relevant to magnetite ores. Using synthesized spherical 10-nm magnetite particles reacting in H ₂ , we resolve the formation and consumption of wüstite (Fe _1-x O)—the step most commonly attributed to whiskering. Using X-ray diffraction, we resolve crystallographic anisotropy in the rate of the initial reaction. Complementary imaging demonstrated how the particles self-assemble, subsequently react, and grow into elongated “whisker” structures. Our insights into how morphologically uniform iron oxide particles react and agglomerate in H ₂ reduction enable future size-dependent models to effectively describe the multiscale aspects of iron ore reduction.

A novel polymer electrolyte based on lithiated perfluorinated sulfonic acid ionomer (PFSA-Li) and poly(tetrafluoroethylene) (PTFE) was prepared, and its performance in the Li-O₂ batteries was evaluated. In this polymer electrolyte, porous PTFE membrane was used as supporting substrate to provide mechanical strength and dimensional stability, and PFSA-Li ionomer was employed as polymer electrolyte to fill into the pores of the PTFE substrate. After swollen with anhydrous dimethyl sulfoxide solvent, the PFSA-Li/PTFE polymer electrolyte showed a high room temperature ionic conductivity of 1.5 × 10⁻⁴ S cm⁻¹ and a high lithium transference number of 0.84. Its use in a lithium-oxygen battery demonstrated excellent compatibility to lithium anode with stable interface property and dendrite-free Li deposition. A good cycling stability over 90 cycles at 1000 mAh g⁻¹ and rate capability up to 2 A g⁻¹ were obtained suggesting a feasible strategy for developing large-scale Li-O₂ battery systems toward high energy and high power application with polymer electrolytes.

A chiral magnetic field brings magnetoplasmonic nanoparticles into close proximity, enabling plasmonic coupling and imparting chirality to resulting superstructures, and consequently, dynamic tunability of plasmonic chiroptical properties.