Hollow structures have demonstrated great potential in drug delivery owing to their privileged structure, such as high surface-to-volume ratio, low density, large cavities, and hierarchical pores. In this review, we provide a comprehensive overview of hollow structured materials applied in targeting recognition, smart response, and drug release, and we have addressed the possible chemical factors and reactions in these three processes. The advantages of hollow nanostructures are summarized as follows: hollow cavity contributes to large loading capacity; a tailored structure helps controllable drug release; variable compounds adapt to flexible application; surface modification facilitates smart responsive release. Especially, because the multiple physical barriers and chemical interactions can be induced by multishells, hollow multishelled structure is considered as a promising material with unique loading and releasing properties. Finally, we conclude this review with some perspectives on the future research and development of the hollow structures as drug carriers.

Single-atom catalysts (SACs) are emerging as the most promising catalysts for various electrochemical reactions. The isolated dispersion of metal atoms enables high density of active sites, and the simplified structure makes them ideal model systems to study the structure–performance relationships. However, the activity of SACs is still insufficient, and the stability of SACs is usually inferior but has received little attention, hindering their practical applications in real devices. Moreover, the catalytic mechanism on a single metal site is unclear, leading the development of SACs to rely on trial-and-error experiments. How can one break the current bottleneck of active sites density? How can one further increase the activity/stability of metal sites? In this Perspective, we discuss the underlying reasons for the current challenges and identify precisely controlled synthesis involving designed precursors and innovative heat-treatment techniques as the key for the development of high-performance SACs. In addition, advanced operando characterizations and theoretical simulations are essential for uncovering the true structure and electrocatalytic mechanism of an active site. Finally, future directions that may arise breakthroughs are discussed.

As a new type of carbon allotrope material, GDY possesses rich acetylenic bonds and unique pore structures, prompting GDY an ideal candidate tuning its electronic structure by introducing heteroatoms, broadening...

Electrodes with a high areal capacity are critical for developing high-energy-density sodium-ion batteries (SIBs). The freestanding thick electrode is a promising candidate among the state-of-art electrodes, since it has the advantages of high areal mass, binder-free, current-collector-free, and no carbon additive; thus, the whole mass of the electrode is an active material that can contribute to capacity. However, enhancing areal density by introducing thick electrodes impinges on the transport of charge carriers including ions and electrons. Here we designed and synthesized an ultrathick (1500 μm) free-standing foam, which is a carbon framework with 1T-MoS 2 nanosheets embedded in the vertically aligned channel wall. To tune the areal mass and morphology of the as-obtained foam, a confined iterative self-assembly strategy was proposed. The Na + storage behavior was studied by using the as-obtained foam as a free-standing electrode against Na metal. Consequently, it displays good cycle stability even with a high areal mass of 20.74 mg cm −2 and delivers an astonishing reversible areal capacity of 19.75 mAh cm −2 at 0.01 A g −1 , which greatly exceeds that of most sodium storage materials. The proposed confined iterative self-assembly strategy for fabricating thick electrodes opens new avenues for high areal capacity batteries.