Search

Ultrathin semiconducting van der Waals (vdW) heterostructures based on transition metal dichalcogenides (TMDs) play a critical role in developing next‐generation electronic and optoelectronic devices. The replacement of one component of the heterostructure by transition metal oxides (TMOs) certainly brings in numerous benefits including long‐term stability and novel functionalities. However, the single‐step chemical‐vapor deposition growth of TMOs/TMDs vdW heterostructures, as a highly desired approach for large‐scale fabrication and practical implementation, is challenging due to contradictory growth atmospheres of TMOs and TMDs. Here, the single‐step growth of an ultrathin WO3–x/WS2 vdW heterostructure based on the quantity‐driven discrepant interaction between S and the precursor, in which S induces sulfidation to produce WS2 in the S‐rich phase and is changed to the reduction role to obtain sub‐stoichiometric WO3–x in the S‐deficient phase is realized. Both WO3–x and WS2 exhibit semiconducting properties with a favorable type‐II band alignment. A wide response across the entire visible spectrum with a large photo‐responsivity of 4375 A W−1, a detectivity of 5.47 × 1011 Jones, and sub‐ms switching kinetics at 405 nm is achieved without gating bias, which is significantly improved over other reported ultrathin vdW heterostructures. This study demonstrates the possibility of single‐step‐growing TMOs/TMDs vdW heterostructures and their strong potential in high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

Bacteria-inspired magnetic helical micro-/nanoswimmers can be actuated and steered in a fuel-free manner using a low-strength rotating magnetic field, generating remotely controlled 3D locomotion with high precision in a variety of biofluidic environments. They are therefore envisioned for biomedical applications related to targeted diagnosis and therapy. In this article, a porous hollow microswimmer possessing an outer shell aggregated by mesoporous spindle-like magnetite nanoparticles (NPs) and a helical-shaped inner cavity is proposed. The fabrication is straightforward via a cost-effective mass-production process of biotemplated synthesis using helical microorganisms. Here, Spirulina-based fabrication is demonstrated as an example. The fabricated microswimmers are superparamagnetic and exhibit low cytotoxicity. They are also capable of performing structural disassembly to form individual NPs using ultrasound when needed. For the first time in the literature of helical microswimmers, a porous hollow architecture is successfully constructed, achieving an ultrahigh specific surface area for surface functionalization and enabling diffusion-based cargo loading/release. Furthermore, experimental and analytical results indicate better swimming performance of the microswimmers than the existing non-hollow helical micromachines of comparable sizes and dimensions. These characteristics of the as-proposed microswimmers suggest a novel microrobotic tool with high loading capacity for targeted delivery of therapeutic/imaging agents in vitro and in vivo. [ABSTRACT FROM AUTHOR]