Transition metal oxides have attracted intense interest owing to their abundant physical and chemical properties. The controlled preparation of large-area, high-quality two-dimensional crystals is essential for revealing their inherent properties and realizing high-performance devices. However, fabricating two-dimensional (2D) transition metal oxides using a general approach still presents substantial challenges. Herein, we successfully achieve highly crystalline nickel oxide (NiO) flakes with a thickness as thin as 3.3 nm through the salt-assisted vapor–liquid–solid (VLS) growth method, which demonstrated exceptional stability under ambient conditions. To explore the great potential of the NiO crystal in this work, an artificial synapse based on the NiO-flake resistive switching (RS) layer is investigated. Short-term and long-term synaptic behaviors are obtained with external stimuli. The artificial synaptic performance provides the foundation of the neuromorphic application, including handwriting number recognition based on artificial neuron network (ANN) and the virtually unsupervised learning capability based on generative adversarial network (GAN). This pioneering work not only paves new paths for the synthesis of 2D oxides in the future but also demonstrates the substantial potential of oxides in the field of neuromorphic computing.

Floating catalysis chemical vapor deposition (FCCVD) direct spinning process is an attractive method for fabrication of carbon nanotube fibers (CNTFs). However, the intrinsic structural defects, such as entanglement of the constituent carbon nanotubes (CNTs) and inter-tube gaps within the FCCVD CNTFs, hinder the enhancement of mechanical/electrical properties and the realization of practical applications of CNTFs. Therefore, achieving a comprehensive reassembly of CNTFs with both high alignment and dense packing is particularly crucial. Herein, an efficient reinforcing strategy for FCCVD CNTFs was developed, involving chlorosulfonic acid-assisted wet stretching for CNT realigning and mechanical rolling for densification. To reveal the intrinsic relationship between the microstructure and the mechanical/electrical properties of CNTFs, the microstructure evolution of the CNTFs was characterized by cross-sectional scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), polarized Raman spectroscopy and Brunauer–Emmett–Teller (BET) analysis. The results demonstrate that this strategy can improve the CNT alignment and eliminate the inter-tube voids in the CNTFs, which will lead to the decrease of mean distance between CNTs and increase of inter-tube contact area, resulting in the enhanced inter-tube van der Waals interactions. These microstructural evolutions are beneficial to the load transfer and electron transport between CNTs, and are the main cause of the significant enhancement of mechanical and electrical properties of the CNTFs. Specifically, the tensile strength, elastic modulus and electrical conductivity of the high-performance CNTFs are 7.67 GPa, 230 GPa and 4.36 × 10⁶ S/m, respectively. It paves the way for further applications of CNTFs in high-end functional composites.

Implantable artificial muscles are of great importance for muscle function restoration and physical augmentation but are still challenging. Herein, we report an artificial muscle by soaking-polymerization of polyaniline (PANI) inside a carbon nanotube (CNT) yarn. Working in aqueous biocompatible solutions, the yarn muscle generates a large contractile stroke of 17% and high isometric stress of 8 MPa at voltages lower than 2 V. The excellent performance can be ascribed to the large actuation volume that is enabled by the fast electrochemical redox of PANI confined in a coiled yarn structure. The actuation performance outperforms that of previously reported aqueous artificial yarn muscles. Moreover, the yarn muscle can work well and maintain excellent actuating performance in other biocompatible solutions such as normal saline and Na₂SO₄ aqueous solution, which makes the CNT/PANI yarn muscles suitable for implantable bionic applications. Finally, a biomimetic arm was fabricated to demonstrate the applications of the CNT/PANI yarn artificial muscle in implantable muscle, underwater robots, and soft exoskeletons.

Aligned arrays of semiconducting carbon nanotubes (s-CNTs) with high homogenous density and orientation are urgently needed for high-performance carbon-based electronics. Herein, a length-controlled approach using combined technologies was developed to regulate the s-CNT length and reduce the length distribution. The impact of different lengths and length distributions was studied during aligned self-assembly on a liquid–liquid confined interface was investigated. The results show that short s-CNTs with a narrow distribution have the best alignment uniformity over the large scale. The optimized and aligned s-CNT array can reach a density as high as 100 CNTs·μm⁻¹ on a 4-inch wafer. The field-effect transistor (FET) performance of these optimized s-CNT arrays was 64% higher than arrays without length-control. This study clarified that rational control of s-CNTs with desired length and length distribution on the aligned self-assembly process within the liquid–liquid confined interface. The results illustrate a solid foundation for the application of emerging carbon-based electronics.

A scalable approach to obtaining high-density, large-area single-walled carbon nanotube (SWNT) arrays is essential for realizing the full potential of SWNTs in practical electronic devices; this is still a great challenge. Here, we report an improved synthetic method for large-area growth of ultra-high-density SWNT arrays on sapphire surfaces by combining Trojan catalysts (released from the substrate, to assure ultra-high density) with Mo nanoparticles (loaded on the surface, to stabilize the released Trojan catalysts) as cooperating catalysts. Dense and perfectly aligned SWNTs covered the entire substrate and the local density was as high as 160 tubes/μm. Field-effect transistors (FETs) built on such arrays gave an output current density of -488 μA/μm at the drain-source voltage (V_ds) = the gate-source voltage (V_gs) =–2 V, corresponding to an on-conductance per width of 244 μS/μm. These results confirm the wide range of potential applications of Trojan-Mo catalysts in the structure-controlled growth of SWNTs.