High-quality monodispersed copper nanowires with an ultrathin diameter of 13.5 nm, lengths up to 30 μm (aspect ratio >10 4 ) were successfully synthesized by a facile and controllable hydrothermal reduction procedure. The synthesis utilized glucose in the presence of hexadecylamine (HDA) and octadecylamine (ODA) as the capping agents. The copper decahedra nanoparticles with a low-surface-energy {111} plane formed pentatwinned one-dimensional nanowires, which was exactly verified by selected-area electron diffraction. Furthermore, the diameter and relative film conductivity of copper nanowires are sensitive to the HDA/ODA molar ratio. The conductor film made of the high-quality and ultrathin copper nanowires shows high transmittance and low resistance (83.83%, 61 Ω/□), exhibiting great potential in the applications of nanofabrication, transparent and flexible conductors, organic light-emitting diodes, and more.

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The controlled anisotropic growth of two-dimensional (2D) materials along a specific crystal axis is very crucial to explore the axis-dependent performance, which derives from the difference of atom arrangement in different crystal axes, while the relevant research is still insufficient. Here, we demonstrated a systematic investigation on the controllable anisotropic growth of 2D SnSe along different axis directions from both the experimental and theoretical perspectives. The anisotropy growth of 2D SnSe was attributed to the difference in atomic structures and bonding features between the zigzag edge (along the b-axis) and armchair edge (along the c-axis), as well as the chemical inertness of the base plane in the a-axis. Scanning transmission electron microscopy (STEM) images further verified that the long side of rectangular 2D SnSe is an armchair edge and the short side is a zigzag edge. The growth rates along the b-and c-axes could be effectively adjusted by hydrogen, attributed to the difference in desorption energy between hydrogen and different edge structures. The higher hydrogen concentration led to a shorter b-axis and a longer c-axis. The morphologies of 2D SnSe could be regulated in the range from square nanosheets to linear nanowires. In terms of the a-axis, 2D SnSe was precisely limited to a minimum value of 7.42 nm via a one-step rapid cooling method and could be further thinned to a bilayer using a two-step method with an additional annealing etching step. This study has demonstrated a facile strategy toward the structure-dependent controllable growth of 2D anisotropic materials, which shed new light on the orientation judgment and axisdependent mechanism of the crystal axis of anisotropic materials.

Electrochemical immunosensors are the largest class of affinity biosensing devices with strong practicability. In recent years, MXenes have become hotspot materials of electrochemical biosensors for their excellent properties, including large specific surface area, good electrical conductivity, high hydrophilicity and rich functional groups. In this review, we firstly introduce the composition and structure of MXenes, as well as their properties relevant to the construction of biosensors. Then, we summarize the recent advances of MXenes-based electrochemical immunosensors, focusing on the roles of MXenes in various electrochemical immunosensors. Finally, we analyze current problems of MXenes-based electrochemical immunosensors and propose an outlook for this research field.