In this work, Janus monolayers are predicted for a new 2D MA2Z4 family by means of first-principles calculations. The predicted MSiGeN4 (M = Mo and W) monolayers exhibit dynamic, thermodynamic and mechanical stability, and they are indirect band-gap semiconductors.

The dynamically and mechanically stable Janus SnSSe monolayer has distinctive electronic, optical, piezoelectric and transport properties.

Monochiral single-walled carbon nanotubes (SWCNTs) are promising materials with potential applications in 3D integrated circuits and optoelectronic hybrid circuits. However, the purity and device performance of monochiral SWCNTs are still far lower than expected. Here, the authors demonstrate that specific monochiral SWCNTs can be wrapped by conjugated polymers containing pyridine units, and the supramolecular assemblies show surprising suspension stability even after high-intensity ultracentrifugation. Additionally, two novel methods are developed, namely, enhanced ultracentrifugation (E-UCG) and stepwise extraction processing (STEP), which successfully achieve isolation of (10,8) and (12,5) SWCNTs with respective diameters of 1.24 and 1.2 nm at high monochiral purity (92.3% and 95.6%). Their S 11 absorption and fluorescence emission peaks are both at ≈1.5 µm (optical telecommunications C-band). Both micro-and nanoscale field-effect transistor (FET) devices can be fabricated from the as-isolated (10,8) SWCNTs, and these FETs exhibit excellent electrical performance and a high semiconducting purity of up to 99.94%.

black arsenic phosphorus (b-AsP), as an alloy of black phosphorus (b-P) with arsenic, has attracted great attention because of its outstanding electronic and optical properties, including high carrier mobility, tunable bandgap and in-plane anisotropy. B-AsP has a smaller bandgap (0.15-0.3 eV) than the b-P bandgap (0.3-2.0 eV), and thus can be used for mid-infrared photodetectors. In addition, both of them can form various van der Waals (vdW) heterojunctions with other 2D materials to realize novel functional optoelectronic devices. Here, we compare the basic characteristics of b-AsP and b-P, including crystal structure, optical properties, band structure, electrical properties and stability, and we summarize the update progress of b-AsP in photo detection, including representatives of phototransistor and photodiode devices. In the last part, the future research directions are discussed.