The family of emerging low‐symmetry and structural in‐plane anisotropic two‐dimensional (2D) materials has been expanding rapidly in recent years. As an important emerging anisotropic 2D material, the black phosphorene analog group IV A –VI metal monochalcogenides (MMCs) have been surged recently due to their distinctive crystalline symmetries, exotic in‐plane anisotropic electronic and optical response, earth abundance, and environmentally friendly characteristics. In this article, the recent research advancements in the field of anisotropic 2D MMCs are reviewed. At first, the unique wavy crystal structures together with the optical and electronic properties of such materials are discussed. The Review continues with the various methods adopted for the synthesis of layered MMCs including micromechanical and liquid phase exfoliation as well as physical vapor deposition. The last part of the article focuses on the application of the structural anisotropic response of 2D MMCs in field effect transistors, photovoltaic cells nonlinear optics, and valleytronic devices. Besides presenting the significant research in the field of this emerging class of 2D materials, this Review also delineates the existing limitations and discusses emerging possibilities and future prospects.

Two-dimensional (2D) tin(II) monosulfide (SnS) with strong structural anisotropy has been proven to be a phosphorene analog. However, difficulty in isolating a very thin layer of SnS poses challenges in practical utilization. Here, we prepare ultrathin SnS via liquid-phase exfoliation. With transmission electron microscopy, we identify the buckled structure of 2D SnS. We employ temperature dependent Raman spectroscopy to elucidate electron-phonon interactions, which reveals a linear phonon shifts. The active Raman modes of ultrathin SnS exhibit higher sensitivity to temperature than other 2D materials. Moreover, we demonstrate strong light-matter interaction in ultrathin SnS using Z-scan and ultrafast spectroscopy. Rich exciton-exciton and coherent exciton-photon interactions arising from many-particle excited effects in ultrathin SnS eventually enhances the nonlinear optical properties. Our findings highlight the prospects for the synthesis of ultrathin anisotropic SnS towards the betterment of thermoelectric and photonic devices.npj 2D Materials and Applications (2020) 4:1 ; https://doi.

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Heterostructures of zero-dimensional/two-dimensional (0D/2D) materials, especially quantum dots (QDs)/nanosheets (NSs), have attracted significant attention for extracting photogenerated electrons and holes. Herein, we report the dissociation of excitons at the heterojunction of CdSe (cadmium selenide) QDs and MoS 2 (molybdenum disulfide) nanosheet utilizing steady-state and time-resolved spectroscopic techniques. Quasi type II semiconductor-like band energy alignment of the 0D/2D heterojunction facilitates exciton breaking via hole transfer from the QD to MoS 2 . Furthermore, we demonstrate the extraction of two holes from doubly excited QDs (created via high-power excitation) following the dissociation of a biexciton at the 0D/2D interface. This work is expected to provide a new approach of exploiting multiple exciton generation in quantum dot-sensitized solar cells by harvesting multiple carriers.