In this work, we demonstrated that B nanosheets can be applied for self-powered photodetectors with superior photoresponsivity and excellent stability.

Two-dimensional germanium sulfide (GeS), an analogue of phosphorene, has attracted broad attention owing to its excellent environmental stabilities, fascinating electronic and optical properties, and applications in various nanodevices. In spite of the current achievements on 2D GeS, the report of ultrathin few-layer GeS nanosheets within 5 nm is still lacking. Here in this contribution, we have achieved preparation of ultrathin few-layer GeS nanosheets with thicknesses of 1.3 ± 0.1 nm [approximately three layers (∼3L)], 3.2 ± 0.2 nm (∼6L), and 4.2 ± 0.3 nm (∼8L) via a typical liquid-phase exfoliation (LPE) method. Based on various experimental characterizations and first-principles calculations, the layer-dependent electronic, transport, and optical properties are investigated. For the few-layer GeS nanosheets, enhanced light absorption in the UV–vis region and superior photoresponse behavior with increasing layer number is observed, while for the thin films above 10 nm, the properties degenerate to the bulk feature. In addition, the as-prepared ultrathin nanosheets manifest great potential in the applications of photoelectrochemical (PEC)-type photodetectors, exhibiting excellent and stable periodic photoresponse behavior under the radiation of white light. The ∼8L GeS-based photodetector exhibits superior performance than the thinner GeS nanosheets (<4 nm), even better as compared to the bulk or film (above 10 nm) counterparts in terms of higher photoresponsivity along with remarkable photodetection performance in the UV–vis region. This work not only provides direct and solid evidence of the layer-number evolutionary band structure, mobility, and optical properties of ultrathin 2D GeS nanosheets but also promotes the foreseeable applications of 2D GeS as energy-related photoelectric devices.

Inorganic luminescent semiconductors have triggered burgeoning research interest in all‐solid‐state light‐emitting devices over the past decades owing to their band‐to‐band transitions along with their high efficiency and excellent long‐term stability compared with most organic luminescent materials. Recent booming developments in 2D materials demonstrate their fascinating tunable layer‐dependent electronic structures, strong light–matter interactions, high carrier mobilities, and broad spectral ranges at the 2D limit, which are promising for high‐performance light‐emitting devices. Here, state‐of‐the‐art 2D luminescent nanomaterials are reviewed from the fundamental aspects of crystal structures and electronic properties to practical applications, providing insights into the luminescence mechanism. Many research paradigms are comprehensively discussed to elaborate ingenious luminescence modulation strategies through control of the microstructure, such as the number of layers, defects, morphologies, charge carriers, heterostructures, and surface states of 2D systems. Promising applications of 2D luminescent systems in light‐emitting diodes, lasers, and bioimaging and biosensing devices are systematically illustrated. Finally, by summarizing the luminescence in 2D materials, challenges are proposed, which will provide new opportunities for developing 2D luminescence physics, luminescent materials, and related light‐emitting device applications.

Surface functionalization is considered to be an effective and versatile strategy to tailor intrinsic electronic and optoelectronic properties of 2D materials. In this work, surface‐decorated few‐layer antimonene is synthesized by a one‐step electrochemical exfoliation and synchronous halogenation method in halogen‐containing an ionic liquid–based electrolyte at room temperature. The prepared halogenated antimonene nanosheets are composed of oxygen‐ and halogen‐decorated amorphous and crystalline domains. The structural reconstructions and evolutions of halogenated antimonene are further revealed by ab initio molecular dynamics simulations and first‐principles calculations. The band structures and optical properties of antimonene can be tailored after amorphization and surface functionalization, depending on the reactivity of different halogens. The photoresponse performance of the halogenated antimonene is further evaluated by photoelectrochemical measurement. Exhibiting self‐powered photoresponse behavior, their photocurrent density increases with the increases of external bias potential and light intensity. This work proposes a new idea of tuning the optoelectronic properties of 2D materials by synchronous halogenation in the facile one‐step electrochemical synthesis process. Benefiting from this facile synthesis procedure, the halogenation of antimonene may shed light on chemical functionalization of other 2D materials for electronic and optoelectronic applications.

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