Controlled substitutional doping of two-dimensional transition-metal dichalcogenides (TMDs) is of fundamental importance for their applications in electronics and optoelectronics. However, achieving p-type conductivity in MoS2 and WS2 is challenging because of their natural tendency to form n-type vacancy defects. Here, we report versatile growth of p-type monolayer WS2 by liquid-phase mixing of a host tungsten source and niobium dopant. We show that crystallites of WS2 with different concentrations of substitutionally doped Nb up to 1014 cm–2 can be grown by reacting solution-deposited precursor film with sulfur vapor at 850 °C, reflecting the good miscibility of the precursors in the liquid phase. Atomic-resolution characterization with aberration-corrected scanning transmission electron microscopy reveals that the Nb concentration along the outer edge region of the flakes increases consistently with the molar concentration of Nb in the precursor solution. We further demonstrate that ambipolar field-effect transistors can be fabricated based on Nb-doped monolayer WS2.

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A BiOCl-Bi2WO6 heterojunction with a chemically bonded interface was synthesized via a facile one-step solvothermal method. A series of characterization techniques (XRD, XPS, TEM, SEM, EDS etc.) confirmed the existence of a BiOCl-Bi2WO6 interface. The heterojunction yielded a higher photodegradation rate of Rhodamine B under visible light irradiation compared to its individual components. Theoretical studies based on density functional theory calculations indicated that the enhanced photosensitized degradation activity could be attributed to the favorable band offsets across the BiI-O-BiII bonded interface, leading to efficient interfacial charge carrier transfer. Our results reveal the photosensitized mechanism of BiOCl-Bi2WO6 heterojunctions and demonstrate their practical use as visible-light-driven photocatalytic materials.

A major drawback of traditional photocatalysts like TiO2 is that they can only work under illumination, and the light has to be UV. As a solution for this limitation, visible-light-driven energy storage photocatalysts have been developed in recent years. However, energy storage photocatalysts that are full-sunlight-driven (UV-visible-NIR) and possess long-lasting energy storage ability are lacking. Here we report, a Pt-loaded and hydrogen-treated WO3 that exhibits a strong absorption at full-sunlight spectrum (300–1,000 nm), and with a super-long energy storage time of more than 300 h to have formaldehyde degraded in dark. In this new material system, the hydrogen treated WO3 functions as the light harvesting material and energy storage material simultaneously, while Pt mainly acts as the cocatalyst to have the energy storage effect displayed. The extraordinary full-spectrum absorption effect and long persistent energy storage ability make the material a potential solar-energy storage and an effective photocatalyst in practice.

The recent development of 2D material-based chemiresistive- and FET-type gas sensors as well as their future directions are comprehensively presented.

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