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Layered metal dichalcogenides (LMDs) are promising gas-sensing materials due to their high specific surface area and satisfactory electrical conductivity. However, virgin LMD-based gas sensors have several performance constraints, including low sensor sensitivity and poor detection limits, which need to be addressed urgently. Cation-doping-induced vacancy engineering is an appealing route to improve the gas-sensing performance of LMDs by modulating their electronic structures and chemical properties. In this work, indium-doped tin diselenide (In–SnSe2) nanosheets were synthesized via a one-step hydrothermal strategy, resulting in a sulfur dioxide (SO2) sensor with improved sensitivity (4.85 ppm−1) and a low detection limit (3.46 ppb). Compared with the pristine SnSe2 sensor, the In-doped SnSe2 sensor with a vintage doping ratio has enhanced the SO2 response (72.45% vs. 38.66% to 5 ppm) at room temperature (25 °C). In addition, the In-doped SnSe2 sensor shows rapid reaction time, outstanding SO2 selectivity, as well as exceptional stability. According to experimental investigation and density functional theory (DFT) calculations, doped-In and induced-Se vacancies have opposite roles in SO2 sensing, which yields the optimum doping ratio with the highest gas response. This study sheds light on the sensitization mechanism and promotes the development of high-performance gas sensors based on doped 2D LMDs. [ABSTRACT FROM AUTHOR]

The high-operating temperature and poor selectivity of metal oxide semiconductor (MOS)-based chemiresistive-type gas sensors severely limit their application in the future Internet of Things (IoT), which need a lower power consumption and a higher accurate molecular recognition ability. Here, a simple and effective modification strategy is proposed for the incorporation of Cu2O and the two-dimensional (2D) material MoS2via a facile hydrothermal and wet chemical method. The sensing characteristics of a series of (p–p) Cu2O/MoS2 nanohybrids towards ammonia (NH3) are systematically investigated. The nanohybrid based sensor shows an excellent NH3 sensing performance compared with the pristine Cu2O nanoparticles in the 25–325 °C temperature range. Under an optimal low-operating temperature of 75 °C, the sensing performance for 20–100 ppm NH3 is studied and the sensing response of the Cu2O/MoS2 sensor (at ∼872%) with an optimized composition for 100 ppm NH3 is increased more than 8 times compared with the pristine Cu2O (∼103%) under the same conditions. Furthermore, excellent selectivity for NH3 is observed against other interferent gases. The Cu2O/MoS2 sensor belongs to a surface-controlled type and the enhanced sensing property of nanohybrid benefits from the superimposed effect of the p–p heterojunction formation and the elevated specific surface area at the interface between Cu2O and MoS2. [ABSTRACT FROM AUTHOR]

It is still challenging to control the crystallization and morphologies of molecular crystal nanostructures with excellent photocatalytic activities. In this study, single-crystalline melem (C6N10H6) nanorods (MNRs) were prepared by a facile thermal polymerization route under a flowing argon atmosphere. Compared with the bulk melem counterpart and g-C3N4, the MNRs exhibited substantially improved efficiency and stability towards the photodegradation of diverse organic pollutants including methyl orange, rhodamine B, and methylene blue. Moreover, the average photocatalytic hydrogen evolution rate of MNRs was about 2.6 folds higher than that of bulk melem under the same conditions. The enhanced photocatalytic redox performance of MNRs arises from the single-crystal nature and novel one-dimensional (1D) nanorod morphology, contributing to elevated conduction band potentials and promoting charge transport dynamics. This study not only reports single-crystalline melem 1D nanostructures as novel highly efficient and stable molecular-crystal photocatalysts, but also reveals the important roles of synergetic tuning of charge potentials and dynamics in enhancing the photocatalytic activity of molecular-crystal photocatalysts. [ABSTRACT FROM AUTHOR]