Vanadium disulfide (VS2), a typical layered transition‐metal dichalcogenide, has drawn extensive attention in energy storage devices, catalysts as well as sensors due to its intriguing electronic peculiarities, whereas its chemiresistive gas sensing properties have seldom been investigated. In this contribution, first the ammonia sensing properties of VS2 nanosheets (NSs)‐based chemiresistive gas sensor are reported. VS2 NSs are synthesized through facile liquid‐phase exfoliation, and their crystal structure, micromorphology, and elemental component are characterized. Density functional theory calculation has revealed that VS2 (100) is highly affinitive to ammonia molecule, and sufficient electron transfers from ammonia to VS2, which implies VS2 NSs possess high potential for ammonia sensing. The computational results are verified by gas sensing measurement that the resistance of VS2 NSs remarkably increases upon injecting ammonia gas at low working temperature of 40 °C. Additionally, the VS2 NSs exhibit superb selectivity to ammonia. The probable mechanism for ammonia sensing can be that ammonia molecule absorbed at edge sites of VS2 NSs transfers electron to p‐type VS2 NSs, reduces hole concentration in the NSs, and thus leads to resistance enhancement of VS2 NSs.
Two‐dimensional (2D) materials have aroused widespread interest due to the high potential in modern photoelectronics. The strategy for improving the stability of 2D materials in the air, reinforcing formation, and transport of photoexcited carriers would open up promising routes toward flexible facilities. In this paper, surface engineering is executed on 2D InSe by decorating Au species for a lower bandgap allowing for efficient sunlight harvesting and decreased barrier with the substrate for improved electron transport. Moreover, hot electrons produced by Au nanoparticles under light irradiation pour into InSe for boosting photocurrent. Au nanoparticles also serve as conducting bridges in InSe−Au photoanode, where the contact resistance is two orders of magnitude lower than that of InSe electrode. Compared with InSe and other 2D counterparts, InSe−Au flexible photoelectrochemical detectors behave with outstanding performances under sunlight irradiation, including responsibility 55.4 µA W−1, detectivity 4.18 × 109 Jones. Importantly, the working electrode shows excellent ON/OFF switching stability after bending for 5000 times (3 months of storage in the air). This surface engineering provides a general strategy to tailor 2D materials for wearable photoelectronic devices in the future.
Electrochemical dopamine (DA) sensors become important for early diagnosis of psychiatric disorders like schizophrenia and Parkinson's disease due to their fast response, simplicity, and portability. However, traditional electrode modification materials such as noble metals and metal oxides have shortcomings such as high cost, low conductivity, or limited catalytic performance. Two-dimensional sulfide materials contribute to the smooth electrode reaction because of their ultra-high specific superficial area and favorable electrocatalysis properties, however, their low carrier mobility and poor electroconductibility limit the detection signal. In this paper, Co-doped FePS3 nanosheets were employed for DA detection for the first time. Fe0.9Co0.1PS3 nanosheets exhibited a detection limit of 120 nM, a linear range 0.25-100 μM and 120-500 μM, and possessed high recovery and reproducible stability when applied to human serum samples. Furthermore, according to the in-situ XPS characterization, S atoms located on the outmost layer of Fe0.9Co0.1PS3 nanosheets could be combined with the phenolic hydroxyl oxygen of DA, which makes electrode reaction from DA to dopamine quinone easier. Co-doping can further enhance the above effect, and increase the carrier mobility of FePS3 nanosheets. This work demonstrates that electrochemical sensors based on metal phosphorus trisulfide materials have tremendous potential for future application in mental disorder diagnosis
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