Strong two‐photon absorption (TPA) in monolayer MoS2 is demonstrated in contrast to saturable absorption (SA) in multilayer MoS2 under the excitation of femtosecond laser pulses in the near‐infrared region. MoS2 in the forms of monolayer single crystal and multilayer triangular islands are grown on either quartz or SiO2/Si by employing the seeding method through chemical vapor deposition. The nonlinear transmission measurements reveal that monolayer MoS2 possesses a nonsaturation TPA coefficient as high as ∼(7.62 ±0.15) ×103 cm/GW, larger than that of conventional semiconductors by a factor of 103. As a result of TPA, two‐photon pumped frequency upconverted luminescence is observed directly in the monolayer MoS2. For the multilayer MoS2, the SA response is demonstrated with the ratio of the excited‐state absorption cross section to ground‐state cross section of ∼0.18. In addition, the laser damage threshold of the monolayer MoS2 is ∼97 GW/cm2, larger than that of the multilayer MoS2 of ∼78 GW/cm2.
MoS2 nanoflowers with expanded interlayer spacing of the (002) plane were synthesized and used as high‐performance anode in Na‐ion batteries. By controlling the cut‐off voltage to the range of 0.4–3 V, an intercalation mechanism rather than a conversion reaction is taking place. The MoS2 nanoflower electrode shows high discharge capacities of 350 mAh g?1 at 0.05 A g?1, 300 mAh g?1 at 1 A g?1, and 195 mAh g?1 at 10 A g?1. An initial capacity increase with cycling is caused by peeling off MoS2 layers, which produces more active sites for Na+ storage. The stripping of MoS2 layers occurring in charge/discharge cycling contributes to the enhanced kinetics and low energy barrier for the intercalation of Na+ ions. The electrochemical reaction is mainly controlled by the capacitive process, which facilitates the high‐rate capability. Therefore, MoS2 nanoflowers with expanded interlayers hold promise for rechargeable Na‐ion batteries. 相似文献
Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation‐assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. 相似文献
Hierarchical MoS2 shells supported on carbon spheres (denoted as C@MoS2) have been synthesized through a one‐step hydrothermal method. The obtained hierarchical C@MoS2 microspheres simultaneously integrate the structural and compositional design rationales for high‐energy electrode materials based on two‐dimensional (2D) nanosheets. When evaluated as an anode material for lithium‐ion batteries (LIBs), the hierarchical C@MoS2 microspheres manifest high specific capacity, enhanced cycling stability and good rate capability. 相似文献
Nanosized semiconductors (semiconductor clusters) have the potential to revolutionize the fields of photooxidation and photocatalysis through the combined effects of quantum confinement and their unique surface morphologies. Photocatalytic oxidation as applied to environmental remediation (i.e., detoxification of chemical wastes), green/sustainable chemistry, as well as alternative energy paths (i.e., splitting of H2O to produce H2) has already experienced improvements in activity, efficiency, and stability through the use of semiconductor nanoclusters based on materials such as TiO2, MoS2, WS2, MoSe2, FeS2, and SnO2. Issues such as improved control of size and surface chemistry play an important role in the success of these semiconductor nanocatalysts. This review explores the effect of advances in the fields of nanoscience and photocatalysis for current and future applications. 相似文献
Most recently, much attention has been devoted to photocatalytic materials that may help to solve the global energy crisis and may provide environmental protection. Herein, novel cocatalysts based on few layered MoS2 and TiO2 nanomaterials have been designed by growing MoS2 nanosheets on the surface of TiO2 nanospheres through a facile hydrothermal method. The method allows the formation of TiO2/MoS2 core–shell heterostructures of uniform morphologies and stable structure and provides a good control over shell thickness. The mechanism that forms these heterostructures is discussed in detail. In addition, as cocatalyst, MoS2 nanosheets can enlarge the light harvesting window to include visible light and improve the photocatalytic ability of TiO2. Using Rhodamine B as the model, the resultant heterostructure is demonstrated to possess excellent and stable photocatalytic activity in the degradation of organic pollutants under visible light illumination. The TiO2/MoS2 heterostructures possess this catalytic activity due to their large surface area and their excellent interface for separating holes and electrons. Therefore, this novel heterostructure nanomaterials possess potential applications in water treatment, degradation of dye pollutants, and environmental cleaning. 相似文献
Sulfur vacancy on an MoS2 basal plane plays a crucial role in device performance and catalytic activity; thus, an understanding of the electronic states of sulfur vacancies is still an important issue. We investigate the electronic states on an MoS2 basal plane by ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory calculations while heating the system in hydrogen. The AP-XPS results show a decrease in the intensity ratio of S 2p to Mo 3d, indicating that sulfur vacancies are formed. Furthermore, low-energy components are observed in Mo 3d and S 2p spectra. To understand the changes in the electronic states induced by sulfur vacancy formation at the atomic scale, we calculate the core-level binding energies for the model vacancy surfaces. The calculated shifts for Mo 3d and S 2p with the formation of sulfur vacancy are consistent with the experimentally observed binding energy shifts. Mulliken charge analysis indicates that this is caused by an increase in the electronic density associated with the Mo and S atoms around the sulfur vacancy as compared to the pristine surface. The present investigation provides a guideline for sulfur vacancy engineering. 相似文献
Transition metal dichalcogenides (TMDC) are important representatives in the emerging field of two‐dimensional materials. At present their combination with molecular films is discussed as it enables the realization of van der Waals bound organic/inorganic hybrids which are of interest in future device architectures. Here, we discuss the potential use of molybdenum disulfide (MoS2) as supporting substrate for the growth of well‐defined, crystalline organic adlayers. By this means, hybrid systems between the TMDC surface and organic compounds can be prepared, allowing for the profound investigation of mutual optical and electronic coupling mechanisms. As model system, we choose pentacene and perfluoropentacene as prototypical organic semiconductors and analyze their film formation on MoS2(001) surfaces. In both cases, we observe smooth, crystalline film growth in lying molecular configuration, hence enabling the preparation of well‐defined hybrid systems. By contrast, on defective MoS2 surfaces both materials adopt an upright molecular orientation and exhibit distinctly different film morphologies. This emphasizes the importance of highly ordered TMDC surfaces with low defect density for the fabrication of well‐defined hybrid systems. 相似文献