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In situ probing of electron transfer at the dynamic MoS2/graphene–water interface for modulating boundary slip
Nano Research
Published: 08 May 2024
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The boundary slip condition is pivotal for nanoscale fluid motion. Recent research has primarily focused on simulating the interaction mechanism between the electronic structure of two-dimensional materials and slip of water at the nanoscale, raising the possibility for ultralow friction flow of water at the nanoscale. However, experimentally elucidating electronic interactions at the dynamic solid–liquid interface to control boundary slip poses a significant challenge. In this study, the crucial role of electron structures at the dynamic solid–liquid interface in regulating slip length was revealed. Notably, the slip length of water on the molybdenum disulfide/graphene (MoS2/G) heterostructure (100.9 ± 3.6 nm) significantly exceeded that of either graphene (27.7 ± 2.2 nm) or MoS2 (5.7 ± 3.1 nm) alone. It was also analyzed how electron transfer significantly affected interface interactions. Excess electrons played a crucial role in determining the type and proportion of excitons at both MoS2–water and MoS2/G–water interfaces. Additionally, by applying voltage, distinct photoluminescence (PL) responses at static and dynamic interfaces were discovered, achieving a 5-fold modulation in PL intensity and a 2-fold modulation in the trion to exciton intensity ratio. More electrons transfer from the top graphene to the bottom MoS2 at the MoS2/G–water interface, reducing surface charge density. Thus, the reduction of electrostatic interactions between the solid and water leads to an increased slip length of water on the MoS2/G heterostructure. The process aids in comprehending the origin of frictional resistance at the subatomic scale. This work establishes a foundation for actively controlling and designing of fluid transport at the nanoscale.

Open Access Research Article Issue
Rapid surface texturing to achieve robust superhydrophobicity, controllable droplet impact, and anti-frosting performances
Friction 2024, 12 (2): 291-304
Published: 29 November 2023
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Robust superhydrophobic surfaces with excellent capacities of repelling water and anti-frosting are of importance for many mechanical components. In this work, wear-resistant superhydrophobic surfaces were fabricated by curing a mixture of polyurethane acrylate (PUA) coating and 1H,1H,2H,2H-Perfluorodecyltrichlorosilane (HFTCS) on titanium alloy (TC4) surfaces decorated with micropillars pattern, thus, composite functional surfaces with PUA coating in the valleys around the micropillars pattern of TC4 were achieved. Apparent contact angle on fabricated surfaces could reach 167°. Influences of the geometric parameters of micropillars pattern on the apparent contact angle were investigated, and the corresponding wear-resistant property was compared. Droplet impact and anti-frosting performances on the prepared surfaces were highlighted. An optimized design of surface texture with robust superhydrophobicity, controllable droplet impact, and anti-frosting performances was proposed. This design principle is of promising prospects for fabricating superhydrophobic surfaces in traditional mechanical systems.

Open Access Review Article Issue
The mechanisms and applications of friction energy dissipation
Friction 2023, 11 (6): 839-864
Published: 26 August 2022
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Downloads:135

About 30% of the world’s primary energy consumption is in friction. The economic losses caused by friction energy dissipation and wear account for about 2%–7% of its gross domestic product (GDP) for different countries every year. The key to reducing energy consumption is to control the way of energy dissipation in the friction process. However, due to many various factors affecting friction and the lack of efficient detection methods, the energy dissipation mechanism in friction is still a challenging problem. Here, we firstly introduce the classical microscopic mechanism of friction energy dissipation, including phonon dissipation, electron dissipation, and non-contact friction energy dissipation. Then, we attempt to summarize the ultrafast friction energy dissipation and introduce the high-resolution friction energy dissipation detection system, since the origin of friction energy dissipation is essentially related to the ultrafast dynamics of excited electrons and phonons. Finally, the application of friction energy dissipation in representative high-end equipment is discussed, and the potential economic saving is predicted.

Research Article Issue
Rapid thin-layer WS2 detection based on monochromatic illumination photographs
Nano Research 2021, 14 (3): 840-845
Published: 01 March 2021
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The thickness of two-dimensional (2D) nanomaterials shows a significant effect on their optical and electrical properties. Therefore, a rapid and automatic detection technology of 2D nanomaterials with desired layer-number is required to extend their practical application in optoelectronic devices. In this paper, an image recognition technology was proposed for rapid and reliable identification of thin-layer WS2 samples, which combining a layer-thickness identification criterion and a novel image segmentation algorithm. The criterion stemmed from optical contrast study of monochromatic illumination photographs, and the algorithm was based on Canny operator and edge connection iteration. This optical identification method can seek out thin-layer WS2 samples on complex surfaces, which provides a promising approach for automatic search of thin-layer nanomaterials.

Research Article Issue
Layer-dependent signatures for exciton dynamics in monolayer and multilayer WSe2 revealed by fluorescence lifetime imaging measurement
Nano Research 2020, 13 (3): 661-666
Published: 12 February 2020
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Downloads:25

Two-dimensional (2D) transition-metal dichalcogenide (TMD) materials have aroused noticeable interest due to their distinguished electronic and optical properties. However, little is known about their complex exciton properties together with the exciton dynamics process which have been expected to influence the performance of optoelectronic devices. The process of fluorescence can well reveal the process of exciton transition after excitation. In this work, the room-temperature layer-dependent exciton dynamics properties in layered WSe2 are investigated by the fluorescence lifetime imaging microscopy (FLIM) for the first time. This paper focuses on two mainly kinds of excitons including the direct transition neutral excitons and trions. Compared with the lifetime of neutral excitons (< 0.3 ns within four-layer), trions possess a longer lifetime (~ 6.6 ns within four-layer) which increases with the number of layers. We attribute the longer-lived lifetime to the increasing number of trions as well as the varieties of trion configurations in thicker WSe2. Besides, the whole average lifetime increases over 10% when WSe2 flakes added up from monolayer to four-layer. This paper provides a novel tuneable layer-dependent method to control the exciton dynamics process and finds a relatively longer transition lifetime of trions at room temperature, enabling to investigate in the charge transport in TMD-based optoelectronics devices in the future.

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