WSe2--a layered semiconductor that can be exfoliated into atomically thin two-dimensional sheets--offers promising characteristics for application in solar energy conversion. However, the lack of ...controllable, cost-effective methods to scalably fabricate homogeneous thin films currently limits practical application. Here we present a technique to prepare controlled thin films of 2D WSe2 from dispersions of solvent-exfoliated few-layer flakes. Flake self-assembly at a liquid/liquid interface (formed exceptionally from two non-solvents for WSe2) followed by substrate transfer affords large-area thin films with superior 2D flake alignment compared with traditional (liquid/air) self-assembly techniques. We further demonstrate, for the first time, solar-to-hydrogen conversion from solution-processed WSe2 thin films. Bare photoelectrodes with a thickness of ca. 25 nm exhibit sustained p-type photocurrent under simulated solar illumination, and up to 1.0 mA cm(-2) at 0 V versus reversible hydrogen electrode with an added water reduction catalyst (Pt). The importance of the self-assembled morphology is established by photoelectrochemical and conductivity measurements.
Few-atomic-layer nanoflakes of liquid-phase exfoliated semiconducting transition metal dichalcogenides (TMDs) hold promise for large-area, high-performance, low-cost solar energy conversion, but ...their performance is limited by recombination at defect sites. Herein, we examine the role of defects on the performance of WSe2 thin film photocathodes for solar H2 production by applying two separate treatments, a pre-exfoliation annealing and a post-deposition surfactant attachment, designed to target intraflake and edge defects, respectively. Analysis by TEM, XRD, XPS, photoluminescence, and impedance spectroscopy are used to characterize the effects of the treatments and photoelectrochemical (PEC) measurements using an optimized Pt–Cu cocatalyst (found to offer improved robustness compared to Pt) are used to quantify the performance of photocathodes (ca. 11 nm thick) consisting of 100–1000 nm nanoflakes. Surfactant treatment results in an increased photocurrent attributed to edge site passivation. The pre-annealing treatment alone, while clearly altering the crystallinity of pre-exfoliated powders, does not significantly affect the photocurrent. However, applying both defect treatments affords a considerable improvement that represents a new benchmark for the performance of solution-processed WSe2: solar photocurrents for H2 evolution up to 4.0 mA cm–2 and internal quantum efficiency over 60% (740 nm illumination). These results also show that charge recombination at flake edges dominates performance in bare TMD nanoflakes, but when the edge defects are passivated, internal defects become important and can be reduced by pre-annealing.
Lithium stripping is a crucial process coupled with lithium deposition during the cycling of Li metal batteries. Lithium deposition has been widely studied, whereas stripping as a subsurface process ...has rarely been investigated. Here we reveal the fundamental mechanism of stripping on lithium by visualizing the interface between stripped lithium and the solid electrolyte interphase (SEI). We observed nanovoids formed between lithium and the SEI layer after stripping, which are attributed to the accumulation of lithium metal vacancies. High-rate dissolution of lithium causes vigorous growth and subsequent aggregation of voids, followed by the collapse of the SEI layer, i.e., pitting. We systematically measured the lithium polarization behavior during stripping and find that the lithium cation diffusion through the SEI layer is the rate-determining step. Nonuniform sites on typical lithium surfaces, such as grain boundaries and slip lines, greatly accelerated the local dissolution of lithium. The deeper understanding of this buried interface stripping process provides beneficial clues for future lithium anode and electrolyte design.
Transient receptor potential (TRP) channels are predominantly distributed in both somatic and visceral sensory nervous systems and play a crucial role in sensory transduction. As the largest visceral ...organ system, the gastrointestinal (GI) tract frequently accommodates external inputs, which stimulate sensory nerves to initiate and coordinate sensory and motor functions in order to digest and absorb nutrients. Meanwhile, the sensory nerves in the GI tract are also able to detect potential tissue damage by responding to noxious irritants. This nocifensive function is mediated through specific ion channels and receptors expressed in a subpopulation of spinal and vagal afferent nerve called nociceptor. In the last 18 years, our understanding of TRP channel expression and function in GI sensory nervous system has been continuously improved. In this review, we focus on the expressions and functions of TRPV1, TRPA1, and TRPM8 in primary extrinsic afferent nerves innervated in the esophagus, stomach, intestine, and colon and briefly discuss their potential roles in relevant GI disorders.
In order to accurately evaluate the safety risk degree of lifting operations and improve the safety control level of lifting operations, firstly, Work Breakdown Structure (WBS) is used to decompose ...the construction process of lifting operations, Risk Breakdown Structure (RBS) is used to decompose the safety risk, 16 safety risk factors of lifting operations are identified, and the risk evaluation system is constructed. Then, the safety risk assessment model of lifting operations is constructed by integrating risk coupling theory, joint ordered weighting operators, and an interaction matrix to identify key risk factors and safety risk levels. Finally, taking the lifting operation construction project of Yangfanggou Hydropower Station as an example, the evaluation index system and method are applied. The results show that the high-risk safety risks of the lifting operation construction of the project are: 'Low safety awareness causes workers to operate illegally X
', 'Operation error caused by illegal command X
', 'Workers' risky work caused by low safety awareness X
', 'Edge, high and climbing operation protection is not in place X
', and 'Improper binding of components caused by workers' illegal operation X
'. The construction of the lifting operation poses a significant risk level, and the evaluation results are consistent with the actual situation. The rationality of the evaluation system and model constructed in this paper can provide a reference for the safety management and control of the construction site of the lifting operation and the safety of the lifting operation.
The solvent-assisted exfoliation of transition metal dichalchogenides (TMDs) is a promising method for preparing scalable quantities of two-dimensional nanomaterials dispersed in a liquid phase. ...However, low concentrations and the restacking/aggregation of TMD layers remain challenges to the solution based preparation of large-area electronic devices. Here we present advances in the exfoliation and solution processing of 2D MoS2 that are subsequently leveraged to prepare and electronically probe homogeneous multiflake thin-film devices. We report that sonopolymer, formed when using 1,2-dichlorobenzene (DCB) as a solvent, plays a critical role in affording stable dispersions (up to 0.5 mg mL–1) of few-layer MoS2 flakes in the 2H phase after only 6 h of low-power sonication. After removing the sonopolymer using a washing procedure, alkyl-trichlorosilane surfactants were used to prevent the restacking of 2D MoS2 layers and create stable dispersions with concentrations as high as 85 mg mL–1. In spin-coated multiflake thin films as thin as 20 nm, electron transport parallel to the substrate was quantifiable over channel lengths of 50 μm owing to the homogeneous film formation. By further varying the alkyl-trichlorosilane chain length we show that a trade-off between dispersibility (film homogeneity) and electronic insulation from the surfactant leads to a maximum (multiflake) electron mobility of 0.02 cm2 V–1 s–1 using hexyl-trichlorosilane modified MoS2 in the direction perpendicular to the substrate as measured by space-charge limited current devices.
T helper (Th) cells have received extensive attention owing to their indispensable roles in anti-tumor immune responses. Th1 and Th2 cells are two key subsets of Th cells that exist in relative ...equilibrium through the secretion of cytokines that suppress their respective immune response. When the type of cytokine in the tumor microenvironment is altered, this equilibrium may be disrupted, leading to a shift from Th1 to Th2 immune response. Th1/Th2 imbalance is one of the decisive factors in the development of malignant tumors. Therefore, focusing on the balance of Th1/Th2 anti-tumor immune responses may enable future breakthroughs in cancer immunotherapy. Polysaccharides can regulate the imbalance between Th1 and Th2 cells and their characteristic cytokine profiles, thereby improving the tumor immune microenvironment. To our knowledge, this study is the most comprehensive assessment of the regulation of the tumor Th1/Th2 balance by polysaccharides. Herein, we systematically summarized the intrinsic molecular mechanisms of polysaccharides in the regulation of Th1 and Th2 cells to provide a new perspective and potential target drugs for improved anti-tumor immunity and delayed tumor progression.
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•Th1/Th2 balance is an important molecular target in cancer.•Polysaccharides significantly improve the tumor immunosuppressive microenvironment.•Polysaccharides can regulate Th1/Th2 balance as an adjuvant for tumor therapy.
A conjugated polymer known for high stability (polybenzimidazobenzophenanthroline, coded as BBL) is examined as a photoanode for direct solar water oxidation. In aqueous electrolyte with a ...sacrificial hole acceptor (SO3 2–), photoelectrodes show a morphology-dependent performance. Films prepared by a dispersion-spray method with a nanostructured surface (feature size of ∼20 nm) gave photocurrents up to 0.23 ± 0.02 mA cm–2 at 1.23 VRHE under standard simulated solar illumination. Electrochemical impedance spectroscopy reveals a constant flat-band potential over a wide pH range at +0.31 VNHE. The solar water oxidation photocurrent with bare BBL electrodes is found to increase with increasing pH, and no evidence of semiconductor oxidation was observed over a 30 min testing time. Characterization of the photo-oxidation reaction suggests H2O2 or •OH production with the bare film, while functionalization of the interface with 1 nm of TiO2 followed by a nickel–cobalt catalyst gave solar photocurrents of 20–30 μA cm–2, corresponding with O2 evolution. Limitations to photocurrent production are discussed.
We investigated the optimal operational conditions for utilizing a broadband supercontinuum (SC) source in a portable 800 nm spectral-domain (SD) endoscopic OCT system to enable high resolution, ...high-sensitivity, and high-speed imaging in vivo. A SC source with a 3-dB bandwidth of ∼246 nm was employed to obtain an axial resolution of ∼2.7 μm (in air) and an optimal detection sensitivity of ∼-107 dB with an imaging speed up to 35 frames/s (at 70 k A-scans/s). The performance of the SC-based SD-OCT endoscopy system was demonstrated by imaging guinea pig esophagus in vivo, achieving image quality comparable to that acquired with a broadband home-built Ti:sapphire laser.
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