Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) have emerged as attractive platforms in next-generation nanoelectronics and optoelectronics for reducing device sizes down ...to a 10 nm scale. To achieve this, the controlled synthesis of wafer-scale single-crystal TMDs with high crystallinity has been a continuous pursuit. However, previous efforts to epitaxially grow TMD films on insulating substrates (e.g., mica and sapphire) failed to eliminate the evolution of antiparallel domains and twin boundaries, leading to the formation of polycrystalline films. Herein, we report the epitaxial growth of wafer-scale single-crystal MoS2 monolayers on vicinal Au(111) thin films, as obtained by melting and resolidifying commercial Au foils. The unidirectional alignment and seamless stitching of the MoS2 domains were comprehensively demonstrated using atomic- to centimeter-scale characterization techniques. By utilizing onsite scanning tunneling microscope characterizations combined with first-principles calculations, it was revealed that the nucleation of MoS2 monolayer is dominantly guided by the steps on Au(111), which leads to highly oriented growth of MoS2 along the ⟨110⟩ step edges. This work, thereby, makes a significant step toward the practical applications of MoS2 monolayers and the large-scale integration of 2D electronics.
We propose a technique of Raman spectroscopy to characterize the excitonic nature and to evaluate the relative contribution of the two kinds of electron/exciton–phonon interactions that are observed ...in two-dimensional transition-metal dichalcogenides (TMDCs). In the TMDCs, the electron/exciton–phonon interactions mainly originate from the deformation potential (DP) or the Fröhlich interaction (FI) which give the mutually different Raman tensors. Using a circularly polarized light, the relative proportion of the DP and the FI can be defined by the ratio of helicity-polarized intensity that is observed by MoS2. By this analysis, we show that the excitonic FI interaction gradually increases with decreasing temperature, contributes equally to DP at ∼230 K, and dominates at lower temperatures. The excitonic effect in the Raman spectra is confirmed by modulating the dielectric environment for the exciton and by changing the laser power.
Two-dimensional (2D) semiconductors, especially transition metal dichalcogenides (TMDs), have been envisioned as promising candidates in extending Moore's law. To achieve this, the controllable ...growth of wafer-scale TMDs single crystals or periodic single-crystal patterns are fundamental issues. Herein, we present a universal route for synthesizing arrays of unidirectionally orientated monolayer TMDs ribbons (e.g., MoS
, WS
, MoSe
, WSe
, MoS
Se
), by using the step edges of high-miller-index Au facets as templates. Density functional theory calculations regarding the growth kinetics of specific edges have been performed to reveal the morphological transition from triangular domains to patterned ribbons. More intriguingly, we find that, the uniformly aligned TMDs ribbons can merge into single-crystal films through a one-dimensional edge epitaxial growth mode. This work hereby puts forward an alternative pathway for the direct synthesis of inch-scale uniform monolayer TMDs single-crystals or patterned ribbons, which should promote their applications as channel materials in high-performance electronics or other fields.
Palladium diselenide (PdSe2) is an emerging 2D layered material with anisotropic optical/electrical properties, extra‐high carrier mobility, excellent air stability, etc. So far, ultrathin PdSe2 is ...mainly achieved via mechanical exfoliation from its bulk counterpart, and the direct synthesis is still challenging. Herein, the synthesis of ultrathin 2D PdSe2 on conductive Au foil substrates via a facile chemical vapor deposition route is reported. Intriguingly, an anisotropic growth behavior is detected from the evolution of ribboned flakes with large length/width ratios, which is well explained from the orthorhombic symmetry of PdSe2. A unique even‐layered growth mode from 2 to 20 layers is also confirmed by the perfect combination of onsite scanning tunneling microscopy characterizations, through deliberately scratching the flake edge to expose both even and odd layers. This even‐layered, ribboned 2D material is expected to serve as a perfect platform for exploring unique physical properties, and for developing high‐performance electronic and optoelectronic devices.
Ultrathin 2D PdSe2 is synthesized on novel Au foil substrates via a facile chemical vapor deposition route. An anisotropic growth behavior is detected from the evolution of ribboned flakes, which arises from the orthorhombic symmetry of PdSe2 and the unique metallic substrate of Au. A unique even‐layered growth mode is also confirmed by onsite scanning tunneling microscopy characterizations.
Manipulating liquid flow over open solid substrate at nanoscale is important for printing, sensing, and energy devices. The predominant methods of liquid maneuvering usually involve complicated ...surface fabrications, while recent attempts employing external stimuli face difficulties in attaining nanoscale flow control. Here we report a largely unexplored ion beam induced film wetting (IBFW) technology for open surface nanofluidics. Local electrostatic forces, which are generated by the unique charging effect of Helium focused ion beam (HFIB), induce precursor film of ionic liquid and the disjoining pressure propels and stabilizes the nanofilm with desired patterns. The IBFW technique eliminates the complicated surface fabrication procedures to achieve nanoscale flow in a controllable and rewritable manner. By combining with electrochemical deposition, various solid materials with desired patterns can be produced.
Rhenium diselenide (ReSe2) is a unique transition-metal dichalcogenide (TMDC) possessing distorted 1T structure with a triclinic symmetry, strong in-plane anisotropy, and promising applications in ...optoelectronics and energy-related fields. So far, the structural and physical properties of ReSe2 are mainly uncovered by transmission electron microscopy and spectroscopy characterizations. Herein, by combining scanning tunneling microscopy and spectroscopy (STM and STS) with first-principles calculations, we accomplish the on-site atomic-scale identification of the top four non-identical Se atoms in a unit cell of the anisotropic monolayer ReSe2 on the Au substrate. According to STS and photoluminescence results, we also determine the quasiparticle and optical band gaps as well as the exciton binding energy of monolayer ReSe2. In particular, we detect a perfect lattice coherence and an invariable band gap across the mirror-symmetric grain boundaries in monolayer and bilayer ReSe2, which considerably differ from the traditional isotropic TMDCs featured with defect structures and additional states inside the band gap. Such essential findings should deepen our understanding of the intrinsic properties of two-dimensional anisotropic materials and provide fundamental references for their applications in related fields.
Acidithiobacillus caldus
plays an important role in bioleaching of low-grade metal ore. It can promote the release of heavy metals in mining-associated habitats and survive in high concentrations of ...heavy metals. Functions of glutathione reductase (GR) in cell defense against reactive oxygen species caused by heavy metals have been elucidated in some eukaryotic cells and bacteria; however, no information is available in
A. caldus
. In this research, the methods of bioinformatics, gene expression, GR activity assays were used to detect and characterize the glutathione reductase gene from the
A. caldus
MTH-04 strain. Then,
A. caldus gr
knockout mutant and
gr
overexpression strain were constructed, and the heavy metal tolerant properties and transcriptional levels of ROS related genes of them were compared to study the function of GR. The results showed that, a putative
gr
gene F0726_RS04210 was detected in the genome of
A. caldus
MTH-04. The purified recombinant protein of F0726_RS04210 showed remarkable GR activity at optimal pH 7.0 and 30°C using
in vitro
assay. The evolutionary relationship of GR from
A. caldus
MTH-04 was close to that from
Escherichia coli
K12. Gene knockout or overexpression of
gr
in
A. caldus
did not affect the growth rate on S
0
medium, suggesting that GR did not play a key role in the activation of sulfur. Deletion of
gr
resulted in increased sensitivity to heavy metals (Cu
2+
and Zn
2+
) in
A. caldus
, and the
gr
overexpression strain showed enhanced tolerance to heavy metals. Furthermore, transcription analysis also revealed strong correlations between GR and the antioxidant pathway. The above results suggest that GR can play an important role in heavy metal tolerance in
A. caldus
.
Purpose. This study mainly analyzes the efficacy of 0.01% atropine eye drops (low-dose atropine (LDA)) combined with virtual reality (VR)-based binocular visual function (BVF) balance training in the ...prevention and control of juvenile myopia. Methods. One hundred and thirty-six juvenile myopia patients admitted between November 2018 to November 2021 were selected, including 76 cases (research group) receiving LDA + VR-based BVF balance training and 60 cases (control group) treated by LDA intervention alone. Visual acuity (VA; naked vision), ocular parameters (pupil diameter (PD), axial length (AXL), and diopter), intraocular pressure (IOP), accommodation facility, clinical efficacy, and incidence of adverse reactions were observed, compared, and analyzed in both groups. Results. After analysis, it was found that the research group showed significantly higher naked vision and PD while statistically lower D after intervention than the corresponding preinterventional parameters than the control group. While AXL showed no statistical difference between the groups and within groups. The IOP also differed insignificantly between groups, but the post-treatment accommodation facility was better in the research group compared with the baseline (before treatment) and control group. In terms of curative effects, an obviously higher total effective rate was determined in the research group. In addition, the two groups showed no significant difference in the incidence of adverse reactions. Conclusions. LDA + VR-based BVF balance training deserves clinical popularization, as it can prevent and control myopia among teenagers, with better adjusting effects on eye function and certain safety.
China is experiencing an aging population, leading to a significant demand for "Internet + nursing services" tailored for elderly individuals. However, there are many risk problems in the process of ...nurse service, which hinder the development of the service, and a scale is needed to assess the risk problems faced by nurses in "Internet + nursing services" for the elderly.
The purpose of this study is to develop an assessment scale for risk factors and outcomes related to nurses' involvement in the "Internet + Nursing Service" for the elderly and to assess its reliability and validity.
Based on literature analysis, focus group, the Delphi method, and a presurvey, we designed an initial scale. The initial scale comprised two sections: risk factors and risk outcomes for nurses. In January and February of 2023, nurses engaged in "Internet + nursing services" for the elderly in Shanxi Province were chosen through a convenience sampling technique for a questionnaire survey. Subsequently, item analysis and exploratory factor analysis were employed to refine and develop a test version of the scale further. A follow-up questionnaire survey was carried out in March and April 2023 using a similar approach. The reliability and validity of the scale were assessed through confirmatory factor analysis, culminating in the formation of the final scale.
The initial survey yielded 244 valid responses. The cumulative variance contributions of the two segments from the exploratory factor analysis were 84.584% and 90.089%, respectively. A subsequent survey garnered 220 valid responses. The confirmatory factor analysis results indicated: χ2/df = 2.086, comparative fit index (CFI) = 0.918, normative fit index (NLI) = 0.855, root mean square of residuals (RMR) = 0.045, and root mean square of error of approximation (RMSEA) = 0.070. These results demonstrate good structural, convergent, and discriminant validity. The content validity index at the item level (I-CVI) ranged between 0.875 and 1.000, while the content validity index at the scale level (S-CVI/Ave) was 0.941. Cronbach's alpha coefficient for the entire scale stood at 0.970. Moreover, the scale exhibited a split-half reliability of 0.876 and a retest reliability of 0.980 (p < 0.01).
The risk factors and risk outcomes associated with nurses involved in "Internet + nursing services" for elderly individuals, as developed in this study, demonstrate strong reliability and validity. They are well suited to the Chinese national context.
Gentiooligosaccharides (GnOS) are a kind of oligosaccharide formed by glucose with β-1-6 glycosidic bonds, which has become a new type of functional oligosaccharide for its unique refreshing bitter ...taste and valuable probiotic effects. However, the research on the enzymatic preparation of GnOS is not thorough enough. In this study, a GH1 thermophilic β-glucosidase from
sp. KOL6 was used as a biocatalyst for the synthesis of GnOS. TsBgl1 exhibited excellent thermophilic and thermostable properties by possessing a melting temperature of 101.5 °C and reacting at 80-90 °C efficiently. Its half-life at 90 °C was approximately 5 h, suggesting its high heat resistance as well. TsBgl1 also showed excellent glucose tolerance with an inhibition constant (
) of 1720 mM and was stimulated in the presence of 0-900 mM glucose. TsBgl1 showed the highest hydrolytic activity on laminaribiose (Glc-β-1,3-Glc), but mainly synthetized gentiobiose (Glc-β-1,6-Glc) during transglycosylation. By optimizing the reaction conditions and substrate concentration, the highest yield of GnOS synthesized by TsBgl1 reached 144.3 g·L
when 1000 g·L
glucose was used as a substrate, which was higher than the highest yield ever reported. The thermophilic and thermostable properties of TsBgl1 were considered to be significant advantages in the industrial production of GnOS, where long periods of high-temperature reactions are required. This study was expected to provide an excellent candidate enzyme for industrial production of GnOS and also provide a reference for studying the transglycosylation of GH1 β-glucosidases.
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