Nanostructural modification and chemical composition tuning are paramount to developing effective non-noble hydrogen evolution reaction (HER) catalysts for water splitting. Herein, we report a novel ...excellent porous molybdenum tungsten phosphide (Mo-W-P) hybrid nanosheet catalyst for hydrogen evolution, which is synthesized via in situ phosphidation of molybdenum tungsten oxide (Mo-W-O) hybrid nanowires grown on carbon cloth. The three-dimensional (3D) hierarchical hybrid electrocatalyst exhibits impressively high electrocatalytic activity with a low overpotential of 138 mV required to achieve a high current density of 100 mA cm-2 and a small Tafel slope of 52 mV dec-1 in 0.5 M H2SO4, which are significantly higher than those of single MoP nanosheets and WP2 nanorods. Such an outstanding performance of the Mo-W-P hybrid electrocatalyst is attributed to the 3D conductive scaffolds, porous nanosheet structure, and strong synergistic effect of W and Mo atoms in Mo-W-P, making it a very promising catalyst for hydrogen production. Our findings demonstrate that careful control over the morphology and composition of the electrocatalyst can achieve highly efficient hybrid electrocatalysts.
We propose nano-constriction engineering of armchair graphene nanoribbons (AGNRs) to construct photoelectric nanodevices aiming to generate pure spin currents through the photogalvanic effect (PGE) ...using first-principles calculations. Two devices with different symmetries were designed, one by introducing only one isosceles zigzag triangle defect on the lower edge of the central region ('D1') and the other by two symmetrically distributed isosceles zigzag triangle defects on the two edges ('D2'). The results show that pure spin current without accompanying charge current can be generated in both junctions, but with a big difference that pure spin current can be generated only at special polarization angles
= 0°, 90° and 180 in device D1, while it can be generated at any polarization angle in D2. The robustness in D2 is attributed to the spatial inversion symmetry in geometry and the inversion antisymmetry of spin density. These findings suggest that local magnetism engineering provides a reliable method for generating robust pure spin currents with the PGE in nonmagnetic systems, especially opening up new possibilities for the application of AGNRs in spintronics.
Pure spin current for a structure with
C
s
symmetry (D1) can be obtained only at certain angles, while for a structure with spatial inverse symmetry (D2), it is robustly independent of the polarization angle.
Great attention to cost‐effective high‐efficiency solar power conversion of trihalide perovskite solar cells (PSCs) has been hovering at high levels in the recent 5 years. Among PSC devices, ...admittedly, TiO2 is the most widely used electron transport layer (ETL); however, its low mobility which is even less than that of CH3NH3PbI3 makes it not an ideal material. In principle, SnO2 with higher electron mobility can be regarded as a positive alternative. Herein, a SnO2 nanocolloid sol with ≈3 nm in size synthesized at 60 °C was spin‐coated onto the fuorine‐doped tin oxide (FTO) glass as the ETL of planar CH3NH3PbI3 perovskite solar cells. TiCl4 treatment of SnO2‐coated FTO is found to improve crystallization and increase the surface coverage of perovskites, which plays a pivotal role in improving the power conversion efficiency (PCE). In this report, a champion efficiency of 14.69% (Jsc = 21.19 mA cm−2, Voc = 1023 mV, and FF = 0.678) is obtained with a metal mask at one sun illumination (AM 1.5G, 100 mW cm−2). Compared to the typical TiO2, the SnO2 ETL efficiently facilitates the separation and transportation of photogenerated electrons/holes from the perovskite absorber, which results in a significant enhancement of photocurrent and PCE.
SnO2 nanocolloids are synthesized for planar CH3NH3PbI3 perovskite solar cells. A champion efficiency of 14.69% is achieved for the SnO2‐based solar cell, which is superior to the TiO2‐based solar cell (13.38%) due to a higher electron mobility and negative conduction band, facilitating the electron injection, charge separation, and collection, which contribute to the improvement of photovoltaic performance.
A highly selective, efficient and practical method for synthesizing primary alcohols was presented. By using cheap Fe(BF4)2 ⋅ 6H2O and /tris2‐(diphenylphosphino)phenylphosphine (L1) as catalysts with ...formic acid as hydrogen source, a variety of primary alcohols bearing versatile functional groups could be obtained from both alkyl‐ and aryl‐substituted epoxides under mild conditions.
Highly selective and efficient synthesis of primary alcohols from epoxides could be achieved under mild conditions by iron catalysis, this process used formic acid as hydrogen source and was suitable for both alkyl‐ and aryl‐substituted epoxides.
In this work, we study the photogalvanic effect of a zigzag graphene nanoribbon junction with a centro-symmetrical structure which consists of 8 zigzag chains by density functional calculations. ...Specifically, we focus on the cases where the irradiated region is just part of the central region and located at different positions, with an aim to see how the spin dependent photocurrents will change and whether pure spin current can be obtained. It is found that the magnitude of the spin-dependent photocurrents increases with a gradual increase of the irradiated region and pure spin current is achieved when and only when the entire central region is irradiated. In addition, we studied the additive effect in this device to see that if we divide the central region into two parts, whether the sum of the spin current generated by irradiating the two parts individually is equal to that produced when the entire central region is irradiated. It is found that the sum of the spin currents produced by irradiating the two parts individually is smaller than that obtained by irradiating the whole central region, which means that the rule of "1 + 2 = 3" does not hold and the coupling effect between the two parts is important in photocurrent generation.
In this work, we study the photogalvanic effect of a zigzag graphene nanoribbon junction with a centro-symmetrical structure which consists of 8 zigzag chains using density functional calculations.
Designing and exploring efficient and stable non-noble bifunctional catalysts by nanostructure modification and chemical composition tuning for water splitting is of critical importance for ...sustainable resources. Herein, pure phase nickel molybdenum phosphide (NiMoP2) nanowires on carbon cloth are successfully synthesized through a simple and highly reproducible in situ P/O exchange process. Such a NiMoP2 nanowire catalyst requires low overpotentials of 199 and 330 mV to obtain a high current density of 100 mA cm-2 towards the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, and is among the most active HER and OER electrocatalysts yet reported. The bifunctional NiMoP2 is used as both anode and cathode catalysts in a two-electrode water electrolysis configuration, which delivers a current density of 10 mA cm-2 under a potential of 1.67 V. Furthermore, the overall water-splitting of the bifunctional NiMoP2 nanowire catalyst is further driven by a dry battery with a nominal voltage of 1.5 V which exhibits excellent performance and durability in a strong alkaline electrolyte.
The light-harvesting chlorophyll a/b binding proteins (LHCB) are perhaps the most abundant membrane proteins in nature. It is reported here that the down-regulation or disruption of any member of the ...LHCB family, LHCB1, LHCB2, LHCB3, LHCB4, LHCB5, or LHCB6, reduces responsiveness of stomatal movement to ABA, and therefore results in a decrease in plant tolerance to drought stress in Arabidopsis thaliana. By contrast, over-expression of a LHCB member, LHCB6, enhances stomatal sensitivity to ABA. In addition, the reactive oxygen species (ROS) homeostasis and a set of ABA-responsive genes are altered in the lhcb mutants. These data demonstrate that LHCBs play a positive role in guard cell signalling in response to ABA and suggest that they may be involved in ABA signalling partly by modulating ROS homeostasis.
We construct zigzag graphene nanoribbon junctions for generating pure spin current through the photogalvanic effect (PGE) by first-principles calculations. Two devices with spatial inversion symmetry ...are designed, both consisting of three zigzag graphene nanoribbons (ZGNRs) that introduce either two carbon tetragons ("2-C4") or two carbon hexagons ("2-C6") as connectors. The results show that robust pure spin current without charge current can be generated in both structures. The mechanism originates from the spatial inversion antisymmetric spin density as well as the spatial inversion symmetry of the geometrical structures. Furthermore, when more connectors are involved, we generalize that for structures with carbon tetragons as connectors, an even number of connectors are required to generate pure spin currents, while for structures with carbon hexagon connectors, any number of connectors can form pure spin currents. In addition, we find that larger pure spin currents can be obtained in the case of using hexagons as connectors. These findings provide a scheme for obtaining pure spin currents based on graphene nanoribbons, which has important reference implications for the design of spintronic devices with composite nanostructures.
Sweet tea (Lithocarpus polystachyus Rehd.) has been consumed as herbal tea to prevent and manage diabetes for a long time. Recent studies indicate that sweet tea is rich in a variety of bioactive ...compounds, especially a class of nonclassical flavonoids, dihydrochalcones. In order to provide a better understanding of sweet tea and its main dihydrochalcones on human health, this review mainly summarizes related literature in the recent ten years, with the potential molecular mechanisms emphatically discussed. Phlorizin, phloretin, and trilobatin, three natural sweeteners, are the main dihydrochalcones in sweet tea. In addition, sweet tea and its dihydrochalcones exhibit plenty of health benefits, such as antioxidant, anti-inflammatory, antimicrobial, cardioprotective, hepatoprotective, antidiabetic, and anticancer effects, which are associated with the regulation of different molecular targets and signaling pathways. Therefore, sweet tea, as a rare natural source of dihydrochalcones, can be processed and developed into nutraceuticals or functional foods, with the potential application in the prevention and management of certain chronic diseases.
Rumination is closely linked to the onset and maintenance of major depressive disorder (MDD). Prior neuroimaging studies have identified the association between self-reported rumination trait and the ...functional coupling among a network of brain regions using resting-state functional magnetic resonance imaging (MRI). However, little is known about the underlying neural circuitry mechanism during active rumination in MDD. Degree centrality (DC) is a simple metric to denote network integration, which is critical for higher-order psychological processes such as rumination. During an MRI scan, individuals with MDD (N = 45) and healthy controls (HC, N = 46) completed a rumination state task. We examined the interaction effect between the group (MDD vs. HC) and condition (rumination vs. distraction) on vertex-wise DC. We further characterized the identified brain region's functional involvement with Neurosynth and BrainMap. Network-wise seed-based functional connectivity (FC) analysis was also conducted for the identified region of interest. Finally, exploratory correlation analysis was conducted between the identified region of interest's network FCs and self-reported in-scanner affect levels. We found that a left superior frontal gyrus (SFG) region, generally overlapped with the frontal eye field, showed a significant interaction effect. Further analysis revealed its involvement with executive functions. FCs between this region, the frontoparietal, and the dorsal attention network (DAN) also showed significant interaction effects. Furthermore, its FC to DAN during distraction showed a marginally significant negative association with in-scanner affect level at the baseline. Our results implicated an essential role of the left SFG in the rumination's underlying neural circuitry mechanism in MDD and provided novel evidence for the conceptualization of rumination in terms of impaired executive control.
PDF
