Spontaneous gaze following and the concomitant joint attention enable us to share representations of the world with others, which forms a foundation of a broad range of social cognitive processes. ...Although this form of social orienting has long been suggested as a critical starting point for the development of social and communicative behavior, there is limited evidence directly linking it to higher-level social cognitive processes among healthy adults. Here, using a gaze-cuing paradigm, we examined whether individual differences in gaze following tendency predict higher-order social cognition and behavior among healthy adults. We found that individuals who showed greater gaze-cuing effect performed better in recognizing others’ emotion and had greater tendency to conform with group opinion. These findings provide empirical evidence supporting the fundamental role of low-level socio-attentional processes in human sociality.
Two-dimensional (2D) materials and van der Waals heterostructures with atomic-scale thickness provide enormous potential for advanced science and technology. However, insufficient knowledge of ...compatible synthesis impedes wafer-scale production. PdSe2 and Pd2Se3 are two of the noble transition-metal chalcogenides with excellent physical properties that have recently emerged as promising materials for electronics, optoelectronics, catalyst, and sensors. This research presents a feasible approach to synthesize PdSe2 and Pd2Se3 with inherently asymmetric structure on honeycomb lattice 2D monolayer substrates of graphene and MoS2. We directly deposit a molecular transition-metal precursor complex on the surface of the 2D substrates, followed by low-temperature selenization by chemical vapor flow. Parameter control leads to tuning of the material from monolayer nanocrystals with Pd2Se3 phase, to continuous few-layer PdSe2 films. Annular dark-field scanning transmission electron microscopy (ADF-STEM) reveals the structure, phase variations, and heteroepitaxy at the atomic level. PdSe2 with unconventional interlayer stacking shifts appeared as the kinetic product, whereas the bilayer PdSe2 and monolayer Pd2Se3 are the thermodynamic product. The epitaxial alignment of interlayer rotation and translation between the PdSe2 and underlying 2D substrate was also revealed by ADF-STEM. These results offer both nanoscale and atomic-level insights into direct growth of van der Waals heterostructures, as well as an innovative method for 2D synthesis by predetermined nucleation.
Abstract
Single-photon emitters are crucial building blocks for optical quantum technologies. Hexagonal boron nitride (hBN) is a promising two-dimensional material that hosts bright, room-temperature ...single-photon emitters. However, photo instability is a persistent challenge preventing practical applications of these properties. Here, we reveal the ubiquitous photobleaching of hBN vacancy emitters. Independent of the source or the number of hBN layers, we find that the photobleaching of a common emission at 1.98 ± 0.05 eV can be described by two consistent time constants, namely a first bleaching lifetime of 5 to 10 s, and a second bleaching lifetime in the range of 150 to 220 s. Only the former is environmentally sensitive and can be significantly mitigated by shielding O
2
, whereas the latter could be the result of carbon-assisted defect migration. Annular dark-field scanning transmission electron microscopy of photobleached hBN allows for visualizing vacancy defects and carbon substitution at single atom resolution, supporting the migration mechanism along with X-ray photoelectron spectroscopy. Thermal annealing at 850 °C of liquid exfoliated hBN eliminates both bleaching processes, leading to persistent photostability. These results represent a significant advance to potentially engineer hBN vacancy emitters with the photostability requisite for quantum applications.
Magnesium-ion batteries have been regarded as a promising alternative to the lithium-ion batteries due to their high theoretical capacity, relatively high potential, and magnesium abundance. However, ...the contradiction between the plating/stripping of Mg 2+ and the electrolytes’ oxidative stability has hampered the Mg-ion battery's development for energy storage applications. Here, we designed an amorphous MgO-wrapped Zn-skeleton as a unique current collector for an anode-free Mg battery to allow reversible Mg 2+ plating/stripping in oxidatively stable electrolytes. The significant lattice mismatch between hexagonal Zn and MgO induces dislocations, leading to a highly defective interphase. This layer behaves as a mixed ionic-electronic conductor, rendering Mg nanoparticles upon electroplating. Combined with a large surface area, the proposed current collector considerably improved the charge transfer kinetics and lowered the cell impedance for Mg 2+ plating/stripping by 1/20 of the typical Mg metal. Moreover, the Mg 2+ interphase conduction was two orders of magnitude higher (∼10 −11 S cm −1 ) compared to the widely known passivating layer (<10 −13 S cm −1 ). This special design enables Mg–Li hybrid batteries with non-corrosive electrolytes to exhibit a high-operating-voltage of 2.82 V vs. Mg/Mg 2+ and an energy density of 412.5 W h kg −1 .
High-nickel layered oxide cathodes suffer seriously from the formation of residual lithium on the surface, which causes notorious issues, such as slurry gelation and gas evolution. Due to the use of ...water for the titration to determine the residual lithium content, certain practical issues remain unresolved. We present here, for the first time, a thorough study of residual lithium that reveals the following. (1) Li2CO3 impurity in lithium raw materials contributes to an increase in residual lithium in high-Ni cathodes after synthesis. (2) LiOH formed due to a leaching of Li from high-Ni cathodes during analyte preparation in water exaggerates the LiOH content in residual lithium (employing a new titration method). (3) A dry cobalt hydroxide coating on high-Ni cathodes not only effectively reduces residual lithium content but also leads to the formation of a Co-rich concentration gradient layer on the surface that suppresses Li leaching when in contact with water.
As the push for inexpensive vehicle electrification grows, high-energy-density cathodes for lithium-ion batteries, such as high-nickel layered oxides, have received a great deal of attention in both ...industry and academia. These materials, however, suffer from severe residual lithium formation, which causes slurry gelation during electrode fabrication and gas evolution during cycling. Herein, a novel cobalt hydroxide coating method on wet-CO2 gas-treated LiNi0.91Mn0.03Co0.06O2 (Co-CO2-NMC91) is presented. Notably, the wet-CO2 treatment prior to a dry cobalt hydroxide coating plays a critical role in improving the coating uniformity and ultimately decreases the effective residual lithium content. Furthermore, full cells of Co-CO2-NMC91 exhibit excellent capacity retention of 91% after 200 cycles. This study highlights how a wet-CO2 treatment can be used to improve a typical dry coating and provides new insights toward the development of cathodes for high-energy-density LIBs without severe slurry gelation or gas evolution.
Spiral Growth of Adlayer Graphene Sun, Haibin; Kong, Xiao; Park, Hyoju ...
Advanced materials (Weinheim)
34, Issue:
12
Journal Article
Peer reviewed
The morphology of as‐grown graphene in chemical vapor deposition (CVD) experiments is sensitive to the reaction environment. Understanding the mechanism of formation of different graphene ...morphologies is essential to achieve controlled graphene CVD growth. Here the growth and formation mechanism of adlayer graphene spirals are reported. An adlayer graphene spiral is formed by fast propagation of the tips of spiral arms along the edge of the first graphene layer. The driving force to form spirals is the limited availability of carbon diffusing from the Cu surface through the edge of the first graphene layer. In addition, it is found that graphene onions are formed by overlapping graphene spirals with clockwise and anticlockwise arms. Based on these features, a kinetic Monte Carlo (kMC) method is demonstrated using which all the observed graphene spiral structures are successfully reproduced at the atomic level. This study thus unravels the hither‐to unresolved mechanism of graphene onion growth and paves the way to the controllable growth of few‐layer graphene by increasing the carbon supply at the edge of the first layer graphene.
The growth of adlayer graphene spirals and onions with novel spiral arms by chemical vapor deposition (CVD) is confirmed. These CVD‐prepared graphene spirals and onions exhibit more than one arm (with two, three, four, and five arms) together with clockwise and anticlockwise direction of rotation of each arm, which can be reproduced by using the kinetic Monte Carlo simulations.
Understanding Li distribution in layered lithium transition-metal oxide (LiTMO) cathodes in Li-ion batteries has been a major challenge at the atomic scale and nanoscale. Li is extremely difficult to ...study by transmission electron microscopy (TEM) because the high-energy electrons impart significant energy and cause massive migration. Here, we directly map the intrinsic spatial distribution and bonding of Li in LiNiO2-layered cathode materials using low-dose and low-loss electron energy loss spectroscopy (EELS). EELS spectra of the Li–K edge are measured simultaneously with O–K and Ni–L, M3,2 edges from layered, cation-mixed, and rock-salt phases and directly matched with atomic-resolution scanning TEM images to correlate the changes in peak intensities and positions to the stoichiometry changes with continual loss of Li and O. Changes in the Li content in the LiNiO2 particles as a function of electron beam dose are studied by sequential Li spectroscopic mapping. We show that the “intrinsic” Li distribution can be observed using a total dose of less than ∼1.5 × 108 e– nm–2 at an accelerating voltage of 80 kV. The method of nanoscale mapping of Li distribution introduced in this study is applicable to high-Ni LiTMO cathode materials (>89% of Ni) as well as LiNiO2. Further study on the extra peaks of the Li–K edge reveals that the peak at ∼59 eV is from the Li ions intercalated in between NiO2 layers barely interacting with each other with less Li K shell electrons pulled to the L shell electrons in NiO2. The results shown here provide improved low-loss TEM characterization approaches that can be used to understand the intrinsic fundamental behaviors in Li-ion batteries.
Magnesium-ion batteries have been regarded as a promising alternative to the lithium-ion batteries due to their high theoretical capacity, relatively high potential, and magnesium abundance. However, ...the contradiction between the plating/stripping of Mg
2+
and the electrolytes' oxidative stability has hampered the Mg-ion battery's development for energy storage applications. Here, we designed an amorphous MgO-wrapped Zn-skeleton as a unique current collector for an anode-free Mg battery to allow reversible Mg
2+
plating/stripping in oxidatively stable electrolytes. The significant lattice mismatch between hexagonal Zn and MgO induces dislocations, leading to a highly defective interphase. This layer behaves as a mixed ionic-electronic conductor, rendering Mg nanoparticles upon electroplating. Combined with a large surface area, the proposed current collector considerably improved the charge transfer kinetics and lowered the cell impedance for Mg
2+
plating/stripping by 1/20 of the typical Mg metal. Moreover, the Mg
2+
interphase conduction was two orders of magnitude higher (∼10
−11
S cm
−1
) compared to the widely known passivating layer (<10
−13
S cm
−1
). This special design enables Mg-Li hybrid batteries with non-corrosive electrolytes to exhibit a high-operating-voltage of 2.82 V
vs.
Mg/Mg
2+
and an energy density of 412.5 W h kg
−1
.
Mg
2+
electroplating has been an obstacle for Mg metal batteries due to the passivating nature of Mg metal. Here, a unique current collector based on an amorphous MgO-wrapped Zn-skeleton enabled Mg
2+
electroplating for a high-voltage Mg metal battery.
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