Semiconductor crystals have generally shown facet‐dependent electrical, photocatalytic, and optical properties. These phenomena have been proposed to result from the presence of a surface layer with ...bond‐level deviations. To provide experimental evidence of this structural feature, synchrotron X‐ray sources are used to obtain X‐ray diffraction (XRD) patterns of polyhedral cuprous oxide crystals. Cu2O rhombic dodecahedra display two distinct cell constants from peak splitting. Peak disappearance during slow Cu2O reduction to Cu with ammonia borane differentiates bulk and surface layer lattices. Cubes and octahedra also show two peak components, while diffraction peaks of cuboctahedra are comprised of three components. Temperature‐varying lattice changes in the bulk and surface regions also show shape dependence. From transmission electron microscopy (TEM) images, slight plane spacing deviations in surface and inner crystal regions are measured. Image processing provides visualization of the surface layer with depths of about 1.5–4 nm giving dashed lattice points instead of dots from atomic position deviations. Close TEM examination reveals considerable variation in lattice spot size and shape for different particle morphologies, explaining why facet‐dependent properties are emerged. Raman spectrum reflects the large bulk and surface lattice difference in rhombic dodecahedra. Surface lattice difference can change the particle bandgap.
High‐resolution X‐ray diffraction patterns reveal bulk and surface layer components for polyhedral Cu2O crystals, while transmission electron microscopy analysis provides first visual evidence of the surface layer contributing to their various facet‐dependent properties. The surface layer can affect Raman spectra and tune the crystal bandgap.
Although transparent radiative cooling is a passive cooling strategy with practical applications and aesthetic appeal, complex manufacturing processes and the use of environmentally unfriendly ...thermal emitters remain latent problems. Herein, eco‐friendly transparent silk radiative cooling (TSRC) films are developed, regenerated from natural silkworm cocoons, for zero‐energy‐consumption thermal management of optoelectronic devices. These TSRC films can dissipate heat radiatively through molecular vibrations of the protein backbone and side chains, while retaining the function and appearance of the associated devices, due to their high visible transparency. Theoretical and experimental investigations revealed that the thermal emission increases rapidly upon increasing the film thickness, but slowly thereafter achieves saturation; nevertheless, the intrinsic solar absorption of silk in the ultraviolet and near‐infrared regions also grows linearly, unavoidably weakening the cooling effect. After spectroscopic optimization, the maximum cooling power during the daytime and nighttime is improved to 77.6 and 101.7 W m−2, respectively. Gratifyingly, the films have a remarkable effect on the cooling performance of electronic devices under sunlight. For example, the TSRC film provides a temperature drop of 5.1 °C for a smartphone during multitasking and charging, and 14 °C for a silicon solar panel with an improvement in the photoelectronic conversion efficiency (≈7%).
Transparent silk radiative cooling films can reduce the temperature of a silicon solar panel and a smartphone by 14 and 5.1 °C, respectively, even under direct sunlight, without compromising the function and appearance of the devices. This makes the transparent silk radiative cooling film an eco‐friendly and efficient solution for the thermal management of optoelectronic devices.
Stacking faults, as defects of disordered crystallographic planes, are one of the most important slipping mechanisms in the commonly seen lattice, face-centered cubic (FCC). Such defects can initiate ...twinning which strengthens mechanical properties, e.g. twinning-induced plasticity (TWIP), of high entropy alloys (HEAs) at cryogenic temperatures. In this work, by using density functional theory (DFT), the twinning initiated from stacking faults is discussed with regard to two different solute elements, Al and Mo, in the FeNiCoCr HEAs. Our results show that adding aluminum (Al) has noticeable enhancement of twinnability while molybdenum (Mo) only induces more stacking faults in the FeNiCoCr-based HEAs.
By using molecular dynamics and cluster dynamics simulations, we probed the role of hydrogen-vacancy complexes on nucleation and growth of proto nano-voids upon dislocation plasticity in α-Fe. Our ...atomistic simulations reveal that, unlike a lattice vacancy, a hydrogen-vacancy complex is not absorbed by dislocations sweeping through the lattice. Additionally, this complex has lower lattice diffusivity; therefore, it has a lower probability of encountering and being absorbed by various lattice sinks. Hence, it can exist metastably for a rather long time. Our large-scale molecular dynamics simulations show that when metals undergo plastic deformation in the presence of hydrogen at low homologous temperatures, the mechanically driven out-of-equilibrium dislocation processes can produce extremely high concentrations of hydrogen-vacancy complex (10−5 ∼ 10−3). Under such high concentrations, these complexes prefer to grow by absorbing additional vacancies and act as the embryos for the formation of proto nano-voids. The current work provides one possible route for the experimentally observed nano-void formation in hydrogen embrittlement of steels and bridges atomic-scale events and damage with macroscopic failure.
•By using multi-scale simulation techniques, we probed the role of hydrogen-vacancy complexes on proto nano-voids formation due to dislocation plasticity in α-Fe during hydrogen embrittlement.•Our atomistic and coarse-grained cluster dynamics simulations show that the concentration of hydrogen-vacancy complexes can reach extremely high levels during dislocation plasticity in the presence of hydrogen, and these hydrogen-vacancy complexes prefer to aggregate by absorbing additional vacancies and act as nuclei for nano-voids.•The current work provides the link between hydrogen-vacancy complexes at the atomic scale to macroscopic failure by nano-void coalescence in hydrogen embrittlement.
•Novel evaluations of stability based on DFT for adlayer hydroxides are presented.•Galvanic corrosion on B2 matrix is due to the lower stability of adlayer hydroxide.•The quality of Cr rich hydroxide ...dominates the corrosion behavior around Ecorr.•The stable ipass is related to lower ksp values of Co(OH)3, Fe(OH)3, and Cr(OH)3.•The annealing enhances the uniformity and corrosion resistance of passive film.
This work investigates the corrosion mechanism of annealed equiatomic AlCoCrFeNi tri-phase alloy in 0.5 M H2SO4 aerated aqueous solution. Experimental results indicate that the B2 matrix is preferentially corroded away while grain-boundary FCC and labyrinth-like BCC endure, consistent with the tendency of formation energy for monolayer hydroxide on the (001) plane of three phases calculated by the first principle based on density function theory. Furthermore, the stable passive current density is related to lower ksp values of Co(OH)3, Fe(OH)3, and Cr(OH)3, while the annealing effect on enhancing corrosion resistance is owing to the more uniformity of passive hydroxide film.
Surface 4-cyanophenylacetylene (4-CNA) functionalization enabled inert Cu2O cubes to possess a high photocatalytic activity. The modified rhombic dodecahedra also exhibited large activity ...enhancement, but decorated octahedra showed only moderate activity improvement. Holes are more important than electrons to the photocatalytic activity of 4-CNA-modified Cu2O cubes. Electron paramagnetic resonance (EPR) data confirm the observed photocatalytic results and show that both hydroxyl and superoxide radicals are photogenerated from modified Cu2O crystals. Density functional theory (DFT) calculations reveal the emergence of a narrow 4-CNA-derived band in the Cu2O band gap to facilitate electron transfer through the molecule to the crystal exterior for radical production. Bader charge difference and planar average local potential analyses also suggest good electron migration for Cu2O cubes through 4-CNA. The functionalized cubes can photocatalyze 4-methoxyphenylboronic acid hydroxylation with a high yield of 92% utilizing the generated superoxide radicals. Conjugated molecular functionalization on semiconductor crystals is a highly effective approach to boosting charge transfer.
Neuroinflammation and oxidative stress have been emerging as important pathways contributing to Parkinson's disease (PD) pathogenesis. In PD brains, the activated microglia release inflammatory ...factors such as interleukin (IL)-β, IL-6, tumor necrosis factor (TNF)-α, and nitric oxide (NO), which increase oxidative stress and mediate neurodegeneration. Using 1-methyl-4-phenylpyridinium (MPP
)-activated human microglial HMC3 cells and the sub-chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD, we found the potential of indole derivative NC009-1 against neuroinflammation, oxidative stress, and neurodegeneration for PD. In vitro, NC009-1 alleviated MPP
-induced cytotoxicity, reduced NO, IL-1β, IL-6, and TNF-α production, and suppressed NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in MPP
-activated HMC3 cells. In vivo, NC009-1 ameliorated motor deficits and non-motor depression, increased dopamine and dopamine transporter levels in the striatum, and reduced oxidative stress as well as microglia and astrocyte reactivity in the ventral midbrain of MPTP-treated mice. These protective effects were achieved by down-regulating NLRP3, CASP1, iNOS, IL-1β, IL-6, and TNF-α, and up-regulating SOD2, NRF2, and NQO1. These results strengthen the involvement of neuroinflammation and oxidative stress in PD pathogenic mechanism, and indicate NC009-1 as a potential drug candidate for PD treatment.
A hybrid composite of organic–inorganic semiconductor nanomaterials with atomic Au clusters at the interface decoration (denoted as PF3T@Au‐TiO2) is developed for visible–light‐driven H2 production ...via direct water splitting. With a strong electron coupling between the terthiophene groups, Au atoms and the oxygen atoms at the heterogeneous interface, significant electron injection from the PF3T to TiO2 occurs leading to a quantum leap in the H2 production yield (18 578 µmol g−1 h−1) by ≈39% as compared to that of the composite without Au decoration (PF3T@TiO2, 11 321 µmol g−1 h−1). Compared to the pure PF3T, such a result is 43‐fold improved and is the best performance among all the existing hybrid materials in similar configurations. With robust process control via industrially applicable methods, it is anticipated that the findings and proposed methodologies can accelerate the development of high‐performance eco‐friendly photocatalytic hydrogen production technologies.
The lattice distortion of a solute primarily occurs because its atomic size and chemical bonding are different from those of neighboring atoms. The lattice distortion effects in conventional and ...high-entropy alloys are different; however, a detailed investigation on these effects has yet to be conducted. To fill this research gap, this study produced face-centered cubic-structured dilute solutions (Ni, Ni–2 at.% W, and Ni–4 at.% W) and concentrated solutions (equiatomic CrFeNi and CoCrFeMnNi) and compared their tensile properties. For the two W-containing alloys, lattice distortion occurred only around the large and strong W atoms. However, for the two concentrated solutions, which had a similar interelement atomic size and shear modulus to the aforementioned alloys, lattice distortion occurred at all lattice sites. These two types of lattice distortion had significantly different effects on tensile properties. The strength and ductility of the alloys with a high concentration of distorted lattice points were higher than those of the alloys with a low concentration of distorted lattice points, although the alloys with a low concentration of distorted lattice points had a larger nominal atomic size difference and shear modulus difference. The mechanisms underlying the evolution of different mechanical properties under different types of lattice distortion were examined for the dilute and concentrated alloys. Moreover, the universal solid solution strengthening mechanism was observed.
Display omitted .
Surface 4-trifluoromethylphenylacetylene (4-TFMA) functionalization enables inert Cu2O cubes to exhibit a good photocatalytic activity. The modified rhombic dodecahedra also showed enhanced ...photocatalytic activity, but decorated octahedra actually delivered activity suppression. Scavenging experiments reveal that holes are more important than electrons for the photocatalytic activity of the functionalized cubes. Electron paramagnetic resonance (EPR) data agree with the observed photocatalysis results. Density functional theory (DFT) calculations disclose the emergence of one and two 4-TFMA-derived narrow bands within the band gap of the respective {110} and {100} surfaces of Cu2O to promote electron transfer through the molecule to the solution for radical generation, but no such band is present for the functionalized Cu2O {111} surface. Bader charge difference analysis also suggests promotion of charge transfer through 4-TFMA for the {100} and {110} surfaces of Cu2O, but the modification is less helpful over the {111} surface. The modified Cu2O cubes can also improve photocatalyzed arylboronic acid hydroxylation reactions. Conjugated molecular functionalization on semiconductor crystals is a powerful strategy for greatly enhancing electron transfer.
PDF
