Strain tuned InSe/MoS2 bilayer van der Waals heterostructures for photovoltaics or photocatalysis.

The isolation of different two-dimensional materials and the possibility to combine them in vertical stacks have led to new material systems, namely heterostructures based on two-dimensional crystals. By using density functional theory, we found that the InSe/MoS2 bilayer shows an indirect band gap of 0.65 eV with optical absorption over a wide range (300-800 nm) and a preferable separation of photogenerated electron-hole pairs. Moreover, the band gap can be readily tuned by external strain engineering, leading to a transition from the indirect band gap to a direct band gap of 1.55 eV under 7% compressive strain, where there is an enhanced and continuous spectrum. In addition, under a tensile strain of 9%, the bilayer is metallic. All of these properties enable the development of excellent photoelectric devices from the heterostructures with strain engineering.

Tailored nanoporous gold for ultrahigh fluorescence enhancement.

We report molecular fluorescence enhancement of free-standing nanoporous gold in which the nanoporosity can be arbitrarily tailored by the combination of dealloying and electroless gold plating. The nanoporous gold fabricated by this facile method possesses unique porous structures with large gold ligaments and very small pores, and exhibits significant improvements in surface enhanced fluorescence as well as structure rigidity. It demonstrates that the confluence effect of improved quantum yield and excitation of fluorophores is responsible for the large fluorescence enhancement due to the near-field enhancement of nanoporous gold, which arises from the strong electromagnetic coupling between neighboring ligaments and the weakening of plasmon damping of the large ligaments because of the small pore size and large ligament size, respectively.

[Integration of clinical significance and statistical significance on clinical study results categorization: a Meta-epidemiology study].

Objective: Statistical significance plays an important role in the interpretation of clinical trial results. However, on the basis of obtaining statistical significance, the assessment of clinical significance is often neglected. This study attempted to propose a simple and unambiguous new classification method for study results, focusing on studies with statistical positive findings to evaluate whether the results have clinical significance. Methods: Our study subjects were the clinical studies in 2019 ACC and ESC annual meetings. Meta-epidemiology methods were used to extract the characteristic variable from each study. The primary evaluation indicators included target effect-size and observed effect-size. Based on the difference between the two indicators, the studies that had statistical significance were subdivided to identify studies with possible insufficient clinical significance; Furthermore, the theoretical threshold based on power analysis was proposed, which was used as the basis for the interpretation of study results. Results: There were 12 clinical studies included in the final analysis. All of them were published on top journals. Those studies had relative high quality on both study design and reporting. The correlation coefficient between the observed and target effect-size was 0.892. Among the 7 studies with statistical significance, two of them were classified as insufficient clinical significance. The counts was 1 (1/3) and 1 (1/4) for the studies reported in ACC and ESC respectively. Conclusions: The achievement of clinical significance is critical even in the study with positive results. This paper proposes a new classification standard that combines clinical significance with statistical significance and further suggests a method to evaluate the reliability of clinical study results in order to assist researchers in identifying potential risks caused by insufficient clinical significance, and provide some reference and help for the reasonable interpretation of clinical study results.

Al13@Pt42 core-shell cluster for oxygen reduction reaction.

To increase Pt utilization for oxygen reduction reaction (ORR) in fuel cells, reducing particle sizes of Pt is a valid way. However, poisoning or surface oxidation limits the smallest size of Pt particles at 2.6 nm with a low utility of 20%. Here, using density functional theory calculations, we develop a core-shell Al13@Pt42 cluster as a catalyst for ORR. Benefit from alloying with Al in this cluster, the covalent Pt-Al bonding effectively activates the Pt atoms at the edge sites, enabling its high utility up to 70%. Valuably, the adsorption energy of O is located at the optimal range with 0.0-0.4 eV weaker than Pt(111), while OH-poisoning does not observed. Moreover, ORR comes from O2 dissociation mechanism where the rate-limiting step is located at OH formation from O and H with a barrier of 0.59 eV, comparable with 0.50 eV of OH formation from O and H2O on Pt(111).

Electron scattering and electrical conductance in polycrystalline metallic films and wires: impact of grain boundary scattering related to melting point.

For electrical conductance in polycrystalline metallic films and wires, the reflection coefficient of electrons at grain boundaries is explored and found to be proportional to the square root of the melting points of metals. As validated by available experimental results, this exploration enables classical models to take an essential role in theoretically predicting the electrical conductance of low-dimensional metals. One thus sees that the mechanism dominating the suppression of electrical conductance is transformed from the surface scattering into the grain boundary scattering as the ratio of film thickness (or wire diameter) to grain size rises. Furthermore, the impact of grain boundary scattering becomes less important for metals with lower melting points.

Nature of solidification of nanoconfined organic liquid layers.

A simple model is established for solidification of a nanoconfined liquid under nonequilibrium conditions. In terms of this model, the nature of solidification is the conjunct finite size and interface effects, which is directly related to the cooling rate or the relaxation time of the undercooled liquid. The model predictions are consistent with available experimental results.