NaF-Rich Multifunctional Layers toward Stable All-Solid-State Sodium Batteries.

NASICON oxide solid electrolytes are considered promising candidates for all-solid-state sodium batteries due to their extremely high ionic conductivity and favorable electrochemical stability. However, the practical application of NASICON electrolytes is greatly impeded by poor electrolyte-electrode interfacial contact and continuous sodium dendrite propagation. Herein, a NaF-rich multifunctional interface layer on the surface of a Na anode (Na@NaF-rich), containing NaF, amorphous carbon, and an unreacted C-F bond species, is developed in situ by the reaction between Na and commercial poly(tetrafluoroethylene). This NaF-rich interface layer is proven to reduce the diffusion barriers at the Na/NASICON electrolyte interface and homogenize Na deposition as well as suppress Na dendrite growth, thus achieving a high critical current density of 4 mA cm-2. The resultant Na3V2(PO4)3@C/Na@NaF-rich all-solid-state cell showed a high initial specific capacity of 117.6 mAh g-1 at 0.1 C with a Coulombic efficiency of 94.8%. Even at 0.5 and 1 C, it still exhibited high capacity retentions of 83.3% and 80.4%, respectively, after 750 cycles.

Color-stable blue light-emitting diodes with defect management by sulfonate.

Utilizing bromine-based quasi-two-dimensional (quasi-2D) perovskite is a feasible strategy to achieve efficient and stable blue perovskite light-emitting diodes (PeLEDs). However, dimension discretization is prone to emerge due to the irregular phase distribution and massive defects in the perovskite system. Here, we introduce alkali-salt to modulate the phase distribution for reducing the n = 1 phase and propose a novel Lewis base to serve as a passivating agent to decrease defects. This revealed that the external quantum efficiency (EQE) dramatically improves due to the suppression of severe non-radiative recombination losses. Consequently, efficient blue PeLEDs were obtained with a peak EQE of 3.82% located at 487 nm.

Solvent polishing engineering for quasi-two-dimensional perovskite blue light-emitting diodes.

Solvent polishing engineering is adopted to remove the relatively loose defect layer without damaging carrier injection in blue perovskite light-emitting-diodes (PeLEDs). Synchronously, the polishing effects depending on the solvents are discussed in detail. Finally, optimized blue PeLEDs were obtained with a maximum external quantum efficiency of 5.18%, high brightness of 3737 cd m-2, and a low turn-on voltage of 3.2 V.

Enhanced catalytic performance of Pt by coupling with carbon defects.

Defect engineering is a promising strategy for supported catalysts to improve the catalytic activity and durability. Here, we selected the carbon (C) matrix enriched with topological defects to serve as the substrate material, in which the topological defects can act as anchoring centers to trap Pt nanoparticles for driving the O2 reduction reactions (ORRs). Both experimental characterizations and theoretical simulations revealed the strong Pt-defect interaction with enhanced charge transfer on the interface. Despite a low Pt loading, the supported catalyst can still achieve a remarkable 55 mV positive shift of half-wave potential toward ORR in O2-saturated 0.1 M HClO4 electrolyte compared with the commercial Pt catalyst on graphitized C. Moreover, the degeneration after 5,000 voltage cycles was negligible. This finding indicates that the presence of strong interaction between Pt and topological C defects can not only stabilize Pt nanoparticles but also optimize the electronic structures of Pt/C catalysts toward ORR.

Ammonia Thermal Treatment toward Topological Defects in Porous Carbon for Enhanced Carbon Dioxide Electroreduction.

Topological defects, with an asymmetric local electronic redistribution, are expected to locally tune the intrinsic catalytic activity of carbon materials. However, it is still challenging to deliberately create high-density homogeneous topological defects in carbon networks due to the high formation energy. Toward this end, an efficient NH3 thermal-treatment strategy is presented for thoroughly removing pyrrolic-N and pyridinic-N dopants from N-enriched porous carbon particles, to create high-density topological defects. The resultant topological defects are systematically investigated by near-edge X-ray absorption fine structure measurements and local density of states analysis, and the defect formation mechanism is revealed by reactive molecular dynamics simulations. Notably, the as-prepared porous carbon materials possess an enhanced electrocatalytic CO2 reduction performance, yielding a current density of 2.84 mA cm-2 with Faradaic efficiency of 95.2% for CO generation. Such a result is among the best performances reported for metal-free CO2 reduction electrocatalysts. Density functional theory calculations suggest that the edge pentagonal sites are the dominating active centers with the lowest free energy (ΔG) for CO2 reduction. This work not only presents deep insights for the defect engineering of carbon-based materials but also improves the understanding of electrocatalytic CO2 reduction on carbon defects.

Temperature Dependence Of AOS Thin Film Nano Transistors For Medical Applications.

BACKGROUND: A novel temperature dependent amorphous nano oxide semiconductor (AOS) thin-film transistor (TFT) is reported here for the first time, which is vastly different from conventional behavior. In the literature, the threshold voltage of TFTs decreases with increasing temperature. Here, the threshold voltage increased at higher temperatures, which is different from previously reported results and was repeated on different samples. METHODS: Electrical experiments (such as I-V measurements and photoelectron spectrometer experiments) were performed in order to explain such behavior. Double sweeping gate voltage measurements were performed to investigate the mechanism for the temperature dependent behavior. RESULTS: It was found that there was a change of trap charge under thermal stress, which was released after the stress. CONCLUSION: Non-Arrhenius behaviors (including a linear behavior) were obtained for the amorphous nano oxide thin-film transistors within 303~425 K, suggesting their potential to be adjusted by measurement processes and be applied as temperature sensors for numerous medical applications.

Change Of Nano Material Electrical Characteristics For Medical System Applications.

Amorphous nano oxides (AO) are intriguing advanced materials for a wide variety of nanosystem medical applications including serving as biosensors devices with p-n junctions, nanomaterial-enabled wearable sensors, artificial synaptic devices for AI neurocomputers and medical mimicking research. However, p-type AO with reliable electrical properties are very difficult to obtain according to the literature. Based on the oxide thin film transistor, a phenomenon that could change an n-type material into a p-type semiconductor is proposed and explained here. The typical In-Ga-Zn-O material has been reported to be an n-type semiconductor, which can be changed by physical conditions, such as in processing or bias. In this way, here, we have identified a manner to change nano material electrical properties among n-type and p-type semiconductors very easily for medical application like biosensors in artificial skin.

Assembling Ultrasmall Copper-Doped Ruthenium Oxide Nanocrystals into Hollow Porous Polyhedra: Highly Robust Electrocatalysts for Oxygen Evolution in Acidic Media.

Here, a facile and novel strategy for the preparation of Cu-doped RuO2 hollow porous polyhedra composed of ultrasmall nanocrystals through one-step annealing of a Ru-exchanged Cu-BTC derivative is reported. Owing to the optimized surface configuration and altered electronic structure, the prepared catalyst displays a remarkable oxygen evolution reaction (OER) performance with low overpotential of 188 mV at 10 mA cm-2 in acidic electrolyte, an ultralow Tafel slope of 43.96 mV dec-1 , and excellent stability in durability testing for 10 000 cycles, and continuous testing of 8 h at a current density of 10 mA cm-2 . Density functional theory calculations reveal that the highly unsaturated Ru sites on the high-index facets can be oxidized gradually and reduce the energy barrier of rate-determining steps. On the other hand, the Cu dopants can alter the electronic structures so as to further improve the intrinsic OER activity.

Analysis of oxidation degree of graphite oxide and chemical structure of corresponding reduced graphite oxide by selecting different-sized original graphite.

The thermal exfoliation and reduction of graphite oxide (GO) is the most commonly used strategy for large-scale preparation of graphene, and the oxidation degree of GO would influence the chemical structure of prepared graphene, thereby affecting its final physical and chemical properties. In addition to serving as the precursor for synthesizing graphene, GO also possesses great potential for various important applications owing to its abundant oxygen-containing groups and hybrid electronic structure. Therefore, systematically studying the influencing factors on the oxidation degree of GO and clarifying the effect of oxidation degree on the corresponding graphene is particularly important. Herein, we have studied the effect of the lateral size of the original graphite on the oxidation degree of GO in order to control the oxidation degree of GO. GOs with different degrees of oxidation were synthesized using a modified Hummers method. The results of X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and Raman spectroscopy revealed that decreased lateral size of the original graphite would lead to increased oxidation degree of GO. Furthermore, the interlayer spacing of the GO samples achieved 0.9-1.0 nm, which indicated that the modified Hummers method could make well oxidized graphite. The corresponding reduced graphite oxide (rGO) was also prepared by low-temperature exfoliation of GO at 140 °C under ambient atmosphere. It was found that a larger lateral size of GO resulted in rGO with fewer oxygen-containing functional groups, but a smaller lateral size of graphite possessed a higher exfoliation degree with a larger specific surface area. More importantly, the relationship between binding energy (E B) of photoelectron of C atom in oxygen-containing groups and the number of oxygen-containing groups in GO and rGO samples was analyzed theoretically.

A Direct Method to Extract Transient Sub-Gap Density of State (DOS) Based on Dual Gate Pulse Spectroscopy.

Sub-gap density of states (DOS) is a key parameter to impact the electrical characteristics of semiconductor materials-based transistors in integrated circuits. Previously, spectroscopy methodologies for DOS extractions include the static methods, temperature dependent spectroscopy and photonic spectroscopy. However, they might involve lots of assumptions, calculations, temperature or optical impacts into the intrinsic distribution of DOS along the bandgap of the materials. A direct and simpler method is developed to extract the DOS distribution from amorphous oxide-based thin-film transistors (TFTs) based on Dual gate pulse spectroscopy (GPS), introducing less extrinsic factors such as temperature and laborious numerical mathematical analysis than conventional methods. From this direct measurement, the sub-gap DOS distribution shows a peak value on the band-gap edge and in the order of 10(17)-10(21)/(cm(3)·eV), which is consistent with the previous results. The results could be described with the model involving both Gaussian and exponential components. This tool is useful as a diagnostics for the electrical properties of oxide materials and this study will benefit their modeling and improvement of the electrical properties and thus broaden their applications.

Mechanical properties and structural features of novel Fe-based bulk metallic glasses with unprecedented plasticity.

Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their unique magnetic and mechanical properties, but few applications have been materialized because of their brittleness at room temperature. Here we report a new Fe(50)Ni(30)P(13)C(7) BMG which exhibits unprecedented compressive plasticity (>20%) at room temperature without final fracture. The mechanism of unprecedented plasticity for this new Fe-based BMG was also investigated. It was discovered that the ductile Fe(50)Ni(30)P(13)C(7) BMG is composed of unique clusters mainly linked by less directional metal-metal bonds which are inclined to accommodate shear strain and absorbed energy in the front of crack tip. This conclusion was further verified by the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy experiments of Fe(80-x)Ni(x)P(13)C(7) (x = 0, 10, 20, 30) and Fe(72-x)Ni(x)B(20)Si(4)Nb(4) (x = 0, 7.2, 14.4, 21.6, 28.8) glassy systems. The results also indicate a strong correlation between the p-d hybridization and plasticity, verifying that the transition from brittle to ductile induced by Ni addition is due to the change of bonding characteristics in atomic configurations. Thus, we can design the plasticity of Fe-based BMGs and open up a new possible pathway for manufacturing BMGs with high strength and plasticity.