Search

Copper complex catalysts exhibit excellent activity for the oxidative carbonylation of methanol to produce dimethyl carbonate (DMC). However, the reaction mechanism over Cu(I) or Cu(II) complex catalysts is not fully understood. In this study, homogeneous CuCl/CuCl2–NMI-m/n(N = N-methylimidazole; m/n= molar ratio of Cu(I) and Cu(II)) catalysts with organic ligand coordination are designed for oxidative carbonylation. The optimized CuCl/CuCl2–NMI-0.3/0.7 catalyst showed a TOF as high as 3.4 h–1and a DMC selectivity of 67.2% based on oxygen, which were superior to those of CuCl–NMI or CuCl2–NMI. Our experiments suggested that the high activity and selectivity were assigned to the synergistic effect between Cu(I) and Cu(II), in which Cu(I) and Cu(II) are mainly responsible for the rapid generation of copper carbonyl and copper methoxy intermediates, respectively. This synergistic effect not only enhances the reaction activity but also ensures high DMC selectivity.

Designing flexible wearable sensors with a wide sensing range, high sensitivity, and high stability is a vulnerable research direction with a futuristic field to study. In this paper, Ti3C2TxMXene/carbon nanotube (CNT)/thermoplastic polyurethane (TPU)/polysulfone (PSF) composite films with excellent sensor performance were obtained by self-assembly of conductive fillers in TPU/PSF porous films with an asymmetric structure through vacuum filtration, and the porous films were prepared by the phase inversion method. The composite films consist of the upper part with finger-like “cavities” filled by MXene/CNTs, which reduces the microcracks in the conductive network during the tensile process, and the lower part has smaller apertures of a relatively dense resin cortex assisting the recovery process. The exclusive layer structure of the MXene/CNTs/TPU/PSF film sensor, with a thickness of 46.95 μm, contains 0.0339 mg/cm2single-walled carbon nanotubes (SWNTs) and 0.348 mg/cm2MXene only, providing functional range (0–80.7%), high sensitivity (up to 1265.18), and excellent stability and durability (stable sensing under 2300 fatigue tests, viable to the initial resistance), endurably cycled under large strains with serious damage to the conductive network. Finally, the MXene/CNTs/TPU/PSF film sensor is usable for monitoring pulse, swallow, tiptoe, and various joint bends in real time and distributing effective electrical signals. This paper implies that the MXene/CNTs/TPU/PSF film sensor has broad prospects in pragmatic applications.

Graphical abstract:

Plasma as the fourth state of matter has attracted great attention for material surface modification, which could induce changes in material microscopic factors, such as defects, phase transitions, crystallinity, and so on. However, the interactions among those microscopic factors and regulation mechanism of macroscopic properties have rarely been investigated. Two-dimensional (2D) transition metal dichalcogenide with tunable structure and phase is one of the most promising electromagnetic wave (EMW) absorbers, which provides a favorable platform for systematically studying the dynamic coupling of its microscopic factors. Herein, we constructed a NaBH4solution-assisted Ar plasma method to modify the 2H-MoS2and 1T-WS2for exploring the regulation mechanism of microscopic factors. For MoS2and WS2, NaBH4solution-assisted Ar plasma treatment behaves with different effects on dielectric responses, realizing dynamic coupling of material microscopic factors to collaboratively promote EM losses coupling. Consequently, the MS-D3-0.5 (MoS2, 3 ​kV voltage, 0.5 ​mol ​L−1NaBH4solution) displays an optimum effective absorption bandwidth of 8.01 ​GHz, which is 319.4 ​% more than that of MS-raw sample. This study not only reveals the novel mechanism of plasma induced dynamic coupling of microscopic factors for EMW dissipation, but also presents a new method of plasma-dominated surface modification to optimize the EMW absorption performance.

In order to greatly improve the energy efficiency and electrolyte utilization efficiency of vanadium redox flow batteries (VRFBs) and to enable them to operate at high current densities, MXene/CoO composites were used for the first time in this research as electrocatalysts for the V3+/V2+reaction. The catalytic effect of the materials was characterized by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) tests. Then battery performance of MXene/CoO composite modified plasma-treated graphite felt (GF) negative electrodes (MXene/CoO/GF) were tested in a VRFB. The results show that MXene/CoO composites can improve the catalytic activity. There is a 22.93 % increase in energy efficiency and 124.94 % increase in electrolyte utilization efficiency when MXene/CoO/GF is applied as VRFB negative electrode at a current density of 200 mA cm−2compared to GF. At a current density of 250 mA cm−2, the energy efficiency of MXene/CoO/GF is maintained at 75.55 %. The excellent performance is attributed to the addition of MXene/CoO, which increases the active sites for redox reactions and thus improves the kinetics of the V3+/V2+reaction.

Ultra-light carboxylic functionalized multi-walled carbon nanotubes (CNTs-COOH) and Ti 3 C 2 MXene hybrids modified sodium alginate (CNTs/Ti 3 C 2 -SA) based composite foams were prepared through ice-templated freeze-drying method. The microstructure of the synthesized CNTs/Ti 3 C 2 hybrids and CNTs/Ti 3 C 2 -SA foams is characterized by the presence of CNTs inserted between MXene layers which prevents their restacking. The resultant CNTs/Ti 3 C 2 hybrids exhibit a unique sandwich-like hierarchical structure. Scanning electron microscopy (SEM) images show that the CNTs/Ti 3 C 2 -SA foam exhibits a heterogeneous anisotropic microstructure and CNTs/Ti 3 C 2 hybrids are homogeneously dispersed in the skeleton of the porous foam. In case that the content of the hybrids amounts 40 mg/cm3, the CNTs/Ti 3 C 2 -SA foam possesses excellent electromagnetic (EM) absorption performance with a minimum reflection coefficient (RC min) as low as -40.0 dB. In case of a sample thickness of 3.95 mm, the RC min reaches -24.4 dB and the effective absorption bandwidth covers the whole X band from 8.2 to 12.4 GHz. A control test shows that, with the same absorbent content, the CNTs/Ti 3 C 2 -SA foam exhibits a far better EM performance than that of CNT-free Ti 3 C 2 -SA foam. [ABSTRACT FROM AUTHOR]

Low velocity impacts usually cause invisible damage of composite structure，which is hard to be found and will cause catastrophic failure. In this work, the blade-coated MXene sensor was used to monitor impact damage of composite laminates. For the purpose of impact monitoring, an experiment was designed where composite laminates were subjected to controlled energy impacts. A circular sensor with a diameter of 100 mm was arranged on the back of the laminate. And ultrasonic C-scan was used to examine delamination damage of laminates after each impact. The experimental results show that the sensor identifies the onset of impact and the generation of damage. And the relative resistance changes of the sensor have a directly linear proportional relationship to the delamination size. There is also a functional relationship between the electrical response of the sensor and the impact energy. The findings are of great significance for the application of composite structure, and can effectively avoid the safety hazards caused by invisible impact delamination damage.

The composite overwrapped pressure vessel (COPV) is sensitive to impact, and even small impact damage may cause serious consequences. So the structural health monitoring of COPV is incredibly crucial, and a highly sensitive sensor is urgently needed to monitor dangerous areas. In this paper, the force-electric response characteristics of MXene sensor are investigated in low velocity impact experiments, and the impact behaviors of COVP are monitored by this sensor array. The experimental results show that the MXene sensor is very sensitive to low energy impact. Moreover, the response of the near-end sensor is opposite to that of the far-end sensor. According to the combined response of sensor array, the magnitude of impact energy and the position of the impact point can be determined. In addition, the sensor can respond to the strain load generated by resonance to ensure the safety factor of COPV. In a word, the impact force and damage degree of COPV can be monitored effectively using MXene sensor array in real-time.

The statistical power of genome-wide association studies (GWASs) is affected by the effective sample size. However, the privacy and security concerns associated with individual-level genotype data pose great challenges for cross-institutional cooperation. The full-process cryptographic solutions are in demand but have not been covered, especially the essential principal-component analysis (PCA). Here, we present TrustGWAS, a complete solution for secure, large-scale GWAS, recapitulating gold standard results against PLINK without compromising privacy and supporting basic PLINK steps including quality control, linkage disequilibrium pruning, PCA, chi-square test, Cochran-Armitage trend test, covariate-supported logistic regression and linear regression, and their sequential combinations. TrustGWAS leverages pseudorandom number perturbations for PCA and multiparty scheme of multi-key homomorphic encryption for all other modules. TrustGWAS can evaluate 100,000 individuals with 1 million variants and complete QC-LD-PCA-regression workflow within 50 h. We further successfully discover gene loci associated with fasting blood glucose, consistent with the findings of the ChinaMAP project.

Constructing effective photocatalysts with visible-light-driven for degrading VOCs including formaldehyde remains a challenge. The TiO2(B) photocatalyst with a two-dimensional lamellar structure was prepared and modified by surface engineering. The DFT calculation results showed new impurity levels appeared among the energy bands of the modified TiO2(B) materials. These photocatalysts exhibited different rates of HCHO degradation under visible light. A variety of characterizations demonstrated that the surface defects greatly reduced the bandgap and enhanced the absorption of visible light. And the recombination of photogenerated electron-hole (e--h+) pairs was suppressed to varying degrees in the modulated TiO2(B) catalysts revealed in the photoelectrochemical analysis. It is necessary to match the band structure of photocatalysts with the frontier orbital of HCHO for achieving effectual photocatalytic oxidation (PCO). Remarkably, the separation and transport of photogenerated carriers were inhibited when excessive metal Cu was doped. The results in this work provide a deeper understanding of the relationship between the surface engineering of TiO2(B)-based catalysts and catalytic performance.

The universal application of wearable strain sensors in various situations for human-activity monitoring is considerably limited by the contradiction between high sensitivity and broad working range. There still remains a huge challenge to design sensors featuring simultaneous broad working range and high sensitivity. Herein, a typical bilayer-conductive structure Ti3C2TxMXene/carbon nanotubes (CNTs)/thermoplastic polyurethane (TPU) composite film was developed by a simple and scalable vacuum filtration process utilizing a porous electrospun thermoplastic polyurethane (TPU) mat as a skeleton. The MXene/CNTs/TPU strain sensor is composed of two parts: a brittle densely stacked MXene upper lamella and a flexible MXene/CNT-decorated fibrous network lower layer. Benefiting from the synergetic effect of the two parts along with hydrogen-bonding interactions between the porous TPU fiber mat and MXene sheets, the MXene/CNTs/TPU strain sensor possesses both a broad working range (up to 330%) and high sensitivity (maximum gauge factor of 2911) as well as superb long-term durability (2600 cycles under the strain of 50%). Finally, the sensor can be successfully employed for human movement monitoring, from tiny facial expressions, respiration, and pulse beat to large-scale finger and elbow bending, demonstrating a promising and attractive application for wearable devices and human–machine interaction.

The objective of this study is to assess the adsorption behavior of C.I. Basic Yellow X-5GL, C.I. Basic Red 13, C.I. Direct Blue 86, C.I. Vat Yellow 2, and C.I. Mordant Black 11 on natural sediment and to identify sediment characteristics that play a predominant role in the adsorption of the dyes. The potentiometric titration experiment is used to investigate acid–base properties of the sediment surface with a constant capacitance surface complexation model. The parameters controlling the sorption such as solution pH and ion strength, as well as the influence of organic carbon and Ca2+ion on the adsorption, are evaluated. It is shown that the titration data can be successfully described by the surface protonation and deprotonation model with the least-squares FITEQL program 2.0. The sorption isotherm data are fitted to the Freundlich equation in a nonlinear form (1/n=0.3–0.9) for all tested dyes. With increasing pH value, the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86 on the sediment decreases, while for C.I. Basic Yellow X-5GL and C.I. Basic Red 13, the extent of sorption slightly increases. In addition, ion strength also exhibits a considerably different effect on the sorption behavior of these dye compounds. The addition of Ca2+can greatly reduce the sorption of C.I. Basic Red 13 on the sediment surface, while it enhances the sorption of C.I. Direct Blue 6. The removal of organic carbon decreases the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86. In contrast, the sorption of C.I. Basic Red 13 and C.I. Basic Yellow X-5GL is obviously enhanced after the removal of organic carbon. The differences in adsorption behavior are mainly attributed to the physicochemical properties of these dye compounds.