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Air-Stable Titanium Carbide MXene Nanosheets for Corrosion Protection
No full textMXene materials have drawn extensive scientific interest in catalysis, batteries, purification, and electromagnetic interference shielding fields; however, their anticorrosion performance is rarely explored mainly because MXene nanosheets are prone to be oxidized under ambient conditions. Herein, we prepared oxidationresistant and highly stable titanium carbide (Ti3C2Tx) MXene sheets through noncovalent functionalization between MXene and an ionic liquid (IL). The resultant IL@MXene nanosheets were used as a smart barrier enhancer of waterborne epoxy (WEP) to improve the anticorrosion performance of coatings. The impedance modulus of the IL@MXene-WEP coatings with a thickness of 13 mu m increased by 1-2 orders of magnitude compared to that of the neat WEP coating, which was supported by potentiodynamic polarization curves and electrochemical impedance spectroscopy measurements. The morphologies of steels protected by the IL@MXene-WEP coatings exhibited less corrosion than the neat WEP, suggesting a satisfactory anticorrosion performance enhancement by the coating. Furthermore, the self-healing properties of the IL@MXene-WEP coating were confirmed using the scanning vibrating electrode technique. Its enhanced protection performance was attributed to the synergistic effects of the exceptional barrier property endowed by well-dispersed MXene nanosheets and the self-repairing property caused by IL passive films. Our work provides a strategy for the design and preparation of MXene smart anticorrosion coatings
Robust covalent organic frameworks with tailor-made chelating sites for synergistic capture of U(vi) ions from highly acidic radioactive waste
No full textA synergistic strategy for enhancing U(vi) capture under highly acidic conditions (2 M HNO3) by radiation resistant phosphonate-functionalized two-dimensional covalent organic frameworks with tailor-made binding sites bearing a strong affinity was described. The combination of the radiation resistant characteristic with a strong acid-resistant property endows COFs with practical capabilities for actinide capture from real radioactive liquid waste
Dual cascade isothermal amplification reaction based glucometer sensors for point-of-care diagnostics of cancer-related microRNAs
No full textThe practical use of a point-of-care (POC) device is of particular interest in performing liquid biopsies related to cancer. Herein, taking advantage of the practical convenience of a commercially available personal glucose meter (PGM), we report a convenient, low-cost and sensitive detection strategy for circulating microRNA-155 (miRNA155) in human serum. First, miRNA155 in serum triggers the catalyzed hairpin assembly (CHA) reaction, and then the CHA product is specifically captured by the peptide nucleic acid (PNA) probes attached to the surface of a 96-well plate, which in turn triggers the hybridization chain reaction (HCR), resulting in the local enrichment of invertase. Next, introduction of a substrate (sucrose) for the invertase results in the generation of glucose, which can be detected by a PGM. In this sensor, neutrally charged PNA (12 nt) is more likely to hybridize with the CHA products than with the negatively charged DNA in kinetics, which improves the detection sensitivity and specificity. Due to the synergistic isothermal amplification reaction between CHA and HCR, the sensor is able to achieve a broad dynamic range (from 1 fM to 10 nM) with a detection limit down to 0.36 fM (3 orders of magnitude lower than that without HCR) and is capable of distinguishing single-base mismatched sequences. Thus the convenient, sensitive, robust and low-cost PGM sensor makes on-site nucleic acids detection possible, suggesting its great application prospect as a promising POC device in cancer diagnostics
Atomic modeling of the segregation of vacancies on < 111 > dislocations in alpha-iron by diffusive molecular dynamics simulations
No full textThe interaction between dislocations and vacancies at finite temperature is crucial for many physical properties and phenomena in materials, such as vacancy segregation, strengthening effect, dislocation motion, and crystal plasticity. Conventional dislocation-vacancy interaction models use approximations based on elasticity theory and assumption that transition state energy can be deduced from the binding energy of the vacancies. The long-term vacancy diffusion near dislocation and the change of dislocation core induced by vacancy segregation are still difficult to capture. In this paper, we present the theoretical study on diffusion and segregation properties of vacancies near edge or screw dislocation on slip planes of {110}, {112} and {123} in bcc iron. The calculations are performed with the distribution of vacancy concentration and dislocation-vacancy interaction energy as a function of distance from dislocation core using diffusive molecular dynamics (DMD). Meanwhile, the accompanying effects of the interaction on vacancy segregation, dislocation motion, and crystal plasticity are discussed. The vacancy diffusion near dislocation is a process highly anisotropic and inter-correlated towards equilibrium. The interaction of vacancies with the tensile stress field of edge dislocations is numerically stronger than that with the pure shear stress field of screw dislocations. The Peierls stress are calculated to reflect the effect of the vacancy segregation on dislocation motion. The slip planes of dislocations have a significant influence on this interaction. With the slip planes changing from {110} to {123} to {112}, the absorption intensity of dislocation to vacancy and the ranges of the effective interaction region of both edge and screw dislocation decrease while the ranges of absorption region increases gradually. In addition, vacancy segregation produces a regulatory mechanism for the structure of dislocation core and promotes the transformation of dislocations on different slip planes to a more stable intermediate structure. This study visually presents the evolution of vacancies near dislocation, providing fundamental insights on the vacancy transport mechanisms which are essential for understanding dislocation-vacancy interaction, dislocation motion and plasticity of metallic materials. (C) 2020 Elsevier B.V. All rights reserved
Theoretical prediction of chiral actinide endohedral borospherenes dagger
No full textRecently, the observation of the first axially chiral borospherenes (B-39(-)) enriched the members of the boron cluster family, and opened the door to axially chiral boron cages. Herein, we theoretically predicted a series of chiral borospherenes by actinide metal (An) encapsulation, which are new chiral members of the borospherene family. Theoretical calculations demonstrate that the C-2 neutral and charged Ac- and Th-B-39 boron clusters (Ac@B-39, [Ac@B-39](2+), and Th@B-39, [Th@B-39](3+)) are the most stable structures, and each borospherene possesses degenerate enantiomers, in accordance with the chiral borospherenes B-39(-). In contrast, the global minimum structures of Cf embedded borospherenes have no symmetry (C-1). All the chiral actinoborospherenes [An@B-39](n+) (An = Ac, n = 0, 2; An = Th, n = 0, 3) possess high formation energies, especially C-2 [Th@B-39](3+). Bonding analysis shows that each complex of [Ac@B-39](n+) and [Th@B-39](n+) has the characteristic of sigma + pi double delocalization, and the Th-B bonds possess relatively higher covalency than the Ac-B bonds, resulting in the higher formation energy of C-2 [Th@B-39](3+). Therefore, the covalent character of An-B bonding may be essential for the formation of these chiral actinoborospherenes. This work extends the chiral borospherenes to actinide metal-doped chiral borospherenes, and sheds light on the design of chiral metalloborospherenes
Two-Dimensional Carbonitride MXenes as an Efficient Electrocatalyst for Hydrogen Evolution
No full textOwing to their excellent thermostability, superior electrical conductivity, and tunable surface chemistry, two-dimensional transition-metal carbides, nitrides, and carbonitrides (MXenes) are highly desirable as potential electrocatalysts for the hydrogen evolution reaction (HER). However, while nearly 30 MXenes have already been synthesized, less carbonitride MXenes were experimentally reported so far, yet their potential promising electrochemical properties are greatly expected. Here, we explored the thermodynamically favorable configurations of Mo-2(CN)T-x (T = F, OH, and O) with a mixture of functional groups under various electrochemical environments. It is revealed that the O*/OH*-terminated Mo-based carbonitride MXenes exhibit the most stable state under ambient conditions. By exploring the catalytic performance of HER for various Mo-2(CxN1-x)T-2 at different ratios of C and N atoms, we found that three optimal C/N ratios with 0.5 ML O* and 0.5 ML OH* showed good catalytic activity of HER, comparable to Pt metals. Further investigations of strain-tunable HER of the cofunctionalized Mo-2(CxN1-x)OOH suggest that the biaxial strain may effectively modify the Delta G(H*) of HER, which can be ascribed to the asymmetrical surface topology and charge polarization. These results provide not only a strategy to synthesize carbonitride MXenes with various surface functionalizations but also a feasible solution to design by chemical doping and strain engineering
Self-assembled membrane-polymer nanoparticles of top-notch tissue tolerance for the treatment of gastroesophageal reflux disease
No full textControlled release technology has continuously attracted attention as a strategy to deliver active agents to specific internal body regions with attendant cost-effectiveness among other intriguing merits. Here, drug-loaded nanoparticles (NPs) are synthesized for ultimate application in the treatment of gastroesophageal reflux disease (GERD), leveraging the benefits of controlled release strategy. To achieve this, eggshell membranes (ESMs) were extracted and combined with chitosan (CHS) to rationally obtain self-assembled CHS-ESM NPs that served as a novel nanocarrier to effectively compartmentalize a GERD-therapeutic drug famotidine (FTD) and form self-assembled FTD@CHS-ESM NPs. Advantageously, the proof-of-concept FTD@CHS-ESM NPs offer superlative tissue tolerance. The cumulative FTD release is 89% after 12 h at pH 1.2, suggesting the capability of FTD@CHS-ESM NPs for effectual controlled drug release; a testimonial of the effective compartmentalization of FTD in the nanocarrier. Furthermore, the release of FTD from the FTD@CHS-ESM NPs is best described by Higuchi square root model, in a non-Fickian diffusional release mechanism (n = 0.584 and 0.582 in pH 1.2 and pH 6.8, respectively). The drug release system demonstrated in this work, therefore, holds strong promise for the oral nanomedical treatment of GERD in vivo, and promotes the rational synthesis of organic-based biocompatible nanomaterials for biomedical application. [GRAPHICS]
High-performance La-0.5(Ba0.75Ca0.25)(0.5)Co0.8Fe0.2O3-delta cathode for proton-conducting solid oxide fuel cells
No full textLa-0.5(Ba0.75Ca0.25)(0.5)Co0.8Fe0.2O3-delta, a simple perovskite cathode material with high electrical conductivity (940 S cm(-1) at 600 degrees C) and impressive surface catalytic activity, was prepared and used in proton-conducting solid oxide fuel cells. As its thermal expansion coefficient is higher than that of the electrolyte material BaZr0.1Ce 0.7Y0.1Yb0.1O3-delta, they were combined and used as a composite cathode. The crystal structure, chemical compatibility, electrical conductivity, cell performance, and the oxygen reduction reaction of the cathode material were explored, and we found that the single fuel cell developed with the composite cathode achieved excellent electrochemical performance, with both a low polarization resistance and high peak power density (0.044 Omega cm(2) and 1102 mW cm(-2 )at 750 degrees C, respectively). Outstanding stability was also achieved, as indicated by a long-term 100-h test. Additionally, the rate-limiting steps of the oxygen reduction reaction were the oxygen adsorption, dissociation, and diffusion processes. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Prototype system of noninterferometric phase-contrast computed tomography utilizing medical imaging components
No full textGrating-based x-ray phase-contrast imaging has been demonstrated to provide more information and higher-contrast images for low-Z soft tissues, compared with conventional absorption-based imaging. However, the existing Talbot-Lau phase-contrast devices are operated in either a two- or three-dimensional mode at low energy with a small field of view and long exposure time. This is because of coherence limitations, difficulties in fabricating high aspect ratio gratings, and the slow readout speed of the detector. For preclinical or even clinical applications, a variable x-ray energy, a large field of view, and fast phase-contrast computed tomography (CT) devices are desirable. The noninterferometric grating-based phase-contrast imaging method is a good candidate, as it relaxes requirements on gratings, including grating period and aspect ratio. Based on the noninterferometric imaging principle, we constructed a prototype phase-contrast CT system, at the National Synchrotron Radiation Laboratory of the University of Science and Technology of China, with medical imaging components. This prototype system enables a large field of view and fast phase-contrast CT imaging under medical imaging energies. In this paper, the prototype system and preliminary experimental results are reported, and possible optimization for forthcoming work is also discussed