A Peierls perspective on mechanisms of atomicfriction

Stick-slip behavior observed from nanoscale asperity friction experiments are often modeled by the one-degree-of-freedom Tomlinson model, which is unable to explain the effects of lattice structure and interface defects, or by molecular simulations which suffer temporal limitations in modeling the velocity- and temperature-dependent frictional behavior. A Peierls-type model developed in this work views the atomic frictional process as the initiation and gliding passage of dislocations with diffused cores on the interface. As a consequence of loss-of-ellipticity instability, the occurrence of stick-slip behavior relies on the interaction among interface slip field, contact stress fields, and existing defects. The friction stress for commensurate interface under large contact area can be approximated from the Rice model of screw-dislocation nucleation from a planar crack tip. The spatially inhomogeneous nature of rate-limiting processes and the coupling effects between contact size and interface incommensurability are successfully determined, which cannot otherwise be tackled in the Tomlinsonmodel.     

Establishment of pressurized liquid extraction followed by HPLC–MS/MS method for the screening of adrenergic drugs,steroids, sedatives,colorants and antioxidants in swine feed

A facile and sensitive multi‐residue detection approach of pressurized liquid extraction following high‐performance liquid chromatography tandem mass spectrometry was established to detect the residues of adrenergic drugs, steroids, sedative, colorant and antioxidant in feed. The conditions employed for pressurized liquid extraction involved acetonitrile/ethyl acetate (1:1, v/v) as the extracting solvent, the temperature 80°C, two cycles and a static time of 10 min. The extraction was followed by a solid‐phase extraction clean‐up step. The separation of samples was done by C₁₈ column with the mobile phase of 5 mM ammonium acetate solution and acetonitrile with 0.1% formic acid. The limits of quantification ranged from 0.03 to 1 μg/kg, limits of detection were in a range of 0.01–0.5 μg/kg, and average recoveries were 70.4–98.6%. The pressurized liquid extraction procedure was optimized and overall method was validated in terms of sensitivity, linearity, selectivity, matrix effect, accuracy, recovery and stability of the target drugs in the pressurized liquid extraction extracts solution. The screening method was proved to be fast, selective, accurate and sensitive for screening drugs.     

Quantitative structure‐retention relationships of the chromatographic retentions of phthalic acid ester contaminants in foods

The harmful health effects caused by phthalic acid esters have been supported from the increasing scientific evidence, developing the efficient methodologies to monitor the levels of phthalic acid esters in various foods become especially important from the aspects of human exposure assessment and their migration mechanistic understanding. In this study, quantitative structure‐retention relationship studies on both the gas and liquid chromatographic retention times of 23 phthalic acid esters were performed by genetic function approximation, and the optimal quantitative structure‐retention relationship models (r² > 0.980, r²_CV > 0.960, and r²_pred > 0.865) passed the statistical tests of cross‐validation, randomization, external prediction, Roy′ r_m² metrics, Golbraikh‐Tropsha′ criteria and applicability domain. The established predictive models elucidate the structural requirements for the retention of phthalic acid esters over different chromatographic columns, which were finally used to predict the retention times of 11 new phthalic acid esters. Hopefully, this work could provide useful guidelines for better understanding and accurate prediction of the retention behavior of undetermined phthalic acid esters when lacking standard samples or under poor experimental conditions, and make the simultaneous identification and quantification of numerous phthalic acid esters possible.     

Choline-based ionic liquids for CO2 capture and conversion

Choline-based ionic liquids(Ch-ILs) with anions possessing interacting sites to attract CO_2 were designed, which could capture CO_2 with capacity 1.0 mol CO_2 per molar IL under ambient conditions. Moreover, this kind of ILs combining with Cu Cl could catalyze the formylation of amines with CO_2/H_2 at 120 °C. Especially, choline imidazolate showed the best performance,affording a series of N-formamides in excellent yields. It was demonstrated that the IL activated CO_2 and the synergistic effect between the IL and Cu Cl resulted in the high activity for catalysing the formylation of amines with CO_2/H_2.     

金红石→萤石TiO2相变的第一性原理计算

利用第一性原理平面波密度泛函理论并结合准谐德拜模型,对TiO₂从金红石结构到萤石结构的相变进行理论研究.依据焓相等原理,得到TiO₂从金红石结构到萤石结构的相变压强为45.32 GPa,并通过吉布斯能的计算发现相变压强随温度的增加而增加,运用拟合的方法估计实验条件下的相变压强(温度为1900-2100K时,P_t=47.604~47.756 GPa).运用等吉布斯能原理,得到零压下从金红石到萤石结构TiO₂的相变温度为2029 K.计算结果与实验及其他理论值相符,并通过准谐德拜模型成功获得相变前后的结构和热力学性质,如相对体积、热膨胀系数、热容和德拜温度等.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/functional exfoliation graphene on carbon paper nanocomposites for supercapacitor electrode

In this work, the commercial carbon paper was firstly peeled in K₂CO₃ solution and then was further treated in a KNO₃ solution to form functional exfoliation graphene (FEG) on the commercial carbon paper. The FEG/carbon paper was characterized by Raman spectra and scanning electron microscopy, confirming that some typical layered fold graphenes were successfully peeled off and stood on the carbon paper matrix. Then, Fe₃O₄ nanoparticles (NPs) were grown on the surface of FEG/carbon paper and the as-prepared Fe₃O₄ NPs/FEG/carbon paper was directly used as supercapacitor electrode. The specific capacitance of Fe₃O₄ NPs/FEG/carbon paper was about 316.07 F g^?1 at a current density of 1 A g^?1. Furthermore, the FEG/carbon papers were also functionalized by benzene carboxylic acid to form FFEG/carbon papers, and then the Fe₃O₄ NPs were grown on the surface of FFEG/carbon paper. The specific capacitance of Fe₃O₄ NPs/FFEG/carbon paper was 470 F g^?1 at a current density of 1 A g^?1, superior to some previous reported results. This work might provide a new strategy to prepare various nanostructures on FFEG/carbon papers for future applications.     

Electrodeposition of polypyrrole on He plasma etched carbon nanotube films for electrodes of flexible all-solid-state supercapacitor

Journal of Solid State Electrochemistry - Flexible and portable supercapacitors have been intensively investigated due to their reliable energy storage performance and promising applications in...     

Exfoliation and Sensitization of 2D Carbon Nitride for Photoelectrochemical Biosensing under Red Light

Two-dimensional carbon nitride (CN) has drawn increasing attention as a conjugated metal-free polymer for photoelectrochemical (PEC) biosensing. However, CN only absorbs ultraviolet and very limited visible light (λ<460 nm), which poses potential risks for biomolecules and also cannot pass through tissue for in vivo detection. Herein, simultaneous exfoliation and functionalization of CN nanosheets (CNNS) with copper phthalocyanine (TsCuPc) simply by mechanical milling, thanks to the delicate π–π interaction between them, is reported. Moreover, due to energy-level matching, an effective donor–acceptor (D-A) interaction with much-improved photocurrent under irradiation with red light (λ>630 nm) was observed for the as-prepared CNNS-TsCuPc. As an example, dopamine in blood was detected by using red light by a CNNS-TsCuPc photoelectrode with uncompromised linear range and detection limit, as well high selectivity. As one of the few successful demonstrations of red-light-responsive PEC sensing systems, this work takes a first step toward future in vivo applications by enriching the optoelectronic properties of CN with task-specific antenna molecules via D-A interaction.     

Highly efficient uranium(VI) removal from aqueous solution using poly(cyclotriphosphazene-co-4,4′-diaminodiphenyl-ether) crosslinked microspheres

Journal of Radioanalytical and Nuclear Chemistry - Radiocarbon and radiocesium were measured on litter fractions (LF) collected on November 19th, 2011 at 40&nbsp;km NW of the FDNPP. The 137Cs...     

Response analysis of the piezoelectric energy harvester under correlated white noise

Nonlinear Dynamics - Energy harvesting of a monostable duffing-type harvester with piezoelectric coupling under correlated multiplicative and additive white noise is investigated in this paper. The...