对称向量拟均衡问题有效解的存在性

利用标量化方法建立对称向量拟均衡问题有效解的存在性定理。作为标量化方法的应用，利用这一方法得到向量变分不等式和拟向量变分不等式有效解的存在性定理。     

Co3+-Rich Na1.95CoP2O7 Phosphates as Efficient Bifunctional Catalysts for Oxygen Evolution and Reduction Reactions in Alkaline Solution

Implementing sustainable energy conversion and storage technologies is highly reliant on crucial oxygen electrocatalysis, such as the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). However, the pursuit of low cost, energetic efficient and robust bifunctional catalysts for OER and ORR remains a great challenge. Herein, the novel Na-ion-deficient Na_2−xCoP₂O₇ catalysts are proposed to efficiently electrocatalyze OER and ORR in alkaline solution. The engineering of Na-ion deficiency can tune the electronic structure of Co, and thus tailor the intrinsically electrocatalytic performance. Among the sodium cobalt phosphate catalysts, the Na_1.95CoP₂O₇ (NCPO5) catalyst exhibits the lowest ΔE (E_J10,OER−E_J−1,ORR) of only 0.86 V, which favorably outperforms most of the reported non-noble metal catalysts. Moreover, the Na-ion deficiency can stabilize the phase structure and morphology of NCPO5 during the OER and ORR processes. This study highlights the Na-ion deficient Na_2−xCoP₂O₇ as a promising class of low-cost, highly active and robust bifunctional catalysts for OER and ORR.     

Developing the Low-Temperature Oxidation Mechanism of Cyclopentane: An Experimental and Theoretical Study

At present, the reactivity of cyclic alkanes is estimated by comparison with acyclic hydrocarbons. Due to the difference in the structure of cycloalkanes and acycloalkanes, the thermodynamic data obtained by analogy are not applicable. In this study, a molecular beam sampling vacuum ultraviolet photoionization time-of-flight mass spectrometer (MB-VUV-PI-TOFMS) was applied to study the low-temperature oxidation of cyclopentane (CPT) at a total pressure range from 1–3 atm and low-temperature range between 500 and 800 K. Low-temperature reaction products including cyclic olefins, cyclic ethers, and highly oxygenated intermediates (e. g., ketohydroperoxide KHP, keto-dihydroperoxide KDHP, olefinic hydroperoxides OHP and ketone structure products) were observed. Further investigation of the oxidation of CPT – electronic structure calculations – were carried out at the UCCSD(T)-F12a/aug-cc-pVDZ//B3LYP/6-31+ G(d,p) level to explore the reactivity of O₂ molecules adding sequentially to cyclopentyl radicals. Experimental and theoretical observations showed that the dominant product channel in the reaction of CPT radicals with O₂ is HO₂ elimination yielding cyclopentene. The pathways of second and third O₂ addition – the dissociation of hydroperoxide – were further confirmed. The results of this study will develop the low-temperature oxidation mechanism of CPT, which can be used for future research on accurately simulating the combustion process of CPT.     

Emission behavior of naphthalimide-coumarin cassette

ABSTRACT

In this contribution, a dye (C₈-alkyl substituted Naphthalimide-Coumarin, CNC) with naphthalimide and coumarin incorporated together with -NHN = bridge unit. The compound was fully characterized by NMR and HRMS spectroscopic techniques. Highly emissive character was investigated in detail in various polar environments. The emission maximum varied from 430 to 470 nm. In polycarbonate film, CNC is also highly emissive with 560 nm emission peak. While in sold, the emission maximum was further shifted to 580 nm due to the more tightly packing mode than that in film. The C₈-alkyl substitution enhances the solubility of CNC and also contributes most to its solid emission.     

Calculation of Ionization,Excitation and Electron Capture Cross Sections for Be4++H(2s, 2p) Collisions

A computational study of Be⁴⁺+H(2s, 2p) collisions has been carried out employing the Classical Trajectory Monte Carlo (CTMC) method for the impact energy range from 20 keV/u to 1000 keV/u. The integral n partial cross sections for H(n) excitation and Be³⁺(n) electron capture and, the total ionization and electron capture cross sections are calculated and compared to recent semiclassical results. A general good agreement is observed for the n partial and total electron capture and ionization cross sections. The comparative study of the three inelastic processes show no significant differences between both excited targets.     

Interactions of DNA with graphene and sensing applications of graphene field-effect transistor devices: A review

Graphene field-effect transistors (GFET) have emerged as powerful detection platforms enabled by the advent of chemical vapor deposition (CVD) production of the unique atomically thin 2D material on a large scale. DNA aptamers, short target-specific oligonucleotides, are excellent sensor moieties for GFETs due to their strong affinity to graphene, relatively short chain-length, selectivity, and a high degree of analyte variability. However, the interaction between DNA and graphene is not fully understood, leading to questions about the structure of surface-bound DNA, including the morphology of DNA nanostructures and the nature of the electronic response seen from analyte binding. This review critically evaluates recent insights into the nature of the DNA graphene interaction and its affect on sensor viability for DNA, small molecules, and proteins with respect to previously established sensing methods. We first discuss the sorption of DNA to graphene to introduce the interactions and forces acting in DNA based GFET devices and how these forces can potentially affect the performance of increasingly popular DNA aptamers and even future DNA nanostructures as sensor substrates. Next, we discuss the novel use of GFETs to detect DNA and the underlying electronic phenomena that are typically used as benchmarks for characterizing the analyte response of these devices. Finally, we address the use of DNA aptamers to increase the selectivity of GFET sensors for small molecules and proteins and compare them with other, state of the art, detection methods.     

Highly charged ion induced nanostructures at surfaces by strong electronic excitations

Nanostructure formation by single slow highly charged ion impacts can be associated with high density of electronic excitations at the impact points of the ions. Experimental results show that depending on the target material these electronic excitations may lead to very large desorption yields in the order of a few 1000 atoms per ion or the formation of nanohillocks at the impact site. Even in ultra-thin insulating membranes the formation of nanometer sized pores is observed after ion impact. In this paper, we show recent results on nanostructure formation by highly charged ions and compare them to structures and defects observed after intense electron and light ion irradiation of ionic crystals and graphene. Additional data on energy loss, charge exchange and secondary electron emission of highly charged ions clearly show that the ion charge dominates the defect formation at the surface.     

Low‐memory iterative density fitting

A new low‐memory modification of the density fitting approximation based on a combination of a continuous fast multipole method (CFMM) and a preconditioned conjugate gradient solver is presented. Iterative conjugate gradient solver uses preconditioners formed from blocks of the Coulomb metric matrix that decrease the number of iterations needed for convergence by up to one order of magnitude. The matrix‐vector products needed within the iterative algorithm are calculated using CFMM, which evaluates them with the linear scaling memory requirements only. Compared with the standard density fitting implementation, up to 15‐fold reduction of the memory requirements is achieved for the most efficient preconditioner at a cost of only 25% increase in computational time. The potential of the method is demonstrated by performing density functional theory calculations for zeolite fragment with 2592 atoms and 121,248 auxiliary basis functions on a single 12‐core CPU workstation. © 2015 Wiley Periodicals, Inc.     

电子功能外延薄膜的电沉积

电沉积作为一种在温和条件下从溶液中合成材料的技术已被广泛应用于在导体和半导体基底表面合成各种功能材料。电沉积一般由人为施加于基底的电刺激（如：施加电位/电流）来触发。这种电刺激通过氧化或还原靠近基底表面的溶液层内部的离子、 分子或配合物从而使该溶液层偏离其热力学平衡状态,随后引起目标产物在基底表面的沉积。在电沉积过程中, 许多实验参数都可能从不同的方面对沉积物的物化性质造成影响。迄今为止,已通过电沉积制备出多种单质（包括金属和非金属单质）、 化合物（例如：金属氧化物、金属氢氧化物、 金属硫化物等）以及复合材料。电沉积制备的这些材料大多为多晶、 织构或外延薄膜的形式。其中, 外延薄膜是一种具有特定的面外和面内晶体生长取向且其晶体取向受基底控制的类单晶薄膜。由于外延薄膜中高度有序的原子排列,它们常呈现出独特的电磁性质。本文总结了常见的电沉积合成路线及影响沉积物外延生长的关键实验因素。此外, 本文简要介绍了用于表征外延薄膜的技术。最后, 本文还讨论了一些采用电沉积制备的具有特殊电子、 电磁及光电特性的功能外延薄膜。     

Catalytic chain transfer polymerization of isobutylene: The role of nucleophilic impurities

Fast polymerization of isobutylene (IB) initiated by tert‐butyl chloride using ethylaluminum dichloride·bis(2‐chloroethyl) ether complex (T. Rajasekhar, J. Emert, R. Faust, Polym. Chem. 2017, 8, 2852) was drastically slowed down in the presence of impurities, such as propionic acid, acetone, methanol, and acetonitrile. The effect of impurities on the polymerization rate was neutralized by using two different approaches. First, addition of a small amount of iron trichloride (FeCl₃) scavenged the impurity and formed an insoluble · impurity complex in hexanes. The polymerization rate and exo‐olefin content were virtually identical to that obtained in the absence of impurities. Heterogeneous phase scavenger (FeCl₃) exhibited better performance than homogenous phase scavengers. In the second approach, conducting the polymerization in wet hexanes, the fast polymerization of IB was retained in the presence of impurities with a slight decrease in exo‐olefin content. ¹H NMR studies suggest that nucleophilic impurities are protonated in the presence of water, and thereby neutralized. Mechanistic studies suggest that the rate constant of activation (k_a), rate constant of propagation (k_p), and rate constant of β‐proton elimination (k_tr) are not affected by the presence of impurities. To account for the retardation of polymerization in the presence of impurities, delay of proton transfer to monomer in the chain transfer step is proposed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3697–3704