Ab initio density functional studies of the restructuring of graphene nanoribbons to form tailored single walled carbon nanotubes

A method based on density functional theory calculations is proposed for the preparation of chiral controlled single walled carbon nanotubes (SWCNTs) by tailoring the edges of bi-layered graphene nanoribbons (GNRs). We find that armchair edged bi-layered GNRs are highly stable and need to be compressed to overcome the energy barrier to form zigzag SWCNTs, while the zigzag edged bi-layered GNRs are intrinsically highly unstable and immediately form armchair SWCNTs. We have investigated the rehybridization of orbitals of carbon atoms in the process of nanotube formation. Nanotube formation is found to be assisted by the edge ripples along with the intrinsic edge reactivity of different types of bi-layered GNRs. Utilizing these results we show that it may be possible to produce high specificity chiral controlled SWCNTs and pattern them for nanoscale device applications.     

QSPR studies of polyvinyls by density functional theory

Density functional theory (DFT) calculations are carried out for polyvinyls repeating units at the B3LYP/6-31G(d) level, and the calculated results of E_T, E_int, C_v, S, Q_ii, μ, α and q⁻ are used to predict V (298 K), P_s, F_d, R_LL, χ, H_vsum, U_R and U_H. Multiple linear stepwise regression analysis is used to generate eight more physically meaningful quantitative structure-property relationship (QSPR) models having correlation coefficient R of 0.996 for V (298 K), 0.998 for P_s, 0.997 for F_d, 0.997 for R_LL, 0.997 for χ, 0.992 for H_vsum, 0.992 for U_R and 0.991 for U_H, and the conclusions are in consistence with theoretical analysis. Investigated results indicate QSPR models given here are easy to apply and have good predictive capability.     

Ab initio studies of complexation of anions to neutral species

The complexation of simple anions (F⁻ and Cl⁻) to different neutral species, anion-coordinating agents, has been studied using electronic structure calculations. The obtained changes in the equilibrium constants for salt dissolution reactions in different typical electrolyte systems are reported. In addition the lithium ion affinities of the obtained anionic complexes have been calculated. Using the present results we discuss strategies for future usage of anion complexing agents and make recommendations of salt and agent combinations for better lithium battery electrolyte performance.     

Time-dependent density functional theory for nonadiabatic processes

Time-dependent density functional theory (TDDFT) is a general and robust method allowing the study of electron dynamics whether induced by nuclear motion or by external fields. We give a brief overview of the theory and some numerical methods together with recent applications stressing the generality and wide applicability of the method. We also discuss recent attempts to extend the present TDDFT by incorporating memory terms into the exchange correlation potentials.     

经典密度泛函理论在双电层超级电容器研究中的应用

提高储能密度是目前超级电容器研究的重点,它取决于电极材料与电解液界面结构。本文介绍了经典密度泛函理论（CDFT）研究固液界面结构的基本原理以及在多孔电极材料中电解液溶液的热力学和动力学性质研究等进展。CDFT是一种基于统计力学的理论方法,被广泛应用于表界面效应、吸附、溶解等研究,在保证相同计算精度的前提下,具有比分子模拟更高的计算效率。CDFT可以系统地研究多孔材料孔径、孔几何形貌、表面官能团,电解液离子大小、化合价、组成以及溶剂种类、浓度等因素对超级电容器性能的影响,进一步发展考虑反应-传递性质的CDFT,可以为设计新型电极材料和筛选电解液提供理论依据。     

Bactericidal activity of certain fatty acids

Fatty acids in the C₉ to C₁₂ range are bactericidal to a number of different organisms, and this activity is markedly enhanced with increasing acidity. Optimum bactericidal activity toStaphylococcus aureus was exhibited by undecylic acid. Since the activity is of the same order as that of the quaternary ammonium germicides in alkaline solution, an explanation for both types of germicidal activity is presented in which the bacteria or some protein essential to the bacteria are considered to be “suffocated” by a “coating” of fatty groups in chemical combination with the protein. The application of these findings to bactericidal activity encountered in rancid fats is discussed briefly in connection with the oxidative degradation of oleic acid derivatives to pelargonic acid. In addition, the possible usefulness of the bactericidal activity as a microbiological assay method for certain fatty acids is pointed out.     

酚酸结构对酚酸-g-聚甘露糖醛酸抗氧化性能的影响

以海藻酸钠水解产物聚甘露糖醛酸(PM)为原料,通过聚甘露糖醛酸-乙二胺(PM-EDA)中间体与酚酸接枝共聚,制备了8种PM的酚酸(PA)接枝共聚物酚酸-g-聚甘露糖醛酸(PA-g-PM),并探究了PA结构对8种PA-g-PM抗氧化活性的影响。在n_PM:n_EDA=1:1.5,PM与两种活化剂碳二亚胺(EDC)、N-羟基琥珀酰亚胺(NHS)的摩尔比1:2:1,活化0 h,pH 8.0条件下,反应24 h,获得最高取代度(17.27%)的PM-EDA。PM的PA-g-PM接枝率在4.171±0.16 ~ 8.880±0.32 mg GA/g之间。UV-vis、FT-IR、XRD表征证实酚酸已成功接枝到PM上获得PA-g-PM。相比PM,8种PA-g-PM的对DPPH的清除率和对铁的还原力均显著提升。PA-g-PM的抗氧化性能与其中的酚羟基个数呈正相关关系,对位酚羟基PA-g-PM的抗氧化性能优于邻位酚羟基PA-g-PM的抗氧化性能,PA-g-PM中的酚羟基被甲氧基取代其抗氧化性能减弱。以期本研究结果为海藻酸钠在食品、化妆品、医药等行业高值开发利用奠定理论基础。     

测氧法研究受阻酚抗氧剂的抗氧化活性及反应动力学

采用测氧法考察了4种市售受阻酚抗氧剂的抗氧化活性,同时对其清除ROO·反应进行了动力学分析。结果表明:4种受阻酚抗氧剂对ROO·均具有良好的清除作用,并且抗氧化活性随着酚羟基浓度增加而增大。在同等的酚羟基浓度下,抗氧剂的抑制速率常数kinh值从大到小的顺序为抗氧剂1098、抗氧剂BHT、抗氧剂1010、抗氧剂1076。抗氧剂的抗氧化活性与功能基团的个数和对位取代基的供电性密切相关,酚胺复合型抗氧剂体现出更高的抗氧化活性。     

反应密度泛函理论的构建与初步应用

提高化学反应的选择性和转化率是发展绿色化学的重要内容。大部分化学反应都在溶液中发生,溶剂对于反应速率、平衡过程甚至反应机理都有重要的影响。溶剂效应对化学反应影响的理论研究比较缺乏。综述了近年来发展的理论模型及最近本课题组提出的反应密度泛函理论,分别介绍了反应密度泛函理论在水相、有机相、界面体系和限域体系中的应用,分析了不同反应溶剂结构对化学反应自由能分布的影响,总结了溶剂效应的影响机制,最后展望了自洽反应密度泛函理论的构建、反应-扩散耦合研究、聚合物反应密度泛函理论及反应密度泛函理论在反应溶剂筛选、界面反应和电解液设计中的应用。     

多乙烯多胺桥联受阻酚类抗氧剂的合成及其清除DPPH·性能

以二乙烯三胺和三乙烯四胺为桥联基,β-(3,5-二叔丁基-4-羟基苯基)丙酰氯为抗氧化功能基团,通过酰胺化缩合反应合成了两类具有不同对位桥联基团的受阻酚类抗氧剂。采用傅里叶红外光谱和核磁共振氢谱证实了合成的多乙烯多胺桥联受阻酚类抗氧剂的化学结构。DPPH法研究了多乙烯多胺桥联受阻酚类抗氧剂清除自由基的性能,并探索了酚羟基个数和对位桥联基结构对受阻酚类抗氧剂清除自由基性能的影响。结果表明,多乙烯多胺桥联受阻酚类抗氧剂具有良好的清除DPPH·能力,且随着抗氧剂分子中酚羟基个数的增加,清除DPPH·的活性增加,分子中含有4个酚羟基的三乙烯四胺受阻酚类抗氧剂的抗氧化效率（AE）达到2.65×10^-2 L/(mol·s)。对位桥联基结构对受阻酚类抗氧剂清除DPPH·能力有较大影响,季戊四醇为桥联基的受阻酚类抗氧剂1010清除DPPH·能力最强,其抗氧化效率（AE）为3.08×10^-2L/(mol·s);乙二胺为核的1.0代树枝状受阻酚类抗氧剂清除DPPH·能力最弱,其抗氧化效率（AE）为2.60×10^-2 L/(mol·s)。     

Trickle-bed CFD studies in the catalytic wet oxidation of phenolic acids

An Euler-Euler computational fluid model was developed successfully for the hydrodynamic prediction of a trickle-bed reactor (TBR) designed for advanced wastewater treatment facilities. Catalytic wet air oxidation of phenolic acids was simulated in a TBR by means of computational fluid dynamic (CFD) in the temperature range and pressures . The hydrodynamic model validation was accomplished through the comparison of simulated pressure drop and liquid holdup with experimental data from the literature. In a broad range of gas and liquid flows studied (G=0.10-0.70 and ) at different operation conditions, CFD demonstrated the considerable effect of operating pressure in pressure drop, whereas a minor influence was detected for the liquid holdup. CFD runs were then performed for the catalytic wet air oxidation of aqueous phenolic acids solution. The reactor behaviour was analysed by means of total organic carbon profiles which reflected the influence of temperature, pressure, gas-liquid flows and initial pollutant concentration.     

Ab initio crystal structure and charge density distribution of a highly energetic 2,4-dinitrobenzoic acid molecule

The energetic parameters, such as density, bond strength, and sensitivity of explosives/ propellants decide their detonation power and safety. Experimentally, optimization of these parameters is found to be a difficult task; therefore, prior to synthesis, it makes sense to estimate these parameters by computational techniques, ab initio crystal structure prediction, and quantum chemical calculation coupled with the AIM analysis. Here, we predict the density of an energetic 2,4-dinitrobenzoic acid (DNBA) molecule from different ab initio crystal structure models and validate the results through comparisons with experimental data. The bond topological characterization reveals that the C NO₂ bonds are the weakest bonds and are identified as sensitive bonds in the molecule. The bond sensitivity is estimated from Murray’s method. The impact sensitivity of this molecule is also calculated. Large negative electrostatic potential regions are found near the NO₂ and carboxylic groups, which are the reactive sites of the molecule.     

Reassessment of the antioxidant activity of conjugated linoleic acids

The anticarcinogenic effect of conjugated linoleic acids (CLA) has been attributed to their antioxidant activity. Strong evidence is lacking, however, to substantiate that CLA is an antioxidant. The objective of this study was, therefore, to test whether CLA is an antioxidant or a prooxidant in canola oil. The oxidation was conducted at 90°C by monitoring oxygen uptake and changes in linoleic acid and α-linolenic acid. Free CLA and CLA methyl ester (CLAME) accelerated lipid oxidation in canola oil. The prooxidant activity of CLA and CLAME was dose-dependent at concentrations ranging from 0.1 to 1.0% in canola oil heated at 90°C. CLA-containing triacylglycerol, however, was neither an antioxidant nor a prooxidant. Under the present experimental conditions, CLA was not an antioxidant in fats and oil.     

Insights into homogeneous catalysis from first-principles theory: density functional studies of inorganic cobalt complexes

Density functional theory (DFT) has been used to predict geometries, energies and spin states of a series of inorganic cobalt complexes containing the geometry-constraining Tp (tris(pyrazolyl borate)) ligand. For example, the carbonyl, TpCoCO, is a stable 16-electron compound with an unusual asymmetric geometry. This molecule is the structural and electronic analog of an unstable intermediate in C–H bond activation. DFT studies of TpCoCO permit detailed comparisons of theory to experiment, and a rationale for the structure that applies to unstable species as well. More recent work has focused on reactive molecules, including (TpCo)₂O₂ complexes (with 36 heavy atoms) that may be useful in catalyzing alkane oxidation. DFT provides a useful guide to the feasibility of proposed oxidation mechanisms.     

Experimental and density functional theory studies on PtPb/C bimetallic electrocatalysts for methanol electrooxidation reaction in alkaline media

Carbon-supported bimetallic Pt_mPb₁ (m = 1, 2, 3) electrocatalysts with different Pt/Pb atomic ratios were synthesized by a polyol method. The X-ray diffraction results reveal that a PtPb alloy formed in the Pt_mPb₁/C electrocatalysts. TEM images show that the PtPb nanoparticles distribute uniformly on the carbon support, and are about 4–5 nm in size. The Pt_mPb₁/C bimetallic catalysts show superior activities toward methanol electrooxidation reaction (MOR) than the Pt/C in alkaline media. Both CO stripping measurements and density functional theory studies reveal that CO adsorption decreased significantly on the Pt_mPb₁/C bimetallic catalysts compared with on pure Pt, which may offer an explanation for the enhanced MOR activity of the Pt_mPb₁/C bimetallic catalysts.