General solution for Poisson-Boltzmann equation in semiinfinite planar symmetry

Self-assembled multilayer thin films have been prepared on Au substrate by alternate surface derivatization with L-cysteine hydrochloride and cupric perchlorate. The layer-by-layer structure at each step of multilayer formation was investigated by X-ray photoelectron spectroscopy. The measurements indicate that there are two structure modes in the multilayers. One is that Cu(2+) sandwiches between two amino acid groups. The other one is that Cu(+) is bonded through disulfide and thiolate. This process is also confirmed by cyclic voltammetry of Cu ion at different self-assembled multilayers. Steps further on will lead to repeated multilayer films.     

Time-dependent density functional theory calculations of the photoabsorption of fluorinated alkanes

Time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of fluorinated alkanes have been performed. The TD-DFT method with the non-local B3LYP potential yields transition energies for the methanes, which are smaller by about 10% as compared to the experimental values. An empirical linear correlation was found between the calculated and experimental transition energies both at the B3LYP/DZ+Ryd(C, F) and B3LYP/cc-pVTZ+Ryd(C, F, H) levels for a total of 19 transitions of the fluorinated methanes with linear correlation coefficients of 0.987 for the former and 0.988 for the latter. This empirical correlation for fluorinated methane molecules is found to agree well with the previously obtained empirical correlations between calculated and experimental values for non-fluorinated molecules. The results show that a single empirical-correlation relationship can be used for both non-fluorinated and fluorinated molecules to predict transition energies. This linear relationship is then used to predict the photoabsorption spectra of ethane, propane, butane, and partially and fully fluorinated derivatives. A key result of these calculations is the dominance of Rydberg transitions in the spectral region of interest.     

A vanadium(IV) phosphite with a pillared layered structure: hydrothermal synthesis and characterization of (VO)4(4,4'-bpy)2(HPO3)4

A novel vanadium(IV) phosphite, (VO)(4)(4,4'-bpy)(2)(HPO(3))(4), was hydrothermally synthesized and characterized by single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system with the space group C2/c and cell parameters a = 35.970(3) A, b = 15.9400(13) A, c = 10.7681(7) A, beta = 101.073(4) degrees, and Z = 8 with R(1) = 0.0482. The structure of the compound consists of trigonal bipyramidal [VO(4)N] and pseudopyramidal [HPO(3)] blocks, which are connected by corner-sharing, to form vanadium phosphite layers in the bc plane. These layers are further linked through 4,4'-bpy pillars, generating a 3D framework. Thermogravimetric analysis and magnetic susceptibility data for this compound are given.     

Maximum overlap symmetry molecular orbital model

This paper provides a brief and systematic presentation of the basic principle and method of the maximum overlap symmetry molecular orbital (MOSMO ) model and its application to simplification of molecular orbital calculation and to calculation of molecular structures and properties, together with some new results about the MOSMO calculation and new insights concerning the further extension of the principle and method. It has been shown that the theoretical method of the MOSMO model is very simple, reliable, and useful and can be employed to study the structure–property relation in even very large molecular systems. The numerical results obtained from the MOSMO calculation on various semiempirical molecular orbital approximation levels show that when the same parametrization, such as one of those employed in EHMO , CNDO /2, and HMO methods, is adopted, the MOSMOS are very close to the canonical molecular orbitals obtained from the customary LCAO method and the MOSMO calculation requires less computing time than does the LCAO method. The MOSMO calculation can be used for rapidly obtaining reasonably good molecular geometries, vibrational frequencies, and other properties of molecules by employing a simple improved semiempirical parametrization. Equilibrium geometries, vibrational frequencies, and other results are in good agreement with the experimental data and the results obtained from ab initio molecular orbital calculation. The basic calculational procedure of the MOSMO model can be extended further and has been employed to give some new results, to propose some new theoretical schemes and principles, and to introduce some new interesting theoretical problems that deserve to be studied further.     

铁体系催化丁二烯聚合的研究——Ⅴ.ESR、NMR和IR研究聚合机理

本文用ESR、¹H-NMR及IR研究了Fe(phen)Cl₃-(i-C₄H₉)₃Al体系催化丁二烯聚合的机理。ESR谱表明,聚合活性中心上的铁为Fe(Ⅱ)。同时观察到自由基的信号,为其还原历程提供了证据。体系中不存在丁二烯时有很宽的ESR信号(ΔH_pp=900G)、加入丁二烯时可以观察到一窄信号(ΔH_pp=50G),二者有明显区别。提出了Fe(phen)Cl₃-(i-C₄H₉)₃Al体系催化丁二烯聚合的反应机理,两个体系的¹H-NMR和IR谱图的比较证实了这个机理。     

Heterogeneous Hydrogenation with Hydrogen Spillover Enabled by Nitrogen Vacancies on Boron Nitride-Supported Pd Nanoparticles

Heterogeneous hydrogenation with hydrogen spillover has been demonstrated as an effective route to achieve high selectivity towards target products. More effort should be paid to understand the complicated correlation between the nature of supports and hydrogenation involving hydrogen spillover. Herein, we report the development of the hydrogenation system of hexagonal boron nitride (h-BN)-supported Pd nanoparticles for the hydrogenation of aldehydes/ketones to alcohols with hydrogen spillover. Nitrogen vacancies in h-BN determine the feasibility of hydrogen spillover from Pd to h-BN. The hydrogenation of aldehydes/ketones with hydrogen spillover from Pd proceeds on nitrogen vacancies on h-BN. The weak adsorption of alcohols to h-BN inhibits the deep hydrogenation of aldehydes/ketones, thus leading to high catalytic selectivity to alcohols. Moreover, the hydrogen spillover-based hydrogenation mechanism makes the catalyst system exhibit a high tolerance to CO poisoning.     

Tandem Guest-Host-Receptor Recognitions Precisely Guide Ciprofloxacin to Eliminate Intracellular Staphylococcus aureus

Staphylococcus aureus (S. aureus) is able to hide within host cells to escape immune clearance and antibiotic action, causing life-threatening infections. To boost the therapeutic efficacy of antibiotics, new intracellular delivery approaches are urgently needed. Herein, by rational design of an adamantane (Ada)-containing antibiotic-peptide precursor Ada-Gly-Tyr-Val-Ala-Asp-Cys(StBu)-Lys(Ciprofloxacin)-CBT ( Cip-CBT-Ada ), we propose a strategy of tandem guest-host-receptor recognitions to precisely guide ciprofloxacin to eliminate intracellular S. aureus. Via guest-host recognition, Cip-CBT-Ada is decorated with a β-cyclodextrin-heptamannoside ( CD-M ) derivative to yield Cip-CBT-Ada/CD-M , which is able to target mannose receptor-overexpressing macrophages via multivalent ligand-receptor recognition. After uptake, Cip-CBT-Ada/CD-M undergoes caspase-1 (an overexpressed enzyme during S. aureus infection)-initiated CBT-Cys click reaction to self-assemble into ciprofloxacin nanoparticle Nano-Cip . In vitro and in vivo experiments demonstrate that, compared with ciprofloxacin or Cip-CBT-Ada , Cip-CBT-Ada/CD-M shows superior intracellular bacteria elimination and inflammation alleviation efficiency in S. aureus-infected RAW264.7 cells and mouse infection models, respectively. This work provides a supramolecular platform of tandem guest-host-receptor recognitions to precisely guide antibiotics to eliminate intracellular S. aureus infection efficiently.     

钾改性氧化铝基羰基硫水解催化剂及其失活机理

天然气、油田伴生气、高炉煤气等化工生产过程中伴生COS气体,不仅会腐蚀管道和毒害催化剂,还会严重污染环境并危害人类健康。COS催化水解反应可在温和条件下高效的将COS脱除,是最具应用前景的COS脱除技术之一。碱金属元素因其具有独特的电子供体性质、表面碱性和静电吸附等特性,常被用作助催化剂以提高Al₂O₃的COS催化水解性能。近年来,以钾为助剂改性的Al₂O₃催化剂(K₂CO₃/Al₂O₃)在COS催化水解反应中得到广泛的应用,但由于负载在Al₂O₃上的K物种的组成复杂,目前研究者对K₂CO₃/Al₂O₃催化剂上COS水解机理的理解仍存在一定的困惑和争议。本论文通过湿法浸渍法合成出一系列钾盐和钠盐改性的Al₂O₃催化剂,并利用各类先进的表征技术对这些催化剂进行分析。活性测试表明,以K₂CO₃、K₂C₂O₄、NaHCO₃、Na₂CO₃和NaC₂O₄改性Al₂O₃催化剂均有助于COS的水解。其中K₂CO₃/Al₂O₃拥有最佳的COS水解性能,连续运行20 h后其COS转化率仍高于~93%,远远优于未改性的Al₂O₃ (~58%)。我们利用原位红外光谱和X射线光电子能谱探明了反应过程中催化剂的化学结构特征,阐明了H₂O分子在K₂CO₃/Al₂O₃上的水解作用机制。原位红外表明COS在K₂CO₃/Al₂O₃上的水解过程中形成了硫代碳酸氢盐中间产物。X射线光电子能谱表征证明催化剂的失活主要是因为催化剂表面积累了硫酸盐和单质硫。此外,我们还研究了水蒸气含量对COS水解性能的影响,研究发现,由于H₂O和COS分子在催化剂表面存在竞争吸附,过量的H₂O会引起催化活性的下降。上述研究表明,K₂CO₃/Al₂O₃催化剂上COS水解性能的提高主要是形成了HO-Al-O-K界面活性位。更为重要的是,所制备的催化剂都是在模拟工业工况条件下进行的,这为后续的工业应用提供了宝贵理论指导。本工作为理解助剂钾在Al₂O₃催化剂上COS水解活性的增强提供了新的见解,这为未来设计稳定高效的COS水解催化剂打开了新的发展方向。     

Assembled Organoruthenium(II) for Formaldehyde Decomposition and Hydrogen Production

Formaldehyde decomposition is not only an attractive method for hydrogen production, but also a potential approach for gaseous formaldehyde removal. In this research, we prepare some assembled organoruthenium through coordination reaction between Ru(p-Cymene)Cl₂ and bridge-linking ligands. It is a creative approach for Ru(p-Cymene)Cl₂ conversion into heterogeneous particles. The rigidity of bridge-linking ligand enables assembled organoruthenium to have highly ordered crystalline structure, even show clear crystal lattice with spacing of 0.19 nm. XPS shows the N−Ru bond are formed between bridge-linking ligand and Ru(p-Cymene)Cl₂. The assembled organoruthenium has high abundant active sites for formaldehyde decomposition at low temperature. The reaction rate could increase linearly with temperature and formaldehyde concentration, with a TOF of 2420 h⁻¹ at 90 °C. It is promising for gaseous formaldehyde decomposition in wet air or nitrogen. Formaldehyde conversion is up to 95 % over Ru-DAPM is 4,4′-diaminodiphenylmethane at 90 °C in air. Gaseous formaldehyde decomposition is a two-steps process under oxygen-free condition. Firstly, formaldehyde dissolve in water, and be converted into hydrogen and formic acid through formaldehyde-water shift reaction. Then intermediate formic acid will further decompose into hydrogen and carbon dioxide. We also find formaldehyde decomposition is a synergetic catalysis process of oxygen and water in moist air. Oxygen is conducive to formic acid desorption and decomposition on the active sites, so assembled organoruthenium exhibit slightly higher conversion for formaldehyde decomposition in moist air. This work proposes a distinctive method for gaseous formaldehyde decomposition in the air, which is entirely different from formaldehyde photocatalysis or thermocatalysis oxidation.     

Amphiphilic Heterografted Molecular Bottlebrushes with Tertiary Amine-Containing Side Chains as Efficient and Robust pH-Responsive Emulsifiers

By combining the unique characteristics of molecular bottlebrushes (MBBs) and the properties of stimuli-responsive polymers, we show that MBBs with randomly grafted poly(n-butyl acrylate) and pH-responsive poly(2-(N,N-diethylamino)ethyl methacrylate) (PDEAEMA) side chains are efficient and robust pH-responsive emulsifiers. Water-in-toluene emulsions were formed at pH 4.0 and disrupted by increasing the pH to 10.0. The emulsion generation and disruption was reversible over the ten cycles investigated, and the bottlebrushes remained intact. The exceptional emulsion stability stemmed from the high interfacial binding energy of MBBs, imparted by their large molecular size and Janus architecture at the interface, as evidenced by the interfacial jamming and wrinkling of the assemblies upon reducing the interfacial area. At pH 10.0, PDEAEMA became water-insoluble, and the MBBs desorbed from the interface, causing de-emulsification. Consequently, we have shown that the judicious design of MBBs can generate properties of particle emulsifiers from their large size, while the responsiveness of the MBBs enables more potential applications.