Restraint of stress in fabricating the large areas of crack-free porous silica films in the presence of composite polydimethylsiloxane

To present a new method of fabricating the large areas of crack-free porous silica films by introduction of composite polydimethylsiloxanes (PDMS). We employed two kinds of side-chain polyether modified by PDMS terminated with Si–CH₃ and Si–OC₂H₅ groups in preparation of large areas of porous silica films. The porous film presents a mesopore structure with a porosity of 58.0 %, which is fit for thermal-isolating layer applied in pyroelectric devices. The stress evolution on gel-to-ceramic film conversion has been investigated. The results reveal that a slow decrease in tensile stress before 250 °C and a slow increase after 250 °C can be observed, which is closely related to the alteration of chemical composition in the heat-treatment process. It is clear that the stress has been restrained with the addition of composite PDMS.     

Visible‐Light‐Responsive Reversible Photoacid Based on a Metastable Carbanion

A new photoacid that reversibly changes from a weak to a strong acid under visible light was designed and synthesized. Irradiation generated a metastable state with high C?H acidity due to high stability of a trifluoromethyl‐phenyl‐tricyano‐furan (CF₃PhTCF) carbanion. This long‐lived metastable state allows a large proton concentration to be reversibly produced with moderate light intensity. Reversible pH change of about one unit was demonstrated by using a 0.1 mM solution of the photoacid in 95 % ethanol. The quantum yield was calculated to be as high as 0.24. Kinetics of the reverse process can be fitted well to a second‐order‐rate equation with k=9.78×10² M ^?1 s^?1. Response to visible light, high quantum yield, good reversibility, large photoinduced proton concentration under moderate light intensity, and good compatibility with organic media make this photoacid a promising material for macroscopic control of proton‐transfer processes in organic systems.     

Kinetic Resolution of Racemic Mandelic Acid Esters by N,N′‐Dioxide–Scandium‐Complex‐Catalyzed Enantiomer‐Selective Acylation

A simple and efficient acylative kinetic resolution of racemic mandelic acid esters was accomplished with a chiral N,N’‐dioxide–scandium(III) complex under mild and base‐free reaction conditions. A variety of mandelic acid esters performed well in the reaction, obtaining both acylated products (up to 49% yield, 97% ee) and recovered substrates (up to 49% yield, 95% ee) in high enantioselectivities with perfect selectivity factors (up to 247). The enantioselective recognition and catalytic models were also proposed for the catalytic KR reaction.     

Silver‐Catalyzed Cross‐Coupling of Propargylic Alcohols with Isocyanides: An Atom‐Economical Synthesis of 2,3‐Allenamides

Cross‐coupling reactions between propargylic alcohols and isocyanides, by means of silver catalysis, have been described. This new reaction is both atom and step efficient and is applicable to a broad scope of substrates, allowing the synthesis of a range of synthetically valuable 2,3‐allenamides in moderate to excellent yields.     

Hetero‐tri‐spin [2p‐3d‐4f] Chain Compounds Based on Nitronyl Nitroxide Lanthanide Metallo‐Ligands: Synthesis,Structure, and Magnetic Properties

Employing nitronyl nitroxide lanthanide(III) complexes as metallo‐ligands allowed the efficient and highly selective preparation of three series of unprecedented hetero‐tri‐spin (Cu?Ln‐radical) one‐dimensional compounds. These 2p–3d–4f spin systems, namely [Ln₃Cu(hfac)₁₁(NitPhOAll)₄] (Ln^III=Gd 1_Gd , Tb 1_Tb , Dy 1_Dy ; NitPhOAll=2‐(4′‐allyloxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide), [Ln₃Cu(hfac)₁₁(NitPhOPr)₄] (Ln^III=Gd 2_Gd , Tb 2_Tb , Dy 2_Dy , Ho 2_Ho , Yb 2_Yb ; NitPhOPr=2‐(4′‐propoxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) and [Ln₃Cu(hfac)₁₁(NitPhOBz)₄] (Ln^III=Gd 3_Gd , Tb 3_Tb , Dy 3_Dy ; NitPhOBz=2‐(4′‐benzyloxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) involve O‐bound nitronyl nitroxide radicals as bridging ligands in chain structures with a [Cu‐Nit‐Ln‐Nit‐Ln‐Nit‐Ln‐Nit] repeating unit. The dc magnetic studies show that ferromagnetic metal–radical interactions take place in these hetero‐tri‐spin chain complexes, these and the next‐neighbor interactions have been quantified for the Gd derivatives. Complexes 1_Tb and 2_Tb exhibit frequency dependence of ac magnetic susceptibilities, indicating single‐chain magnet behavior.     

β-PbO2/TiO2纳米管电极的制备及其电催化降解苯酚

采用阳极氧化法和脉冲电沉积制备出β-PbO2改性TiO2纳米管(β-PbO2/TiO2-NTs)电极,通过扫描电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等技术手段对制备的β-PbO2/TiO2-NTs电极的表面形貌和结构进行了表征。结果表明,该方法成功地将β-PbO2纳米颗粒分散在TiO2纳米管中,通过电催化降解苯酚评价了β-PbO2/TiO2-NTs电极的电催化活性,实验结果表明,在TiO2-NTs中电沉积β-PbO2提高了电极的电催化活性,对苯酚的降解达到83%。     

Phosphate Monoester Hydrolysis by Trinuclear Alkaline Phosphatase; DFT Study of Transition States and Reaction Mechanism

Alkaline phosphatase (AP) is a trinuclear metalloenzyme that catalyzes the hydrolysis of a broad range of phosphate monoesters to form inorganic phosphate and alcohol (or phenol). In this paper, by using density functional theory with a model based on a crystal structure, the AP‐catalyzed hydrolysis of phosphate monoesters is investigated by calculating two substrates, that is, methyl and p‐nitrophenyl phosphates, which represent alkyl and aryl phosphates, respectively. The calculations confirm that the AP reaction employs a “ping‐pong” mechanism involving two chemical displacement steps, that is, the displacement of the substrate leaving group by a Ser102 alkoxide and the hydrolysis of the phosphoseryl intermediate by a Zn2‐bound hydroxide. Both displacement steps proceed via a concerted associative pathway no matter which substrate is used. Other mechanistic aspects are also studied. Comparison of our calculations with linear free energy relationships experiments shows good agreement.     

纤连蛋白在石墨烯修饰二氧化钛表面吸附的计算机模拟

采用全原子分子动力学模拟方法研究了纤连蛋白(FN)在金红石表面、23%石墨烯覆盖率的金红石表面、92%石墨烯覆盖率的金红石表面、石墨表面的吸附行为.模拟结果表明:FN在金红石表面吸附不稳定.通过石墨烯修饰二氧化钛表面可降低金红石表面的亲水性;当表面含有石墨烯层时,FN都将稳定地吸附在表面上.在23%石墨烯覆盖率的金红石表面上,FN的特异性识别位点朝向溶液而有利于整合素识别.DSSP分析结果显示在40 ns的分子动力学模拟过程中,FN的七个β-折叠结构在所有体系中均没有发生太大变化.由于有石墨烯层存在,表面附近水分子层密度减小.FN的表面吸附能随着表面石墨烯覆盖率的增加而增大.石墨烯修饰能加强二氧化钛表面对蛋白质的吸附.本工作可以为移植体修饰生物材料设计与开发提供参考.     

The oxygen sensitive properties of (LaBa)Co2O5+δ thin films fabricated by polymer-assisted deposition technique

(LaBa)Co₂O_5+δ (LBCO) thin films were successfully fabricated on Si (001) substrates by polymer-assisted deposition method. Microstructures were examined by X-ray diffraction technique, which confirmed the films were a single phase, pseudo cubic structure. The electrical transport properties of the films were investigated by the temperature dependence of films resistance, which suggested that LBCO films have typical semiconductor properties. After circle tests, the oxygen–hydrogen response rate did not show obvious variation in the specific temperature environment of 580 °C. This demonstrates that the LBCO thin films have a superior stability in both oxygen and hydrogen (6 % H₂, 94 % N₂) environment. Simultaneously, the drastic changes of films resistance (from ~10⁶ to ~10² Ω) with the switch of redox (O₂–H₂) environment within such a short time (~2.2 s) indicated that LBCO films have an excellent oxygen sensitive property and extraordinary fast surface exchange rate.