A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity

Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.     

Methylation of zebularine investigated using density functional theory calculations

Deoxyribonucleic acid (DNA) methylation is an epigenetic phenomenon, which adds methyl groups into DNA. This study reveals methylation of a nucleoside antibiotic drug 1‐(β‐D ‐ribofuranosyl)‐2‐pyrimidinone (zebularine or zeb) with respect to its methylated analog, 1‐(β‐D ‐ribofuranosyl)‐5‐methyl‐2‐pyrimidinone (d5) using density functional theory calculations in valence electronic space. Very similar infrared spectra suggest that zeb and d5 do not differ by types of the chemical bonds, but distinctly different Raman spectra of the nucleoside pair reveal that the impact caused by methylation of zeb can be significant. Further valence orbital‐based information details on valence electronic structural changes caused by methylation of zebularine. Frontier orbitals in momentum space and position space of the molecules respond differently to methylation. Based on the additional methyl electron density concentration in d5, orbitals affected by the methyl moiety are classified into primary and secondary contributors. Primary methyl contributions include MO8 (57a), MO18 (47a), and MO37 (28a) of d5, which concentrates on methyl and the base moieties, suggest certain connection to their Frontier orbitals. The primary and secondary methyl affected orbitals provide useful information on chemical bonding mechanism of the methylation in zebularine. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Development of a Biomimetic Enzyme‐linked Immunosorbent Assay Method for the Determination of Methimazole in Urine Sample

A fast and direct competitive biomimetic enzyme‐linked immunosorbent assay (BELISA) method was developed for the determination of methimazole (MMZ) in urine sample based on a molecularly imprinted film as an artificial antibody. This is the first example to monitor methimazole with a direct competitive biomimetic enzyme‐linked immunosorbent assay (BELISA) method. The imprinted film was directly synthesized on the well surface of MaxiSorp polystyrene 96‐well plate and characterized. The results showed that it exhibited an antibody‐like binding ability, rapid adsorption speed, high stability, which was particularly advantageous and suitable for BELISA development. The BELISA method established in this paper had a higher selectivity for MMZ than for the structurally related compounds and the IC₅₀ (calculated as the concentration giving 50% inhibition of color development) and the detection limit values under optimized experimental conditions were 70 ± 4 μg L^‐1 and 0.9 ± 0.04 μg L^‐1, respectively. The method was applied to the determination of MMZ in spiked urine sample with excellent recoveries ranging from 90% to 95%, and the imprinted film was able to be reused for 20 times without loss of sensitivity. The results obtained by BELISA correlated well with that obtained by the high performance liquid chromatography (HPLC) method.     

dM-Dim for carboxylic acid protection

The 1,3-dithian-2-yl-methyl (Dim) and its analogous groups including dimethyl-Dim (dM-Dim) can provide a new dimension of orthogonality for carboxylic acid protection. They can be deprotected under nearly neutral oxidative conditions. In this paper, the protection of carboxylic acid with dM-Dim, deprotection of dM-Dim ester with sodium periodate, stability of dM-Dim protected carboxylic acid under acidic and basic conditions, and selective deprotection of dM-Dim protected carboxylic acids in the presence of tertiary butyl and methyl esters are presented.     

电化学制备异质二氧化钛结构增强其在光电分解水中转化效率（英文）

本文描述了一种利用电化学方法合成第二型异质二氧化钛纳米棒结构的方法,这种纳米棒由部分还原的黑色二氧化钛和原始的白色二氧化钛组成.这种异质结结构的半还原的二氧化钛纳米棒与原始的白色二氧化钛和完全还原的黑色二氧化钛纳米棒相比,展现出更好的光电催化性能.这可归结于这种条件下合成的纳米棒具备的协同作用.一方面,这类结构增强了整个太阳光光谱的利用率.底层的黑色二氧化钛能够大量吸收可见光,而上层的白色二氧化钛能够较好的利用太阳光中紫外光的部分.另一方面,因为形成了第二型异质结结构,电荷的激发分离和传输得到了有效的控制.这种简单的制备方法可进一步拓展合成其他金属氧化物,来进一步研究光电分解水的性能.本文利用传统的三电极系统:0.05 mol/L的硫酸作为电解液,在加–0.5 V的偏压下进行.相比与已报道的还原手段,该电解液中质子的浓度相对比较低,可以保证这个还原过程逐步发生.电化学还原曲线可以明显反映二氧化钛还原的过程,尽管从扫描电子显微镜中很难观察到响应的区别,但是在该过程中,电极片的颜色发生了明显的变化.相应的,我们将这个系列的电极进行了光学和晶体学的研究,发现其在还原过程中,能带能够逐步减小.而在X射线衍测试当中,仅最终完全还原的得到的样品在20度左右出现两个额外的峰,可归结为还原状态的二氧化钛.电化学扫描进一步测试其能带的相应位置,证明了黑色被还原的二氧化钛和白色的原始二氧化钛是同时存在的.最后将这个系列光电极光电催化分解水的性能进行了比较,发现在同等的测试条件下,形成异质结结构的二氧化钛具有最高的光催化效率,其值大约是白色二氧化钛的三倍,同时也比纯黑的二氧化钛增长了20%左右.另外,异质结结构的二氧化钛与黑色的相比,在可见光区域有相同的效率的同时具备更好的紫外光转化效率.最后,我们分析了异质结形成以后的相对应的能带结构,该结构能够更好的促进光吸收和转化.     

硅锑钼杂多酸·罗丹明B缔合物的共振散射光谱研究及其应用

在０．０４ｍｏｌ／Ｌ Ｈ２ＳＯ４介质中,ＳｉＯ＾２－３、Ｓｂ（Ⅲ）和ＭｏＯ＾２－４形成Ｓｉ－Ｓｂ－Ｍｏ三元杂多酸;调节酸度至０．２２ｍｏｌ／Ｌ Ｈ２ＳＯ４加入罗丹明Ｂ生成四元缔合物。该缔合物在６００ｎｍ处产生一灵敏的共振散射峰。据此建立了一个测定２－４０ｎｇ／ｍＬ Ｓｉ的共振散射光谱分析新方法,用于钢样中硅的测定,结果满意。     

Positron annihilation properties of copolyimides and copolyamides with microphase‐separated structures

The positron annihilation lifetime (PAL) of a series of copolyimides and copolyamides with microphase‐separated structures was measured to investigate the effects of different hard‐segment polymers on the PAL properties of soft‐segment domains of poly(dimethyl‐siloxane) (PDMS) and poly(ethylene oxide) (PEO). The lifetime (τ₃) and intensity (I₃) of the long‐lived component are given as a function of the PDMS or PEO content for a series of copolymers, of which the density roughly obeys the additive rule except for the PDMS‐segmented copolyamides. The PDMS‐segmented copolyimides and copolyamides show much smaller I₃ values than those estimated from the additive rule. The lifetime distribution of the long‐lived component for the PDMS‐segmented copolyamides is composed of two components. The longer‐lifetime component is attributed to pure PDMS domains, and the shorter‐lifetime component is attributed to the polyamide domains, intermediate phases, and PDMS domains containing small amounts of short amide blocks. Despite the high PDMS content, the latter component is rather large. Thus, the positronium formation in the PDMS domains of the copolyimides and copolyamides is effectively reduced. This can be explained by the combination of the difference in the electron affinity of the PDMS and polyimide or polyamide segments and the incomplete phase separation. The PEO‐segmented copolyimides show much smaller I₃ values than those predicted from the additive rule. This is likely attributable to the effects of the intermediate phases. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1123–1132, 2000     

Self-assembly architecture of bis(guanidiniums) receptors incorporated by sulfate anions in single crystals

A novel bis(guanidiniums)receptor for the catalytic cleavage of phosphosdiester was prepared and self-assembly architecture through hydrogen bonds and electrostatic interactions a-mong the bis(guanidiniums)receptor,the sulfate anion and water molecule was revealed by X-ray crystallographic analy-     

Synthesis reactivity and electrochemical properties of substituted cyclopentadienyl cobalt (III) complexes

Cyclopentadienyl cobalt complexes (η⁵‐C₅H₄R) CoLI₂ [L = CO,R=‐COOCH₂CH=CH₂ (3); L=PPh₃, R=‐COOCH₂‐CH=CH₂ (6); L=P(p‐C₆H₄O₃)₃, R = ‐COOC(CH₃) = CH₂ (7), ‐COOCH₂C₆H₅ (8), ‐COOCH₂CH = CH₂ (9)] were prepared and characterized by elemental analyses, ¹H NMR, ER and UV‐vis spectra. The reaction of complexes (η⁵‐C₅H₄R)CoLI₂ [L= CO, R= ‐COOC(CH₃) = CH₂ (1), ‐COOCH₂C₆H₅(2); L=PPh₃, R=‐COOC (CH₃) = CH₂ (4), ‐COOCH₂C₆H₅ (5)] with Na‐Hg resulted in the formation of their corresponding substituted cobaltocene (η⁵‐C₅H₄R)₂ Co[R=‐COOC(CH₃) = CH₂ (10), ‐COOCH₂C₆H₅ (11)]. The electrochemical properties of these complexes 1–11 were studied by cyclic voltammetry. It was found that as the ligand (L) of the cobalt (III) complexes changing from CO to PPh₃ and P(p‐tolyl)₃, their oxidation potentials increased gradually. The cyclic voltammetry of α,α′‐substituted cobaltocene showed reversible oxidation of one electron process.