Catalytic reactivity and surface chemistry of polyaniline(EB)–Pd–H2O systems

Catalytic reactivity and surface chemical effects induced by the presence of water in the molecular system polyaniline(EB)–Pd–H₂O were investigated. The polyaniline(EB) doped with palladium reveals its high activity and selectivity in the semihydrogenation: hexyne → hexenes (→ hexane). However, to demonstrate these effects, the specimen has to be submitted to a special treatment to lose most of its water. The XPS analysis allowed identification of the catalytically active sites of the studied system. They were ascribed to the [PdCl₄]²⁻ complex anions present at the surface of the dry specimens. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chemisorption of O2 and CO on the K-modified diamond (100)2×1 surface

The adsorption of O₂ and CO molecules on the K-modified C(100) surface has been studied mainly by electron energy loss spectroscopy (EELS) and additionally by thermal desorption spectroscopy (TDS) and low-energy electron diffraction (LEED) at 300 K. Although O₂ does not react with the clean C(100) surface, it readily reacts with the K-modified surface. The adsorbed species are characterized by the two loss peaks at 150 and 214 meV. The 150 and 214-meV losses are ascribed to the CO stretch of the COC (ether) and >CO (carbonyl) species which are formed by breaking both σ and π bonds of a surface dimer, respectively. In contrast to Si(100), substrate oxidation mainly occurs at the top layer of C(100). The CO molecule also reacts with the K-modified surface, while it does not react with the clean C(100) surface. The adsorbed species are characterized by the loss peaks at 154 meV with a shoulder at 192 meV. The 154-meV loss is tentatively assigned to the CO stretch of the (C₂O₂)²⁻2K⁺ complex formed on the K-modified C(100) surface. The shoulder at 192 meV is ascribed to the CO stretch of either (C₄O₄)²⁻2K⁺ or >CO, in which the π bond is largely perturbed by the K adatoms.     

Synthesis,spectral, structural,Hirshfeld surface and DFT studies on bis(N-(4-fluorobenzyl)-N-(2-phenylethyl)dithiocarbamato-S,S′)zinc(II) and its use for the preparation of ZnS and ZnO nanoparticles

Two new complexes, bis(N-(2-phenylethyl)-N-(4-fluorobenzyl)dithiocarbamato-S,S′)zinc(II) (1) and bis(N-(2-phenylethyl)-N-(4-chlorobenzyl)dithiocarbamato-S,S′)zinc(II) (2), have been synthesized and characterized by various physicochemical techniques. Structure of 1 has been determined by single crystal X-ray diffraction. Complex 1 is a dimer. Zinc atom is four coordinated with a distorted tetrahedral environment. Geometry optimization, geometrical parameters, molecular electrostatic potential (MEPs) and frontier molecular orbital analysis of dimeric and monomeric structures of 1 have been carried out by DFT methods and compared with the experimental X-ray diffraction data. The noncovalent interactions in the complex 1 have been analyzed using Hirshfeld surface analysis. 1 and 2 have been used as single source precursors for the preparation of zinc sulfide and zinc oxide nanoparticles. As-prepared zinc sulfides and zinc oxides have been characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), UV–vis absorption, photoluminence and energy dispersive X-ray spectroscopy (EDS). X-ray diffraction study reveals that zinc sulfides and zinc oxides are composed of rhombohedral and hexagonal phases, respectively. Photocatalytic activities of zinc sulfides and zinc oxides were evaluated by degradation of rhodamine B in aqueous solution under UV light irradiation. The results demonstrated the capability of zinc sulfides and zinc oxides as photocatalyst under UV irradiation to degrade the dye.     

Adsorption capability of surface modified activated carbon for Cr(Ⅵ)

分别用H3PO4、KOH和ZnCl2对活性炭进行表面改性处理,研究了改性活性炭的表面化学性能及其对Cr(Ⅵ)的吸附性能.实验结果表明:通过上述改性,活性炭表面官能团数量发生了改变,改性后的活性炭对Cr(Ⅵ)的吸附性能提高.其吸附等温式均与Langmuir方程符合,吸附动力学较好地符合Lagergren二级吸附速率方程.     

Self-assembly behavior of hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(?-caprolactone) in epoxy resin: Nanostructures and surface properties

The organic-inorganic amphiphile, hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS)-capped poly(?-caprolactone) (POSS-capped PCL) was synthesized via the ring-opening reaction of ?-caprolactone, which was initiated by 3-hydroxypropylhepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS) with stannous (II) octanoate [Sn(Oct)₂] as the catalyst. The organic-inorganic nanocomposites were prepared via the in situ polymerization of epoxy monomers in the presence of the POSS-capped PCL. The atomic force microscopy (AFM) shows that the organic-inorganic hybrids possess the nanostructures. In view of the miscibility of the sub-components of the organic-inorganic amphiphile [i.e., PCL chains and POSS cages] with epoxy after and before curing reaction, the formation of the nanostructures in the thermosets followed the mechanism of self-assembly. The surface properties of the organic-inorganic nanocomposites were investigated by means of static contact angle measurements and X-ray photoelectronic spectroscopy (XPS). It is demonstrated that the improvement in surface hydrophobicity was ascribed to the enrichment of the POSS cages on the surface of the materials.     

orthovanadate (SO) and erythro

rate. The results suggested that the slower senescence rate of peach fruit was closely related to the higher peak value and longer duration of Ca2 -ATPase activity in microsomal membrane, with     

High and low surface area NiO–MgO and CoO–MgO solid solutions: a study of XPS surface composition and CO oxidation activity

Oxide solid solutions NiO–MgO of high surface area were studied by XPS. The surface Ni²⁺ concentration was found to be equal, within experimental errors, to the bulk concentration. The result is analogous to that found previously for the low surface area NiO–MgO system and for both the high and low surface area systems of CoO–MgO. The catalytic oxidation of CO by O₂, on high and low surface area NiO–MgO and CoO–MgO materials, was investigated with the aim of relating the catalytic activity with transition metal ion nature and concentration. Turnover frequency data (CO₂ molecules produced per second per surface atom) show that the activity is due primarily to the transition metal ions and is not subject to the ions being in special configurations (dimers or trimers) or in special positions (edges, corners). The activity of CoO–MgO is higher than that of NiO–MgO solid solution. This revised version was published online in June 2006 with corrections to the Cover Date.     

Crystallization and morphology of poly(ethylene succinate) and poly(β-hydroxybutyrate) blends

Summary The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy. The results indicate that PHB and PES are miscible in the melt. Consequently the blend exhibits a depression of the melting temperature of both PHB and PES. In addition, a depression of the equilibrium melting temperature of PHB is observed. The Flory-Huggins interaction parameter (χ₁₂ ), obtained from melting point depression data, is composition dependent, and its value is always negative. Isothermal crystallization in the miscible blend system PES/PHB is examined by polarized optical microscope. The presence of the PES component gives a wide variety of morphologies. The spherulites exhibit a banded structure and the band spacing decreases with increase PES content. Received: 29 June 1998/Revised version: 31 August 1998/Accepted: 10 September 1998     

Electrode material and performance of amorphous Ni(OH)2 codoped by Fe(Ⅲ) and Al(Ⅲ)

采用快速冷冻沉淀法首次成功制备出Fe(Ⅲ)和Al(Ⅲ)复合掺杂非晶态Ni(OH)₂粉体材料。通过XRD、SAED、SEM、IR、Raman光谱及DSC-TG等对样品粉体的结构形态进行表征和分析,同时将样品合成电极材料并组装成MH/Ni模拟电池进行电化学性能测试,结果表明,样品材料内部结构缺陷多、无序性强、材料微粒大小比较均匀,并具有较好的分散性,结合水含量较多。将复合掺杂Fe(Ⅲ) 5%和Al(Ⅲ) 8%的样品材料制备镍正极并组装成MH/Ni模拟电池,在以80 mA·g^-1恒流充电5.5 h,40 mA·g^-1恒流放电,终止电压1.0 V的充放电制度下,进行充放电性能、比容量及其循环性能等电化学性能的测试,放电平台平稳,工作电压高达1.30 V,放电比容量达到357.6 mAh·g^-1,且在电极过程中材料的稳定性增强、电化学阻抗较小,循环可逆性较好。     

Synthesis and characterization of 4,4’–(dimethylsilylene) bis( phenyl chloroformate) and 4,4’–(dimethylgermylene)bis(phenyl chloroformate) and their use in the synthesis of poly(urethanes)

Summary The synthesis of 4,4–(dimethylsilylene)bis(phenyl chloroformate) and 4,4–(dimethylgermylene)bis(phenyl chloroformate) is described according to the same route for the synthesis of bisphenol–A bischloroformate. These compounds were characterized using elemental analysis, FT–IR and NMR spectroscopy. Poly(urethanes) derived from these bischlororformates containing silicon or germane in the main chain, were obtained in benzene solution by reaction with 4,4–methylenedianiline in the presence of pyridine. Poly(urethanes) were characterised by spectroscopic methods and the thermal properties (Tg and thermal stability) were compared with the homologue poly(urethane) obtained from bisphenol–A chloroformate.     

Synthesis and photoactivity of novel cationic photoinitiators: (η-Diphenylmethane) (η-cyclopentadienyl) iron hexafluorophosphate and (η-benzophenone) (η-cyclopentadienyl) iron hexafluorophosphate

Two novel cationic photoinitiators (η⁶-diphenylmethane) (η⁵-cyclopentadienyl) iron hexafluorophosphate (PhCH₂PhFe⁺CpPF₆⁻) and (η⁶-benzophenone) (η⁵-cyclopentadienyl) iron hexafluorophosphate (PhCOPhFe⁺CpPF₆⁻), were synthesized, characterized, and studied. PhCH₂PhFe⁺CpPF₆⁻ was prepared by straightforward synthetic techniques with ferrocene and diphenylmethane and PhCOPhFe⁺CpPF₆⁻ was synthesized from oxidation of diphenylmethane–cyclopentadienyliron salt. Their activity as cationic photoinitiators was studied using real-time infrared spectroscopy. The results obtained showed that PhCH₂PhFe⁺CpPF₆⁻ and PhCOPhFe⁺CpPF₆⁻ are capable of photoinitiating the cationic polymerization of epoxy monomer directly on irradiation with long-wavelength UV light. Comparative studies also demonstrated that PhCH₂PhFe⁺CpPF₆⁻ exhibited better efficiency than I-261 and PhCOPhFe⁺CpPF₆⁻. DSC studies showed that PhCOPhFe⁺CpPF₆⁻ and PhCH₂PhFe⁺CpPF₆⁻ photoinitiators in epoxides possess good thermal stability in the absence of light.     

Adsorbed states of K on the diamond (100)(2×1) surface

The adsorbed states of K on the C(100)(2×1) surface have been studied by electron energy loss spectroscopy (EELS), work function change (Δφ) measurement and thermal desorption spectroscopy (TDS). In the region where the K coverage is less than one-half of a monolayer (θ_K≤0.5), a loss is observed from ∼1.2 eV (θ_K=0.2) to 1.0 eV (θ_K=0.5); the work function decreases upon K adsorption until reaching a shallow minimum of Δφ=−3.35 eV at θ_K=∼0.5; and a desorption peak (β) is observed from ∼825 K (θ_K=0.05) to 525 K (θ_K=0.5). These results indicate that the K–substrate bond is highly polarized; the 1.2 eV loss is attributed to the electronic transition from the bonding to antibonding states formed at the K–substrate interface. In the region between θ_K=0.5 and 1, two losses are observed at 0.7 and 1.4 eV (θ_K=0.6); there is only a small increase of the work function; and a desorption peak (α) is observed in addition to the β peak. These results indicate that the K regains its electron and becomes, essentially, neutral. The 1.4-eV loss is ascribed to the transition from the 4s to 4p states of K. The origin of the 0.7-eV loss is discussed. The Δφ and TDS results are analyzed by the depolarization model.     

The number of measurements of a surface’s topography and the expected variation in adhesion to the surface

Variations in roughness on a surface spawn variations in adhesion force between the surface and any particles that contact the surface. To fully characterize the adhesion that will be exhibited when a particle contacts any location on the surface, it is desirable to map the surface with nanoscale detail. Since it is impractical to make nanoscale roughness measurements over the entirety of a surface with a characteristic dimension on the order of centimeters, a relationship between the number of surface measurements and the likely variation in the expected adhesion force is similarly desirable. In this work, the predicted van der Waals force was used to describe the particle adhesion force. The bootstrap statistical method was employed to estimate the error associated with the predicted mean adhesion force between a smooth spherical particle and a rough surface as a function of the number of locations on the surface where the roughness was measured. Specifically, 40 atomic force microscope (AFM) topographical scans (5 × 5 μm) were taken of three different surfaces and used as model surface inputs to an existing van der Waals adhesion force simulator. The simulator described the expected adhesion force resulting from 1200 contacts between the smooth, spherical particle (10 μm diameter) and random locations on each scanned area. After analyzing the results using the bootstrap method, it was determined that the adhesion between the particle and 10–15 scanned areas (out of 40) optimizes the accuracy of the predicted adhesion with respect to the researcher’s labor.     

Syntheses,magnetic properties,and reactivity of dinuclear oxovanadium (IV) and copper (II) complexes with (μ-diphenylphosphinato)-bridges

Novel dinuclear oxovanadium (IV) complexes having the formula [(VO)₂(dpp)₃(bpy)₂]NO₃·2H₂O (1), [(VO)₂(dpp)₃(phen)₂]-NO₃·H₂O (2), [(VO)₂(bmp)₃(bpy)₂]NO₃·H₂O (3), and [(VO)₂(bmp)₃(phen)₂]NO₃·H₂O (4), and copper (II) complexes having the formula [Cu₂(bmp)₂(phen)₂](NO₃)₂·MeOH·H₂O (5), and [Cu₂(bmp)₂(bpy)₂](NO₃)₂ (6) (where Hdpp=diphenylphosphinic acid, Hbmp=bis(4-methoxyphenyl)phosphinic acid, bpy=2,2^′-bipyridine, and phen=1,10-phenanthroline) with (μ-phosphinato)-bridges, 1–6, have been prepared and characterized. Crystal structure of complex 2 reveals that two vanadium ions are linked by tris(μ-phosphinato)-bridges. The magnetic susceptibility data for 1–3, and 6 conform to the usual dimer equation with −2J values of 16–24 cm⁻¹, indicating a weak antiferromagnetic interaction between vanadium(IV) ions.The oxidation of cinnamyl alcohol was studied using complexes 1–6 as catalyst and molecular oxygen as an oxidant. In the presence of complex 3 as a catalyst, cinnamyl alcohol was oxidized to cinnamaldehyde 61% yield in 7 h. Consequently, complex 3 activates oxygen, and then alcohol was quite efficiently oxidized by activated oxygen.     

The flexible surface or the rigid surface?

In this paper we discuss aspects of the concept described by Somorjai as the flexible surface, and whether some surfaces can be considered to be inflexible, or rigid. We present STM results which appear to manifest both types of behaviour for surfaces, depending on their oxidation state. Copper metal surfaces can be classed as flexible, showing facile reconstruction in the presence of oxygen, whereas an oxidised Pd(110) surface shows no apparent diffusivity, even at 500 K. We go on to show data for a bulk oxide which indicates that sub-stoichiometry in the sample induces an element of flexibility in the surface, especially during reaction with oxygen. Finally, this is related to the direct observation of spillover on model catalysts of Pd nanoparticles supported on TiO₂. It must be recognised that flexibility relates to surface diffusivity and hence length- and time-scales. Surfaces which appear inflexible at short times may be flexible at long times. In relation to catalysis then, surface flexibility depends on the relationship between the time-scale of diffusive events on the surface and the catalytic turnover number.     

Synthesis and characterization of four- and six-arm star-shaped poly(ε-caprolactone)-b-poly(N-vinylcaprolactam): Micellar and core degradation studies

Star-shaped copolymers with four and six poly(ε-caprolactone)-block-poly(N-vinylcaprolactam) (S(PCL-b-PNVCL)) arms were successfully synthesized by combining ring opening polymerization (ROP) of ε-caprolactone (CL) and reversible addition-fragmentation chain transfer (RAFT) polymerization of N-vinylcaprolactam (NVCL). The resulting star copolymers were characterized using ¹H NMR, GPC and UV–vis. The numbers of arms in the star-shaped PCL-b-PNVCL block copolymers were demonstrated using degradation studies under acidic conditions, and the individual PNVCL chains were characterized by GPC and ¹H NMR. In aqueous solution, star-shaped PCL-b-PNVCL block copolymers self-assembled into large aggregates or micelles with sizes varying from 54 to 300 nm, depending on the molecular weight of the copolymer and the relative lengths of the hydrophobic and hydrophilic segments. Micelles were characterized by atomic force microscopy (AFM), dynamic light scattering (DLS) and scanning electron microscopy (SEM).     

Rheological properties of poly(ε-caprolactone) and poly(styrene-co-acrylonitrile) blends

Summary Rheological properties of poly(-caprolactone) (PCL) and Poly (styrene-co-acrylonitrile) (SAN) blends were examined as a function of the acrylonitrile (AN) content in SAN, to systematically understand the correlation between the interaction parameter and the theological properties of miscible polymer blends. When the plateau modulus (G _N ⁰) and zero shear viscosity ( ₀) of the PCL/SAN blends are plotted against the AN content in SAN, a minimum is observed. Qualitatively, the results obtained parallel the variation of the interchain interaction with the AN content. The negative deviation ofG _N ⁰ and ₀ from linearity seems to be attributed to the increase in the entanglement molecular weight between dissimilar chains which results from the chain extension caused by interchain interaction.     

Modifying the STM tip for the ' ultimate ' imaging of the Si(111)-7×7 surface and metal-supported molecules

We report on high-resolution STM measurements with modified probe tips. First, both the rest atoms and adatoms of a Si(111)-7×7 surface are observed simultaneously. The visibility of rest atoms is dependent upon the sample bias voltage (less than -0.7 V) and is enhanced by sharpening the tip, which is rationalized by first-principles calculations. Second, a tip with a perylene molecule adsorbed at its apex is used to discriminate the molecular states and the metal states of the underlying Ag(110) surface, which is attributable to a mismatch between the energy levels of the functionalized tip and the adsorbates on silver. Lastly, high-resolution images of iron phthalocyanine (FePc) and zinc phthalocyanine (ZnPc) molecules on Au(111) are obtained by using an O(2)-terminated tip, and the images reveal rich intramolecular features arising from molecular orbitals that are not observed when using clean metallic tips.     

Mechanism of micro-particle motion across falling liquid cylinder for PM2.5 separation (Ⅰ)Trajectory of particle motion towards surface and separation radius

提出了横掠液柱流的速度场和温度场推动PM_2.5微粒附面运动机理,建立了微粒附面运动微分方程和数值积分反演方法,计算粒子运动轨迹并预测可吸收的微粒运动最大分离半径。定义最大分离半径与液柱表面之间附面层的厚度为分离厚度,以气溶胶流体通过该区域的体积流量与横掠单液柱的总体积流量之比代表单液柱吸收效率;热泳推动力是强化吸收效率的主要因素。基于单液柱吸收效率,按串联模型导出规则排列的液柱群整体分离效率计算公式,依据液柱交叉流几何结构、流体流动和气液两相传热传质参数即可确定整体分离效率。对交叉流Reynolds数为170的实例计算显示,直径4 mm的单液柱吸收效率为1.18%,由195排液柱群组成的长度为1170 mm的分离通道整体分离效率达到90%。