Application of self-assembly for replacing chromate in corrosion protection of zinc

Due to the toxic and carcinogenic properties of hexavalent chromium ion, the corrosion protection with chromating technique needs replacement. Several environmentally friendly alternative metal pretreatments have already been proposed. One of these methods is the application of self-assembling molecules to form mono- or multilayers on the metal surfaces. These layers can prevent metal dissolution due to their dense and stable structure. The objective of our studies was to protect zinc surface against corrosion, with a thin phosphonate layer. Aqueous solutions of diphosphonic acid with different alkyl chain lengths were applied with different treatment times. The layer formation, stability, and corrosion protection of these films were monitored by electrochemical impedance spectroscopy and the effect of 1,5-diphosphono-pentane (DPP) on zinc was studied by polarization curves. The wetting properties were determined by static contact angle measurement. 1,5-Diphosphono-pentane forms a thin layer, with a pronounced protective ability in neutral aqueous solutions. The application of self-assembling molecules can be a promising method to replace the chromating technique on zinc surface.     

Thin layer distillation for matrix isolation in flow analysis

Analyte transfer from the matrix in a thin layer distillation (TLD) cell and its subsequent measurement were investigated in a flow injection configuration. We designed the cell such that the donor and acceptor streams flowed in parallel channels separated by a thin dividing wall. The matrix transfer process involved room-temperature distillation of the analyte into the headspace of the TLD cell and its subsequent condensation/uptake by a concurrently flowing acceptor stream. There are no membranes; hence there are no membrane-related problems. The TLD system design was optimized with respect to its dimensions and operational parameters. Throughput and sensitivity were compared with a conventional pervaporation flow injection (PFI) system for ammonia and five different amines. For the higher molecular mass amines, the TLD approach provided comparable or superior performance. The TLD technique should be an attractive approach for online analysis of volatile chemical species in ‘dirty’ samples, especially for volatile analytes of higher molecular mass.     

Microgel-based engineered nanostructures and their applicability with template-directed layer-by-layer polyelectrolyte assembly in protein encapsulation

A novel strategy for the fabrication of microcapsules is elaborated by employing biomacromolecules and a dissolvable template. Calcium carbonate (CaCO(3)) microparticles were used as sacrificial templates for the two-step deposition of polyelectrolyte coatings by surface controlled precipitation (SCP) followed by the layer-by-layer (LbL) adsorption technique to form capsule shells. When sodium alginate was used for inner shell assembly, template decomposition with an acid resulted in simultaneous formation of microgel-like structures due to calcium ion-induced gelation. An extraction of the calcium after further LbL treatment resulted in microcapsules filled with the biopolymer. The hollow as well as the polymer-filled polyelectrolyte capsules were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and scanning force microscopy (SFM). The results demonstrated multiple functionalities of the CaCO(3) core - as supporting template, porous core for increased polymer accommodation/immobilization, and as a source of shell-hardening material. The LbL treatment of the core-inner shell assembly resulted in further surface stabilization of the capsule wall and supplementation of a nanostructured diffusion barrier for encapsulated material. The polymer forming the inner shell governs the chemistry of the capsule interior and could be engineered to obtain a matrix for protein/drug encapsulation or immobilization. The outer shell could be used to precisely tune the properties of the capsule wall and exterior. [Diagram: see text] Confocal laser scanning microscopy (CLSM) image of microcapsules (insert is after treating with rhodamine 6G to stain the capsule wall).     

LBL分子沉积法制备葡萄糖氧化酶电极

采用以静电力为主的逐层分子交替沉积技术制备葡萄糖氧化酶（GOD）电极.通过带有正电荷的聚二甲基二烯丙基铵盐酸盐（PDDA）和带有负电荷的GOD交替沉积在修饰有3-巯基-1-丙基磺酸钠（MPS）的金电极表面.以甲酸二茂铁为电子媒介体,用循环伏安法检测GOD电极对葡萄糖的响应.结果表明,当GOD电极组装层数小于4时,电流响应随着层数的增加而增大,超过4层时电流响应减小.其中4层GOD修饰电极的线性范围为0.55～6.63 mmol•L－1,当pH为7.0时,响应最大.同时电极的检测重现性能良好,相对标准偏差为2.4％.     

Spectroelectrochemical Measurements at Colloidal Au Multilayer Optically Transparent Electrodes

Application of thin colloidal Au multilayers on glass substrates as optically transparent electrodes is reported herein. Evaluation of the electrode by scanning electron microscopy and as an optically transparent thin layer electrode (OTTLE) illustrate its use for spectroelectrochemical applications. A spectroelectrochemical Nernst plot acquired for the oxidation of o‐tolidine yielded a value of E°=0.605 V (vs. Ag/AgCl) and n=1.88. Both of these values are in excellent agreement with previously published values obtained using a traditional Au minigrid OTTLE. The colloidal Au multilayer electrode is expected to offer many advantages over the minigrid OTTLE in specific applications. These advantages include direct control over microscopic surface topography, large electrochemical surface area, applicability to many different electrode geometries, and increased microscopic surface roughness for SERS and SPR applications.     

Ion Association and Hydration in Aqueous Solutions of Nickel(II) and Cobalt(II) Sulfate

Aqueous solutions of nickel(II) and cobalt(II) sulfate have been investigated at 25 ^∘C by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 ≤ ν (GHz) ≤ 89) and salt concentrations (0.025 ≤ c(mol-L⁻¹) ≤ 1.4). The spectra indicate, as for MgSO₄(aq) studied previously, the simultaneous presence of double solvent-separated, solvent-shared and contact ion pairs in both NiSO₄(aq) and CoSO₄(aq). The stepwise formation constants for each ion-pair type and the overall association constant, obtained from the data are in good agreement with ultrasonic relaxation and other estimates. The DR spectra at higher concentrations (c ≥ 0.5 mol-L⁻¹) suggest the existence of a nonlinear triple ion M₂SO₄²⁺(aq). Consistent with the very strong hydration of the salts, which have ‘effective’ hydration numbers approaching 27 at infinite dilution, there are no significant differences in any of the relaxation or thermodynamic parameters for NiSO₄(aq) and CoSO₄(aq), except that the triple ion appears to be somewhat more stable for the latter.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

Spectroscopic Interrogation of Layer-by-layer Assembled Films of Conjugated Polyelectrolytes

Layer-by-layer fluorescent conjugated polyelectrolyte films have been studied. The photoluminescence of conjugate polyelectrolytes was observed to be highly tunable during this film assembly process. Efficient photoinduced electron transfer from thus prepared highly luminescent film to a natural electron-transfer protein cytochrome c has also been observed.     

Concentrated electrolyte solutions at high temperatures and pressures

A survey is given of recent experimental results obtained from high-temperature, high-pressure investigations with water, aqueous solutions, and ionic fluids. Data on the static dielectric constant of water to 550°C and 5 kbar are given and discussed with respect to their relation to water structure. Infrared and Raman spectra of HDO in pure water have been obtained to 400°C and 4 kbar, which give information on hydrogen bonding. Xe–H₂O and CO₂–H₂O mixtures were investigated in the infrared. Ni(II) and Cu(II) complexes were investigated by absorption spectroscopy in aqueous solutions of high chloride content to 350°C and 2–6 kbar. The gas-liquid critical point of ammonium chloride was found at 880°C and 1635 bars. This fluid appears to be predominantly ionic even in the critical region. The possibility of converting pure polar fluids such as ammonia and water into concentrated ionic solutions by self-ionization at very high pressures is mentioned.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.     

[Co（H2o）4（NCS）2]（18—C—6）的薄层光谱电化学研究

利用光谱电化学方法来研究冠醚类化合物的文章尚未见报导.本文在测定用凝胶法合成的[Co(H_2O)(NCS)_2](18-C-6)的核磁共振谱和红外光谱的基础上,使用循环伏安法和薄层光谱电化学技术,在金微栅电极上测定了此配合物在乙腈溶剂中的第一步克式量电势(E~0′)和电子转移数(n),并推测了电还原反应机理.