Determination of trace amounts of beryllium using derivative spectrophotometry in non-ionic micellar medium

A rapid and sensitive method for the trace level determination of beryllium based on the formation of a 1:2 complex (λ_max 560 nm) with 1,4-dihydroxy-9,10-anthracenedione in an aqueous medium containing Triton X-100 is reported. Beer’s law is followed in the range 3.60–360 ng ml⁻¹ of Be(II). The molar absorptivity and Sandell’s sensitivity are 1.68×10⁴ l mol⁻¹cm⁻¹ and 0.54 ng cm⁻², respectively; detection limit is 0.23 ng ml⁻¹ of Be(II). Analysis of synthetic mixtures of composition similar to that of alloys and spiked samples of distilled water, gave results that are in agreement with their beryllium content.     

A pressure and temperature study on solubility and micelle formation of sodium perfluorodecanoate in aqueous solution

Both the critical solution temperature (CST, or the Krafft temperature) and the critical solution pressure (CSP, or the Tanaka pressure) were determined for sodium perfluorodecanoate (NaPFDe) in water, and the result shows that the Krafft temperature is raised with the increase in the Tanaka pressure. A thermodynamic analysis has been made on the data for the critical micellization concentration (cmc) and of the solubility at various temperatures and pressures. The estimated change in the partial molal volume, resulting from micelle formation from the singly dispersed state and from the hydrated solid state, was found to be conspicuously higher for NaPFDe compared to hydrocarbon surfactants. This has been ascribed to the more pronounced role of carbon chain-water interactions and water structure effects of the fluorocarbon surfactants.     

New route for removal of Cu(II) using fabricated nanocomposite based on cationic surfactant/Ag-nanoparticles/silica gel

Generally, the treated wastewater must at least achieve the minimum safety standards for the purpose of the treatment process. The main target of this work is the combination of the features of surfactants, nanoparticles, and silica gel in one system for Cu(II) removal from the aqueous solution. To achieve this goal, the attempt would be made by the fabrication of nanocomposite based on 4-amino-N-tetradecyl pyridinium bromide (C14) coated silver nanoparticles and silica gel. The fabricated nanocomposite (C14-Ag-SG) was characterized using different techniques such as FTIR, XRD, XRF, SEM, and TEM. We examined the adsorption of Cu(II) ions onto the fabricated nanocomposite using batch adsorption. The effect of the contact time, pH of the solution, and mass of the adsorbent on the efficiency of adsorption was evaluated. The adsorption capacity of Cu(II) increased by increasing of the contact time with a neutral pH. The maximum removal of Cu(II) ions (98.57 %) was found using 0.4 g of the (C14-Ag-SG) nanocomposite. The fabricated nanocomposite showed high adsorption efficiency which clarifies the effect of the surfactant compound (C14) and silver nanoparticles in improving the adsorption efficiency. The results in this work suggest that the fabricated nanocomposite has high efficiency in the removal of Cu(II).     

Cyclic Voltammetry Examination for Effect of Counter Anion on Adsorptive Voltammetry of 11‐Ferrocenytrimethylundecylammonium at Carbon Paste Electrode

The electrode oxidation of 11‐ferrocenyltrimethylundecylammonium (FeTMUA) at carbon paste electrode (CPE) was investigated by cyclic voltammetry in order to reveal the adsorption nature of FeTMUA ion‐paired with anion. The voltammograms of FeTMUA were classified by the counter anion; hydrophilic and hydrophobic ions. The electric charge reflecting the adsorption isotherm increased gently with the FeTMUA concentration until a critical point (CP), which was independent of the sort of hydrophilic anion and comparable with the amount of the maximum surface coverage of FeTMUA at the air‐water interface. The voltammogram for hydrophobic anion had two oxidation waves. The electric charge for the first wave monotonously increased with the FeTMUA concentration without indicating CP. The second wave was not observed on the voltammogram at the glassy carbon electrode, thus the second wave was made from the pasting liquid. These results suggested that CPE adsorbed FeTMUA with hydrophilic anion behaved like serving a liquid surface, however, CPE adsorbed FeTMUA with hydrophobic anion was disordered and represented the heterogeneity.     

Styrene and methylmethacrylate oil-in-water microemulsions

 A simple procedure for the preparation of styrene-in-water and methylmethacrylate (o/w) micro-emulsions was established. This consisted of the preparation of a w/o emulsion using a low HLB number surfactant (Synperonic NP4, nonyl phenyl with 4 mol ethylene oxide) and a small amount of an anionic surfactant (Aerosol OT, diethyl hexyl sulphosuccinate, or sodium dodecyl benzene sulphonate). The w/o emulsion was then titrated with an aqueous solution of a high HLB number surfactant (Synperonic NP15, nonyl phenyl with 15 mol ethylene oxide). The droplet size and poly-dispersity were determined using photon correlation spectroscopy (PCS). The temperature range within which a microemulsion remained stable decreased with increase in the concentration of styrene or methylmethacrylate and this could be explained in terms of the phase diagram of the microemulsion system. Conductivity measurements as a function of temperature showed that the systems are oil-in-water microemulsions. Received: 20 December 1996 Accepted: 5 March 1997     

Mesoscopic Simulation of Aggregates in Surfactant／Oil／Water Systems

The aggregates in sodium dedecylsulphate(SDS)/dimethylbenzene/water systems have been investigated using dissipative particles dynamic(DPD) simulation method.Through analyzing three-dimensional structures of aggregates,three simulated results are found.One is the phase separation,which is clearly observed by water density and the aggregates in the simulated cell;another is the water morphology in reverse micelle,which can be found through the isodensity slice of water including bound water,trapped water and bulky water;the third is about the water/oil interface,i.e.,ionic surfactant molecules,SDS,prefer to exist in the interface between water and oil phase at the low concentraion.     

The effect of an anionic surfactant on the rheology and stability of high volume fraction O/W emulsion stabilized by PVA

The effect of the addition of an anionic surfactant (sodium dodecyl benzene sulphonate) on the rheology and storage stability of concentrated O/W emulsions stabilized by poly (vinyl alcohol) is reported. It was found that the surfactant markedly reduced the magnitudes of the storage modulii of the emulsions. This could be attributed to a reduction in the interfacial tension resulting from the formation of polyelectrolyte type complexes between the PVA and NaDBS at the O/W interface. The results were compared to the equation (given by Princen) relating concentrated emulsion rheology to the interfacial tension and droplet size. Reasonable agreement was found, though there was a small difference in the constants in the equation given by Princen and those found here. The agreement suggested that the emulsions were deforming above a critical volume fraction and that the rheological properties were dominated by the dilation of the interface during shear. Microelectrophoresis measurements showed that the addition of the surfactant conferred a charge onto the PVA stabilized droplets as a result of the formation of the polyelectrolyte complex. The NaDBS was found to reduce the long-term stability of the emulsions compared to emulsions containing PVA alone.     

Determination of 4-methylbenzilidene camphor in sunscreen by square wave voltammetry in media of cationic surfactant

The voltammetric behavior of 4-methylbenzelidene camphor (MBC) was studied by square wave voltammetry (SWV) using mercury electrode. The experimental condition that provided the highest peak current with the best reduction signal definition of MBC was found in Britton-Robinson buffer and cationic surfactants, cetyltrimethylammoniun bromide (CTABr). A single peak of MBC reduction was observed at − 1.21 V versus Ag/AgCl. The developed methodology was applied for determination of MBC in commercial sunscreen SPF 15, 20 and 30 and for the simultaneous determination when other protection agents were associated, such as benzophenone-3 (BENZO) and octyl methoxycinammate (OMC). Both methodologies had shown good determination values for the analyzed samples. The calculated detection limit was 2.99 × 10^− 9 mol L^− 1 and the quantification limit was 9.98 × 10^− 9 mol L^− 1.     

咪唑啉型表面活性剂组成微乳液的热力学性质

由咪唑啉型表面活性剂、醇、水和正十六烷组成微乳液，探讨了该微乳液中醇从油相转移到界面相时的自由能变化及温度对自由能变化的影响，算得了熵变和焓变。     

Photosensitive polyimides for applications in electrical and optical interconnection technology

The application of photosensitive polyimides in electrical and optical interconnection technology is discussed. Critical properties of two photosensitive polyimide formulations with significantly different structural chemistries have been compared. Polyamic ester based formulations such as Selectilux® HTR3 show significant distortions in the photopatterned features upon high-temperature baking, which can be ascribed to anisotropic shrinkage. A BTDA-alkylated diamine based preimidized formulation (Probimide®), on the other hand, shows a more uniform shrinkage of the photopatterned features. HTR3 films interacts strongly with metals such as copper, which adversely affect the photopatternability of these materials. Planarization behavior in multiple layer structures has also been investigated. We explored the viability of these materials for applications in optical interconnection. Probimide® materials exhibit low scattering losses and appear to be promising candidates for the development of a MCM-compatible optical interconnection technology. We also describe here a novel technique for optical recording of refractive index patterns in Probimide® films.