A comparative study of the adsorption of La and Al at the mercury/aqueous electrolyte interphase

Cationic surface excesses at the mercury/aqueous A1Cl₃, LaCl₃ and AlCl₃ + LaCl₃ interphases have been determined from differential capacity, potential of zero charge and interfacial tension measurements. A comparative analysis of the adsorption of La³⁺ and Al³⁺ at negative potentials has been carried out. No definite support for La³⁺ specific adsorption has been found. On the other hand, a simple combination of ion size effects and the Gouy-Chapman theory was able to give a reasonable account of the experimental surface excesses, obtained from either single-salt or mixed-salt solutions.     

Adsorption of ethyl ether on polycrystal and the (110) single crystal face of gold by admittance measurements and modulated reflection spectroscopy

The adsorption of ethyl ether on polycrystalline and on (110) gold electrodes has been studied by simultaneous measurements of differential capacity and modulated electroreflectance (ER) in aqueous solutions of 0.02 M NaF containing various concentrations of ethyl ether. The results indicate that the adsorption can be studied only at negative charges, the behaviour at positive charges being masked by the oxidation of ether. A comparison of our capacity curves with the data obtained for Hg would indicate that the ether molecules are less strongly adsorbed on Au than on Hg. The ER measurements show that there is a proportionality between the amount adsorbed and the reflectivity change, and confirms that a simple interfacial model may be used to evaluate the amount adsorbed. Qualitative analysis of the ER spectra reveal that the adsorbed layer exhibits transparent optical properties and displays anisotropic characteristics in the adsorption—desorption region, probably due to the sudden change in the layer structure. Furthermore, the ER spectra provide evidence for the absence of any chemical interaction between gold and ether molecules.     

A study by ultraviolet spectroscopy on the self-association of diazines in aqueous solution

The self-association of pyridazine and pyrazine was studied in aqueous solution at acidic, neutral and basic pH values, by ultraviolet spectroscopy. The spectra of pyridazine in the mid-ultraviolet region did not show any variation in molar absorptivity upon concentration of this compound, indicating that self-association is not important. By contrast, deviations from Beer-Lambert law with increasing concentration were found in pyrazine at the pH values studied. A single hypochromic effect was detected at pH<0, 0.6 and 11.0, while a double hypochromic effect was observed at pH 6.9. These results were interpreted in terms of self-association of pyrazine leading to the formation of dimers at acidic and basic pH, and of dimers and polymers at neutral pH. From the fitting of the experimental curves of hypochromic effects, self-association constants were calculated. The self-association of 3-methylpyridazine, 2-methylpyrazine, and 2,3-dimethylpyrazine was also analyzed, concluding that the introduction of a methyl group has no influence upon the self-association of the pyridazine ring, but the self-association of pyrazine is enhanced by the introduction of two methyl groups. A comparative discussion of the self-association behavior of pyridazine, pyrazine and pyrimidine in aqueous solution has been carried out in terms of the differences in the molecular structure of the three diazines.     

A vibrational study by Raman spectroscopy of some dinuclear gold ylide complexes

A vibrational study of the dinuclear gold ylide complexes [Au(CH₂)₂PPh₂]₂ and [Au(CH₂)₂PPh₂]₂X₂ (X = Cl, Br or I) has been undertaken by Raman spectroscopy. The non-bonding AuAu interaction in the Au^I dimer, [Au(CH₂)₂PPh₂)₂, at 64 cm⁻¹ shifts to higher wavenumber in the single-bonded Au^II halogen complexes, with bands at 162, 132 and 103 cm⁻¹ for X = Cl, Br and I, respectively, being assigned to ν(AuAu). The Au-X vibration was also identified. The general trends in AuAu and Au-X stretching vibrations with changing halogen are compared with those for other dinuclear metal-metal bonded complexes, with a metal-metal bond order of one, and with those for mononuclear gold-halogen complexes.     

Lithium transport within the solid electrolyte interphase

A LiClO₄ SEI film grown on copper was examined with time-of-flight secondary ion mass spectrometry. The SEI porosity profile and Li⁺ transport processes within the SEI were studied with isotopically labeled ⁶LiBF₄ electrolyte. An ~ 5 nm porous region, into which electrolytes can easily diffuse, was observed at the electrolyte/SEI interface. Below the porous region, a densely packed layer of Li₂O and/or Li₂CO₃ prevents electrolyte diffusion, but Li⁺ transports through this region via ion exchange.     

Adsorption of pyridine on a polycrystalline gold electrode surface studied by infrared reflection absorption spectroscopy

The adsorption behavior of pyridine on a smooth polycrystalline gold electrode surface was investigated over a wide wavenumber region (2000–500 cm⁻¹) by in situ infrared reflection absorption spectroscopy (IRAS). The reversible adsorption/desorption of pyridine was observed upon the change in applied electrode potential, and the adsorption state at positive potentials was found to depend strongly on the kind of halide ion used as a supporting electrolyte. Symmetry analysis of absorption bands observed revealed that pyridine molecules adsorb with the molecular axis (C₂ axis) perpendicular to the electrode surface (vertical configuration) at positive potentials in 0.5 M KF, KCl and KBr solutions. A band due to the out-of-plane bending mode of the adsorbed pyridine molecule was observed at potentials more negative than ca. 0 V for 0.5 M KF solution containing 100 mM pyridine. We concluded that even in the 100 mM pyridine solution, adsorbed pyridine forms a monolayer and that the molecules reorient from a flat (parallel) to the vertical configuration as the potential becomes less negative. No bands due to adsorbed pyridine were detected for 0.5 M KI solution. The amount of adsorbed pyridine was found to depend strongly on the strength of specific adsorption of halide ions.     

Polystyrene latex adsorption at the gold/electrolyte interface

Irreversible deposition of polystyrene latex particles (average diameter, 1.5 microm) on various solid/electrolyte interfaces was studied experimentally by using the direct microscope observation method. The substrate surfaces included bare mica (reference interface), gold covered mica (layer thickness of 50 nm), and solid gold plate. The morphology and thickness of the gold layer on mica was determined by atomic force microscopy. Well-defined transport conditions of particles were created by using the new impinging-jet cell. A characteristic feature of the cell was that the suspension stream was directed obliquely to the interface. This unique characteristic was advantageous allowing one for direct, in situ, observation of particle deposition at metals and other nontransparent interfaces. Experiments performed for various flow intensities indicated that the initial deposition kinetics at all interfaces was identical within the error bounds, in accordance with the model based on the convective-diffusion theory. It was concluded that the limiting flux was governed by the bulk transport rather than by the specific surface interactions.     

Characterization of oxidoreductase-redox polymer electrostatic film assembly on gold by surface plasmon resonance spectroscopy and Fourier transform infrared-external reflection spectroscopy

The electrostatic assembly of nanocomposite thin films consisting of alternating layers of an organometallic redox polymer (RP) and oxidoreductase enzymes, glucose oxidase (GOX), lactate oxidase (LOX) and pyruvate oxidase (PYX), was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic attachment of a cationic RP, poly(vinylpyridine Os(bis-bipyridine)₂Cl-co-allylamine) (PVP-Os-AA), and anionic oxidoreductase enzymes. Surface plasmon resonance (SPR) spectroscopy, Fourier transform infrared external reflection spectroscopy (FT-IR-ERS) and electrochemistry were employed to characterize the assembly of these nanocomposite films. The surface concentration of GOX was found to be 2.4 ng/mm² for the first enzyme layer and 1.96 ng/mm² for the second enzyme layer, while values of 10.7 and 1.3 ng/mm² were obtained for PYX and LOX, respectively. The apparent affinity constant for GOX adsorption was found to be 8×10⁷ M⁻¹. FT-IR-ERS was used to verify the incorporation of GOX and its conformational stability inside of these nanocomposite thin films. An SPR instrument with a flow-through cell was modified by additions of Ag/AgCl reference and Pt counter electrodes, with the gold-coated SPR surface film serving as the working electrode. This enabled real-time observation of the assembly of sensing components and immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. A glucose-dependant amperometric response with sensitivity of 0.197 μA/cm²/mM for a linear range of 1-10 mM of glucose was obtained. The SPR and FT-IR-ERS studies also showed no desorption of polymer or enzyme from the nanocomposite RP-GOX structure when stored in aqueous environment occurred over the period of 3 weeks, suggesting that decreasing substrate sensitivity with time was due to loss of enzymatic activity rather than loss of film compounds from the nanostructure.     

Structure of aqueous electrolyte solutions estimated by near infrared spectroscopy and chemometric analysis of spectral data

The IR spectra of aqueous solutions of MClO₄, MNO₃, MCl (M = Li, Na), CsCl, and Na₂SO₄ were measured at frequencies of 5400–7500 cm^?1 over a wide concentration range from 0.12 M up to saturation concentrations at 25°C. Chemometric analysis of the experimental data matrix was performed. Regularity was detected in distribution of the IR spectra of the studied aqueous solutions on the the plot of analysis scores by the principal component method depending on the nature of the anion-water interaction. The influence of the nature of the salt anion and cation on the water structure in aqueous electrolyte solutions was demonstrated. The existence and interconversion of the spectral forms of water with changing electrolyte concentration in solution were revealed.     

聚合物固态电解质–高电压正极界面稳定性研究进展

聚合物固态电解质相比于液态电解质表现出更良好的热稳定性,并且对比无机固态电解质具有机械性能好、耐候性好和易加工成型等特点,因此在下一代高能量密度储能装置中极具应用潜能.然而,固态电解质与正负极材料之间的界面稳定性问题阻碍了其实际应用.本文总结了锂离子聚合物固态电解质的关键特性,讨论了聚合物固态电解质与高电压正极的普遍界面问题,包括界面接触不良与界面不稳定问题.分析了导致高电压富镍氧化物正极材料与聚合物固态电解质严重界面问题的主要因素,针对相关因素总结了缓解界面问题的有效策略,并展望了未来聚合物固态电解质与富镍层状氧化物的界面性能提升的研究方向,为基于聚合物固态电解质与高电压正极材料固态锂电池的研究提供参考.     

The FTIR study of uranium oxides by the method of light pipe reflection spectroscopy

Light pipe infrared reflection spectra of UO₂, UO₃, U₃O₈ have been studied by using an FTIR spectrometer. The uranium oxide powders were ground to ensure fine particle size and distributed on the inner surface of a straight glass pipe with gold coating. The infrared beam from the interferometer was focused into one end of the pipe at 45° incidence and then the transmitted beam was refocused by a pair of Cassegrainian type mirrors. The resultant spectra show the infrared characteristics of the -U-O-U-O-, uranyl ion UO ₂ ²⁺ bond vibration and the active lattice vibrations predicted by group theory calculations. In comparison to the transmission spectra measured by authors or reported in literature, this 45° incident light pipe method as well as the previous light pipe method offer advantages of sensitivity, ease of acquisition and interpretation, and require a very small sample. It confirms the power of the light pipe method for studying powders and its special utility for the infrared studies of hazardous materials.Visiting from the Physics Department, Peking University, Beijing, People's Republic of China     

A study of the structure of water in electrolyte solutions by differential infrared absorption spectroscopy in the overtone region

Theoretical and Experimental Chemistry -     

A study of electrolytic coagulation of gold sols by the method of localized surface plasmon resonance spectroscopy

Surface plasmon resonance spectroscopy has been employed to study the aggregation of gold sols with average nanoparticle sizes of 15–35 nm under the action of an indifferent electrolyte (NaCl). The structure of resulting aggregates has been established as depending on the coagulation regime. In the regime of fast coagulation, anisotropic aggregates with branched structure are initially formed; then, they are transformed into denser aggregates with a lower degree of anisotropy. The change of the aggregate structure accelerates with an increase in hydrosol concentration. At the same time, slow coagulation obviously yields denser aggregates, the structure of which is independent of the sol concentration and particle size. A procedure has been proposed for estimating the critical coagulation concentration of gold hydrosols based on the analysis of variations in their extinction. It has been found that the critical coagulation concentration increases with a reduction in the sol concentration and gold nanoparticle size.     

The role of adding NaF to the electrolyte in constructing a stable anode/electrolyte interphase for magnesium battery applications

Journal of Solid State Electrochemistry - Realizing practical Mg batteries still confronts crucial obstacles like the absence of a novel cathode with sufficient fast kinetic and the rapid...     

A review on the failure and regulation of solid electrolyte interphase in lithium batteries

Solid electrolyte interphase (SEI) has been widely recognized as the most important and the least understood component in lithium batteries.Considering the intr...     

A study of PBT/PC blends by modulated DSC and conventional DSC

Two poly(butylene terephthalate)/polycarbonate (PBT/PC) blends with different formulations were analyzed by modulated DSC (MDSC) and conventional DSC to determine differences in crystallization behavior. A significant difference (30°C in cold crystallization temperature) between the two samples was detectable by MDSC while no significant difference was seen by conventional DSC. That indicatesthe total heat flow from MDSC is not always equivalent to the heat flow from conventional DSC as we have assumed or seen before. The reason has not been fully understood, but may be related to unusual nucleation and crystallization induced by modulation. Alternative conventional DSC methods were developed and compared to the MDSC results.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe authors like to thank Drs. Bernhard Wunderlich and Robert Gallucci for helpful discussion, David Shaker and Mary Parsonage for some DSC experiments. Technical support from TA Instruments is also greatly appreciated.     

Electrodeposition of gold nanoparticles at a solid|ionic liquid|aqueous electrolyte three-phase junction

Gold nanoparticles have been electrodeposited on an electrode through electrogeneration at an ITO|AuCl₄^? solution in an ionic liquid|aqueous electrolyte three-phase junction. The electrodeposition was carried out by inverted double-pulse potential chronoamperometry. The direct reduction of AuCl₄^? ions at the electrode is followed by a counterion transfer through the liquid|liquid interface. Contrary to the electrodeposition from a single ionic liquid phase, scanning electron microscopy reveals that the shape of the resulting nanoparticles is highly angular and well-developed with a diameter of 110 ± 30 nm. Catalytic oxidation of glucose on the modified electrode is demonstrated.