Thin Film Counterelectrodes with High Li Charge Capacity for Electrochromic Windows

 Ce-V mixed oxide films have been deposited by RF sputtering with the aim of increasing the Li charge capacity of counter electrodes in smart windows. Such mixed oxides have shown high transmittance and optical passivity in the visible region. After electrode pre-conditioning by cyclic voltammetry, a good electrochemical reversibility in LiClO₄– propylene carbonate electrolyte was observed, and large Li-charge capacity under galvanostatic charging (up to 50 mCċcm⁻²) has been measured. The electrode charge capacity decreased after prolonged insertion-deinsertion cycles, whereas the photoptic transmittance remained about constant. After 800 cycles the Li-charge capacity decreased to 40 mCċcm⁻². The Li diffusion coefficient inside the films measured by electrochemical impedance and by galvanostatic titration ranged from 10⁻¹¹ cm²ċs⁻¹ to 10⁻¹³cm²ċs⁻¹. We observed that the Li charge capacity of the film electrodes is a function of the film deposition conditions, because it increased with the vanadium oxide concentration in the target and with the oxygen content in the sputtering atmosphere.     

Vibrational Spectroscopy and Analytical Electron Microscopy Studies of Fe–V–O and In–V–O Thin Films

Summary.  Orthovanadate (M ³⁺VO₄; M = Fe, In) and vanadate (Fe₂V₄O₁₃) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM), the chemical composition and the degree of crystallization of the phases present in the thin Fe–V–O films were investigated. TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin films are reported. Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lower temperatures (300°C) consisted of nanograins embedded in the dominating amorphous phase. Characteristic vibrational spectra allowed to distinguish between the different crystalline phases, since the IR and Raman bands showed broadening due to the decreasing particle size of the films thermally treated at lower temperatures. Vibrational analysis also showed that the electrochemical cycling of crystalline films led to spectra that were in close agreement with the spectra of the nanocrystalline films prepared at lower temperatures. The formation of a nanocrystalline structure is therefore a prerequisite for obtaining a higher charging/discharging stability of Fe–V–O and In–V–O films. Received October 4, 2001. Accepted (revised) November 23, 2001     

Analytical Techniques Applied in Optimization of Electrophoretic Deposition of Thin Film YBCO Superconductors

 YBa₂Cu₃O _7−x (x = 0.1–0.2) compounds (YBCO) were produced by the oxalate coprecipitation and the solid state reaction methods. The powders obtained were used for the production of YBCO superconducting coatings on Pt/Si wafers, by the electrophoretic deposition technique. The optimum process conditions for the production of both powders and coatings were found by using a combination of modern analytical techniques. The thermal treatment of the samples was followed by thermogravimetry (TG) and differential scanning calorimetry (DSC). The optimization and characterization of the superconducting properties of the powders and coatings were achieved by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), optical microscopy, magnetic susceptibility and electrical resistivity measurements.     

A Spectro-Microscopic Approach for Thin Film Analysis: Grain Boundaries in mc-Si and Sn/SnO2 Nano Particles

 Synchrotron radiation based spectro-microscopy is shown to be an exciting tool for elemental analysis in the field of heterogeneous interfaces, thin films, and device technology. Results are reported, taken with a spectrometer that enables the combination of a photoemission electron microscope (PEEM) with photoelectron spectroscopies (XPS, UPS) operated at a high brilliance undulator beam line at BESSY. The properties of mc-Si (multi crystalline silicon) are of interest because of their applications in low priced photovoltaic devices. An example of how to analyze the surface potentials of such surfaces without removing the native oxide is given. Tin nano-scale particles are shown to be the decisive factor affecting the corrosion prevention of passivated tinplate surfaces.     

Capacity Titration Technique for Determining the Solid Diffusion Coefficient of Intercalary Species within Insertion-host Materials

Investigation on the solid diffusion process of intercalary species within insertion-host materials plays an important role in the energy storage and output of secondary batteries1. To determine the solid diffusion coefficient, several electrochemical techniques have been developed such as galvanostatic intermittent titration (GITT)2,3, electrochemical impedance spectroscopy (EIS)4,5, potential intermittent titration technique (PITT)6, and potential step chronoamperometry (PSCA)7, potenti…     

Determination of Nitrite by a Modified Electrode of Poly(1-Naphthylamine) Film Doped with Dawson-Type Heteropolyanions

 The voltammetric behavior of the electrode modified with poly(1-naphthylamine) film doped with α-P₂W₁₈ heteropolyanions was investigated. The concentration of the modifier, the acidity of the medium and the scan range of potential had obvious effects on the electrochemical characteristics of the electrode. The electrocatalytical characteristics of the film electrode were studied by cyclic voltammetry and other methods. It is suggested that the electrocatalytic reaction of nitrite is controlled by its diffusion. The applicability of the electrode was assessed by the determination of nitrite in waste-water. Determination limit for nitrite was 5 × 10⁻⁷ mol.L⁻¹. Received August 23, 1999. Revision January 2, 2001     

Atomic Force Microscopy Studies of SnO2 Thin Film Microstruc tures Deposited by Atomic Layer Epitaxy

 ALE-grown, rutile-type SnO₂ thin films and gas sensor structures based thereupon were studied by AFM with main emphasis on cross-sectional investigations (X-AFM). On glass substrates the polycrystalline films showed a preferred orientation which depended on the film thickness and growth temperature while on single crystal sapphire () the growth was heteroepitaxial. For the X-AFM studies various sample preparation techniques were investigated but only ion beam etching gave satisfactory results and revealed substructures in the sensor structure consisting of Pt and SnO₂ layers on a silicon substrate.     

Estimation of Li+, K+ and Ca2+ Complexation with [12] crown-4, [15] crown-5 and [18] crown-6 Using a Na+ ISE in Dioxane-Water, Part IV*

 The (1:1) Na⁺ equilibrium constants, Ke1, of macrocyclic ethers of [12]crown-4, [12]crown-5 and [18]crown-6 were determined with a Na⁺ ISE in the presence of a second cation e.g. Li⁺, K⁺ and Ca²⁺ in dioxane/water (50/50). We estimated the (1:1) equilibrium constants, K e2 of the macrocyclic ethers with Li⁺, K⁺ and Ca²⁺ by this way. The binding selectivity of a macrocyclic ether between two cations was estimated in the same binary solvent mixture where the water hydration role is diminished. Results showed clearly the effect of macrocyclic size and cation radii in a solution. Received October 27, 1998. Revision March 22, 1999.     

M Spectra of Elements 39 ≤ Z ≤ 56 Measured with an Ultra-Thin Window Si(Li) Detector

 Elements in the range 39 ≤ Z ≤ 56 were excited by electrons of an energy between 3 and 15 keV. The X-rays were detected by means of an energy dispersive Si(Li) spectrometer with an ultra-thin polymer entrance window. In all cases M_ζ = M₅N₃ was found to be the most intense M line. Thus, the relative intensity of this line is by definition 100%. For the heavier of the investigated elements some other M lines were observed: M₅O₃, M_γ and M₂N₄. M_γ was detectable for Z ≥ 47, starting with a relative intensity of about 5%, which increased rapidly with Z to approximately 10%. M₅O₃ was first observed for 49-In, with a relative intensity of less than 10%, which increased up to approximately 50% for 56-Ba. Also, M₂N₄ was observed for Z ≥ 49. The relative intensity of that line is approximately one half of that of M_γ.     

Synthesis of a Model for Phycocyanin with Respect to the Acid-Base Chemistry between Protein and Chromophore

Summary.  Earlier investigations have shown that the cysteine adduct of phycocyanobilin dimethylester qualifies for intramolecular protonation [1]. In this context, the -Cys-Ala-Phe-Asp-tetrapeptide adduct of phycocyanobilin dimethylester was synthesized and examined for its protonation properties with respect to the zwitterionic interaction between chromophore and protein. Received March 15, 2000. Accepted March 21, 2000     

Prediction Helps Analytical Experimental Work for Environmental Purposes

 Analytical work, especially for environmental purposes, involves in the typical case determination of organic compounds in compartments, where their presence is very small. Identification of the appropriate experimental technique, whose range of applicability covers the concentration value involved, requires an estimate of this value. To this purpose, we present in this study a methodology for the prediction of the concentration of organic pollutants in the various environmental compartments (aquatic biota, air, sediment and soil) from the knowledge of the concentration in one of them. In case where the pollutant’s concentration is not available for any of the compartments, the proposed methodology can be used to estimate the maximum expected concentration in each one of them assuming that the water phase is saturated with the pollutant. The latter value can be obtained from a simple correlation presented here. The methodology is based on the correlation of the partition coefficients of pollutants among the various environmental compartments with two important thermodynamic quantities of pollutants: the octanol/water partition coefficient and the Henry’s law coefficient, which can be easily predicted by simple models presented here. Application of the methodology to field experimental data gives very satisfactory results at least for identifying the appropriate experimental technique.     

Elemental Analyses Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) of Geological Samples Fused with Li2B4O7 and Calibrated Without Matrix-Matched Standards

 Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used as a complementary technique to X-ray fluorescence (XRF), for multi-element analysis of geological samples fused with lithium-tetraborate Li₂B₄O₇). Different calibration strategies using external non-matrix matched reference materials were investigated. Various internal standards were tested, including the use of Li from the flux, and the use of the naturally occurring internal standards, Si or Ca. The use of a naturally occurring standard is not as efficient as this required a prior analysis of the samples using XRF. The obtained values for the analysis of geological reference materials were compared with consensus literature values, and satisfactory agreement was found. Laser pits, which were formed, had a diameter of 80 μm and 3–5 replicates on each fused disc were measured. The reproducibility of the method was better than 10% for concentrations above 1 μg/g and better than 15% for lower concentrations. The use of Li as the internal standard offers the possibility of multi-element determinations in geological samples, which have an unknown composition when the laser ablation analysis is carried out. However, using the calculated stoichiometric composition of the lithium-tetraborate for the calculation of the Li concentration leads to a constant deviation from the recommended values. Therefore, it was necessary to determine the Li concentration within each sample batch using at least one lithium tetraborate fused geological reference material. This resulting Li concentration in the beads was then used for all subsequent samples in a run. Limits of detection, reproducibility, deviation from reference values indicate the potential of LA-ICP-MS for such bulk analysis without matrix matched calibration standards.     

Influence of Pickling High Alloyed CrNi-Steels and Nickel Base Alloys with Citric Acid on the Composition of their Tarnish Oxides

 Extra-ordinary mechanical features and high corrosion resistance are essential qualities of CrNi-steels and nickel base alloys. The corrosion resistance of these materials fundamentally depends on their surface conditions. Tarnish colours and welding scale, formed during thermal treatment or joining, are removed by pickling components made of these alloys with sulphuric acid, nitric acid and hydrofluoric acid as well. By this kind of surface refinement several million tons per annum of aggressive waste waters are produced, that cause high environmental risks and not acceptable employee endangerings. Therefore, a project was promoted by the DECHEMA e.V. to replace hydrofluoric acid by organic complexing agents. The related surface analytical examinations are reported in this publication.     

New Experimental Cross-Section Measurements for Cr and Cu and Comparison with Model Predictions

 In order to obtain more accurate experimental values of X-ray emission cross sections, resulting from the interaction of ion with atoms, we have measured them for the K-inner-shell of Cr and Cu elements using a proton beam of energy range 1–2.3 MeV. The experimental data obtained in the present work are compared with the theoretical calculations given by the two models BEA (binary encounter approximation) and ECPSSR (energy coulombian perturbed stationary state relativistic). Also, the present experimental results are compared with those obtained by Paul and Sachert. The comparison shows a good agreement between the previous and the present data with a slight improvement in the measurement accuracy for Cr. From the theoretical point of view, agreement with the experimental data is observed only for the ECPSSR predictions, while the BEA’s cross section calculations at higher energies are approximately 20% lower than the present experimental values.     

A Novel Ion-Selective Sensor for Procaine Hydrochloride Based on a Piezoelectric Quartz Crystal Coated with a Procaine Tetraphenylborate PVC Membrane

 A novel ion-selective sensor for procaine hydrochloride has been proposed and applied successfully to analysis of pharmaceutical preparations. The sensor is based on modification of the Ag-electrode of an AT-cut piezoelectric quartz crystal with a PVC membrane containing procaine tetraphenylborate. A linear relation between the logarithm of the response frequency and the logarithm of the procaine hydrochloride concentration was found experimentally and could be explained by combination of a modified Sauerbrey equation and the Freundlich isotherm. The detection range was from 8.3 × 10⁻⁸ to 5.0 × 10⁻³ M with a detection limit of 8.3 × 10⁻⁸ M. The selectivity of the sensor and the influence of experimental parameters such as solution pH and detection time were investigated. Received February 10, 1999. Revision October 10, 1999.     

Structural and Chemical Analysis of Materials with High Spatial Resolution

 An understanding of the correlation between microstructures and properties of materials require the characterization of the material on many different length scales. Often the properties depend primarily on the atomistics of defects, such as dislocations and interfaces. The different techniques of transmission electron microscopy allow the characterization of the structure and of the chemical composition of materials with high spatial resolution to the atomic level: high resolution transmission electron microscopy allows the determination of the position of the columns of atoms (ions) with high accuracy. The accuracy which can be achieved in these measurements depends not only on the instrumentation but also on the quality of the transmitted specimen and on the scattering power of the atoms (ions) present in the analyzed column. The chemical composition can be revealed from investigations by analytical microscopy which includes energy dispersive X-ray spectroscopy, mainly quantitatively applied for heavy elements, and electron energy-loss spectroscopy. Furthermore, the energy-loss near-edge structure of EELS data results in information on the local band structure of unoccupied states of the excited atoms and, therefore, on bonding. A quantitative evaluation of convergent beam electron diffraction results in information on the electron charge density distribution of the bulk (defect-free) material. The different techniques are described and applied to different problems in materials science. It will be shown that nearly atomic resolution can be achieved in high resolution electron microscopy and in analytical electron microscopy. Recent developments in electron microscopy instrumentation will result in atomic resolution in the foreseeable future.     

Cathodic Adsorptive Stripping Voltammetry for Estimation of the Forest Area Pollution with Nickel and Cobalt

 Necessary conditions were established for simultaneous nickel and cobalt determination in environmental samples, such as oak wood and soil, based on cathodic adsorptive stripping voltammetry. Ni(II) and Co(II), complexed with dimethylglyoxime, were determined using a hanging mercury drop electrode. Optimum conditions were found to be: accumulation time 90 s, accumulation potential −0.80 V vs. SCE, supporting electrolyte 0.2 mol dm⁻³ ammonia-ammonium chloride buffer (pH = 9.4) + 0.05 mol dm⁻³ NaNO₂ and dimethylglyoxime 2 × 10⁻⁴ mol dm⁻³. A linear current-concentration relationship was observed up to 7.51×10 ⁻⁷ mol dm⁻³ for Ni(II) and 7.0 × 10⁻⁷ mol dm⁻³ for Co(II). Excess amounts of zinc(II) interfering with cobalt peaks were masked by complexation with EDTA. Wood and soils were mineralized by applying a microwave digestion system, using the mixtures H₂O₂ + HNO₃ or HNO₃ + HF, respectively. The developed procedure was tested by analysing international reference materials (BCR 62 Olive Leaves and GBW 08302 Tibet Soil). The developed procedure was used to determine pollution of oak stand with nickel and cobalt in different regions of Poland. Received August 10, 2000. Revision May 22, 2001.     

Combination of Aqueous and Non-Aqueous Capillary Electrophoresis with Electrospray Mass Spectrometry for the Determination of Drug Residues in Water

Summary.  The work presented in this paper deals with the combination of capillary electrophoresis (CE) with electrospray mass spectrometry (MS) for the determination of drug residues in water. CE/MS methods have been developed based on either aqueous or non-aqueous ammonium acetate solutions as the carrier electrolyte for the separation of selected drugs. The different separation conditions were compared in terms of selectivity and detection limits; both aqueous and non-aqueous CE proved to be suitable for the present analytical task, exhibiting detection limits between 3 and 93 μg/dm³ (injected standard concentration) corresponding to concentrations between 5 and 19 ng/dm³ in the sample. A combination of liquid-liquid extraction and solid-phase extraction was investigated for sample pretreatment, yielding enrichment factors of 10000. The applicability of CE/MS was demonstrated for the analysis of several river water samples. Received August 25, 2000. Accepted October 17, 2000     

Determination of Cobalt with a Tungsten Tube Atomizer by Electrothermal Atomic Absorption Spectrometry and its use for the Analysis of Biological Materials

 The determination of cobalt by electrothermal atomic absorption spectrometry with a tungsten tube atomizer has been investigated. The absolute characteristic mass (the mass of element giving 0.0044 abs.) of cobalt by the atomizer was 5.8 pg and the detection limit was 0.65 ng/ml (3S/N). The interferences caused by large amounts of interferents like Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn were evaluated and most of these elements were found to interfere with the cobalt signal. Ammonium thiocyanate as a chemical modifier was found to be efficient to eliminate the severest interferences. The accuracies of the recommended method were found to be almost satisfactory for the determination of cobalt in biological materials, as shown by a comparison with the reported values of NIST materials at the 0.02–0.4 μg/g level. Received August 24, 1998. Revision February 9, 1999.     

Performance of ICP-MS with Hexapole Collision Cell and Application for Determination of Trace Elements in Bio-Assays

 The application of a hexapole collision cell in quadrupole based inductively coupled plasma mass spectrometry (HEX-ICP-QMS) was studied systematically in order to characterize the performance of this approach for multielement analysis. Additionally, the performance of different solution introduction systems was studied for use with HEX-ICP-QMS (Platform, Micromass Ltd., Manchester, UK) and the developed methods were applied in the multielement analysis of biological tissue. A significant improvement in detection limits was achieved for ions affected by interferences with argon ions and argon-based molecular ions due to the removal of Ar⁺ and ArX⁺ ions (X = H, C, N, O, Ar) as well as for heavy elements (m > 100 u) due to better ion transmission through the hexapole ion guide. Metal oxide ion formation was reduced by up to ten times by the application of hexapole bias potential. Accuracy of the HEX-ICP-QMS measurements was assessed by analyzing standard reference material SRM 1566a Oyster Tissue and comparison with neutron activation analysis. Good agreement of measured trace element concentrations with certified values was found for most elements. Received December 7, 2000. Revision April 3, 2001.