Synthesis of nanosize metallic and alloyed particles in ordered phases

Functionalized reverse micelles have been used to synthesize Copper and Cobalt nanoparticles differing by their size and shape. They can be also used to synthesize Fe–Cu alloy (at 30% Fe) and composite (at 70% Fe) particles. In the case of Fe–Cu system, the magnetic properties are presented.     

Chemical sensing and imaging with metallic nanorods

In this Feature Article, we examine recent advances in chemical analyte detection and optical imaging applications using gold and silver nanoparticles, with a primary focus on our own work. Noble metal nanoparticles have exciting physical and chemical properties that are entirely different from the bulk. For chemical sensing and imaging, the optical properties of metallic nanoparticles provide a wide range of opportunities, all of which ultimately arise from the collective oscillations of conduction band electrons ("plasmons") in response to external electromagnetic radiation. Nanorods have multiple plasmon bands compared to nanospheres. We identify four optical sensing and imaging modalities for metallic nanoparticles: (1) aggregation-dependent shifts in plasmon frequency; (2) local refractive index-dependent shifts in plasmon frequency; (3) inelastic (surface-enhanced Raman) light scattering; and (4) elastic (Rayleigh) light scattering. The surface chemistry of the nanoparticles must be tunable to create chemical specificity, and is a key requirement for successful sensing and imaging platforms.     

Theoretical methods in thermodynamics of condensed phases

Theoretical possibilities of determining energetic and thermodynamic characteristics of chemical entities in gaseous and condensed (solid and liquid) phases are briefly reviewed. The considerations include quantum chemistry methods which enable evaluation of energetic quantities and statistical thermodynamics dependencies necessary for determining other thermodynamic characteristics. The possible applications of these methods are also discussed in brief.     

Chemical and electrochemical behavior of metallic technetium in acidic media

The chemical and electrochemical properties of technetium metal were studied in 1–6 M HX and in 1 M NaX (pH 1 and 2.5), X = Cl, NO₃. The chemical dissolution rates of Tc metal were higher in HNO₃ than in HCl (i.e. 8.63 × 10^?5 mol cm^?2 h^?1 in 6 M HNO₃ versus 2.05 × 10^?9 mol cm^?2 h^?1 in 6 M HCl). The electrochemical dissolution rates in HNO₃ and HCl were similar and mainly depended on the electrochemical potential and the acid concentration. The optimum dissolution of Tc metal was obtained in 1 M HNO₃ at 1 V/AgAgCl (1.70 × 10^?3 mol cm^?2 h^?1). The dissolution potentials of Tc metal in nitric acid were in the range of 0.596–0.832 V/AgAgCl. Comparison of Tc behavior with Mo and Ru indicated that in HNO₃, the dissolution rate followed the order: Mo > Tc > Ru, and for dissolution potential the order: E _diss(Ru) > E _diss(Tc) > E _diss(Mo). The corrosion products of Tc metal were analyzed in HCl solution by UV–Visible spectroscopy and showed the presence of TcO₄ ^?. The surface of the electrode was characterized by microscopic techniques; it indicated that Tc metal preferentially corroded at the scratches formed during the polishing and no oxide layer was observed.     

Chemical diffusion in intermediate phases in the lithium-tin system

The compositional variation of the chemical diffusion coefficient in the six intermediate phases LiSn, Li₇Sn₃, Li₅Sn₂, Li₁₃Sn₅, Li₇Sn₂, and Li₂₂Sn₅ of the lithium-tin system at 415°C has been measured. Among these intermediate phases, the phase Li₁₃Sn₅ has the highest chemical diffusion coefficient, varying with composition from 5.01 × 10^?5 to 7.59 × 10^?4 cm²/sec at that temperature. Combining this information with coulometric titration curves (emf versus composition), the self-diffusion coefficient of lithium has also been determined in the various intermetallic phases as a function of composition under the assumption that the tin atoms do not move appreciably compared with the lithium atoms. The lithium self-diffusion coefficient in the phase LiSn is lower than those in the more lithium-rich phases by one order of magnitude. This result is discussed in terms of the difference between the crystal structures of LiSn and the other lithium-rich phases in the lithium-tin system.     

Chemical methods of stable isotope separation

The least expensive chemical methods of stable isotope separation are discussed. Between them are especially known chemical exchanges used for separation of boron, nitrogen and sulfur isotopes, low temperature rectification applied for enriching rare isotopes of carbon and oxygen and cryogenic adsorption served for obtaining very pure deuterium. The most important characteristics of installations, processes and working conditions are represented.     

Chemical,plasma chemical,and thermal modification of metallic catalysts

The role played by factors that modify the state of the surface of metals and their influence on catalytic activity are discussed. It is shown that the theoretical real gas model (two-dimensional electron gas-chemisorbed impurity particles) can be used to explain the character of the influence of nonmetallic and metallic impurities on the activity of catalysts. The influence of plasma chemical and thermal treatments of Rh, Ir, Ni, and Ag in the form of films, massive samples, and ultradisperse powders deposited on silica gel and Sibunite on their activity in the oxidation of CO, dehydrocyclization of n-C₆H₁₄, and dehydrogenation of isopropanol was studied. The influence of impurities and treatments specified was determined separately and in combination. The catalytic parameters changed because of changes in the surface electron density and the formation of structure defects on the surface of metals.     

Chemical methods in association with physical methods in drug analysis

Physical methods, namely spectroscopy and separation techniques such as high-performance liquid chromatography, in which the analyte is not chemically changed during analysis, have gained increasing popularity in the field of pharmaceutical analysis. Nevertheless, chemical manipulation in combination with such methods will continue to play a vital role, as will be demonstrated with examples selected from methods developed for two new, cardioactive drugs, nadolol and captopril, and from other recent literature references.     

The low-temperature proton-ordered phases of ice predicted by ab initio methods

The low-temperature proton-ordered counterparts for ice-Ih, ice-III, ice-VI and ice-VII are investigated by first principle methods in conjunction with a graph enumeration technique. Two experimentally well calibrated disorder/order transitions, ice-Ih/ice-XI and ice-VII/ice-VIII, are used to validate the methodology we used herein and in both cases our approach is able to reproduce major experimental features. For ice-III and ice-VI, direct structural determination on the fully proton-ordered counterparts by neutron diffraction is not available and in the literature different ordering schemes have been proposed. Our calculation results serve as an independent reference, and we shall discuss our findings and their relevance to previous experimental works.     

Combined supercritical fluid chromatographic methods for the characterization of octadecylsiloxane-bonded stationary phases

In this paper, we present a combination of a key-solute test based on retention and separation factors of large probe solutes (carotenoid pigments) and a quantitative structure-retention relationship analysis based on the retention factors of small probe solutes (aromatic compounds) to investigate the different chromatographic behavior of octadecylsiloxane-bonded stationary phases of all sorts: classical, protected against silanophilic interactions or not, containing polar groups (endcapping groups or embedded groups). Varied chemometric methods are used to enlighten the differences between the 27 phases tested. The results indicate that the two approaches chosen (carotenoid test and solvation parameter model) are complementary and provide precise information on the chromatographic behavior of ODS phases.     

Orientation of isotactic polypropylene in crystalline and amorphous phases: IR methods

Two methods based on polarization infrared spectroscopy are described for measurement of polypropylene orientation. One method, for the crystalline phase, allows precise measurement of polypropylene orientation in three orthogonal directions. It is based on the polarization characteristics of two crystallinity bands, those at 841 and 809 cm^?1, which exhibit opposite polarization characteristics. The other method, for the amorphous phase, provides a semiquantitative estimate and is suitable for uniaxially oriented films. It is based on polarization characteristics of the 1155-cm^?1 band. Both methods are applied to the measurement of orientation in polypropylene films uniaxially stretched at various speeds and temperatures.     

Chemical equilibria studies using multivariate analysis methods

Chemical multiequilibria systems can be monitored efficiently with the aid of spectroscopic techniques. Both hard- and soft-modeling are effective and powerful tools to extract chemical information from spectroscopic data. Recently, hybrid approaches that combine the flexibility of soft-modeling with the precise solutions provided by hard-modeling have been proposed. Here, we tested the performance of these three chemometric approaches for the analysis of several simulated data sets. In addition, experimental data recorded during the study of the acid–base equilibria of two DNA structures (G-quadruplex and i-motif) corresponding to two short sequences of the k-ras oncogene were studied. Finally, we also analyzed the interaction of the two DNA sequences with the model ligand TMPyP4. The results obtained from the analysis of these data sets may be useful to determine the most appropriate use of each approach. Whenever the presence of optically active interferences or unknown drifts can be neglected and a chemical model can easily be proposed and fitted, the hard-modeling method shows the best performance. If any of these conditions is not fulfilled, a hybrid-modeling approach may be a better option because all the contributions (chemical and unknown) can be modeled and the ambiguities inherent to soft-modeling methods show minor effects.     

Chemical test methods for determining components of liquids

The reported data on determining substances by chemical test methods are summarized. The reagents used; methods of their immobilization on supports; and principles, devices, and methods for determining components are considered. The main analytical characteristics are discussed.     

Chemical interactions between aqueous and organic phases in a reactive extraction process

Partitioning of lactic acid between aqueous phase and kerosene containing trin-octyl phosphine oxide (TOPO) as a reactive agent was measured and analyzed in terms of an association model between lactic acid and TOPO. Equilibrium association was calculated to involve 1.1 mol of lactic acid/mol of TOPO.³¹P-NMR and FTIR analyses found no evidence of covalent bond formation between lactic acid and TOPO in solutions in kerosene, and pointed to hydrogen bond formation between the two chemicals. In a hydrophobic, microporous, hollow-fiber-membrane module, the simultaneous presence of lactic acid, TOPO, and the back-extractant NaOH resulted in drastic membrane fouling as evidenced by the loss of kerosene flux through the membrane. The membrane could be restored back to the original kerosene flux after extensive washing.

     

Chemical and physical methods for characterisation of biofilms

Research on biofilms has developed into interdisciplinary work, in which scientists from different fields are involved. This review summarizes the state- of-the-art including models due to different aspects of biofilms. Techniques for characterization of surfaces and interfaces, e.g. microscopic, spectroscopic and microsensoric methods will be presented. In addition, procedures that involve sampling of biofilms and subsequent separation of the components for their analysis are a part of this article. Analytical methods are summarized for the investigation of extracellular polymeric substances (EPS), mainly polysaccharides beside proteins in the microbial host. Finally, procedures for the analysis of minerals as components of biofilms are presented.     

Chemical bonding, electron-phonon coupling, and structural transformations in high-pressure phases of Si

The nature of chemical bonding of the stable phases of Si at high pressure was analyzed. The effect of pressure is to promote sp electrons into the d orbitals, thus increasing the metallic character and reducing the dimensionality of covalent bonding. Localized covalent bonds, however, persist up to approximately 40 GPa (Si-VI, Cmca) and help to stabilize directional framework structures. At high pressures, Si becomes a metal, and the usual dense packed structures prevail. The existence of conducting and localized electrons gives rise to a combination of "steep and flat bands" near the Fermi level in Si-V. This peculiar electron topology in conjunction with low-frequency vibrations contributes to the relatively high superconducting temperature in Si-V and VI.     

Chemical methods for use with Vickers Multichannel 300

Summary The Vickers Multichannel 300 is an automated system for the chemical analysis of blood or serum. It has positive sample dentification and recalibration is done automatically. The process controller which includes a small digital computer is programmed to operate the machine and check for fault conditions. Results are printed in digital form and attention is drawn to those falling outside physiological limits. Analytical methods suitable for use on the machine have been developed. These include alk. phosphatase, lactate dehydrogenase, glucose, urea, bilirubin, total protein, albumen, S.G.O.T., as well as hydrogencarbonate, chloride, phosphate, sodium, potassium and calcium. The methods are described and an account of the repeatability obtained is given.

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Chemische Verfahren für die automatische Analysenapparatur Vickers Multichannel 300

Zusammenfassung Die Apparatur eignet sich für die chemische Analyse von Blutplasma oder -serum. Sie besitzt positive Probenidentifizierung und automatische Eichung. Das Steuergerät, das einen kleinen Digitalcomputer enthält, ist für die Bedienung der Apparatur und Prüfung auf Störungen programmiert. Die Ergebnisse werden digital ausgedruckt, wobei auf solche aufmerksam gemacht wird, die die physiologischen Grenzen überschreiten. Für die Apparatur geeignete Verfahren zur Bestimmung von alk. Phosphatase, Lactatdehydrogenase, Glucose, Harnstoff, Bilirubin, Gesamt-protein, Albumin, S.G.O.T. sowie Hydrogencarbonat, Chlorid, Phosphat, Natrium, Kalium und Calcium werden beschrieben und ihre Reproduzierbarkeit diskutiert.