Particle adhesion studies relevant to chemical mechanical polishing

This study describes particle adhesion experiments carried out to elucidate interactions between particles in slurries used for polishing of wafers and disks. For this purpose the packed column technique was employed, which simulated chemical mechanical polishing of copper with silica and alumina, as well as of silicic oxide with ceria. The model systems consisted of uniform copper and glass beads as collectors, representing the wafers, and colloidal dispersions of silica, alumia, and silica coated with nanosize ceria, all of well-defined properties that are used as abrasives. It was shown that a strong correlation exists between deposition and detachment results of the adhesion studies and the polish rates measured using actual substrates with the same or similar slurries.     

XPS Study of the Corrosion Protection of Fluorozirconate Glasses Dip-Coated with SnO2 Transparent Thin Films

Tin oxide nanoparticles prepared by an aqueous sol–gel method were deposited by dip-coating on fluorozirconate glass, ZBLAN (53%ZrF₄-20%BaF₂-4%LaF₃-3%AlF₃-20%NaF) to improve its resistance against wet corrosion. The aqueous leaching of uncoated and SnO₂-coated fluorozirconate glass was studied by X-ray photoemission spectroscopy (XPS) and it was shown that even an ultra thin tin dioxide film provides good protection of the glass surface against the bulk propagation of the hydrolytic attack.     

Gradient- und Transfer-Techniken in der Chromatographie

Zusammenfassung In einer Übersicht werden die Gradient-Techniken in der Chromatographie unter allgemeinen Gesichtspunkten besprochen. Gradient-Verfahren kann man in der stationären und der mobilen Phase sowie in den Milieubedingungen einführen. Neuartige Möglichkeiten ergibt eine Chromatographie quer zum eigentlichen Verlauf des Gradients. Dieses Verfahren wurde erstmals für die DC ausgearbeitet.Zur sicheren Identifizierung der getrennten Substanzen ist die Kombination mit geeigneten physikalischen, chemischen und biologischen Verfahren wichtig. Erprobte Möglichkeiten der direkten Kopplung und des mechanischen Transfers kleinster Mengen werden an Beispielen geschildert.

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Summary Gradient techniques in chromatography are reviewed in general. Gradients can be introduced in the properties of the stationary and/or mobile phases and in the other conditions (e.g. temperature or flow rate programming). A chromatography which traverses the gradient direction yields new possibilities. This procedure has been worked out for TLC for the first time.Combination with suitable physical, chemical and biological procedures is important for accurate identification of the separated substances. Tested possibilities of direct coupling and of mechanical transfer of very small amounts are illustrated by examples.

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Mein Dank gilt allen Institutionen und Firmen, aber insbesondere den Mitarbeitern, die mir nei der Verwirklichung meiner Forchungsvorhaben tatkräftig geholfen haben.

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Festvortrag anläßlich der Verleihung des Fresenius-Preises am 14. 4. 1966 in Lindau; zugleich XVI. Mitt. Dünnschicht-Chromatographie.     

The (p, ρ, T) properties and apparent molar volumes Vϕ of (ZnBr2 + C2H5OH)

The (p, ρ, T) properties and apparent molar volumes V_? of ZnBr₂ in ethanol at temperatures (293.15 to 393.15) K and pressures up to p = 40 MPa are reported. The measurements were made with a recently developed vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, ethanol, and aqueous NaCl solutions. The experiments were carried out at molalities of m = (0.05681, 0.16958, 0.30426, 0.43835, 0.93055, 1.49016, and 1.88723) mol · kg^?1 using zinc bromide. An empirical correlation for the density of (ZnBr₂ + C₂H₅OH) with pressure, temperature, and molality has been derived. This equation of state was used to calculate other volumetric properties such as isothermal compressibility, isobaric thermal expansibility, the differences in specific heat capacities at constant pressures and volumes, apparent molar volumes of ZnBr₂ in ethanol, and partial molar volumes of both components.     

Easy access to 4-nitrothiochroman S,S-dioxides via ring-enlargement from 3-nitrobenzo[b]thiophene

The (E)-2-aryl-1-[2-(methylthio)phenyl]-1-nitroethylenes 5 can easily be oxidized to the relevant sulfones 6 and effectively subjected to cyclization via an intramolecular Michael addition after metallation with lithium bis(trimethylsilyl)amide in THF. After quenching with ammonium chloride the 3-aryl-4-nitrothiochroman S,S-dioxides 2 are obtained as diastereomeric mixtures in good to excellent yields. Both yields and stereochemistry of the ring-closure step appear to be influenced by steric effects of the 3-aryl moiety. As sulfides 5 derive from an initial ring opening of 3-nitrobenzo[b]thiophene (1), the overall 1 to 2 process can be considered as an effective 5 to 6 ring enlargement of the sulfur heterocycle. A conformational ¹H NMR and molecular-mechanics investigation on the isolated diastereomeric 2 has also been accomplished.     

Analysis of the recent antipsychotic aripiprazole in human plasma by capillary electrophoresis and high-performance liquid chromatography with diode array detection

Two methods, based on the use of capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC), respectively, were developed for the analysis of the atypical antipsychotic aripiprazole in plasma of schizophrenic patients for therapeutic drug monitoring purposes. Good analytical performances were obtained with the CE method, using uncoated fused silica capillaries and a background electrolyte composed of 50 mM phosphate buffer at pH 2.5. With 20 kV voltage, aripiprazole was detectable at 214 nm within 5 min. The second analytical method, based on HPLC with diode array detection, employed a C8 reversed-phase column and a mixture of a 12.5 mM phosphate buffer, pH 3.5, containing triethylamine and acetonitrile as the mobile phase. Aripiprazole was detected at 254 nm and a complete chromatographic run lasted about 10 min. For both analytical methods loxapine was used as the internal standard and the same plasma sample pre-treatment by means of solid-phase extraction on cyano cartridges was carried out, with extraction yield values always higher than 91.3%. Linear responses for aripiprazole were obtained between 70 and 700 ng mL⁻¹ and precision assays (expressed as relative standard deviation values) were lower than 7.0%. After validation, both methods were successfully applied to human plasma samples drawn from schizophrenic patients undergoing therapy with Abilify^® tablets. Accuracy was satisfactory, with recovery value higher than 91.0%.     

Condensed 2-pyrrolidinone-1,2-oxazines from lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid and β-aryl, β-nitroenamines

The reaction of the lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid 3 with a series of β-aryl, β-nitroenamines unexpectedly afforded 6-aryl-2-benzyl-4-oxa-1-oxo-3a-methoxycarbonyl-2,5-diazaindenes 9a-d, whose structure was determined by analytical and NMR spectroscopical analysis. The structure of 9b was further confirmed by X-ray analysis. A reasonable mechanism for their formation is given.     

PGSE NMR diffusion overhauser studies on [Ru(Cp*)(eta6-arene)][PF6], plus a variety of transition-metal, inorganic, and organic salts: an overview of ion pairing in dichloromethane

PGSE diffusion, 19F, 1H HOESY and 13C NMR studies for a series of [Ru(Cp*)(eta6-arene)][PF6] (1) salts are presented. The solid-state structure of [Ru(Cp*)(eta6-fluorobenzene)][PF6] (1 c) is reported. The extent of the ion pairing and the relative positions of the ions are shown to depend on the arene. For the solvent dichloromethane, new and literature PGSE data for PF6(-) salts of transition-metal, inorganic, and organic salts are compared. Taken together, these new results show that the charge distribution and the ability of the anion to approach the positively charged positions (steric effects due to molecular shape) are the determining factors in deciding the amount of ion pairing. DFT calculations of the charges in four salts of type 1, as well as in a variety of other salts, using a natural population analysis (NPA), support this view. This represents the first attempt, using experimental data, to understand, correlate, and partially explain the various degrees of ion pairing in a widely different collection of salts.