Showing papers by "Ivan Sondi published in 2001"

Homogeneous Precipitation of Calcium Carbonates by Enzyme Catalyzed Reaction.

Abstract: Catalytic decomposition of urea by urease in aqueous calcium chloride solutions was used to rapidly prepare calcium carbonate polymorphs at room temperature. The nature of the resulting particles depended on the concentration of the enzyme and, in a strong manner, on the agitation of the reacting solutions. In an undisturbed system an amorphous precipitate is formed first, which readily crystallized to vaterite and upon aging changed to calcite. Under the influence of magnetic stirring, the amorphous phase could be not observed; instead smaller particles were initially obtained, which aggregated to vaterite and calcite. Similarly, the application of ultrasonic energy produced small vaterite particles at the early stages. It is apparent that enzyme macromolecules are important in the development of calcite faces and, as such, they exert significant influence on calcite morphology, without being present in detectable amounts in the resulting solids. Copyright 2001 Academic Press.

Semiconductor nanoparticles for analysis of blood cell populations and methods of making same

Abstract: A semiconductor nanoparticle for use in analysis of biological samples is described. This semiconductor nanoparticle is composed of an aminodextran which is bound to at least one nanoparticle of the formula (X Y) n wherein X is selected from the group comprising Cd 2+ , Hg 2+ , and Zn 2+ and combinations thereof, and Y is selected from the group comprising S 2− , Se 2− and Te 2− and combinations thereof; and n=approximately 50 to 1000. Also provided are methods of making these semiconductor nanoparticles and methods of making conjugates composed of these semiconductor nanoparticles linked to ligands. Also described are uses for the conjugates in a variety of biological assays.

Precipitation of Monodispersed Basic Iron(III) Sulfate (Sodium Jarosite) Particles

Abstract: Uniform sodium jarosite particles were obtained by forced hydrolysis of ferric salt solutions to which copper sulfate, sodium sulfate, and sodium nitrate were added. It was found that at the same concentrations of ferric and sulfate ions the particle size and yield decreased with the lowering of the concentration of sodium ions, but the morphology remained the same. At a sufficiently small content of sodium in the reacting solution, no precipitation of sodium jarosite particles was observed. Finally, chemical and XRD analyses showed that small amounts of copper ions are incorporated in the crystal lattice which, with the change in the Na+/H3O+ ratio, slightly affected the structure of this mineral, but not its other properties.

Encapsulated inorganic resist technology applied to 157-nm lithography

Abstract: In order to increase plasma etch selectivity in traditional single layer organic resists SiO 2 nanoparticles have been added to typical 248-nm resist formulations. Formulation modifications are necessary due to the dissolution acceleration effect of the particles. Surface functionalization of the nanoparticle surfaces with organic groups lessens this effect and allows the inclusion of acid labile groups. This allows for a wider formulation window and limits unexposed film thickness losses (UFTL). Both t-butyl ester groups and poly(t-butyl acrylate) have been used to achieve this effect. Encapsulated inorganic resist technology (EIRT) can be used as a single layer hard mask compatible with existing resist processing steps and replace complex and costly multilevel resist approaches. Lithographic evaluations have been performed with electron beam, and with 248 nm and 157-nm projection systems. Greater transparency at 157 nm is achieved by the addition of these materials, thus enabling the use of thicker films. High resolution imaging is demonstrated at these wavelengths.