Agarose Hydrogels Enriched by Humic Acids as the Complexation Agent

The transport properties of agarose hydrogels enriched by humic acids were studied. Methylene blue, rhodamine 6G and Cu(II) ions were incorporated into hydrogel as diffusion probes, and then their release into water was monitored. Cu(II) ions as well as both the dyes studied in this work have high affinity to humic substances and their interactions strongly affected their diffusion in hydrogels. It was confirmed that humic acids retarded the transport of diffusion probes. Humic acids’ enrichment caused the decrease in the values of effective diffusion coefficients due to their complexation with diffusion probes. In general, the diffusion of dyes was more affected by the complexation with humic acids in comparison with Cu(II) ions. The effect of complexation was selective for the particular diffusion probe. The strongest effect was obtained for the diffusion of methylene blue. It was assumed that metal ions interacted preferentially with acidic functional groups. In contrast to Cu(II) ions, dyes can interact with acidic functional groups, and the condensed cyclic structures of the dye probes supported their interactions with the hydrophobic domains of humic substances.

Characterization of Co(II)-PAMAM dendrimer complexes with polypropylene oxide core by using UV-VIS spectroscopy

<p>The aim of this study was to characterize poly(amidoamine) (PAMAM) dendrimer complexes of Co(II) ions by using UV-Vis spectroscopy. For this aim, a generation-4 polypropylene oxide (Jeffamine^® T-403) cored and amine-terminated PAMAM dendrimer (P₄) was used as a model complexation agent. Optimum complexation condition for P₄ was determined by potentiometric and spectroscopic titration studies. Extent of protonation (EOP) of the amino groups of P₄ was determined from the potentiometric titration data and validated with spectroscopic titration data. The results indicated that pH 8 was the optimum dendrimer aqueous solution media, where the available number of tertiary amines present in P₄was the highest for possible metal complexation. At the optimized conditions, UV-Vis characterization of the Co(II)-P₄ complexes was performed and 585–635 nm <em>d-d</em> transition bands were observed as the characteristic complexation bands of the tertiary amine groups of P₄ with Co(II) ions. Obtained Co(II)-P₄ complexes might be considered for the development of magnetic resonance image (MRI) improvers or MRI contrast agents.</p><p class="Abstract"><span lang="EN-US"><br /></span></p>

Study on CMP Slurry and Technique of Silicon Dioxide Dielectric for ULSI

SiO2 is a kind of widely used dielectric material in ULSI and its chemical mechanical planarization (CMP) is one of the most difficult processes. In this paper, the CMP mechanism and the effect of abrasive on SiO2 dielectric were analyzed; the different factors of affecting the CMP were analyzed. A kind of organic alkali was chosen to act as the pH regulator and complexation agent to enhance the chemical effect. The silica sol was selected as abrasive to realize no contamination, low viscidity, proper hardness and easy to clean. The effect of different concentration of abrasive on the removal rate and surface performance were studied. Further more the influence of polishing slurry flow and surfactant on removal rate were analyzed. The final planarization was realized.