Journal of Nanoanalysis

5

Authors: Monireh Hajmalek, Mohammad Sajjad Khalili, Karim Zare and Omid Zabihi

The acid dissociation constants of the hydroxyl groups in 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetrasulphonic-calix[4]arene (SC4) were determined at 25οC by a combination of potentiometric and spectrophotometric titration method. The first and second acid dissociation constants (pKa1, pKa2) were found to be 3.19 and 12.1, which demonstrated pKa shift due to intramolecular hydrogen bonding interactions among hydroxyl groups in SC4.

8

Authors: Seyed Mojtaba Mostafavi, Masoumeh Piryaei, Ahmad Rouhollahi and Ali Mohajeri

In this study, a new silica gel based adsorbent was fabricated and its ability in separation and quantification of alkanes mixture was investigated. Silica gel (SiO2) is a polar absorbent which is mainly used to separate polar compounds. Also, the carbon materials such as activated carbon and recently carbon nanotube (CNTs), have been widely used for separation of nonpolar materials. Carbon nanotubes are nanosized carbon-based sorbents that have a high surface area and a large aspect ratio and are known to be stable at high temperatures. It is, therefore, conceivable to use of their unique properties in gas chromatography. In this work, a MWCNT-Silica gel nanocomposite was prepared by Sol-Gel process and it was used as stationary phase in gas chromatography for separation of alkanes mixture. In first part,ability of silica gel adsorbent was studied and then results were compared with new MWCNT-Silica gel nanocomposite. Finally, a quantitative investigation was done on a LPG sample and propane, 2-methylpropane, nbutane,2,2-dimethylpropane, 2-methylbutane and n-pentane were measured by standard addition.

10

Authors: Mehdi Zamani, Hossein A. Dabbagh

In this study, the adsorption behavior of the primary, secondary and tertiary alcohols over nanoscale (1 0 0) surface of defect spinel γ-alumina was investigated with the aid of density functional theory (DFT) at BLYP/DNP level of calculation. The influence of different substituents including alkyl, cycloalkyl, allyl and aryl were analyzed for free and adsorbed alcohols to shed light the adsorption selectivity of these compounds over γ-alumina surface. These results indicate that more branches at a position of alcohol favor the adsorption, while a decrease in adsorption energy is achieved for the alcohols containing the substituents at the β position. The tertiary alcohols are adsorbed over the surface stronger than secondary and primary alcohols. Alcohols with larger alkyl chains have greater adsorption energies. Also the aryl alcohols are adsorbed over the surface better than the alkyl and allyl moieties.