Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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  • Article
    Citation - WoS: 17
    Citation - Scopus: 21
    Humidity Sensing Properties of Chitosan by Using Quartz Crystal Microbalance Method
    (American Scientific Publishers, 2012) Havare, A. Kemal; İlgü, Hüseyin; Okur, Salih; Şanlı Mohamed, Gülşah
    Humidity adsorption kinetics of chitosan films was investigated by quartz crystal microbalance (QCM) technique. In this study, chitosan was synthesized from chitin by deacetylation process in 2.0% (v/v) acetic acid solution and then coated on QCM to measure humidity response. The Langmuir model was used to determine the adsorption rates and Gibbs free energy for various relative humidity between 11% and 94%. The average Gibbs free energy for adsorption was obtained as 12.93 kJ/mol. Our reproducible experimental results show that chitosan films are very sensitive to relative humidity changes at room temperature. Copyright © 2012 American Scientific Publishers All rights reserved.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Effect of Alkali Metal Hydroxides on the Morphological Development and Optical Properties of Ceria Nanocubes Under Hydrothermal Conditions
    (American Scientific Publishers, 2011) Kepenekçi, Özlem; Eanes, Mehtap; Demir, Mustafa Mustafa
    Nanocrystalline cerium(IV) oxide (CeO2, ceriaceria) particles were produced via the hydrothermal treatment of cerium nitrate hexahydrate with various alkali metal hydroxides (MOH: M = Li, Na, K). Experimental conditions such as [MOH], reaction temperature, and reaction time were studied. Particle morphology as well as size of crystallites was precisely controlled by choice of experimental conditions. While rod-shaped particles were obtained at 120 C, well-defined nanocubes were formed at higher temperatures regardless of the choice of MOH. Examination of particle growth kinetics, in the final stages of crystallization, showed that particle growth rate is controlled by two different mechanisms. Grain boundary diffusion controls the particle growth in the presence of NaOH with an activation energy of 113.8 kj/mol and surface diffusion for LiOH ad KOH with the activation energy of 43.0–150.9 kj/mol, respectively. In addition, the particles exhibit strong violet and blue emissions at 400 nm and 370 nm. The former emission originates from excitation of a wide band gap of CeO2. The latter one is attributed to the trivalency of the cerium ion and appears to be sensitive to all the experimental conditions studied. Both extending reaction time and increasing temperature reduce the intensity of the 370 nm emission and increase the intensity of the 400 nm emission.