Chemical Engineering / Kimya Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/14

Browse

Filters

20142

Settings

Language: search.filters.language.enSubject: search.filters.subject.Luminescence

Search Results

Now showing 1 - 2 of 2
  • Book Part
    Control of the Particle Size and Purity of Nano Zinc Oxide
    (Taylor & Francis, 2014) Özmıhçı Ömürlü, Filiz; Özmıhçı, Filiz; Balköse, Devrim; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Effects of template, mechanical mixing and/or ultrasound mixing on the size of the ZnO crystals obtained by precipitation at 30 °C from aqueous zinc chloride and potassium hydroxide solutions were investigated by 2k factorial design. Precipitation method is employed to synthesize nano zinc oxide particles. Monodisperse nano ZnO having 29 nm particle size was produced by adding triethyl amine and applying simultaneously mechanical and ultrasound mixing. The surface area and the density of the powder were 21 m2/g and 4.8 g/cm3. It contains 5.2% impurities present as CO3-2 and bound OH- groups. Volumetric resistivity was found as 1.3 × 107ohm cm. Absorption spectrum of the powder showed absorption peak at 353 nm. The room temperature fluorescence spectrum of the powder revealed a strong and sharp UV emission band at 391 nm due to free exciton or bound exciton of ZnO and a weak and broad violet emission band at 405 nm due to zinc vacancies.
  • Article
    Citation - Scopus: 1
    Optical and Surface Properties of Zinc Oxide Nanoparticles Dried by Conventional and Supercritical Ethanol Drying Techniques
    (Research India Publications, 2014) Egbuchunam, Theresa Obuajulu; Yetgin, Senem; Balköse, Devrim; Balköse, Devrim; Özmıhçı, Filiz; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Zinc oxide (ZnO) nanoparticles were synthesized by conventional (ZnO-A) and supercritical ethanol drying (ZnO-B). Nitrogen adsorption/desorption analyses were performed to determine the surface areas of the powders. The specific surface area was 28.30m2/g and 10.61 m2/g for ZnO-A and ZnO-B respectively. The powders adsorbed very small amount of CO2with the conventionally dried powder adsorbing more CO2. Supercritical ethanol dried ZnO had ethanol on its surface which was eliminated by vacuum application at room temperature. Both powders had OH groups which were eliminated on heating up to 500°C under vacuum. However, OH groups were present in lower amounts in supercritical ethanol dried ZnO. The powders were characterized by UV-VIS optical absorption and room temperature photoluminescence spectroscopic analyses. The UV-VIS absorption spectrum showed an absorption band at 375nm due to ZnO nanoparticles. The photoluminescence spectrum of ZnO excited at 380nm exhibited three emission peaks: one at 424nm and 490nm corresponding to band gap excitonic emission and another located at 520nm due to the presence of singly ionized oxygen vacancies.