Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 SPECTROFLUORIMETRIC DETECTION OF DISSOLVED CARBON DIOXIDE BY ELECTROSPUN POLYMER NANOFIBERS Sibel Aydoğdu 1* , Kadriye Ertekin 1 , Mustafa Göçmentürk 1 , Yavuz Ergün 1 , Aslıhan Süslü 2 , Ümit Cöcen 2 1 University of Dokuz Eylul, Faculty of Arts and Sciences, Department of Chemistry, 35160, Izmir,Turkey 2 University of Dokuz Eylul, Faculty Engineering, Department of Metallurgical and Materials Engineering, 35160, Izmir,Turkey Abstract- In this work CO 2 sensing nanofibers were produced. Fluorescence sensing agent and auxiliary additives were doped into PMMA and EC matrices. Presence of ionic liquid in the matrix material enhanced electrospinning process and provided higher analytical signal. Electrospun fibers find applications in the making of functional fiber composites, electronic and optical devices, and as biotechnological materials [1]. Electrospinning is an effective method by which polymer nanofibers (with submicron scale diameters) can be formed by accelerating a charged polymer jet under a high voltage electric field [2]. As this droplet flows in air, the solvent evaporates leaving behind a fiber that can be electrically oriented on a substrate. Electrospun fibres can be functionalized by the use of proper indicator and auxiliary additives for desired purposes. Most of the optical CO 2 sensor designs utilize indicator dyes with pKa values between 7.4 and 10.0, which are doped into the polymer matrices. In such designs, mainly absorption or emission based measurements were performed on thin film surface or dip-coated fiber optics. In this work quenching-based optical chemical sensors were produced by the electrospinning technique. A series of dissolved CO 2 sensitive nanofibers with various compositions of poly-methyl-methacrylate (PMMA), ethyl cellulose (EC), plasticizer and ionic liquid (1-ethyl-3- methylimidazolium tetrafluoroborate) were produced and characterized by Scanning Electron Microscopy (SEM). The CO 2 sensitive dye N’-[(1Z)-(9-methyl-9Hcarbazol-3-yl)methylene]isonicotinohyrazide (MY9) has been used as sensing agent. (See Fig.1). Polymer solutions were prepared by mixing 240 mg of ethyl cellulose, 1 mg MY9 dye, equivalent amount of phase transfer agent, varying amounts of plasticizer (DOP) and ionic liquid in 1.5mL of tetrahydofuran (THF). PMMA based solutions were prepared by a similar protocol. Figure 1. Chemical structure of MY9 dye Electrospinning was performed at 25 kV voltage and at 0.3 mL/h flow rate (See Fig.2) SEM micrographs of EC based nanofibers were shown in Fig. 3. Upon exposure to dissolved CO 2 the MY9 dye exhibited an emission based signal change at 440 nm in direction of signal decrease. Photo-characterization, electrospinning fabrication, and sensing capability of PMMA and EC based fibers are discussed. The fiber diameters were measured between 322-688 nm for 40% DOP, 10% IL and 50% ethyl cellulose containing composites. Figure 2. An SEM micrograph EC based nanofiber Figure 3. A simplified schematic of the electrospinning process. This study was supported by TUBITAK Münir Birsel National Graduate Scholarship Programme and TUBITAK project-104M268. *Corresponding author: sibel.aydogdu@ogr.deu.edu.tr [1]. V. Gunaranjan, M. Saravanababu, P. Victor, N. Omkaram, A. M., Pulickel and L. J. Robert, Biomacromolecules., 7, 415-418 (2006). [2] S. Piperno, L. Lozzi a , R. Rastelli, M. Passacantando and S. Santucci, Applied Surface Science, 15, 252, 5583-5586 (2006). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 389
Poster Session, Tuesday, June 15 Theme A1 - B702 The effect of transition metals on electronical properties of nanocrystalline indium oxide films by experimental and theoretical approaches Hossein Asghar Rahnamaye Aliabad, 1* Seyed Mohammad Hosseini 2 and Mohammad-Mehdi Bagheri-Mohagheghi 3 1 Department of Physics, Sabzevar Tarbiat Moallem University, Sabzevar, Iran 2 Department of Physics, Ferdowsi University of Mashhad, Mashhad, Iran 3 Department of Physics, Damghan University of Basic Sciences, Damghan, Iran Abstract— Electronical properties of pure nanocrystalline indium oxide films and its alloys with Y and La have been investigated using experimental and theoretical methods. The Full Potential Linearized Augmented Plane Wave (FP-LAPW)approach was used with the Local Density Approximation plus Hubbard potential (LDA+U). Theoretical calculations have indicated that there are two band gaps for pure Indium Oxide. The band gap is increased with Y dopant while decreases with La dopant. These impurities increase the value of the electron effective mass in the bottom of the conduction band. We have also prepared samples by spray pyrolysis method at 500 degree centigrade as thin films. The obtained optical band gap for pure indium oxide sample is 4.1 eV. It was found that adding Y and La impurities increases and decreases the band gap, respectively. Increasing and decreasing procedure of the band gap is conformed to both theoretical and experimental methods and also is in good agreement with others. Over the last two decades there has been an attracted increasing attention in both fundamental research and industrial applications of transparent conducting oxides (TCOs). These materials have many applications in numerous devices such as flat panel displays, solar cells, gas sensors and low-emissive windows [1, 2]. Among various transparent oxides the indium tin oxide (ITO), indium oxide (In 2 O 3 ), tin oxide (SnO 2 ), and zinc oxide (ZnO) are the dominant TCOs. Tin-doped indium oxide (ITO), with a typical electrical conductivity and transparency in the visible region is usually used in thin coating form. Also the developments of polycrystalline and amorphous transparent conducting oxide semiconductors, used for practical thin-film transparent electrode applications, have been under discussion in the literature during the last few years [3, 4]. In this work, We have studied, the effect of Y and La on electronical properties of In 2 O 3 nanostructure by using two methods spray pyrolysis metod and Local density approximation (LDA+U) based on the density functional theory (DFT). Indium oxide can exist in three different phases [5] characterized by space group symmetries I2 1 3, Ia 3 and R 3 . In 2 O 3 with space group Ia 3 and the band gap of Eg =3.7 eV is similar to many trivalent rare-earth oxides, such as Yb 2 O 3 and Dy 2 O 3 . This phase of indium oxide has two nonequivalent six-fold coordinated cation sites. The two cation sites are referred to as equipoints “b” and “d”. The sites of the cations are coordinated to six oxygen anions at three different distances, which lie near the corners of a distorted cube with two empty ions along one face diagonal. The unit cell contains 80 atoms and crystallized in cubic bixbyite structure. We substituted the impurities in b positions, since at low temperatures the impurities prefer to sit at b positions [6]. The Y an La -doped In 2 O 3 thin films have been deposited on glass substrates at 500 °C with 250 nm thickness. For deposition of In 2 O 3 films, we used the technique of spray pyrolysis. The carrier gas used in all the experiments was N 2 . These films have been prepared by sol–gel technique that is a suitable chemical method for the preparation of nanostructures. Initial solution composed of In(NO 3 ).4H 2 O(0.08 wt%), H 2 O(0.44 wt%), HNO 3 (0.04 wt%) and CH 3 CH 2 OH(0.44 wt%). For doping of Y and La, we have used an aqueous ethanol solution consisting of Y(NO 3 ).5H 2 O and N 3 O 9 La.6H 2 O with various doping levels from 0 to 25 and 33 wt% in solution. The optical absorption and transmission spectra of films were recorded using a UV visible Spectrophotometer and X-ray diffraction was used to characterize the crystal structure of the films. The optical absorption edge for undoped In 2 O 3 film by spray pyrolysis lies at 4.1 eV. This result is good agreement with others [7].The effect of Y(In 1.85 Y 0.15 O 3 ) and La (In 1.85 Y 0.15 O 3 ) with 15 wt% increases and decreses optical band gap to 4.3 eV and 4.05 eV respetively. Obtained band gap for In 2 O 3 by density functional theory (DFT) is 1.43 eV. This result is good agreement with others [5]. The effect of Y (In 1.5 Y 0.5 O 3 ) and La (In 1.5 La 0.5 O 3 ) increases and decreses band gap to 1.88 eV and 1.24 eV respetively. The experimental and theoretical results are good agreement with each other. *Corresponding author: h_rahnamay@yahoo.com [1] T. J. Coutts, J. D. Perkins, D. S. Ginley and T. O. Mason,, Presented at the 195th Meeting of the Electrochemical Society, Seattle, Washington May 2-6, (1999). [2] D. S. Ginley and C. Bright (Guest Editors), "Transparent Conducting Oxides" MRS Bulletin, 15-18, August (2000). [3] T. Minami, , Semicond. Sci. Technol., 20 ,S35-S44 (2005) [4] N. G. Lewis and D. C. Paine, , MRS Bulletin- Materials Research Society, Vol. 25; Part 8,22-27 (2000). [5]S. Zh. Karazhanov, P. Ravindran, P. Vajeeston, A. Ulyashin, T. G. Finstad and H. Fjellvåg, , Phys. Rev. B 76, 075129(1-13) (2007). [6]J. E. Medvedeva, Phys. Rev. Lett. 97, 086401(1-4) (2006). [7] Prathap, P., Subbaiah ,Y.P.V., Devika ,M.and Ramakrishna Reddy, K.T., Materials Chemistry and Physics 100, pp. 375–379(2006). Figure: Non-equivalent cation sites and anion vacancies in In 2 O 3 . 6th Nanoscience and Nanotechnology Conference, zmir, 2010 390
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