Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 IONIC LIQUID DOPED ELECTROSPUN POLYMER COMPOSITE NANOFIBERS FOR COPPER(II) SENSING Merve Zeyrek a* , Kadriye Ertekin a , Mustafa Göçmentürk a , Yavuz Ergün a , Mehtap Özdemir b , Erdal Çelik b,c a University of Dokuz Eylul, Faculty of Arts and Sciences, Department of Chemistry, 35160, Izmir, Turkey b University of Dokuz Eylul, Faculty Engineering, Department of Metallurgical and Materials Engineering, 35160, Izmir, Turkey c University of Dokuz Eylul, Center for Fabrication and Application of Electronic Materials (EMUM), 35160, Izmir, Turkey Abstract- In this work Copper(II) 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. Recently electrospinning has gained much attention as a simple and reliable process to produce polymer and composite nanofibers, which have small diameter and high aspect ratio and have different types of applications including tissue engineering, biocompatible materials, filters, optical sensor design and drug delivery. For a typical electrospinning setup as shown in Fig. 1, a high voltage, usually more than 5 kV, is applied to the polymer based composite in a spinneret so that free charges accumulate at the liquid-air interface of the capillary. At a critical voltage, the repulsive force within the charged polymer solution is larger than the surface tension and a jet erupts from the tip of the spinneret. As the jet travels through the air, it solidifies leaving behind a polymer fiber to be collected on an electrically grounded support [1]. Electrospun fibers can be functionalized by the use of proper indicator and auxiliary additives for desired purposes. amount of phase transfer agent and varying amounts of plasticizer (DOP) and ionic liquid in 1.5mL of EtOH/CH 3 Cl (v/v 3/1). EC based solutions were prepared by a similar protocol. Figure 2. Chemical structure of MY10 dye Electrospinning was performed at 25 kV voltage and at 0.3 mL/h flow rate. SEM micrographs of PMMA based nanofibers were shown in Fig. 3. Upon exposure to Cu 2+ the MY10 dye exhibited an emission based signal change at 530 nm in direction of signal decrease. The fiber diameters were measured between 634-823 nm for 25% DOP, 25% IL and 50% PMMA containing composites. Photocharacterization, electrospinning fabrication, and sensing capability of PMMA and EC based fibers are discussed. Figure 1. A simplified schematic of the electrospinning process. Copper is the third most abundant element in the human body and is essential in several biological pathways including electron transport, O 2 metabolism and enzymatic catalysis. Oter et al. that offered sensor exhibited remarkable fluorescence intensity quenching upon exposure to Cu 2+ ions at pH 4.0 in the concentration range of 1.0×10 −9 to 3.0×10 −4 M [Cu 2+ ] [2]. In this work the Cu 2+ sensitive dye; N’-3- (4(dimethylamino)phenyl)allylidene)isonicotinohydra zide) (MY10) has been used as sensing agent (See Fig.2). The MY10 dye was doped into poly-methylmethacrylate together with ionic liquid and other additives. Composite fibers were fabricated by electrospinning and characterized by Scanning Electron Microscopy (SEM). Polymer solutions were prepared by mixing 240 mg of poly(methyl methacrylate), 1 mg of MY10 dye, equivalent Figure 3. An SEM micrograph PMMA based nanofiber The preliminary results show that these sensing agents have an order of magnitude higher sensitivity to the Cu 2+ than sensor slides formed from continuous thin films. This is believed to be due to the higher surface area to volume ratio of the electrospun nanofibrous materials. * Corresponding author: mervezeyrek@gmail.com [1] K. Tong, C. Xu, Q. Wang, B. Gu, K. Zheng, L. Ye and X. Li, Chin.Phys.Lett. 25, 4453 (2008). [2] O. Oter, K. Ertekin, C. Kırılmıs and M. Koca, Analytica Chimica Acta 584, 308–314 (2007). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 395
Poster Session, Tuesday, June 15 Theme A1 - B702 What determines the easy-axis in magnetic nanowire arrays 1 *, Giray Kartopu 1, 2 , K.-L. Choy 2 , Ramazan Topkaya 3 1 2 Mechanical, Materials and Manufacturing Engineering, University of Nottingham, Nottingham NG7 2RD, UK 3 Department of Physics, Gebze Institute of Technology, 41400 Gebze, Kocaeli, Turkey Abstract- Magnetic behaviour of nanowire (NW) arrays produced by an electrodeposition method has been investigated by ferromagnetic resonance (FMR) and vibration sample magnetometer (VSM) techniques at room temperature. FMR spectra, their resonance field values as well as magnetic hysteresis curves indicate that the easy-axis shows changes as a function of the nanowires’ geometrical factors, namely the packing density and aspect ratio. The magnetic nanowires are expected to have potential applications in a broad range of topical areas, including magneto-electronic devices, data storage media, magneto/nano-optics, nanosensors, and molecular electronics [1-3]. The magnetic properties of NWs have been investigated by using a variety of techniques [4-7]. Magnetic behavior of nickel (Co) NWs have been reported by electrodeposition techniques on alumina (AAO) templates [8]. Some magnetic NWs have also become very important for their magnetic and microwave absorbing properties [9]. The magnetic properties of NWs with the easy axis along the perpendicular direction have not been studied in detail, e.g. with varying packing density and aspect ratio. The experimental and theoretical coordinate systems for NWs sample geometry; dc, magnetic field, and relative orientation of the equilibrium magnetization are shown in Figure 1. Figure 2. Experimental (open /closed symbols) and calculated (full red lines) resonance fields for NWs. Magnetic NWs exhibit uniaxial anisotropy, usually with the easy axis along the wire length in small diameters (open symbols in fig. 2) or aligned perpendicular to the wire axis as in thicker diameters (closed symbols in fig. 2). The support of the Scientific and Technological Research Council of Turkey gratefully acknowledged. *Corresponding author: yalcin@nigde.edu.tr Figure 1. (a) Sketch of the sample geometry (b) Sample parameters used in calculating the packing factors (P). (c) Schematic representation of a hexagonal nanowire array exhibiting seven wires. The dashed lines point out the six-fold symmetry. In this work, we have studied dense arrays of NWs by vibrating sample magnetometry (VSM) and techniques ferromagnetic resonance (FMR) as functions of different geometric factors (e.g. packing factor, P, and and applied field direction at the room temperature (RT) [10]. The FMR technique has proved to be a very powerful technique which can provide information on the magnetization, magnetic anisotropy, g-value and relaxation times, as well as the damping in magnetization dynamics [11-12]. In the frame of relevant theories FMR results, its magnetic resonance fields and magnetic hysteresis were investigated in detail. The magnetic resonance field, coercive field, magnetization values, magnetic anisotropies and relaxation time of wires are presented and discussed in the context of geometrical factors. [1] Fabrication and Applications of Metal Nanowire Arrays Electrodeposited in Ordered Porous Templates, in Nanowires, Ed. A. Lazinica, In-Tech, Vienna (2010). [2] 2T, Tuominen, “FMR Studies of Co Nanowire Arrays”, Nanostructures Magnetic Materials and Their Applications, Kluwer Academic Publisher. Nato Science Series. Mathematics, Physics and Chemistry. Volume: 143. Page:347–356, (2004). [3] G. Kartopu, M. Es-Souni, A.V. Sapelkin, and D. Dunstan, Phys. Stat. Solidi (a), 203 (10) (2006) R82; J. Nanosci. Nanotech. 8 (2008) 931 [4] -souni J. Magn. Magn. Mater. 321 (2009) 1142, and references therein. [5] P. M. Paulus, F. Luis, M. Kröll, G. Schmid, L. J. De Jongh, J. Magn. Magn. Mater. 224 (2001) 180. [6] K. Niels, et al., J. Magn. Magn. Mater. 249 (2002) 234. [7] Bal, M.T. Touminen. J. Magn. Magn. Mater. 272-276 (2004) 1684. [8] - Phys. 103 (2008) 093915. [9] M. Vazquez, M. Hernández-Vélez, K. Pirota, A. Asenjo, D. Navas, J. Velázquez, P. Vargas and C. Ramos. Eur. J. Phys. B 40 (2004) 489 [10] -L. Choy, R. Topkaya, S. Kazan and -axis in Ni nanowires” prepared (2010) [11] öz, F. Yildiz, Y. Yerli and B. [12] Stat. Solid (a) 203 (2006) 1539. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 396
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