Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 3 Nanostructures for lithium ion batteries 1* 1 , Erdal Sönmez 1 , 2 and Mehmet Ertugrul 3 1 K. K. Education Faculty, Department of Physics, Ataturk University, Erzurum 25240, Turkey 2 K. K. Education Faculty, Department of Chemistry, Ataturk University, Erzurum 25240, Turkey Engineering Faculty, Department of Electric-Electronic, Ataturk University, Erzurum 25240, Turkey Abstract—Nanostructure materials are currently of interest for lithium ion battery because of their high surface area, porocity, etc. It was observed that lithium ions transport, battery stability and batteries specific capacities increased by using nanostructures. Moreover depending on the characteristic of nanostructures internal resistance along the path of electronic conductivities has been decreased and that of the high charge/discharge rate has been observed. Nowadays nanomaterial’s sciences have started to use for lithium ion battery applications [1,2]. Recently the nanostructured materials have used to be energy storage devices such as high charge/discharge rate lithium ion batteries [3]. This newly developed energy storage devices can be used for requiring high power applications such as electric and hybrid electric vehicles. The reason for that is advantage of this type next-generations battery, electrode materials used in battery have high charge/discharge rate. Rechargeable lithium ion batteries consist of positive electrode (cathode), negative electrode (anode) and Li-ion containing electrolyte [4]. As the classic lithium ion batteries LiCoO 2 cathode material and graphite as the anode materials were used. During the charge process Li ions are extracted from the LiCoO 2 and continuously inserted graphic carbon electrode. Fig. 1. Schematic of an insertion electrode based rechargeable lithium ion battery. Discharge process occurs in reverse charge process. So, Li ions are extracted from the negative electrode a continuously inserted positive electrode. The classical insertion/extraction process is shown in Fig. 1 [4]. The cathode half reaction is: LiCoO 2 1-x CoO 2 + xLi + + xe - The anode half reaction is : xLi + + xe - +6C x C 6 Overcharge up to 5.2 V leads to the synthesis of cobalt (IV) oxide, as evidenced by X-ray diffraction (XRD) [5]. LiCoO 2 + +CoO 2 In lithium ion batteries lithium ions are transported to anode oxidizing of transition metal Co from Co +3 to Co +4 in LiCoO 2 a cathode material and transported to cathode with this metal Co reducing from Co +4 to Co +3 during discharging As active cathode materials in lithium ion batteries use of LiMO2 type structure is common. (M: Co, Ni, Mn, V) According to the charge/discharge state these structure tend to give Li + or receive Li + . Materials also used as cathode should be easily prepared, must have high operating voltage and high capacity. The research purposed of synthesizing and development of LiCoO 2 materials is to improve the performance of these materials. The purpose of these studies was prepared as LiCoO 2 particles of various sizes and dimensional. Template –prepared LiCoO 2 have been demonstrated to show much improved electrode performance than that their bulk form and even outperform the nanoparticles counterparts obtained without template [6]. LiNiO2, which is used as a cathode material, is attractive for the researchers for having low redox potential and being affordable. Yet preparing LiNiO 2 stoichiometrically is a rather hard process. So, doping cobalt to LiNiO 2 enables to have the suitable cathode material. As the result of these works, the XRD results of the structures of LiNixCoyO2 nanotube doped with LiCoO 2 and cobalt are similar to the XRD result of these materials bulked state. The difference between these two can be regarded as in the XRD results of the nanotubes, the cells are broadened and the bulk density is lowered. The reason of these differences is the size of the small particles of the nanostructures.[7] *Corresponding author: mehmetyilmaz@atauni.edu.tr [1] J. Maier, et al., Nat. Mater, 4 805 (2005). [2] A.S. Arico, et al., Nat. Mater.4 366, (2005) . [3] H. Zhou, et al., Angew. Chem. Int. Ed.44 797, (2005) . [4] C. Jiang et al., Nanotoday 4 24(2006). [5] G.G. Amatucci et al., J.Elect. Soc. 143 1114-1123 (1996). [6] E. Ozcelik and G. Ozkan, J.Fac.Eng.Arch., Gazi.Univ. 21 423- 425 (2006). [7] F. Cheng et al. Chem. Mater. 20 667-681 (2008). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 268
Poster Session, Tuesday, June 15 Theme A1 - B702 Synthesis and Characterization of ternary PbS x Se 1-x thin films via Electrochemical Co-deposition Methods Fatma Bayrakçeken, Ümit Demir, Tuba Öznülüer* Department of Chemistry, Arts and Sciences Faculty, Atatürk University, Erzurum 25240, Turkey Abstract - Thin films of PbS x Se 1-x were electrodeposited on Au (1 1 1) substrates by using a practical electrochemical method, based on the simultaneous underpotential deposition (UPD) of Pb, S and Se from the same solution containing Pb(CH 3 COO) 2 ,SeO 2 ,Na 2 S and EDTA at a constant potential. PbS x Se 1-x nanofilms were characterizated by X-ray diffraction (XRD), atomic force microscopy (AFM), FTIR spectroscopy techniques. AFM, XRD, and FTIR results revelead that ternary lead chalcogenide nanofilms having high crystallinity were deposited at a kinetically preferred (200) orientation on the Au (111) substrates. The lead salts (PbS, PbSe and PbTe) and their alloys are narrow band gap semiconductors which have been studied in the field of IR detection and thermoelectric devices [1]. More recently, further interest in the different lead-salt alloys has been created as a result of experiment in high-resolution spectroscopy and in air pollution measurement using tunable lead-salt diyote lasers. In addition to infrared detectors and emitters, narrow gap semiconductors have potential application in magnetoresistive and Hall effect devices as well as in thermoelectric devices. Emphasis is placed on the ternary alloy systems of PbS x Se 1-x , Pb 1-x Sn x Se, PbSn 1-x Se and Hg 1-x Cd x Te due to scope for regulation of their physico-chemical properties through variation of composition. It is possible to vary such electrophysical characteristics as type of conductivity concentration of main current carrier, band gap (E g ) etc. Individually, both the lead salt compounds PbS and PbSe have been widely used as radiation dedectors sensitive to near-infrared wavelengths[2]. Mixed compounds of the form PbS x Se 1-x, however, offer potentially useful dedectors of intermediate wavelength, broad band, and perhaps unique response. Lead chalcogenides films have been prepared by atomic layer epitaxy (ALE), chemical bath deposition (CBD), and electrochemical deposition[3]. Demir et al. have recently reported atom-by-atom electrochemical codeposition method to prepare PbS[4], ZnS[5] and CdS[6] thin films on Au(111). In this study, we also have shown that the highly oriented PbS x Se 1-x thin films have been successfully prepared by an electrochemical co-deposition method, which based on the upd or surface-limited reaction of Pb, Se and S at pH 4.5. The appropriate co-deposition potentials based on the underpotential deposition (upd) potentials of Pb, Se and S have been determined by the cyclic voltammetric studies. The films were grown from an electrolyte of 2.5 mMPb(CH 3 COO) 2 ,2 mM Na 2 S, 0.3 mM SeO 2 and EDTA in acetate buffer (pH 4.5) at a potential of -0.02 V vs. Ag|AgCl (3 M KCl). The bandgap values of the PbS x Se 1-x films were determined by absorbance measurement in the wavelength range 1280-5000 nm using Fourier transform infrared spectrophotometer. X-ray diffraction patterns were used to determine the sample quality, crystal structure and lattice parameter of the films. PbS x Se 1-x thin films were found to be single crystalline in nature as confirmed by XRD patterns and have a predominantly rock salt (NaCl) structure (Figure 1). The morphological investigation of PbS x Se 1-x films revealed that the film growth follows a 3D nucleation and growth mechanism. In conclusion, morphology and structure analyses confirm that high-quality ternary thin films could be prepared by this UPD-based electrochemical technique. Intensity/ a.u. PbSe xS 1-x (200) Au(111) 20 25 30 35 40 45 50 55 60 2/deg Figure 1. XRD patterns of PbSe x S 1-x thin film on Au (111) electrode after potential controlled deposition at -400 mV, pH 4.5; (a) 30 minutes and (b) 1 hour. *Corresponding author: toznuluer@gmail.com [1]S. Kumar, M. Hussain, P. T. Sharma, M. Husain Journal of Physics and Chemistry of Solids 64, 367 (2003) [2]B. A. Riggs J. Electrochem. Soc. 107, 708 (1967). [3]M. Alanyalioglu., F. Bayrakceken, Ü. Demir, Electrochim. Acta 105, 10588 (2009) [4]T. Oznuluer, I.Erdogan, I.Sisman and U Demir Chemistry of Materials 17, 935 (2005) [5] T. Oznuluer, I.Erdogan, I.Sisman and U Demir Lagmuir 22, 4415 (2006) [6] İ.Sisman,M.Alanyalioglu and Ü.Demir J.Phys.Chem.C 111, 2670 (2007) b a 6th Nanoscience and Nanotechnology Conference, zmir, 2010 269
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