Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Thermodynamical Properties of Pd-Au and Pt-Au Core-Shell Nanoparticles: A Molecular Dynamics Study S. Kaya 1 , S.Ozdemir Kart 1* , T. Cag 2 1 2 Department of Chemical Engineering, Texas A&M University, Texas, TX 77843-3122, USA Abstract- The thermodynamical properties of Pt-Au and Pd-Au core-shell nanoparticles are studied at constant temperature and constant volume (TVN) molecular dynamics simulations with the use of quantum corrected Sutton-Chen potential energy function. The nanoparticles have the spherical core-shell structures with two different diameters of 5 nm and 10 nm. The spherical Pd or Pt is covered with the spherical Au shell with five different concentrations. The pure metals (Pd, Pt and Au) with the same particle sizes are also studied to compare with the results of core-shell nanoparticles. The melting temperature is determined by examining the behaviour of the total energy as a function of the temperature. Simulation results such as kinetic energy, potential energy, heat capacity, and latent heat of the fusion are presented. The effects of the concentration of shell atoms on the physical properties for both core-shells interested in this study are also investigated. In recent years, metallic nanoparticles attract growing interest due to their unique properties -differing greatly fro m bulk- resulting fro m the large fraction of surface atoms. Furthermore, core-shell nanoparticles are of particular interest in applications ranging from catalysis to optical, magnetic and electronic applications because the properties of nanoparticles can change with not only size and but also chemical composition [1-4]. Core-shell nanoparticles are made up of core material coated with another material. The design of new nanoparticle functionalized with size, composition and atomic distribution necessitate the understanding of the structure and properties of core-shell nanoparticles. In this study, we are particularly interested in the thermodynamic and structural properties of both Pd-Au and Pt-Au core-shell nanoparticles. We have performed molecular dynamics simulations for five different core-shell concentrations by utilizing Quantum Sutton-Chen potential [5-6]. They are arranged as Pd(Pt) n-xAu x , where, n is the mu ltip lier of the lattice parameter to produce the radius of the nanoparticles. Here, n is taken as 6 and 12, respectively, for 5 nm and 10 nm core-shells while x is set as 0, 1, …6 for the small size core-shell and 0, 2, 4, … 12 for the large size of the one. The total energy, melting temperature, specific heat and latent heat of the fusion are calculated as a function of temperature and concentrations. Atomic distribution of these core-shell nanoparticles at various temperatures are shown in Figure 1. Melting temperatures of the core-shell nanoparticles increase with not only the size of the spherical nanoparticles, but also the number of the core atoms of Pd or Pt. Core atoms such as Pd coated by Au are redistributed among the Au shell atoms at high temperature as shown in Figure 1. c) and d). Figure 1. Typical snapshop of Pd 4 Au 2 core-shell paricles: halfdisplayed a)- 300K, b) 1200 K, c) 2000 K and d) full-structure displayed at 2000K *Corresponding author: ozsev@pau.edu.tr [1] F. Delogu, Phys. Rev. B 76, 235421 (2007). [2] E. E. Zhurkin, T. V. Hoof, and M. Hou, Phys. Rev. B, 75, 224102 (2007). [3] Y. H. Chui, G. Grochola, I. K. Snook, and S. P. Russo. Phys. Rev. B 75, 033404 (2007). [4] Z. Yang, X. Yang, and Zhijun Xu, J. Phys. Chem. C 112, 4937 (2008). [5] Y. Qi, T. Cagin, W. L. Johnson, W. A. Goddard III, J. Chem. Phys. 115, 385 (2001). [6] H H Kart, G. Wang, I. Karaman an (2009). a) 300 K b) 1200 K c) 2000 K d) 2000 K 6th Nanoscience and Nanotechnology Conference, zmir, 2010 256
Poster Session, Tuesday, June 15 Theme A1 - B702 Production of Iron Oxide Nano Particles from Different Precursors Abstract— We produced monodisperse iron oxide nano particles between 6-21 nm from iron acetyl acetonate, iron oxide hydroxide, iron oleate and iron acetate procursors at different experimental conditions. It was observed that around 15 nm particles produced from iron oxide hydroxide and iron oleate precursors were more reliable, simple and economic. Iron nano particles have a great interest because of magnetic, electric and catalytic properties [1-7]. Particulaly, in Fischer-Tropsch synthesis (FTS), which produces sulfur and aromatic free fuel, liquid hydrocarbons can be produced from synthesis gas (CO + H 2 ) over iron catalysis. Iron nano particles also play an important role in the carbon nanotube production. In these proseses, iron catalysis are prefered because of catalytic activity and economy [8-9]. In this work, we explored the production of monodisperse iron nanoparticles between 6-21 nm from four different iron precursors by a thermal decomposition process. The precursors used were iron acetyl acetonate (Fe(acac) 3 ), iron oxide hydroxide (FeOOH), iron oleate and iron acetate (Fe(ac) 2 ). In the experiments, some experimental parameters were changed in order to tune the particle diameter of the iron oxide nanoparticles. The tables of experimental condititions as follows Table 1. Experimental conditions for Fe(acac) 3 [1-4] Ex. No 1 2 3 4 Fe(acac) Precur. 3 Fe(acac) 3 Fe(acac) 3 Fe(acac) 3 3mmol 2mmol 2mmol 2mmol O.Acid O.Acid O.Acid O.Acid Surf.-1 9 mmol 2mmol 2mmol 2mmol O. Amine O. Amine O. Amine O. Amine Surf.-2 Red.A. 9 mmol 1,2 Hex. Diol 15 mmol 2mmol 1,2 Hex. Diol 10 mmol 2mmol 1,2 Hex. Diol 10 mmol 2mmol 1,2 Hex. Diol 10 mmol Solv. 1-oct. 1-oct. 1-oct. 1-oct. 20 mL 20 mL 20 mL 20 mL Temp. 315 o C 315 o C 315 o C 315 o C Part. S. 6 nm 8 nm 10 nm 14 nm At 100 o C, 30 min., at At 100 o C, 30 min,. at At 100 o C, 30 min., at Explan. At 200 o 200 o C, 1 h. 200 o C, 1 h. 200 o C, 2 h. C, and at 315 and at 315 and at 315 2 hour and at 315 o C, 1 h. C, 1 h. C, 1 h. C, 1 waiting, waiting waiting hour seed were seed were seed were waiting taken from taken from taken from 1st. experiment 2nd. experiment 3 th. experiment (Precur.: precursor, surf.; surfactant, red.a; reducing agent, solv.; solvent, part. s.; particle size, explan.; explanation, O.; oleic, Hex. Diol.: hexadecenediol, oct: octadecene) Table 2. Experimental conditions for FeOOH [5] Ex. No 1 2 Precur. FeOOH, 6mmol FeOOH, 6mmol Surf.-1 O.Acid, 18 mmol O.Acid, 36 mmol Solv. 1-oct., 20 mL 1-oct., 24 mL Temp. 315 o C 315 o C Part. S. 10 nm 17 nm Explan. At 315 o C, 1.5 h. waiting At 315 o C, 1.5 h. waiting Table 3. Experimental conditions for Fe oleate [6] Ex. No 1 2 Precur. Fe Oleate, 4 mmol Fe Oleate, 4mmol Surf.-1 O.Acid, 2 mmol O.Acid, 2 mmol Solv. 1-oct., 29 mL 1-oct., 29 mL Temp. 315 o C 315 o C Part. S. 12.5 nm 15 nm Explan. At.320 o C, 30 min waitinig At.220 o C, 30 min and at.320 o C, 30 min waitinig Table 4. Experimental conditions for Fe(ac) 2 [7] Ex. No 1 2 Precur. Fe(Ac) 2 ,8mmol Fe(Ac) 2 ,6mmol Surf.-1 O.Acid, 3.6 mmol O.Acid, 10 mmol Solv. TOA, 20 mL TOA, 15 mL Temp. 260 o C 260 o C Part. S. 21.5 nm 14 nm Explan. At 220 o C, 20 min. and at 260 o C, 40 min. waiting At 260 o C, 1.5 h. waiting (TOA.; tri octyl amine) Fe(acac) 3 precursor 14 nm FeOOH precursor 17 nm Fe oleate precursor 15 nm Fe(ac) 2 precursor 14 nm Figure 1. TEM pictures of some iron oxides produced from different precursors. In summary, iron oxide nano particles having 14 nm. diameter were produced at the end of the four stage process by iron acetylacetonate precursor. When iron oxide hydroxide precursor were used, increasing the surfactant amount as two times increased the particle size from 10 nm to 17 nm. In the case of iron oleate precursor, when waited at 220 o C for 30 min. during the reaction, the particle size increased from 12.5 to 15 nm. in a one stage reaction. The second experimental conditions of iron acetate in Table 4. gave more monodisperde nano particles than first experimental condition. Our results showed that iron oxides produced from iron oxide hydroxide and iron oleate precursors were more reliable, simple and economic. I acknowledge support from the Scientific and Technological Research Council of Turkey (TUBITAK) through grant no. BIDEB-2219. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 257
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