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LOCAL, GLOBAL AND ELECTRONIC STRUCTURE OF NANOSTRUCTURED SYSTEMS

National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca, Romania. LOCAL, GLOBAL AND ELECTRONIC STRUCTURE OF NANOSTRUCTURED SYSTEMS. N. Aldea 1 , S. Pintea 1 , V. Rednic 1 , P. Marginean 1 , R. Turcu 1 , S. Gergely 1 , M. Neumann 2 , Y. Xie 3 , F. Matei 4

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LOCAL, GLOBAL AND ELECTRONIC STRUCTURE OF NANOSTRUCTURED SYSTEMS

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  1. National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca, Romania LOCAL, GLOBAL AND ELECTRONIC STRUCTURE OF NANOSTRUCTUREDSYSTEMS N. Aldea1, S. Pintea1, V. Rednic1, P. Marginean1, R. Turcu1, S. Gergely1, M. Neumann2, Y. Xie3, F. Matei4 1 National Institute for R&D of Isotopic and Molecular Technologies, Cluj - Napoca, Romania 2 University of Osnabrück, Fachberiech Physik, Osnabruck, Germany 3 Beijing Synchrotron Radiation Facilities of Beijing, National Laboratory, P. R. China 4 University of Agriculture Sciences and Veterinary Medicine, Math. Department, Cluj-Napoca, Romania The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  2. Outlook Some physical and chemical properties of nanostructured materials (supported Au and Ni catalysts, Fe3O4polypyrrole core-shell composites) Theoretical background of EXAFS, XRD and XPS methods Experimental, data analysis, results and discussion Conclusions The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  3. A. Physical and chemical properties • Supported metal catalysts (SMC) arespecial materials used in complete or partial oxidation, reduction or hydrogenation reactions that change the reaction speed without changing the chemical equilibrium. • Fe3O4nanocompositesbased on polypyrrole and magnetites are biocompatible and offer great promise applications in biotechnology. A1. Why are we interested to determine crystalline and electronic nanostructure ? strong correlation the global (XRD), local (XAS) and electronic structure (XPS) Catalytic activity A2. Crystallite size (global structure) determination methods: • Chemisorption of the hydrogen • TEM • Magnetic measurements method - based on Longevin’s theory • Powder X-ray diffraction - a new package program: XRSIZE The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  4. Crystallite domain Grain size Adsorbed hydrogen atoms A. Physical and chemical properties A3.Grain size HRTEM micrograph of Au/TiO2 chemosorption of the hydrogen Masatake Haruta, "Catalyst of gold nanoparticles deposited on metal oxides" Cattech 6 (2002) 102 P. Marginean and A. Olaru, Appl. Catalysis A: General 140 (1996) 59 The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  5. A. Physical and chemical properties A4. The activity of supported gold catalysts R. Grisel, Kees-Jan Weststrate, Andrea Gluhoi, B.E.Nieuwenhuys, "Catalysis by Gold Nanoparticles", Gold Bulletin 35/2 (2002) 45 Synergistic and particle size effects for reactions: a) conversion of propene2C3H6 + 9O2 → 6CO2 + 6H2O b) CO oxidation2CO + O2 → 2CO2 c) Temperature neededfor 95% CO conversion versus the average gold particle size of Au/Al2O3 calcined at 300 °C (▲), Au/Al2O3 calcined at 600 °C (■ ), Au/Al2O3 calcined at 900 °C (♦)and Au/MOx/Al2O3 (●) catalysts. The three Au/Al2O3 catalysts have been calcined at 300, 400 and 600 °C in order to change the average Au particle size The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  6. B. Theoretical background B1.Theoretical outline of local structure of the metal particle nanosize based on EXAFS method B 1.1 The EXAFS function χ(k) is defined in terms of the atomic absorption coefficient B 1.2 The theoretical EXAFS signal is defined by the relation Total amplitude function: B 1.3 The single shell contribution may be isolated by Fourier transform technique B 1.4 The inverse Fourier transform of the radial structure function is obtained for any coordination shell with: The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  7. · Diffraction line broadening analysis - Scherrer method; · Fourier transform or analysis using Generalized Fermi Function (GFF) for X-ray Line Profiles (XRLP) approximation B. Theoretical background B2. Particle size determination from X-ray diffraction method By X-ray line diffraction profile (XRLP) analysis one can obtain crystallite size, microstrain and stacking fault probability. Methods For non-overlapped lines • N. Aldea, Andreea Gluhoi, P. Marginean, C. Cosma, Xie Yaning, Extended X-ray absorption fine structure and X-ray diffraction studies on supported nickel catalysts, Spectrochimica Acta B 55, 997 (2000). • N. Aldea, Andreea Gluhoi, P. Marginean, C. Cosma, Xie Yaning, Hu Tiandou, Whongua Wu and Baozhong Dong, Investigation of supported nickel catalysts by X-ray absorbtion spectrometry and X-ray diffraction using synchrotron radiation, Spectrochimica Acta B 57, 1453 (2002). • N. Aldea, B. Barz, S. Pintea, F. Matei,Theoretical approach regarding nanometrology of the metal nanoclusters used in heterogeneous catalysis by powderX-ray diffraction method, J. Optoelectron. Adv. Mat 9(10) (2007) 3293. The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  8. F(L)=Fs(L)F(L) Û s F - depends on particle size and stacking faults probability - depends on microstrains Two simultaneous events. Fourier transform method ε F Convolution equation: h(s) – experimental spectrum g(s) - instrumental function f(s) - true sample spectrum Fredholm integral equation of the first kind Ill-posed problem. B. Theoretical background B3. Theoretical outline of metal particle nanosize based on single x-ray line profile analysis B3.1 General aspects based on convolution equation: B3.2General relation of the true sample function  erfc(x)=1-erf(x). The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  9. C. Experimental, data analysis, results and discussions C1. Investigated systems. Preparation methods C1.1 Supported gold catalysts • Supported gold catalysts were prepared by homogeneous deposition-precipitation with urea on support of MOx/Al2O3 (M: Cu, Ce, Mg, Li in different combinations). • The gold precursor was HAuCl4·3H2O, Aldrich, 99.999% purity. • The theoretical gold content for the catalysts was 5 wt %. • The catalysts were calcined at 3000 C before the measurements 0 - Au foil 1 - Au/LaOx/Al2O3 2 - Au/ZnO/MgO/Al2O3 3 - Au/CuO/Al2O3 4 - Au/CeOx/Al2O3 5 - Au/ZnO/Al2O3 6 - Au/TiO2 7 - Au/MnOx/Al2O3 8 - Au/Al2O3 9 - Au/CeOx/ ZrOx/ Al2O3 10 - Au/Li2O/CeOx/Al2O3 11 - Au/Rb2O/CeOx/Al2O3 The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  10. C. Experimental, data analysis, results and discussions C1.2 Supported nickel catalysts • The Ni/Cr2O3 and Ni/Al2O3 catalysts were prepared by coprecipitation of the mixture of nickel nitrate and chromium nitrate, respectively, aluminum nitrate with a solution of sodium carbonate/hydroxide. • After precipitation we obtained: NiCO3.2Ni(OH)2.4H2O, Al hydroxide and Cr hydroxide, respectively • In order to eliminate the sodium ions the precipitate was thoroughly washed with double distilled water. Then the precipitate was dried at 105°C in stove and calcined in nitrogen flow at 340°C and reduced in flowing hydrogen. • The thermal treatments of the catalysts have been done in hydrogen flow at different temperatures for 3 hours. Ni/Al2O3 Ni/Cr2O3 Ni85Al15 at % Termal treatement at: 11 - 3500C 12 - 5500C 13 - 7500C 14 - 8500C 15 - 10500C Ni85Cr15 at % Termal treatement at: 1 - 3500C 2 - 4200C 3 - 6500C 4 - 8500C 5 - 9500C Ni70Cr30 at % Termal treatement at: 6 - 3500C 7 - 6500C 8 - 7500C 9 - 9000C 10- 9500C Ni70Al30 at % Termal treatement at: 16 - 9500C Ni60Al40 at % Termal treatement at: 17 - 10500C The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  11. C. Experimental, data analysis, results and discussions C1.3Fe3O4polypyrrole core-shell composites The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  12. monochromater ion chamber SR BEAMLINE t slit IC1 IC0 slit slit sample I0 I encoder Stepped motors data acquisition counter drivers interface I=I0e-t GPIB bus computer C. Experimental, data analysis, results and discussions C2. XAS measurements C2.1XAS set up on synchrotron radiation for transmission measurements Block diagram of the monochromator control and XAS data acquisition The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  13. C. Experimental, data analysis, results and discussions C2.2Results and discussions C2.2.1SupportedGold catalysts BSRF - Beijing Synchrotron Radiation Facilities 4W1B beamlines, 30-50 mA, 2.2 GeV, room temperature, ΔE=1-2 eV at E=10 KeV • XAS spectroscopy • LIII gold edge, fluorescence technique, X-ray energy of incident flux between 11582 - 12806 eV 0 - Au foil 1 - Au/LaOx/Al2O3 2 - Au/ZnO/MgO/Al2O3 3 - Au/CuO/Al2O3 4 - Au/CeOx/Al2O3 5 - Au/ZnO/Al2O3 6 - Au/TiO2 7 - Au/MnOx/Al2O3 8 - Au/Al2O3 9 - Au/CeOx/ ZrOx/ Al2O3 10 - Au/Li2O/CeOx/Al2O3 11 - Au/Rb2O/CeOx/Al2O3 ── Au(OH)3 EXAFS signals The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  14. C. Experimental, data analysis, results and discussions Numerical results N1 = 12 atoms, R1 = 0.287 nm N2 = 6 atoms, R2 = 0.407 nm N3 = 24 atoms,R3 = 0.498 nm N4 = 12 atoms,R4 = 0.575 nm Standard sample: The local structural parameters of the investigated samples for the first coordination shell The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  15. C. Experimental, data analysis, results and discussions XANES Analysis • N. Aldea, C. Tiusan, A. Chezan, "Full multiple scattering approximation to K-XANES of supported metal catalysts", Physica B, 208 & 209 (1995) 691. • K edge for Ni, Cu, Fe; • K edge for Cl (NaCl), F (NaF), K (KCl), K (KF), Ti (TiO), Ti (TiC). Z = 79, Au: Discrete transitions 6s LIII 2p3/2 → 6d3/2 6d5/2 The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  16. C. Experimental, data analysis, results and discussions Transitions probability • ℒ , ℒ(E)dE = 1, FWHM = Γ, -life time XANES signals The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  17. C. Experimental, data analysis, results and discussions The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  18. C. Experimental, data analysis, results and discussions Transition probability parameters (LIII edge) M. LAZAR, V. ALMASAN, S.PINTEA, B. BARZ, C. DUCU, V. MALINOVSCHI, X. YANING, N. ALDEA Preparation and structural characterization by XRD and XAS of the supported gold catalysts JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10 (9), 2244 (2008) N. Aldea, V. Rednic, S. Pintea, P. Marginean, B. Barz, A. Gluhoi, B. E. Nieuwenhuys, M. Neuman, X. Yaning, F. Matei Local, global and electronic structure of supported gold nanoclustersdetermined by EXAFS, XRD and XPS sent for publication Superlattices and Microstructures, Ref: SM08-141, 2008 The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  19. C. Experimental, data analysis, results and discussions C2.2.2 Supported Ni catalysts XAS signals The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  20. C. Experimental, data analysis, results and discussions The first coordination shell parameters S. Pintea, V. Rednic, P. Marginean, X. Yaning, H. Tiandou, Z. Wu, M. Neumann and N. Aldea Crystalline and electronic structure investigated by XRD, XAS and XPS methods of Ni nanoclusters supported on Al2O3 and Cr2O3 sent for publication Superlattices and Microstructures, Ref: SM 08-136, 2008 The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  21. Fe3O4 standard sample C. Experimental, data analysis, results and discussions C2.2.3.Fe3O4polypyrrole core-shell composites Fe K edge XANES (A) quadrupole transition 1s-3d, l=o, ±1, ±2 (B) dipole transition 3d-4d mixing Fe electrons, l=o, ±1 (C) d-p mixing Fe and O electrons (D) clusters size of metal oxide Full multiple scattering theory applied to transition metals and AB compounds N. Aldea, C. Tiusan, A. Chezan, Physica B, 208-209 (1995),691 Threshold energy EB- maximum value of the first derivative The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  22. Fe3O4 Normalized XANES & EXAFS -0.2 Fe3O4 as standard sample "fe3o4s.dat" -0.4 background -0.6 -0.8 -1 -1.2 miux(energy) -1.4 -1.6 -1.8 -2 -2.2 -2.4 6800 7000 7200 7400 7600 7800 8000 8200 X-ray energy [eV] Fe3O4 χ signal of standard sample Fe3O4, µ0, µ signals Fe3O4 - Normalized EXAFS & XANES, Miux-0, Miux 1 Normalized EXAFS signal Fe3O4 XANES Fe3O4 miux Fe3O4 miux-zero 0.8 0.6 miux(energy) 0.4 0.2 0 6800 7000 7200 7400 7600 7800 8000 8200 X-ray energy [eV] C. Experimental, data analysis, results and discussions XAS signals The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  23. C. Experimental, data analysis, results and discussions EXAFS results Radial structure function (RSF) Inverse Fourier transform of the RSF • San-Miguel, Physica B 208 & 209,177 (1995) (LURE, ESRF) • CDXAS computer package programs Where are the first & second coordination shells? They are overlapped k r What we have to do? Good bye FFT !!! Modified Filon algorithm M. Abramowich and A. Stegun, Handbook Math. Func., EXAFS 51-65 (1996) . N. Aldea, E. Indrea, Comput. Phys. Commun. 60 (1990) 155. N. Aldea, R. Zapotinschi, PC 94 Lugano, Switzerland, (1994) The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  24. C. Experimental, data analysis, results and discussions Fe3+ tetrahedral structure Fe-O R1=1.89 Å, N1=4 Fe2+/ Fe3+ octahedral structure Fe-O R2=2.09 Å, N2=6 R = R2-R1= 0.2 Å R[H] = 0.52147 Å N. Aldea, R. Turcu, A. Nan, I. Craciunescu, O. Pana, X. Yaning, Z. Wu, D. Bica, L. Vekas, F. Matei Investigation of nanostructured Fe3O4polypyrrole core-shell composites by X-ray absorbtion spectroscopy and X-ray diffraction using synchrotron radiation accepted for publicationJournal of Nanoparticle Research, DOI: 10.1007/s11051-008-9536-3 N. Aldea, S. Pintea, V. Rednic, F. Matei and X. Yaning Comparative study of EXAFS spectra for closed-shell systems sent for publicationJOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  25. C. Experimental, data analysis, results and discussions Radial distribution function The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  26. C. Experimental, data analysis, results and discussions Local structure parameters The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  27. SAMPLE DETECTOR BEPC IC AL window 6 - CIRCLES DIFRACTOMETER SLI SLIT SR BEAMLINE BE window MIRROR MONOCHROMATOR MOTION TABLE CAMAC CRATE HV for LC CONTROLLER HV for Na I SMC SCA Time gen. Ampl. COUNTER INTERFACE RATEMETER DISPLAY DRIVER FORTAB (6) GATED CLOCK DRIVER FOR DIF (6) I/O REGISTER DRIVER FOR MONO (1) SMC I/V Ampl. V/F COUNTER PRINTER COMPUTER PDP11/53 TERMINAL C. Experimental, data analysis, results and discussions C3. XRD measurements C3.1XRD setup SCHEMATIC DIFFRACTION STATION AT BSRL -2 montage, ionic chamber before sample The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  28. (200) Au foil Standard sample Relative Intensity (111) (311) (220) 35 40 45 50 55 60 65 70 75 80 85 o q (2 ) C. Experimental, data analysis, results and discussions C3.2Results and discussions C3.2.1 Supported Gold catalysts Au Space Group 225, a=b=c= 0.40720 nm Instrumental correction: Au - foil RIGAKU setup with rotating anode λ = 0.15406 nm The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  29. Sample Au/SiO2 (1.1), Line (111) 1.1 Experimental General approximation 1 Background correction by polynomial approximation Cubic App. Parabolic App. 0.9 3000 f(x) 0.8 experimental fond 0.7 2500 gff1(x) gff2(x) 0.6 Fourier Transform of true sample gff3(x) 0.5 2000 0.4 Relative Intensity 0.3 1500 0.2 1000 0.1 0 50 100 150 200 250 300 350 400 500 L[Å] 0 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 2*sin()/ λ Experimental Experimental General approximation General approximation Cubic App. Cubic App. Parabolic App. Parabolic App. Sample Au/Al2O3 (3.1), Line (311) Sample Au/SiO2 IMP 3, Line (220) 1 1 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 Fourier Transform of true sample 0.5 Fourier Transform of true sample 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 20 40 60 80 100 120 140 0 10 20 30 40 50 60 L[Å] L[Å] C. Experimental, data analysis, results and discussions Data analysis and Fourier Transform for XRLP by Generalised Fermi Function (GFF) distribution The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  30. C. Experimental, data analysis, results and discussions Global structural parameters of the investigates samples The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  31. C. Experimental, data analysis, results and discussions C3.2.2Supported Ni catalysts XRD Paterns measured on syncrotron radiation The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  32. C. Experimental, data analysis, results and discussions Global structural parameters of the investigates samples The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  33. C. Experimental, data analysis, results and discussions C3.2.3Fe3O4polypyrrole core-shell composites Nanoparticles Fe3O4 polypyrrole core-shell composites Silicon powder for instrumental correction The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  34. C. Experimental, data analysis, results and discussions Global structural parameters of the investigates samples The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  35. C. Experimental, data analysis, results and discussions C4. XPS measurements Background correction for XPS profiles was done by Shirley-Tougaard approximation XPS profiles were approximated by Doniach-Sunjic distribution: C4.1Supported Ni catalysts Ni 2p3/2 oxide Ni 2p1/2 oxide Contribution from Cr2O3 and Al2O3 Ni metal is missing satellites Ni 2p3/2 metal Ni 2p core level lines O 1s core level lines The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  36. C. Experimental, data analysis, results and discussions C4.2SupportedGold catalysts • Au(Au2O3)/Li2O/CeO2/Al2O3 Ce 3d Survey Evidence of Au2O3 on the surface! O 1s Au 4f The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  37. C. Experimental, data analysis, results and discussions • Au/ CeO2/Al2O3 Survey O 1s Au 4f metallic state The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  38. D. Conclusions • The investigated catalysts have crystallite average sizes between 1.6 - 6.3 nm for supported Au catalysts, 6.7 – 43.3 nm for supported Ni catalysts and 3.2 – 10.3 nm in case of Fe3O4polypyrrole core-shell composites;1.6 nm is the smallest value of crystallite size determined by XRD method; • The microstrains of lattice can also be correlated with the effective crystallite size in the following ways: the value of the effective crystallite size increases when the microstrainvalue decreases, and reverse; • The small coordination obtained from EXAFS can explain the strong metal-support interaction (SMSI) as well as the active sites occurrence; • By analyzing the Au LIII edge (XANES) we have shown the existence of the electronic transitions without determining or discriminating the percentage between Au+, Au0; • The different values of the FWHM, obtained for each electronic transition, are an evident prove for the SMSI. The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  39. D. Conclusions • The XPS method provided us additional information related to electronic structure and the possible existence of the gold oxide on the surface of the gold nanocrystallites. • Until now in literature we did not find the 1st and 2nd coordination shells evidenced by XAS for Fe3O4 nanoparticles; • Shapes and shift of XANES spectra and diminution of number of atoms from 1st (25 %) and 2nd (10%) from coordination shells of Fe atoms pointed out the existence of electronic interaction between magnetite nanoparticle and surrounding polypyrrole; • The Ni oxide of the precursors is totally reduced, as we can see in XRD patterns only on the surface there is a thin layer of Ni oxide, evidenced from XPS measurements. The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  40. Research Team and collaborators PhD Student Bogdan Barz Dr. Petru Marginean PhD Student Stelian Pintea PhD Student Vasile Rednic Dr. Rodica Turcu Prof. Dr. Manfred Neumann Dr. Florica Matei Dr. Nicolae Aldea The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

  41. Thank you for your attention ! The 14-th National Conference “Progresses in Cryogenics and Isotopes Separation”, 29-31 October 2008, Calimanesti-Caciulata, Valcea, Romania

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