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Transition Metal Nanoparticles Synthesis: Salt Reduction

Transition Metal Nanoparticles Synthesis: Salt Reduction

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Transition Metal Nanoparticles Synthesis: Salt Reduction

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  1. Transition Metal Nanoparticles Synthesis:Salt Reduction CHEM *7530/750 Winter 2006 Olivier Nguon

  2. Interests of study • High performance catalysts1 (hydrogenation, oxidation, selectivity, etc.) • Advanced materials (electronic, optic, magnetic, etc., properties)2 • Size related properties investigation

  3. Salt reduction • Reduction of metal salt in solution3 • Reducing agent added in situ • Easily oxidized solvent, e.g. alcohol, can act as reducing agent4 • Stabilizing agents

  4. Stabilization of nanoparticles in liquids Agglomeration • Particles attracted by Van der Waals forces • Coagulation Aggregation of particles due to Van der Waals forces

  5. Stabilization of nanoparticles in liquids Solutions • Electrostatic stabilization • Steric stabilization Steric stabilization using polymers

  6. PVP-protected Pd nanoparticles H2PdCl4 aqueous solution (2.0 mM) preparation • 0.6 mmol of PdCl2 • 6.0 mL of 0.2 M HCl, • 294 mL of distilled water. ____________________________________________________________________ 5. T. Teranishi and M. Miyake, Chem. Mater. 1998, 10, 594-600

  7. PVP-protected Pd nanoparticles • A mixture of 15 mL H2PdCl4 aqueous solution (30 µmol of Pd) • x mL of water, • y mL of alcohol • (x + y ) 35 mL • Poly(VinylPyrrolidone) PVP (40 000 g/mol) was refluxed

  8. size and size distribution of Pd nanoparticles control • The amount of PVP from 0.333 mg to 133 mg • The concentration of alcohol in the solvent was changed from 10 to 70 vol %

  9. Measurements • UV-vis spectroscopy (PVP-Pd particles dark colour, disappearance of [PdCl4]2- yellow) • Selected Area Electron Diffraction (ED) • Transmission Electron Microscopy (TEM) PVP-Pd nanoparticles TEM characterization and mean diameter (Teranishi and M. Miyake5)

  10. Results • Influence of the concentration of alcohol as a reducing agent • Influence of the amount of stabilizing agent

  11. Achievements • PVP prevent particles from aggregating • Controlled nanoparticles diameter from 22 to 48 Å • Narrow size distribution for smaller particles (σ= 4.23 Å)

  12. Limits • Particle size appeared to have a lower limit determined by the kind of alcohol. (methanol > ethanol > 1-propanol) • Larger particles have a broader size distribution

  13. References 1. Lewis, L. N. Chem. Rev. (Washington, D.C.) 1993, 93, 2693. 2. Colvin, V. L.; Schlamp, M. C.; Alivisatos, A. P. Nature 1994, 370, 354. 3. Nanoparticles, Gunter Schmidt Edition, Wiley-VCH, 2004. 4. Hirai, H.; Toshima, N. Tailored Metal Catalysts; Iwasawa, Y., Ed.; D. Reidel: Dordrecht, 1986; pp 87-140. 5. Teranishi and M. Miyake, Chem. Mater. 1998, 10, 594-600

  14. Thank you !!! Any questions ?