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

2. Interests of study High performance catalysts 1 (hydrogenation, oxidation, selectivity, etc.) High performance catalysts 1 (hydrogenation, oxidation, selectivity, etc.) Advanced materials (electronic, optic, magnetic, etc., properties) 2 Advanced materials (electronic, optic, magnetic, etc., properties) 2 Size related properties investigation Size related properties investigation

3. Salt reduction Reduction of metal salt in solution 3 Reduction of metal salt in solution 3 Reducing agent added in situ Reducing agent added in situ Easily oxidized solvent, e.g. alcohol, can act as reducing agent 4 Easily oxidized solvent, e.g. alcohol, can act as reducing agent 4 Stabilizing agents Stabilizing agents

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

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

6. PVP-protected Pd nanoparticles H 2 PdCl 4 aqueous solution (2.0 mM) preparation 0.6 mmol of PdCl 2 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 H 2 PdCl 4 aqueous solution (30 µmol of Pd) x mL of water, y mL of alcohol (x + y ) 35 mL Poly(VinylPyrrolidone) 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, (PVP-Pd particles dark colour, disappearance of [PdCl 4 ] 2- yellow) Selected Area Electron Diffraction (ED) Transmission Electron Microscopy (TEM) PVP-Pd nanoparticles TEM characterization and mean diameter (Teranishi and M. Miyake 5 )

10. Results Synthetic conditionMean diameter Å PVP/Pd = 10 [ethanol] = 70 vol % PVP/Pd = 1.0, [ethanol] = 20 vol % PVP/Pd = 10 [ethanol] = 20 vol % PVP/Pd =10 [ethanol] = 40 vol % 48.9 33.6 24.4 22.2 Influence of the concentration of alcohol as a reducing agent Influence of the amount of stabilizing agent 20-40 vol % of alcohol with excess of PVP to Pd  Smallest particles

11. Achievements PVP prevent particles from aggregating PVP prevent particles from aggregating Controlled nanoparticles diameter from 22 to 48 Controlled nanoparticles diameter from 22 to 48 Å Narrow size distribution for smaller particles 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 ?