🗊Презентация The way to prepare gold clusters - Every atom makes a difference

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Слайд 1





The way to prepare gold clusters
 -Every atom makes a difference
Naoaki Shinjo
Department of Chemistry, School of Science
The University of Tokyo
Описание слайда:
The way to prepare gold clusters -Every atom makes a difference Naoaki Shinjo Department of Chemistry, School of Science The University of Tokyo

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The strategy for preparing metal clusters
Bottom-up preparation
Metal ions – electrostatic repulsion
          ↓ reduction
Neutral metal atoms
  ↓ aggregation
Metal clusters
Problems:
Continuous aggregation   
Difficulty in size control   
Описание слайда:
The strategy for preparing metal clusters Bottom-up preparation Metal ions – electrostatic repulsion ↓ reduction Neutral metal atoms   ↓ aggregation Metal clusters Problems: Continuous aggregation    Difficulty in size control   

Слайд 3





“Magic numbers” for bare gold clusters
Описание слайда:
“Magic numbers” for bare gold clusters

Слайд 4





Protection of metal clusters by ligands
I. Protection by phosphine ligands 
Dative ligands  
Описание слайда:
Protection of metal clusters by ligands I. Protection by phosphine ligands Dative ligands  

Слайд 5





Protection of metal clusters by ligands
I. Protection by phosphine ligands 
Chiral clusters with BINAP  
Описание слайда:
Protection of metal clusters by ligands I. Protection by phosphine ligands Chiral clusters with BINAP  

Слайд 6





Protection of metal clusters by ligands
II. Protection by thiolate ligands
– high affinity between Au and S
“Brust-Schiffrin Method” 
(B) Ligand exchange of phosphine-protected clusters
     
Thiolation of  polymer-stabilized clusters
Описание слайда:
Protection of metal clusters by ligands II. Protection by thiolate ligands – high affinity between Au and S “Brust-Schiffrin Method” (B) Ligand exchange of phosphine-protected clusters Thiolation of polymer-stabilized clusters

Слайд 7





Protection of metal clusters by ligands
II. Protection by thiolate ligands
“Brust-Schiffrin Method” 
(i) Phase transfer of a gold salt (reaction is not balanced)
HAuCl4 (aq) + TOABr (tol) → [AuCl4-xBrx]TOA (tol) + HCl (aq)
(ii) Reduction of Au (III) to Au(I)
[AuCl4-xBrx]TOA + 3HSR → Au:SR + RSSR
(ii) Reduction of Au (I) to Au(0) → Aggregation
Au:SR + NaBH4 (aq, excess) → Aun(SR)m
Competition between thiolate protection and aggregation
⇒ Kinetic control of size distribution
Описание слайда:
Protection of metal clusters by ligands II. Protection by thiolate ligands “Brust-Schiffrin Method” (i) Phase transfer of a gold salt (reaction is not balanced) HAuCl4 (aq) + TOABr (tol) → [AuCl4-xBrx]TOA (tol) + HCl (aq) (ii) Reduction of Au (III) to Au(I) [AuCl4-xBrx]TOA + 3HSR → Au:SR + RSSR (ii) Reduction of Au (I) to Au(0) → Aggregation Au:SR + NaBH4 (aq, excess) → Aun(SR)m Competition between thiolate protection and aggregation ⇒ Kinetic control of size distribution

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Protection of metal clusters by ligands
II. Protection by thiolate ligands
(B) Ligand exchange of phosphine-stabilized clusters
     e.g. [Au11(PPh3)8X2]+, [Au11(BINAP)4X2]+
Thiolation of  polymer-stabilized clusters
     e.g. Au:PVP
Dependent on the stability of parent clusters
⇒ Thermodynamic control of size distribution
Описание слайда:
Protection of metal clusters by ligands II. Protection by thiolate ligands (B) Ligand exchange of phosphine-stabilized clusters e.g. [Au11(PPh3)8X2]+, [Au11(BINAP)4X2]+ Thiolation of polymer-stabilized clusters e.g. Au:PVP Dependent on the stability of parent clusters ⇒ Thermodynamic control of size distribution

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Fractionation of gold clusters 
Atomic monodispersity is difficult to achieve
↓
Fractionation
(A) Polyacrylamide gel electrophoresis (PAGE)
(B) Gel permeation chromatography (GPC)
(C) Size-selective etching
Описание слайда:
Fractionation of gold clusters Atomic monodispersity is difficult to achieve ↓ Fractionation (A) Polyacrylamide gel electrophoresis (PAGE) (B) Gel permeation chromatography (GPC) (C) Size-selective etching

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Fractionation by PAGE
Fractionation by PAGE
– suitable for hydrophilic, charged clusters
Описание слайда:
Fractionation by PAGE Fractionation by PAGE – suitable for hydrophilic, charged clusters

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Fractionation by PAGE
Fractionation by PAGE
      Au:SG, Au:S(h-G) 
          GSH: glutathione 
      
      h-GSH: homo-glutathione
Описание слайда:
Fractionation by PAGE Fractionation by PAGE Au:SG, Au:S(h-G) GSH: glutathione h-GSH: homo-glutathione

Слайд 12





Fractionation by PAGE
Fractionation by PAGE
Описание слайда:
Fractionation by PAGE Fractionation by PAGE

Слайд 13





(B) Fractionation by GPC
(B) Fractionation by GPC
– suitable for hydrophobic clusters
Описание слайда:
(B) Fractionation by GPC (B) Fractionation by GPC – suitable for hydrophobic clusters

Слайд 14





(B) Fractionation by GPC
(B) Fractionation by GPC
Описание слайда:
(B) Fractionation by GPC (B) Fractionation by GPC

Слайд 15





Fractionation of gold clusters 
(C) Size-selective etching
Описание слайда:
Fractionation of gold clusters (C) Size-selective etching

Слайд 16





Fractionation of gold clusters 
Stability of Au25(SG)18
Описание слайда:
Fractionation of gold clusters Stability of Au25(SG)18

Слайд 17





The latest results
Bond stiffness of Aun(SR)m clusters
Описание слайда:
The latest results Bond stiffness of Aun(SR)m clusters

Слайд 18





The latest results
Bond stiffness of Aun(SR)m clusters
Описание слайда:
The latest results Bond stiffness of Aun(SR)m clusters

Слайд 19





The latest results
Bond stiffness of Aun(SR)m clusters
Описание слайда:
The latest results Bond stiffness of Aun(SR)m clusters

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Conclusion
Bottom-up preparation of gold clusters can be achieved by protection with ligands.
Monodisperse clusters are obtained by the fractionation (PAGE, GPC, and size-selective etching).
Magic-numbered clusters are thermodynamically stable and forms dominantly. The stability is explained by their electronic or geometric structures.
Описание слайда:
Conclusion Bottom-up preparation of gold clusters can be achieved by protection with ligands. Monodisperse clusters are obtained by the fractionation (PAGE, GPC, and size-selective etching). Magic-numbered clusters are thermodynamically stable and forms dominantly. The stability is explained by their electronic or geometric structures.

Слайд 21





Thank you for listening!!
Описание слайда:
Thank you for listening!!



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