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№1 слайд![The way to prepare gold](/documents_6/9237db5ed1c12ff36e514a66819e1130/img0.jpg)
Содержание слайда: The way to prepare gold clusters
-Every atom makes a difference
Naoaki Shinjo
Department of Chemistry, School of Science
The University of Tokyo
№2 слайд![The strategy for preparing](/documents_6/9237db5ed1c12ff36e514a66819e1130/img1.jpg)
Содержание 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
№3 слайд![Magic numbers for bare gold](/documents_6/9237db5ed1c12ff36e514a66819e1130/img2.jpg)
Содержание слайда: “Magic numbers” for bare gold clusters
№4 слайд![Protection of metal clusters](/documents_6/9237db5ed1c12ff36e514a66819e1130/img3.jpg)
Содержание слайда: Protection of metal clusters by ligands
I. Protection by phosphine ligands
Dative ligands
№5 слайд![Protection of metal clusters](/documents_6/9237db5ed1c12ff36e514a66819e1130/img4.jpg)
Содержание слайда: Protection of metal clusters by ligands
I. Protection by phosphine ligands
Chiral clusters with BINAP
№6 слайд![Protection of metal clusters](/documents_6/9237db5ed1c12ff36e514a66819e1130/img5.jpg)
Содержание 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
№7 слайд![Protection of metal clusters](/documents_6/9237db5ed1c12ff36e514a66819e1130/img6.jpg)
Содержание 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
№8 слайд![Protection of metal clusters](/documents_6/9237db5ed1c12ff36e514a66819e1130/img7.jpg)
Содержание 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
№9 слайд![Fractionation of gold](/documents_6/9237db5ed1c12ff36e514a66819e1130/img8.jpg)
Содержание 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
№10 слайд![Fractionation by PAGE](/documents_6/9237db5ed1c12ff36e514a66819e1130/img9.jpg)
Содержание слайда: Fractionation by PAGE
Fractionation by PAGE
– suitable for hydrophilic, charged clusters
№11 слайд![Fractionation by PAGE](/documents_6/9237db5ed1c12ff36e514a66819e1130/img10.jpg)
Содержание слайда: Fractionation by PAGE
Fractionation by PAGE
Au:SG, Au:S(h-G)
GSH: glutathione
h-GSH: homo-glutathione
№12 слайд![Fractionation by PAGE](/documents_6/9237db5ed1c12ff36e514a66819e1130/img11.jpg)
Содержание слайда: Fractionation by PAGE
Fractionation by PAGE
№13 слайд![B Fractionation by GPC B](/documents_6/9237db5ed1c12ff36e514a66819e1130/img12.jpg)
Содержание слайда: (B) Fractionation by GPC
(B) Fractionation by GPC
– suitable for hydrophobic clusters
№14 слайд![B Fractionation by GPC B](/documents_6/9237db5ed1c12ff36e514a66819e1130/img13.jpg)
Содержание слайда: (B) Fractionation by GPC
(B) Fractionation by GPC
№15 слайд![Fractionation of gold](/documents_6/9237db5ed1c12ff36e514a66819e1130/img14.jpg)
Содержание слайда: Fractionation of gold clusters
(C) Size-selective etching
№16 слайд![Fractionation of gold](/documents_6/9237db5ed1c12ff36e514a66819e1130/img15.jpg)
Содержание слайда: Fractionation of gold clusters
Stability of Au25(SG)18
№17 слайд![The latest results Bond](/documents_6/9237db5ed1c12ff36e514a66819e1130/img16.jpg)
Содержание слайда: The latest results
Bond stiffness of Aun(SR)m clusters
№18 слайд![The latest results Bond](/documents_6/9237db5ed1c12ff36e514a66819e1130/img17.jpg)
Содержание слайда: The latest results
Bond stiffness of Aun(SR)m clusters
№19 слайд![The latest results Bond](/documents_6/9237db5ed1c12ff36e514a66819e1130/img18.jpg)
Содержание слайда: The latest results
Bond stiffness of Aun(SR)m clusters
№20 слайд![Conclusion Bottom-up](/documents_6/9237db5ed1c12ff36e514a66819e1130/img19.jpg)
Содержание 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.
№21 слайд![Thank you for listening!!](/documents_6/9237db5ed1c12ff36e514a66819e1130/img20.jpg)
Содержание слайда: Thank you for listening!!