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Dendrimer-mediated hydrothermal synthesis of ultrathin gold nanowires.

Liu H, Cao X, Yang J, Gong XQ, Shi X - Sci Rep (2013)

Bottom Line: The formation of uniform Au NWs was optimized by varying the Au/Ag salt molar ratio, dendrimer stabilizers, and reaction solvent, temperature, and time.A novel growth mechanism involving a synergic facet-dependent deposition/reduction of Ag(I) and oriented migration of Au atoms is proposed based on density functional theory calculations and the experimental results.This work can significantly expand the scope of dendrimers as stabilizers to generate metal NWs in aqueous solution that may be further functionalized for different applications.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China [2] College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, People's Republic of China.

ABSTRACT
We report the use of poly(amidoamine) dendrimers as stabilizers to synthesize ultrathin Au nanowires (NWs) with a diameter of 1.3 nm via a hydrothermal approach. The formation of uniform Au NWs was optimized by varying the Au/Ag salt molar ratio, dendrimer stabilizers, and reaction solvent, temperature, and time. A novel growth mechanism involving a synergic facet-dependent deposition/reduction of Ag(I) and oriented migration of Au atoms is proposed based on density functional theory calculations and the experimental results. This work can significantly expand the scope of dendrimers as stabilizers to generate metal NWs in aqueous solution that may be further functionalized for different applications.

No MeSH data available.


DFT simulated growth mechanism of the formed NWs.Schematic illustration of the Au NW growth process involving adsorption and mergence of Ag atoms.
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f4: DFT simulated growth mechanism of the formed NWs.Schematic illustration of the Au NW growth process involving adsorption and mergence of Ag atoms.

Mentions: To take into consideration of surface defects in the realistic system, we also calculated an Au37Ag particle based on the octahedral Au38 model in which one Ag atom adsorbs on the defect site of a missing Au. It can be found that the adsorbed Ag tends to migrate to the subsurface of Au NP, which can be attributed to the fact that Au is more stable than Ag and by replacing Ag at the exposed facets it can stabilize the whole NP (Fig. 4). Furthermore, it is intriguing to note that the net charges of surface Au atoms adjacent to the subsurface of Ag are even more negative than those adjacent to Au (Supplementary Fig. S9b). This is clearly due to the higher electronegativity of Au than that of Ag, so that surface Au atoms bonding to Ag can take more cations. This indicates that the surface area around subsurface Ag can attract more Ag(I) ions after it is incorporated into Au NPs. Hence, a strong anisotropic growth process can be expected that Ag(I) ions may be selectively adsorbed and be sequentially reduced at the {100} facets of Au NPs, followed by diffusion and accumulation of Au atoms from other part of the cluster to the Ag-containing facets to bury them into the bulk. Accordingly, the reduction rate of Ag(I) is a key step during the growth of Au NWs. If the rate is too high, Ag atoms may not be incorporated into the bulk quickly enough at the very active {100} facets and other Ag(I) ions or even reduced Ag atoms may prefer to adsorb on other facets of gold NPs, leading to the failure of anisotropic growth of Au NWs. On the other hand, the preparation time would be too long if the reduction rate is too low.


Dendrimer-mediated hydrothermal synthesis of ultrathin gold nanowires.

Liu H, Cao X, Yang J, Gong XQ, Shi X - Sci Rep (2013)

DFT simulated growth mechanism of the formed NWs.Schematic illustration of the Au NW growth process involving adsorption and mergence of Ag atoms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3822382&req=5

f4: DFT simulated growth mechanism of the formed NWs.Schematic illustration of the Au NW growth process involving adsorption and mergence of Ag atoms.
Mentions: To take into consideration of surface defects in the realistic system, we also calculated an Au37Ag particle based on the octahedral Au38 model in which one Ag atom adsorbs on the defect site of a missing Au. It can be found that the adsorbed Ag tends to migrate to the subsurface of Au NP, which can be attributed to the fact that Au is more stable than Ag and by replacing Ag at the exposed facets it can stabilize the whole NP (Fig. 4). Furthermore, it is intriguing to note that the net charges of surface Au atoms adjacent to the subsurface of Ag are even more negative than those adjacent to Au (Supplementary Fig. S9b). This is clearly due to the higher electronegativity of Au than that of Ag, so that surface Au atoms bonding to Ag can take more cations. This indicates that the surface area around subsurface Ag can attract more Ag(I) ions after it is incorporated into Au NPs. Hence, a strong anisotropic growth process can be expected that Ag(I) ions may be selectively adsorbed and be sequentially reduced at the {100} facets of Au NPs, followed by diffusion and accumulation of Au atoms from other part of the cluster to the Ag-containing facets to bury them into the bulk. Accordingly, the reduction rate of Ag(I) is a key step during the growth of Au NWs. If the rate is too high, Ag atoms may not be incorporated into the bulk quickly enough at the very active {100} facets and other Ag(I) ions or even reduced Ag atoms may prefer to adsorb on other facets of gold NPs, leading to the failure of anisotropic growth of Au NWs. On the other hand, the preparation time would be too long if the reduction rate is too low.

Bottom Line: The formation of uniform Au NWs was optimized by varying the Au/Ag salt molar ratio, dendrimer stabilizers, and reaction solvent, temperature, and time.A novel growth mechanism involving a synergic facet-dependent deposition/reduction of Ag(I) and oriented migration of Au atoms is proposed based on density functional theory calculations and the experimental results.This work can significantly expand the scope of dendrimers as stabilizers to generate metal NWs in aqueous solution that may be further functionalized for different applications.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, People's Republic of China [2] College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, People's Republic of China.

ABSTRACT
We report the use of poly(amidoamine) dendrimers as stabilizers to synthesize ultrathin Au nanowires (NWs) with a diameter of 1.3 nm via a hydrothermal approach. The formation of uniform Au NWs was optimized by varying the Au/Ag salt molar ratio, dendrimer stabilizers, and reaction solvent, temperature, and time. A novel growth mechanism involving a synergic facet-dependent deposition/reduction of Ag(I) and oriented migration of Au atoms is proposed based on density functional theory calculations and the experimental results. This work can significantly expand the scope of dendrimers as stabilizers to generate metal NWs in aqueous solution that may be further functionalized for different applications.

No MeSH data available.