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Stabilization of 4H hexagonal phase in gold nanoribbons.

Fan Z, Bosman M, Huang X, Huang D, Yu Y, Ong KP, Akimov YA, Wu L, Li B, Wu J, Huang Y, Liu Q, Png CE, Gan CL, Yang P, Zhang H - Nat Commun (2015)

Bottom Line: These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient conditions.Furthermore, the 4H hexagonal phases of silver, palladium and platinum can be readily stabilized through direct epitaxial growth of these metals on the 4H gold nanoribbon surface.Our findings may open up new strategies for the crystal phase-controlled synthesis of advanced noble metal nanomaterials.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.

ABSTRACT
Gold, silver, platinum and palladium typically crystallize with the face-centred cubic structure. Here we report the high-yield solution synthesis of gold nanoribbons in the 4H hexagonal polytype, a previously unreported metastable phase of gold. These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient conditions. Using monochromated electron energy-loss spectroscopy, the strong infrared plasmon absorption of single 4H gold nanoribbons is observed. Furthermore, the 4H hexagonal phases of silver, palladium and platinum can be readily stabilized through direct epitaxial growth of these metals on the 4H gold nanoribbon surface. Our findings may open up new strategies for the crystal phase-controlled synthesis of advanced noble metal nanomaterials.

No MeSH data available.


TEM analysis of bimetallic 4H/fcc Au@Ag and Au@Pd NRBs.(a) Bright-field TEM image of a typical Au@Ag NRB (scale bar, 200 nm). (b) Magnified TEM image of an Au@Ag NRB (scale bar, 10 nm). (c) A typical SAED pattern of an Au@Ag NRB taken along the [110]4H/[101]f zone axes. (d,e) HRTEM images of an Au@Ag NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (f) HAADF-STEM image (scale bar, 100 nm) and (g,h) the corresponding STEM-EDS elemental mappings of a typical Au@Ag NRB. (i) A typical bright-field TEM image of an Au@Pd NRB (scale bar, 50 nm). (j) Magnified TEM image of a typical Au@Pd NRB (scale bar, 20 nm). (k) SAED pattern of a typical Au@Pd NRB collected along the [110]4H/[101]f zone axes. (l,m) HRTEM images of an Au@Pd NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (n) HAADF-STEM image (scale bar, 50 nm) and (o,p) the corresponding STEM-EDS elemental mappings of a typical Au@Pd NRB.
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f4: TEM analysis of bimetallic 4H/fcc Au@Ag and Au@Pd NRBs.(a) Bright-field TEM image of a typical Au@Ag NRB (scale bar, 200 nm). (b) Magnified TEM image of an Au@Ag NRB (scale bar, 10 nm). (c) A typical SAED pattern of an Au@Ag NRB taken along the [110]4H/[101]f zone axes. (d,e) HRTEM images of an Au@Ag NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (f) HAADF-STEM image (scale bar, 100 nm) and (g,h) the corresponding STEM-EDS elemental mappings of a typical Au@Ag NRB. (i) A typical bright-field TEM image of an Au@Pd NRB (scale bar, 50 nm). (j) Magnified TEM image of a typical Au@Pd NRB (scale bar, 20 nm). (k) SAED pattern of a typical Au@Pd NRB collected along the [110]4H/[101]f zone axes. (l,m) HRTEM images of an Au@Pd NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (n) HAADF-STEM image (scale bar, 50 nm) and (o,p) the corresponding STEM-EDS elemental mappings of a typical Au@Pd NRB.

Mentions: Significantly, the as-prepared 4H Au NRBs can serve as the substrates for the epitaxial growth of other noble metals with the similar 4H structure stabilization. For instance, Au@Ag NRBs were synthesized by reduction of AgNO3 with oleylamine in the presence of Au NRBs (see Methods for details). The ribbon shape is well preserved after the deposition of Ag on the surface of Au NRBs (Fig. 4a,b). The chemical composition of Au@Ag NRBs is examined using STEM-EDS, giving an average Au/Ag atomic ratio of 1.0/1.7 (Supplementary Fig. 13). High-angle annular dark-field-STEM (HAADF-STEM) images of a typical Au@Ag NRB and the corresponding STEM-EDS elemental maps indicate the uniform distribution of Au and Ag (Fig. 4f–h), which is further confirmed using the STEM-EDS line scanning analysis (Supplementary Fig. 14). Interestingly, the SAED pattern of a typical Au@Ag NRB shows the [110]4H zone pattern together with streaks along the [001]4H direction, suggesting the coexistence of 4H and fcc structures with stacking faults and twins present along the [001]4H/[111]f direction (Fig. 4c). This indicates that the deposition of Ag on the surface of Au NRB led to the transformation of the original 4H Au to 4H/fcc polytypic structure. Such a structure was also confirmed using the selected-spot dark-field TEM analysis (Supplementary Fig. 15). HRTEM images of a typical Au@Ag NRB further prove the intergrowth of 4H and fcc phases (Fig. 4d,e), where the lattice fringes coherently extend from the centre to the edge of the Au@Ag NRB, indicating the epitaxial relationship between the Au core and the Ag shell (Fig. 4e). Moreover, most importantly, the 4H phase of Ag is stabilized through this epitaxial growth process. Similarly, polytypic 4H Pd and Pt can be stabilized via the same epitaxial growth process (Fig. 4i–p and Supplementary Figs 16–20). To the best of our knowledge, this is the first demonstration of 4H Pd and Pt nanostructure formation (Fig. 4k–m and Supplementary Fig. 18c–e).


Stabilization of 4H hexagonal phase in gold nanoribbons.

Fan Z, Bosman M, Huang X, Huang D, Yu Y, Ong KP, Akimov YA, Wu L, Li B, Wu J, Huang Y, Liu Q, Png CE, Gan CL, Yang P, Zhang H - Nat Commun (2015)

TEM analysis of bimetallic 4H/fcc Au@Ag and Au@Pd NRBs.(a) Bright-field TEM image of a typical Au@Ag NRB (scale bar, 200 nm). (b) Magnified TEM image of an Au@Ag NRB (scale bar, 10 nm). (c) A typical SAED pattern of an Au@Ag NRB taken along the [110]4H/[101]f zone axes. (d,e) HRTEM images of an Au@Ag NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (f) HAADF-STEM image (scale bar, 100 nm) and (g,h) the corresponding STEM-EDS elemental mappings of a typical Au@Ag NRB. (i) A typical bright-field TEM image of an Au@Pd NRB (scale bar, 50 nm). (j) Magnified TEM image of a typical Au@Pd NRB (scale bar, 20 nm). (k) SAED pattern of a typical Au@Pd NRB collected along the [110]4H/[101]f zone axes. (l,m) HRTEM images of an Au@Pd NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (n) HAADF-STEM image (scale bar, 50 nm) and (o,p) the corresponding STEM-EDS elemental mappings of a typical Au@Pd NRB.
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f4: TEM analysis of bimetallic 4H/fcc Au@Ag and Au@Pd NRBs.(a) Bright-field TEM image of a typical Au@Ag NRB (scale bar, 200 nm). (b) Magnified TEM image of an Au@Ag NRB (scale bar, 10 nm). (c) A typical SAED pattern of an Au@Ag NRB taken along the [110]4H/[101]f zone axes. (d,e) HRTEM images of an Au@Ag NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (f) HAADF-STEM image (scale bar, 100 nm) and (g,h) the corresponding STEM-EDS elemental mappings of a typical Au@Ag NRB. (i) A typical bright-field TEM image of an Au@Pd NRB (scale bar, 50 nm). (j) Magnified TEM image of a typical Au@Pd NRB (scale bar, 20 nm). (k) SAED pattern of a typical Au@Pd NRB collected along the [110]4H/[101]f zone axes. (l,m) HRTEM images of an Au@Pd NRB taken in the centre and at the edge, respectively (scale bars, 2 nm). (n) HAADF-STEM image (scale bar, 50 nm) and (o,p) the corresponding STEM-EDS elemental mappings of a typical Au@Pd NRB.
Mentions: Significantly, the as-prepared 4H Au NRBs can serve as the substrates for the epitaxial growth of other noble metals with the similar 4H structure stabilization. For instance, Au@Ag NRBs were synthesized by reduction of AgNO3 with oleylamine in the presence of Au NRBs (see Methods for details). The ribbon shape is well preserved after the deposition of Ag on the surface of Au NRBs (Fig. 4a,b). The chemical composition of Au@Ag NRBs is examined using STEM-EDS, giving an average Au/Ag atomic ratio of 1.0/1.7 (Supplementary Fig. 13). High-angle annular dark-field-STEM (HAADF-STEM) images of a typical Au@Ag NRB and the corresponding STEM-EDS elemental maps indicate the uniform distribution of Au and Ag (Fig. 4f–h), which is further confirmed using the STEM-EDS line scanning analysis (Supplementary Fig. 14). Interestingly, the SAED pattern of a typical Au@Ag NRB shows the [110]4H zone pattern together with streaks along the [001]4H direction, suggesting the coexistence of 4H and fcc structures with stacking faults and twins present along the [001]4H/[111]f direction (Fig. 4c). This indicates that the deposition of Ag on the surface of Au NRB led to the transformation of the original 4H Au to 4H/fcc polytypic structure. Such a structure was also confirmed using the selected-spot dark-field TEM analysis (Supplementary Fig. 15). HRTEM images of a typical Au@Ag NRB further prove the intergrowth of 4H and fcc phases (Fig. 4d,e), where the lattice fringes coherently extend from the centre to the edge of the Au@Ag NRB, indicating the epitaxial relationship between the Au core and the Ag shell (Fig. 4e). Moreover, most importantly, the 4H phase of Ag is stabilized through this epitaxial growth process. Similarly, polytypic 4H Pd and Pt can be stabilized via the same epitaxial growth process (Fig. 4i–p and Supplementary Figs 16–20). To the best of our knowledge, this is the first demonstration of 4H Pd and Pt nanostructure formation (Fig. 4k–m and Supplementary Fig. 18c–e).

Bottom Line: These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient conditions.Furthermore, the 4H hexagonal phases of silver, palladium and platinum can be readily stabilized through direct epitaxial growth of these metals on the 4H gold nanoribbon surface.Our findings may open up new strategies for the crystal phase-controlled synthesis of advanced noble metal nanomaterials.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.

ABSTRACT
Gold, silver, platinum and palladium typically crystallize with the face-centred cubic structure. Here we report the high-yield solution synthesis of gold nanoribbons in the 4H hexagonal polytype, a previously unreported metastable phase of gold. These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient conditions. Using monochromated electron energy-loss spectroscopy, the strong infrared plasmon absorption of single 4H gold nanoribbons is observed. Furthermore, the 4H hexagonal phases of silver, palladium and platinum can be readily stabilized through direct epitaxial growth of these metals on the 4H gold nanoribbon surface. Our findings may open up new strategies for the crystal phase-controlled synthesis of advanced noble metal nanomaterials.

No MeSH data available.