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Resonances of nanoparticles with poor plasmonic metal tips.

Ringe E, DeSantis CJ, Collins SM, Duchamp M, Dunin-Borkowski RE, Skrabalak SE, Midgley PA - Sci Rep (2015)

Bottom Line: However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures.The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating.The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and NanoEngineering, Rice University, 6100 Main St., Houston TX 77005, USA.

ABSTRACT
The catalytic and optical properties of metal nanoparticles can be combined to create platforms for light-driven chemical energy storage and enhanced in-situ reaction monitoring. However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures. The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating. Here, nanometer resolution electron-based techniques (electron energy loss, cathodoluminescence, and energy dispersive X-ray spectroscopy) are used to show that Au particles incorporating a catalytically active but heavily damped metal, Pd, sustain multiple size-dependent localized surface plasmon resonances (LSPRs) that are narrow and strongly localized at the Pd-rich tips. The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.

No MeSH data available.


Related in: MedlinePlus

Structure, crystallography, and composition of Au/Pd octopods.(a) STEM bright field image. (b,c) Convergent beam electrondiffraction (CBED) patterns obtained at the positions indicated in a,<001> orientation; the arrows indicate the orientationcorrespondence between b and c. (d,e) HAADF-STEM imageof the region shown in a and associated Fourier transform,<001> orientation. (f) HAADF-STEM image of an octopodtilted −30°. (g) Model of an octopod tilted−30°. (h) Au Mα,Lα, and Lβ summed relativeX-ray intensity map. (i) Pd Lα,Lβ, and Kα summed relativeX-ray intensity map. (j) Relative X-ray intensity linescan of the AuMα and Pd Lα lines alongthe vertical axis in (h,i). Scale bars, 25 nm fora, 2 nm for d,5 nm−1 for e,50 nm for f,h,i.
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f1: Structure, crystallography, and composition of Au/Pd octopods.(a) STEM bright field image. (b,c) Convergent beam electrondiffraction (CBED) patterns obtained at the positions indicated in a,<001> orientation; the arrows indicate the orientationcorrespondence between b and c. (d,e) HAADF-STEM imageof the region shown in a and associated Fourier transform,<001> orientation. (f) HAADF-STEM image of an octopodtilted −30°. (g) Model of an octopod tilted−30°. (h) Au Mα,Lα, and Lβ summed relativeX-ray intensity map. (i) Pd Lα,Lβ, and Kα summed relativeX-ray intensity map. (j) Relative X-ray intensity linescan of the AuMα and Pd Lα lines alongthe vertical axis in (h,i). Scale bars, 25 nm fora, 2 nm for d,5 nm−1 for e,50 nm for f,h,i.

Mentions: During Au/Pd co-reduction synthesis, overgrowth of seed Au crystals in the<111> directions creates 8-branched alloyed structures with pointgroup symmetry Oh called octopods19. The well-definedprotrusions are terminated by flat {111} facets, seen as sharp edges in thescanning transmission electron microscopy (STEM) images (shown in red in Fig. 1g) and electron tomograms (examples in Supplementary Figs 1–2 and Supplementary Movie 1). Thisstellated external morphology is, rather surprisingly, formed by a twin-freestructure, as evidenced by nanometer resolution diffraction mapping (Fig. 1 and Supplementary Movie 2). The convergent beam electron diffraction(CBED) patterns in Fig. 1b,c show diffraction disks fromtwo different areas of the particle, while Supplementary Movie 2 tracks the CBED patterns across the entirenanoparticle. All the CBED patterns acquired (Fig. 1b,care two examples) are oriented along the same axes and have the same four-foldsymmetry attributable to the <100> orientation in an FCC materialat any position of the sub-nanometer probe. The consistency of orientation andsymmetry in the diffraction map implies consistency in lattice orientation, i.e.each region of the octopod has a similar crystallographic orientation, anobservation consistent with the lack of twinning in the structure. The singlecrystalline nature of the seeds is conserved through the synthesis, and thefully miscible Au and Pd form a continuous solid solution through the tips ofthe particle, rather than a patchy or polycrystalline core-shell structure, asshown by atomic resolution imaging (Fig. 1 and Supplementary Fig. 3). Diffractionpatterns, Fourier transforms of lattice images, and atomic spacing measurementsall yield a lattice spacing between that of Au and Pd, i.e. between 408 and398 pm, also consistent with a solid solution, within themeasurement error of a few percent. This lattice continuity, surface smoothness,and lack of scattering defects in Au/Pd particles are likely to have a favorableimpact on the quality and lifetime of the plasmon resonances20.


Resonances of nanoparticles with poor plasmonic metal tips.

Ringe E, DeSantis CJ, Collins SM, Duchamp M, Dunin-Borkowski RE, Skrabalak SE, Midgley PA - Sci Rep (2015)

Structure, crystallography, and composition of Au/Pd octopods.(a) STEM bright field image. (b,c) Convergent beam electrondiffraction (CBED) patterns obtained at the positions indicated in a,<001> orientation; the arrows indicate the orientationcorrespondence between b and c. (d,e) HAADF-STEM imageof the region shown in a and associated Fourier transform,<001> orientation. (f) HAADF-STEM image of an octopodtilted −30°. (g) Model of an octopod tilted−30°. (h) Au Mα,Lα, and Lβ summed relativeX-ray intensity map. (i) Pd Lα,Lβ, and Kα summed relativeX-ray intensity map. (j) Relative X-ray intensity linescan of the AuMα and Pd Lα lines alongthe vertical axis in (h,i). Scale bars, 25 nm fora, 2 nm for d,5 nm−1 for e,50 nm for f,h,i.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4663493&req=5

f1: Structure, crystallography, and composition of Au/Pd octopods.(a) STEM bright field image. (b,c) Convergent beam electrondiffraction (CBED) patterns obtained at the positions indicated in a,<001> orientation; the arrows indicate the orientationcorrespondence between b and c. (d,e) HAADF-STEM imageof the region shown in a and associated Fourier transform,<001> orientation. (f) HAADF-STEM image of an octopodtilted −30°. (g) Model of an octopod tilted−30°. (h) Au Mα,Lα, and Lβ summed relativeX-ray intensity map. (i) Pd Lα,Lβ, and Kα summed relativeX-ray intensity map. (j) Relative X-ray intensity linescan of the AuMα and Pd Lα lines alongthe vertical axis in (h,i). Scale bars, 25 nm fora, 2 nm for d,5 nm−1 for e,50 nm for f,h,i.
Mentions: During Au/Pd co-reduction synthesis, overgrowth of seed Au crystals in the<111> directions creates 8-branched alloyed structures with pointgroup symmetry Oh called octopods19. The well-definedprotrusions are terminated by flat {111} facets, seen as sharp edges in thescanning transmission electron microscopy (STEM) images (shown in red in Fig. 1g) and electron tomograms (examples in Supplementary Figs 1–2 and Supplementary Movie 1). Thisstellated external morphology is, rather surprisingly, formed by a twin-freestructure, as evidenced by nanometer resolution diffraction mapping (Fig. 1 and Supplementary Movie 2). The convergent beam electron diffraction(CBED) patterns in Fig. 1b,c show diffraction disks fromtwo different areas of the particle, while Supplementary Movie 2 tracks the CBED patterns across the entirenanoparticle. All the CBED patterns acquired (Fig. 1b,care two examples) are oriented along the same axes and have the same four-foldsymmetry attributable to the <100> orientation in an FCC materialat any position of the sub-nanometer probe. The consistency of orientation andsymmetry in the diffraction map implies consistency in lattice orientation, i.e.each region of the octopod has a similar crystallographic orientation, anobservation consistent with the lack of twinning in the structure. The singlecrystalline nature of the seeds is conserved through the synthesis, and thefully miscible Au and Pd form a continuous solid solution through the tips ofthe particle, rather than a patchy or polycrystalline core-shell structure, asshown by atomic resolution imaging (Fig. 1 and Supplementary Fig. 3). Diffractionpatterns, Fourier transforms of lattice images, and atomic spacing measurementsall yield a lattice spacing between that of Au and Pd, i.e. between 408 and398 pm, also consistent with a solid solution, within themeasurement error of a few percent. This lattice continuity, surface smoothness,and lack of scattering defects in Au/Pd particles are likely to have a favorableimpact on the quality and lifetime of the plasmon resonances20.

Bottom Line: However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures.The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating.The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and NanoEngineering, Rice University, 6100 Main St., Houston TX 77005, USA.

ABSTRACT
The catalytic and optical properties of metal nanoparticles can be combined to create platforms for light-driven chemical energy storage and enhanced in-situ reaction monitoring. However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures. The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating. Here, nanometer resolution electron-based techniques (electron energy loss, cathodoluminescence, and energy dispersive X-ray spectroscopy) are used to show that Au particles incorporating a catalytically active but heavily damped metal, Pd, sustain multiple size-dependent localized surface plasmon resonances (LSPRs) that are narrow and strongly localized at the Pd-rich tips. The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.

No MeSH data available.


Related in: MedlinePlus