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Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples

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ABSTRACT

A powerful approach to augment the diversity of well-defined metal nanoparticle (MNP) morphologies, essential for MNP advanced applications, is symmetry breaking combined with seeded growth. Utilizing this approach enabled the formation of bimorphic silver nanoparticles (bi-AgNPs) consisting of two shapes linked by one regrowth point. Bi-AgNPs were formed by using an adsorbing polymer, poly(acrylic acid), PAA, to block the surface of a decahedral AgNP seed and restricting growth of new silver to a single nucleation point. First, we have realized 2-D growth of platelets attached to decahedra producing nanoscale shapes reminiscent of apples, fishes, mushrooms and kites. 1-D bimorphic growth of rods (with chloride) and 3-D bimorphic growth of cubes and bipyramids (with bromide) were achieved by using halides to induce preferential (100) stabilization over (111) of platelets. Furthermore, the universality of the formation of bimorphic nanoparticles was demonstrated by using different seeds. Bi-AgNPs exhibit strong SERS enhancement due to regular cavities at the necks. Overall, the reported approach to symmetry breaking and bimorphic nanoparticle growth offers a powerful methodology for nanoscale shape design.

No MeSH data available.


Development of 2-D bi-AgNP morphologies with different amounts of added silver (the percentage is given in brackets relative to silver present in decahedral seeds).(a) Representative TEM images; (b) UV-vis spectra; and (c) optical photographs of samples: ➊ 0.008 mM (20%), ➋ 0.016 mM (40%), ➌ 0.04 mM (100%), ➍ 0.05 mM (120%), ➎ 0.08 mM (200%) and ➏ 0.13 mM (320%). All scale bars are 50 nm.
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f2: Development of 2-D bi-AgNP morphologies with different amounts of added silver (the percentage is given in brackets relative to silver present in decahedral seeds).(a) Representative TEM images; (b) UV-vis spectra; and (c) optical photographs of samples: ➊ 0.008 mM (20%), ➋ 0.016 mM (40%), ➌ 0.04 mM (100%), ➍ 0.05 mM (120%), ➎ 0.08 mM (200%) and ➏ 0.13 mM (320%). All scale bars are 50 nm.

Mentions: AgNP morphologies attained in different regrowth conditions are shown in Fig. 1a. The main focus of this report is the uniform 2-D bimorphic growth of a platelet/prism onto a decahedral seed (Fig. 2 and Supplementary Fig. S1). Among other growth modes of decahedra, most straightforward is uniform 3-D regrowth (uniform decahedra enlargement) where new silver deposits uniformly onto all ten (111) facets3132. In this report we have accessed 3-D regrowth of decahedra at low pH and in the presence of citrate at room temperature (Fig. 1e and Supplementary Fig. S2h). Several other regrowth modes can be accessed using halides: 1-D enlargement of decahedra resulting in pentagonal rods (Fig. 1a), mediated by chloride complexation and 3-D bimorphic growth of cubes and bipyramids from decahedral seeds (Fig. 1a and Supplementary Fig. S3) directed by bromide. Different pathways of the symmetry breaking in bi-AgNP growth demonstrated by this work (Figs 1 and 3) attest to the universality of the developed procedure. In particular, we have focused on 2-D bi-AgNPs to elucidate the role of synthetic parameters and to demonstrate control over shape selection.


Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples
Development of 2-D bi-AgNP morphologies with different amounts of added silver (the percentage is given in brackets relative to silver present in decahedral seeds).(a) Representative TEM images; (b) UV-vis spectra; and (c) optical photographs of samples: ➊ 0.008 mM (20%), ➋ 0.016 mM (40%), ➌ 0.04 mM (100%), ➍ 0.05 mM (120%), ➎ 0.08 mM (200%) and ➏ 0.13 mM (320%). All scale bars are 50 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015045&req=5

f2: Development of 2-D bi-AgNP morphologies with different amounts of added silver (the percentage is given in brackets relative to silver present in decahedral seeds).(a) Representative TEM images; (b) UV-vis spectra; and (c) optical photographs of samples: ➊ 0.008 mM (20%), ➋ 0.016 mM (40%), ➌ 0.04 mM (100%), ➍ 0.05 mM (120%), ➎ 0.08 mM (200%) and ➏ 0.13 mM (320%). All scale bars are 50 nm.
Mentions: AgNP morphologies attained in different regrowth conditions are shown in Fig. 1a. The main focus of this report is the uniform 2-D bimorphic growth of a platelet/prism onto a decahedral seed (Fig. 2 and Supplementary Fig. S1). Among other growth modes of decahedra, most straightforward is uniform 3-D regrowth (uniform decahedra enlargement) where new silver deposits uniformly onto all ten (111) facets3132. In this report we have accessed 3-D regrowth of decahedra at low pH and in the presence of citrate at room temperature (Fig. 1e and Supplementary Fig. S2h). Several other regrowth modes can be accessed using halides: 1-D enlargement of decahedra resulting in pentagonal rods (Fig. 1a), mediated by chloride complexation and 3-D bimorphic growth of cubes and bipyramids from decahedral seeds (Fig. 1a and Supplementary Fig. S3) directed by bromide. Different pathways of the symmetry breaking in bi-AgNP growth demonstrated by this work (Figs 1 and 3) attest to the universality of the developed procedure. In particular, we have focused on 2-D bi-AgNPs to elucidate the role of synthetic parameters and to demonstrate control over shape selection.

View Article: PubMed Central - PubMed

ABSTRACT

A powerful approach to augment the diversity of well-defined metal nanoparticle (MNP) morphologies, essential for MNP advanced applications, is symmetry breaking combined with seeded growth. Utilizing this approach enabled the formation of bimorphic silver nanoparticles (bi-AgNPs) consisting of two shapes linked by one regrowth point. Bi-AgNPs were formed by using an adsorbing polymer, poly(acrylic acid), PAA, to block the surface of a decahedral AgNP seed and restricting growth of new silver to a single nucleation point. First, we have realized 2-D growth of platelets attached to decahedra producing nanoscale shapes reminiscent of apples, fishes, mushrooms and kites. 1-D bimorphic growth of rods (with chloride) and 3-D bimorphic growth of cubes and bipyramids (with bromide) were achieved by using halides to induce preferential (100) stabilization over (111) of platelets. Furthermore, the universality of the formation of bimorphic nanoparticles was demonstrated by using different seeds. Bi-AgNPs exhibit strong SERS enhancement due to regular cavities at the necks. Overall, the reported approach to symmetry breaking and bimorphic nanoparticle growth offers a powerful methodology for nanoscale shape design.

No MeSH data available.