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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.

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(a) Schematics of different pathways of bi-AgNP formation illustrating 1-D, 2-D and 3-D growth in the system. (b–i) transmission electron microscopy (TEM) images of (b–d) representative 2-D bi-AgNP morphologies, (b,c) optimal preparation: 0.13 mM PAA 450 K, 0.04 mM AgDeNP seeds, 0.27 mM ascorbic acid, and 0.08 mM AgNO3, (c) low Ag, and (e) uniformly 3-D enlarged decahedra (high PAA). (f–i) representative bi-AgNPs prepared in presence of halides: (f,g) 3-D bi-AgNPs, (f) 75:1 Ag/KBr; (g) 38:1 Ag/KBr; (h) pentagonal rods with 1:12 Ag/KCl, (i) 1-D bi-AgNPs with 1:5 Ag/HCl. All ratios are molar. All scale bars are 50 nm. For detailed description of samples-see Supplementary Table S1.
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f1: (a) Schematics of different pathways of bi-AgNP formation illustrating 1-D, 2-D and 3-D growth in the system. (b–i) transmission electron microscopy (TEM) images of (b–d) representative 2-D bi-AgNP morphologies, (b,c) optimal preparation: 0.13 mM PAA 450 K, 0.04 mM AgDeNP seeds, 0.27 mM ascorbic acid, and 0.08 mM AgNO3, (c) low Ag, and (e) uniformly 3-D enlarged decahedra (high PAA). (f–i) representative bi-AgNPs prepared in presence of halides: (f,g) 3-D bi-AgNPs, (f) 75:1 Ag/KBr; (g) 38:1 Ag/KBr; (h) pentagonal rods with 1:12 Ag/KCl, (i) 1-D bi-AgNPs with 1:5 Ag/HCl. All ratios are molar. All scale bars are 50 nm. For detailed description of samples-see Supplementary Table S1.

Mentions: Key features of bi-AgNP synthesis by seeded growth of decahedral AgNPs, AgDeNPs, (pentagonal bipyramids, J13) are summarized in Fig. 1. The symmetry breaking in regrowth of high-purity decahedra3132 takes place upon the reduction of silver ions (AgNO3) by ascorbic acid (AA) with surface blocking by poly(acrylic acid) (PAA) giving rise to shape-selective deposition of new silver2223. Several types of well-defined bi-AgNPs are attainable by controlling four main parameters, the most crucial of which is i) surface-blocking by an adsorbing polymer (PAA of different molecular weights at different concentrations); followed by ii) the amount of new silver added, iii) reducing power (AA concentration and pH of the reaction), and iv) presenceofshape-selective agents (e.g. halides).


Symmetry Breaking by Surface Blocking: Synthesis of Bimorphic Silver Nanoparticles, Nanoscale Fishes and Apples
(a) Schematics of different pathways of bi-AgNP formation illustrating 1-D, 2-D and 3-D growth in the system. (b–i) transmission electron microscopy (TEM) images of (b–d) representative 2-D bi-AgNP morphologies, (b,c) optimal preparation: 0.13 mM PAA 450 K, 0.04 mM AgDeNP seeds, 0.27 mM ascorbic acid, and 0.08 mM AgNO3, (c) low Ag, and (e) uniformly 3-D enlarged decahedra (high PAA). (f–i) representative bi-AgNPs prepared in presence of halides: (f,g) 3-D bi-AgNPs, (f) 75:1 Ag/KBr; (g) 38:1 Ag/KBr; (h) pentagonal rods with 1:12 Ag/KCl, (i) 1-D bi-AgNPs with 1:5 Ag/HCl. All ratios are molar. All scale bars are 50 nm. For detailed description of samples-see Supplementary Table S1.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (a) Schematics of different pathways of bi-AgNP formation illustrating 1-D, 2-D and 3-D growth in the system. (b–i) transmission electron microscopy (TEM) images of (b–d) representative 2-D bi-AgNP morphologies, (b,c) optimal preparation: 0.13 mM PAA 450 K, 0.04 mM AgDeNP seeds, 0.27 mM ascorbic acid, and 0.08 mM AgNO3, (c) low Ag, and (e) uniformly 3-D enlarged decahedra (high PAA). (f–i) representative bi-AgNPs prepared in presence of halides: (f,g) 3-D bi-AgNPs, (f) 75:1 Ag/KBr; (g) 38:1 Ag/KBr; (h) pentagonal rods with 1:12 Ag/KCl, (i) 1-D bi-AgNPs with 1:5 Ag/HCl. All ratios are molar. All scale bars are 50 nm. For detailed description of samples-see Supplementary Table S1.
Mentions: Key features of bi-AgNP synthesis by seeded growth of decahedral AgNPs, AgDeNPs, (pentagonal bipyramids, J13) are summarized in Fig. 1. The symmetry breaking in regrowth of high-purity decahedra3132 takes place upon the reduction of silver ions (AgNO3) by ascorbic acid (AA) with surface blocking by poly(acrylic acid) (PAA) giving rise to shape-selective deposition of new silver2223. Several types of well-defined bi-AgNPs are attainable by controlling four main parameters, the most crucial of which is i) surface-blocking by an adsorbing polymer (PAA of different molecular weights at different concentrations); followed by ii) the amount of new silver added, iii) reducing power (AA concentration and pH of the reaction), and iv) presenceofshape-selective agents (e.g. halides).

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.


Related in: MedlinePlus