14 research outputs found
Synthesis and Isolation of {110}-Faceted Gold Bipyramids and Rhombic Dodecahedra
Two {110}-faceted gold nanostructuresârhombic dodecahedra and obtuse triangular bipyramidsâhave been synthesized via a Ag-assisted, seed-mediated growth method. The combination of a Clâ-containing surfactant with a low concentration of Ag+ plays a role in the stabilization of the {110} facets. To the best of our knowledge, this is the first reported synthesis of a {110}-faceted bipyramid structure
Synthesis and Isolation of {110}-Faceted Gold Bipyramids and Rhombic Dodecahedra
Two {110}-faceted gold nanostructuresârhombic dodecahedra and obtuse triangular bipyramidsâhave been synthesized via a Ag-assisted, seed-mediated growth method. The combination of a Clâ-containing surfactant with a low concentration of Ag+ plays a role in the stabilization of the {110} facets. To the best of our knowledge, this is the first reported synthesis of a {110}-faceted bipyramid structure
A Directional Entropic Force Approach to Assemble Anisotropic Nanoparticles into Superlattices
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102143/1/14230_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102143/2/ange_201306009_sm_miscellaneous_information.pd
Chemically isolating hot spots on concave nanocubes
The article of record as published may be found at http://dx.doi.org/10.1021/nl3032235We report a simple and general strategy for selectively
exposing and functionalizing the sharp corners of concave nanocubes,
which are the SERS hot spots for such structures. This strategy takes
advantage of the unique shape of the concave cubes by coating the particles
with silica and then etching it away to expose only the corner regions, while
maintaining the silica coating in the concave faces. These corner regions
can then be selectively modified for improved enhancement and signal
response with SERSFunded by Naval Postgraduate School.AFOSRNational Science FoundationNERC (DOE)Awards No. N00244-09-1-0012 and N00244-09-1-0071 (NPS)Award no. FA9550-09-1-0294 (AFOSR)DMR-0520513 and DMR-01121262 (NSF)Award no. DE-SC0000989 (NERC
Concave Cubic Gold Nanocrystals with High-Index Facets
A new class of gold nanostructures, concave nanocubes, enclosed by 24 high-index {720} facets, have been prepared in a monodisperse fashion by a modified seed-mediated synthetic method. The Clâ counterion in the surfactant plays an essential role in controlling the concave morphology of the final product. The concave nanocubes exhibit higher chemical activities compared with low-index {111}-faceted octahedra.
Includes Supporting Information
Defining Rules for the Shape Evolution of Gold Nanoparticles
The roles of silver ions and halides (chloride, bromide,
and iodide) in the seed-mediated synthesis of gold nanostructures
have been investigated, and their influence on the growth of 10 classes
of nanoparticles that differ in shape has been determined. We systematically
studied the effects that each chemical component has on the particle
shape, on the rate of particle formation, and on the chemical composition
of the particle surface. We demonstrate that halides can be used to
(1) adjust the reduction potential of the gold ion species in solution
and (2) passivate the gold nanoparticle surface, both of which control
the reaction kinetics and thus enable the selective synthesis of a
series of different particle shapes. We also show that silver ions
can be used as an underpotential deposition agent to access a different
set of particle shapes by controlling growth of the resulting gold
nanoparticles through surface passivation (more so than kinetic effects).
Importantly, we show that the density of silver coverage can be controlled
by the amount and type of halide present in solution. This behavior
arises from the decreasing stability of the underpotentially deposited
silver layer in the presence of larger halides due to the relative
strengths of the Ag<sup>+</sup>/Ag<sup>0</sup>âhalide and Au<sup>+</sup>/Au<sup>0</sup>âhalide interactions, as well as the
passivation effects of the halides on the gold particle surface. We
summarize this work by proposing a set of design considerations for
controlling the growth and final shape of gold nanoparticles prepared
by seed-mediated syntheses through the judicious use of halides and
silver ions
Anisotropic Nanoparticles as Shape-Directing Catalysts for the Chemical Etching of Silicon
Anisotropic
Au nanoparticles have been used to create a library
of complex features on silicon surfaces. The technique provides control
over feature size, shape, and depth. Moreover, a detailed study of
the etching rate as a function of the nanoparticle surface facet interfaced
with the silicon substrate suggested that the etching is highly dependent
upon the facet surface energy. Specifically, the etching rate for
Au nanocubes with {100}-terminated facets was âŒ1.5 times higher
than that for triangular nanoprisms with {111} facets. Furthermore,
this work gives fundamental insight into the mechanism of metal-catalyzed
chemical etching