Gold Nanobipyramid‐Supported Silver Nanostructures with Narrow Plasmon Linewidths and Improved Chemical Stability

Abstract

Silver nanostructures with narrow plasmon linewidths and good chemical stability are strongly desired for plasmonic applications. Herein, a facile method is discussed for the preparation of Ag nanostructures with narrow plasmon linewidths and improved chemical stability through Ag overgrowth on monodispersed Au nanobipyramids. Structural evolution from bipyramid through rice to rod is observed, indicating that Ag atoms are preferentially deposited on the side surfaces of Au nanobipyramids. The resultant (Au nanobipyramid)@Ag nanostructures possess high size and shape uniformities, and much narrower plasmon linewidths than other Ag nanostructures. The spectral evolution of the supported Ag nanostructures is ascertained by both ensemble and single‐particle characterizations, together with electrodynamic simulations. Systematic measurements of the refractive index sensing characteristics indicate that Ag nanostructures in this study possess high index sensitivities and figure of merit (sensitivity divided by linewidth) values. Moreover, Ag nanostructures in this study exhibit greatly improved chemical stability. The superior sensing capability of Ag nanostructures in this study is further demonstrated by the detection of sulfide ions at a relatively low detection limit. Taken together, results of this study show that the Au‐nano­bipyramid‐supported Ag nanostructures will be an outstanding candidate for the design of ultrasensitive plasmonic sensing devices as well as for the development of other plasmon‐enabled technological applications.

Defect‐Directed Growth of Symmetrically Branched Metal Nanocrystals

“…[1] As shown in Figure S13, the branched NCs display broad LSPR peaks in the visible-NIR spectral range.H ere,f inite-difference time domain (FDTD) simulations were used to investigate far-and near-field behavior of these structures.The plasmonic behavior of ab ranched decahedron is presented in Figure 7, with ab ranched pentatwinned rod and ab ranched icosahedron being analyzed in Figures S14 and S15, respectively.Branched decahedron, pentatwinned rod, and icosahedron models were constructed using the geometrical dimensions of the synthesized structures;h owever,t he models were treated as all-Au NCs due to limitations in simulating complex Au/Pd distributions. [24,25] Thesimulations of all-AuNCprovide aqualitative analysis of EF behavior of the synthesized branched NCs. TheL SPR features from the symmetry of the branched NCs are maintained, but the LSPR peaks occur at different energies with respect to their experimental analogues.…”

“…TheL SPR features from the symmetry of the branched NCs are maintained, but the LSPR peaks occur at different energies with respect to their experimental analogues. [24,25] Thef ar-field (Figure 7a)a nd near-field (Figure 7e-j) plasmonic behavior was analyzed by changing the lights injection axis, k,a long the C 2 and C 5 rotational axis of the branched decahedron ( Figure S16). [3d,26] Figure 7reveals that the branched decahedron displays three major LSPR peaks:…”

Defect‐Directed Growth of Symmetrically Branched Metal Nanocrystals

“…The simulations of all‐Au NC provide a qualitative analysis of EF behavior of the synthesized branched NCs. The LSPR features from the symmetry of the branched NCs are maintained, but the LSPR peaks occur at different energies with respect to their experimental analogues …”

“…The plasmonic behavior of a branched decahedron is presented in Figure , with a branched pentatwinned rod and a branched icosahedron being analyzed in Figures S14 and S15, respectively. Branched decahedron, pentatwinned rod, and icosahedron models were constructed using the geometrical dimensions of the synthesized structures; however, the models were treated as all‐Au NCs due to limitations in simulating complex Au/Pd distributions . The simulations of all‐Au NC provide a qualitative analysis of EF behavior of the synthesized branched NCs.…”

Rapid synthesizing of gold nanobipyramids

“…Recently it has been shown that the edge of gold nanobipyramids (GBPs) are sharper than those of GNRs, which can yield local electric-field enhancements of GBPs 3 times larger than those of GNRs [4]. Thus substituting GNRs for GBPs should be beneficial in some applications [5,6], e.g. for photodynamic and photothermal therapies [7] probes for bio-applications [8], detection of influenza virus [9], surface-enhanced Raman scattering detection [10], as well as cancer cell imaging and photodynamic therapies [11].…”