Spiky Gold Nanoshells: Synthesis and Enhanced Scattering Properties

Abstract

Gold nanoshells covered with sharp rods called “spiky gold nanoshells” are synthesized by employing a silver-assisted seed-growth method for heterogeneous nanoparticle syntheses at polymer/water interfaces. It is found that silver ions in the growth solution play an important role in forming uniform gold shells as well as regulating the surface morphology. The optical properties of spiky gold nanoshells are investigated by single-particle scattering measurements, single-particle surface-enhanced Raman scattering measurements, and finite-difference time-domain modeling. The scattering intensities from isolated spiky nanoshells are significantly enhanced compared to those of conventional smooth shells. Moreover, due to the abundant hot spots on spiky nanoshells, the SERS signal is readily observed from single spiky shells with a very small intensity variation (35%), whereas there is no detectable signal from isolated smooth shells. These results demonstrate that our synthetic method provides a straightforward way to organize metal nanoparticles into well-defined assemblies with enhanced scattering properties.

Gold Nanostar Substrates for Metal-Enhanced Fluorescence through the First and Second Near-Infrared Windows

“…For both fluorophores used, fluorescence enhancement was significantly larger with L-AuNS substrates, compared to S-AuNS substrates. On the one hand, this observation may be due to the higher degree of spectral overlap between the LSPR of the L-AuNS substrates with the PL excitation and emission spectra of the AF dyes (Figure 2g), which is crucial to obtaining the maximum 68,69 and has been shown to depend on the morphology of the spikes, with sharper tips producing larger enhancements. 70 In sensing applications, the ability to predict and adjust the enhancement factor of plasmonic substrates is crucial for optimizing the quantitative detection of different analytes in their respective concentration ranges, by tuning the sensitivity and dynamic range of the array.…”

Modal interference in spiky nanoshells

“…As described in our previous publications [30][31][32][33], spiky nanoshells were produced using a surfactant-assisted seed growth method. The nanoshells used in this study have a polystyrene core with a diameter of 95 nm, with spikes estimated to be less than 68 nm in length.…”

“…FDTD simulations were performed using Lumerical Solutions inc.'s FDTD package (versions 8.6 and 8.7) as previously described [31][32][33]. The simulation boundary conditions were set to Perfectly Matched Layers (PML), and a Total-Field Scattered-Field (TFSF) source was used to inject a plane wave into the simulation.…”

“…Spiky nanoshells are composed of randomly sized sharp gold spikes decorating the surface of a polystyrene core [30], and have tunable dipolar resonances in the visible and near-IR range [30][31][32]. It has been recently demonstrated that the disorder in these nanoshells generates spectrally and spatially broad dark quadrupole modes that enable highly efficient and reproducible Quadrupole Enhanced Raman Scattering(QERS) on a single particle level [33].…”

Solution-Phase Synthesis of Branched Metallic Nanoparticles for Plasmonic Applications

“…The Ag also provides a reductive condition on the tips of Au crystals caused by the galvanic current, and the Ag on the tips can be nearly replaced with Au. However, this method results in significant contamination of Ag in the core of Au nanostructures 43,44 . The remaining Ag and Ag can produce side effects in applications especially in biomedical use .…”