Tailoring Longitudinal Surface Plasmon Wavelengths, Scattering and Absorption Cross Sections of Gold Nanorods

Abstract

Tailoring the longitudinal surface plasmon wavelengths (LSPWs), scattering, and absorption cross sections of gold nanorods has been demonstrated by combining anisotropic shortening and transverse overgrowth and judiciously choosing starting Au nanorods. Shortening yields Au nanorods with decreasing lengths but a fixed diameter, while overgrowth produces nanorods with increasing diameters but a nearly unchanged length. Two series of Au nanorods with LSPWs varying in the same spectral range but distinct extinction coefficients are thus obtained. The systematic changes in the LSPW and extinction for the two series of Au nanorods are found to be in good agreement with those obtained from Gans theory. Dark-field imaging performed on two representative nanorod samples with similar LSPWs shows that the scattering intensities of the overgrown nanorods are much larger than those of the shortened nanorods. The experimental results are found to be in very good agreement with those obtained from finite-difference time-domain (FDTD) calculations. FDTD calculations further reveal that the scattering-to-extinction ratio increases linearly as a function of the diameter for Au nanorods with a fixed aspect ratio.

Highly sensitive sulphide mapping in live cells by kinetic spectral analysis of single Au-Ag core-shell nanoparticles

“…All other reagents were AR grade and were purchased from Shanghai Sinopharm. AuNR synthesis and purification procedures were adopted elsewhere 53,54 . The resulting AuNRs were used as seeds for the growth of AuNR-Ag NPs according to the literature with some modifications 55 .…”

Flow Dichroism as a Reliable Method to Measure the Hydrodynamic Aspect Ratio of Gold Nanoparticles

“…The particle sizes and shapes are such that the particles will posses an anisotropic optical response, not only because of the mere geometric properties, but mainly because of the presence of the surface plasmon 32,33 . The extinction curves as a function of wavelength are given in Figure 1.C for the Au-nanorods.…”

“…However, at the wavelengths used in the light scattering and rheo-optical experiments, the particles with the smallest aspect ratio show the strongest extinction. As the width of the rods is smaller than 30 nm, most of the extinction will come from absorption 33 . For the decahedral gold disks, the extinction curves in Figure 1.D are less clear but for all particles there is sufficient extinction to provide contrast at the wavelengths used in the optical setups.…”

“…Purely elastic scattering will be dominated by the larger particles, for the surface plasmon there is a more complex dependency on particle size and shape 33 .…”

Sideways Science

“…Several of the articles in this issue focus on using such near-field effects to advantage, and to understanding the nanoscale tools at our disposal. [2][3][4][5][6] We can expect to see many significant advances in this area in the future.Our current approach to understanding the nanoscale world is often one of pragmatism; we look at highly simplified systems. We try to study one structure and one phenomenon, but still, we often lack the ability to confirm that we have created the precise structure that we have targeted.…”