Sulfate-Mediated End-to-End Assembly of Gold Nanorods

Abstract

There is interest in the controlled aggregation of gold nanorods (GNRs) for the production of extended nanoassemblies. Prior studies have relied upon chemical modification of the GNR surface to achieve a desired final aggregate structure. Herein we illustrate that control of electrolyte composition can facilitate end-to-end assembly of cetyltrimethylammonium-bromide-coated (CTAB) GNRs. By adjusting either the sulfate anion concentration or the exposure time it is possible to connect GNRs in chain-like assemblies. In contrast, end-to-end assembly was not observed in control experiments using monovalent chloride salts. We attribute the end-to-end assembly to the localized association of sulfate with exposed quaternary ammonium head groups of CTAB at the nanorod tip. To quantify the assembly kinetics, visible-near-infrared extinction spectra were collected over a predetermined time period, and the colloidal behavior of the GNR suspensions was interpreted using plasmon band analysis. Transmission electron microscopy and atomic force microscopy results support the conclusions reached via plasmon band analysis, and the colloidal behavior is consistent with Derjaguin-Landau-Verwey-Overbeek theory.

Smart design of high‐performance surface‐enhanced Raman scattering substrates

“…The optical properties of side‐by‐side, end‐to‐end, and end‐to‐side gold nanorod dimers have been investigated (Figure 3A). 40,41 First, in the side‐to‐side and end‐to‐side assembly, the extinction of the initial transverse LSPR band increases, and the band slightly red shifts to higher wavelengths, while the extinction of the longitudinal band decreases and blue shifts to lower wavelengths, thus resulting in the convergence of the two bands. However, in end‐to‐end assembly, the bands behave quite differently, in which neither the transverse nor the longitudinal band shifts.…”

In situ modulation of gold nanorod's surface charge drives the growth of end-to-end assemblies from dimers to large networks that enhance single-molecule fluorescence by 10 000-fold

“…16 Over the last two decades various wet-chemical and biochemical methods have been developed to link gold nanorods in an end-to-end fashion. 10,11,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Generally, different thiol-modied linkers are used with their thiol ends attached to nanorods and the other ends binding together via different interactions such as DNA origami formation, 17 antigen-antibody 24 and other bio recognitions, 23,33 molecular copolymerization, [19][20][21] p-p stacking, 31 hydrogen bonding 29 and hydrophobic interactions. 30 In a simpler approach a short dithiol ligand could also be used to directly link two nanorods in a single step.…”

Plasmonic Oligomers with Tunable Conductive Nanojunctions

“…A recent study provided an alternative to dithiolated linkers by showing that sulfate ions can mediate end-to-end attachment of gold nanorods. 19 We built upon this study to assemble gold bipyramids (GBPs) oligomers and refined the process to better control the chain formation kinetics (Figure 1). Figure S2).…”