(5v) Electrochemistry and Self-Assembly of Complex Single-Walled Carbon Nanotube (SWNT) Nanostructures

Authors: 
Pasquali, M., Rice University


This work explores the optical and electrochemical properties of surfactant stabilized and individually-suspended SWNTs in aqueous media via application of various external stimuli. As a result, novel nanostructures are obtained, and this allows for the study of the inherent nanotube electronic and optical properties. The goal is to engineer SWNT systems which can be tuned by understanding the mechanism of the electrochemical and environmental reactions so that applications in nanophotonics, photovoltaics, and electronics can be effectively exploited.

A strategy to obtain a surfactant/polymer protective ?shell" that improves the stability and luminescence signal of individual SWNTs is presented. We used literature evidence of fluorescence emission shifts to understand the interactions between polymers and surfactants and show how morphological changes induced by extrinsic factors distort the SWNT luminescence. We developed an in-situ polymerization which creates an outer shell around the SWNT micelle that resulted in suspensions with stable luminescence at all pH, in saline buffers, and on the surface of living cells.1

Nanoparticle-nanotube structures were also fabricated by exploiting the electrochemical properties of SWNTs upon activation with alternating electromagnetic fields (EM). Under EM, metallic SWNTs will preferentially polarize creating a localized apparent field enhancement at the tips due to their high aspect ratio and electronic properties -antenna behavior. This field enhancement can generate sufficient current densities which drive electron transfer reactions preferentially at their tips, reducing transition metal salts into nanoparticles. The selectivity is assessed using microscopic and spectroscopic techniques such as atomic force microscopy, UV-vis absorbance, and Raman spectroscopy. At the end we obtain a system with tunable reaction conditions where spontaneous particle formations are controlled and selective deposition is obtained to form novel nanostructures.2

References

1. Duque, J.; et, al; JACS, 2008, 130, (8), 2626

2. Duque, J.; et, al; JACS, 2008, 130, (46), 15340