Molecular Perspective on Diazonium Adsorption for Controllable Functionalization of Single-Walled Carbon Nanotubes in Aqueous Surfactant Solutions

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• 作者：Shangchao Lin ; Andrew J. Hilmer ; Jonathan D. Mendenhall ; Michael S. Strano ; Daniel Blankschtein
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：May 16, 2012
• 年：2012
• 卷：134
• 期：19
• 页码：8194-8204
• 全文大小：684K
• 年卷期：v.134,no.19(May 16, 2012)
• ISSN：1520-5126

文摘

Functionalization of single-walled carbon nanotubes (SWCNTs) using diazonium salts allows modification of their optical and electronic properties for a variety of applications, ranging from drug-delivery vehicles to molecular sensors. However, control of the functionalization process remains a challenge, requiring molecular-level understanding of the adsorption of diazonium ions onto heterogeneous, charge-mobile SWCNT surfaces, which are typically decorated with surfactants. In this paper, we combine molecular dynamics (MD) simulations, experiments, and equilibrium reaction modeling to understand and model the extent of diazonium functionalization of SWCNTs coated with various surfactants (sodium cholate, sodium dodecyl sulfate, and cetyl trimethylammonium bromide). We show that the free energy of diazonium adsorption, determined using simulations, can be used to rank surfactants in terms of the extent of functionalization attained following their adsorption on the nanotube surface. The difference in binding affinities between linear and rigid surfactants is attributed to the synergistic binding of the diazonium ion to the local 鈥渉ot/cold spots鈥?formed by the charged surfactant heads. A combined simulation鈥搈odeling framework is developed to provide guidance for controlling the various sensitive experimental conditions needed to achieve the desired extent of SWCNT functionalization.