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Article

Interactions of Small Molecules and Au Nanoparticles with Solubilized Single-Wall Carbon Nanotubes

Jian Zhang,^† Gangli Wang,^† Young-Seok Shon,^†^‡ Otto Zhou,^§ Richard Superfine,^§ and Royce W. Murray*^†

Kenan Laboratories of Chemistry and Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599

J. Phys. Chem. B, 2003, 107 (16), pp 3726–3732

DOI: 10.1021/jp0273068

Publication Date (Web): March 28, 2003

†

Kenan Laboratories of Chemistry.

‡

Present address: Department of Chemistry, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42101.

Department of Physics and Astronomy.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

Abstract

Oxidatively end-cut single-wall carbon nanotube (SWNT) has been solubilized (sol-SWNT) in organic solvents by refluxing in aniline and purified by silica gel chromatography. NMR analysis of sol-SWNT indicates that the ratio of nanotube carbons to aniline sites is 360:1. A hydroxy-stilbene fluorophore (trans-4-nitro-4‘-hydroxy stilbene, 1) adsorbs onto sol-SWNT, but can also be demonstrably ester-coupled to the nanotube material, based on comparisons of absorbance spectra. In the combinations of 1 and sol-SWNT made by ester-coupling and adsorption, the fluorescences of hydroxy-stilbene and of sol-SWNT could be excited selectively and separately. When exciting (500 nm) the sol-SWNT in the presence of adsorbed hydroxy-stilbene, the nanotube's emission intensity decreases, but the energetics are unchanged, whereas ester-coupled hydroxy-stilbene diminishes both the sol-SWNT energy and intensity. When exciting either adsorbed (at 372 nm) or ester-coupled stilbene (at 347 nm), the stilbene emission intensities are substantially reduced, and a weak, photosensitized sol-SWNT emission could be seen. Energy transfer quenching of the stilbene by the nanotube structure produces some quantity of excited states that relax by emission. Mixed monolayer-protected Au clusters adsorb strongly onto both end-opened SWNT and sol-SWNT. Adsorption of MPCs with hydroxyl groupings in the mixed monolayer onto end-opened SWNTs occurred without change in shape of the nanotube bundles but could effect the rolling up of the more flexible sol-SWNTs. Amine-labeled MPCs were less aggressive adsorbers and the 15−20 nm nanotube bundles of sol-SWNT could be imaged, outlined with the adsorbed nanoparticles.