Water-Soluble Single-Walled Carbon Nanotubes via Noncovalent Sidewall-Functionalization with a Pyrene-Carrying Ammonium Ion

Abstract

In this communication, we describe the finding that sonication of solid single-walled carbon nanotubes (p-SWNT) in an aqueous solution of a pyrene-carrying ammonium ion 1 gave a transparent dispersion/solution of the nanotubes, which was characterized by transmission electron microscopy, UV-vis absorption, fluorescence and 1 H NMR spectroscopies. We showed evidence for the interaction of the nanotube sidewall and the pyrene moiety in the aqueous dispersion/solution.Since the discovery in 1991, 1 carbon nanotubes have been in the forefront of nanoscience and nanotechnology because of their many unique properties.2 Very recently, considerable attention has focused on the preparation of soluble carbon nanotubes 3 that would find many chemical applications in fundamental and practical research fields. Shortened SWNTs have been reported to be soluble in the organic solvents by derivatization with thionyl chloride and octadecylamine.3 Full-length SWNTs were rendered soluble in common organic solvents by ionic complexation with the terminal carboxylic acid in the SWNTs and octadecylamine. 4Carbon nanotubes have been reported to be soluble in the aqueous micellar solution of some detergents 5 and in the aqueous solutions of poly(vinyl pyrrolidone) and poly(styrene sulfonate).6 We describe in this paper the first preparation of sidewall-functionalized water-soluble single-walled carbon nanotubes (SWNTs). Here, a pyrene-carrying ammonium ion, trimethyl-(2-oxo-2-pyren-1-yl-ethyl)-ammonium bromide (1, Chart 1) was designed and synthesized as a solubilizer, since the pyrene moiety has been reported to have affinity with carbon nanotubes. 7SWNTs (HiPco TM ), 8 length obtained from Carbon Nanotechnologies Incorporated were placed in a ceramic boat and heated in a furnace for 18 h at 225 C in humid synthetic air, and then sonicated in concentrated HCl for 15 min. The tubes were collected by a filter (pore size, 100 nm), and then washed with sodium hydrogencarbonate. The nanotubes were collected by a filter (pore size, 100 nm), and then heated at 50C to obtain the purified SWNTs (p-SWNTs). The XPS measurements revealed that for the p-SWNTs, Fe2p 3=2 did not appear in the region of 706-714 eV. This is indicating that Fe from the catalyst for the synthesis of the SWNTs was almost removed by the purification procedure. The reaction of 1-(bromoacetyl)pyrene with trimethylamine in THF gave a precipitate, which was recrystallized from chloroform to give a compound 1 that was identified by 1 H NMR, IR and elemental analysis. 9The maximum solubility of 1 in water was ca. 2 mM (1 M ¼ 1 mol dm À3 ). It was found that 1 does not form a micelle in water since the surface tension of 1 on water was almost constant at 69 AE 1 mN/m for concentrations below 2 mM.About 1 mg of the solid p-SWNTs and compound 1 was sonicated with a bath-type sonicator (Branson 2210) in water (1 ¼ 1 mM) for 1 h. Centrifugation of the suspension for 1 h gave a black-colored transparent supernatant aqueous dispersion/ solution (Figure 1). TEM measurements for the aque...

Stability and thermal conductivity enhancement of carbon nanotube nanofluid using gum arabic

“…Functionalisation of CNTs has been carried out by oxidation process under extensive sonication with mixture of sulphuric acid and nitric acid [15]. Physical methods include addition of variety of dispersants, surfactants, polymers and aromatic compounds [16][17][18][19][20][21].…”

Ab initio study of noncovalent sidewall functionalization of carbon nanotubes

“…It is noteworthy that the terminal groups of aromatic molecules have been manipulated in experiments involving CNT functionalizations. 2,5,8 Our results for the binding energetics are compiled in Table I. We observe that the larger is the size of the adsorbed molecules, the stronger is the binding affinity with CNTs.…”

“…[1][2][3][4] Aqueous solution of unharmed individual CNTs has been required for fundamental study of opto-electronic properties of the CNT. 5,6 To attain these objectives, various methods of molecular adsorptions onto the outer surface of CNTs have been attempted. Among them, noncovalent methods are the most desirable because they are expected to preserve the mechanical and electronic advantages of CNTs.…”

The Unlikely Surfactant: DNA as a Ligand for Single-Walled Carbon Nanotubes

“…Initially, detergents like pyrene salts (Nakashima et al, 2002) and tensides, such as sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), or sodium cholate (SC) were used to generate stable nanotube suspensions (Ausman et al, 2000;Chen et al, 2001;O'Connell et al, 2002;Islam et al, 2003). The molecular structure of some of these is shown in Figure 1.…”