A Novel Diameter‐Selective Functionalization of SWCNTs with Lithium Alkynylides

Abstract

Covalent functionalization by addition to the sidewalls ofsingle‐walled carbon nanotubes (SWCNTs) is one of the most important methods for the derivatization of carbon nanotubes. The nucleophilic addition of organometallic reagents (carbon‐ and nitrogen‐based carbanions) has recently become a widely used tool for the introduction of functional moieties onto the surface of this new carbon allotrope. The extension of this concept by the successful nucleophilic addition of in situ generated lithium acetylides to the SWCNT scaffold is presented herein. The chemically derivatized SWCNTs have been characterized in detail by TGA/MS, Raman, UV/Vis/NIR and fluorescence spectroscopy. On the basis of a detailed examination of the signals in the radial breathing‐mode region of the Raman spectra, the preferred functionalization of smaller‐diameter tubes has been clearly demonstrated.

Structure-Dependent Thermal Defunctionalization of Single-Walled Carbon Nanotubes

“…The larger diameter (12,3) nanotubes show maximum recovery of their RBM signals with pyrolysis at 350 °C, whereas temperatures greater than 500 °C appear necessary for full restoration from the smaller diameter (7,5) nanotubes. Additional data for the (10,3) and (8,3) species are included in Supporting Information. It seems clear that the pattern of recovery of the RBM Raman bands shows structure-dependent defunctionalization rates, with the largest diameter SWCNTs most readily losing their dodecyl addends.…”

“…8,9 The main such pattern is enhanced reactivity of smaller diameter nanotubes because of their greater sp 2 bond strain. 10 Although previously unexplored, variations in reactivity with structure should also affect the process of covalent defunctionalization, in which bonds to addends are broken to regenerate pristine SWCNTs.We report here a structure-resolved study of thermally induced defunctionalization reactions.Pristine SWCNT samples were first subjected to Billups-Birch reductive alkylation to obtain substantial sidewall functionalization with docedyl groups and solubility in organic solvents. 3,5 These dodecylated samples were then pyrolyzed for specific times at a range of controlled temperatures, after which changes in composition were monitored by optical absorption, fluorescence, and Raman spectroscopies and gravimetric analysis.…”

“…8,9 The main such pattern is enhanced reactivity of smaller diameter nanotubes because of their greater sp 2 bond strain. 10 Although previously unexplored, variations in reactivity with structure should also affect the process of covalent defunctionalization, in which bonds to addends are broken to regenerate pristine SWCNTs.…”

Chemistry of Carbon Nanotubes in Flow

“…Covalent and non-covalent chemical functionalization approaches play a fundamental role to debundle and stabilize CNTs in solution where their unique characteristics can be discerned and studied. Reagents, such as oxidants [6], diazonium salts [7][8], carbenes [9], nitronium ions [10], lithium alkynylides [11], and azomethine ylides [12], have been successfully employed for the covalent modification of CNTs. Despite this rich functionalization chemistry [13][14][15][16][17], only a few comparative studies [11,18] on the addition chemistry to CNT have been reported so far.…”

“…Reagents, such as oxidants [6], diazonium salts [7][8], carbenes [9], nitronium ions [10], lithium alkynylides [11], and azomethine ylides [12], have been successfully employed for the covalent modification of CNTs. Despite this rich functionalization chemistry [13][14][15][16][17], only a few comparative studies [11,18] on the addition chemistry to CNT have been reported so far. Motivated by this, we have evaluated the solubility and functionalization degree (FD) of single-wall carbon nanotube (SWCNT) samples that were subjected to different functionalization protocols through a continuous-flow approach.…”