Abstract
The reaction of neutral single-walled carbon nanotubes (SWCNTs) with diazonium salts proceeds with a high selectivity towards metallic carbon nanotube species; this reaction is well-understood and the mechanism has been elucidated. In the present joint theoretical and experimental study, we investigate the reaction of negatively charged SWCNTs - carbon nanotubides - with diazonium salts. Our density functional theory calculations predict a stronger binding of the aryl diazonium cations to charged metallic SWCNTs species and therefore lead to a preferential addend binding in the course of the reaction. The Raman resonance profile analysis on the reductive arylation of carbon nanotubides obtained by the solid state intercalation approach with potassium in varying concentrations confirms the predicted preferred functionalization of metallic carbon nanotubes. Furthermore, we were also able to show that the selectivity for metallic SWCNT species could be further increased when low potassium concentrations (K : C < 1 : 200) are used for an initial selective charging of the metallic species. Further insights into the nature of the bound addends were obtained by coupled thermogravimetric analysis of the functionalized samples.
Highlights
The reaction of neutral single-walled carbon nanotubes (SWCNTs) with diazonium salts proceeds with a high selectivity towards metallic carbon nanotube species; this reaction is well-understood and the mechanism has been elucidated
In a ground-breaking work, Strano et al.[10] have shown that the covalent functionalization of surfactant-individualized, neutral SWCNTs with diazonium salts proceeds with a high selectivity towards metallic carbon nanotube species
The reaction of neutral SWCNTs with diazonium salts proceeds with a high selectivity towards metallic carbon nanotube species, like previously observed in Birch type charged SWCNT samples
Summary
Semiconducting carbon nanotubes, as SWCNT bulk synthesis always yields mixtures of tubes with both electronic types as well as different diameters and lengths. Addition, the calculations reveal no correlation of the PhN2 radical/cation-SWCNTs interaction energy with varying tube diameters Based on these theoretical results, charged metallic SWCNTs should be more reactive than their semiconducting counterparts, which is in perfect agreement with the results we obtained on Birch type reduced systems.[27] In the present experimental approach, we carried out the SWCNT reduction in a wellde ned potassium intercalation[30] protocol with a variation of the applied charge density in the course of the reductive diazotation reaction (Scheme 1).[29] The successful arylation of the carbon nanotubes was veri ed by a thermogravimetric (TG) product analysis, coupled with gas-chromatographic (GC) separation and mass-spectrometric (MS) characterization (TG-MS and TG-GCMS).
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