Fundamental Insights into the Reductive Covalent Cross-Linking of Single-Walled Carbon Nanotubes

Abstract

Single-walled carbon nanotubes (SWCNT) have been covalently cross-linked via a reductive functionalization pathway, utilizing negatively charged carbon nanotubides (KC). We have compared the use of difunctional linkers acting as molecular pillars between the nanotubes, namely, p-diiodobenzene, p-diiodobiphenyl, benzene-4,4'-bis(diazonium), and 1,1'-biphenyl-4,4'-bis(diazonium) salts as electrophiles. We have employed statistical Raman spectroscopy (SRS), a forefront characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spectrometry (TG-GC-MS) and aberration-corrected high-resolution transmission electron microscopy imaging series at 80 kV to unambiguously demonstrate the covalent binding of the molecular linkers. The present study shows that the SWCNT functionalization using iodide derivatives leads to the best results in terms of bulk functionalization homogeneity ( H) and degree of addition. Phenylene linkers yield the highest degree of functionalization, whereas biphenylene units induce a higher surface area with an increase in the thermal stability and an improved electrochemical performance in the oxygen reduction reaction (ORR). This work illustrates the importance of molecular engineering in the design of novel functional materials and provides important insights into the understanding of basic principles of reductive cross-linking of carbon nanotubes.

Controlling the Degree of Functionalization: In‐Depth Quantification and Side‐Product Analysis of Diazonium Chemistry on SWCNTs

“…Then, in the main mass loss region( marked by dashedvertical lines), the difference between high and low functionalization becomes distinct, revealing higherm ass losses for higher-functionalized samples. [16] Eventually,t he mass loss deriving exclusively from the desired functional group Dm(FG) can be calculated using Equation (1): This corroborates the results of TG-MS( see Figure 1) and provest hat the cleavage of the 4-iodophenyl group occurs in the main mass loss region between 150 8Ca nd Scheme1.ReactionofS WCNTsw ith a4 -iodobenzenediazonium salt in 1% SDBS solution resulting in the aryl-functionalized SWCNT-PhI.…”

“…The SDBS molecule, being physisorbed to the nanotubes, can surpass the washing procedure due to strong van‐der‐Waals interactions with the aromatic ring system of the SWCNTs which is common for molecules that can enclose the nanotubes and/or contain large π‐systems . Alternatively, the high mass loss temperature and the toluene peak are an indicator for lattice decomposition, which has been previously reported for graphene and SWCNTs . Eventually, the mass loss deriving exclusively from the desired functional group Δ m (FG) can be calculated using Equation : …”

A Straightforward Approach to Multifunctional Graphene

“…Last but not least, to face the problem of the direct identification of the functionalg roups grafted onto graphene, we analysed the mf-G with at echnique based on the coupling between TGA, gas chromatography and mass spectroscopy (TG-GC-MS). [12,37] We collected and eluted by GC the molecules and fragments in gas phase generated by the TGA at different temperatureo ft he analysis, to evaluate the composition of the samples. In conventionalT G-MS experiments the interpretation of the MS spectra collected is not easy because of the difficulty to predict the evolution of the organic moieties during the TGA process.…”

“…Last but not least, to face the problem of the direct identification of the functional groups grafted onto graphene, we analysed the mf‐G with a technique based on the coupling between TGA, gas chromatography and mass spectroscopy (TG‐GC‐MS) . We collected and eluted by GC the molecules and fragments in gas phase generated by the TGA at different temperature of the analysis, to evaluate the composition of the samples.…”

Covalent Inter‐Carbon‐Allotrope Architectures Consisting of the Endohedral Fullerene Sc3N@C80 and Single‐Walled Carbon Nanotubes

“…Therefore, the development of inter‐SWCNT–Sc 3 N@C 80 hybrids is quite intriguing. To accomplish high degrees of addition, our previously developed route to activate SWCNTs by using reductively charged SWCNTs as starting material was adopted …”