Abstract:The reaction of Group 6 metals with SWCNT has the potential to bridge the resistive SWCNT . . . SWCNT junctions by the formation of "Cr(SWCNT) 2 " complexes analogous to Cr(C 6 H 6 ) 2 . This study reports that the formation of such species is very sensitive to oxidation by a residual iron oxide catalyst used for the growth of the SWCNTs and adsorbed/bound oxygen functionality. The reaction of raw HiPco SWCNTs with M(CO) 6 and (C 7 H 8 )M(CO) 3 (M = Cr, W) or (C 6 H 6 )Cr(CO) 3 results in the formation of the Group 6 metal oxides. Annealing and acid treating the HiPco SWCNTs to reduce the catalyst content allows for the observation of zero valent metals by XPS, while the use of very high purity SWCNTs and graphene allows for the addition of primarily zero valent Group 6 metals, including the bis-hexahapto metal complex.

Nanocarbon-based disordered, conductive, polymeric nanocomposite materials (DCPNs) are increasingly being adopted in applications across the breadth of materials science. DCPNs characteristically exhibit poor electroconductive properties and irreproducibility/ irreversibility in electronic phenomena, due largely to the percolative disordered nature intrinsic to such systems. The authors herein present an alternative approach toward enhancing the thermoresponsivity, repeatability, and reversibility of nanocarbon-based DCPNs in thermometric applications. This is empirically demonstrated using poly(octadecyl acrylate)-graf ted-multiwall carbon nanotubes (PODA-g-MWCNTs) synthesized via reversible addition−fragmentation chain-transfer (RAFT) polymerization. Synthesized PODA-g-MWCNTs exhibit repeatable, nearpyrexia sensitized, switch-like electronic responses across subtle glass transitions characterized by an exceptionally large positive temperature coefficient of resistance values of 7496.53% K −1 ± 3950.58% K −1 at 315.1 K (42.0 °C). This corresponds to a sizable transition rate of 17.39 kΩ K −1 ± 0.49 kΩ K −1 , and recoverable near room temperature resistance values of 246.17 Ω ± 12.19 Ω at 298.2 K (25.1 °C). Near-human body temperature sensitized PODA-g-MWCNTs assembled in this work are promising candidates for wearable temperature sensors and other thermometric applications.

We present a study of the seeded growth of copper on the surface of two classes of single-walled carbon nanotubes (SWNTs) in order to compare the effects of surface functional groups. Pyridine-functionalized HiPco SWNTs and ultrashort SWNTs (US-SWNTs) were synthesized (py-SWNTs and py-US-SWNTs, respectively), and the functionality was used as seed sites for copper, via an aqueous electroless deposition reaction, as a comparison to the carboxylic acid functionality present on piranha-etched SWNTs and the native US-SWNTs. UV-vis spectroscopy demonstrated the take-up of Cu(II) ions by the functionalized SWNTs. TEM showed that the SWNTs with pyridine functionality more rapidly produced a more even distribution of copper seeds with a narrower size distribution (3-12 nm for py-US-SWNTs) than those SWNTs with oxygen functional groups (ca. 30 nm), showing the adventitious role of the pyridine functional group in the seeding process. Seed composition was confirmed as Cu(0) by XPS and SAED. Copper growth rate and morphology were shown to be affected by degree of pyridine functionality, the length of the SWNT, and the electroless reaction solvent used.

The direction of electromigration of SWCNTs in the absence of surfactant depends on the presence of catalyst residue, surface functional groups and adsorbed metal ions.