The interaction with surfactants changes from one carbon nanotube species to the other. We used this to replace non‐ionic surfactants by ionic ones. By fine‐tuning the replacement conditions, we covered some specific nanotubes with non‐ionic surfactants and the others with ionic ones. Addition of salt triggers precipitation of the species suspended by the ionic surfactant; this effectively leads to chiral selective enrichment of a carbon nanotube suspension. We hence produce an (8,4)‐enriched suspension by replacing a polyglycerol‐based custom amphiphile with the commercial SDBS and salting with NaCl.Relative sample composition, before and after the salting‐out procedure.

Stimulus responsive surfactants based on dendritic glycerol azobenzene conjugates were used to solubilize and debundle single-walled carbon nanotubes in aqueous media. Their debundling property as well as their reaggregation behavior upon irradiation with light was examined and light triggered reversible bundling and precipitation are shown.

A series of nonionic amphiphiles derived from polyglycerol dendrons were studied for their ability to solubilize and isolate single-walled carbon nanotubes. The amphiphiles possessed differently sized polar head groups, hydrophobic tail units, and various aromatic and non-aromatic groups between the head and tail groups. Absorbance analysis revealed that amphiphiles with anchor groups derived from pyrene were far inferior to those that possessed simple linear aliphatic tail groups. Absorbance and near-infrared fluorescence analyses revealed a weak dependence on the dendron size of the head group, but a strong positive trend in suspended nanotube density and fluorescence intensity for amphiphiles with longer tail units. Variations in the moieties linking the head and tail groups led to a range of effects on the suspensions, with linkers imparting flexibility and a bent shape that gave improved performance overall. This was illustrated most dramatically by a pair of benzamide-containing amphiphiles, the para isomer of which showed evidence in the fluorescence data of increased nanotube aggregate formation when compared with the meta isomer. In addition, statistical AFM was used to illustrate more directly the microscopic differences between amphiphiles that were effective at nanotube bundle disruption and those that were not.

Molecular switch compounds, consisting of aromatic anchoring groups connected to a spiropyran moiety, are exploited for carbon nanotube functionalization. The effect of the different anchor groups on sample distribution and debundling efficiency is investigated as well as the influence of the anchorswitch distance and hence tubeswitch separation. Morphologically similar anchor groups result in similar chiral compositions of the sample. With smaller separation, the tubeswitch interaction strength increases as well as the lifetime of the ring opened isomer.

Single‐walled carbon nanotubes (SWCNTs) are functionalized with a spiropyran derivative, which is attached non‐covalently to the SWCNT's sidewall via a pyrene anchor group. Using this non‐covalent functionalization strategy, individual SWCNTs can be stabilized in solution without the need for additional surfactants. Bright luminescence confirms the presence of individual tubes in the thus‐prepared samples. In these samples, the majority of pyrene‐spiropyran molecules are attached to the walls of the SWCNTs. Upon complex formation with the SWCNT, the switching moiety retains its ability to switch, i.e., to undergo reversible transformations between the closed spiropyran and the opened merocyanine form, and is stable over many cycles of operation.

Carbon nanotubes (CNTs) were solubilized using akyl/polyglycerol amphiphiles. Similar cosurfactants, bearing different aromatic moieties between head and tail, were added to these samples. The interaction strength between these amphiphiles and CNTs changes depending on the inserted aromatic moieties. The insertion of a phenyl ring allows the amphiphile to replace the starting one indicating a higher interaction strength, while the insertion of a triazol pentagon does not, suggesting that the interaction strength is lower. The replacement was monitored via PLE mapping. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Aqueous dispersions of carbon nanotubes (CNTs) were obtained by noncovalent adsorption of an azobenzene derivative carrying polyglycerol dendric structures. UV/Vis absorption spectra and photoluminescence maps were recorded to confirm successful nanotube debundling and suspension. Comparison to dispersion of nanotubes using sodium dodecyl sulfate (SDS) revealed shifts of the nanotube E22 excitation peaks from 28 to 67 meV as well as shifts from 21 to 37 meV of the E11 emission peaks.