Toxicological Profiling of Highly Purified Single‐Walled Carbon Nanotubes with Different Lengths in the Rodent Lung and Escherichia Coli

Carbon nanotubes (CNTs) exhibit a number of physicochemical properties that contribute to adverse biological outcomes. However, it is difficult to define the independent contribution of individual properties without purified materials. A library of highly purified single‐walled carbon nanotubes (SWCNTs) of different lengths is prepared from the same base material by density gradient ultracentrifugation, designated as short (318 nm), medium (789 nm), and long (1215 nm) SWCNTs. In vitro screening shows length‐dependent interleukin‐1β (IL‐1β) production, in order of long > medium > short. However, there are no differences in transforming growth factor‐β1 production in BEAS‐2B cells. Oropharyngeal aspiration shows that all the SWCNTs induce profibrogenic effects in mouse lung at 21 d postexposure, but there are no differences between tube lengths. In contrast, these SWCNTs demonstrate length‐dependent antibacterial effects on Escherichia coli, with the long SWCNT exerting stronger effects than the medium or short tubes. These effects are reduced by Pluronic F108 coating or supplementing with glucose. The data show length‐dependent effects on proinflammatory response in macrophage cell line and antibacterial effects, but not on collagen deposition in the lung. These data demonstrate that over the length scale tested, the biological response to highly purified SWCNTs is dependent on the complexity of the nano/bio interface.     

Solution‐Based Processing of Optoelectronically Active Indium Selenide

Layered indium selenide (InSe) presents unique properties for high‐performance electronic and optoelectronic device applications. However, efforts to process InSe using traditional liquid phase exfoliation methods based on surfactant‐assisted aqueous dispersions or organic solvents with high boiling points compromise electronic properties due to residual surface contamination and chemical degradation. Here, these limitations are overcome by utilizing a surfactant‐free, low boiling point, deoxygenated cosolvent system. The resulting InSe flakes and thin films possess minimal processing residues and are structurally and chemically pristine. When employed in photodetectors, individual InSe nanosheets exhibit a maximum photoresponsivity of ≈5 × 10⁷ A W^?1, which is the highest value of any solution‐processed monolithic semiconductor to date. Furthermore, the surfactant‐free cosolvent system not only stabilizes InSe dispersions but is also amenable to the assembly of electronically percolating InSe flake arrays without posttreatment, which enables the realization of ultrahigh performance thin‐film photodetectors. This surfactant‐free, deoxygenated cosolvent approach can be generalized to other layered materials, thereby presenting additional opportunities for solution‐processed thin‐film electronic and optoelectronic technologies.     

Isolation of single-walled carbon nanotube enantiomers by density differentiation

Current methods of synthesizing single-walled carbon nanotubes (SWNTs) result in racemic mixtures that have impeded the study of left- and right-handed SWNTs. Here we present a method of isolating different SWNT enantiomers using density gradient ultracentrifugation. Enantiomer separation is enabled by the chiral surfactant sodium cholate, which discriminates between left- and right-handed SWNTs and thus induces subtle differences in their buoyant densities. This sorting strategy can be employed for simultaneous enrichment by handedness and roll-up vector of SWNTs having diameters ranging from 0.7 to 1.5 nm. In addition, circular dichroism of enantiomer refined samples enables identification of high-energy optical transitions in SWNTs. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Visualizing the local optical response of semiconducting carbon nanotubes to DNA-wrapping

We studied the local optical response of semiconducting single-walled carbon nanotubes to wrapping by DNA segments using high resolution tip-enhanced near-field microscopy. Photoluminescence (PL) near-field images of single nanotubes reveal large DNA-wrapping-induced red shifts of the exciton energy that are two times higher than indicated by spatially averaging confocal microscopy. Near-field PL spectra taken along nanotubes feature two distinct PL bands resulting from DNA-wrapped and unwrapped nanotube segments. The transition between the two energy levels occurs on a length scale smaller than our spatial resolution of about 15 nm.     

Biomolecule-directed assembly of self-supported, nanoporous, conductive, and luminescent single-walled carbon nanotube scaffolds

A single-walled carbon nanotube self-suspended network of exceptionally low density is formed by DNA-streptavidin-assisted assembly where the DNA complex serves as a cross-shaped point connector. The macroscopic nanotube aerogel is conductive and luminescent and presents an excellent scaffold for subsequent functionalization. For example, platinum and titanium dioxide coating of the nanotube network is demonstrated.     

Pluronic F108 coating decreases the lung fibrosis potential of multiwall carbon nanotubes by reducing lysosomal injury

We compared the use of bovine serum albumin (BSA) and pluronic F108 (PF108) as dispersants for multiwalled carbon nanotubes (MWCNTs) in terms of tube stability as well as profibrogenic effects in vitro and in vivo. While BSA-dispersed tubes were a potent inducer of pulmonary fibrosis, PF108 coating protected the tubes from damaging the lysosomal membrane and initiating a sequence of cooperative cellular events that play a role in the pathogenesis of pulmonary fibrosis. Our results suggest that PF108 coating could serve as a safer design approach for MWCNTs.     

Two-dimensional electronic spectroscopy reveals the dynamics of phonon-mediated excitation pathways in semiconducting single-walled carbon nanotubes

Electronic two-dimensional Fourier transform (2D-FT) spectroscopy is applied to semiconducting single-walled carbon nanotubes and provides a spectral and time-domain map of exciton-phonon assisted excitations. Using 12 fs long pulses, we resolve side-bands above the E(22) transition that correspond with the RBM, G, G', 2G and other multiphonon modes. The appearance of 2D-FT spectral cross-peaks explicitly resolves discrete phonon assisted population transfer that scatters excitations to the E(22) (Γ-pt) state, often through a second-order exciton-phonon coupling process. All 2D-FT peaks exhibit a strong peak amplitude modulation at the G-band period (21 fs) which we show originates from an impulsive stimulated Raman process that populates a ground-state G-band vibrational coherence over a 1.3 ps phonon lifetime.