Quantitative analyses of PEGylated phospholipids adsorbed on single walled carbon nanohorns by high resolution magic angle spinning 1H NMR

Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity

“…If we assume that the transverse relaxation time for the PEO chains at the inner surfaces or in crevices to 100 μs (sufficient for the observed signal loss) and the surface diffusion coefficient is on the order of 10 –12 m 2 /s (at least a factor of 3 slower than that at the outer surface of SWNTs), we obtain a diffusional path length >10 nm, that is comparable to the nanohorn extension. In other words, diffusing to the structural elements that experience crowded conditions for the PEO chains effectively quenches all NMR signals, both for the directly attached hydrophobic and for the anchored but dangling hydrophilic blocks, thereby explaining the observations in nanohorns …”

“…In contrast to SWNTs, nanohorns present both inner and outer surfaces for adsorbing molecules although it remains unclear (despite frequent sketches in the literature that suggest open access) to which extent in which medium those internal surfaces may become available. As another structural aspect, nanohorns often appear as “dahlia-shaped” aggregates with a multitude of narrow holes and crevices between the constituting horns. − Irrespective whether surfaces are internal to nanohorns or at crevices between aggregated nanohorns, if anchoring groups (such as alkyl chains in PEG-ylated lipids) attach to those surfaces, then the PEO blocks oriented away from the anchoring surface face a situation very different from that experienced by molecules attached to convex surfaces of individual nanotubes or their bundles. Namely, the chains will be pointed toward the limited inner volumes (either in a crevice or within a nanohorn) that must be crowded at high coverage.…”

“…Recently, the adsorption of PEG-ylated lipids (block copolymers with a large PEO block and a hydrophobic alkyl chain) in nanohorns (capped very short, ∼30 nm, single-walled CNTs, usually aggregated) has been studied by NMR . In striking contrast to previous findings with Pluronics-dispersed CNTs, ,, the adsorption of those lipids to the nanohorns resulted in a loss of the 1 H NMR signal, both for the hydrophobic alkyl and for the hydrophilic PEO blocks.…”

“…Second, we were inspired by the apparently opposing set of observations obtained from SWNTs and carbon nanohorns . We explicitly show that, indeed, the PPO block is attached to the SWNT surface so that it loses reorientational freedom.…”

Fasting-dependent Vascular Permeability Enhancement in Brown Adipose Tissues Evidenced by Using Carbon Nanotubes as Fluorescent Probes

“…Its diameter after the PLPEG coating would be about 14 nm as estimated from the occupied area estimation of PLPEG that adsorbed on the nanocarbons (Fig. 1A ) 19 . The wavelength region employed for the fluorescence imaging is indicated with a black rectangular in the fluorescence spectra (Fig.…”