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We found that multiwalled carbon nanotubes (MWNTs) can be opened longitudinally by intercalation of lithium and ammonia followed by exfoliation. Intercalation of open-ended tubes and exfoliation with acid treatment and abrupt heating provided the best results. The resulting material consists of: (i) multilayered flat graphitic structures (nanoribbons), (ii) partially open MWNTs, and (iii) graphene flakes. We called the completely unwrapped nanotubes ex-MWNTs, and their large number of edge atoms makes them attractive for many applications.

Nanotube salts serve as initiators for the in situ polymerization of methyl methacrylate onto the surface of the nanotubes. The poly(methyl methacrylate)-grafted single-walled carbon nanotubes (SWNTs) are soluble in chloroform, tetrahydrofuran, and acetone. Atomic force microscopy images and Raman spectroscopy show that the SWNT bundles were exfoliated during the reduction, leading mostly to individual tubes.

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An important issue in developing applications for photopolymers in holography is the effect of film thickness on recording properties. Now it is possible to create these samples with a much wider range of thickness (d = 20-1400 mum) than was previously available. We exploit these recent advances in photopolymer processing to systematically evaluate how the dynamic range of a photopolymer depends on its thickness. The results illustrate that sample performance increases linearly with thickness as predicted by standard models of volume holography. However, above a critical thickness sample performance degrades, and the angular response of recorded plane-wave holograms shows evidence of grating curvature. These distortions are likely the result of photopolymer shrinkage, which in thicker samples occurs in a nonuniform fashion. This problem limits the performance of these photopolymers and is likely to be an issue for any photopolymer that undergoes comparable polymerization shrinkage.