A method for the reliable fabrication of less than 200 nm thick, free-standing purified-SWNT films having large surface areas exceeding several cm 2 is described. Films were characterized using a variety of optical, microscopic and spectroscopic methods. The procedure was also used to prepare thin films of as-prepared, acid-cut and octadecylamine (ODA) functionalized SWNTs. Such samples allow facile transmission measurements of SWNT derived solids.

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Exposure of thin films of as-prepared single-walled carbon nanotubes (SWNT) to nitric acid induces dramatic bleaching of the first and second interband transitions of semiconducting tubes (S1 and S2). These near-IR absorption features can be restored by annealing of treated SWNT films to elevated temperatures. Annealing may also be accomplished by visible laser irradiation thus allowing for spatially resolved modifications to SWNT thin film optical absorption.

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Photoluminescence ͑PL͒ laser microscopy was applied to determine optical transition energies E 11 and E 22 of individual semiconducting single-walled carbon nanotubes ͑SWNTs͒ suspended on top of carbon nanotube "forests," grown by chemical vapor deposition ͑CVD͒ on silicon substrates. A uniform increase of E 11 and E 22 energies by 40-55 and 24-48 meV, respectively, was found for 19 different ͑n , m͒ nanotube species suspended in air or a vacuum-relative to SWNTs in a reference water-surfactant dispersion. CVD-grown SWNTs embedded in paraffin oil and 1-methylnaphthalene show nearly the same PL peak positions as SWNTs in aqueous dispersion, indicating similar dielectric screening of excitons in SWNTs in these media.