Reversible modification of the absorption properties of single-walled carbon nanotube thin films via nitric acid exposure

Hennrich, Frank; Wellmann, Ralf; Malik, Sharali; Lebedkin, Sergei; Kappes, Manfred M.

doi:10.1039/b208270e

Cited by 98 publications

(109 citation statements)

References 38 publications

(44 reference statements)

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“…142 In accordance with similar observations on graphite intercalation compounds, 143 the downshift is interpreted as a softening and elongation of the C-C bonds upon electron transfer to the SWCNTs, whereas electron withdrawal from the sp 2 lattice leads to a contraction and hardening of the lattice. As nitric acid and sulfuric acid are known to lead to a p-type doping of SWCNTs, 113,118,144,145 the observed upshifts of the tangential modes in acid-treated SWCNTs are very likely induced by intercalated acid molecules.…”

Section: Shift Of Raman Modesmentioning

confidence: 99%

Raman spectroscopy of covalently functionalized single‐wall carbon nanotubes

Graupner

2007

J Raman Spectroscopy

304

229

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Raman spectroscopy is one of the most extensively employed methods for the characterization of carbon nanotubes. In this review article, an overview about Raman spectroscopy as a tool for the characterization of functionalized single-walled carbon nanotubes (SWCNTs) is given. First, the relevant Raman modes in SWCNTs are introduced. Then, in a phenomenological approach, the effects that are observed for the individual modes in the Raman spectra are compiled and discussed. It is shown that special care has to be taken in order to separate the effects of functionalization, which are specific to a subset of the SWCNTs (metallic/semiconducting or diameter dependent), from changes in sample morphology or doping effects.

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Section: Shift Of Raman Modesmentioning

confidence: 99%

Raman spectroscopy of covalently functionalized single‐wall carbon nanotubes

Graupner

2007

J Raman Spectroscopy

304

229

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“…Thermal processing ͑"baking"͒ consisted of treating the samples in flowing pure argon at 1000°C for 12 h, to remove from the sample the nitric acid, used during purification. 6,12 Sample B was a second piece of the same film as sample A; samples C and CЈ were the same piece of film measured both before and after baking. Spectra were taken on three different spectrometers with sufficient spectral overlap to allow unambiguous merging of transmittance curves: a Bruker 113v Fourier-transform interferometer ͑20-3000 cm −1 ͒ with a Si bolometer ͑FIR͒ and a DTGS detector ͑MIR͒, a homemade near infrared/visible/UV spectrometer based on a Perkin-Elmer monochromator ͑2000-40 000 cm −1 ͒, and a Perkin-Elmer Lambda 900 VIS/UV spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Charge dynamics in transparent single-walled carbon nanotube films from optical transmission measurements

et al. 2006

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We report on the transmission over a wide frequency range ͑from the far infrared through the visible͒ of pristine and hole-doped, free-standing carbon nanotube films at temperatures between 50 and 300 K. Optical constants are estimated by Kramers-Kronig analysis of the transmittance. We see evidence in the far infrared for a gap below 10 meV. Hole doping causes a shift of spectral weight from the first interband transition into the far infrared. Temperature dependence in both the doped and undoped samples is restricted to the farinfrared region.

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“…Therefore, acid treatment to elute catalyst metals was performed as described previously. 27 All nanotube preparations were stored in a 1% SDS solution. Before use in the experiment, SWCNTs were acetone precipitated (21000 xg) and resuspended in bidistilled water, sedimented again by centrifugation, and finally taken up in growth media and diluted to final concentrations.…”

mentioning

confidence: 99%

“…The soot is somewhat richer in oxygen than the target rod, likely because of the metal oxidation and gas adsorption in transfer. 27 Viability Tests. MTT Assay.…”

mentioning

confidence: 99%

Oops They Did It Again! Carbon Nanotubes Hoax Scientists in Viability Assays

2006

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New materials of emerging technological importance are single-walled carbon nanotubes (SWCNTs). Because SWCNTs will be used in commercial products in huge amounts, their effects on human health and the environment have been addressed in several studies. Inhalation studies in vivo and submerse applications in vitro have been described with diverging results. Why some indicate a strong cytotoxicity and some do not is what we report on here. Data from A549 cells incubated with carbon nanotubes fake a strong cytotoxic effect within the MTT assay after 24 h that reaches roughly 50%, whereas the same treatment with SWCNTs, but detection with WST-1, reveals no cytotoxicity. LDH, FACSassisted mitochondrial membrane potential determination, and Annexin-V/PI staining also reveal no cytotocicity. SWCNTs appear to interact with some tetrazolium salts such as MTT but not with others (such as WST-1, INT, XTT). This interference does not seem to affect the enzymatic reaction but lies rather in the insoluble nature of MTT−formazan. Our findings strongly suggest verifying cytotoxicity data with at least two or more independent test systems for this new class of materials (nanomaterials). Moreover, we intensely recommend standardizing nanotoxicological assays with regard to the material used: there is a clear need for reference materials. MTT−formazan crystals formed in the MTT reaction are lumped with nanotubes and offer a potential mechanism to guide bioremediation and clearance for SWCNTs from "contaminated" tissue. SWCNTs are good supporting materials for tissue growth, as attachment of focal adhesions and connections to the cytoskeleton suggest.

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Reversible modification of the absorption properties of single-walled carbon nanotube thin films via nitric acid exposure

Cited by 98 publications

References 38 publications

Raman spectroscopy of covalently functionalized single‐wall carbon nanotubes

Raman spectroscopy of covalently functionalized single‐wall carbon nanotubes

Charge dynamics in transparent single-walled carbon nanotube films from optical transmission measurements

Oops They Did It Again! Carbon Nanotubes Hoax Scientists in Viability Assays

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