simple wall carbon nanotubes

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Electronic transport properties of double-wall carbon nanotubes

Electronic transport properties of double-wall carbon nanotubes

and 4(b) corresponds to a full-shell charge state. IV. CONCLUSIONS In conclusion, we have observed eight-electron periodicity in the single-particle stability diagram of DWCNT QDs. The charging energy, level spacing, intershell coupling strength, mismatching parameters, and coupling strength to the leads are obtained. The full energy shell and partially filled shell states are determined by examining the excitation lines. The extraction of the intershell coupling strengths in DWCNTs from the spectroscopy measurements was never performed before. The simple and standard spectroscopy measurement provides a relatively easy approach to investigate and to better understand the intershell couplings in DWCNTs and MWCNTs, which are crucial for their application in nanodevices.
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Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition (CCVD) method

Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition (CCVD) method

. Ž . g day of single-wall carbon nanotubes SWNTs is possible by CCVD method similar to the two other techniques used until now, arc discharge and laser evaporation. Indeed, the method using the catalytic decomposition of methane over well-dispersed metal particles supported on MgO at 10008C has been adapted to produce large quantities of SWNTs. The synthesis yield was easily estimated, after removing the support by a simple acidic treatment to obtain a product containing SWNTs of high purity. The SWNTs content in the purified samples was esti- mated approximately to be of the order of 70–80%.
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Sample preparation protocols for realization of reproducible characterization of single-wall carbon nanotubes

Sample preparation protocols for realization of reproducible characterization of single-wall carbon nanotubes

As-grown SWCNT material typically consists of nanotube bundles and may also include other carbonaceous material and metallic particles (catalyst). SWCNT bundles can adsorb simple gases in external grooves, voids, the nanotube interior, and sometimes interstitial channels as well as on the external surface. Grooves, interior and external surfaces of nanotube bundles are characterized by relatively well-defined binding energy as compared to other adsorption sites in the SWCNT material, and steps may be identified on the isotherm corresponding to adsorption on these sites. Other carbonaceous materials may include nanotube debris (shells, nanotube fragments), graphitic particles, amorphous carbon, and possibly residual solid precursor material. Debris, graphitic particles, and residual solid precursor material can adsorb gases on highly polyenergetic surface adsorption sites. Metallic particles are typically covered by multi-layer-thick graphitic shells, thus they exhibit gas adsorption properties similar to those of carbonaceous material. Amorphous carbon does not have energetically well-defined adsorption sites and it can accumulate on other components of SWCNT material blocking the above-mentioned adsorption sites.
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Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

i I i ð3Þ where P, P and I are respectively the spectral position, the spectral position mean value and the intensity of the G band. Fig. 5 shows the weighted mean of the spectral position and its standard devia- tion as a function of DWNTs weight fraction. The weighted mean of the G band position below the percolation threshold displays the highest value while above 0.3 wt% the value is independent of the weight fraction and the standard deviation presents the same behavior. The weighted mean refers the interaction of the outer tube with the polymer. If the G band of the outer tube is up shifted, the DWNTs are in interaction with the polymer matrix. The stan- dard deviation corresponds to the homogeneity of the dispersion. This means when the weighted mean is upshifted and the standard deviation is close to zero, the DWNTs are well dispersed in the poly- mer matrix. This is a simple method to quantify the quality of the dispersion using G band Raman images.
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Amperometric detection of diclofenac at a nano-structured multi-wall carbon nanotubes sensing films

Amperometric detection of diclofenac at a nano-structured multi-wall carbon nanotubes sensing films

7 merits of different electrochemical methods for detection of DCL are summarized in Table 1. The reported method here offers good limit of detection and sensitivity for DCL analysis . It is also a simple approach without complex multi-modification procedures and does not imply the use of differential or transient techniques.

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Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

i I i ð3Þ where P, P and I are respectively the spectral position, the spectral position mean value and the intensity of the G band. Fig. 5 shows the weighted mean of the spectral position and its standard devia- tion as a function of DWNTs weight fraction. The weighted mean of the G band position below the percolation threshold displays the highest value while above 0.3 wt% the value is independent of the weight fraction and the standard deviation presents the same behavior. The weighted mean refers the interaction of the outer tube with the polymer. If the G band of the outer tube is up shifted, the DWNTs are in interaction with the polymer matrix. The stan- dard deviation corresponds to the homogeneity of the dispersion. This means when the weighted mean is upshifted and the standard deviation is close to zero, the DWNTs are well dispersed in the poly- mer matrix. This is a simple method to quantify the quality of the dispersion using G band Raman images.
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Preparation and characterization of α-Fe nanowires located inside double wall carbon nanotubes

Preparation and characterization of α-Fe nanowires located inside double wall carbon nanotubes

2. Experimental DWCNTs, were produced by Catalytic Chemical Vapour Deposi- tion (CCVD) from a H 2 –CH 4 mixture (18 mol% CH 4 , heating and cooling rates 5 °C/min, maximun temperature 1000 °C, no dwell) using oxide (Mg, Co, Mo)O catalysts [9] . The pristine CNTs con- tained ca. 75% DWCNTs, with 1.5 nm average internal diameter and 2.2 nm average external diameter. The CNTs were filled with iron by using a simple method based on the capillary filling with an FeCl 3 solution (adapted from [7] ). To open the CNTs around

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Ultrafast carrier dynamics in single-wall carbon nanotubes

Ultrafast carrier dynamics in single-wall carbon nanotubes

ness of the sample). In this approximation, the transient photo-bleaching of the first interband transition of the semi-conducting tubes can be explained within a simple model. Absorption of the pump pulse creates a popu- lation of electrons in the conduction band and holes in the valence band and until these carriers relax, one ob- serves transient saturation of the line due to filling ef- fects on the final states. In the simplified picture of a two-level system, this saturation should result in a tran- sient broadening of the line. We checked for symmetric energies on the low- and high- energy sides of the peak A that one still observes the same positive change of trans- mission. Moreover the signal amplitude reaches its max- imum at the central energy of the line. We can thus exclude any shift of the line which would on the contrary result in a negative change of transmission on one side of the line. Finally, note that the amplitude of the sig- nal is proportional to the pump power as expected for the photo-created population and that the decay time is independent of the pump fluence as expected in the low perturbation regime. We therefore end up with a first interband transition of the semi-conducting nanotubes modeled by a simple two-level system weakly saturated by the pump beam. The phenomenology is similar for the peak B with a shorter decay time (130 fs) which may be attributed to more efficient relaxation channels within the conduction band. This intraband relaxation time of 130 fs is in agreement with the relaxation times measured in bulk graphite by Seibert et al. [13].
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Determination of moisture content of single-wall carbon nanotubes

Determination of moisture content of single-wall carbon nanotubes

Conclusions Although the materials investigated in this study are not “pure” SWCNT in any definable way, they serve as an excellent model for the variety of samples obtained in production processes. The measurable behavior of their water content is important for their characterization, their use, and perhaps their commercial value. The selective measurement of water based on the KF titration permits its use as a benchmarking methodology for the determination of water content in SWCNT. Possibly due to their residual catalytic metal content, some samples may suffer oxidation reactions which lead to mass gains following initial loss of moisture during oven heating at 105 °C or for prolonged periods of time. Thus, as in the case of some coals and coke, the oven may have to be purged with dry nitrogen to minimize such an effect [ 21 ]. Since not all of the water in the sample may be liberated (detected) if the temperature is not high enough, this conflicting situation suggests that simple oven drying cannot be recommended for processing SWCNT samples. Drying over desiccants such as anhy- drous Mg(ClO 4 ) 2 provides a convenient and inexpensive
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Chirality dependence of coherent phonon amplitudes in single-wall carbon nanotubes

Chirality dependence of coherent phonon amplitudes in single-wall carbon nanotubes

As noted by Sanders et al., 13 only q = 0 phonon modes are coherently excited if the pump laser spot size is large compared with the size of the nanotube. For coherent phonons to be excited, it is necessary for the pump pulse to have a duration shorter than the phonon period (so that the pump pulse power spectrum has a Fourier component at the phonon frequency). In a simple forced oscillator model neglecting oscillation decays, the coherent RBM phonon amplitude Q with frequency ω satisfies a driven oscillator equation, 13

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Carbon-based optoelevtronics on silicon using semiconducting single wall carbon nanotubes

Carbon-based optoelevtronics on silicon using semiconducting single wall carbon nanotubes

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Pressure dependence of raman modes in double wall carbon nanotubes filled with 1D tellurium

Pressure dependence of raman modes in double wall carbon nanotubes filled with 1D tellurium

4. Conclusion In first instance the adopted chemical wetting method was successful and Tellurium entered almost all as trigonal Te in- side DWCNTs giving the opportunity to distinguish pressure- induced spectral changes from internal and external walls in MWCNTs. The splitting of the G band can be explained by considering a tangential discontinuity of the stress compo- nent as one goes from the external wall to the internal one. At normal pressure, in addition to the radial modes of CNTs, we observed the Raman modes of Tellurium confined in CNTs. This confinement modifies the selection rules of the Tellurium phonons in the center of the Brillouin zone. Under pressure, we note that the pressure coefficient of the G bands of the internal and external CNTs filled with trigonal Te are larger than the pressure coefficients of empty CNTs and this has been attributed to the effect of charge transfer of elec- trons from the Tellurium nanowires to the CNTs. Finally, we unravel that the outer tubes act as a protection shield for the inner tubes (at least up to 11 GPa).
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Pressure dependence of Raman modes in double wall carbon
nanotubes filled with α-Fe

Pressure dependence of Raman modes in double wall carbon nanotubes filled with α-Fe

which in the two-dimensional packing hexagonal model [11] could correspond to 40 DWCNTs. In Figure 2(b) there are two rings corresponding to α-Fe, the (110) and the (200). Those rings are non-continuous, indicating that there are preferential orientations of the Fe nanowires. We also indicate reflections (002) due to the DWCNTs (‘nanotube’ in the figure), corresponding to the inter-graphene distance d = 3.37 A of the two graphene layers of the double wall (here also the preferential orientations mentioned above are clear). Figure 3 shows at normal pressure the tangential modes and the D band which corresponds to the double resonance induced by the defects in the CNTs. The high value of the intensity ratio of the tangential external mode and the D band indicates that the crystalline quality of the nanotubes is rather good. Also, the larger intensity of the external mode with respect to the internal one indicates that in this sample the chiralities correspond predominantly to semiconductor nanotubes, with an important concentration of metallic ones, as confirmed by the presence of the band observed around 1508 cm −1 . Table 1 reports the frequency and width of the Raman peaks as extracted from spectra through Lorentzian fit. In the diamond anvil cell the low frequency radial breathing modes and the Raman confined modes of α-Fe nanowires were not observed (50–300 cm −1 range). The tangential optical phonon modes of the CNTs are sensitive to the in-plane stress and split into two contributions associated respectively with the external and internal tube. Figure 4 shows the Raman spectra as a function of applied pressure in the high frequency range obtained using the methanol–ethanol pressure medium. We
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Narrow diameter double-wall carbon nanotubes: synthesis, electron microscopy and inelastic light scattering

Narrow diameter double-wall carbon nanotubes: synthesis, electron microscopy and inelastic light scattering

4. Inelastic light scattering We recorded Raman spectra (DILOR X Y micro-Raman spectrometer) using an argon or krypton ion laser and a photon flux of less than 10 W cm − 2 . The polarization was set parallel to the higher transmission characteristics of the spectrometer. The nanotubes were dispersed on a silicon oxide surface using a diluted solution. To enhance the Raman signal we used a bilayer substrate [ 15 ]. To explore the distribution of the heterogeneous tubes we recorded spectra along a line of the sample every micrometre. Figure 4 shows the composed Raman image which shows the Raman spectra in the radial breathing mode region as a function of the displacement on the sample surface. The Raman image shows the large dispersion of the tube diameter. All the peaks with Raman shifts of more than 220–240 cm − 1
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Optical Absorption and Raman Spectroscopy Study of the Fluorinated Double-Wall Carbon Nanotubes

Optical Absorption and Raman Spectroscopy Study of the Fluorinated Double-Wall Carbon Nanotubes

bromine- and iodine-doped DWNTs using Raman spectroscopy has demon- strated charge transfer from the adsorbed halogen ions onto the outer tube shells (1, 2). Fluorine being the most reactive halogen has been found to attach covalently to carbon nanotube surface (3, 4). Fluorinated single- wall carbon nanotubes (SWNTs) are easyly dissolved in alcohols that allow conducting new reactions for tube functionalization (5). The aim of the present work is investigation of DWNTs reactivity toward a fluori- nating agent BrF 3 . Application of this reagent to the HiPCO-produced
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Sorting and transmission electron microscopy analysis of single or double wall carbon nanotubes

Sorting and transmission electron microscopy analysis of single or double wall carbon nanotubes

CNRS, Universite´ Paul Sabatier, Institut Carnot Cirimat, 31062 Toulouse, France PACS 61.46.Fg, 78.30.Na, 78.40.-q, 81.07.De, 81.20.Ym * Corresponding author: e-mail romain.fleurier@onera.fr , Phone: þ33 1 46 73 45 27, Fax: þ33 1 46 73 41 55 On the basis of the recent progress on the sorting of carbon nanotubes’ structure with respect to their diameter or number of walls, we investigate by transmission electron microscopy the sorting efficiency, with a comparison with optical absorption spectroscopy measurements. We study density gradient ultra- centrifugation sorted single walled or double walled carbon nanotubes, showing obviously the ability to separate carbon nanotubes of different diameters or/and number of walls. This microscopic approach affords accurate information about the
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Elimination of D-band in Raman spectra of double-wall carbon nanotubes by oxidation

Elimination of D-band in Raman spectra of double-wall carbon nanotubes by oxidation

ture and composition. The goal of the work was to select the oxidation conditions leadiig to the removal of amorphous carbon by rnonitosing the intensity of the D b[r]

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Specific surface area of carbon nanotubes and bundles of carbon nanotubes

Specific surface area of carbon nanotubes and bundles of carbon nanotubes

Mg 12x 2 y M M Al O x y 2 4 (M, M95Fe, Co, Ni) solid solu- entirely ruled out that some CNTs are open-ended and tions, it was shown [12,13] that the SSA of carbon is hence that their inner surface area contributes to the 2 maximal (about 350 m / g) when using only cobalt (i.e. experimental value of SSA. However, the increase of SSA y 5 0), and for x 5 0.1. All filaments in that case are due to the opening of some CNTs may be balanced by the bundles of CNTs most of which are SWNTs. decrease of SSA due to the gathering of some of the CNTs

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Carbon Nanotubes Integration on Silicon

Carbon Nanotubes Integration on Silicon

2016 Progress In Electromagnetic Research Symposium (PIERS), Shanghai, China, 8–11 August Carbon Nanotubes Integration on Silicon E. Dur´ an-Valdeiglesias 1 , W. Zhang 1 , H. C. Hoang 1 , C. Alonso-Ramos 1 , S. Serna 1 , X. Le Roux 1 , E. Cassan 1 , L. Vivien 1 , F. Sarti 2 , U. Torrini 2 , M. Gurioli 2 , M. Balestrieri 3 ,

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Polyethylene/carbon nanotubes composites

Polyethylene/carbon nanotubes composites

/ La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. Access and use of [r]

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