ABSTRACTS (Articles)Last update: Jan. 2010
1- Ch. Laurent, E. Flahaut, A. Peigney, A. Rousset
New J. Chem., (1998), 1229-1237
"Metal nanoparticles for the catalytic synthesis of carbon nanotubes"
A review with 116 refs. Single-wall and multiwall carbon nanotubes are currently the subject of an intense research effort owing to the outstanding properties they may possess. Many synthesis methods have been proposed, most of which involve nanometric metal particles. In this article the various mechanisms proposed for nanotube nucleation and growth from such particles have been reviewed. The micro/nanostructure of the materials obtained by the different methods have also been addressed. Discussions include arc-discharge and laser vaporization methods and catalysis methods.
2- A. Govindaraj, E. Flahaut, Ch. Laurent, A. Peigney,
A. Rousset, C. N. R. Rao
J. Mater. Res., (1999), 14, 6, 2567-2576
"An investigation of carbon nanotubes obtained from the decomposition of methane over reduced Mg1-xMxAl2O 4 (M = Fe, Co, Ni) spinel catalysts"
C nanotubes produced by the treatment of Mg1-xMxAl2O4 (M = Fe, Co, or Ni; x = 0.1, 0.2, 0.3, or 0.4) spinels with an H2-CH4 mixt. at 1070° were studied systematically. The grains of the oxide-metal composite particles are uniformly covered by a weblike network of C nanotube bundles, several tens of micrometers long, made up of single-wall nanotubes with a diam. close to 4 nm. Only the smallest metal particles (< 5 nm) are involved in the formation of the nanotubes. A macroscopic characterization method involving surface area measurements and chem. anal. was developed to compare the different nanotube specimens. An increase in the transition metal content of the catalyst yields more C nanotubes (up to a metal content of 10.0% or x = 0.3), but causes a decrease in C quality. The best compromise is to use 6.7% of metal (x = 0.2) in the catalyst. Co gives superior results with respect to both the quantity and quality of the nanotubes. In the case of Fe, the quality is notably hampered by the formation of Fe3C particles.
3- E. Flahaut, A. Govindaraj, A. Peigney, Ch. Laurent,
A. Rousset, C. N. R. Rao
Chem. Phys. Lett., (1999), 300, 1-2, 236-242
"Synthesis of single-walled carbon nanotubes using binary (Fe, Co, Ni) alloy nanoparticles prepared in situ by the reduction of oxide solid solutions"
Passing a H2-CH4 mixt. over oxide spinels contg. two transition elements as in Mg0.8MyM'zAl2O4 (M, M' = Fe, Co or Ni, y + z = 0.2) at 1070° produces small alloy nanoparticles which enable the formation of carbon nanotubes. Surface area measurements are useful for assessing the yield and quality of the nanotubes. Good-quality single-walled nanotubes (SWNTs) were obtained in high yields with the FeCo alloy nanoparticles, as evidenced by transmission electron microscope images and surface area measurements. The diam. of the SWNTs is in the 0.8-5 nm range, and the multiwalled nanotubes, found occasionally, possess very few graphite layers.
4- E. Flahaut, A. Peigney, Ch. Laurent, A. Rousset
J. Mater. Chem., 10, (2000), 249-252
"Synthesis of single-walled carbon nanotube-Co-MgO composite powders and extraction of the nanotubes"
A carbon nanotube-Co-MgO composite powder was prepd. by reducing a Mg0.9Co0.1O solid soln. in H2-CH4 atmosphere. The oxide matrix and part of the Co catalyst are dissolved by acid treatment without damage to the nanotubes. More than 80% of the carbon nanotubes have either one or two walls. The diams. of the nanotubes are in the range 0.5-5 nm. The used method may be a real improvement in the low-cost, large-scale synthesis of single- and double-walled carbon nanotubes.
5- Ch. Laurent, A. Peigney, E. Flahaut, A. Rousset
Mater. Res. Bull., 35, 5, (2000), 661-673
"Synthesis of carbon nanotubes-Fe-Al2O3 powders : influence of the characteristics of the starting Al1.8Fe 0.2 O3 oxide solid solution"
Al1.8Fe0.2O3 amorphous solid soln. were calcined at 1025-1100° and the obtained powders were reduced in a H2-CH4 gas mixt. (12 mol% CH4) at 1050° to prep. carbon nanotubes (CNTs)-Fe/Fe3C-Al2O3 nanocomposite powders. The calcination at 1100° leads to powders contg. an a-Al2-2xFe2xO3 solid soln. (x < 0.1) and some traces of a Fe-rich phase (a-Fe2-2yAl2yO3) that gives, under redn., large Fe particles which catalyze the growth of ribbon like filaments. An a-Al1.8Fe0.2O3 monophased solid soln. with a higher sp. surface area was obtained after a calcination at only 1050 or 1025°. In the corresponding composite powders, all filaments are isolated CNTs or bundles of CNTs and the high specific area is beneficial to both the quantity and the quality parameters which are greatly enhanced in comparison with previous results. About 20% of the obsd. CNTs are single wall nanotubes (SWNTs). The majority of the obsd. multiwall nanotubes (MWNTs) have only two walls and the inner diams. are distributed between 0.8 and 6 nm, with a peak at 2 nm. The in-situ catalysis by selective redn. of a solid soln. allows for prodn. of nanocomposite powders contg. very large quantities of high quality CNTs.
6- A. Peigney, Ch. Laurent, E. Flahaut, A. Rousset
Ceram. Int., 26, 6, (2000), 677-683
"Carbon nanotubes as a part of novel ceramic matrix nanocomposites"
Novel carbon nanotube-metal-ceramic nanocomposite powders and dense materials have been prepd. and their microstructure and mech. properties have been investigated. After a brief review on the structure, synthesis and phys. properties of carbon nanotubes, we describe an original catalytic method that produces ceramic-matrix composite powders that contain in situ grown nanotubes. The synthesis parameters that favor obtaining very high quantities of nanotubes are discussed. The quality of the nanotubes is also addressed. The microstructure and mech. properties of the materials prepd. by hot-pressing of these powders are presented. The influence of carbon nanotubes in such composites is discussed in view of potential applications.
7- E. Flahaut, A. Peigney, Ch. Laurent, Ch. Marlière,
F. Chastel, A. Rousset
Acta Mater., 48, (2000), 3803-3812
"Carbon nanotube-metal-oxide nanocomposites : microstructure, electrical conductivity and mechanical properties"
8- P. Coquay, E. De Grave, R. E. Vandenberghe, C. Dauwe,
E. Flahaut, Ch. Laurent, A. Peigney,
Acta Mater., 48, (2000), 3015-3023
"Mössbauer spectroscopy study of MgAl2O4-matrix nanocomposite powders containing carbon nanotubes and iron-based nanoparticles"
Materials involved in the catalytic formation of carbon nanotubes are for the first time systematically studied by Moessbauer spectroscopy between 11 K and room temp. Mg1-xFexAl2O4 (x=0.1, 0.2, 0.3, 0.4) solid solns. are transformed into carbon nanotubes-Fe/Fe3C-MgAl2O4 composite powders by redn. in a H2-CH4 gas mixt. The oxides are defective spinels of general formulas (Mg1-x2+Fex-3a2+Fe2a3+.box.aAl23+)O42-. Ferromagnetic a-Fe, ferromagnetic Fe3C and a gamma-Fe form, the latter possibly corresponding to a gamma-Fe-C alloy, are detected in the composite powders. An attempt is made to correlate these results with the microstructure of the powder. It seems that the nanoparticles, which catalyze the formation of the carbon nanotubes, are detected as Fe3C in the post-reaction Moessbauer spectroscopy anal.
9 - J. Sloan, M.C. Novotny, S.R. Bailey, G. Brown,
C. Xu, V.C.Williams, S. Friedrichs, E. Flahaut,
R.L. Callendar, A.P.E. York, K.S. Coleman, M.L.H. Green, R.E. Dunin-Borkowski and J.L. Hutchison
Chem. Phys. Lett., 329, (2000), 61-65
"Two layer 4:4 co-ordinated KI crystals grown within single walled carbon nanotubes"
The formation of 'all surface' 4:4 coordinated KI crystals within 1.4 nm diam. single walled C nanotubes (SWNT) is reported. KI was inserted into the SWNTs by a capillary method (Sloan et al., 1999), whereby the nanotubes were combined intimately with the molten halide. The crystals grew with <001> (relative to bulk KI) parallel to the tubule axes and were continuous tetragonally distorted bilayer crystals composed of alternating columns of K-I and I-K pairs when viewed along <100>.
10 - C. Xu, J. Sloan, G. Brown, S. Bailey, V. C. Williams,
S. Friedrichs, K. S. Coleman, E. Flahaut, J. L. Hutchison, R. E. Dunin-Borkowski
and M. L. H. Green
Chem. Commun., 24, (2000), 2427-2428
"1D lanthanide halide crystals inserted into single-walled carbon nanotubes"
1D crystals of lanthanide halides of the form LnCl3 (Ln = La, Nd, Sm, Eu, Gd, Tb or Yb) have been inserted into single-walled carbon nanotubes (SWNTs) using the molten salt capillary filling method. Ca. 20-40% of all the obsd. SWNTs were filled with melts in the range 650-910 °C with no observable damage to the carbon tubules. High resoln. transmission electron microscopy (HRTEM) studies showed that the nanostructures of the encapsulated crystals varied with tubule diam.
11- A. Peigney, Ch. Laurent, E. Flahaut, R. Bacsa,
Carbon, 39, (2000), 507-514
"Geometrical calculations on the specific surface area of carbon nanotubes and bundles of carbon nanotubes"
The theor. external sp. surface area of single- and multi-walled carbon nanotubes and of carbon nanotube bundles is calcd. as a function of their characteristics (diam., no. of walls, no. of nanotubes in a bundle). The results are reported in diagrams and tables useful to correlate the microscopic characteristics and the sp. surface area of samples. The calcd. values are in good agreement with the microscopic characteristics and the sp. surface area measurements which were reported. The sp. surface area is a macroscopic parameter which can be helpful to adjust the synthesis conditions of carbon nanotubes.
12- G. Brown, S. R. Bailey, J. Sloan, C. Xu, S. Friedrichs,
E. Flahaut, K. S. Coleman, J. L. Hutchison, R. E. Dunin-Borkowski, M. L.H.
Chem. Commun., 9, (2001), 845-846
"Electron beam induced in situ clusterisation of 1D ZrCl4 chains within single walled carbon nanotubes"
Cluster formation can be induced in situ in SWNTs filled with ZrCl4 by electron beam irradn. of SWNT/ZrCl4 composites within a field emission gun transmission electron microscope (FEGTEM); the process represents a possible route to the synthesis of 1-dimensional-quantum dot arrays formed by related materials.
13- A. Peigney, P. Coquay, E. Flahaut, E. De Grave,
R. E. Vandenberghe, Ch. Laurent
J. Phys. Chem. B, 105, 40, (2001), 9699-9710
"A study of the formation of single- and double-walled carbon nanotubes by a CVD"
The redn. in H2/CH4 atmosphere of aluminum-iron oxides produces metal particles small enough to catalyze the formation of single-walled carbon nanotubes. Several expts. have been made using the same temp. profile and changing only the max. temp. (800-1070 °C). Characterizations of the catalyst materials are performed using notably 57Fe M.ovrddot.ossbauer spectroscopy. Electron microscopy and a macroscopical method are used to characterize the nanotubes. The nature of the iron species (Fe3+, alpha-Fe, gamma-Fe-C, Fe3C) is correlated to their location in the material. The nature of the particles responsible for the high-temp. formation of the nanotubes is probably an Fe-C alloy which is, however, found as Fe3C by postreaction anal. Increasing the redn. temp. increases the redn. yield and thus favors the formation of surface-metal particles, thus producing more nanotubes. The obtained carbon nanotubes are mostly single-walled and double-walled with an av. diam. close to 2.5 nm. Several formation mechanisms are thought to be active. In particular, it is shown that the second wall can grow inside the first one but that subsequent ones are formed outside. It is also possible that under given exptl. conditions, the smallest (<2 nm) catalyst particles preferentially produce double-walled rather than single-walled carbon nanotubes.
14- S. F. Ji, T. C. Xiao, H. T. Wang, E. Flahaut, K. S. Coleman, M. L. H. Green
Catalysis Lett., 75 (1-2), (2001), 65-71
"Catalytic combustion of methane over cobalt-magnesium oxide solid solution catalysts"
A series of cobalt-magnesium catalyst(CoMgO) have been prepared using urea combustion methods, and characterised by X-ray diffraction(XRD), Laser Raman(LR), and Infrared spectroscopy(IR). The catalytic activities for methane combustion have been tested in a micro-reactor. The Co content has a significant effect on the activity of the cobalt-magnesium oxide solid solution catalyst. The catalysts containing Co5% and Co10% have the lowest light-off temperature in methane combustion. In the preparation of cobalt-magnesium oxide solid solution catalysts, higher urea to metal ratio gives rise to smaller crystal particles and leads to a better catalytic performance. Addition of lanthanum nitrate to the solution of Co and Mg nitrate depressed the formation of the cobalt-magnesium oxide solid solution and decreased the activity of the catalysts for methane combustion. The cobalt-magnesium oxide solid solution catalysts are very stable when the calcination or reaction temperature is no more than 900oC. However, the catalytic activity decreases rapidly after high temperatures( 1000oC) calcinations, possibly due to sintering of the catalyst and thus decrease of the surface area.
15- A. Peigney, E. Flahaut, Ch. Laurent, F. Chastel,
Chem. Phys. Lett., 352, (2002), 20-25
"Aligned carbon nanotubes in ceramic-matrix nanocomposites prepared by high-temperature extrusion"
Carbon nanotube (CNT)-metal-oxide nanocomposites are extruded at high temps. The superplastic forming is made easier by the CNTs. It is possible to align the CNTs in ceramic-matrix nanocomposites, which are bulk materials rather than fibers or thin films. The CNTs withstand the extreme shear stresses occurring during the extrusion. In addn. to electron microscopy revealing the alignment, the materials show an anisotropy of the elec. cond., which could be adjusted by controlling the amt. of CNTs.
16- Flahaut, E.; Agnoli, F.; Sloan, J.; O'Connor, C.;
Green, M. L. H.
Chem. Mater., 14, (2002), 2553-2558
"CCVD Synthesis and Characterization of Cobalt-Encapsulated Nanoparticles"
Cobalt nanoparticles encapsulated in carbon shells were synthesized by catalytic chem. vapor deposition (CCVD) in high yield by reducing with a H2/CH4 gas mixt. a Mg0.9Co0.1O solid soln. impregnated MgO (SSI-MgO) catalyst. The carbon-encapsulated Co nanoparticles have a narrow distribution of diams. within the range 5-15 nm. They are made of (fcc)-Co as shown by x-ray diffraction and are stable to air oxidn.; the magnetic properties were investigated using a SQUID magnetometer and confirm that Co is present in the metallic state.
17- C. Xu, E. Flahaut, S. R. Bailey, G. Brown, J. Sloan,
K. S. Coleman, V. C. Williams, M L. H. Green,
Chemical Research in Chinese Universities, 18(2), (2002) 130-132
"Purification of single-walled carbon nanotubes grown by a chemical vapour deposition (CVD) method"
A procedure for purification of single-walled carbon nanotubes (SWNTs) grown using the chemical vapour deposition (CVD) of carbon monoxide has been developed. Based on the result from TGA/DTA of as-prepared sample, the oxidation temperature was determined. The process included sonication, oxidation and acid washing steps. The purity and yield after purification was estimated both by TEM and Raman spectroscopy.
18- G. Brown, S. R. Bailey, M. Novotny, R. Carter,
E. Flahaut, K. S. Coleman, J. L. Hutchison, M. L. H. Green, J. Sloan
Appl. Phys. A, 76 (4), (2003), 457-462
"High yield incorporation and washing properties of halides incorporated into single walled carbon nanotubes"
We describe here the high yield filling (i.e. >50%) of single walled nanotubes (SWNTs) with a variety of halides, achieved according to various modified filling procedures. Both bundles and discrete SWNTs can be filled continuously up to lengths of several hundred nm, often with filling yields approaching 60-70% or better. In addn. some high yield filled SWNTs were subjected to long-term washing in either boiling or room temp. aq. media, which does not remove the filling from the tubules, but enables effective removal of water-sol. extraneous materials .
19- R. R. bacsa, Ch. Laurent, A. Peigney, T. Vaugien,
E. Flahaut, W. S. Bacsa, A. Rousset
J. Am. Ceram. Soc., 85, 11, (2002), 2666-2669
"(Mg,Co)O solid solutions precursors for the large-scale synthesis of carbon nanotubes by catalytic chemical vapor deposition"
Single- and double-walled carbon nanotubes were produced in high yield using the selective redn. of solid solns. of Mg1-xCoxO in a methane and hydrogen atm. at 1000°. The solid solns. were prepd. using combustion synthesis with urea as the fuel. The BET surface areas was 10-65 m2/g depending on the fuel content. A single cryst. phase was obtained only for fuel-rich compns. Increased fuel content increased the surface area by a factor of 6. However, very high fuel contents (>4 times the stoichiometric amt.) caused a demixed solid soln. Surface-area measurements and Raman spectra showed that the quantity of nanotubes formed depended on the surface area and compn. of the precursor oxide.
20- E. Flahaut, A. Peigney, Ch. Laurent
J. Nanosci. Nanotech., 3, (2003), 151-158
"Double-Walled Carbon Nanotubes in Composite Powders"
Double-walled carbon nanotubes (DWNTs) may be interesting in many applications since the outer wall would provide an interface with the rest of the system. CNT-Fe/Fe3C-Al2O3 composite powders containing CNTs (65% of which are DWNTs) are prepared by reduction of an oxide solid solution in a H2-CH4 gas mixture. The powders and CNTs are studied using both local and macroscopical techniques. The influence of the reducing atmosphere composition and of the dwell time at 1050°C are studied. There is 6-fold increase in CNTs content upon the increase in the CH4 content from 3 to 30 mol.%, but the formation of undesirable carbon nanofibers can also be promoted. A CH4 content of 12-18 mol.% is adapted for the particular iron content in these powders. Increasing the dwell time at 1050°C results in a thickening of the CNTs by addition of walls on pre-existing CNTs.
21- M. Sagnes, J.M. Broto, B. Raquet, T. Ondarcuhu, C. Laurent, E. Flahaut, C. Vieu, F. Carcenac
Microelectronic Engineering, (2003), in press (available on the web)
"Alignment and nano-connections of isolated carbon nanotubes"
We report a new approach for the alignment and the electrical nano-connection of isolated carbon nanotubes (CNTs). Through a novel combination of proven technics, we have been able to align isolated carbon nanotubes and selectively contact those CNTs by high resolution electron beam lithography (HREBL). Resistance versus temperature (R(T)) experiments have been carried out to determine the reliability of the metal–CNTs interface and to probe the electronic conductance of the CNT.
22- J.-F. Colomer, L. Henrard, E. Flahaut, G. Van Tendeloo, A. A. Lucas, Ph. Lambin
Nano Letters, 3 (5), (2003), 685-689
"Rings of double-walled carbon nanotube bundles"
Rings composed of double-walled carbon nanotubes coherently packed in a triangular arrangement are observed and characterized by transmission electron microscopy (TEM) and electron diffraction. Our conclusions are based on the interpretation of the real space images obtained by TEM and on the analysis of selected area electron diffraction patterns with the help of the kinematic theory of diffraction.
23- M. Sagnes, B. Raquet, B. Lassagne, J.M. Broto, E. Flahaut, Ch. Laurent, Th. Ondarçuhu, F. Carcenac, Ch. Vieu
Chem. Phys. Lett, 372, (2003), 733-738
"Probing the electronic properties of individual carbon nanotube in 35 T pulsed magnetic field"
After optimization of the alignment and the nano-contact processes of isolated single wall and double-walls carbon nanotube, we investigate the high magnetic field effects on the electronic transport properties of an individual metallic CNT. We develop pioneer multi-probes magneto-transport expts. under a 35 T pulsed field which reveal an unexpected oscillatory behavior of R(H) inconsistent with existing theories.
24- E. Flahaut, R. Bacsa, A. Peigney and Ch. Laurent
Chem. Commun., (2003), 1442-1443
"Gram-Scale CCVD Synthesis of Double-Walled Carbon Nanotubes"
Synthesis of clean double-walled carbon nanotubes by a Catalytic Chemical Vapour Deposition method is reported; the catalyst is a Mg1-xCoxO solid solution containing additions of Mo oxide: this MgO-based catalyst can be easily removed, leading to gram-scale amounts of clean carbon nanotubes, 77% of which are double-walled carbon nanotubes.
25- R. Bacsa, E. Flahaut, Ch. Laurent, A. Peigney, S. Aloni, P. Puech, W.S. Bacsa
New J. Phys, 5, (2003) 131.1–131.9 (published on the web)
"Narrow diameter double-wall carbon nanotubes: synthesis, electron microscopy and inelastic light scattering"
Double-wall carbon nanotubes are themolecular analogues to coaxial cables. Narrow diameter double-walled carbon nanotubes (DWNTs) have been obtained by catalytic chemical vapour deposition process with high yield and characterized by scanning and transmission electron microscopy. We examine the inelastic light scattering spectrum of mostly DWNTs with internal tubes of subnanometre diameter. We observe particularly narrow radial breathing modes corresponding to the internal tubes of diameter less than 0.7 nm of double-walled tubes. The D band is found to be strongly helicity dependent and the tangential modes in narrow diameter DWNTs are found to be often down-shifted.
26- E. Flahaut, A. Peigney, W. S. Bacsa, R. R. Bacsa and Ch. Laurent
J. Mater. Chem., invited paper, submitted
"CCVD synthesis of carbon nanotubes from (Mg, Co, Mo)O catalysts: Influence of the proportions of cobalt and molybdenum."
Carbon nanotubes have been synthesised by catalytic chemical vapour deposition of a H2–CH4 mixture (18 mol% CH4) over (Mg,Co,Mo)O catalysts. The total amount of cobalt and molybdenum has been kept constant at 1 cat% and the proportion of molybdenum with respect to cobalt has been varied from x(Mo) = 0.25–1.0. This variation has important effects on both the yield and the nature (number of walls, straight walls or bamboo-like structures) of the carbon nanotubes. It also has an influence on the purity of the samples (amount of encapsulated metal particles, presence or not of amorphous carbon deposits). For x = 0.25, the nanotubes were mainly double- and triple-walled (inner diameter less than 3 nm); samples prepared from catalysts with higher molybdenum ratios contained larger multi-walled carbon nanotubes (inner diameter up to 9 nm), having up to 13 concentric walls. It is proposed that different growth mechanisms may occur depending on the initial composition of the catalyst.
27- S. Casimirius, E. Flahaut, Ch. Laurent, Ch. Vieu, F. Carcenac, Ch. Laberty- Robert
Microelectronic Engineering, 73-74, (2004), 564-569
"Optimized microcontact printing process for the patterned growth of individual SWNTs"
We report an original approach to pattern a substrate with isolated carbon nanotubes. Through the improvement of the microcontact printing technique by the use of a new composite stamp, we were able to produce on flat substrates micrometric features of a catalyst suitable for the localised growth of single-walled carbon nanotubes by catalytic chem. vapor deposition. This catalyst material is for the first time prepd. via an original sol-gel process. The growth of straight carbon nanotubes between the patterns was obsd. and a method to promote the controlled growth of such isolated nanoobjects is thus conceivable.
28- M. Sagnes, J-M. Broto, B. Raquet, C.Vieu, V. Conedera, P. Dubreuil, T. Ondarçuhu, Ch. Laurent, E Flahaut
Microelectronic Engineering, 73-74 (2004), 689-694
"Nanodevices for electrical transport and structural cross investigation on individual carbon nanotubes"
We report a new approach to the correlation of the structural properties and the transport properties of carbon nanotubes. Through an original combination of UV lithog., custom-made photosensitive sol-gel resist and deep reactive ion etching (RIE), we have successfully integrated membrane technol. and nanodevice fabrication for the elec. connection of individual carbon nanotubes. After single wall nanotube (SWNT) deposition by mol. combing and contacting using high resoln. electron beam lithog., we obtain a device that allows both the investigation of the nanotubes and the contact regions by transmission electron microscopy (TEM) and the measurement of the electronic transport properties of the same individual nano-object. The whole fabrication process is detailed and the demonstration that the micro membranes are suitable for both TEM inspection and nanoelectrode fabrication is given.
29- J. Cambedouzou, J. L. Sauvajol, A. Rahmani, E. Flahaut, A. Peigney, C. Laurent
Phys. Rev. B., 69, (2004), 135422:1-6
"Raman spectroscopy of iodine-doped double-walled carbon nanotubes"
We present a Raman spectroscopy study of iodine-intercalated (p-type-doped) double-walled carbon nanotubes. Double-walled carbon nanotubes (DWCNTs) are synthesized by catalytic chem. vapor deposition and characterized by Raman spectroscopy. The assignment of the radial breathing modes and the tangential modes of pristine DWCNTs is done in the framework of the bond polarization theory, using the spectral moment method. The changes in the Raman spectrum upon iodine doping are analyzed. Poly-iodine anions are identified, and the Raman spectra reveal that the charge transfer between iodine and DWCNTs only involves the outer tubes.
30- C. Portet, P. L. Taberna, P. Simon, E. Flahaut
J. Power. Sources (2004), in press
"Influence of carbon nanotubes addition on carbon-carbon supercapacitor performances in organic electrolyte"
This paper presents the performances of 4 cm2 supercapacitors cells assembled with 200 micron thick active material films composed with activated carbon and carbon nanotubes mixture in organic electrolyte. Galvanostatic and electrochemical spectroscopy impedance measurements have been carried out. Galvanostatic measurements show that both internal resistance and specific capacitance decrease when the carbon nanotubes content increases in the active material.With 15% of carbon nanotubes, the internal resistance is 0.65 Ohm.cm2 and the specific capacitance is 90 F/g measured at 20mA/cm2. This performances remain stable during 10,000 cycles. The characterization of the frequency behavior was made by Electrochemical Impedance Spectroscopy. For 15% of CNTs content in the active material, the relaxation time (phi = -45°) is divided by 3 as compared to a supercapacitor using pure activated carbon electrodes.
31- E. Flahaut, Ch. Laurent, A. Peigney
Carbon, 43, (2005), 375-383
"Catalytic CVD Synthesis of Double and Triple-walled Carbon Nanotubes by the Control of the Catalyst Preparation"
We report the influence of catalyst preparation conditions for the synthesis of carbon nanotubes (CNTs) by catalytic chemical vapour deposition (CCVD). Catalysts were prepared by the combustion route using either urea or citric acid as the fuel. We found that the milder combustion conditions obtained in the case of citric acid can either limit the formation of carbon nanofibres (defined as carbon structures not composed of perfectly co-axial walls or only partially tubular) or increase the selectivity of the CCVD synthesis towards CNTs with fewer walls, depending on the catalyst composition. It is thus for example possible in the same CCVD conditions to prepare (with a catalyst of identical chemical composition) either a sample containing more than 90% double- and triple-walled CNTs, or a sample containing almost 80% double-walled CNTs.
32- P. Puech, H. Hubel, D.J. Dunstan, A. Bassil, R. Bacsa, A. Peigney, E. Flahaut, C. Laurent, W.S. Bacsa
Phys. Stat. Sol. B, 241, 14, (2004), 3360-3366
"Light scattering of double wall carbon nanotubes under hydrostatic pressure: pressure effects on the internal and external tubes"
We report high-pressure Raman light scattering studies up to 10 GPa on double walled carbon nanotubes using two pressure transmitting media. In alcohol, a clear splitting of the G band is observed up to 10 GPa. This splitting is evidence for both discontinuous tangential stress and continuous radial stress. A structural distortion seems to be present at 3 GPa, revealed by a spectroscopic signature at 1480 cm(-1). With argon as the pressure transmitting medium, the nanotubes bundles show a transition at 6 GPa which corresponds to a collapse to a flattened structure and removes the splitting. The comparison of the pressure coefficients before the transition for the two pressure transmitting media shows that the ratio of the two coefficients associated with internal and external tubes, is the same but the absolute values are different.
33- A. Bassil, P. Puech, G. Landa, W. Bacsa, S. Barrau, Ph. Demont, C. Lacabanne, E. Perez, R. Bacsa, E. Flahaut, A. Peigney, Ch. Laurent
J. Appl. Phys., 97, (2005), 034303
"Spectroscopic detection of carbon nanotube interaction with amphiphilic molecules in epoxy resin composites"
Incorporation of carbon nanotubes into epoxy resin composites has the effect of increasing electrical conductivity at low percolation levels. An amphiphilic molecule such as palmitic acid has been used to increase the surface contact area and to improve the dispersion of the carbon nanotube bundles in the prepolymer. The chemical environment of the dispersed nanotubes has been probed using vibrational Raman spectroscopy. Spectroscopic Raman maps on sample surfaces (60×60 µm2) with ratios of nanotubes to palmitic acid varying from 1:2 to 2:1 by weight, have been recorded to test the uniformity of the dispersion. Substantial spatial inhomogeneities have been observed in the G-band shift and an additional spectral band at 1450 cm–1. The 1450 cm–1 band has been attributed to the CH3 group of the amphiphilic molecules adsorbed onto the nanotube surface. The maps are correlated with the measured electrical conductivity values. The highest conductivity has been observed for the best dispersed nanotubes and nanotubes with the highest degree of interaction.
34- S. Osswald, E.l Flahaut, H. Ye, Y. Gogotsi
Chem. Phys. Lett., 402, (2005), 422-427
"Elimination of D-Band in Raman Spectra of Double-Wall Carbon Nanotubes by Oxidation"
In this Letter, we present an in situ Raman spectroscopy study of oxidation-induced changes in the structure and composition of double-wall carbon nanotubes (DWNTs). Above 480 °C, the intensity of the D band decreases to less than 0.01% of the G band intensity, when measured using the 780 nm laser excitation. The D band was absent from the Raman spectra recorded with the 514.5 nm excitation. Thermogravimetric analysis and high-resolution transmission electron microscopy are used to explain the observed results. We conclude that oxidation provides a purification method for the DWNTs which leads to a sample containing tubes having nearly clean surfaces without disordered carbon.
35- G. Fedorov, B. Lassagne, M. Sagnes, B. Raquet, J.M. Broto, F. Triozon, S. Roche, E. Flahaut
Phys. Rev. Lett., 97, (2005), 066801
"Gate dependant magnetoresistance phenomena in carbon nanotubes"
We report on the first experimental study of the magnetoresistance of double-walled carbon nanotubes under a magnetic field as large as 50 T. By varying the field orientation with respect to the tube axis, or by gate-mediated shifting the Fermi level position, evidence for unconventional magnetoresistance is presented and interpreted by means of theoretical calculations.
36- V. Datsyuk, C. Guerret-Piécourt, S. Dagréou, L. Billon, J.C. Dupin, E. Flahaut, A. Peigney, Ch. Laurent
Carbon, 43(4), (2005) 873-876
"Double walled carbon nanotube/polymer composites via in-situ nitroxide mediated polymerisation of amphiphilic block copolymers"
For the first time double walled carbon nanotube/polymer composites were synthesized by in-situ nitroxide mediated polymn. The block copolymer synthesis method allows elaborating well-dispersed carbon nanotubes (CNT) in various polymer matrixes, as the first block is strongly interacting with CNT surface. Such composites could also be used as compatibilizer to improve the dispersion of CNT in different industrially produced polymer matrixes.
37- T. Hertel, A. Hagen, V. Talalaev, K. Arnold, F. Hennrich, M. Kappes, S. Rosenthal, Ja. McBride, H. Ulbricht, E. Flahaut
Nano Letters, 5, (3), (2005), 511-514
"Spectroscopy of Single- and Double-Wall Carbon Nanotubes in Different Environments"
Individual single-wall carbon nanotubes (SWNTs) and double-wall carbon nanotubes (DWNTs) were suspended in water for optical studies using sodium-cholate and other surfactants. We used time-resolved photoluminescence (PL) spectroscopy to study the influence of tube chirality and diam. as well as of the environment on nonradiative decay in small diam. tubes. The studies provide evidence for PL from small diam. core tubes in DWNTs and for a correlation of nonradiative decay with tube diam. and exciton red shift as induced by interaction with the environment.
38- C. Salvador-Morales, E. Flahaut, E Sim, J. Sloan, M.L.H.Green, R. B. Sim
Molec. Immun., 43, (3), (2006), 193-201 (DOI:10.1016/j.molimm.2005.02.006)
"Complement activation and protein adsorption by carbon nanotubes"
As a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways.Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques were used to elucidate the mechanism of activation of complement via the classical pathway, and to analyse the interaction of complement and other plasma proteins with carbon nanotubes.We report for the first time that carbon nanotubes activate human complement via both classical and alternative pathways. We conclude that complement activation by nanotubes is consistent with reported adjuvant effects, and might also in various circumstances promote damaging effects of excessive complement activation, such as inflammation and granuloma formation. C1q binds directly to carbon nanotubes. Protein binding to carbon nanotubes is highly selective, since out of the many different proteins in plasma, very few bind to the carbon nanotubes. Fibrinogen and apolipoproteins (AI, AIV and CIII) were the proteins that bound to carbon nanotubes in greatest quantity.
39- C. Portet, P.L. Taberna, P. Simon, E. Flahaut, C. Laberty-Robert
Electrochimica Acta, 50, (2005), 4174-4181
"High power density electrodes for Carbon supercapacitor applications"
This paper presents results obtained with 4 cm2 Carbon/Carbon supercapacitors cells in organic electrolyte. In the first approach, a surface treatment for Al current collector foil via the sol–gel route has been used in order to decrease the Al/active material interface resistance. Performances obtained with this original process are: a low equivalent series resistance (ESR) of 0.5 Ohm.cm2 and a specific capacitance of 95Fg-1 of activated carbon. Then, supercapacitors assembled with treated Al foil and active material containing activated carbon/carbon nanotubes (CNTs) with different compositions have been studied. Galvanostatic cycling measurements show that when CNTs content increases, both ESR and specific capacitance are decreased. Fifteen percent appears to be a good compromise between stored energy and delivered power with an ESR of 0.4 Ohm.cm2 and a specific capacitance of 93 F g-1 of carbonaceous active material. Finally, cells frequency behaviour has been characterized by Electrochemical Impedance Spectroscopy. The relaxation time constant of cells decreases when the CNTs content increases. For 15% of CNTs, the time constant is about 30% lower as compared to a cell using pure activated carbon-based electrodes leading to a higher delivered power.
40- E. Flahaut, M.C. Durrieu, M. Remy-Zholgadri, R. Bareille, Ch. Baquey
J. Mater. Sci, Accepted
"Study of the Cytotoxicity of CCVD Carbon Nanotubes"
The cytotoxicity of different samples of carbon nanotubes synthesised by catalytic chemical vapour deposition was investigated towards human umbilical vein endothelial cells, using two cytotoxicity standard tests (neutral red assay for the cell viability and MTT assay - tetrazolinium salt - for the cell metabolic activity). No toxicity was found for any sample, although a slight dilution effect may exist for two of them.
41- A. Cordier, E. Flahaut, C. Viazzi, Ch. Laurent, A. Peigney
J. Mater. Chem., 15, (2005), 4041-4050
"In-situ CCVD synthesis of carbon nanotubes within a commercial ceramic foam"
Consolidated nanocomposite foams containing a large quantity of carbon nanotubes (CNTs) within millimetre-sized pores are prepared for the first time. A commercial ceramic foam is impregnated by a 60 g/L slurry of a (Mg(1-x)(Co0.75Mo0.25)xO solid solution (x = 0.01, 0.05, 0.1 and 0.2) powder in ethanol. Three successive impregnations led to deposits several tens of mm thick, with a good coverage of the commercial-ceramic pore walls but without closing the pores. The materials were submitted to a CCVD treatment in H2–CH4 atmosphere in order to synthesise the CNTs. When using attrition-milled powders, the carbon is mostly in the form of nanofibres or disordered carbon rather than CNTs. Using non-milled powders produces a less-compact deposit of catalytic material with a higher adherence to the walls of the ceramic foam. After CCVD, the carbon is mostly in the form of high-quality CNTs, as when using powder beds, their quantity being 2.5 times higher. The so-obtained consolidated nanocomposite materials show a multi-scale pore structuration.
42- P. Coquay, A. Peigney, E. De Grave, E. Flahaut, R. E. Vandenberghe, Ch. Laurent
J. Phys. Chem. B, 109, (38), (2005), 17813-17824 (DOI: 10.1021/jp0524936)
"Fe/Co alloys for the CCVD synthesis of single- and double-walled carbon nanotubes - Part I: the CNT-Fe/Co-MgO system"
Mg0.90FexCoyO (x + y ) 0.1) solid solutions were synthesized by the ureic combustion route. Upon reduction at 1000 °C in H2-CH4 of these powders, Fe/Co alloy nanoparticles are formed, which are involved in the formation of carbon nanotubes, which are mostly single and double walled, with an average diameter close to 2.5 nm. Characterizations of the materials are performed using 57Fe Mössbauer spectroscopy and electron microscopy, and a well-established macroscopic method, based on specific-surface-area measurements, was applied to quantify the carbon quality and the nanotubes quantity. A detailed investigation of the Fe/Co alloys’ formation and composition is reported. An increasing fraction of Co2+ ions hinders the dissolution of iron in the MgO lattice and favors the formation of MgFe2O4-like particles in the oxide powders. Upon reduction, these particles form R-Fe/Co particles with a size and composition (close to Fe0.50Co0.50) adequate for the increased production of carbon nanotubes. However, larger particles are also produced resulting in the formation of undesirable carbon species. The highest CNT quantity and carbon quality are eventually obtained upon reduction of the iron-free Mg0.90Co0.10O solid solution, in the absence of clusters of metal ions in the starting material.
43- P. Coquay, E. Flahaut, E. De Grave, A. Peigney, R. E. Vandenberghe, Ch. Laurent
J. Phys. Chem. B, 109, (38), (2005), 17825-17830 (DOI: 10.1021/jp052494y)
"Fe/Co alloys for the CCVD synthesis of single- and double-walled carbon nanotubes - Part II: theCNT-Fe/Co-MgAl2O4 system"
A detailed 57Fe Mössbauer study of the Mg0.8Fe0.2-yCoyAl2O4 (y ) 0, 0.05, 0.1, 0.15, 0.2) solid solutions and of the CNT-Fe/Co-MgAl2O4 nanocomposite powders prepared by reduction in H2-CH4 has allowed characterization of the different iron phases involved in the catalytic process of carbon nanotube (CNT) formation and to correlate these results with the carbon and CNT contents. The oxide precursors consist of defective spinels of general formulas (Mg1-x-y2+Fex-3alpha2+Fe2alpha3+Vac alpha Coy2+Al23+)O42- . The metallic phase in the CNT-Fe/Co-MgAl2O4 nanocomposite powders is mostly in the form of the ferromagnetic alpha-Fe/Co alloy with the desired composition. For high iron initial proportions, the additional formation of Fe3C and gamma-Fe-C is observed while for high cobalt initial proportions, the additional formation of a gamma-Fe/Co-C phase is favored. The higher yield of CNTs is observed for postreaction alpha-Fe0.50Co0.50 catalytic particles, which form no carbide and have a narrow size distribution. Alloying is beneficial for this system with respect to the formation of CNTs.
44- A. Albina, P.L. Taberna, J.P. Cambronne, P. Simon, E. Flahaut, T. Lebey
Microelectronics Journal, Accepted
"Impact of the surface roughness on the electrical capacitance"
A new hybrid approach consists to use the advantages of both systems namely the high geometric aspects of the electrodes of the ultracapacitor and the high dielectric strength of polymer materials used in dielectric capacitors. The surface roughness of the electrodes of the ultracapacitor is manufactured with nano-porous materials; activated carbon and carbon nanotubes (CNTs). Many compositions of both carbonaceous materials are tested with different insulating materials (liquid and solid) to constitute the hybrid capacitor. It appears that the capacitance increases with the carbonaceous composition: An increasing from 15% to 40% is observed as compared to a plane capacitor, it can be twice with a 100wt % of CNTs content. But, the impregnation of the insulating material in the surface roughness remains the key point of the realization of the hybrid capacitor. The roughness accessibility is a major property to optimize in order to improve the impregnation of the insulating material to increase the electrical capacitance.
45- P. Puech, A. Bassil, J. Gonzalez, Ch. Power, E. Flahaut, S. Barrau, Ph. Demont, C. Lacabanne, E. Perez, W. S. Bacsa
Phys. Rev. B, 72, (2005), 155436
"Similarities in the Raman RBM and D bands in double-wall carbon nanotubes"
We examine the Raman spectrum of double wall carbon nanotubes with a broad size distribution in agglomerated form and partially filled with PbI2. Using spectroscopic mapping we find a statistical correlation between the radial breathing mode (RBM) and D band intensity. All the investigated samples show the same correlation using the 514 nm laser excitation. We derive the phonon deformation potential for the D band and extend the dispersion of the D band to the UV. We find that the intensity of the D band decreases with increasing pressure and vanishes at a pressure comparable to what has been observed earlier for the RBM and D* band.
46- M. Sendova, E. Flahaut, B. DeBono
J. Appl. Phys., 98, (2005), 104304
"Raman spectroscopy of PbI2-filled double-walled carbon nanotubes"
PbI2-filled double-walled carbon nanotubes (PbI2@DWCNT) have been studied by Raman spectroscopy employing 785 nm excitation wavelength and their spectra have been compared to those of pristine DWCNT. The DWCNTs were synthesized by catalytic chemical vapor deposition. Assignment of the radial breathing modes and the tangential modes was done based on the 1D electronic energy band structure of carbon nanotubes. It was established that PbI2@DWCNT can be unambiguously identified by the position of the second order G'-band and its rate of downshift due to power density increase of the excitation radiation. After laser assisted disintegration of the PbI2@DWCNT the PbI2 band has been detected and compared to those of the powder PbI2. The one dimensional PbI2 crystal chains show downshifted bands as compared to those of the powder material.
47- E.Flahaut, M.C. Durrieu, M. Remy-Zholgadri, R. Bareille, Ch. Baquey
"Investigation of the cytotoxicity of CCVD carbon nanotubes towards human umbilical vein endothelial cells"
The cytotoxicity of different samples of carbon nanotubes synthesised by catalytic chemical vapour deposition was investigated towards human umbilical vein endothelial cells, using two cytotoxicity standard assays (neutral red assay for the cell viability and MTT assay - tetrazolinium salt - for the cell metabolic activity). No cytotoxicity was found for any sample.
48- A. Cordier, A. Peigney, E. De Grave, E. Flahaut, Ch. Laurent
J. Eur. Ceram. Soc.,(2005), 26, (2006), 3099-3111
"Synthesis of the metastable alpha-Al1.8Fe0.2O3 solid solution from precursors prepared by combustion"
Consolidated nanocomposite foams contg. a large quantity of carbon nanotubes (CNTs) within millimeter-sized pores are prepd. for the first time. A com. ceramic foam is impregnated by a 60 g.L-1 slurry of a Mg(1-x)(Co0.75Mo0.25)xO solid soln. (x = 0.01, 0.05, 0.1 and 0.2) powder in ethanol. Three successive impregnations led to deposits several tens of microns thick, with a good coverage of the com.-ceramic pore walls but without closing the pores. The materials were submitted to a CCVD treatment in H2-CH4 atmosphere to synthesize the CNTs. When using attrition-milled powders, the carbon is mostly in the form of nanofibers or disordered carbon rather than CNTs. Using non-milled powders produces a less-compact deposit of catalytic material with a higher adherence to the walls of the ceramic foam. After CCVD, the carbon is mostly in the form of high-quality CNTs, as when using powder beds, their quantity being 2.5 times higher. The so-obtained consolidated nanocomposite materials show a multi-scale pore structuration.
49- E. Flahaut, J. Sloan, S. Friedrichs, A.I. Kirkland, K.S. Coleman, V.C. Williams, N. Hanson, J.L. Hutchison, M.L.H. Green
Chemistry of Materials, available online
"Crystallization of 2H and 4H PbI2 in carbon nanotubes of varying diameters and morphologies"
The crystallization of the complex halide PbI2 in discrete and bundled single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs) and thicker walled nanotubes is described. The nanotubes were produced either by arc synthesis or by catalytic chemical vapor deposition. The obtained crystals can be described in terms of 1D fragments derived principally from the 2H form of PbI2 although some evidence for the formation of fragments derived from 4H PbI2 in some nanotubes was observed. The crystallization inside nanotubes was compared to the crystallization behavior of bulk PbI2 as determined by X-ray powder diffraction measurements obtained under comparable heating conditions. While the 2H to 4H polytype transition is clearly observable in bulk PbI2, stacking behavior correlated with this type of polytypism was only very occasionally observed within nanotubes suggesting that crystallizing PbI2 within nanotubes has a tendency to order the halide into the 2H form. Additionally, PbI2 apparently does not crystallize in rigid narrow DWNTs with internal diameters of less than 2 nm. Raman studies performed on the PbI2 filled nanotubes show that the ratio of intensity of the D and G bands generally increases after filling and that both the RBM peaks and the G band are slightly up-shifted.
50- S. Osswald, E. Flahaut, Y. Gogotsi
Chemistry of Materials, 18, (6), (2006), 1525-1533
"In Situ Raman spectroscopy study of oxidation of double- and single-wall carbon nanotubes"
In situ Raman spectroscopy allows for a detailed and time-resolved study of the kinetics of complex phys. or chem. processes. Oxidn. has become a frequently used method for the removal of disordered C species from C nanotubes. Oxidn., however, can also induce damage to the tubes and destroy most of the sample. The authors conducted an in situ Raman spectroscopy study of the oxidn. of double- and single-walled C nanotubes (DWCNT and SWCNT) under isothermal and nonisothermal conditions to identify the temp. range in which the oxidn. of amorphous C occurs without any changes with respect to the tubes and their structure. In situ Raman spectroscopy anal. of the oxidn. of DWCNTs showed a decrease in the intensity of the D band starting around 370°, followed by complete D band elimination at 440°. Oxidn. studies of SWCNTs showed a similar decrease in the D band intensity, but the D band was not completely eliminated. Also, in situ measurements allow one to det. the different contributions to the D band feature and show the relation between the D band, G band, and RBM Raman modes in the Raman spectra of DWCNT upon heating. Isothermal oxidn. provides an efficient purifn. method for DWCNTs and SWCNTs, which is also selective to tube diam. After oxidn., tubes show clean surfaces without disordered or amorphous C impurities.
51- C. Portet, P. L. Taberna, P. Simon, E. Flahaut
Journal of The Electrochemical Society, 153, (4), (2006), A649-A653
"Modification of Al Current Collector/Active Material Interface for Power Improvement of Electrochemical capacitor Electrodes"
This paper presents results about carbon nanofibers (CNFs) synthesis and their use as surface treatments for Al current collector for carbon electrochemical capacitors in organic electrolyte. CNFs have been successfully synthesized on a pretreated Al substrate; the pretreatment of Al consists of an etching followed by a carbonaceous sol-gel deposit. Performances of cells assembled with pretreated Al and pretreated Al coated by CNFs have been compared by using galvanostatic cycling measurements. Internal resistances as low as 0.4 Ohm.cm2 are obtained for cells using CNF-treated Al. The increase of the surface contact and interface conductivity between the Al and the active material are responsible for this internal resistance decrease. The capacitance obtained for the two cells is the same (95 F/g of activated carbon). Performances [both equivalent series resistance (ESR) and capacitance] are stable over 10 000 cycles, proving the great efficiency of surface treatments.
52- M. Dragoman, K. Grenier, D. Dubuc, L. Bary, E. Fourn, R.
Plana, E. Flahaut
Appl. Phys. Lett., 88, (2006), 173113:1-3
"Controlled laser heating of carbon nanotubes"
We investigate laser heating of double wall carbon nanotubes deposited on surfaces and immerged in liquids as a function of laser wavelength. Observing the Raman spectrum we find that laser heating of agglomerated double wall carbon nanotubes is six times larger at 488 nm than at 647 nm. The wavelength dependence of the Raman G band is linear in the visible spectral range. The frequency shift of the Raman G band obtained in methanol as a function of temperature is close to what is observed for graphite.
53- A. Bassil,P. Puech, L. Tubery, W. Bacsa, E. Flahaut
Appl. Phys. Lett., 88, (2006), 153108:1-3
"Experimental determination of microwave attenuation and electrical permittivity of double-walled carbon nanotubes"
The attenuation and the electrical permittivity of the double-walled carbon nanotubes (DWCNTs) were determined in the frequency range of 1–65 GHz. A micromachined coplanar waveguide transmission line supported on a Si membrane with a thickness of 1.4 micrometers was filled with a mixture of DWCNTs. The propagation constants were then determined from the S parameter measurements. The DWCNTs mixture behaves like a dielectric in the range of 1–65 GHz with moderate losses and an abrupt change of the effective permittivity that is very useful for gas sensor detection.
54- T. Michel, L. Alvarez, J.L. Sauvajol, R. Almairac, R. Aznar, O. Mathon, J.L. Bantignies, E. Flahaut
J. Phys. Chem. Sol., 67, (2006), 1190-1192
"Structural selective charge transfer in iodine-doped carbon nanotubes"
We have investigated iodine intercalated carbon nanostructures by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. We discuss here the charge transfer and the iodine-carbon interaction as a function of the carbon nanostructures (graphite, multi-walled, double-walled and single walled nanotubes). The results show that iodine is weakly adsorbed on the surface of all multi-walled nanotubes. By contrast, a charge transfer between iodine and single walled nanotubes is evidenced.
55- P. Puech, E. Flahaut, A. Sapelkin, H. Hubel, D.J. Dunstan, G. Landa, W.S. Bacsa
Phys. Rev. B, 73, (23), (2006), 233408:1-4
"Nanoscale pressure effects in individual double-wall carbon nanotubes"
We use the signal from the internal tubes of double-wall carbon nanotubes as an ideal pressure ref. The intensity assocd. with the G band of the external tubes is shown to be related to the interaction of the pressure medium and the carbon nanotube. We observe clear pressure medium dependent pressure coeffs. of the Raman G band using at. argon, oxygen, and alc. The G band of the internal tubes shifts between 5.1 and 3.3 cm-1/GPa and for the external tubes between 5.8 and 8.6 cm-1/GPa for the different pressure media used. We find that the spectral shape of the optical phonon band depends clearly on the pressure medium. Ab initio calcns. support local partial ordering and shell formation of the pressure medium around the nanotube. The shell formation around the tube has a strong impact on the local pressure transmission.
56- P. N. Gevko, L. G. Bulusheva, A. V. Okotrub, N. F. Yudanov, I. V. Yushina, K. A. Grachev, A. M. Pugachev, N. V. Surovtsev,E. Flahaut
Fullerenes, Nanotubes, and Carbon Nanostructures, 14, (2-3), (2006), 233-238
"Optical absorption and Raman spectroscopy study of the fluorinated double-wall carbon nanotubes"
Double-wall carbon nanotube (DWNT) samples have been fluorinated at room temp. with varied concn. of a fluorinating agent BrF3. Content of the products estd. from X-ray photoelectron data was equal to CF0.20 and CF0.29 in the case of deficit and excess of BrF3. Raman spectroscopy showed considerable decrease of carbon nanotube amt. in the fluorinated samples. Anal. of optical absorption spectra measured for pristine and fluorinated DWNT samples revealed a selectivity of carbon nanotube fluorination. Nanotubes with large chiral angle are more inert to the fluorinating agent used.
57- L.G. Bulusheva, P.N. Gevko, A.V. Okotrub, Yu.V. Lavskaya, N.F. Yudanov, L.I. Yudanova, O.G. Abrosimov, E.M. Pazhetnov, A.I. Boronin, E. Flahaut
Chem. Mater, 18, (20), (2006), 4967 - 4971
"Thermal behavior of the fluorinated double-walled carbon nanotubes"
Double-walled carbon nanotubes (DWNTs), produced by a catalytic chem. vapor deposition method, have been fluorinated using a volatile mixt. of BrF3 and Br2. Optical absorption spectroscopic study on the product detected nonfluorinated nanotubes, which could correspond to the inner walls of DWNTs. The fluorinated DWNTs have been annealed in vacuum at fixed temps., and XPS showed almost no fluorine in the sample heated to 300 °C. Comparison between X-ray fluorescent C K spectra of the pristine DWNT sample and the annealed fluorinated sample revealed change of the at. structure of graphitic shells in the process of thermal defluorination.
58- J.L. Bantigines, P. Hermet, J. Cambedouzou, L. Alvarez, J. L. Sauvajol, A. Rahmani, E. Flahaut
Phys. Rev. B., (2006), accepted
"Infrared-active phonons in carbon nanotubes"
59- M. Dragoman, A. Muller, D. Neculoiu, D. Vasilache, G. Konstantinidis, K.Grenier, D.Dubuc,
L. Bary, R. Plana, E. Flahaut
Appl. Phys. Lett., 89, (2006), 143122:1-3
"High performance thin film bulk acoustic resonator covered with carbon nanotubes"
This letter presents experimental results concerning a thin film bulk acoustic wave resonator realized on a thin GaN membrane and covered with a thin film of double walled carbon nanotube mixt. The quality factor was measured before and after the coating of the resonator with the nanotube thin film. The quality factor has increased more than ten times when the resonator was coated with nanotubes, due to their high elasticity modulus and low d., which confers a much higher acoustic impedance of the resonator electrodes and thus confines much better the longitudinal acoustic standing waves inside the resonator.
60- C. Salvador-Morales, P. Townsend, E. Flahaut, C. Vénien-Bryan, A. Vlandas, M.L.H. Green,
R. B. Sim
Carbon, 45, (2007), 607-617
"Binding of pulmonary surfactant proteins to carbon nanotubes; potential for damage to lung immune defense mechanisms"
Potential pulmonary toxicity of carbon nanotubes is a research area that has received considerable attention. Surfactant proteins A and D (SP-A and SP-D) are collectin proteins that are secreted by airway epithelial cells in the lung. They play an important role in first-line defense against infection within the lung. The aim of this study was to investigate the interaction between carbon nanotubes and proteins contained in lung surfactant. By using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Western Blotting, a novel technique of affinity chromatography based on carbon nanotube–Sepharose matrix and electron microscopy data it was shown that SP-A and SP-D selectively bind to carbon nanotubes. The binding was Ca2+-ion dependent, and was variable between batches of nanotubes. It was therefore likely to be mediated by surface impurities or chemical modifications of the nanotubes. Chronic level exposure to carbon nanotubes may result in sequestration of SP-D and SP-A. Absence of these proteins in knockout mice leads to susceptibility to lung infection and emphysema.
61- S. P. Somani, P. R. Somani, M. Umeno, E. Flahaut
Phys. stat. sol. (b), 244, (1), (2007), 136-141
"Improving photovoltaic response of Poly(3-hexylthiophene)/n-Si heterojunction by incorporating double walled carbon nanotubes"
Poly(3-hexylthiophene)/n-Si heterojunction solar cells were studied with and without incorporation of double walled carbon nanotubes (DWCNs) in the polymer layer. Performance of the device improves by manyfold by incorporation of DWCN. The authors report power conversion efficiency, open circuit voltage, short-circuit current density, and fill factor of 0.026%, 0.446 V, 0.3398 mA/cm², and 0.17, respectively, for an unoptimized cell containing DWCN. Reference cells without DWCNs show much lower performance. DWCN incorporation yields better hole transport, easy exciton splitting, and suppression of charge recombination, thereby improving photovoltaic action. DWCN seems promising materials for improving hole transport in organic solar cells. ©2006 American Institute of Physics
62- A. Bassil, P. Puech, W. Bacsa, P. S. Pizani, R. G. Jasinevicius, Ph. Demont, S. Barrau,
C. Lacabanne, R. Bacsa, E. Flahaut
Japan. J. Appl. Phys., 45, (10A), (2006), 7776-7779
"Laser induced modifications of carbon nanotube composite surfaces"
Carbon nanotubes epoxy composites have been processed with high power laser pulses and micro-machined with a single crystal diamond tool. The effect of the dispersion of the carbon nanotubes (CNTs, 0.4 wt. %) in the epoxy resin and carbon nanotube interaction with the composite matrix have been probed using spectroscopic Raman mapping. While the micromachined surface maintains a good electrical conductivity after machining, the surface is poorly conductive after laser ablation. Laser processing (power 150 J/pulse, 1064 nm) transforms the surface of the carbon nanotube nanocomposite up to a distance of 25 micrometers. AFM images show that the diamond machined surface reduces the composite surface roughness.
63- M. Monthioux, E. Flahaut, J.P. Cleuzioux
J. Mater. Res., 21, (11), (2006), 2774-2793
"Hybrid carbon nanotubes: strategy, progress and perspectives"
We introduce the concept of meta-nanotubes, among which are hybrid carbon nanotubes (X@CNTs), which are CNTs whose hollow core is filled—fully or partially—with foreign atoms, molecules, or compounds. The article focuses on the latter, describing their potential interest and the various ways currently available to synthesize them, while providing examples of the resulting materials mainly taken from the author’s works but also from literature, as characterized by means of high-resolution microscopy and related techniques. We discuss advantages and drawbacks of the various synthesis routes to help willing scientists and engineers to define a strategy for X@CNT synthesis with respect to their specific goals and expectations. Some examples of peculiar properties and behaviors of X@CNTs will be provided as well, although such related investigations are still scarcely reported because we are dealing with quite new nanomaterials.
64- J. González, Ch. Power, E. Belandria, J. M. Broto, P. Puech, J. Sloan, E. Flahaut
Phys. stat. sol. (b), 244, (1), (2007), 136-141
"Pressure dependence of Raman modes in DWCNT filled with PbI2 semiconductor"
Unpolarized Raman spectra of tangential modes on DWNTs filled with 1D nanocrystalline PbI2 semiconductor excited with 647 nm were studied at room temperature and elevated pressure up to 30 GPa. The tangential optical phonon modes of the carbon nanotubes are sensitive to the in plane stress and split into a contribution associated with the external and internal tube. Up to 11 GPa we find a pressure coefficient for the internal tube of 3.7 cm-1 GPa-1 and for the external tube of 6.3 cm-1 GPa-1. In addition, the tangential band of the external tubes broadens and decreases in amplitude. The corresponding Raman features of the internal tubes appear to be considerably less sensitive to pressure. In the range 11 to 15 GPa we observed a discontinuity in the slope (red shift) of the pressure dependence of the frequency of the tangential modes. This phase transition is associated to a possible structural distortion of the nanotube cross-section. When increasing the pressure furthermore up to 30 GPa the pressure coefficients for the tangential modes associated to the internal and external tubes are the same (10.6 cm-1 GPa-1). All findings lead to the conclusion that the outer tubes act as a protection shield fore the inner tubes (at least up to 11 GPa). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
65- J. Cheng, E. Flahaut, S. H. Cheng
Environmental Toxicology and Chemistry, (4), (2007), 708-716
"Effect of carbon nanotubes on developing zebrafish (Danio rerio) embryos"
The impact of carbon nanotubes (CNTs) on the aquatic environment was investigated by examining the properties of raw CNTs under several environmental conditions and using developing zebrafish (Danio rerio) embryos. The agglomerate size for single-walled CNTs (SWCNTs) was significantly larger at pH 11 or greater and was stable at temperatures from 4 to 40°C and salinities from 0 to 30 ppt. Exposure to SWCNTs induced a significant hatching delay in zebrafish embryos between 52 to 72 h postfertilization (hpf) at concentrations of greater than 120 mg/L, but 99% of the exposed embryos hatched by 75 hpf. Double-walled CNTs also induced a hatching delay at concentrations of greater than 240 mg/L, but carbon black did not affect hatching at the concentrations tested. Molecular and cellular analysis showed that the embryonic development of the exposed embryos up to 96 hpf was not affected at SWCNT concentrations of up to 360 mg/L. Scanning-electron microscopic inspection showed that the size of the pores on the embryo chorion was nanoscaled and that the size of SWCNT agglomerates was microscaled or larger, indicating that the chorion of zebrafish embryos was an effective protective barrier to SWCNT agglomerates. The hatching delay observed in this study likely was induced by the Co and Ni catalysts used in the production of SWCNTs that remained at trace concentrations after purification. This study suggests that materials associated with raw SWCNTs (perhaps metal contaminants) have the potential to affect aquatic life when released into the aquatic environment.
66- P. Somani, S. Somani, E. Flahaut, M. Umeno
Nanotechnology, 18, (2007), 185708:1-5
"Improving the photovoltaic response of a poly(3-octylthiophene)/n-Si heterojunction by incorporating double-walled carbon nanotubes"
Poly(3-octylthiophene)/n-Si heterojunction solar cells were studied with and without incorporation of double-walled carbon nanotubes (DWCNs) in the polymer layer. The performance of the device improves significantly by the incorporation of DWCNs. We report a power conversion efficiency, open circuit voltage, short-circuit current density and fill factor of 0.49%, 0.53 V, 5.9 mA cm-2 and 0.15 respectively for an un-optimized cell containing DWCNs. Reference cells without DWCNs show a much lower performance. DWCN incorporation yields better hole transport, easy exciton splitting and suppression of charge recombination, thereby improving photovoltaic action. DWCN seems a promising material for improving hole transport in organic solar cells.
67- P.R. Somani, S.P. Somani, S. P. Lau, E. Flahaut, M. Tanemura, M. Umeno
Solid State Electronics, 51, (5), (2007), 788-792
"Field electron emission of double walled carbon nanotube film prepared by drop casting method"
Thick films of double walled carbon nanotubes (DWCN) were deposited on indium-tin-oxide (ITO) coated glass substrates by drop casting method and were studied for their field electron emission property in a parallel plate configuration using bare ITO coated glass as counter electrode. They show excellent field electron emission property with low turn-on-field of about 0.8 V/µm and threshold field of about 1.8 V/µm. Field enhancement factor calculated from the non-saturated region of the FN plot is about 1715. Field electron emission current was observed to be stable up to 3000 min, indicating thereby that DWCNs are excellent electron emitters with appreciable stable performance.
68- P. Puech, E. Flahaut, A. Bassil, T. Juffmann, F. Beuneu, W. S. Bacsa
J. Raman Spectrosc., 38, (2007), 714-720
"Raman bands of double-wall carbon nanotubes: comparison with single- and triple-wall carbon nanotubes, and influence of annealing and electron irradiation"
We compare the G and G2D bands of single-, double- and triple-wall carbon nanotubes (CNTs). We observe that the band shape is sensitive to the number of walls of the CNTs. For single-wall carbon nanotubes (SWCNTs), the G band is composed of two distinct contributions G+ and G-, while the G band for double-wall nanotubes is composed of one band with two main contributions from the inner and the outer tube. The G2D band can be fitted with one Lorentzian for single-wall tubes, while two distinct contributions are observed for double-wall carbon nanotubes (DWCNTs). Considerable variations of the G2D band are found with similar first order Raman spectra. Annealing influences the D- and RBM-band intensities. Electron irradiation has the effect of decreasing the G- and D-band wavenumbers but does not enhance the D-band intensity considerably. The down-shifts of the G- and D-band wavenumbers are correlated and are the same for two excitation wavelengths. This is consistent with the scattering of phonons around the K-point. Copyright © 2007 John Wiley & Sons, Ltd.
69- A. Albina, P. L. Taberna, J. P. Cambronne, P. Simon, E. Flahaut, T. Lebey
Microelectronics Journal, 38, (4-5), (2007), 642-648
"Influence of carbonaceous electrodes on capacitance and breakdown voltage for hybrid capacitor"
This paper presents a new type of capacitor and deals with a hybrid approach where the advantages of two systems, dielectric capacitors and the ultracapacitor are combined. The objective is to increase the capacitance and the energy storage capability, while or at least preserving or decreasing the volume of the passive components. In this aim, the surface area and structural properties of ultracapacitor electrodes and the high dielectric strength of a polymer material are associated. The surface roughness of the carbonbased electrodes, namely (activated carbon—AC, and carbon nanotubes—CNTs), has a good impact on the capacitance. However, the surface roughness also depends on the composition of carbonaceous materials and so does the capacitance. Moreover, the choice of the dielectric material is the key parameter. The better the impregnation of the roughness is, the better is the increase of the capacitance.Since the final objective is to improve the electrical energy stored by the capacitor, the effect of surface roughness on the breakdown voltage is also evaluated.
70- M. Dragoman, K. Grenier, D. Dubuc, L. Bary, R. Plana, E. Fourn, E. Flahaut
J. Appl. Phys., 101, (2007), 106103:1-2
"Millimeter wave carbon nanotube gas sensor"
This Letter reports experimental observations regarding the significant changes in the transmission modulus and phase of the propagating microwave signals up to 110 GHz in a micromachined coplanar waveguide supported on a dielectric membrane with a thickness of 1.4 µm filled with a mixture of carbon nanotubes when exposed to nitrogen gas. These large shifts of amplitude and phase of microwave signals due to gas absorption represent the experimental basis on which a miniature wireless gas sensor could be implemented. ©2007 American Institute of Physics
71- F. Mouchet, P. Landois, E. Flahaut, E. Pinelli, L. Gauthier
Nanotoxicology, 1, (2), (2007), 149-156
"Assessment of the potential in vivo ecotoxicity of Double-Walled Carbon Nanotubes (DWNTs) in water, using the amphibian Ambystoma mexicanum"
Because of their specific properties (mechanical, electrical, etc), carbon nanotubes (CNTs) are being assessed for inclusion in many manufactured products. Due to their massive production and number of potential applications, the impact of CNTs on the environment must be taken into consideration. The present investigation evaluates the ecotoxic potential of CNTs in the amphibian larvae (Ambystoma mexicanum). Acute toxicity and genotoxicity were analysed after 12 days of exposure in laboratory conditions. The genotoxic effects were analysed by scoring the micronucleated erythrocytes in the circulating blood of the larvae according to the French standard micronucleus assay (AFNOR, 2000). The results obtained in the present study demonstrated that CNTs are neither acutely toxic nor genotoxic to larvae whatever the CNTs concentration in the water, although black masses of CNTs were observed inside the gut. In the increasing economical context of CNTs, complementary studies must be undertaken, especially including mechanistic and environmental investigations.
72- M. Monthioux, E. Flahaut
Mater. Sci. Eng. C, 27(5-8), (2007), 1096-1101
"Meta- and hybrid-CNTs: A clue for the future development of carbon nanotubes"
A new generation of carbon nanotubes (CNTs), which may be named “meta-nanotubes”, is more and more the focus of the research worldwide. They result from the transformation of “regular” CNTs by various ways such as functionalisation, doping, substitution, etc. The new nanomaterials thereby created are likely to exhibit new behaviors, specifically regarding properties that pristine CNTs do not possess (reactivity, solubility, magnetism…). The paper includes the description of the various routes to synthesize hybrid CNTs and their related advantages and limitations, while providing examples of the resulting materials from both literature and author’s team work. Hybrid SWNTs (abbreviated as X@SWNTs) are one example of meta-nanotubes, and consist in SWNTs whose the hollow core is fully or partially filled with foreign atoms, molecules, or compounds. The inserted material may then exhibit a peculiar behavior with respect to the macroscopic state, for several non-exclusive reasons: 1D-dimension preventing electron scattering and enhancing the role of surface atoms, protection from surface adsorption of disturbing molecules by the carbon sheath, anisotropic lattice distortion or creation of new structures due to imposed dimensions, interactions/electron coupling with the surrounding carbon lattice. A wide field is thus open, possibly even wider than for pristine SWNTs.
73- P. Puech, F. Puccianti, R. Bacsa, C. Arrondo, V. Paillard, A. Bassil, M. Monthioux, E. Flahaut,
F. Barde, W. Bacsa
Phys. Rev. B, 76, (5), (2007), 054118:1-4
"Ultraviolet photon absorption in single- and double-wall carbon nanotubes and peapods: Heating-induced phonon line broadening, wall coupling, and transformation."
Ultraviolet photon absorption has been used to heat single- and double-wall carbon nanotubes and peapods in vacuum. By increasing the laser intensity up to 500 mW, a downshift and a broadening of the optical phonons are observed corresponding to a temperature of 1000 °C. The UV Raman measurements are free of blackbody radiation. We find that the linewidth changes for the G+ and G- bands differ considerably in single-wall carbon nanotubes. This gives evidence that the phonon decay process is different in axial and radial tube directions. We observe the same intrinsic linewidths of graphite (highly oriented pyrolytic graphite) for the G band in single- and double-wall carbon nanotubes. With increasing temperature, the interaction between the walls is modified for double-wall carbon nanotubes. Ultraviolet photon induced transformations of peapods are found to be different on silica and diamond substrates.
74- F. Mouchet, P. Landois, E. Sarremejean, G. Bernard, P. Puech, E. Pinelli, E. Flahaut, L. Gauthier
Aquatic Toxicology, 87, (2), (2008), 127-137
"Characterisation and in vivo ectoxicity evaluation of double-wall carbon nanotubes in larvae of the amphibian xenopus laevis"
Because of their outstanding properties, carbon nanotubes (CNTs) are being assessed for inclusion in many manufactured products. Due to their massive production and growing number of potential applications, the impact of CNTs on the environment must be taken into consideration. The present investigation evaluates the ecotoxicological potential of double-walled carbon nanotubes (DWNTs) in the amphibian larvae Xenopus laevis at a large range of concentrations in water (from 10 to 500 mg/L). Acute toxicity and genotoxicity were analysed after 12 days of static exposure in laboratory conditions. Acute toxicity was evaluated according to the mortality and the growth of larvae. The genotoxic effects were analysed by scoring the micronucleated cells erythrocytes of the circulating blood of larvae according to the International Standard micronucleus assay. Moreover, histological preparations of larvae intestine were realized after 12 days of exposure for observation using photonic and transmission electron microscopy (TEM). Finally, an exposed intestine was prepared on a slide to analyse the corresponding Raman image. The results showed no genotoxicity in erythrocytes of larvae exposed to DWNTs in water, but acute toxicity whatever the concentration of DWNTs. Moreover, black masses suggesting CNTs were observed inside the intestine using optical microscopy and TEM, and confirmed by Raman spectroscopy analysis. Considering their increasingly use in commercial products and applications, assessing the CNTs risks requires better understanding, especially including mechanistic and environmental investigations.
75- M. Sendova, E. Flahaut
J. Appl. Phys., 103, (2008), 024311:1-6
"Comparative micro-Raman spectroscopy study of tellurium-filled double-walled carbon nanotubes"
Tellurium-filled double-walled carbon nanotubes (Te@DWNTs) have been studied by Raman spectroscopy in the temperature interval from 300 to 700 K employing 785 nm excitation wavelength, and their spectra have been compared to those of pristine double-walled carbon nanotubes (DWNTs). The DWNTs were synthesized by catalytic chemical vapor deposition. Assignment of the radial breathing modes and the tangential modes was done based on the one dimensional electronic energy band structure of carbon nanotubes. The tangential mode components of Te@DWNT are downshifted compared to those of pristine DWNT consistent with the proposed weakening of the carbon-carbon bond due to the introduced van der Waals interaction of the Te atoms with the DWNT. It was established that Te@DWNT can be unambiguously identified by the 30% temperature coefficient decrease of the G[prime]-band position.
76- S. P. Somani, P. R. Somani, E. Flahaut, G. Kalita, M. Umeno
Jap. J. Appl. Phys., 47, (2), (2008), 1219-1222
"Double-Walled Carbon Nanotubes-Incorporated Donor - Acceptor-Type Organic Photovoltaic Devices Using Poly(3-octylthiophene) and C60"
Donor–acceptor-type photovoltaic devices with a heterojunction between regioregular poly(3-octylthiophene) (P3OT) and C60 are fabricated with and without the addition of double-walled carbon nanotubes (DWCNs) in the polymer layer. Incorporation of DWCNs in the polymer layer improves the performance of the device by many folds, which is attributable to improved exciton dissociation and better charge transport leading to the suppression of charge carrier recombination. We report an opencircuit voltage, short-circuit current density, fill factor and conversion efficiency (%) of approximately 0.37 V, 0.014 mA/cm2, 0.22 and 0.001%, respectively, for an unoptimized device incorporating DWCNs.
77- J. Sloan, G. Matthewmann, C. Dyer-Smith, A.Y. Sung, Z. Liu, K. Suenaga, A. Kirkland, E. Flahaut
ACS Nano, 2, (5), (2008), 966-976
"Direct Imaging of the Structure, Relaxation and Sterically Constrained Motion of encapsulated Tungsten Polyoxometalate Lindqvist Ions within Carbon Nanotubes"
The imaging properties and observation of the sterically regulated translational motion of discrete tungsten polyoxometalate Linqvist ions (i.e., [W6O19]2-) within carbon nanotubes of specific internal diameter are reported. The translational motion of the nonspheroidal anion within the nanotube capillary is found to be impeded by its near-perfect accommodation to the internal van der Waals surface of the nanotube wall. Rotational motion of the anion about one remaining degree of freedom permits translational motion of the anion along the nanotube followed by locking in at sterically favorable positions in a mechanism similar to a molecular ratchet. This steric locking permits the successful direct imaging of the constituent octahedral cation template of individual [W6O19]2- anions by high resolution transmission electron microscopy thereby permitting meterological measurements to be performed directly on the anion. Direct imaging of pairs of equatorial W2 atoms within the anion reveal steric relaxation of the anion contained within the nanotube capillary relative to the bulk anion structure.
78- J. Jorge, E. Flahaut, F. Gonzalez-Jimenez, G. Gonzalez, J. Gonzalez, E. Belandria, J.M. Broto,
Chem. Phys. Lett.457, (2008), 347-351
"Preparation and characterization of alpha-Fe nanowires located inside Double Wall Carbon Nanotubes"
Capillary effect was used to fill double wall carbon nanotubes (DWCNT) with iron. The samples are characterized by Mössbauer and Raman spectroscopies, TEM, SAED, and magnetization. The experimental results indicate the presence of a-Fe nanowires inside the DWCNTs. The samples are ferromagnetic at room temperature. There are three striking results due to the confinement effects on the physical behavior of alpha-Fe: the hyperfine fields increase, the Debye temperature decreases and Raman modes are observed.
79- E. del Corro, J. Gonzales, M. Taravillo, E. Flahaut, V. Baonza
Nano Lett., 8, (8), (2008), 2215-2218
"Raman Spectra of Double-wall carbon nanotubes under extreme uniaxial pressures"
We investigated the pressure dependence of the Raman frequencies and intensities of the D and G bands of double-wall carbon nanotubes under strong uniaxial conditions. Using moissanite anvils, we observed for the first time the evolution of the D band under extreme stress/pressure conditions. We find that the difference between D and G frequencies remains constant over the whole stress range. In addition, we observe that double-wall carbon nanotubes behave elastically up to the maximum uniaxial stress reached in our experiments, which is estimated to be about 12 GPa.
80- P. Puech, A. Ghandour, A. Sapelkin, C. Tinguely, E. Flahaut, D. J. Dunstan, W. Bacsa
Phys. Rev. B, 78, (4), (2008), 045413:1-6
"Raman G-band in double wall carbon nanotubes combining p-doping and high pressure"
We use sulfuric acid as pressure medium to extrapolate the G-band position of the inner and outer tubes of double-wall carbon nanotubes. Keeping the G-band position of the inner and outer tubes constant, we can determine the fraction of double-wall and single-wall tubes in samples containing a mixture of the two. A-band-related electronic interwall interaction at 1560 cm-1 is observed, which is associated with the outer tube walls. This band is observed to shift with pressure at the same rate as the G band of outer tubes and is not suppressed with chemical doping. Differences in the interwall interaction is discussed for double-wall carbon nanotubes grown by the catalytic chemical-vapor method and double-wall carbon nanotubes obtained through transformation of peapods.
81- P. Landois, A. Peigney, Ch. Laurent, L. Frin, E. Flahaut
Carbon, 47, (3), (2009), 789-794
"CCVD synthesis of carbon nanotubes with W/Co-MgO catalysts"
Carbon nanotubes (CNT) were prepd. from a H2-CH4 mixt. with W/Co-MgO catalyst by a catalytic chem. vapor deposition (CCVD) method. Different W/Co ratios were investigated. From TEM observations, it was obsd. that both the no. of walls and the diam. of CNT increased with the proportion of tungsten. A promoter effect was obsd. as long as the proportion of W was kept low and CNT with a no. of walls ranging from 2 to 5 were obtained. With a higher proportion of W, multi-walled carbon nanotubes (MWNT) 10 walls were prepd., together with addnl. undesirable carbon nanofibers.
82- J. Gonzalez, C. Power, E. Belandria, J. Jorge, F. Gonzalez-Jimenez, M. Millot, S. Nanot, J. M. Broto, E. Flahaut
High Pressure Research, 28, (4), (2008), 577-582
"Pressure dependence of Raman modes in double wall carbon nanotubes filled with alpha-Fe"
The prepn. of highly anisotropic one-dimensional (1D) structures confined into carbon nanotubes (CNTs) in general is a key objective in CNTs research. In this work, the capillary effect was used to fill double wall carbon nanotubes with iron. The samples are characterized by Mossbauer and Raman spectroscopy, transmission electron microscopy, scanning area electron diffraction, and magnetization. In order to investigate their structural stability and compare it with that of single wall carbon nanotubes (SWNTs), elucidating the differences induced by the inner-outer tube interaction, unpolarized Raman spectra of tangential modes of double wall carbon nanotubes (DWNTs) filled with 1D nanocrystallin .alpha.-Fe excited with 514 nm were studied at room temp. and elevated pressure. Up to 16 GPa we find a pressure coeff. for the internal tube of 4.3 cm-1 GPa-1 and for the external tube of 5.5 cm-1 GPa-1. In addn., the tangential band of the external and internal tubes broadens and decreases in amplitude. All findings lead to the conclusion that the outer tube acts as a protection shield for the inner tubes (at least up 16 GPa). Structural phase transitions were not obsd. in this range of pressure.
83- F. Legorreta Garcia, C. Estournès, A. Peigney, A. Weibel, E. Flahaut, Ch. Laurent
Scripta Materiala, 60, (2009), 741-744
"Carbon nanotube-magnesia nanocomposites by spark-plasma-sintering: microstructure, electrical conductivity and microhardness"
A double-walled carbon nanotube-MgO powder is prepd. without any mixing. The applied pressure is the main parameter acting on densification. Increasing the max. temp. and holding time is marginally beneficial. The nanotubes are blocking the matrix grain growth. The nanocomposite prepd. using the most severe spark plasma sintering conditions (1700 C, 150 MPa) shows mostly undamaged nanotubes and a higher microhardness than the other materials, reflecting a better bonding between nanotubes and matrix. The elec. cond. of all nanocomposites is over 12 S/cm.
84- C. Lamprecht, J. Danzberger, P. Lukanov, C. M. Tîlmaciu, A. M. Galibert, B. Soula, E. Flahaut, H. J. Gruber, P. Hinterdorfer, A. Ebner, F. Kienberger
Ultramicroscopy109, (8), (2009), 899-906
"AFM Imaging of Functionalized Double-Walled Carbon Nanotubes"
We present a comparative study of several non-covalent approaches to disperse, debundle and non-covalently functionalize double-walled carbon nanotubes (DWNTs). We investigated the ability of bovine serum albumin (BSA), phospholipids grafted onto amine-terminated poly-ethylene glycol (PL-PEG2000-NH2), as well as a combination thereof, to coat purified DWNTs. Topographical imaging with the atomic force microscope (AFM) was used to assess the coating of individual DWNTs and the degree of debundling and dispersion. Topographical images showed that functionalized DWNTs are better separated and less aggregated than pristine DWNT and that the different coating methods differ in their abilities to successfully debundle and disperse DWNTs. Height profiles indicated an increase in the diameter of DWNTs depending on the functionalization method and revealed adsorption of single molecules onto the nanotubes. Biofunctionalization of the DWNT surface was achieved by coating DWNTs with biotinylated BSA, providing for biospecific binding of streptavidin in a simple incubation step. Finally, biotin-BSA-functionalized DWNTs were immobilized on an avidin layer via the specific avidin-biotin interaction.
85- V. Datsyuk, P. Landois, J. Fitremann, A. Peigney, A. M. Galibert, B. Soula, E. Flahaut
J. Mater. Chem., 19, (2009), 2729-2736
"Double-Walled Carbon Nanotube dispersion via surfactant substitution"
A new approach for the stabilization of double-walled carbon nanotubes in aq. media was developed. A low mol. wt. surfactant was used in the first stage for the debundling of the nanotubes followed by substitution with a higher mol. wt. surfactant or non-ionic surfactants. Dispersions were characterized by optical d. measurements, SEM and DLS. The presence of remaining low mol. wt. surfactant was investigated by FT-IR. Double walled carbon nanotube dispersions showed good dispersion stability and non-detectable amts. of the initial surfactant, which was completely removed. Such a method could be useful for prepn. of stable aq. dispersions of carbon nanotubes with low concn. of surfactants, which is esp. important for toxicity studies.
86- P. Puech, A. Waheed Anwar, E. Flahaut, D. J. Dunstan, A. Bassil, W. Bacsa
Phys. Rev. B, 79, (8), (2009), 085418:1-4
"Raman G and D band in strongly photoexcited carbon nanotubes"
The authors observe clear differences in the spectral shift of the Raman D and G bands when heating double wall C nanotubes through intense photon irradn. and by varying the temp. in a thermostat. These spectral differences are attributed to modifications of the defect induced double-resonance Raman process, and are consistent with Stokes-anti-Stokes anomalies obsd. for single and double wall C nanotubes, not present in graphite. The Raman intensity for double wall C nanotubes increases superlinearly in the red spectral region and sublinearly in the UV spectral region.
87- M. Sendova, E. Flahaut, L. Datas
J. Appl. Phys., 105, (2009), 094312:1-5
"Micro-Raman scattering of Selenium-filled double-walled carbon nanotubes: temperature study"
Selenium-filled double-walled carbon nanotubes (Se@DWNT) have been studied by High Resolution Transmission Electron Microscopy (HRTEM) and micro- Raman spectroscopy in the temperature interval from 80 K to 600 K employing 785 nm excitation wavelength. The temperature dependence of the dominant bands (G-band and G'-band) are analyzed in terms of the model developed by Klemens, Hart, Agraval, Lax, Cowley and extended by Balkanski for anharmonic decay of optical phonons. The findings were compared to analogous study for empty double carbon nanotubes (DWNT). The DWNT inter-atomic force constants modification as a result of the presence of the Se atoms inside the tubes is revealed through larger anharmonicity constants describing the temperature dependences of the G'-band and the inner tube tangential modes (G-band).
88- J. Cambedouzou, M. Chorro, R. Almairac, L. Noé, E. Flahaut, S. Rols, M. Monthioux, P. Launois
Phys. Rev. B., 79, (2009), 195423:1-8
"X-ray diffraction as a tool for the determination of the structure of double-walled carbon nanotubes batches"
The av. structure of double-walled carbon nanotube (DWCNT) samples can be detd. by x-ray diffraction (XRD). We present a formalism that allows XRD patterns of DWCNTs to be simulated and we give researchers the tools needed to perform these calcns. themselves. Simulations of XRD patterns within this formalism are compared to exptl. data obtained on two different DWCNT samples, produced by chem. vapor deposition or by peapod conversion (i.e., high-temp. peapod annealing). For each sample, we are able to det. structural aspects such as the no. of walls, the diam. distribution of inner and outer tubes, the intertube spacing, and the bundled structure.
89- F. Mouchet, P. Landois, V. Datsyuk, P. Puech, E. Pinelli, E. Flahaut, L. Gauthier
Env. Toxicology, Accepted for publication (proof state)
"Use of the international amphibian micronucleus standardised procedure (ISO 21427-1) for in vivo evaluation of double-walled carbon nanotubes (DWNTs) toxicity and genotoxicity in water"
Considering the important production of Carbon Nanotubes (CNTs), it is likely that some of them will contaminate the environment during each step of their life cycle. Nevertheless, there is little known about their potential ecotoxicity. Consequently, the impact of CNTs on the environment must be taken into consideration. This work evaluates the potential impact of well characterised Double-Walled carbon NanoTubes (DWNTs) in the amphibian larvae Xenopus laevis under normalised laboratory conditions according to the International Standard micronucleus assay ISO 21427-1:2006 for 12 days of half-static exposure to 0.1 – 1 – 10 and 50 mg/L of DWNTs in water. Two different endpoints were carried out: (i) toxicity (mortality and growth of larvae) and (ii) genotoxicity (induction of micronucleated erythrocytes). Moreover, intestine of larvae were analysed using Raman spectroscopy. The DWNTs synthetized by Catalytic Chemical Vapour Deposition (CCVD) were used as produced (experiment I) and the addition of Gum Arabic (GA) was investigated to improve the stability of the aqueous suspensions (experiment II). The results show growth inhibition in larvae exposed to 10 and 50 mg/L of DWNTs with or without GA. No genotoxicity was evidenced in erythrocytes of larvae exposed to DWNTs, except to 1 mg/L of DWNTs with GA suggesting its potential effect in association with DWNTs at the first non-acutely toxic concentration. The Raman analysis confirmed the presence of DWNTs into the lumen of intestine but not in intestinal tissues and cells, nor in the circulating blood of exposed larvae.
90- L. Picard, F. Lincker, Y. Kervella,M. Zagorska, R. de Bettignies, A. Peigney, E. Flahaut, G. Louarn, S. Lefrant, R. Demadrille, A. Pron
J. Phys. Chem.C, 113, (40), (2009), 17347-17354
"Composites of Double-Walled Carbon Nanotubes with bis-Quaterthiophene-Fluorenone Conjugated Oligomer: Spectroelectrochemical and Photovoltaic Properties"
A new composite consisting of a semiconducting oligomer, namely 2,7-bis-(3,3'''-didodecyl-[2,2',5',2'';5'',2''']quaterthiophen-5-yl)-fluoren-9-one (QTF12), and double walled carbon nanotubes (DWCNT) has been prepd. in view of its application as an active component in bulk heterojunction photovoltaic cells. Raman spectroelectrochem. investigations show that the onset of the oxidative doping of QTF12 in the presence of DWCNT occurs at E = 0.475 V vs. Ag/Ag+, which is 50 mV lower than in the case of pure QTF12. This effect was independently confirmed by UV-visible-near-IR spectroelectrochem. The lowering of the oxidative doping potential, detected by spectroelectrochem., can be taken as a spectroscopic evidence of oligomer-nanotube interactions which result in raising, by 0.05 eV, the HOMO level of these QTF12 mols. which are at the interface with DWCNT. Bulk heterojunction test photovoltaic cells consisting of a ternary system (QTF12-DWCNT, PCBM) show an open-circuit voltage of 0.53 V and a power conversion efficiency of 0.43%.
91- C.-M. Tîlmaciu, B. Soula, A.-M. Galibert, P. Lukanov, L. Datas, J. González, L. Fernández Barquín, J. Rodríguez Fernández, F. González-Jiménez, J. Jorge, E. Flahaut
Chem. Commun., 43, (2009), 6664-6666
"Synthesis of superparamagnetic Iron (III) oxide nanowires in double-walled carbon nanotubes"
The synthesis and characterization of superparamagnetic iron(iii) oxide nanowires confined within double-walled carbon nanotubes by capillary filling with a melted precursor (iron iodide) followed by thermal treatment is reported for the first time.
92- M. Dragoman, E. Flahaut, D. Dragoman, M. Al Ahmad, R. Plana
Nanotechnology, 20, (37), (2009), 375203:1-4
"Writing simple RF electronic devices on paper with carbon nanotube ink"
This paper shows that we can print on paper simple high-frequency electronic devices such as resistances, capacitances or inductances, with values that can be changed in a controllable manner by an applied dc voltage. This tunability is achieved with the help of an ink contg. functionalized carbon nanotubes and water. After the water is evapd. from the paper, the nanotubes remain steadily imprinted on paper, showing a semiconducting behavior and tunable elec. properties.
93- C. Lamprecht, I. Liashkovich, V. Neves, J. Danzberger, E. Heister, M. Rangl, H. M. Coley, J. McFadden, E. Flahaut, H. J. Gruber, P. Hinterdorfer, F. Kienberger and A. Ebner
Nanotechnology, 20, (37), (2009), 434001:1-7
"AFM imaging of functionalized carbon nanotubes on biological membranes"
Multifunctional carbon nanotubes are promising for biomedical applications as their nano-size, together with their phys. stability, gives access into the cell and various cellular compartments including the nucleus. However, the direct and label-free detection of carbon nanotube uptake into cells is a challenging task. The at. force microscope (AFM) is capable of resolving details of cellular surfaces at the nanometer scale and thus allows following of the docking of carbon nanotubes to biol. membranes. Here we present topog. AFM images of non-covalently functionalized single walled (SWNT) and double walled carbon nanotubes (DWNT) immobilized on different biol. membranes, such as plasma membranes and nuclear envelopes, as well as on a monolayer of avidin mols. We were able to visualize DWNT on the nuclear membrane while at the same time resolving individual nuclear pore complexes. Furthermore, we succeeded in localizing individual SWNT at the border of incubated cells and in identifying bundles of DWNT on cell surfaces by AFM imaging.
94- R. Fleurier, J-S. Lauret, E. Flahaut, A. Loiseau
Phys. Status Solidi B, 246, 11-12, (2009), 2675-2678
"Sorting and transmission electron microscopy analysis of single or double wall carbon nanotubes"
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 ultracentrifugation 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 sorted samples such as the real mean diameter, the relative concentration of double walled carbon nanotubes over single walled carbon nanotubes, standard deviation, and the real diameter distribution of carbon nanotubes, even beyond any possible accurate analysis from optical absorption spectroscopy. Therefore, we demonstrate that the diameter analysis of the sorted samples by TEM can indeed afford some information about the relevant optical properties of carbon nanotubes.
95- F. Mouchet, P. Landois, P. Puech, E. Pinelli, E. Flahaut, L. Gauthier
Nanomedicine, Accepted (Aug. 2010)
"CNT ecotoxicity in amphibians: assessment of multi-walled carbon nanotubes and comparison with double-walled carbon nanotubes"
The potential impact of industrial Multi-Walled NanoTubes (MWNT) was investigated under normalised laboratory conditions according to the International Standard micronucleus assay ISO 21427-1 for 12 days of half-static exposure to 0.1 – 1 – 10 and 50 mg.L-1 of MWNT in water. Three different endpoints were carried out for 12 days of exposure: mortality, growth inhibition, and micronuclei induction in erythrocytes of the circulating blood of larvae. Raman spectroscopy analysis was used to study the presence of CNT in the biological samples. Considering the high diversity of CNT according to their different characteristics, MWNT were analyzed in Xenopus larvae, comparatively to Double-Walled NanoTubes (DWNT) used in a previous study in similar conditions. Growth inhibition in larvae exposed to 50 mg.L-1 of MWNT was evidenced, however no genetoxicity (micronucleus assay) was noticed, whatever the concentration. Carbon Nanotubes localisation in the larvae leads to different possible hypothesis of mechanisms explaining toxicity in Xenopus.
96- K. W. Kwok, K. M. Leung, E. Flahaut, J. Cheng, S. H. Cheng
Nanomedicine, Accepted (Aug. 2010)
"Chronic toxicity of double-walled carbon nanotubes to three marine organisms: Influence of different dispersion methods"
Double-walled carbon nanotubes (DWNTs) are found in a variety of consumer products but there is no ecotoxicity data of DWNTs to marine organisms. Chronic toxicity of DWNTs was investigated with the diatom Thalassiosira pseudonana, copepod Tigriopus japonicus and medaka Oryzias melastigma. DWNTs were dispersed using sonication (so-DWNTs) and stirring (st-DWNTs) for comparison. The median aggregation size (0.89 µm2) of so-DWNTs was smaller than that of st-DWNTs (21.8 µm2). Exposure to DWNTs led to growth inhibition of T. pseudonana with EC50s of 1.86 and 22.7 mg l-1 for so- and st-DWNTs respectively. Population growth of T. japonicus was reduced at ? 0.1 mg l-1 for so-DWNTs and 10 mg l-1 for st-DWNTs. Growth inhibition in O. melastigma was observed at 10 mg l-1 for so-DWNTs but not for st-DWNTs. Given that so-DWNTs are consistently significantly more toxic than st-DWNTs, dispersion method and size of aggregations should be considered in DWNT toxicity testing.
97- E. Belandria, M. Millot, J-M. Broto, E. Flahaut, F. Rodriguez, R. Valiente, J. Gonzalez
Carbon, 48, (2010), 2566-2572
"Pressure dependence of Raman modes in double wall carbon nanotubes filled with 1D Tellurium"
The preparation of highly anisotropic one-dimensional (1D) structures confined into carbon nanotubes (CNTs) in general is a key objective in nanoscience. In this work, capillary effect was used to fill double wall carbon nanotubes (DWCNTs) with trigonal Tellurium. The samples are characterized by high resolution transmission electronic microscopy and Raman spectroscopy. In order to investigate their structural stability and unravel the differences induced by intershell interactions, unpolarized Raman spectra of radial and tangential modes of DWCNTs filled with 1D nanocrystalline Te excited with 514 nm were studied at room temperature and high pressure. Up to 11 GPa we found a pressure coefficient of 3.7 cm-1 GPa-1 for the internal tube and 7 cm-1 GPa-1 for the external tube. In addition, the tangential band of the external and internal tubes broaden and decrease in amplitude. All findings lead to the conclusion that the outer tube acts as a protection shield for the inner tube (at least up 11 GPa). No pressure-induced structural phase transition was observed in the studied range.
98- E. Heister, C. Lamprecht, V. Neves, C. Tîlmaciu, L. Datas, E. Flahaut, B. Soula, P. Hinterdorfer, H. M. Coley, S. R. Silva, J. McFadden
ACS Nano, 4, (5), (2010), 2615-2626
"Higher dispersion efficacy of functionalized carbon nanotubes in chemical and biological environments"
Aqueous dispersions of functionalized carbon nanotubes (CNTs) are now widely used for biomedical applications. Their stability in different in vitro or in vivo environments, however, depends on a wide range of parameters, such as pH and salt concentrations of the surrounding medium, and length, aspect ratio, surface charge, and functionalization of the applied CNTs. Although many of these aspects have been investigated separately, no study is available in the literature to date, which examines these parameters simultaneously. Therefore, we have chosen five types of carbon nanotubes, varying in their dimensions and surface properties, for a multidimensional analysis of dispersion stability in salt solutions of differing pH and concentrations. Furthermore, we examine the dispersion stability of oxidized CNTs in biological fluids, such as cellular growth media and human plasma, and their toxicity toward cancer cells. To enhance dispersibility and biocompatibility, the influence of different functionalization schemes is studied. The results of our investigations indicate that both CNT dimensions and surface functionalization have a significant influence on their dispersion and in vitro behavior. In particular, factors such as a short aspect ratio, presence of oxidation debris and serum proteins, low salt concentration, and an appropriate pH are shown to improve the dispersion stability. Furthermore, covalent surface functionalization with amine-terminated polyethylene glycol (PEG) is demonstrated to stabilize CNT dispersions in various media and to reduce deleterious effects on cultured cells. These findings provide crucial data for the development of biofunctionalization protocols, for example, for future cancer theranostics, and optimizing the stability of functionalized CNTs in varied biological environments.
99- Ch. Laurent, E. Flahaut, A. Peigney
Carbon, 48, (2010), 2994-2996
"The weight and density of carbon nanotubes versus the number of walls and diameter"
The weight and density of carbon nanotubes are calculated as a function of their characteristics (inner diameter, outer diameter, and number of walls). The results are reported in the form of diagrams which may be useful to other researchers, in particular in the fields of synthesis/production, materials and composites, health/toxicity studies.
100- D. Crouzier, S. Follot, E. Gentilhomme, E. Flahaut, R. Arnaud, V. Dabouis, C. Castellarin, J.C. Debouzy
Toxicology, 272, (1-3), (2010), 39-45
"Carbon nanotubes induce inflammation but decrease the production of reactive oxygen species in lung"
With the rapid spread of carbon nanotubes (CNTs) applications, the respiratory toxicity of these compounds has attracted the attention of many scientists. Several studies have reported that after lung administration, CNTs could induce granuloma, fibrosis, or inflammation. By comparison with the mechanisms involved with other toxic particles such as asbestos, this effect could be attributed to an increase of oxidative stress. The aim of the present work was to test this hypothesis in vivo. Mice were intranasally instilled with 1.5 mg/kg of double walled carbon nanotubes (DWCNTs). Six, 24, or 48 h after administration, inflammation and localisation of DWCNTs in lungs were microscopically observed. Local oxidative perturbations were investigated using ESR spin trapping experiments, and systemic inflammation was assessed by measuring the plasma concentration of cytokines TNF-a, IL-1a, IL-1ß, IL-6, IGF-1, Leptin, G-CSF, and VEGF. Examination of lungs and the elevation of proinflammatory cytokines in the plasma (Leptin and IL-6 at 6 h) confirmed the induction of an inflammatory reaction. This inflammatory reaction was accompanied by a decrease in the local oxidative stress. This effect could be attributed to the scavenger capability of pure CNTs.