decoration of carbon nanotubes with metal nanoparticles by wet chemical method: a small-angle...

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Copyright © 2010 American Scientific PublishersAll rights reservedPrinted in the United States of America

Journal ofNanoscience and Nanotechnology

Vol. 10, 1–9, 2010

Decoration of Carbon Nanotubes with MetalNanoparticles by Wet Chemical Method:A Small-Angle Neutron Scattering Study

J. Bahadur1�∗, D. Sen1, S. Mazumder1, Jyoti Parkash2,D. Sathiyamoorthy2, and R. Venugopalan2

1 Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India2Powder Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

Multi-wall carbon nanotubes have been synthesized by catalytic chemical vapour deposition method.Attempts have been made to decorate the walls of these nanotubes with various metal nano-particles (Ni, Cu and Fe) after functionalizing the nanotubes walls by wet chemical method. Small-Angle Neutron Scattering data reveals chain cluster type morphology of the carbon nanotubes.Transmission electron microscopy, Energy dispersive analysis of X-rays and Small-Angle NeutronScattering measurements show that decoration of nanotube walls by metallic nano-particles couldbe realized for Ni and Cu nano-particles. Further, wall decoration by nano-particles of Fe could notbe achieved by wet chemical method due to strong agglomeration behavior of Fe nano-particles.

Keywords: SANS, MWNTS, Nano-Particle, Agglomeration.

1. INTRODUCTION

Since, the synthesis of carbon nanotubes (CNTs) has beenachieved1 in macroscopic quantities, it has become possi-ble to explore their physical and chemical characteristics.2

Novel well defined tubular structure of CNTs contin-ues to attract interest as a fascinating model system forfundamental scientific research with potential for sev-eral promising applications.3 For various technologicalapplications, in different areas of nanotechnology, CNTsneed to be interfaced with a variety of other materi-als, ranging from inorganic materials,4 polymer coatings5

to bio-molecules6 etc. Among these hybrid materials, aninteresting class of derivative results from the deposi-tion of inorganic materials, such as metallic,7–13 semiconducting14–18 and insulating19–21 nano-particles on CNTssurfaces.22 These nano-particulate hybrid systems, derivedfrom inorganic solids and CNTs, have unique optical, elec-trical and mechanical properties. Further, they are promis-ing materials for nanoelectronics and other applications.

In order to efficiently synthesize the CNT based mono-hybrids with various inorganic particles, it is necessaryto activate the surface of the nanotubes that are chemi-cally inert. Recently, extensive experiments are being per-formed towards the functionalization of the side wall of the

∗Author to whom correspondence should be addressed.

CNTs,23–28 since they are good templates for adsorption ofnanoparticles.29–30

Two main approaches, considered for the surface modi-fications, are covalent chemical approach and non-covalentapproach. The covalent chemical modification is carriedout via enabling covalent bonding between CNTs andthe material of interest.31–34 It can increase the solubil-ity of carbon nanotubes and open up the possibility ofattaching other molecules to the CNTs.35–36 Examples ofsuch covalent linkages, achieved through chemical func-tionalization, have been used in CNTs-reinforced polymercomposites37–38 and biological systems.39–40 One of thecovalent approaches for functionlization of CNTs walls’is refluxing nanotubes with nitric acid. It is known thatrefluxing carbon nanotubes with nitric acid not only opensup the closed tips of the tubes but also creates acid sitesand defects on the surfaces.41–42 The acid sites are com-posed of functional groups such as –COOH and –OH,which can act as nucleation centres for metal ions.42 Thus,this method has an advantage over non-covalent surfacemodification method that inner wall of CNTs may also bedecorated. Nanotubes can be filled by some metal or metaloxide in this method which is otherwise not possible bythe non-covalent method. However, all covalent chemicalapproaches, may disrupt the intrinsic mechanical and elec-trical properties of a CNTs. As a result, some works were

J. Nanosci. Nanotechnol. 2010, Vol. 10, No. xx 1533-4880/2010/10/001/009 doi:10.1166/jnn.2010.2169 1

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Decoration of Carbon Nanotubes with Metal Nanoparticles by Wet Chemical Method Bahadur et al.

also attempted to functionalize the side wall of carbonnanotubes by the non-covalent method,23�28 which modi-fies the surface of the carbon nanotube via non-covalentinteractions (van der Waals interaction, � stacking etc.)and which can preserve the unique properties of CNTs.

Small-angle scattering is an ideal tool for investigatingthe CNT structures.43–49 Small-Angle Neutron Scattering(SANS) probes the density fluctuations in mesoscopiclength scale.50–54 SANS provides statistically averagedinformation of a bulk sample. It had been observed thatthe CNTs are generally not found in a dispersed form.Rather, they are often found in branched or in aggregatedform.44�55–57 Such aggregations may often be treated as afractal in order to have a quantitative measure of the mor-phology of these aggregates, SANS is a convenient methodto characterize such disordered aggregated or branchedobjects using.58a A fractal object58b like Sierpinski gasketwhich is generated by mathematical rules possesses selfsimilarity i.e., they look similar under change of scale i.e.,they are scale invariant objects. It is worthy to mentionthat various natural and synthesized objects do not pos-sess exact self similarity but possess self affinity (wherethe scaling factors are directional dependent) in a statisti-cal sense. It is well established that the scattering inten-sity (I(q)) as a function of wave-vector transfer (q), for afractal object (with mass fractal dimension D), follows apower law, I(q) ∼ q−D, for a wide range of q.

In the present study, a covalent chemical approach hasbeen adopted to functionalize walls of multi-wall carbonnanotubes (MWNTs) by treating with nitric acid. Effortshave been made to deposit metal nanoparticles (Ni, Cuand Fe) directly on the surface of acid treated MWNTsby wet chemical method. SANS have been used to inves-tigate the morphology of MWNTs. Transmission elec-tron microscopy (TEM) and energy dispersive analysis ofX-rays (EDAX) have also been used, as a direct method,to characterize the metal decorated nanotubes. It is wor-thy to mention here that microscopy and SANS are twocomplementary techniques to study such systems.

2. EXPERIMENTAL DETAILS

2.1. Sample Preparation

The following experimental procedure has been carried outfor decorating the walls of MWNTs with metal (M) nano-particles (Ni, Cu and Fe). The pre synthesized MWNTsby catalytic chemical vapour deposition method, is treatedwith the concentrated HNO3 and heated at 70 �C for24 hours in order to create the active centres on the sidewalls and to open the end caps of CNTs. For decorationof CNTs, metal nitrate, M(NO3)2, dissociation has beencarried out in the presence of synthesized acid treatednanotubes. For this purpose, 50 mg of M(NO3)2 washomogeneously dissolved in 50 ml of deionized water

together with the 250 mg powder of acid treated nano-tubes. Mild sonication for 20 minutes has been performedto avoid agglomeration of CNTs.

The solution was then dehydrated at 500 �C in order toget metal oxides, MO, as the product. This metal oxide isthen reduced to metallic phase by performing the reductionreaction in the presence of hydrogen atmosphere at 700 �C.The high purity hydrogen gas has been allowed to pass ata flow rate of 100 sccm (standard cubic centimeter) forone hour.

MO+H2 → M+H2O

The sample was placed into a quartz tube and heated untilthe reduction temperature is achieved in the presence ofargon flow. The obtained CNTs, nano-particle compos-ite has been characterized by the transmission electron

Fig. 1. TEM micrograph of BCNT, showing the chain cluster typestructure of MWNTs.

Fig. 2. TEM micrograph of the NiCNT. The Ni nano-particle decoratedat the walls of the MWNTs.

2 J. Nanosci. Nanotechnol. 10, 1–9, 2010

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Bahadur et al. Decoration of Carbon Nanotubes with Metal Nanoparticles by Wet Chemical Method

Fig. 3. TEM micrograph of the NiCNT in magnified scale.

microscope (JEOL TEM 2000FX) in order to confirm thepresence of nanoparticles on surface walls of MWNTs.TEM micrographs are presented in Figures 1–6. Further,to have an elemental analysis of each sample, EDAX hasbeen performed. Results are shown in Figures 7–12. TheEDAX spectrums at different zone of the specimen con-firm the metal formation in the specimens. The samples

Fig. 4. TEM micrograph of CuCNT. It is seen that nano-particle clusteris attached to the walls of the nanotubes.

Fig. 5. TEM micrograph of CuCNT in magnified scale.

prepared by this method will be named as following. Acidtreated CNTs, Ni nano-particle-MWNTs composite, Cunano-particle-MWNTs composite and Fe nano-particle-MWNTs composite are represented by BCNT, NiCNT,CuCNT and FeCNT, respectively.

2.2. SANS Experiments

SANS experiments have been carried out by using adouble crystal based medium resolution small-angle neu-tron scattering instrument (MSANS) at the Guide TubeLaboratory of the Dhruva rector at Trombay, India.59

The instrument consists of a non-dispersive (1,−1) set-ting of (111) reflections from silicon single crystals withspecimen between two crystals. The scattered intensitieshave been recorded as a function of wave vector trans-fer q � = 4�sin(��/, where 2� is the scattering angle and ( = 0.312 nm) is the incident neutron wavelength for thepresent experiment]. Measurements have been performedon MWNTs (BCNT) and MWNTs-nano-particle compos-ites (NiCNT, CuCNT and FeCNT). SANS profiles wererecorded in q-range 0.003–0.17 nm−1. SANS profiles of

Fig. 6. TEM micrograph of FeCNT sample, showing agglomerates ofFe nano-particles.

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Fig. 7. Sites of interest of the NiCNT specimen for EDAXS study.

0Full scale 1256 cts

2 4 6 8keV

10 0Full scale 7623 cts

2 4 6 8keV

10


2 4 6 8keV


2 4 6 8keV

10

0Full scale 586 cts

2 4 6 8keV

10

Fig. 8. Different EDAX spectrums showing carbon and nickel peaks in NiCNT.

the specimens were corrected for transmission and instru-ment resolution60 prior to further analysis. The correctedprofiles have been shown in Figure 13.

3. DATA ANALYSIS AND DISCUSSIONS

It is well known45–47 that nanotubes dispersed or in pow-der form exhibit flexibility and often exist as agglomeratedclusters even in well dispersed samples. From TEM micro-graph (Fig. 1) of BCNT sample; branched or rope-likestructure of bundled MWNTs is evident. This structure isfurther verified by observation of an extensive linear regionin the log–log plot of SANS profile (Fig. 13). Linear regionin a wide q-range of scattering profile in log–log plotmay have different slopes in different length scale,46 whichoriginates from different agglomeration nature of CNTs.Power law depends on the type of the structures, such as,self-avoiding polymer chain, which has a slope −5/3 anda Gaussian chain, which has a slope −2 in log–log plotof scattering profile. Some times, structures may undergo


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Fig. 9. Sites of interest of the CuCNT specimen for EDAXS study.

a kind of a transition in slopes of power law regime inlog–log plot, relating to an internal size. For example, ifa long rod is broken along its length, forming a series ofconnected rigid segments, it appears as a rod at lengthsbelow its “persistence length” and as a self-avoiding poly-mer chain structure at a longer length scales. There is achange of power law exponent from −5/3 to −1 at q valuedependent on the persistence length. In any practical sit-uation, typical scattering experiment covers only a lim-ited range of q, hence measures certain regions of fractalagglomerates. Thus, depending on q-window of the SANSmeasurements, the exponent of the power laws may beestimated from the slope of the log–log plot of the scat-tering profile.

SANS profiles in log–log plot in Figure 13, show alinear region over a wide q-range for three specimens(BCNT, NiCNT and CuCNT) implying a network ofMWNTs. Thus, we envision a fractal network of MWNTsmodel to explain SANS data.

SANS intensity I(q) from mass fractal agglomerate isgiven as,

Iq�= C Pcq� r0�L�Scq� r0� (1)

where C is the scale parameter, Pc(q, r0, L) is the form fac-tor of a cylinder with radius r0 and length L. The expres-sion for the cylindrical form factor can be written as,

Pcq� r0�L� =∫ �/2

0

[2J1q r0 sin��

q r0 sin�sinq L cos��/2q L cos��/2

]2

× sin��d� (2)

where J1(x) is the first order Bessel function.

Fig. 10. Different EDAX spectrums showing carbon and nickel peaks in CuCNT.

Electron image 120 µm

Fig. 11. Sites of interest of the FeCNT specimen for EDAXS study.

Sc(q, r0� is the static structure factor of the mass fractalagglomerates61–63 of CNTs and is given by,

Scq� = 1+ 1qro�

Df× Df �Df −1�

�1+1/q2�2��Df−1�/2

× sin�Df −1� tan−1q�� (3)

where �x� is the Gamma function with argument x, Df

is the mass fractal dimension (1 <Df < 3), � is upper cut-off length (maximum length up to which fractal structureexists) and ro is the size of primary particles. In presentcase, it has been assumed that basic primary particle sizeof the fractal aggregates (building blocks of the aggregate)is of the order of the CNTs cross-sectional radius (r0�.This method explains data well for BCNT, NiCNT andCuCNT specimens. The fitting parameters obtained fromthis model have been tabulated in Table IV. The fit of thismodel to the data for BCNT, NiCNT and CuCNT samplesare depicted in the Figure 13.

From the Figure 13, it is clear that the functionality ofSANS profiles for FeCNT is significantly different fromthose of BCNT, NiCNT and CuCNT. Profile for FeCNTsamples is not showing any linear region over an extendedq range in the log–log plot of the SANS profiles, indi-cating different structural features as compared to thoseof BCNT, NiCNT and CuCNT specimens. From the TEM


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Fig. 12. Different EDAX spectrums showing carbon and nickel peaksin FeCNT.

micrograph (Fig. 6) of FeCNT, it is also evident thatFeCNT shows agglomerated structure of Fe nano-particlewith no clear visible tubular structure. Thus, in FeCNTspecimen, the agglomerates of iron nano-particles domi-nate over the typical chain cluster (fractal) type morphol-ogy of MWNTs. It suggests that agglomerated structuresof iron nano-particle are shadowing the scattering contri-bution of the MWNTS in the scattering profile. To seethe contribution of the scattering originating solely fromthe Fe nano-particle agglomerates of FeCNT specimen, wehave subtracted the BCNT scattering profile from FeCNTscattering profile (Fig. 14). This shows that the major scat-tering contribution in the SANS profile is coming due tothe agglomerates of Fe nano-particles. In the light of above

10–3 10–2 10–110–5

10–2

101

104

BCNTNiCNT

CuCNT

FeCNT

Model fit

Inte

nsity

(ar

b. s

cale

)

q (nm–1)

Fig. 13. SANS profiles from acid treated MWNTs specimens andMWNTs-nano-particle composites. The profiles are shifted vertically inorder to represent the fit clearly.

Table I. Concentration of Ni in NiCNT in atomic %.

Spectrum C Ni

Spectrum 1 90.82 9�18Spectrum 2 97.27 2�73Spectrum 3 97.48 2�52Spectrum 4 98.63 1�37Spectrum 5 85.54 14�46Mean 93.95 6�05

Table II. Concentration of Cu in CuCNT in atomic %.

Spectrum C Cu

Spectrum 1 75.31 24�52Spectrum 2 92.81 6�41Mean 84.06 15�46

fact, the SANS data for FeCNT specimen have been ana-lyzed as agglomerates of polydisperse spherical Fe nano-particles. The scattered intensity can be written as,

Iq�= C

[∫DR�V 2R�Psq�R�dR

]Ssq� rav� (4)

where Ps(q, r) is form factor for spherical particles and isgiven by,

Psq� r�= 9[

sinqr�−qr cosqr�

qr�3

]2

(5)

Ss(q, rav) is structure factor for agglomerates. For simplic-ity, we have considered S(q) of a mass fractal as men-tioned above. Thus, scattering profile from FeCNT consistsof two parts, the first contribution is scattering from theMWNTs network and the second contribution is due to thescattering from the agglomerates of spherical Fe particles.Scattering contribution from Fe agglomerates is dominant

Table III. Concentration of Fe in FeCNT in atomic %.

Spectrum C Fe

Spectrum 1 83.81 16�19Spectrum 2 98.96 1�04Spectrum 3 92.53 7�47Mean 91.77 8�23

Table IV. Parameters obtained by fitting the SANS profiles.

CNTsagglomerate Fractal dimension (Df ) Cross sectionmodel of CNT agglomerates radius (r0� (nm)

BCNT 1.24 26.5NiCNT 1.28 22.1CuCNT 1.23 22.0

Fe nano-particle Fractal dimension (Df � Av. Fe nano-particle Fe agglomerateagglomerate of agglomerates of Fe particle radius (nm) size (nm)

FeCNT 2.2 13.5 69.0


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10–3 10–2 10–1

102

103

104

105

106

FeCNT

BCNTContribution from Fe agglomerates(FeCNT-BCNT)

Inte

nsity

(arb

. sca

le)

q (nm–1)

Fig. 14. SANS profile for FeCNT and BCNT. The scattering contribu-tion solely from the Fe agglomerates is derived by subtracting the abovetwo scattering profiles.

as compared to the contribution from of MWNTs alone.The agglomerate size is calculated from the SANS profilewhich is found to be ∼69 nm. From the TEM micrograph,Figure 6, the agglomerate size is seen to be of the sameorder as obtained by SANS.

(a)

(b)

(c)

Fig. 15. A covalent approach to decorate CNTs by metal nano-particles. In first step (a), CNTs were treated with HNO3. This process creates activecenters (acidic sites and defects) at the surface of CNTs. In second process (b) these active centers act as nucleating centers and the nano-particlesnucleates and grows on these sites. But, in case of Fe (c) nano-particles due to strong agglomeration nature, forms agglomerate.

From the SANS data analysis, it is evident that themesoscopic structure of the Ni and Cu nano-particle-MWNTS composites remain more or less same asMWNTs (BCNT) in the probes length scale. Fromthe TEM micrographs (Figs. 2, 3, 4 and 5), it is found thatthe Ni and Cu nano-particle are attached on the wall of theMWNTs. Here, it is important to mention that because ofthe limitation in accessibility of higher q range, informa-tion about the size of the nano-particles which are attachedat the walls of the CNTs in case of CUCNT and NICNTcould not be obtained.

As mentioned earlier, SANS profile (Fig. 13) forFECNT is significantly different in functionality in com-parison to BCNT, NICNT and CUCNT which indicatesa significant modification of the morphology, which isattributed to the high agglomeration nature of the magneticFe nano-particle.

An attempt has been made to suggest a possible mecha-nism to explain the aforementioned experimental observa-tions below. CNTs are typically chemically inert. Covalentattachment of molecular species to fully sp2-bonded car-bon atoms on the nanotube sidewalls proves to be difficult.But oxidation of the nano-tubes modifies the side-wall(inner as well as outer wall) by creating acidic centres(–COOH, –OH). This process also creates defect on the


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side wall of the carbon nanotubes. These active centres actas nucleation centres on the carbon nanotube side wall.It is interesting to mention at this juncture that covalentchemical approach, however, may disrupt the intrinsicmechanical and electrical properties of a carbon nano-tube. The mechanism by which the defects or vacancieson carbon nanotube may facilitates for nucleation centresas follows. For examples, theoretical studies suggest thatNi atoms on CNT surface may interact with vacancies; theenergy for substitution of a C atom by a Ni atom in agraphene sheet was estimated to be 9.5 eV while Ni atomsinteract with vacancies with a strong adsorption bond of−4.7 eV (minimum energy gain associated with the sat-uration of the three dangling bonds in graphite by a Niatom when filling an existing vacancy).64 Based on theabove discussion, it can be suggested that Ni decorationof MWNTs involves first the adsorption of Ni atoms ontothe surface, followed by diffusion of these adsorbed atomsacross the surface until nucleation of islands occurs whendiffusing adsorbed atoms form a stable nucleus. After theformation of stable nuclei at nucleation centres, the nextincoming adatoms can either attach to an existing nucleusor diffuse on the surface until they encounter anotheradatom to form a new stable nucleus. The density of nucle-ation centers depends on the interaction between adsorbedatoms and the substrate; considering the strong adsorptionbond between Ni atoms and C vacancies, such defects willbe the principal nucleation sites.

Similarly, the metal nano-particle may attach at theacidic centres created by the oxidation of the carbon nano-tube. These acidic sites will act as nucleating centres formetal nano-particles. The fictionalization of carbon nano-tubes by covalent method have been depicted pictorially(Fig. 15).

The above described mechanisms are responsible toobtain the nano-particle (Ni and Cu) decorated MWNTSin the NiCNT and CuCNT specimens.

As the SANS and TEM data shows that due to highagglomeration nature of the Fe nano-particle, Fe decoratedcarbon nanotube could not be achieved. The agglomera-tion of the Fe nano-particle may be attributed to its highmagnetic moment. Thus, the agglomeration of Fe nano-particle is a serious issue due to strong attractive inter-action. It is also to be noted that, the reactivity of theFe nano-particle is another important issue to get pure Fenano-particle decorated MWNTs. Our next effort will beto synthesize Fe-decorated MWNTs by reduction of theiron salt in presence of a surfactant that may prevent thewholesale agglomeration of the Fe nano-particles.

4. CONCLUSIONS

Metal (Ni, Cu) nano-particles decorated MWNTs weresynthesize by wet chemical method. SANS and TEMreveal the chain cluster type of morphology of the

MWNTs. Wall decoration using Ni and Cu nano-particlescould be achieved by wet chemical method. Fe-decoratedMWNTs could not be achieved by wet chemical methoddue to the severe agglomeration of the magnetic Fe nano-particle before its nucleation at active centers at CNT walldue to strong dipolar interaction. In near future, decora-tion of CNT walls by Fe nanoparticles will be attemptedby reduction of the iron salt in presence of a surfactantthat may prevent the wholesale agglomeration of the Fenano-particles within the experimental limitations.

References and Notes

1. S. Iijima, Nature 354, 56 (1991).2. T. W. Ebbesen and P. M. Ajayan, Nature 358, 220 (1992).3. M. S. Dresselhaus, G. Dresselhaus, and Ph. Avouris, Carbon Nano-

tubes: Synthesis, Structure, Properties and Applications, Springer,Berlin (2001).

4. G. G. Wildgoose, C. E. Banks, and R. G. Compton, Small 2, 182(2006).

5. M. Baibarac and P. Gómez-Romero, J. Nanosci. Nanotechnol. 6, 289(2006).

6. Y. Lin, S. Taylor, H. Li, K. A. Fernando Shiral, L. Qu, W. Wang,L. Gu, B. Zhou, and Y. P. Sun, J. Mater. Chem. 14, 527 (2004).

7. J. M. Planeix, N. Coustel, B. Coq, V. Bretons, P. S. Kumbhar,R. Dutartre, P. Geneste, P. Bernier, and P. M. Ajayan, J. Am. Chem.Soc. 116, 7935 (1994).

8. R. Yu, L. Chen, Q. Liu, J. Lin, K. L. Tan, S. C. Ng, H. S. O. Chan,G. Q. Xu, and T. S. A. Hor, Chem. Mater. 10, 718 (1998).

9. J. Kong, M. Chapline, and H. Dai, Adv. Mater. 13, 1384 (2001).10. Z. Liu, X. Lin, J. Y. Lee, W. Zhang, M. Han, and L. M. Gan,

Langmuir 18, 4054 (2002).11. C. Wang, M. Waje, X. Wang, J. M. Tang, R. C. Haddon, and Y. Yan,

Nano Lett. 4, 345 (2004).12. Y. Lin, X. Cui, C. Yen, and C. M. Wai, J. Phys. Chem. B 109, 14410

(2005).13. L. Qu and L. Dai, J. Am. Chem. Soc. 127, 10 806 (2005).14. J. M. Haremza, M. A. Hahn, T. D. Krauss, S. Chen, and J. Calcines,

Nano Lett. 2, 1253 (2002).15. W. Q. Han and A. Zettl, Nano Lett. 3, 681 (2003).16. J. Shi, Y. Qin, W. Wu, X. Li, Z. X. Guo, and D. B. Zhu, Carbon 42,

455 (2004).17. L. Fu, Z. M. Liu, Y. Q. Liu, B. X. Han, P. A. Hu, L. C. Cao, and

D. B. Zhu, Adv. Mater. 17, 217 (2005).18. I. Robel, B. A. Bunker, and P. V. Kamat, Adv. Mater. 17, 2458

(2005).19. E. A. Whitsitt and A. R. Barron, Nano Lett. 3, 775 (2003).20. T. Sainsbury and D. Fitzmaurice, Chem. Mater. 16, 3780 (2004).21. W. Fan and L. Gao, Chem. Lett. 34, 954 (2005).22. Y. T. Kim, K. Ohshima, K. Higashimine, T. Uruga, M. Takata,

H. Suematsu, and T. Mitani, Angew. Chem. Int. 45, 407 (2006).23. E. V. Basiuk, E. V. Rybak-Akimova, V. A. Basiuk, D. Acosta-

Najarro, and J. M. Saniger, Nano Lett. 2, 1249 (2002).24. T. Yokoi, S. Iwamatsu, S. Komai, T. Hattori, and S. Murata, Carbon

43, 2869 (2005).25. J. E. Riggs, Z. Guo, D. L. Carroll, and Y. P. Sun, J. Am. Chem. Soc.

122, 5879 (2000).26. A. Eitan, K. Jiang, D. Dukes, R. Andrews, and L. S. Schadler, Chem.

Mater. 15, 3198 (2003).27. M. Shim, N. W. S. Kam, R. J. Chen, Y. Li, and H. Dai, Nano Lett.

2, 285 (2002).28. C. Richard, F. Balavoine, P. Schultz, T. W. Ebbesen, and

C. Mioskowski, Science 300, 775 (2003).


https://www.researchgate.net/publication/232789484_Large-Scale_synthesis_of_carbon_nanotubes?el=1_x_8&enrichId=rgreq-a6372237a02d2bc1a7129bdeb76baa62-XXX&enrichSource=Y292ZXJQYWdlOzQyODMyMTE2O0FTOjEwNjM3ODIwNzE3MDU2MEAxNDAyMzczOTQ5NjQ3

RESEARCHARTICLE


29. H. C. Choi, M. Shim, S. Bangsaruntip, and H. Dai J. Am. Chem.Soc. 124, 9058 (2002).

30. Y. Zhang and H. Dai, Appl. Phys. Lett. 77, 3015 (2000).31. T. Yokoi, S. Iwamatsu, S. Komai, T. Hattori, and S. Murata, Carbon

43, 2869 (2005).32. J. E. Riggs, Z. Guo, D. L. Carroll, and Y. P. Sun, J Am. Chem. Soc.

122, 5879 (2000).33. A. Eitan, K. Jiang, D. Dukes, R. Andrews, and L. S. Schadler, Chem.

Mater. 15, 3198 (2003).34. J. L. Stevens, A. Y. Huang, H. Peng, I. W. Chiang,

V. N. Khabashesku, and J. L. Margrave, Nano Lett. 3, 331 (2003).35. J. L. Bahr, J. Yang, D. V. Kosynkin, M. J. Bronikowski,

R. E. Smalley, and J. M. Tour, J. Am. Chem. Soc. 123, 6536 (2001).36. V. Georgakilas, K. Kordatos, M. Prato, D. M. Guldi, M. Holzinger,

and A. Hirsch, J. Am. Chem. Soc. 124, 760 (2002).37. D. E. Hill, Y. Lin, A. M. Rao, L. F. Allard, and Y. P. Sun,

Macromolecules 35, 9466 (2002).38. Y. Lin, A. M. Rao, B. Sadanadan, E. A. Kenik, and Y. P. Sun,

J. Phys. Chem. B 106, 1294 (2002).39. W. Huang, S. Taylor, K. Fu, Y. Lin, D. Zhang, T. W. Hanks, A. M.

Rao, and Y. P. Sun, Nano. Lett. 2, 311 (2002).40. K. A. Williams, P. T. M. Veenhuizen, B. G. D. Torre, R. Eritja, and

C. Dekker, Nature 420, 761 (2002).41. S. C. Tsang, P. J. F. Harris, and M. L. H. Green, Nature 362, 520

(1993).42. B. C. Satishkumar, M. Vogl Erasmus, A. Govindaraj, and C. N. R.

Rao, J. Phys. D: Appl. Phys. 29, 3173 (1996).43. W. Howard, Z. Wei, L. H. Derek, I. W. Karen, E. F. John, J. G.

Charles, and K. H. Erik, Nano Letters 4, 1789 (2004).44. D. W. Schaefer, J. Zhao, J. M. Brown, D. P. Anderson, and D. W.

Tomlin, Chemical Physics Letters 375, 369 (2003).45. R. S. Justice, D. H. Wang, L.-S. Tan, and D. W. Schaefer, J. Appl.

Cryst. 40, s88 (2007).46. J. B. Barry, K. H. Erik, and L. B. Matthew, Macromolecules 39,

2637 (2006).

47. K. Yurekli, C. A. Mitchell, and R. Krishnamoorti, J. Am. Chem. Soc.126, 9902 (2004).

48. J. J. Hernández, G. M. C. Garcia, A. Nogales, D. R. Rueda, and T.A. Ezquerra, Composites Science and Technology 66, 2629 (2006).

49. K. Dasgupta, D. Sen, S. Mazumder, C. B. Basak, J. B. Joshi, andS. Banerjee, J. Nanosci. and Nanotechnol. (2009), In press.

50. J. Bahadur, D. Sen, S. Mazumder, and S. Ramanathan J. Solid StateChem. 181, 1227 (2008).

51. J. Bahadur, D. Sen, S. Mazumder, R. Shukla, and A. K. Tyagi,J. Phys.: Condens. Matter 20, 345201 (2008).

52. D. Sen, J. Bahadur, S. Mazumder, V. Bedekar, and A. K. Tyagi,J. Phys.: Condens. Matter 20, 035103 (2008).

53. D. Sen, K. Dasgupta, J. Bahadur, S. Mazumder, andD. Sathiyamoorthy, PRAMANA-Journal of Physics 71, 971 (2008).

54. S. Mazumder, D. Sen, A. K. Patra, S. A. Khadilkar, R. M. Cursetji,R. Loidl, M. Baron, and H. Rauch, Phys. Rev. Lett. 93, 255704(2004).

55. J. M. Cowley and F. A. Sundell, Ultramicroscopy 68, 9000(1997).

56. M. Monthioux, B. W. Smith, B. Burteaux, A. Claye, J. E. Fischer,and D. E. Luzzi, Carbon 39, 1251 (2001).

57. A. G. Rinzler, J. Liu, H. Dai, P. Nikolaev, C. B. Huffman, F. J.Rodriguez-Macias, P. J. Boul, A. H. Lu, D. Heymann, D. T. Colbert,R. S. Lee, J. E. Fischer, A. M. Rao, P. C. Eklund, and R. E. Smalley,J. Appl. Phys. A 67, 29 (1998).

58. (a) D. W. Schaefer, Science 243, 1023 (1989); (b) B. B Mandelbrot,The Fractal Geometry of Nature, Freeman, New York (1982).

59. S. Mazumder, D. Sen, T. Sarvanan, and P. R. Vijayraghavan, J. Neu-tron Research 9, 39 (2001).

60. J. A. Lake, J. Appl. Cryst. 23, 191 (1967).61. M. Foret, J. Pelous, and R. Vacher, J. Phys. I France 2, 79 (1992).62. J. Teixeira, J. Appl. Cryst. 21 ,781 (1988).63. T. Freltoft, J. K. Jems, and S. K. Sinha, Phys. Rev. B 33, 269 (1986).64. F. Banhart, J. C. Charlier, and P. M. Ajayan, Phys. Rev. Lett. 84, 686

(2000).

Received: 7 May 2009. Accepted: 16 June 2009.


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https://www.researchgate.net/publication/232800812_Thinning_and_Opening_of_Carbon_Nanotubes_by_Oxidation_Using_Carbon_Dioxide?el=1_x_8&enrichId=rgreq-a6372237a02d2bc1a7129bdeb76baa62-XXX&enrichSource=Y292ZXJQYWdlOzQyODMyMTE2O0FTOjEwNjM3ODIwNzE3MDU2MEAxNDAyMzczOTQ5NjQ3

decoration of carbon nanotubes with metal nanoparticles by wet chemical method: a small-angle...

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