research article novel method of evaluating the purity of...

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2013 Article ID 615915 6 pageshttpdxdoiorg1011552013615915

Research ArticleNovel Method of Evaluating the Purity of Multiwall CarbonNanotubes Using Raman Spectroscopy

Young Chul Choi1 Kyoung-In Min2 and Mun Seok Jeong34

1 CNT Team Hanwha Chemical 80 Annamro 402 gil Bupyeong-gu Incheon 403-030 Republic of Korea2 Spectro Gwangju 500-712 Republic of Korea3 Center for Integrated Nanostructure Physics Institute for Basic Science Sungkyunkwan UniversitySuwon 440-746 Republic of Korea

4Department of Energy Science Sungkyunkwan University Suwon 440-746 Republic of Korea

Correspondence should be addressed to Mun Seok Jeong mjeongskkuedu

Received 15 October 2013 Accepted 29 October 2013

Academic Editor Clare C Byeon

Copyright copy 2013 Young Chul Choi et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

We propose the quantitativemethod of evaluating the purity ofmultiwall carbon nanotubes (MWCNTs) usingRaman spectroscopyHigh purityMWCNTswere prepared by chemical vapor deposition (CVD) to be used as a referencematerial with 100purity Sincethe intensity and wavenumber ofD10158401015840-band located at around 1500 cmminus1 were found to be independent of the excitation wavelengthof a laser the purity of MWCNTs was measured by comparing the intensity ratio of D10158401015840-band to G-band (119868

11986310158401015840 119868119866) of the sample

with that of a reference material The established method was verified by testing the mixture of amorphous carbon particles andreference MWCNTs

1 Introduction

Since multiwall carbon nanotubes (MWCNTs) possess highelectrical conductivity high thermal conductivity and excel-lent mechanical properties [1ndash3] they have been exten-sively studied for being used in the electrical thermal andmechanical applications [4ndash7] In order to achieve bettercharacteristics of application products the advancement inthe synthesis technology has been tried to improve theproperties ofMWCNTs including crystallinity dispersibilityand purity [8ndash10] Among these characteristics purity isone of the most important properties from the viewpointof better performance of application products In additionsince higher purity means that a smaller amount of CNTs isrequired to achieve targeted properties it is very importantfor industrial applications to use high purity MWCNTs interms of low cost Many researchers have used thermo-gravimetric analysis (TGA) [11ndash13] and 119863-band to 119866-bandintensity ratio of Raman spectrum (119868

119863119868119866) [14] to measure

the purity of MWCNTs However TGA represents the wholecarbon content in the sample because measuring the weight

loss with increasing temperature does not distinguish carbonnanotubes from other carbon species Meanwhile apart fromthe fact that the intensity and position of 119863-band peak arevaried with the excitation wavelength of a laser to a greatextent [15] 119863-band originates from not only amorphouscarbon particles but also nanotube-related aspects includingdefects in the curved graphene sheets tube ends and finitesize of crystalline domains of the tubes [16] Thus themeasurement of (119868

119863119868119866) is not useful for evaluating the purity

of MWCNTs using various wavelengths of laser In contrastto 119863-band the intensity and position of 11986310158401015840 band are notvaried with the wavelength of laser Moreover 11986310158401015840-bandoriginates from only amorphous carbons [17] Therefore wepropose here the quantitativemethod evaluating the purity ofMWCNTs using the11986310158401015840-band Raman spectrum ofMWCNTsas a signal for amorphous carbon particles

As-synthesizedMWCNTs are in general composed of thenanotubes catalyst particles and amorphous carbonaceousparticles Since the crystallinity of MWCNTs observed fromRaman spectroscopy is clearly distinguishable from that ofamorphous carbons we used the comparison of Ramanpeaks

2 Journal of Nanomaterials

(a)

500 1000 1500 2000 2500 3000

G-band

D-band

Inte

nsity

(au

)

D998400998400-band

D998400-band

Raman shift (cmminus1)

(b)

Figure 1 (a) SEM image of referenceMWCNTswith 100purity Inset shows theHRTEM image of referenceMWCNTs (b) Raman spectrumof reference MWCNTs

observed fromMWCNTs and amorphous carbons for evalu-ating the purity ofMWCNTs A high purityMWCNT-samplewas prepared and then used as a reference material Thepurity was evaluated from comparing 11986310158401015840-band to 119866-bandintensity ratio (119868

11986310158401015840119868119866) of sample with 119868

11986310158401015840119868119866of reference

materials MWCNTs have been synthesized by either arc-discharge [18 19] or chemical vapor deposition (CVD) [1ndash10] Since the MWCNTs synthesized by arc-discharge havehigher crystallinity 11986310158401015840-band is scarcely seen in the Ramanspectrum Therefore the method to be introduced in thisreport is useful for only CVD-grown MWCNTs But theMWCNTs synthesized by arc-discharge are not used in thepractical applications due to the impossibility of mass pro-ductionTherefore it is still worthy of developing themethodhave evaluating the purity of CVD-grownMWCNTs that areunexceptionally shown11986310158401015840-band in the Raman spectrumWewill provide the detailed protocols for determining the purityof CVD-grown MWCNTs which are confirmed by testingthe mixture of high purity MWCNTs and amorphous carbonparticles

2 Experimental

In order to synthesize MWCNTs FeMoAl2O3particles

were prepared using combustion method FeMo particleswere used as catalysts and Al

2O3was supporting the cata-

lysts Metal-organic precursors of iron nitrate molybdenumacetate and aluminum nitrate were dissolved in deionizedwater and then the prepared solution was transformed intocatalyst powder by thermal treatment at 450∘C for 30minin air ambient The quartz boat having the catalyst powderwas placed inside a quartz tube reactor After heating thereactor to 700∘C in Ar atmosphere a gas mixture of C

2H4H2

(1 1) was fed into the reactor with a pressure of 1 atm for thesynthesis followed by cooling to room temperature under Aratmosphere

The morphologies of MWCNTs were investigated usingscanning electron microscopy (SEM JEOL JSM 6700F) and

transmission electron microscopy (TEM FEI Tecnai 20200 kV) The amount of catalyst particles included in thesynthesized MWCNT samples was investigated by TGAAmorphous carbon powder was purchased from Aldrichto be used as an impurity material In order to verify theproposed evaluation method several intermediate puritysamples having the purity range of 0ndash100 with 20interval were prepared by mixing high purity MWCNTsand amorphous carbon powder considered as 100 and 0respectively Then Raman spectroscopy measurement wascarried out to evaluate the purity ofMWCNTs using a Ramanmicroscope (TRIVIA Acton)

3 Results and Discussion

Through optimizing the experimental parameters for thesynthesis of MWCNTs we prepared very high purity MWC-NTs as can be seen in Figure 1(a) Despite of a number ofobservations using SEM we could not see carbonaceous par-ticles TEM image (inset figure) clearly shows the synthesizedmaterials are all of MWCNTs with hollow insides Accordingto TGA analysis two weight-percent (wt) of catalyst metalparticles is included in the prepared MWCNTs However wecould hardly see the catalyst particles during both SEM andTEM observations It is believed that 2 wt of catalyst parti-cles corresponds to an extremely small volume percent thatcould be negligible because the bulk density of catalyst parti-cle is much larger than that of MWCNTs Furthermore mostof the catalyst particles are residing insideMWCNTs after thesynthesis [20] which does not affect Raman spectrumThere-fore this high purity MWCNTs could be considered as a ref-erence material with 100 purity Figure 1(b) represents theRaman spectrum of a reference MWCNT sample The spec-trum was taken using an excitation wavelength of 633 nmThe Raman spectrum shows a typical feature of MWC-NTs the first ordered 119863- 119866- and 1198631015840-band peaks locatedat around 1350 1582 and 1610 cmminus1 respectively 119866-bandpeak is assigned to ldquoin planerdquo displacement of the carbons

Journal of Nanomaterials 3

2120583m

(a)

2120583m

(b)

2120583m

(c)

2120583m

(d)

2120583m

(e)

2120583m

(f)

Figure 2 SEM images of purity-controlled MWCNT samples by mixing amorphous carbon particles and highly pure MWCNTs (a) 0 (b)20 (c) 40 (d) 60 (e) 80 and (f) 100

strongly coupled in the hexagonal sheets [17] 119863- and 1198631015840-band are found when disorder is introduced into the graphitestructure For this reason the intensity ratio of119863-band to 119866-band (119868

119863119868119866) has been used to determine the crystallinity of

MWCNTs [15 20] However according to Behler et al [15]the intensity and position of119863-band peak are varied with theexcitation wavelength of laser to a great extentTherefore themeasurement of 119868

119863119868119866cannot be used as a standard method

for evaluating the crystallinity of MWCNTs although 119868119863119868119866

is used to compare the crystallinity of carbon nanotubeswhen the identical wavelength is used Another broad peak(11986310158401015840-band) located at around 1500 cmminus1 is also found in theRaman spectrum (Figure 1(b)) 11986310158401015840-band was reported tobe associated with amorphous 1199041199012-bonded forms of carbon[21 22] Unlike 119868

119863119868119866 the intensity ratio of 11986310158401015840-band to 119866-

band (11986811986310158401015840119868119866) was found to be invariable with the excitation

wavelength of laser In addition 11986310158401015840-band is associated withonly amorphous carbons Hence we suggest 119868

11986310158401015840119868119866instead

of 119868119863119868119866

to be used for representing the crystallinity ofcarbon nanotubes 119868

11986310158401015840119868119866of the reference samples obtained

from Figure 1(b) is 006 On the other hand 11986811986310158401015840119868119866

ofamorphous carbon particles that was purchased fromAldrichis 037 We suggest that 119868

11986310158401015840119868119866of the high purity MWCNTs

(006) and amorphous carbons (037) should represent thepurities of 100 and 0 respectivelyTherefore the purity ofMWCNTs (119875MW) can be simply determined by an equation of

119875MW () = (AC (11986310158401015840119866) minusMW (11986310158401015840119866)AC (11986310158401015840119866) minus RMW (11986310158401015840119866)

) times 100 (1)

where AC(11986310158401015840119866) MW(11986310158401015840119866) and RMW(11986310158401015840119866) are11986310158401015840119866ratios of amorphous carbon particlesMWCNTs being testedand reference MWCNTs respectively In order to verifythe suggested equation intermediate purity samples werepreparedwith 20purity interval from0 to 100bymixinghigh purity MWCNTs and amorphous carbon particles


1008060

40200

Inte

nsity

(au

)

500 1000 1500 2000 2500 3000Raman shift (cmminus1)

(a)

Constructed MWCNT content ()

Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100

(b)

Figure 3 (a) Raman spectra taken using an excitation wavelength of 633 nm of purity-controlled MWCNT samples with purities rangingfrom 0 to 100 with 20 interval (b) Purity measured from Raman spectroscopy using 633 nm laser versus constructed content ofMWCNTs

First we dispersed the MWCNTs and amorphous carbonparticles in the dimethylformamide (DMF) separately with1mg100ml concentration Then two solutions were mixedwith designed ratiosThemixed solutions were dropped ontoglass and Si substrates for the analyses by Raman and SEMrespectively Figure 2 shows the SEM images of several inter-mediate purity samples It can be clearly observed from thesefigures that the amount of impurity decreases as the purity ofMWCNT increases However it is hard to define the purityof samples quantitatively by using SEMmeasurements

Six different intermediate samples preparedwith differentpurities (0ndash100) were analyzed by Raman spectroscopyFigure 3(a) shows the Raman spectra taken using an excita-tion wavelength of 633 nm of MWCNTs with various puri-ties 100 and 0 purity samples show the Raman spectraof reference MWCNTs and amorphous carbons respectivelyAlthough the deconvoluted peaks of 0 purity sample arenot presented here it was found that the Raman spectrumof 0 purity sample is composed of not only conventional119863-and 119866-bands but also11986310158401015840-band with a considerable intensityWith increasing the purity of MWCNTs full width at thehalf maximum (FWHM) of the peak at 1200ndash1400 cmminus1 (119863 +11986310158401015840-bands) decreases because the contribution of 11986310158401015840-band

is getting smaller We applied the proposed equation to theseries of MWCNT samples with intentionally varied purityand the results are illustrated in Figure 3(b) Figure 3(b) plotsthe purity evaluated using the equation to the constructedcontents with varying purities from 0 to 100 The linearfitting yielded a slope close to unity 096 and the confidencevalue 1198772 was 095 Thus the evaluated purities of MWCNTsare in good agreement with the designed values of con-structed content It can be therefore said that the suggested

equation can be simply used for evaluating the purity ofMWCNTs

Various lasers with different excitation wavelengths areused in Raman spectroscopy Therefore in order to stan-dardize an evaluation method using Raman spectroscopythe method should not be dependent upon the excita-tion wavelength A number of previous literatures reportedthe crystallinity of carbon nanotubes determined from theintensity ratio of 119863-band (sim1350 cmminus1) to 119866-band (119868

119863119868119866)

However the measurement of 119868119863119868119866cannot be used as a

standardized evaluation method since the intensity of 119863-band is significantly dependent upon the wavelength of laser[15] In this study we measured the purities of several differ-ent samples by using the excitation wavelength of not only633 nm shown in Figure 3(b) but also 532 nm to verify theindependency of this method on the wavelength Generally633 nm and 532 nm laser are widely used for the Ramanscattering measurement of MWCNTs Figure 4 representsthe purities evaluated from the Raman spectra taken using532 nm laser as a function of constructed content 119868

11986310158401015840119868119866

obtained using an excitation wavelength of 532 nm of highpurity reference MWCNTs and amorphous carbon particleswas 007 and 049 respectively Although 119868

11986310158401015840119868119866measured

using 532 nm laser is slightly different from that obtainedusing 633 nm laser the purity measured using an excitationwavelength of 532 nm is also well matched to the constructedcontent as can be seen in Figure 4The linear fitting yielded aslope of 103 and the confidence value 1198772 was 096 Thus thepurities of MWCNTs evaluated using excitation wavelengthof 532 nm are also in good agreement with the designedvalues of constructed content It can be therefore concludedthat evaluating the purity of MWCNTs using 119868

11986310158401015840119868119866is valid

regardless of excitation wavelength of laser



Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100

Figure 4 Purity measured from Raman spectroscopy using anexcitation wavelength of 532 nm versus constructed content ofMWCNTs

4 Conclusion

A quantitative method for evaluating the purity of MWCNTsusing Raman spectroscopywas newly proposedThe purity ofMWCNTs was determined by comparing the intensity ratioof 11986310158401015840-band to 119866-band (119868

11986310158401015840119868119866) of MWCNTs being tested

with that of the high purity reference material The estab-lishedmethodwas verified by testing themixture of referenceMWCNTs of high purity and amorphous carbon particlesFurthermore it was found that the proposed method wasfound to be valid regardless of the excitation wavelength oflaser

Acknowledgment

This work was supported by Institute for Basic Science (IBS)(EM1304)

References

[1] L J Cui H Z Geng W Y Wang L T Chen and J GaoldquoFunctionalization of multi-wall carbon nanotubes to reducethe coefficient of the friction and improve the wear resistanceof multi-wall carbon nanotubeepoxy compositesrdquo Carbon vol54 pp 277ndash282 2013

[2] Y J NohH S Kim and S Y Kim ldquoImproved electrical conduc-tivity of a carbon nanotube mat composite prepared by in-situpolymerization and compression molding with compressionpressurerdquo Carbon Letters vol 13 no 4 pp 243ndash247 2012

[3] Y C Choi YM Shin Y H Lee et al ldquoControlling the diametergrowth rate and density of vertically aligned carbon nanotubessynthesized by microwave plasma-enhanced chemical vapordepositionrdquo Applied Physics Letters vol 76 no 17 pp 2367ndash2369 2000

[4] S Akita Y Ohshima and T Arie ldquoNanoincandescent consist-ing of individual carbon nanotubesrdquo Applied Physics Expressvol 4 no 2 Article ID 025101 2011

[5] C T Chang C-P Juan and H-C Cheng ldquoPillar heightdependence of field-emission properties in an array of carbon

nanotube pillarsrdquo Japanese Journal of Applied Physics vol 52 no18 Article ID 085101 2013

[6] A Mierczynska M Mayne-LrsquoHermite G Boiteux and JK Jeszka ldquoElectrical and mechanical properties of carbonnanotubeultrahigh-molecular-weight polyethylene compos-ites prepared by a filler prelocalization methodrdquo Journal ofApplied Polymer Science vol 105 no 1 pp 158ndash168 2007

[7] F L Jin and S J Park ldquoRecent advances in carbon-nanotube-based epoxy compositesrdquo Carbon Letters vol 14 no 1 pp 1ndash132013

[8] J S Kim S J Cho K S Jeong Y C Choi and M SJeong ldquoImproved electrical conductivity of very long multi-walled carbon nanotube bundlepoly (methyl methacrylate)compositesrdquo Carbon vol 49 no 6 pp 2127ndash2133 2011

[9] Y C Choi Y M Shin S C Lim et al ldquoEffect of surfacemorphology of Ni thin film on the growth of aligned carbonnanotubes by microwave plasma-enhanced chemical vapordepositionrdquo Journal of Applied Physics vol 88 no 8 pp 4898ndash4903 2000

[10] Y S Park H S Moon M Huh et al ldquoSynthesis of alignedand length-controlled carbon nanotubes by chemical vapordepositionrdquo Carbon Letters vol 14 no 2 pp 99ndash104 2013

[11] P Mahanandia P N Vishwakarma K K Nanda et al ldquoSynthe-sis of multi-wall carbon nanotubes by simple pyrolysisrdquo SolidState Communications vol 145 no 3 pp 143ndash148 2008

[12] J H Lehman M Terrones E Mansfield K E Hurst and VMeunier ldquoEvaluating the characteristics of multiwall carbonnanotubesrdquo Carbon vol 49 no 8 pp 2581ndash2602 2011

[13] J P C Trigueiro GG Silva R L Lavall et al ldquoPurity evaluationof carbon nanotube materials by thermogravimetric TEM andSEMmethodsrdquo Journal of Nanoscience andNanotechnology vol7 no 10 pp 3477ndash3486 2007

[14] R ADiLeo B J Landi andR P Raffaelle ldquoPurity assessment ofmultiwalled carbon nanotubes by Raman spectroscopyrdquo Journalof Applied Physics vol 101 no 6 Article ID 064307 2007

[15] K Behler S OsswaldH Ye S Dimovski andYGogotsi ldquoEffectof thermal treatment on the structure of multi-walled carbonnanotubesrdquo Journal of Nanoparticle Research vol 8 no 5 pp615ndash625 2006

[16] W Li H Zhang C Wang et al ldquoRaman characterization ofaligned carbon nanotubes produced by thermal decompositionof hydrocarbon vaporrdquo Applied Physics Letters vol 70 no 20pp 2684ndash2686 1997

[17] T Jawhari A Roid and J Casado ldquoRaman spectroscopiccharacterization of some commercially available carbon blackmaterialsrdquo Carbon vol 33 no 11 pp 1561ndash1565 1995

[18] Y S Park Y C Choi K S Kim et al ldquoHigh yield purificationof multiwalled carbon nanotubes by selective oxidation duringthermal annealingrdquo Carbon vol 39 no 5 pp 655ndash661 2001

[19] X Song Y Liu and J Zhu ldquoMulti-walled carbon nanotubesproduced by hydrogen DC arc discharge at elevated environ-ment temperaturerdquoMaterials Letters vol 61 no 2 pp 389ndash3912007

[20] Z Balogh G Halasi B Korbely and K Hernadi ldquoCVD-synthesis of multiwall carbon nanotubes over potassium-dopedsupported catalystsrdquo Applied Catalysis A vol 344 no 1-2 pp191ndash197 2008


[21] D S Knight and W B White ldquoCharacterization of diamondfilms by Raman spectroscopyrdquo Journal of Materials Researchvol 4 no 2 pp 385ndash393 1989

[22] P V Huong ldquoStructural studies of diamond films and ultrahardmaterials by Raman and micro-Raman spectroscopiesrdquo Dia-mond and Related Materials vol 1 no 1 pp 33ndash41 1991

Submit your manuscripts athttpwwwhindawicom

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


(a)

500 1000 1500 2000 2500 3000

G-band

D-band

Inte

nsity

(au

)

D998400998400-band

D998400-band

Raman shift (cmminus1)

(b)

Figure 1 (a) SEM image of referenceMWCNTswith 100purity Inset shows theHRTEM image of referenceMWCNTs (b) Raman spectrumof reference MWCNTs

observed fromMWCNTs and amorphous carbons for evalu-ating the purity ofMWCNTs A high purityMWCNT-samplewas prepared and then used as a reference material Thepurity was evaluated from comparing 11986310158401015840-band to 119866-bandintensity ratio (119868

11986310158401015840119868119866) of sample with 119868

11986310158401015840119868119866of reference

materials MWCNTs have been synthesized by either arc-discharge [18 19] or chemical vapor deposition (CVD) [1ndash10] Since the MWCNTs synthesized by arc-discharge havehigher crystallinity 11986310158401015840-band is scarcely seen in the Ramanspectrum Therefore the method to be introduced in thisreport is useful for only CVD-grown MWCNTs But theMWCNTs synthesized by arc-discharge are not used in thepractical applications due to the impossibility of mass pro-ductionTherefore it is still worthy of developing themethodhave evaluating the purity of CVD-grownMWCNTs that areunexceptionally shown11986310158401015840-band in the Raman spectrumWewill provide the detailed protocols for determining the purityof CVD-grown MWCNTs which are confirmed by testingthe mixture of high purity MWCNTs and amorphous carbonparticles

2 Experimental

In order to synthesize MWCNTs FeMoAl2O3particles

were prepared using combustion method FeMo particleswere used as catalysts and Al

2O3was supporting the cata-

lysts Metal-organic precursors of iron nitrate molybdenumacetate and aluminum nitrate were dissolved in deionizedwater and then the prepared solution was transformed intocatalyst powder by thermal treatment at 450∘C for 30minin air ambient The quartz boat having the catalyst powderwas placed inside a quartz tube reactor After heating thereactor to 700∘C in Ar atmosphere a gas mixture of C

2H4H2

(1 1) was fed into the reactor with a pressure of 1 atm for thesynthesis followed by cooling to room temperature under Aratmosphere

The morphologies of MWCNTs were investigated usingscanning electron microscopy (SEM JEOL JSM 6700F) and

transmission electron microscopy (TEM FEI Tecnai 20200 kV) The amount of catalyst particles included in thesynthesized MWCNT samples was investigated by TGAAmorphous carbon powder was purchased from Aldrichto be used as an impurity material In order to verify theproposed evaluation method several intermediate puritysamples having the purity range of 0ndash100 with 20interval were prepared by mixing high purity MWCNTsand amorphous carbon powder considered as 100 and 0respectively Then Raman spectroscopy measurement wascarried out to evaluate the purity ofMWCNTs using a Ramanmicroscope (TRIVIA Acton)

3 Results and Discussion

Through optimizing the experimental parameters for thesynthesis of MWCNTs we prepared very high purity MWC-NTs as can be seen in Figure 1(a) Despite of a number ofobservations using SEM we could not see carbonaceous par-ticles TEM image (inset figure) clearly shows the synthesizedmaterials are all of MWCNTs with hollow insides Accordingto TGA analysis two weight-percent (wt) of catalyst metalparticles is included in the prepared MWCNTs However wecould hardly see the catalyst particles during both SEM andTEM observations It is believed that 2 wt of catalyst parti-cles corresponds to an extremely small volume percent thatcould be negligible because the bulk density of catalyst parti-cle is much larger than that of MWCNTs Furthermore mostof the catalyst particles are residing insideMWCNTs after thesynthesis [20] which does not affect Raman spectrumThere-fore this high purity MWCNTs could be considered as a ref-erence material with 100 purity Figure 1(b) represents theRaman spectrum of a reference MWCNT sample The spec-trum was taken using an excitation wavelength of 633 nmThe Raman spectrum shows a typical feature of MWC-NTs the first ordered 119863- 119866- and 1198631015840-band peaks locatedat around 1350 1582 and 1610 cmminus1 respectively 119866-bandpeak is assigned to ldquoin planerdquo displacement of the carbons


2120583m

(a)

2120583m

(b)

2120583m

(c)

2120583m

(d)

2120583m

(e)

2120583m

(f)











11986310158401015840119868119866instead

of 119868119863119868119866








) times 100 (1)



1008060

40200

Inte

nsity

(au

)


(a)


Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100

(b)







119863119868119866)



11986310158401015840119868119866


11986310158401015840119868119866measured


11986310158401015840119868119866is valid




Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100


4 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




2120583m

(a)

2120583m

(b)

2120583m

(c)

2120583m

(d)

2120583m

(e)

2120583m

(f)











11986310158401015840119868119866instead

of 119868119863119868119866








) times 100 (1)



1008060

40200

Inte

nsity

(au

)


(a)


Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100

(b)







119863119868119866)



11986310158401015840119868119866


11986310158401015840119868119866measured


11986310158401015840119868119866is valid




Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100


4 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




1008060

40200

Inte

nsity

(au

)


(a)


Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100

(b)







119863119868119866)



11986310158401015840119868119866


11986310158401015840119868119866measured


11986310158401015840119868119866is valid




Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100


4 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Mea

sure

d pu

rity

()

100

80

60

40

20

0

0 20 40 60 80 100


4 Conclusion




Acknowledgment


References
































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article novel method of evaluating the purity of...

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