Research Article Common Wet Chemical Agents for Purifying ...

Research ArticleCommon Wet Chemical Agents for Purifying MultiwalledCarbon Nanotubes

Rasel Das1 Md Eaqub Ali1 Sharifah Bee Abd Hamid1

M S M Annuar2 and Seeram Ramakrishna3

1Nanotechnology and Catalysis Research Center University of Malaya 50603 Kuala Lumpur Malaysia2Institute of Biological Sciences Faculty of Science University of Malaya 50603 Kuala Lumpur Malaysia3NUS Centre for Nanofibers and Nanotechnology (NUSCNN) Healthcare and Energy Materials LaboratoryNational University of Singapore Singapore 117584

Correspondence should be addressed to Md Eaqub Ali eaqubaligmailcom

Received 31 August 2014 Revised 2 December 2014 Accepted 2 December 2014 Published 22 December 2014

Academic Editor Chunyi Zhi

Copyright copy 2014 Rasel Das et alThis is an open access article distributed under theCreativeCommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Purification and functionalization of multiwalled carbon nanotubes (MWCNTs) are challenging but vital for their effectiveapplications in various fields including water purification technologies optoelectronics biosensors fuel cells and electrode arraysThe currently available purification techniques often complicated and time consuming yielded shortened and curled MWCNTsthat are not suitable for applications in certain fields such as membrane technologies hybrid catalysis optoelectronics and sensordevelopments Here we described the H

2O2synergy on the actions of HCl and KOH in purifying and functionalizing pristine

MWCNTs The method (HClH2O2) showed 100 purification yield as compared to HCl and KOHH

2O2with purification

yields 9346 and 392 respectively We probed the findings using transmission electron microscope energy dispersive X-rayspectroscope attenuated total reflectance infrared spectroscope Raman spectroscope thermal gravimetric analysis and X-raypowder diffraction The study is a new avenue for simple rapid low cost and scalable purification of pristine MWCNTs forapplication in versatile fields

1 Introduction

Carbon nanotubes (CNTs) are one of the most fascinatingnanomaterials having many attractive and useful physico-chemical properties such as mechanical [1 2] thermal [3]electrical [2 4] and optoelectronic properties [5] SinceCNTswere defined by Iijima in 1991 [6] they have played significantshoot in many domains including water purification tech-nologies [7ndash9] polymer and composites [10ndash12] conductivecable fibers [13] hydrogen storage media [14] biomedicalsciences [15] field emission displays [16] electrochemistryand nanosensors [17] nanoelectrodes and microarrays [18]and many other versatile fields [16]

CNTs are often received or synthesizedwith other genericimpurities such as nonnanotube or amorphous carbons ashand metal catalysts with extreme hydrophobicity [19] Theexisting CNT synthesis methods added the impurities suchas metal catalysts to increase the yield and reduce cost [20]

The level of these unwanted matters depends on the specificmethod used for CNT synthesis Whatever might be themethod of choice impurities often hinder CNTs perform-ances and confuse the understanding of their original func-tionalities limiting their applications in many importantfields For instance this triggered CNT aggregation in vari-ous polymers [21] which destabilizes polymerrsquos mechanicalstrength and electrical conductivity [21]

In order to purify pristine CNTs three classes of CNTpurification methods such as chemical physical and a com-bination of both were developed [19] Chemical purificationmethod was effective because of its selectivity sensitiv-ity faster rate kinetics of the oxidation of carbonaceousimpurities and metal catalysts dissolution from the pristineCNTs [22] In addition chemical agents are widely availableand cost-effective and need simple laboratory settings Incontrast physicalmethodwas involved in removing graphiticsheets and carbon nanospheres from CNT [19] The method

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 945172 9 pageshttpdxdoiorg1011552014945172

2 Journal of Nanomaterials

was not effective to remove carbon impurities often compli-cated and time consuming [19] Therefore based on pristineCNT impurities one can select chemical physical or a com-bination of both in order to get pure CNT with desiredproperties

HCl H2O2 and KOH are easily available simple wet

chemicals that are commonly found in most of the ordinarylaboratories Here we treated MWCNTs with HCl [23 24]as a reference But HCl is often incapable of completingremoval of nonnanotube impurities [25] Pristine few walledcarbon nanotubes (FWCNTs) were oxidized and purified byH2O2[26] but the method thus far is not extensively studied

for multiwalled carbon nanotubes (MWCNTs) purificationexcept few [22 27] Although single-walled carbonnanotubes(SWCNTs) were purified by a mixture of HCl and H

2O2

[25 28ndash31] no study has yet been adopted for MWCNTpurification by using that mixtureTherefore we studied herethe synergistic effects of HClH

2O2mixture for improving

the carbon yield and getting purified well graphitic layerof MWCNTs A basic treatment involving NH

4OHH

2O2

was effective in purifying MWCNTs [32] We developed andapplied another basic wet oxidizing technique involving amixture of KOHH

2O2in purifying MWCNTsThe methods

(HCl HClH2O2 and KOHH

2O2) were effective to get

oxidized MWCNTs but high purification yield was observedfor HClH

2O2compared with HCl and KOHH

2O2 We

focused on MWCNTs because of their low preparation costsand availability in large quantities

Transmission electron microscope (TEM) was used tostudy the morphological changes of MWCNTs Energy dis-persive X-ray spectroscope (EDX) was used for the analysisof elemental composition and state of impurities Attenuatedtotal reflectance infrared (ATR-IR) spectroscope was per-formed to estimate the degree and type of functionalizationRaman spectroscope was conducted to measure the defectsand character of graphite bands and thermal gravimetricanalysis (TGA) was used to record themass profile of pristineand treated MWCNTs Finally X-ray powder diffraction(XRD) was used to define crystallinity in-plane regularityand lattice profiles

2 Experimental Section

21 Materials PristineMWCNTs of 12plusmn5 and 4 nm in outerand inner diameters and gt1 120583m in length were bought fromBayer MaterialScience AG (Germany) The tubes were pre-pared by catalytic chemical vapor deposition (CCVD) andcontained gt95 carbon by weight and were used as receivedHydrochloric acid and hydrogen peroxide were purchasedfrom Merck Sdn Bhd (Malaysia) Potassium hydroxide eth-anol and acetone were purchased from Sigma-Aldrich SdnBhd (Malaysia) The purity of all reagents was ge99 excepthydrochloric acid (37) hydrogen peroxide (30) and eth-anol (70) in water

22 Instrumentation TEM (Hitachi-HT7700 Japan) wasused for the morphological characterizations of the MWC-NTs It was performed at 120 kV An EDX coupled witha FE-SEM (QUANTA FEG 450 FEI USA) was used for

elemental analysis An X-Max Silicon Drift detector (OxfordUK) of 80mm2 was used to identify the elements and energyand relative intensity of emitted X-rays were analyzed at10 Kev ATR-IR spectra were recorded on a KBr using an IRspectrometer (IFS 66 vS Bruker Germany) Raman spectrawere acquired for 10min at a laser power of 100 on Ar+ laser(514 nm) focused (50X objective) on a spot size of about 15ndash20 120583m (Renishaw inVia UK) TGA (TGASDTA 851 MettlerToledo USA) was performed under air flow (50mL) between25 and 1000∘C at 10∘Cmin XRD diffracted patterns werecollected at Ni filtered Cu K120572 radiation (40 kV 40mA 120582 =15401 A) (XRDD8 Bruker Germany)

23 Wet Chemical Treatments of MWCNTs Three wet chem-ical treatments were performed to purify and oxidize the as-obtained pristine MWCNTs

(i) HCl Treatment Pristine MWCNTs (05 g) were treatedwith 100mL of hydrochloric acid (36wt) and sonicatedat 50∘C for 3 h in an ultrasonication bath (Series 400POWERSONIC 40KHz Korea) [24] The method was as areference

(ii) HClH2O2 Treatment Pristine MWCNTs (05 g) weredispersed into 25mL mixture (70 30) of hydrochloric acid(36wt) and hydrogen peroxide (30wt) and the finalmixture was sonicated at 50∘C for 5 h at 40KHz

(iii) KOHH2O2 Treatment Pristine MWCNTs (05 g) weredispersed into a 20mLmixture (50 50) of potassiumhydrox-ide (25wt) and hydrogen peroxide (30wt) and themixture was sonicated at 50∘C for 5 h at 40KHz

24 Removal of the Residual Impurities All treatedMWCNTswere extracted from the residual acids bases metallic by-products and carbonaceous impurities by repeated cycleof dilution and centrifugation (dissolved in 1 L of deion-ized water and centrifuged (Eppendorf-5430R Germany) at7000 rpm for 30min) The supernatant was carefully col-lected when the MWCNTs were precipitated at the bottom ofthe polyethylene centrifuge tubeThe procedure was repeated5-6 times until the resistivity of the supernatant was greaterthan 05MΩsdotcmandpHwassim70The treatedMWCNTswerethen rinsed with ethanol (70wt) and dried overnight in avacuum oven at 100∘C

3 Results and Discussion

31 Predicted Chemical Reactions of HCl H2O2 and KOH

with MWCNTs To get pure MWCNTs agents such as HClHClH

2O2 and KOHH

2O2were found to be promising

(Figure 1) The method (HClH2O2) can purify MWCNTs

through different routes The metals that are usually presentin pristine CNTs act as catalysts to produce hydroxyl radical(OHo) through Fentonrsquos chemistry [33] (Figure 1(a)) whichis stronger oxidizing agent than H

2O2

H2O2+metal (reduced) 997888rarr OHo

+OHminus +metal (oxidized)(1)

Journal of Nanomaterials 3

OH

OH

OH

OH

OH

OH

OH

OH

OHOHOH

Metal

OH

OHOO

O

OO

R

R

O

O

O

O

O

O

Highly pure

CNT skeleton

CNT skeleton

CNT

skele

ton

CNT

Less pureCNT

HereR alkyl or aryl and so forth

HClH2

O 2

KOHH2 O

2

H2O2HO∙ + OHminus

Amorphous

Amorphous

carbon oxidation

oxidationMetal

carbon layer

CO2

HClmediatedremoval

Metalimpurities

Pentagonal

Heptagonal

carbon

carbon

X2H2O2

2K2O2

2H2O

2H2O

O2HO∙ + OHminus

2KOH

4KOH

2KHO2

b

c

fd

e

a

(sonica

tion te

mp 50∘ C 5

h)

(sonication temp 50 ∘C 5h)

Figure 1 Schematic of the localized catalytic reactions of HClH2O2(a) (b) and (c) and KOHH

2O2(d) (e) and (f) with pristineMWCNTs

The radical (OHo) is then reacted with amorphous carbonimpurities of pristine CNTs [22] and converted them intoCO2[25] (Figure 1(b))

4OHo+ C 997888rarr CO

2+ 2H2O (2)

The oxidized metals and other impurities are then dissolvedinto HCl (Figure 1(c)) which are subsequently removedthrough filtering and washings

However a mixture of KOH and H2O2was unable to

complete amorphous carbon oxidation and removal of metalimpurities from MWCNT This is because of the chemicalreactions between KOH and H

2O2(Figures 1(d) 1(e) and

1(f)) KOH decreases the availability of H2O2in the system

so there is the least chance to produce free radicals and otheretching agents The ultimate products of the reaction wereKOH and O

2 Oxygen was evaporated while KOH may have

some chemical interactions with amorphous carbons whichmight be negligible to remove MWCNT core impurities

32 TEM Analysis TEM microscope was used to closelyexamine the contents of amorphous carbon and location ofmetal catalysts trapped into the tubular interstitial spaces ofpristine and treatedMWCNTs (Figure 2) Pristine MWCNTsreflected clumped cloudy and amorphous carbon containingMWCNTs (Figure 2(a)) The impure carbonaceous particleswere found to be wrapped around the nanotube struc-tures and metal catalysts were trapped into the MWCNTsAlthough the overall amorphous carbons and metals wereremoved from the nanotube surface after HCl treatment

some MWCNTs were thick suggesting small percentagesof nonnanotube carbonaceous agents and impurities maypresent on MWCNT surfaces (Figure 2(b)) The HClH

2O2

treatment producedmuch cleaner fresh and complete amor-phous carbon and metals-free MWCNTs and the nanotubesappeared in thin and loosely connected bundles (Figure 2(c))Although the oxidizing strength of H

2O2is high (Pka 116)

it did not produce vigorous CNT fragmentations upon thepurification process in presence of HCl In the KOHH

2O2

treatment some of the amorphous carbons from MWCNTsurfaces were removed However the effects were local sincethe presence of some nonnanotube carbon impurities wasglobally obvious (Figure 2(d)) and the nanotubes appearedmore flattened and thick than those of HCl (Figure 2(b)) andHClH

2O2(Figure 2(c)) treated MWCNTs

33 EDX Analysis EDX is a significant characterization toolfor measuring the extent of CNT oxidation and elementalcomposition [22] EDX findings of the pristine and treatedMWCNTs are shown in Figure 3 and representative analysisis listed in Table 1 Purification yield of pristine and treatedMWCNTs was calculated based on the following

Purification yield () 1198820minus119882119905

1198820

times 100 (3)

where1198820is the metal content of the pristine MWCNT ()

and119882119905is the metal content of purified MWCNT ()

As we observed in Table 1 by far the largest element inthe as-received pristine MWCNT is carbon (either graphitic


(a)

(c)

(b)

(d)

Figure 2 TEM images of pristine (a) HCl (b) HClH2O2(c) and KOHH

2O2treated MWCNTs (d)

Table 1 Elemental analysis of before and after MWCNT treatments in this study

Specimen Treatment time (h) Elemental composition (Wt)C O Co Mn Al Mg Sum Purification yield ()

Pristine MWCNT 0 9735 112 048 046 03 029 100 mdashMWCNT-HCl 5 9877 113 0 0 01 0 100 9346MWCNT-HClH2O2 5 9878 122 0 0 0 0 100 100MWCNT-KOHH2O2 5 9519 334 045 042 03 03 100 392

or amorphous) with some extent of oxygen (Figure 3(a))However pristine MWCNTs were highly contaminated withmetal impurities such as Co Mn Al and Mg (Figure 3(a))After wet chemical agent treatments it was observed thatthe amount of graphitic carbons was slightly increased sincemost of the metal impurities diminish significantly given theestablished role of HCl and HClH

2O2as good purification

yields of 9346 and 100 respectively (Figures 3(b) and3(c)) In contrast KOHH

2O2was incapable of completing

removal of metal impurities and showed lowest purificationyield 392 (Figure 3(d)) Herein we hypothesized that theHClH

2O2mixture can be a judicial choice for the complete

purification of pristine MWCNTs compared with HCl andKOHH

2O2treatments

34 ATR-IR Analysis ATR-IR spectroscope was performedfor characterizing the functionalities produced followingwet chemical treatments (HCl HClH

2O2 and KOHH

2O2)

resulting in MWCNT purifications The IR spectra of thepristine and treated MWCNTs are depicted in Figure 4 Thedominant IR spectrum at 3409 cmminus1 was assigned to thestretching vibration of intermolecularly hydrogen bondedOH OH groups (Figures 4(a) 4(b) 4(c) and 4(d)) [34 35]The intensity of this band was low in pristine MWCNTs

(Figure 4(a)) but it was significantly increased and broad-ened following wet chemical treatments and purificationsespecially at KOHH

2O2(Figure 4(d)) indicating the forma-

tion of huge ndashOH groups upon chemical treatments [36]The IR transmittance peak at 2907 cmminus1 which was dominantin HClH

2O2(Figure 4(c)) and KOHH

2O2(Figure 4(d))

treated MWCNTs was assigned to sp2 and sp3 CndashH stretch-ing vibrations [37] The transmittance bands at 2422 and2279 cmminus1 were observed for pristine (Figure 4(a)) HClH2O2(Figure 4(c)) and KOHH

2O2(Figure 4(d)) but was

absent in the HCl (Figure 4(b)) treated MWCNTs respec-tively may pointing out the grafting of some CO and COOminusgroups respectively [38] The peak at 1630 cmminus1 (Figures4(a) 4(b) 4(c) and 4(d)) was due to the stretching vibrationof C=C [36] and C=O of quinone [38] that was createdon MWCNT surfaces following wet chemical treatmentsThe highest intensity of this peak was found followingKOHH

2O2treatment (Figure 4(d)) suggesting the presence

of more ndashCO groups The prominent peak at 1044 cmminus1(Figures 4(a) 4(b) 4(c) and 4(d)) was due to ndashOH groupgenerated because of the atmospheric oxidation or oxidationfrom wet chemical treatments [38] In addition a peakthat appeared at 804 cmminus1 was due to epoxy and oxiranerings evolved from CndashOndash groups and ring deformation of


Electron image 1

10120583m

cps (

eV)

C

MgO

Co

Co

AlN MnMn

0

0

5 10

10

20

15

(keV)

Spectrum 1Wt 120590

CONCoMnAlMg

9735 0202000001010000

112

048

03046

029

(a)

10120583m

C

OAlN

cps (

eV)

0

0

5 10

20

15

Spectrum 2

Wt 120590COAl

9877 02020001

113

Electron image 2

(keV)

(b)

10120583m

C

ON

cps (

eV)

0

0

5 10

20

40

15

Spectrum 3Wt 120590

CON

9878 02020000

122

Electron image 3

(keV)

(c)

10120583m

C

O

cps (

eV)

0

0

5 10

10

5

15

Mg

MnCo

AlN CoMn

Spectrum 4Wt 120590

CONCo

9519 0403000001

334

045MnAlMg

010000

03042

03

Electron image 4

(keV)

(d)

Figure 3 EDX profiles of pristine (a) HCl (b) HClH2O2(c) and KOHH

2O2(d) treated MWCNTs

substituted aromatic structures [36] Some weak peaks thatappeared in 2500ndash3500 cmminus1 region in pristine MWCNTs(shown by asterisks) (Figure 4(a)) disappeared followingchemical treatments (Figures 4(b) 4(c) and 4(d)) It clarifiesthe presence of some minor functional groups of the pris-tine MWCNTs anchored by amorphous carbons and othercarbonaceous fragments which were successfully removed bywet chemicals processing

35 Raman Spectroscopy Typically MWCNT represents twosignificant high frequency bands called D- and G-bands at

1330 and 1585 cmminus1 for CNT structural defects and graphitein-plane vibration respectively [39 40] In this study D- andG-bands appeared at sim1349 and sim1588 cmminus1 both in treatedand pristine MWCNTs respectively (Figure 5)

The intensity of the D-band which is induced by nonzerocenter phonon mode usually depends on the presence ofdisordered carbon atomic networks [31 41] However Figure5 shows the D-band intensities were practically constantin both pristine and treated MWCNTs This indicates thatMWCNTs were purified with less defects density This mightbe due to the milder reaction conditions among graphitic


400 500 1000 1500 2000 2500 40003000 3500

Wavenumber (cmminus1)

Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast

lowastlowastlowastlowast

(cmminus1)

Figure 4 ATR-IR spectra of pristine (a) HCl (b) HClH2O2(c)

and KOHH2O2(d) treated MWCNTs

10

08

06

04

02

00

Inte

nsity

DG

Raman shift (cmminus1)1200 1400 1600

IGIDPristineMWCNT-HCLMWCNT-HCLH2O2

MWCNT-KOHH2O2

067081091073

Figure 5 Normalized Raman spectra of pristine and treatedMWCNTs

carbons of MWCNTs and HCl HClH2O2and KOHH

2O2

The etching properties of OHo which was generated byFentonrsquos chemistry [33] may have direct affinity to oxidizeamorphous carbons due to the presence of many activesites on it [32] (Figure 1(b)) rather than oxidizing graphiticlayerrsquos carbon atoms On the other hand KOHH

2O2was

unable to directly react with graphitic skeleton since mostof the amorphous carbons were wrapped around the pristineMWCNTs (Figures 1(d) 1(e) and 1(f)) However the G-bandintensities were significantly increased in treated MWCNTsespecially for HClH

2O2treated MWCNTs This clearly

indicates that the HClH2O2removed nonnanotube carbon

10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)

Pristine MWCNTMWCNT-HCl

MWCNT-HClH2O2

MWCNT-KOHH2O2

Figure 6 TGA curves of pristine and treatedMWCNTs (down) andtheir derivative spectra (up)

impurities and metal catalysts and generated well graphiticMWCNT structure [41] compared to HCl and KOHH

2O2

while maintaining intact MWCNT integrity (Figure 5)Finally the purity states of the pristine and treated

MWCNTs were compared from the intensity ratio of theG (119868G) and D-bands (119868D) [32] The highest ratio (091) of119868G119868D was found forHClH

2O2treatedMWCNTs suggesting

the better efficiency of HClH2O2in removing amorphous

and carbonaceous materials from MWCNTs [26] The 119868G119868Dratios forHCl (081) andKOHH

2O2(073) treatedMWCNTs

were less effective in complete removal of nonnanotubecarbon impurities andmetal catalysts frompristineMWCNTsurfaces (Figure 5)

36 TGAAnalysis TGAwas performed tomeasure the amor-phous carbons oxidation defects and overall quality of puri-fied MWCNTs TGA of pristine and treated MWCNTs(down) with their derivative spectra (up) are presented inFigure 6 By oxidation temperature herein we mean thetemperature where MWCNTs lose their weight and thusshow the highest derivative weight curve This can definethe stability of MWCNTs at a given temperature At firstpristine and KOHH

2O2treated MWCNTs showed lowest

decomposition temperatures at around 100∘C and lost theirweights of about 1 and 70 respectively which correspondto the pyrolytic evolution of hydroxyl andor water [32]Typically amorphous carbons oxidized at around 500∘C [42]due to their lower activation energy and the presence ofmany heat sensitive active sites [32] TGA of pristine andKOHH

2O2treated MWCNTs showed highest decomposi-

tion temperatures at 550∘C and loss of their weights of about5 and 75 respectively (Figure 6) However pure and wellgraphitic carbon skeletons are commonly reacted at relatively


2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)

Figure 7 XRD patterns of pristine (a) HCl (b) HClH2O2(c) and KOHH


higher temperature ranges between 600 and 700∘C [43]TGA of HCl and HClH

2O2(Figure 6) treated MWCNTs

started to weight loss of about 5 and 10 respectively at600∘C suggesting the efficacy of these chemicals in purifyingMWCNTs Remaining disordered carbons present in allMWCNTs showed complete weight loss between 650 and800∘C [32]

37 XRD Analysis The two characteristic XRD peaks ofMWCNTs for two important phases such as 002 and 100 inthe range of 2120579 = (10ndash60∘) (Figure 7) were followed in thisstudy [44] The peak characterizing the interlayer spacing(002) of CNT tubular walls was observed at 2120579 = 2608and 2603∘ (mean) for pristine (Figure 7(a)) and treatedMWCNTs (Figures 7(b) 7(c) and 7(d)) respectively Thisindicates that the graphitic structure of MWCNTs was notdestroyed during the purification process [45] The peakdefining in-plane regularity (100) appeared at 2120579 = 4334

and 4326∘ (mean) for pristine (Figure 7(a)) and treatedMWCNTs (Figures 7(b) 7(c) and 7(d)) respectively Whenall parts of MWCNTs are absolutely parallel to the 002 planethe intensity of the peak 100 often decreases or vanishes [27]Presence of nonnanotube impurities and debris can changecarbon ordering and increase roughness of the CNT surfacelattice structure The intensity at plane 100 was 801 lt 1044lt 1225 lt 1937 for HClH

2O2(Figure 7(c)) HCl (Figure

7(b)) KOHH2O2(Figure 7(d)) and pristine MWCNTs

(Figure 7(a)) respectivelyThis suggested that the HClH2O2

treated MWCNT had well parallel MWCNT lattice structurebecause of complete elimination of nonnanotube impuritiesas compared to HCl and KOHH

2O2

4 Conclusions

Thepurification ofMWCNTsusing three commonwet chem-ical agents (HCl HClH

2O2 and KOHH

2O2) is presented


The HClH2O2mixture produced more cleanly and well

orderly MWCNT skeleton compared with that of ordinaryHCl Although considerable removal of amorphous carbonis possible with KOHH

2O2treatment complete MWCNT

purification is out of place Thus the MWCNT puritiesdepend on the nature of wet chemical agents and impuritiespresent in the overall MWCNT structure

Conflict of Interests

The authors declare no conflict of interests

Acknowledgments

Rasel Das is a recipient of the University of Malaya BrightSpark Scholarship The research is supported by HIR Projectno H-21001-F000032 NND Project no 53-02031090 andUMRG (RP022-2012A) given to Professor Sharifah Bee AbdHamid

References

[1] E W Wong P E Sheehan and C M Lieber ldquoNanobeammechanics elasticity strength and toughness of nanorods andnanotubesrdquo Science vol 277 no 5334 pp 1971ndash1975 1997

[2] Z Y Liu B L XiaoW GWang and Z YMa ldquoTensile strengthand electrical conductivity of carbon nanotube reinforcedaluminum matrix composites fabricated by powder metallurgycombined with friction stir processingrdquo Journal of MaterialsScience amp Technology vol 30 no 7 pp 649ndash655 2014

[3] J Hone B Batlogg Z Benes A T Johnson and J E FischerldquoQuantized phonon spectrumof single-wall carbon nanotubesrdquoScience vol 289 no 5485 pp 1730ndash1733 2000

[4] S J Tans A R M Verschueren and C Dekker ldquoRoom-temperature transistor based on a single carbon nanotuberdquoNature vol 393 no 6680 pp 49ndash52 1998

[5] PAvouris and J Chen ldquoNanotube electronics and optoelectron-icsrdquoMaterials Today vol 9 no 10 pp 46ndash54 2006

[6] S Iijima ldquoHelicalmicrotubules of graphitic carbonrdquoNature vol354 no 6348 pp 56ndash58 1991

[7] R Das S B A Hamid M E Ali A F Ismail M Annuar andS Ramakrishna ldquoMultifunctional carbon nanotubes in watertreatment the present past and futurerdquo Desalination vol 354pp 160ndash179 2014

[8] R Das M E Ali S B A Hamid S Ramakrishna andZ Z Chowdhury ldquoCarbon nanotube membranes for waterpurification a bright future in water desalinationrdquoDesalinationvol 336 no 1 pp 97ndash109 2014

[9] M E Ali R Das A Maamor and S B A Hamid ldquoMul-tifunctional carbon nanotubes (CNTs) a new dimension inenvironmental remediationrdquo Advanced Materials Research vol832 pp 328ndash332 2014

[10] Z Spitalsky D Tasis K Papagelis and C Galiotis ldquoCarbonnanotube-polymer composites chemistry processingmechan-ical and electrical propertiesrdquo Progress in Polymer Science(Oxford) vol 35 no 3 pp 357ndash401 2010

[11] E T Thostenson C Li and T-W Chou ldquoNanocomposites incontextrdquoComposites Science and Technology vol 65 no 3-4 pp491ndash516 2005

[12] S Parveen S Rana and R Fangueiro ldquoA review on nano-material dispersion microstructure andmechanical propertiesof carbon nanotube and nanofiber reinforced cementitiouscompositesrdquo Journal of Nanomaterials vol 2013 Article ID710175 19 pages 2013

[13] M Miyauchi J Miao T J Simmons et al ldquoConductive cablefibers with insulating surface prepared by coaxial electro-spinning of multiwalled nanotubes and celluloserdquo Biomacro-molecules vol 11 no 9 pp 2440ndash2445 2010

[14] U Sahaym and M G Norton ldquoAdvances in the application ofnanotechnology in enabling a ldquohydrogen economyrdquordquo Journal ofMaterials Science vol 43 no 16 pp 5395ndash5429 2008

[15] Y Zhang Y Bai and B Yan ldquoFunctionalized carbon nanotubesfor potentialmedicinal applicationsrdquoDrugDiscovery Today vol15 no 11-12 pp 428ndash435 2010

[16] R H Baughman A A Zakhidov and W A De Heer ldquoCarbonnanotubesmdashthe route toward applicationsrdquo Science vol 297 no5582 pp 787ndash792 2002

[17] J Kong N R Franklin C Zhou et al ldquoNanotube molecularwires as chemical sensorsrdquo Science vol 287 no 5453 pp 622ndash625 2000

[18] J E Koehne H Chen A M Cassell et al ldquoMiniaturizedmultiplex label-free electronic chip for rapid nucleic acid anal-ysis based on carbon nanotube nanoelectrode arraysrdquo ClinicalChemistry vol 50 no 10 pp 1886ndash1893 2004

[19] P-X Hou C Liu and H-M Cheng ldquoPurification of carbonnanotubesrdquo Carbon vol 46 no 15 pp 2003ndash2025 2008

[20] Y Kobayashi H Nakashima D Takagi and Y Homma ldquoCVDgrowth of single-walled carbon nanotubes using size-controllednanoparticle catalystrdquo Thin Solid Films vol 464-465 pp 286ndash289 2004

[21] L Vaisman G Marom and H D Wagner ldquoDispersions ofsurface-modified carbon nanotubes in water-soluble andwater-insoluble polymersrdquoAdvanced Functional Materials vol 16 no3 pp 357ndash363 2006

[22] K A Wepasnick B A Smith K E Schrote H K Wilson SR Diegelmann and D H Fairbrother ldquoSurface and structuralcharacterization of multi-walled carbon nanotubes followingdifferent oxidative treatmentsrdquo Carbon vol 49 no 1 pp 24ndash362011

[23] A R Harutyunyan B K Pradhan J Chang G Chen and PC Eklund ldquoPurification of single-wall carbon nanotubes byselective microwave heating of catalyst particlesrdquo Journal ofPhysical Chemistry B vol 106 no 34 pp 8671ndash8675 2002

[24] B Scheibe E Borowiak-Palen and R J Kalenczuk ldquoOxidationand reduction of multiwalled carbon nanotubesmdashpreparationand characterizationrdquoMaterials Characterization vol 61 no 2pp 185ndash191 2010

[25] Y Wang H Shan R H Hauge M Pasquali and R E SmalleyldquoA highly selective one-pot purification method for single-walled carbon nanotubesrdquoThe Journal of Physical Chemistry Bvol 111 no 6 pp 1249ndash1252 2007

[26] Y Feng H Zhang Y Hou et al ldquoRoom temperature purifi-cation of few-walled carbon nanotubes with high yieldrdquo ACSNano vol 2 no 8 pp 1634ndash1638 2008

[27] Y Peng and H Liu ldquoEffects of oxidation by hydrogen peroxideon the structures of multiwalled carbon nanotubesrdquo Industrialand Engineering Chemistry Research vol 45 no 19 pp 6483ndash6488 2006


[28] X Zhao M Ohkohchi S Inoue T Suzuki T Kadoya andY Ando ldquoLarge-scale purification of single-wall carbon nan-otubes prepared by electric arc dischargerdquoDiamond andRelatedMaterials vol 15 no 4ndash8 pp 1098ndash1102 2006

[29] T Suzuki K Suhama X Zhao S Inoue N Nishikawa and YAndo ldquoPurification of single-wall carbon nanotubes producedby arc plasma jet methodrdquoDiamond and Related Materials vol16 no 4 pp 1116ndash1120 2007

[30] N Karatepe and N Yuca ldquoHydrogen adsorption on carbonnanotubes purified by different methodsrdquo International Journalof Hydrogen Energy vol 36 no 17 pp 11467ndash11473 2011

[31] U J Kim C A Furtado X Liu G Chen and P C EklundldquoRaman and IR spectroscopy of chemically processed single-walled carbon nanotubesrdquo Journal of the American ChemicalSociety vol 127 no 44 pp 15437ndash15445 2005

[32] V Datsyuk M Kalyva K Papagelis et al ldquoChemical oxidationof multiwalled carbon nanotubesrdquo Carbon vol 46 no 6 pp833ndash840 2008

[33] C Walling ldquoFentonrsquos reagent revisitedrdquo Accounts of ChemicalResearch vol 8 no 4 pp 125ndash131 1975

[34] N M Vesali A A Khodadadi Y Mortazavi A O SahraeiF Pourfayaz and M S Sedghi ldquoFunctionalization of carbonnanotubes using nitric acid oxidation and DBD plasmardquoWorldAcademy of Science Engineering andTechnology vol 37 pp 177ndash179 2009

[35] R A Nyquist Interpreting Infrared Raman and Nuclear Mag-netic Resonance Spectra Academic Press 2001

[36] J Coates ldquoInterpretation of infrared spectra a practicalapproachrdquo in Encyclopedia of Analytical Chemistry 2000

[37] Y-R Shin I-Y Jeon and J-B Baek ldquoStability of multi-walledcarbon nanotubes in commonly used acidic mediardquo Carbonvol 50 no 4 pp 1465ndash1476 2012

[38] P-C Ma and J-K Kim Carbon nanotubes for Polymer Rein-forcement CRC Press 2011

[39] P C Eklund and K R Subbaswamy ldquoAnalysis of Breit-Wignerline shapes in the Raman spectra of graphite intercalationcompoundsrdquo Physical Review B vol 20 no 12 pp 5157ndash51611979

[40] A C Dillon T Gennett K M Jones J L Alleman P A Parillaand M J Heben ldquoA simple and complete purification of single-walled carbon nanotube materialsrdquo Advanced Materials vol 11no 16 pp 1354ndash1358 1999

[41] A Eckmann A Felten A Mishchenko et al ldquoProbing thenature of defects in graphene by Raman spectroscopyrdquo NanoLetters vol 12 no 8 pp 3925ndash3930 2012

[42] P Hou C Liu Y Tong S Xu M Liu and H ChengldquoPurification of single-walled carbon nanotubes synthesizedby the hydrogen arc-discharge methodrdquo Journal of MaterialsResearch vol 16 no 9 pp 2526ndash2529 2001

[43] A G Rinzler J Liu H Dai et al ldquoLarge-scale purification ofsingle-wall carbon nanotubes process product and character-izationrdquo Applied Physics A Materials Science amp Processing vol67 no 1 pp 29ndash37 1998

[44] R Das S B A Hamid M E Ali S Ramakrishna and WYongzhi ldquoCarbon nanotubes characterization by X-ray powderdiffractionmdasha reviewrdquo Current Nanoscience vol 11 pp 1ndash132015

[45] F Taleshi and A A Hosseini ldquoSynthesis of uniformMgOCNTnanorods by precipitation methodrdquo Journal of Nanostructure inChemistry vol 3 no 1 pp 1ndash5 2012

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



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BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


was not effective to remove carbon impurities often compli-cated and time consuming [19] Therefore based on pristineCNT impurities one can select chemical physical or a com-bination of both in order to get pure CNT with desiredproperties

HCl H2O2 and KOH are easily available simple wet

chemicals that are commonly found in most of the ordinarylaboratories Here we treated MWCNTs with HCl [23 24]as a reference But HCl is often incapable of completingremoval of nonnanotube impurities [25] Pristine few walledcarbon nanotubes (FWCNTs) were oxidized and purified byH2O2[26] but the method thus far is not extensively studied

for multiwalled carbon nanotubes (MWCNTs) purificationexcept few [22 27] Although single-walled carbonnanotubes(SWCNTs) were purified by a mixture of HCl and H

2O2

[25 28ndash31] no study has yet been adopted for MWCNTpurification by using that mixtureTherefore we studied herethe synergistic effects of HClH

2O2mixture for improving

the carbon yield and getting purified well graphitic layerof MWCNTs A basic treatment involving NH

4OHH

2O2

was effective in purifying MWCNTs [32] We developed andapplied another basic wet oxidizing technique involving amixture of KOHH

2O2in purifying MWCNTsThe methods

(HCl HClH2O2 and KOHH

2O2) were effective to get

oxidized MWCNTs but high purification yield was observedfor HClH

2O2compared with HCl and KOHH

2O2 We

focused on MWCNTs because of their low preparation costsand availability in large quantities

Transmission electron microscope (TEM) was used tostudy the morphological changes of MWCNTs Energy dis-persive X-ray spectroscope (EDX) was used for the analysisof elemental composition and state of impurities Attenuatedtotal reflectance infrared (ATR-IR) spectroscope was per-formed to estimate the degree and type of functionalizationRaman spectroscope was conducted to measure the defectsand character of graphite bands and thermal gravimetricanalysis (TGA) was used to record themass profile of pristineand treated MWCNTs Finally X-ray powder diffraction(XRD) was used to define crystallinity in-plane regularityand lattice profiles

2 Experimental Section

21 Materials PristineMWCNTs of 12plusmn5 and 4 nm in outerand inner diameters and gt1 120583m in length were bought fromBayer MaterialScience AG (Germany) The tubes were pre-pared by catalytic chemical vapor deposition (CCVD) andcontained gt95 carbon by weight and were used as receivedHydrochloric acid and hydrogen peroxide were purchasedfrom Merck Sdn Bhd (Malaysia) Potassium hydroxide eth-anol and acetone were purchased from Sigma-Aldrich SdnBhd (Malaysia) The purity of all reagents was ge99 excepthydrochloric acid (37) hydrogen peroxide (30) and eth-anol (70) in water

22 Instrumentation TEM (Hitachi-HT7700 Japan) wasused for the morphological characterizations of the MWC-NTs It was performed at 120 kV An EDX coupled witha FE-SEM (QUANTA FEG 450 FEI USA) was used for

elemental analysis An X-Max Silicon Drift detector (OxfordUK) of 80mm2 was used to identify the elements and energyand relative intensity of emitted X-rays were analyzed at10 Kev ATR-IR spectra were recorded on a KBr using an IRspectrometer (IFS 66 vS Bruker Germany) Raman spectrawere acquired for 10min at a laser power of 100 on Ar+ laser(514 nm) focused (50X objective) on a spot size of about 15ndash20 120583m (Renishaw inVia UK) TGA (TGASDTA 851 MettlerToledo USA) was performed under air flow (50mL) between25 and 1000∘C at 10∘Cmin XRD diffracted patterns werecollected at Ni filtered Cu K120572 radiation (40 kV 40mA 120582 =15401 A) (XRDD8 Bruker Germany)

23 Wet Chemical Treatments of MWCNTs Three wet chem-ical treatments were performed to purify and oxidize the as-obtained pristine MWCNTs

(i) HCl Treatment Pristine MWCNTs (05 g) were treatedwith 100mL of hydrochloric acid (36wt) and sonicatedat 50∘C for 3 h in an ultrasonication bath (Series 400POWERSONIC 40KHz Korea) [24] The method was as areference

(ii) HClH2O2 Treatment Pristine MWCNTs (05 g) weredispersed into 25mL mixture (70 30) of hydrochloric acid(36wt) and hydrogen peroxide (30wt) and the finalmixture was sonicated at 50∘C for 5 h at 40KHz

(iii) KOHH2O2 Treatment Pristine MWCNTs (05 g) weredispersed into a 20mLmixture (50 50) of potassiumhydrox-ide (25wt) and hydrogen peroxide (30wt) and themixture was sonicated at 50∘C for 5 h at 40KHz

24 Removal of the Residual Impurities All treatedMWCNTswere extracted from the residual acids bases metallic by-products and carbonaceous impurities by repeated cycleof dilution and centrifugation (dissolved in 1 L of deion-ized water and centrifuged (Eppendorf-5430R Germany) at7000 rpm for 30min) The supernatant was carefully col-lected when the MWCNTs were precipitated at the bottom ofthe polyethylene centrifuge tubeThe procedure was repeated5-6 times until the resistivity of the supernatant was greaterthan 05MΩsdotcmandpHwassim70The treatedMWCNTswerethen rinsed with ethanol (70wt) and dried overnight in avacuum oven at 100∘C

3 Results and Discussion

31 Predicted Chemical Reactions of HCl H2O2 and KOH

with MWCNTs To get pure MWCNTs agents such as HClHClH

2O2 and KOHH

2O2were found to be promising

(Figure 1) The method (HClH2O2) can purify MWCNTs

through different routes The metals that are usually presentin pristine CNTs act as catalysts to produce hydroxyl radical(OHo) through Fentonrsquos chemistry [33] (Figure 1(a)) whichis stronger oxidizing agent than H

2O2

H2O2+metal (reduced) 997888rarr OHo

+OHminus +metal (oxidized)(1)


OH

OH

OH

OH

OH

OH

OH

OH

OHOHOH

Metal

OH

OHOO

O

OO

R

R

O

O

O

O

O

O

Highly pure

CNT skeleton

CNT skeleton

CNT

skele

ton

CNT

Less pureCNT


HClH2

O 2

KOHH2 O

2

H2O2HO∙ + OHminus

Amorphous

Amorphous

carbon oxidation

oxidationMetal

carbon layer

CO2

HClmediatedremoval

Metalimpurities

Pentagonal

Heptagonal

carbon

carbon

X2H2O2

2K2O2

2H2O

2H2O

O2HO∙ + OHminus

2KOH

4KOH

2KHO2

b

c

fd

e

a

(sonica

tion te

mp 50∘ C 5

h)






2+ 2H2O (2)











2O2




2O2





1198820

times 100 (3)





(a)

(c)

(b)

(d)













2O2treatments


2O2 and KOHH

2O2)






2O2(Figure 4(d))







Electron image 1

10120583m

cps (

eV)

C

MgO

Co

Co

AlN MnMn

0

0

5 10

10

20

15

(keV)

Spectrum 1Wt 120590

CONCoMnAlMg

9735 0202000001010000

112

048

03046

029

(a)

10120583m

C

OAlN

cps (

eV)

0

0

5 10

20

15

Spectrum 2

Wt 120590COAl

9877 02020001

113

Electron image 2

(keV)

(b)

10120583m

C

ON

cps (

eV)

0

0

5 10

20

40

15

Spectrum 3Wt 120590

CON

9878 02020000

122

Electron image 3

(keV)

(c)

10120583m

C

O

cps (

eV)

0

0

5 10

10

5

15

Mg

MnCo

AlN CoMn

Spectrum 4Wt 120590

CONCo

9519 0403000001

334

045MnAlMg

010000

03042

03

Electron image 4

(keV)

(d)








400 500 1000 1500 2000 2500 40003000 3500


Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast


(cmminus1)



10

08

06

04

02

00

Inte

nsity

DG



MWCNT-KOHH2O2

067081091073



2O2


2O2was




10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)


MWCNT-HClH2O2

MWCNT-KOHH2O2



2O2














2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




OH

OH

OH

OH

OH

OH

OH

OH

OHOHOH

Metal

OH

OHOO

O

OO

R

R

O

O

O

O

O

O

Highly pure

CNT skeleton

CNT skeleton

CNT

skele

ton

CNT

Less pureCNT


HClH2

O 2

KOHH2 O

2

H2O2HO∙ + OHminus

Amorphous

Amorphous

carbon oxidation

oxidationMetal

carbon layer

CO2

HClmediatedremoval

Metalimpurities

Pentagonal

Heptagonal

carbon

carbon

X2H2O2

2K2O2

2H2O

2H2O

O2HO∙ + OHminus

2KOH

4KOH

2KHO2

b

c

fd

e

a

(sonica

tion te

mp 50∘ C 5

h)






2+ 2H2O (2)











2O2




2O2





1198820

times 100 (3)





(a)

(c)

(b)

(d)













2O2treatments


2O2 and KOHH

2O2)






2O2(Figure 4(d))







Electron image 1

10120583m

cps (

eV)

C

MgO

Co

Co

AlN MnMn

0

0

5 10

10

20

15

(keV)

Spectrum 1Wt 120590

CONCoMnAlMg

9735 0202000001010000

112

048

03046

029

(a)

10120583m

C

OAlN

cps (

eV)

0

0

5 10

20

15

Spectrum 2

Wt 120590COAl

9877 02020001

113

Electron image 2

(keV)

(b)

10120583m

C

ON

cps (

eV)

0

0

5 10

20

40

15

Spectrum 3Wt 120590

CON

9878 02020000

122

Electron image 3

(keV)

(c)

10120583m

C

O

cps (

eV)

0

0

5 10

10

5

15

Mg

MnCo

AlN CoMn

Spectrum 4Wt 120590

CONCo

9519 0403000001

334

045MnAlMg

010000

03042

03

Electron image 4

(keV)

(d)








400 500 1000 1500 2000 2500 40003000 3500


Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast


(cmminus1)



10

08

06

04

02

00

Inte

nsity

DG



MWCNT-KOHH2O2

067081091073



2O2


2O2was




10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)


MWCNT-HClH2O2

MWCNT-KOHH2O2



2O2














2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(c)

(b)

(d)













2O2treatments


2O2 and KOHH

2O2)






2O2(Figure 4(d))







Electron image 1

10120583m

cps (

eV)

C

MgO

Co

Co

AlN MnMn

0

0

5 10

10

20

15

(keV)

Spectrum 1Wt 120590

CONCoMnAlMg

9735 0202000001010000

112

048

03046

029

(a)

10120583m

C

OAlN

cps (

eV)

0

0

5 10

20

15

Spectrum 2

Wt 120590COAl

9877 02020001

113

Electron image 2

(keV)

(b)

10120583m

C

ON

cps (

eV)

0

0

5 10

20

40

15

Spectrum 3Wt 120590

CON

9878 02020000

122

Electron image 3

(keV)

(c)

10120583m

C

O

cps (

eV)

0

0

5 10

10

5

15

Mg

MnCo

AlN CoMn

Spectrum 4Wt 120590

CONCo

9519 0403000001

334

045MnAlMg

010000

03042

03

Electron image 4

(keV)

(d)








400 500 1000 1500 2000 2500 40003000 3500


Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast


(cmminus1)



10

08

06

04

02

00

Inte

nsity

DG



MWCNT-KOHH2O2

067081091073



2O2


2O2was




10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)


MWCNT-HClH2O2

MWCNT-KOHH2O2



2O2














2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Electron image 1

10120583m

cps (

eV)

C

MgO

Co

Co

AlN MnMn

0

0

5 10

10

20

15

(keV)

Spectrum 1Wt 120590

CONCoMnAlMg

9735 0202000001010000

112

048

03046

029

(a)

10120583m

C

OAlN

cps (

eV)

0

0

5 10

20

15

Spectrum 2

Wt 120590COAl

9877 02020001

113

Electron image 2

(keV)

(b)

10120583m

C

ON

cps (

eV)

0

0

5 10

20

40

15

Spectrum 3Wt 120590

CON

9878 02020000

122

Electron image 3

(keV)

(c)

10120583m

C

O

cps (

eV)

0

0

5 10

10

5

15

Mg

MnCo

AlN CoMn

Spectrum 4Wt 120590

CONCo

9519 0403000001

334

045MnAlMg

010000

03042

03

Electron image 4

(keV)

(d)








400 500 1000 1500 2000 2500 40003000 3500


Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast


(cmminus1)



10

08

06

04

02

00

Inte

nsity

DG



MWCNT-KOHH2O2

067081091073



2O2


2O2was




10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)


MWCNT-HClH2O2

MWCNT-KOHH2O2



2O2














2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




400 500 1000 1500 2000 2500 40003000 3500


Tran

smitt

ance

(au

)

804

1044

1630

2279

2422

2907

3409 (a)

(b)(c)

(d)

lowastlowast


(cmminus1)



10

08

06

04

02

00

Inte

nsity

DG



MWCNT-KOHH2O2

067081091073



2O2


2O2was




10008006004002000

100

80

60

40

20

0

Wei

ght (

)

Temperature (∘C)


MWCNT-HClH2O2

MWCNT-KOHH2O2



2O2














2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




2120579 (deg)10 20 30 40 50 60

Inte

nsity

2120579 (deg)

002

100

10 20 30 40 50 60

Inte

nsity

(a)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(b)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(c)

002

100

2120579 (deg)10 20 30 40 50 60

Inte

nsity

(d)












2O2

4 Conclusions


2O2 and KOHH

2O2) is presented








Acknowledgments


References






















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










Acknowledgments


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 Common Wet Chemical Agents for Purifying ...

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