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Research ArticleCatalytic Reductive Degradation of Methyl Orange Using AirResilient Copper Nanostructures

Razium Ali Soomro12 Ayman Nafady34 Sirajuddin1 Syed Tufail Hussain Sherazi1

Nazar Hussain Kalwar12 Mohammad Raza Shah5 and Keith Richard Hallam2

1National Centre of Excellence in Analytical Chemistry University of Sindh Jamshoro 76080 Pakistan2Interface Analysis Centre School of Physics University of Bristol Bristol BS8 1TL UK3Department of Chemistry College of Science King Saud University Riyadh 11451 Saudi Arabia4Chemistry Department Faculty of Science Sohag University Sohag 82524 Egypt5International Centre for Chemical and Biological Sciences HEJ Research Institute of Chemistry University of KarachiKarachi 75500 Pakistan

Correspondence should be addressed to Nazar Hussain Kalwar nazarkalwargmailcom

Received 16 November 2014 Revised 26 December 2014 Accepted 27 December 2014

Academic Editor Xingcai Wu

Copyright copy 2015 Razium Ali Soomro 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

The study describes the application of oxidation resistant copper nanostructures as an efficient heterogeneous catalyst for thetreatment of organic dye containing waste waters Copper nanostructures were synthesized in an aqueous environment usingmodified surfactant assisted chemical reduction routeThe synthesized nanostructures have been characterized by UV-Vis Fouriertransform infrared spectroscopy FTIR spectroscopy Atomic force microscopy (AFM) Scanning Electron Microscopy (SEM)and X-ray diffractometry (XRD) These surfactant capped Cu nanostructures have been used as a heterogeneous catalyst for thecomparative reductive degradation of methyl orange (MO) in the presence of sodium borohydride (NaBH

4) used as a potential

reductant Copper nanoparticles (Cu NPs) were found to be more efficient compared to copper nanorods (Cu NRds) with thedegradation reaction obeying pseudofirst order reaction kinetics Shape dependent catalytic efficiency was further evaluatedfrom activation energy (119864

119860) of reductive degradation reaction The more efficient Cu NPs were further employed for reductive

degradation of real waste water samples containing dyes collected from the drain of different local textile industries situated inHyderabad region Pakistan

1 Introduction

Major scientific interest targeting fabrication of metal nanos-tructures of distinct shape and diminutive size has beendeveloped in recent years because of their exclusive propertiesas compared to their bulk counter parts [1ndash3] The capabilityto fashion metal nanostructures with variety of shapes andsizes allows for exploring their fascinating applications infields like catalysis electronics sensors optical devices andso on Most of the unique properties shown by metalnanostructures are a consequence of their nanosize scaleregime However recently it has been found that proper-ties of nanomaterials are also influenced by their shapefor example Jana and Murphy (2002) [4] reported shape

dependent surface plasmon resonance (SPR) peaks of silverand gold nanoparticles Similarly anisotropic behavior inoptical properties of copper nanorods has also been reportedby Henglein (1989) [5] Thus special shaped nanocompositematerials are the focus of present day scientific research Fromthe present literature perspective development of a feasiblesynthesis method for such nanomaterials is an importanttask Among all the methods employed today (radiationmethod [6] microemulsion method [7] thermal decompo-sition method [8] laser ablation method [9] and aqueouschemical reduction method [10]) the aqueous reductionroute is the most preferred for its simple and economicstrategy with high yield and quality of the desired productand ease of control over particle size and distribution with

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 136164 12 pageshttpdxdoiorg1011552015136164

2 Journal of Nanomaterials

various experimental parameters [11ndash14] Although a varietyof metal nanostructures are being employed for numerousapplications in various fields the use of nanosize metalstructures as a heterogeneous recyclable catalyst in differentenvironmental problems associated with hazardous wastesand toxic water pollutants pollution is the need of the day

The textile industry and its waste water have beenincreasing proportionally making it one of the main sourcesof severe water pollution worldwide [15] In particulardyes comprise a major section of industrial waste watereffluents as they are released in abundance up to 50 ofdyes may be lost directly into waterways due to inefficientand uneconomic dyeing techniques The release of suchchemicals in aquatic systems is of environmental concern dueto their carcinogenic persistent and recalcitrant nature [16]Dyes released in waste water may also undergo incompleteanaerobic degradation inducing additional toxicity causedby mutagenic end products Besides this coloring decreasessunlight penetration and oxygen dissolution in water whichis also a considerable threat to the aquatic ecosystem [17]In order to cope with increasingly strict legislations andregulations concerning waste water management the asso-ciated industries are required to find green efficient andeconomically viable waste water treatment methods Watertreatment methods include adsorption biological coagula-tion routes and ozonation [18] However these methodsare time-consuming expensive and inefficient and result insecondary pollution with overall increase in the method costbecause of the extra disposal procedures Advanced oxidationprocesses (AOPs) employing metal oxides such as TiO

2

and ZnO are technically feasible degradation processes butthe requirement for short wavelength light sources and lowquantum yields restrain their widespread acceptance as effi-cient and practical remediation processes [19ndash22] Recentlymultistep processes for significant advancement in practicalapplications regarding dye degradation have been reported[23] Among such processes reductive degradation of organicdyes with metal nanostructures is a convenient degradationmodel system which is not only viable in terms of efficiencyand costliness but also greener as it provides biodegradableend products like aromatic amines which are readily andeasily degraded by microorganisms [24] Hassan et al (2011)[25] reported the catalytic reduction of mixture of dyes usinggold nanoparticles within 15 s of reaction time Similarly Xuet al (2008) [26] used Pd nanoparticles with good catalyticproperties in the degradation of azo dyes Nafady et al (2011)[27] reported reductive degradation of methylene blue withcysteine capped gold nanoparticles in just 5min of reactiontime Ai and Jiang (2013) [28] used alginate hydrogel (AH)capped silver nanoparticles for the heterogeneous catalyticreduction of 4-nitrophenol by NaBH

4in aqueous solution

and Sau et al (2001) [29] addressed catalysis of eosinreduction in the presence of NaBH

4with Triton X-100 coated

gold nanoparticles From all the previous reports it is clearthat most of the relevant recent studies carried out in thefield of catalysis have focused on the use of transition metalslike silver gold and platinum with less understanding of theshape selective catalytic performance of NPs In addition thehigh cost and troublesome availability of these noble metals

restricts their applications in larger volume production Acheap metal like copper can serve as a suitable alternativewith its low cost easy availability and higher electronic andthermal conductivity compared to traditional noble metalslike silver gold and platinum [30] Interestingly some ofthe properties of special shaped copper nanoparticles aremuch greater than bulk copper thus synthesis of specialshaped copper nanoparticles is of interest However it isvery difficult to fabricate copper nanomaterials in aqueoussolution because of its easy oxidizing capability [31] Untilnow tremendous efforts are carried out for the preparationof pure metallic nanosized copper Petit et al (1993) [32] haveused the microemulsion based method to stabilize metalliccopper nanoparticles Cao et al (2003) [33] synthesizedcopper nanorods in high yield using a composite templateof polyethylene glycol (PEG) and cetyltrimethylammoniumbromide (CTAB) Joshi et al (1998) [6] used oxygen freeatmosphere to prevent oxidation of copper nanoparticles inaqueous medium Similarly Park et al (2007) [34] addressedthe use of polymer like PVP for the prevention of oxidationand aggregation of copper nanoparticles However most ofthese recent strategies employ oxygen free environmentsand heavy molecular weight polymers as protecting agentslimiting the usage of copper nanoparticles in aqueous medi-ums with restrained catalytic efficiency as heavy polymermolecules block large areas of active sites

Although successful synthesis of copper nanoparticleshas been carried out via numerous routes [40] much lessis known about the mechanism concerning control of shapeand size at the nanoscale level with the basic understandingof shape dependent performance of copper nanostructuresas a suitable catalyst We recently showed the formation ofspherical copper nanoparticles in aqueous medium employ-ing SDS surfactant as a protecting agent with its application inreduction of eosin B dye used as a standard pollutant [41]Thestudy clearly indicated the application of such nanoparticlesin real waste remediation and thus due to such considera-tion extended work was carried out in understanding theformation and wider real application of copper nanostruc-tures as a catalyst for waste water remediation Thus thepresent study is an extended version of our previous reporttargeted towards the application of copper nanostructuresfor comparative catalytic reductive degradation of model azodye methyl orange (MO) to determine the shape influenceof copper nanostructures on catalytic kinetic and energeticbehaviorsThe study also compares the basic mechanism thatgoverns the shape of stable copper nanostructures betweennanoparticles and nanorods using surfactants like SDS andCTAB in aqueous solution In addition the universal natureof copper nanostructures as catalysts was also highlighted byemploying highly efficient copper nanoparticles for reductivedegradation of real dyeingwastewater samples collected fromdifferent regions of Hyderabad city Pakistan which to thebest of our knowledge has not been reported before

2 Experimental

21 Materials All chemicals used were of analytical gradeand were used without further purification by employing

Journal of Nanomaterials 3

pure Milli-Q water as the preparatory medium Copper (II)chloride (CuCl

2sdot5H2O (97)) sodium dodecyl sulfate (SDS

(98)) cetyltrimethylammonium bromide (CTAB (98))vitamin C (C

6H8O6(98)) and MO (C

14H14N3NaO3S

(99)) were purchased from E Merck and sodium borohy-dride (NaBH

4(98)) sodiumhydroxide (NaOH (98)) and

hydrochloric acid (HCl (37)) were from Sigma-Aldrich

22 Preparation of Copper Nanostructures Surfactant cappedcopper nanostructures were synthesized via an aqueousreduction route SDS capped copper nanoparticles (Cu NPs)were prepared as mentioned in our previous work [41]However slight changes in the optimum amount of precursoringredients were made to obtain best nanosize particles withmaximum catalytic performance In the typical synthesis ofcopper nanoparticles optimized amounts of ingredients wereused 05mLof 002Mcopper (II) chloride salt (CuCl

2sdot5H2O)

was taken in a test tube To this was added 10 120583L of 10Msodium dodecyl sulfate (SDS) followed by the addition of01mL of 01M ascorbic acid (vitamin C) The mixturevolume was adjusted to 90mL with deionized water andfinally 03mL of 001M sodium borohydride (NaBH

4) was

added slowly To ensure complete reduction and cappingof copper nuclei after reduction reaction was allowed toproceed for about 15min With similar methodology CTABcapped copper nanorods (Cu NRds) were also synthesizedby taking 01mL of 003M copper (II) chloride solution ina similar test tube followed by addition of 30 120583L of 01Mcationic surfactant CTAB 01mL of 01M ascorbic acid(vitamin C) was added as a quenching agent and the mixturewas diluted with deionized water up to 90mL Reductionwas carried out by the addition of 03mL of 001M sodiumborohydride (NaBH

4) slowly down the walls of the test tube

This process was repeated several times to obtain stablesurfactant capped copper nanostructures which were furtherused for characterization and application

The proposed ionic mechanism for the reduction of Cu2+to Cu0 with sodium borohydride is given as follows

Cu2+ + 2BH4

minus997888rarr Cu +H

2+ B2H6

(1)

23 Characterization UV-Vis spectroscopy (Lambda 35 ofPerkinElmer) was used for tracing SPR of surfactant cappedcopper nanostructure in the spectral range of 200ndash800 nmwith the scan rate of 1920 nm sminus1 Surface interaction studybetween surfactants and copper nanostructures was carriedout with Fourier transform infrared spectroscopy (FTIR)(Nicolet 5700 of Thermo) using the KBr pelleting methodand solid samples were obtained after parching colloidaldispersions of as-synthesized Cu nanostructures under nitro-gen atmospheres Morphological characterization with sizedetermination was performed using Atomic force microcopy(AFM) (Agilent 5500) and Scanning Electron Microscopy(SEM) (Jeol Japan) on freshly cleaved mica and carbon tapesurface respectively Phase purity and crystalline patterns forCu nanostructures were studied using X-ray diffractometry(XRD) (D-8 of Bruker)

24 Catalytic Test for Reductive Degradation of Dye In arepresentative degradation experiment 1mg of SDS cappedCu NPs or CTAB capped Cu NRds was deposited onpreweighted glass cover slips and dried under nitrogenousatmospheres for complete adhesion to the surface Thesecover slips with specific amounts of copper nanostructureswere further used in heterogeneous reductive degradation ofmodel azo dye (MO) and real dyeing waste water samplesFor an uncatalyzed reaction an aqueous solution of 100mM(MO) was taken in a 4mL capacity quartz cuvette along with10mM of (NaBH

4) reducing agent The reaction mixture was

studied for some time with an UV-Vis spectrophotometerat room temperature and atmospheric pressure In a sim-ilar manner for catalyzed reaction glass cover slips withappropriate amounts of surfactant capped Cu nanostructureswere placed inside the sample container already containingmodel dye and reductant (NaBH

4) solution The catalyzed

reaction was followed by measuring the time-dependent fallin absorbance (Abs) at 556 nm The kinetic study of thereductive degradation procedure was performed at constanttemperatures and atmospheric pressure with the calculationof activation energy for nanostructures Degradation of realdyeing waste water samples was carried out with the mostefficient copper nanostructure (SDS capped Cu NPs) Thereductive degradation experiment used the optimum amountof SDS capped Cu NPs (05mg) previously deposited ona clean glass cover slip This specific amount was furtherintroduced in a mixture containing 10120583L of real waste watersample and 10mM reductant (NaBH

4) diluted up to the total

volume of 35mL with deionized water

3 Results and Discussion

31 Optical Characterization Recent advances have allowedmetals to be structured on the nanoscale by engineeringthe surface plasmon modes of metallic nanostructures [42]Surface plasmons are collective excitations of the electronsat the interface of a metal surface resulting in absorptionof electromagnetic waves [43] This interesting phenomenondominates when particle size is brought within the nanoscaleregime In recent years several studies have shown thatoptical properties of metal nanoparticles depend on thegeometry and size thus the optical response of metalnanoparticles (NPs) can be tuned to control shape and size ofmetal nanostructure [43 44] Since surface plasmon modesof metallic nanoparticles like Au Ag and Cu reside withinthe optical region of the electromagnetic spectrum [42 45]optical spectroscopy can be used as a primary tool for theinvestigation of such nanoparticles UV-Vis spectral profilesfor Cu NPs were recorded with timeThe SPR band observedat 569 nm shows the completely reduced (rich red) colloidalsol as depicted in Figure 1(a)

The absorption spectra have been simulated for sphericalcopper particles by various earlier reports [30 46 47]As our absorption spectrum is in close resemblance weconclude that copper nanoparticles were formed in this studySimilarly the SPR band for Cu NRds (dark reddish brown)was recorded at 545 nm (Figure 1(b)) with an increase in

4 Journal of Nanomaterials

400 500 600 700 800000

025

050

075

100

Cu NRdsCu NPs

Abso

rban

ce

Wavelength (nm)

Cu NPs Cu NRds

569nm

(a)

(b)

545nm

Figure 1 SPR bands of (a) SDS capped Cu NPs and (b) CTABcapped Cu NRds

band width compared to the narrow SPR band of Cu NPsit is well established that SPR band position and width arehighly influenced by particle shape and size [48] Thereforethe PWHM (peak width half-maximum) was calculated forboth as-synthesized copper nanoparticles and nanorodsThePWHM value obtained for Cu NPs (70) of 100 nm indicatesuniform distribution of particle size However for Cu NRds(118) the value is above 100 nm which demonstrates largevariance in structural size resulting in broad SPR bandwidths In this case increased band width may be the resultof considerable interactions between nanoparticles fromhigher order multipoles and distribution of depolarization asnanoparticles assemble in the form of rod-shaped structuresduring nucleation It is interesting to note that the observedcolor of the Cu NRds (reddish brown) can also be describedas a rangemixture of colors depending on the variance in sizeof nanorods

32 Fourier Transform Infrared Spectroscopy (FTIR) FTIRspectroscopy can provide vital information concerning sur-face interactionsThe FTIR spectrum of nanoparticles differsconsiderably from that of the bulk counterpart [49] In thecase of nanoparticles the surface to volume ratio is very highwhen compared to bulk form thus the number of atoms thatconstitute the surface can influence the vibration spectra ofnanoparticles [49 50] In order to understand the basics ofsurface interactioncapping between copper nanostructuresand surfactants FTIR spectra were recorder in the range of4000ndash400 cmminus1 Figure 2 shows FTIR spectra of SDS cappedCu NPs and CTAB capped Cu NRds the FTIR spectra ofpure surfactants are also present for comparison In the caseof SDS capped Cu NPs Figure 2(c and d) the characteristicvibrational bands of pure SDS can be divided into tworegions concerning its hydrophobic and hydrophilic natureTwin absorption peaks in the range of 2950ndash2850 cmminus1 are

4000 3500 3000 2500 2000 1500 1000 500

Abso

rban

ce (a

u)

CTABCTAB capped Cu NRds

SDS SDS capped Cu NPs

(d)

(c)

(b)

(a)

Wavenumber (cmminus1)

1226 cmminus1

1234 cmminus1

3030 cmminus1

3020 cmminus1

Figure 2 FTIR spectra of (a) standard CTAB (b) CTAB capped CuNPs (c) standard SDS and (d) SDS capped Cu NRds

attributed to aliphatic group (tail group) and another bandat 1226 cmminus1 is attributed to sulfonic acid (head group) ofthe surfactant [51] Blue shift in the characteristic absorptionband of the sulfonic acid group from 1226 cmminus1 in pure SDSto 1234 cmminus1 (Figure 2(d)) suggests that the copper nanopar-ticles were capped by the head group moiety Furthermorethe absence of the characteristic bands around 623 588534 and 480 cmminus1 excludes the possibility of Cu

2O and

CuO impurities respectively [52 53] In the case of CTABcapped Cu NRds Figure 2(a and b) we understand thatintensive vibration bands of CTAB can also be categorizedinto two different regions such as the bands associated withmethylene tails of surfactant molecules and bands whichare associated with alkyl ammonium head groups [54] Acharacteristic peak around 3018 cmminus1 as shown in Figure 2(a)can be assigned to the symmetric stretching mode of thetrimethylammonium head group (CH

3)3N+ of the surfactant

molecules and the most intensive peaks around 2917 and2847 cmminus1 are associated with asymmetric and symmetricstretching vibration modes of the methylene group A slightshift in the frequency of band associated the head groupfrom 3018 cmminus1 to 3025 cmminus1 and (Figure 2(b)) suggests thatthe growth of Cu NRds is restricted via interaction of thehead group [(CH

3)3N+] with the surface of copper However

the difference in critical micelle concentration (CMC) ofthe two surfactants and the nature of interaction allowedthe directional growth of particles towards self-assemblednanorods in aqueous CTAB medium

33 Atomic Force Microscopy (AFM) Surface morphologyplays an important role in the field of catalysis Atomicforce microscopy (AFM) is a powerful technique that canprovide direct spatial mapping of surface morphology withnanometer resolution It requires no specific sample prepa-ration procedures and is easy to interpret and allows for

Journal of Nanomaterials 5

09

08

07

06

05

04

03

02

01

0

0908070605040302010

Y(120583

m)

X (120583m)

1000

(nm

)

000

(a)

(120583m)(120583m)

20

0(nm

)

08

06

04

02

08

06

04

02

0

(b)

09

08

07

06

05

04

03

02

01

0

0908070605040302010

Y(120583

m)

X (120583m)

3000

(nm

)

000

(c)

(120583m)

(120583m)

200(n

m)

08

06

04

02

08

06

04

02

(d)

Figure 3 AFM images of Cu nanostructures (a) typical medium scale AFM image (09 times 09 120583m) (b) topographical map of the SDS cappedCu NPs (c) typical medium scale AFM image (09 times 09 120583m) and (d) topographical map of the CTAB capped Cu NRds

the study of morphological characteristics of samples ina nondistractive way [55] The tapping modes of AFMimagining were developed especially for studying both SDScapped Cu NPs and CTAB capped Cu NRds Figure 3(a)shows a typical medium scale AFM image (09 120583m times 09 120583m)of the SDS capped Cu NPs with spherical and uniformshape whereas a topographical map of nanoparticles ispresented in Figure 3(b) where rough surface morphologywith dents and irregularities are indicated by highlightedregions Such rough surfaces have greater number of activesites which provide greater number of contact points forcatalysis [56 57] SEM analysis was carried out to get furtherinsight and determine the exact particle size of Cu NPsFigure S1(a) in Supplementary Material available online athttpdxdoiorg1011552015136164 shows the SEM imagewith high distribution of as-synthesized Cu NPs It canbe seen that most nanoparticles are highly dispersed withspherical shape morphology The average particle diametercalculated from SEM analysis was about 35 plusmn 28 nm inthe scale range of 15ndash40 nm The number of surface atomsper nanoparticle calculated in Table 1 clearly suggests that

Cu NPs have greater numbers of atoms at the surfaceas compared to nanorods In a similar pattern Cu NRdswere also characterized for morphology Figure 3(c) shows amedium scale AFM image of CTAB capped Cu NRds wherehigh surface roughness is evident The SEM image of as-synthesized Cu NRds is presented in Figure S1(b) It can beseen that the formed nanorods are very well dispersed withnegligible aggregation We assume that considerable interac-tion between small nanodots during nucleation mediated bythe surfactant resulted in a self-assembly of particles towardsrod-shaped structures This issue is further discussed later inSection 35 The average width of nanorods estimated fromSEM analysis was determined to be 65 plusmn 38 nm with anaverage aspect ratio of 95 Such a high aspect ratio alongwith irregular surface topography as depicted in Figure 3(c)allows nanorods to create a network of surfaces in the reactionmedium leading to increased physical contacts betweencatalyst and reactants molecules

34 X-Ray Powder Diffraction (XRD) The X-ray diffrac-tograms of surfactant capped Cu NPs and NRds are shown

6 Journal of Nanomaterials

Inte

nsity

(au

)

2 2

02 0

0

1 1

1

30 35 40 45 50 55 60 65 70 75 80 852120579 scale

(a)

30 35 40 45 50 55 60 65 70 75 80 85

Inte

nsity

(au

)

2 2

02 0

0

1 1

1

2120579 scale

(b)

Figure 4 XRD patterns of (a) Cu NPs and (b) Cu NRds

in Figures 4(a) and 4(b) respectively The characteristicMiller indices (1 1 1) (2 2 0) and (2 2 0) lattice planeswere observed for both Cu NPs and Cu NRds The datarefer to pure copper metal with face centered cubic structure(FCC) No characteristic peaks indexed to copper oxide wereobserved indicating the phase purity of copper metal Theresults obtained are in strong corelationwith previous reports[58 59] However differences in intensity and broadness incorresponding peaks were evident The measured intensityratio of diffraction peaks indexed as (1 1 1) and (2 0 0)between CuNPs and CuNRds was 196 and 172 respectivelyThis increased ratio for (1 1 1) planes refers to the exposedfacets along the crystal surface of copper nanoparticlesand relatively strong diffraction intensity compared to CuNRds This may be a consequence of an isotropic growthof particular planes during the nucleation step which hasbeen manifested from their particle and rod-like structuralshapes In addition increased broadness in XRD peak widthsof Cu NPs relative to Cu NRds suggests smaller grain sizerespectively

35 Growth Mechanism for Copper Nanostructures Experi-mental studies were carried out for [Cu] and [SDS] at 1 1ratio which resulted in stable blood red colored coppernanoparticles with an SPRband at 569 nmThemechanismofformation for SDS capped Cu NPs is explained in Figure S2At concentration of 1mMwhich is approximately eight timeshigher than CMC (8 times 10minus3M) of SDS surfactant aqueousmedium is rich in SDS micelles thus a large population ofcopper ions are gathered at the negatively charged head groupof the surfactant as a result of electrostatic attraction betweenoppositely charged copper ion and surfactant head group asshown in Figure S2(a) As the electron transfer starts withthe abrupt addition of reducing agent (NaBH

4) explosive

nucleation occurs consumingmost of the precursor ions andaggregation of small metal nuclei at the very instant as aconsequence of strong interaction between their magnetic

dipoles However due to the presence of a dense micellenetwork and strong interaction between oppositely chargedgroupsmost of the nucleation occurswithin the SDSmicelleswhich restricts the growth of particles by adsorbing onto thesurface This adsorption of surfactant around nanoparticlesresults in an overall decrease in grain boundary energywhich is highly related to surface energy Thus decreasingthe grain boundary energy would result in a decrease indriving force for particle growth (Figure S2(bndashd)) AFMand SEM studies indicate the formation of spherical coppernanoparticles at [Cu2+] [SDS] having 1 1 ratio as shown inFigure 3(a) The results are in contrast to those obtained withCTAB at a similar ratio [Cu2+] [CTAB] = 1 1 where coppernanorods are obtained The formation of copper nanorodscan be explained as presented in Figure S3 We know thatCTAB is a cationic surfactant thus at concentrations aboveCMC the precursor ions are mostly located in the micelleshead group due to the presence of the counter ion Brminus(Figure S3(a)) not within the micelle network as proposed inFigure S2 With the introduction of reducing agent (NaBH

4)

subsequent unidirectional nucleation occurs as one side ofthe particles is no longer free due to the presence of micelle(Figure S3(b and c))This restriction results in unidirectionalgrowth of particle along the specific facets that are exposed towater ultimately leading to the formation of rod-like struc-tures from the self-assembly of small nanoparticles (FigureS3(d)) The growth mechanism is in correspondence with arecently published report on copper nanorods [45] Basedon an aforementioned mechanism we conclude that coppernanoparticles and nanorods are both formed by a similarprocess that is surfactant directed growth However differ-ences in directional growth of nanostructures arise becauseof difference in nature charge and micelle size In additionwe also argue that the formation of copper nanostructuresis through a template free route with surfactants used asstabilizers and growth directors It is quite unlikely that rod-like CTAB micelles and SDS associated rod-like structuresmay form in the absence of additives like sodium salicylate

Journal of Nanomaterials 7

and anilinium nitrate as it is evident from the previouslypublished reports [60 61]

36 Catalytic Evaluation of Copper Nanostructures for Degra-dation of MO The catalytic performance for both SDScapped Cu NPs and CTAB capped NRds was monitoredtaking MO dye as a model compound for organic azo dyesThe progression of the reductive degradation of MO can beeasily studied by following the decline in time-dependentabsorbance at 550 nm as shown in Figure 5 The uncatalyzedreaction (Figure 5(a)) was carried out to assess the capabilityof reductantNaBH

4(10mM) alonewithMO (100 120583M)which

showed only a small percentage of degradation (up to 85)with time In contrast catalyzed reaction carried out withsurfactant capped copper nanostructures that is CuNPs andCuNRds in a similar sample solution suggested the completereductive degradation of MO dye (100) within 60 and 180 sof reaction time respectively (Figures 5(b) and 5(c)) Thereaction rate for MO degradation with copper NPs and CuNRdswas enhanced 112 and 75 times respectively comparedwith the results of the control experiment

The rate of reaction for the heterogeneous catalysis is bestdescribed by the LangmuirndashHinshelwood (LndashH) model [62]which has the following mathematical formula [18]

minus119889119888

119889119905=119896119871minus119867119896ad119862

1 + 119896ad119862 (2)

where 119896119871minus119867

is the reaction rate constant 119896ad is the adsorptioncoefficient of dye on catalyst and119862 is the variable concentra-tion at any time 119905 For pseudo first-order reaction the valueof 119896 ad 119862 is very small as compared to 1 in the denominatorof (2) So by integrating (2) for simplification we obtain

ln(1198620

119862) = 119896119871minus119867119896ad119905 = minus119896119905 (3)

Here 1198620is the initial concentration and 119896 = 119896

119871minus119867119896ad is the

pseudo first-order reaction rate constantFigure 6 shows the plot with linear relationship of natural

logarithm of ratio of initial concentration of MO and relativeremaining concentration after reductive degradation versusthe corresponding reaction time (s) Linear regression anal-ysis was used to evaluate the reaction rate constants for thereductive degradation of MO by surfactant capped coppernanostructures Rate constant 119896 was found to be 0056 plusmn0001 and 0036 plusmn 00015 sminus1 for the corresponding catalyticreductive degradation of MO by Cu NPs and Cu NRdsrespectively The 1198772 values clearly suggest that the removalof MO seems to fit pseudo first-order kinetics

Differences in catalytic performance between SDS cappedCu NPs and CTAB capped Cu NRds can also be explainedbased on the difference in the nanostructure-support contactarea that is dependent on the particles shape and size It isknown that many catalytic processes occur at the perimeterinterface around the nanoparticles where the fraction of stepsites increases significantly with decreasing particle size [63]Here Cu NPs were found to have degraded MO 15 timesfaster than CuNRds thus such enhancement in reaction rate

is a function of two major factors number of surface atomsper nanoparticle and activation energy

Comparatively the larger numbers of surface atoms of CuNPs (323025) than ofCuNRds (121457)would provide greaternumbers of low coordination sites (sharp corners and edges)over the surface of the nanocatalyst In contrast for CuNRdsit can be understood that particles at connecting interfacesof rods are much less exposed to the surface resulting indecreased numbers of low coordinated sites compared to theindependent spherical Cu nanoparticles which have all sitesexposed as surface and available for coordination Also thelarger size of Cu NRds provides low surface coverage per unitvolume in the reaction mixture whereas for Cu NPs theirsmaller size and homogenous distribution provides increasednumbers of contact sites for the reactant molecules per unitvolume within the reaction medium

The shape effect of copper nanostructures on the activa-tion energy of reductive degradation of MOwith NaBH

4was

evaluated via catalytic experiment conducted as a function ofthree different temperatures (35∘C 45∘C and 50∘C) for bothSDS capped Cu NPs and CTAB capped Cu NRds For eachexperiment absorption spectra in the range of 400 to 700 nmwere recorded at different time intervals The effective rateconstant values for both CuNPs andCuNRds were evaluatedas a function of temperature as follows Cu NPs 014 plusmn 002025 plusmn 001 and 028 plusmn 005 sminus1 and Cu NRds 010 plusmn 001021 plusmn 002 and 027 plusmn 001 sminus1 at 30∘C 40∘C and 55∘Crespectively The obtained values were used in the followinglinear form of the Arrhenius equation to estimate apparentactivation energy

ln 119896 = minus119864119886

119877times1

119879+ ln119860 (4)

where 119864119886is activation energy 119879 is the absolute temperature

and 119877 is the universal gas constant A linear plot of ln 119896versus 1119879 was obtained for degradation carried out withSDS capped Cu NPs and CTAB capped NRds and the valueof the apparent activation energy was estimated from thelinear regression as shown in Figure 7 The activation energyobtained for the reaction carried out with Cu NPs (21 +10 kJmolminus1) is much smaller compared to 119864

119886value obtained

for the reaction carried out with Cu NRds (33 + 12 kJmolminus1)The significantly lower apparent activation energies obtainedwith SDS capped Cu NPs then a CTAB capped NRds maybe attributed to the rough surface morphology of spheri-cal copper nanoparticles that offer higher numbers of lowcoordination sites from all three dimensions belonging tothe nanosize regime Many studies have shown that the ratioof corner and edge atoms increases with the decrease ofcrystal size [64ndash66] At the nanoscale edge and corner atomsexhibit open coordination sites thatmay result in significantlydifferent bond enthalpies and desorption energies comparedto macrostructures In contrast Cu NRds have large sizesand lower surface coordination sites as indicated from theirsmaller number of surface atoms per nanoparticle Thusvariation in surface morphology when shape of particleschanges from spherical to rod is responsible for changesin activation energy of the overall system Some literaturedata on decolorization of MO dye by different methods

8 Journal of Nanomaterials

200 300 400 500 60000

05

10

Abso

rban

ce

Wavelength (nm)00min05min

10min15min

(a)

200 300 400 500 60000

05

10

Abso

rban

ce

Wavelength (nm)

20 s40 s

60 s80 s

00 s

(b)

200 300 400 500 60000

05

10

Abso

rban

ce

Wavelength (nm)80 s100 s120 s

60 s40 s20 s00 s

(c)

Figure 5 UV-Vis spectral profiles for (a) uncatalyzed reduction of 100 120583M (MO) with 500 120583L 001M (NaBH4) and (b) and (c) catalyzed

reductive degradation of MO in a similar sample environment with SDS capped Cu NPs and CTAB capped Cu NRds respectively

comparative with that obtained in this paper are summarizedin Table 1

Table 1 shows that all the parameters tested for thecatalytic system used in this paper are more effective thanthose of the previously reported methods Small amounts ofcatalyst (1mg surfactant capped Cu nanostructures) 100mMreductant NaBH

4 low activation energy (119864

119886= 21 plusmn 10

and 33 plusmn 12 kJmolminus1) with advanced reductive degradationachieved in just 80 and 120 s for Cu NPs and Cu NRdsrespectively at room temperature andpressure provide a clearedge over reports listed in the literature

37 Reductive Degradation of Real Dyeing Waste Water Sam-ples The universality of surfactant capped copper nanos-tructures as a heterogeneous catalyst for dye degradationwas examined by degrading real waste water dye containingsamples However the degradation was carried out onlywith SDS capped Cu NPs because of their higher efficiencycompared to CTAB capped Cu NRds Real waste watersamples were collected from drains of three different localtextile industries of Hyderabad region Catalytic degradationwas performed with a similar methodology as mentionedabove with optimized weight of Cu NPs (05mg) and 05mL

Journal of Nanomaterials 9

Table 1 Comparative results obtained for MO degradation and decolorization by various methods

Degrading system Reaction conditions Observations References

Gold silver nanocoresilicananoshell (photocatalyticsystem)

[catalyst] = 500mg Lminus1[MO] = 50 ppmSize (SiO2 = 30 nm)(Core shell Ag NPs = 20 nm)(Core shell Au NPs = 15 nm)

119870 = 001 plusmn 0001 0023 plusmn 00002 0035plusmn 00005minminus1 for SiO2Au NPs and Ag NPs respectively100 degradation after 120 70 and65min for SiO2 Au NPs and Ag NPsrespectively

[35]

Nanosized ZnO(photocatalyst)

[ZnO] = 25 g Lminus1 (calcined at550∘C for 120min)[MO] = 5 to 50mg Lminus1Average size = 20 nm

119870 = 00631 plusmn 000035minminus1100 degradation after 120min [36]

GT-Fe NPs(fenton-like catalyst)

[GT-Fe NPs] = 500mg[H2O2] = 50mL of 100[MO] = 500mg Lminus1Size 40ndash60 nm range

119870 = 0019 plusmn 00002minminus1100 degradation after 360min [37]

Nanoscale zerovalent IronParticles (NZVI)

[NZVI] = 3 g Lminus1[MO] = 114mg Lminus1Size 50ndash100 nm

119870 = 034 plusmn 0004minminus1119864119860= 23 plusmn 15 kJmolminus1

100 degradation after 24min[38]

Electrochemical-assistedphotodegradation on TiO2thin films

[TiO2] = 20mg[MO] = 10 ppm

119870 = 0219 plusmn 000025minminus1119864119860= 1863 plusmn 35 kJmolminus1

100 degradation after 120min[39]

In this study

[Cu NPs] [Cu NRds] = 01mg[MO] = 100 uM[NaBH4] = 10mMSize Cu NPs = (average width = 20 nmand average height = 37 nm)Cu NRds = (average width = 48 nm andaverage height = 14 nm)

[Cu NPs] = 119870 = 0032 plusmn 0001 sminus1119864119860= 21 plusmn 10 kJmolminus1100

degradation after 80 sec[Cu NRds] = 119870 = 0056 plusmn 00015 sminus1119864119860= 33 plusmn 12 kJmolminus1

100 degradation after 120 s

0 20 40 60 80 100 120Time (s)

Cu NRdsCu NPs

minus14

minus13

minus12

minus11

minus10

minus9

0032 sminus1

0056 sminus1

R2 = 0998

lnCoC

R2 = 0996

Figure 6 Linear regression plot showing pseudo first-order kineticsfor the Cu nanostructure catalyzed reductive degradation of MOwith SDS capped Cu NPs and CTAB capped NRds

of 100mM (NaBH4) reductant and 10 120583L of real sample

diluted up to 03mL with deionized water was used for thestudy of real environmental samples Figure S4 shows UV-Vis spectra for the reductive degradation of real samples

Cu NPsCu NRds

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10

55∘C

40∘C

lnk

31 32 33times10minus3

30∘C

1T (Kminus1)

Figure 7 Linear regression for Arrhenius equation with estimationof corresponding activation energy for surfactant capped Cu NPsand NRds

Complete degradation was observed in very short reactiontime for each sample irrespective of their chemical natureand color intensities indicating the high efficiency andcomprehensive nature of Cu NPs as a catalyst Figure S4(a

10 Journal of Nanomaterials

b and c) represents the spectra for an uncatalyzed controltest with very small decrease in the absorbance with reactiontime In contrast catalyzed tests in Figure S4(d e and f)show excellent reductive degradation (100)with time Smalldifferences between the reaction rates can be explained on thebasis of structural difference and concentration of various dyemolecules present in each real sample

4 Conclusions

From the above experimental results we conclude thatsurfactant capped Cu nanoparticles and nanorods can beefficiently synthesized in an aqueousmedium via a surfactantassisted wet-chemical reduction route The study is uniqueas we have shown the formation of copper nanostructureswith directional growth using long alkyl chain containingsalts compared to the conventional common seed-mediatedstrategy Another aspect of this study highlights the basicmechanism for shape variation of the copper nanostructuresin aqueous surfactant medium and depicts the formationto be based on concentration [surfactant] to [copper ion]ratio nature of surfactant micelle size and alignments ofthe initially formed particles Shape and size dependentcatalytic activity of copper nanostructures is also evaluatedby degradingmethyl orange in the presence ofNaBH

4used as

a reductant under ambient reaction conditions Comparisonhas been made to show their different catalytic performancein terms of kinetic and thermodynamic parameters Coppernanoparticles were found to be a highly efficient catalystas compared to copper nanorods because of their smallerwork functions and high number of surface atoms Lastlythe universal nature of copper nanostructures as a catalystwas demonstrated by efficiently degrading real dyeing wastewater samples with copper nanoparticles collected fromdrainage of local industries situated in Hyderabad regionPakistanThe study could be extended to all types of reductivedegradation of other dyes as well as other pollutants in wastewater research

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors acknowledge the Higher Education Commis-sion Islamabad Pakistan and the National Centre of Excel-lence in Analytical Chemistry University of Sindh JamshoroPakistan for provision of financial assistance and facilitiesduring this research The authors equally highly thankand cordially appreciate the financial support by King SaudUniversity for provision of funding via their Research Projectno RGP-VPP-236

References

[1] K Mallick M J Witcomb and M S Scurrell ldquoPreparationand characterization of a conjugated polymer and copper nano-particle compositematerial a chemical synthesis routerdquoMateri-als Science and Engineering B Solid-StateMaterials for AdvancedTechnology vol 123 no 2 pp 181ndash186 2005

[2] R Das S S Nath and R Bhattacharjee ldquoLuminescence ofcopper nanoparticlesrdquo Journal of Luminescence vol 131 no 12pp 2703ndash2706 2011

[3] M Abdulla-Al-Mamun Y Kusumoto and M Muruganand-ham ldquoSimple new synthesis of copper nanoparticles inwateracetonitrile mixed solvent and their characterizationrdquoMaterials Letters vol 63 no 23 pp 2007ndash2009 2009

[4] C J Murphy and N R Jana ldquoControlling the aspect ratio ofinorganic nanorods and nanowiresrdquo Advanced Materials vol14 no 1 pp 80ndash82 2002

[5] A Henglein ldquoSmall-particle research physicochemical prop-erties of extremely small colloidal metal and semiconductorparticlesrdquo Chemical Reviews vol 89 no 8 pp 1861ndash1873 1989

[6] S S Joshi S F Patil V Iyer and S Mahumuni ldquoRadiationinduced synthesis and characterization of copper nanoparti-clesrdquoNanostructuredMaterials vol 10 no 7 pp 1135ndash1144 1998

[7] J N Solanki R Sengupta and Z V P Murthy ldquoSynthesis ofcopper sulphide and copper nanoparticles with microemulsionmethodrdquo Solid State Sciences vol 12 no 9 pp 1560ndash1566 2010

[8] Y H Kim Y S Kang W J Lee B G Jo and J H JeongldquoSynthesis of Cu nanoparticles prepared by using thermaldecomposition of Cu-oleate complexrdquo Molecular Crystals andLiquid Crystals vol 445 pp 231ndash238 2006

[9] Z Yan R Bao C Z Dinu Y Huang A N Caruso andD B Chrisey ldquoLaser ablation induced agglomeration of Cunanoparticles in sodium dodecyl sulfate aqueous solutionrdquoJournal of Optoelectronics and Advanced Materials vol 12 no3 pp 437ndash439 2010

[10] Q-M Liu T Yasunami K Kuruda andMOkido ldquoPreparationof Cu nanoparticles with ascorbic acid by aqueous solutionreductionmethodrdquo Transactions of NonferrousMetals Society ofChina vol 22 no 9 pp 2198ndash2203 2012

[11] Q-M Liu R-L Yu G-Z Qiu Z Fang A-L Chen and Z-W Zhao ldquoOptimization of separation processing of copper andiron of dump bioleaching solution by Lix 984N in DexingCopper Minerdquo Transactions of Nonferrous Metals Society ofChina vol 18 no 5 pp 1258ndash1261 2008

[12] H-T Zhu C-Y Zhang and Y-S Yin ldquoRapid synthesis ofcopper nanoparticles by sodium hypophosphite reduction inethylene glycol under microwave irradiationrdquo Journal of CrystalGrowth vol 270 no 3-4 pp 722ndash728 2004

[13] O Coussy and T Fen-Chong ldquoCrystallization pore relaxationand micro-cryosuction in cohesive porous materialsrdquo ComptesRendusmdashMecanique vol 333 no 6 pp 507ndash512 2005

[14] A A Athawale P P Katre M Kumar and M B MajumdarldquoSynthesis of CTAB-IPA reduced copper nanoparticlesrdquo Mate-rials Chemistry and Physics vol 91 no 2-3 pp 507ndash512 2005

[15] K-SWang C-L LinM-CWei et al ldquoEffects of dissolved oxy-gen on dye removal by zero-valent ironrdquo Journal of HazardousMaterials vol 182 no 1ndash3 pp 886ndash895 2010

[16] Y He J-F Gao F-Q Feng C Liu Y-Z Peng and S-Y WangldquoThe comparative study on the rapid decolorization of azoanthraquinone and triphenylmethane dyes by zero-valent ironrdquoChemical Engineering Journal vol 179 pp 8ndash18 2012

Journal of Nanomaterials 11

[17] M A Rauf M A Meetani and S Hisaindee ldquoAn overview onthe photocatalytic degradation of azo dyes in the presence ofTiO2doped with selective transition metalsrdquo Desalination vol

276 no 1ndash3 pp 13ndash27 2011[18] Z Sun Y Chen Q Ke Y Yang and J Yuan ldquoPhotocatalytic

degradation of cationic azo dye by TiO2bentonite nanocom-

positerdquo Journal of Photochemistry and Photobiology A Chem-istry vol 149 no 1ndash3 pp 169ndash174 2002

[19] X Lu B Zhang Y Wang et al ldquoNano-Ag-loaded hydroxyap-atite coatings on titanium surfaces by electrochemical deposi-tionrdquo Journal of the Royal Society Interface 2011

[20] A D Bokare R C Chikate C V Rode and K M PaknikarldquoIron-nickel bimetallic nanoparticles for reductive degradationof azo dye Orange G in aqueous solutionrdquo Applied Catalysis BEnvironmental vol 79 no 3 pp 270ndash278 2008

[21] I Poulios E Micropoulou R Panou and E KostopoulouldquoPhotooxidation of eosin Y in the presence of semiconductingoxidesrdquo Applied Catalysis B Environmental vol 41 no 4 pp345ndash355 2003

[22] L Ma X Wang B Wang et al ldquoPhotooxidative degrada-tion mechanism of model compounds of poly(p-phenylenev-inylenes) [PPVs]rdquo Chemical Physics vol 285 pp 85ndash94 2002

[23] Y Xiong and H T Karlsson ldquoApproach to a two-step process ofdye wastewater containing acid red Brdquo Journal of EnvironmentalScience and HealthmdashPart A ToxicHazardous Substances andEnvironmental Engineering vol 36 no 3 pp 321ndash331 2001

[24] E L Appleton ldquoA nickel-iron wall against contaminatedgroundwaterrdquo Environmental Science and Technology vol 30no 12 pp 536Andash539A 1996

[25] S S Hassan A R Solangi M H Agheem Y Junejo N HKalwar and Z A Tagar ldquoUltra-fast catalytic reduction of dyesby ionic liquid recoverable and reusablemefenamic acid derivedgold nanoparticlesrdquo Journal ofHazardousMaterials vol 190 no1ndash3 pp 1030ndash1036 2011

[26] L Xu X-C Wu and J-J Zhu ldquoGreen preparation and catalyticapplication of Pd nanoparticlesrdquoNanotechnology vol 19 no 30Article ID 305603 2008

[27] A Nafady H I Afridi S Sara A Shah and A Niaz ldquoDirectsynthesis and stabilization of Bi-sized cysteine-derived goldnanoparticles reduction catalyst for methylene bluerdquo Journal ofthe Iranian Chemical Society vol 8 no 1 pp S34ndashS43 2011

[28] L Ai and J Jiang ldquoCatalytic reduction of 4-nitrophenol by silvernanoparticles stabilized on environmentally benign macro-scopic biopolymer hydrogelrdquo Bioresource Technology vol 132pp 374ndash377 2013

[29] T K Sau A Pal and T Pal ldquoSize regime dependent catalysisby gold nanoparticles for the reduction of eosinrdquo Journal ofPhysical Chemistry B vol 105 no 38 pp 9266ndash9272 2001

[30] T M D Dang T T T Le E Fribourg-Blanc and M CDang ldquoSynthesis and optical properties of copper nanoparticlesprepared by a chemical reductionmethodrdquoAdvances in NaturalSciences Nanoscience and Nanotechnology vol 2 no 1 ArticleID 015009 2011

[31] T M D Dang T T T Le E Fribourg-Blanc and M CDang ldquoThe influence of solvents and surfactants on the prepa-ration of copper nanoparticles by a chemicalreductionmethodrdquoAdvances in Natural Sciences Nanoscience and Nanotechnologyvol 2 no 2 Article ID 025004 2011

[32] C Petit P Lixon and M-P Pileni ldquoIn situ synthesis ofsilver nanocluster in AOT reverse micellesrdquo Journal of PhysicalChemistry vol 97 no 49 pp 12974ndash12983 1993

[33] X Cao F Yu L Li Z Yao and Y Xie ldquoCopper nanorodjunctions templated by a novel polymer-surfactant aggregaterdquoJournal of Crystal Growth vol 254 no 1-2 pp 164ndash168 2003

[34] B K Park S Jeong D Kim JMoon S Lim and J S Kim ldquoSyn-thesis and size control ofmonodisperse copper nanoparticles bypolyol methodrdquo Journal of Colloid and Interface Science vol 311no 2 pp 417ndash424 2007

[35] Y Badr and M A Mahmoud ldquoPhotocatalytic degradationof methyl orange by gold silver nano-coresilica nano-shellrdquoJournal of Physics and Chemistry of Solids vol 68 no 3 pp 413ndash419 2007

[36] C Chen J Liu P Liu and B Yu ldquoInvestigation of photocat-alytic degradation of methyl orange by using nano-sized ZnOcatalystsrdquo Advances in Chemical Engineering and Science vol 1no 1 pp 9ndash14 2011

[37] T Shahwan S Abu Sirriah M Nairat et al ldquoGreen synthesisof iron nanoparticles and their application as a Fenton-likecatalyst for the degradation of aqueous cationic and anionicdyesrdquoChemical Engineering Journal vol 172 no 1 pp 258ndash2662011

[38] Y He J F Gao F Q Feng C Liu Y Z Peng and S Y WangldquoThe comparative study on the rapid decolorization of azoanthraquinone and triphenylmethane dyes by zero-valent ironrdquoChemical Engineering Journal vol 179 pp 8ndash18 2012

[39] Z Zainal C Y Lee M Z Hussein A Kassim and N A YusofldquoElectrochemical-assisted photodegradation of dye on TiO

2

thin films investigation on the effect of operational parametersrdquoJournal of Hazardous Materials vol 118 no 1ndash3 pp 197ndash2032005

[40] A Umer S Naveed N Ramzan and M S Rafique ldquoSelectionof a suitable method for the synthesis of copper nanoparticlesrdquoNano vol 7 no 5 Article ID 1230005 2012

[41] R A Soomro S T H Sherazi Sirajuddin et al ldquoSynthesis of airstable copper nanoparticles and their use in catalysisrdquoAdvancedMaterials Letters vol 5 no 4 pp 191ndash198 2014

[42] F Chen N Alemu and R L Johnston ldquoCollective plasmonmodes in a compositionally asymmetric nanoparticle dimerrdquoAIP Advances vol 1 no 3 Article ID 032134 2011

[43] T GhodselahiM A Vesaghi andA Shafiekhani ldquoStudy of sur-face plasmon resonance of CuCu

2O core-shell nanoparticles

byMie theoryrdquo Journal of Physics D Applied Physics vol 42 no1 Article ID 015308 2009

[44] CNoguez ldquoSurface plasmons onmetal nanoparticles the influ-ence of shape and physical environmentrdquo Journal of PhysicalChemistry C vol 111 no 10 pp 3606ndash3619 2007

[45] S K Ghosh and T Pal ldquoInterparticle coupling effect on thesurface plasmon resonance of gold nanoparticles from theoryto applicationsrdquo Chemical Reviews vol 107 no 11 pp 4797ndash4862 2007

[46] S De and S Mandal ldquoSurfactant-assisted shape control of cop-per nanostructuresrdquo Colloids and Surfaces A Physicochemicaland Engineering Aspects vol 421 pp 72ndash83 2013

[47] M Vaseem K M Lee D Y Kim and Y-B Hahn ldquoParametricstudy of cost-effective synthesis of crystalline copper nanopar-ticles and their crystallographic characterizationrdquo MaterialsChemistry and Physics vol 125 no 3 pp 334ndash341 2011

[48] V Sharma K Park and M Srinivasarao ldquoColloidal dispersionof gold nanorods historical background optical propertiesseed-mediated synthesis shape separation and self-assemblyrdquoMaterials Science and Engineering R Reports vol 65 no 1ndash3pp 1ndash38 2009

12 Journal of Nanomaterials

[49] J A Eastman L J Thompson and B J Kestel ldquoNarrowingof the palladium-hydrogen miscibility gap in nanocrystallinepalladiumrdquo Physical Review B vol 48 no 1 pp 84ndash92 1993

[50] T R Yang H E Horng H C Yang L J Jang W N Kangand S S Yom ldquoInfrared properties of single crystal MgAl

2O4 a

substrate for high-temperature superconducting filmsrdquo PhysicaC Superconductivity vol 235ndash240 no 2 pp 1445ndash1446 1994

[51] S R Taffarel and J Rubio ldquoAdsorption of sodium dodecylbenzene sulfonate from aqueous solution using a modifiednatural zeolite with CTABrdquo Minerals Engineering vol 23 no10 pp 771ndash779 2010

[52] M S Usman N A Ibrahim K Shameli N Zainuddin andW M Z W Yunus ldquoCopper nanoparticles mediated by chi-tosan synthesis and characterization via chemical methodsrdquoMolecules vol 17 no 12 pp 14928ndash14936 2012

[53] K Tian C Liu H Yang and X Ren ldquoIn situ synthesis of coppernanoparticlespolystyrene compositerdquo Colloids and Surfaces APhysicochemical and Engineering Aspects vol 397 pp 12ndash152012

[54] Z M Sui X Chen L Y Wang et al ldquoCapping effect of CTABon positively chargedAg nanoparticlesrdquo Physica E Low-Dimen-sional Systems and Nanostructures vol 33 no 2 pp 308ndash3142006

[55] X Gu T Nguyen M Oudina et al ldquoMicrostructure andmorphology of amine-cured epoxy coatings before and afteroutdoor exposuresmdashan AFM studyrdquo Journal of Coatings Tech-nology Research vol 2 no 7 pp 547ndash556 2005

[56] A Chaudhari C-C S Yan and S-L Lee ldquoAutopoisoningreactions over rough surface a multifractal scaling analysisrdquoInternational Journal of Chemical Kinetics vol 37 no 3 pp 175ndash182 2005

[57] S-L Lee and C-K Lee ldquoHeterogeneous reactions over fractalsurfaces amultifractal scaling analysisrdquo International Journal ofQuantum Chemistry vol 64 no 3 pp 337ndash350 1997

[58] P Chokratanasombat and E Nisaratanaporn ldquoPreparation ofultrafine copper powders with controllable size via polyolprocess with sodium hydroxide additionrdquo Engineering Journalvol 16 no 4 pp 39ndash46 2012

[59] M Kooti and L Matouri ldquoFabrication of nanosized cuprousoxide using fehlingrsquos solutionrdquo Scientia Iranica vol 17 no 1 pp73ndash78 2010

[60] M A Watzky and R G Finke ldquoTransition metal nanoclusterformation kinetic and mechanistic studies A new mechanismwhen hydrogen is the reductant slow continuous nucleationand fast autocatalytic surface growthrdquo Journal of the AmericanChemical Society vol 119 no 43 pp 10382ndash10400 1997

[61] J Hu T W Odom and C M Lieber ldquoChemistry and physicsin one dimension synthesis and properties of nanowires andnanotubesrdquo Accounts of Chemical Research vol 32 no 5 pp435ndash445 1999

[62] A Houas H Lachheb M Ksibi E Elaloui C Guillardand J-M Herrmann ldquoPhotocatalytic degradation pathway ofmethylene blue in waterrdquo Applied Catalysis B Environmentalvol 31 no 2 pp 145ndash157 2001

[63] K M Bratlie H Lee K Komvopoulos P Yang and G ASomorjai ldquoPlatinum nanoparticle shape effects on benzenehydrogenation selectivityrdquoNano Letters vol 7 no 10 pp 3097ndash3101 2007

[64] R B Greegor and F W Lytle ldquoMorphology of supported metalclusters determination by EXAFS and chemisorptionrdquo Journalof Catalysis vol 63 no 2 pp 476ndash486 1980

[65] S Ladas ldquoThe effect of metal particle size on the stoichiometryof adsorptionrdquo Surface Science vol 175 no 1 pp L681ndashL6861986

[66] R van Hardeveld and F Hartog ldquoThe statistics of surface atomsand surface sites on metal crystalsrdquo Surface Science vol 15 no2 pp 189ndash230 1969

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