Research ArticleSynthesis and Ultraviolet Visible SpectroscopyStudies of Chitosan Capped Gold Nanoparticlesand Their Reactions with Analytes

Norfazila Mohd Sultan and Mohd Rafie Johan

Nanomaterials Engineering Research Group Advanced Materials Research Laboratory Department of Mechanical EngineeringUniversity of Malaya 50603 Lembah Pantai Kuala Lumpur Malaysia

Correspondence should be addressed to Mohd Rafie Johan mrafiejumedumy

Received 29 April 2014 Revised 10 July 2014 Accepted 16 July 2014 Published 19 August 2014

Academic Editor Degang Fu

Copyright copy 2014 N Mohd Sultan and M R Johan This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Gold nanoparticles (AuNPs) had been synthesized with various molarities and weights of reducing agent monosodium glutamate(MSG) and stabilizer chitosan respectively The significance of chitosan as stabilizer was distinguished through transmissionelectron microscopy (TEM) images and UV-Vis absorption spectra in which the interparticles distance increases whilst retainingthe surface plasmon resonance (SPR) characteristics peak The most stable AuNPs occurred for composition with the lowest (1 g)weight of chitosan AuNPs capped with chitosan size stayed small after 1 month aging compared to bare AuNPs The ability ofchitosan capped AuNPs to uptake analyte was studied by employing amorphous carbon nanotubes (120572-CNT) copper oxide (Cu

2O)

and zinc sulphate (ZnSO4) as the target material The absorption spectra showed dramatic intensity increased and red shifted once

the analyte was added to the chitosan capped AuNPs

1 Introduction

Gold nanoparticles (AuNPs) have glowing prospects inmanyapplications due to their distinctive optical electronic andelectrical properties [1] AuNPs display intense colours wheninduced by incident light field These were contributed bycollective electron oscillation that gives intensification to thesurface plasmon resonance (SPR) absorption

There are various techniques to produce AuNPs suchas microemulsion reversed micelles seeding growth sono-chemistry photochemistry radiolysis and direct chemicalreduction [2ndash4] The most simple economical and powerfulsynthesis is the direct chemical reductionmethod In the caseofAuNPs chemical reduction routes generate zerovalent goldcolloids from gold precursors [5]

The invention of zerovalent gold colloids was pioneeredby Turkevich et al [6] and later refined by Frens [7] in whichthe ratio of gold precursors to citrate was varied Brust-Schiffin [8] commenced the synthesis of AuNPs in organicsolventswhich involves a phase transfer agent such as toluene

The above conventional methods had many shortcomingswhich contributed to explorations of other reducing agentsand alternative routes The synthesis of AuNPs throughTurkevich et al approaches takes a longer time (1 hr) for goldsalt reduction While the use of organic solvents in Brust-Schiffinmethod leaves them inapt for detecting biomoleculesand biological surfaces like proteins and saccharides [9]various chemicals had been exploited as reducing agent toproduce zerovalent gold colloids such as amino acid deriva-tives like lysine and valine but without success Howeverother acidic amino acid derivatives such as aspartic acid[10] and monosodium glutamate (MSG) [11] are competentin reducing gold salt (Figure 1) Sugunan and Dutta [11]produced AuNPs by emphasizing on lower molar ratio ofMSG

AuNPs have compelling tendency to flocculate due totheir van der walls forces However the agglomeration canbe hindered by introducing a repulsive force between theparticles In this light the use of stabilizer as a repulsiveforce came into the pictureThe use of chitosan as a stabilizer

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 184604 7 pageshttpdxdoiorg1011552014184604

2 The Scientific World Journal

Cl

Cl

Cl

HO

O

O

HOH

HO

O

O

H

O

O

H

HO

O

HO

HO

H

OH

HO

HO

HO

OO

O

n

HO

HO

HO

OO

O

n

Adsorb

3

HO

O

O

HOH

NH2

+998400

NH2

+998400

NH2

+998400

Au3+

Au3+

Au3+

H2N+998400

H2N+998400

H2N+998400

H2N+998400

Ominus

Ominus

Ominus

minus

minus3Clminus+

+

+ NH2

NH2

NH2

NH2

Na+

OH

OH

OH

OH

OH

OH

OH

OH

OH

OH

OH

Figure 1 Schematic diagram of gold precursor reduction by MSG and capping the gold particle surfaces with chitosan

was reported elsewhere [12] Chitosan contributed the sterichindrance to stabilize the nanoparticles as shown in Figure 1The amino group presence in its polycationic structureactivates steric hindrance thus ensuring strong stability overlong durations [12] Formost biological applications chitosanpossesses many attractive functional groups such as biotin[13] aptamers [14 15] concanavalin (con-A) [16] and bovineserum albumin [17 18] However proteins have a downsideas they are expensive although theywerewidely exploited andoffer excellent characteristics Remarkably chitosan possessessimilar ability as proteins and manipulations of its propertieshave not been fully extended for numerous applicationsChitosan is accessible for cross-linking through its boundlessamino group and its cationic features allowing the ionic cross-linking to take place with multivalent elements The mostpromising features of chitosan are its solubility in aqueous

acidic solutions [19] The description of chitosan agrees withthe aims of the research to manufacture a readily biocompat-ible and nontoxic chitosan capped gold nanoparticles

Sugunan et al [9] had employed chitosan as stabilizerfor silver nanoparticles for heavy metal ion sensor yetthe thermodynamically proficiency of chitosan had notbeen investigated Moreover the performance of chitosanadsorption on the surface of AuNPs has not been studiedIn this paper we report the synthesis of AuNPs and itsstabilization mechanism using chitosan By exploiting thechemistry of amine and chitosan we have shown that theAuNPs can be prepared in water by complexation of highmolar ratio glutamic acid molecules with gold precursorsstabilized by the adsorption of chitosan on the surface ofAuNPs Preparation of AuNPs capped with chitosan wascarried out in a single-pot process and the resulting particles

The Scientific World Journal 3

were thoroughly characterized The stability of chitosan wasfurthered studied and discussed

2 Experimental Section

21 Materials Gold (III) chloride (AuCl3) acetic acid and

monosodium glutamate (MSG) (99 Na salt of L-glutamicacid) were purchased from Acros Organics Meanwhile chi-tosan (industrial grade) was purchased from Easter HoldingCo Ltd with deacetylation degree of 80 All chemicals wereused without further purifications and all the solutions wereprepared with distilled water

22 Preparation of AuNPs 2mL of 5mM AuCl3solution

(01517 g in 100mL water) was stirred and heated to 100∘CThen 3mL of 50mM Na salt of L-glutamic acid solution(MSG) (09357 g in 100mL water) is quickly poured into thegold solution The solution was stirred continuously untilthe colour changed from pale red to intense red The stepswere repeated with 100 150 200 250 and 300mM of MSGAnother set of samples was prepared for observing the agingbehaviour of the AuNPs The samples were left in ambiencetemperature for a month

23 Preparation of Chitosan Capped AuNPs The chitosansolution was prepared by mixing the said amount of blendedchitosan powder as purchased with distilled water andadequate amount of acetic acid The solution was stirred atroom temperature until the chitosan powder had completelydissolved in the water 990 120583L of chitosan solution (1 g ofchitosan in mixture of 100mL water and 150 120583L acetic acid)was then added to the as-synthesized 50mMofMSG reducedAuNPs A visible change of colour occurred immediatelyTheheating was discontinued to allow the solution to reach theambient temperature The steps were repeated with differentconcentrations of MSG (100 150 200 250 and 300mM)Another set of samples was prepared for observing the agingbehaviour of the chitosan capped AuNPs The samples wereleft in ambience temperature for a month

24 Preparation of Amorphous Carbon Nanotubes (120572-CNTs)ChitosanCappedAuNPs Thesynthesis procedure of120572-CNTsis followed by Tan et al [20] The procedure was instigatedwith mixture of 8mL of ethyl alcohol (90) 42 g of NaBH

4

(9999) and 15mL of 1M NaOH in a 25mL flask Thesolution was further stirred for the next 45 minutes beforebeing transferred to a Parr reactor with capacity of 200mLThe reactor was heated inside a furnace up to 200∘C andheld for 2 hours under scaled conditionThe Parr reactor wasallowed to cool to ambient temperature and the precipitatewaswashed thoroughlywith alcohol and deionisedwaterTheprecipitate was then dried in the vacuum oven 120572-CNTs wereadded to the optimum condition of chitosan capped AuNPssolution (1 g of chitosan powder and 100mM of MSG)

25 Preparation of Copper Oxide-Chitosan Capped AuNPs0005 001 005 01 and 05 g of purchased copper oxidepowderwere added to optimumcondition of chitosan capped

Figure 2 TEM image of AuNPs reduced with 100mM of MSG

Figure 3 TEM image of AuNPs reduced with 200mM of MSG

AuNPs solution (1 g of chitosan powder and 100mM ofMSG)

26 Preparation of Zinc Sulphate-Chitosan Capped AuNPs0005 001 005 01 and 05 g of purchased zinc sulphatepowderwere added to optimumcondition of chitosan cappedAuNPs solution (1 g of chitosan powder and 100mM ofMSG)

27 Characterizations of AuNPs Transmission electronmicroscope (Libra 120 TEM using accelerating voltageof 400 kV) was employed to assess the particles size anddistribution of the particles The optical properties of golddispersions were investigated by UV-Vis spectrophotometerusing UVIKON 923 UV-Vis spectrophotometer

3 Results and Discussion

31 TEM Analysis Figures 2 3 and 4 show the TEM imagesfor AuNPs prepared at different concentrations of MSG Theparticles are nearly spherical with high dispersibility Theaverage size of particles for 100 200 and 300mMMSG is 1815 and 9 nm respectively It is clearly shown that high molarof MSG produces smaller particle size

The role of chitosan in stericmechanism has been verifiedby the TEM image shown in Figure 5 The chitosan whichresembles a spider web infused a repelling force between theAuNPs separating them apart unlike the bare AuNPs (Figures2ndash4) The average interparticles distance increases to 96 nmdue to wrapping of chitosan around the AuNPs

4 The Scientific World Journal

Figure 4 TEM image of AuNPs reduced with 300mM of MSG

Figure 5 TEM image of chitosan capped AuNPs

32 UV-Vis Spectroscopy Analysis

321 Effect of Concentration of Reducing Agent MSGFigure 6 shows the absorption spectra of AuNPs at variousconcentrations of MSG The surface plasmon resonance(SPR) peaks are shifted to the smaller wavelengths indicatingthe reduction in particle sizes This result is in good agree-ment with the TEM images in Figures 2ndash4 The symmetricalshape of the absorp-tion spectra indicates that sample has anarrow particle size distribution

322 Effect of Chitosan as Stabilizer Figure 7 shows theabsorption spectra of bare and increased weight of chitosancapped AuNPs at the optimum concentration of reducingagent MSG (100mM) The absorbance of chitosan cappedAuNPs is higher than bare AuNPsThe SPR peak is shifted tothe longer wavelength for chitosan capped AuNPs This redshifted trend is continued for samples with increasing weightof chitosan The absorbance for chitosan capped AuNPs isslightly increased with the increase of chitosan weight Theattachment of chitosan on the surface of AuNPs affected theiroptical properties

323 Effect of Aging Figure 8 shows the absorption spectraof AuNPs with various concentrations of MSG after 1 monthaging time The SPR peaks are shifted to longer wavelengthcompared to their counterparts in Figure 6 The same goesfor their FWHM values which show more broadened peakafter 1 month ageing time This indicates that the AuNPs sizeand their particle size distribution are increased after aging

12

1

08

06

04

02

0

400 500 600 700

Nor

mal

ized

abso

rban

ce

Wavelength (nm)

a

b

c

d

e

Figure 6 Absorption spectra of AuNPswith various concentrationsof reducing agent MSG (a) 100mM (b) 150mM (c) 200mM (d)250mM (e) 300mM

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) Without chitosan(b) 1g chitosan(c) 2g chitosan

(d) 3g chitosan(e) 4g chitosan(f) 5g chitosan

Figure 7 Absorption spectra of bare and increased weight ofchitosan capped AuNPs at the optimum concentration of reducingagent MSG (a) 0 g chitosan (b) 1 g chitosan (c) 2 g chitosan (d) 3 gchitosan (e) 4 g chitosan (f) 5 g chitosan

Figure 9 shows the absorption spectra of bare and chi-tosan capped AuNPs for various concentrations of MSGafter 1 month ageing time The SPR peaks are shifted to thesmaller wavelength compared to the bare AuNPs (Figure 8)The same goes for their FWHM values which are smallerthan the FWHM values of the bare AuNPs These absorptionspectra have highlighted the role of chitosan adsorption onthe AuNPs surfaces in which their particle size stays smalleven after 1 month aging time Chitosan preserves stability

The Scientific World Journal 5

Table 1 Experimental values of SPR peaks for bare and chitosan capped AuNPs with full width half maximum (FWHM) after 1 month ageingtime

Sample SPR 120582max (nm) FHWM (nm)Concentration of MSG (mM) AuNPs Chitosan capped AuNPs AuNPs Chitosan capped AuNPs100 532 531 51 60150 544 537 72 52200 554 539 52 51250 544 527 96 46300 534 526 70 57

0

02

04

06

08

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 8 Absorption spectra of AuNPs with various concentrationsof reducing agent MSG after 1 month aging time (a) 100mM (b)150mM (c) 200mM (d) 250mM (e) 300mM

0

02

04

06

08

1

400 450 500 550 600 650 700Wavelength (nm)

minus02

Abso

rban

ce

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 9 Absorption spectra of chitosan capped AuNPs withvarious concentrations of reducing agent MSG after 1 month agingtime (a) 100mM (b) 150mM (c) 200mM (d) 250mM (e)300mM

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

(a) 0001(b) 0005(c) 005

Figure 10 Absorption spectra of chitosan capped AuNPs mixedwith different weights of 120572-CNTs (a) 0001 g (b) 0005 g (c) 005 g

and hinders agglomeration of AuNPsThe FWHM and otherexperimental results are listed in Table 1

324 Effect of Amorphous Carbon Nanotube (120572-CNTs)sOxides and Sulphate to Chitosan Capped AuNPs Figure 10shows the SPR peaks of chitosan capped AuNPs adjournedat 549 nm for three different weights of 120572-CNTs The SPRpeak intensity rises as the weight of 120572-CNTs increases Thisphenomenon can be explained with regard to the fact thatAuNPs are very sensitive in the weight change of 120572-CNTsupon exposure High surface ratios of AuNPs contribute tothe sensitivities and make them more reactive and able touptake the analyte

Figure 11 shows the absorption spectra of chitosan cappedAuNPsmixedwith different weights of copper oxideThe SPRpeaks are shifted from 521 to 577 nm as the weight of copperoxide increases This clearly shows the complexation ofchitosan cappedAuNPs towards the addition of copper oxideThe enlargement of the particles uptake can be underlined asthe peak intensity also shows dramatic increase as the weightof copper oxide increases

Figure 12 shows the absorption spectra of chitosan cappedAuNPs at different weights of zinc sulphate The spectra alsosuccessfully show analyte particles entrapment by chitosan

6 The Scientific World Journal

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

001(b) 0005(a) 005(c)

01(d)

Figure 11 Absorption spectra of chitosan capped AuNPs mixedwith different weights of copper oxide (a) 0005 g (b) 001 g (c)005 g (d) 01 g

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) 001(b) 005

Figure 12 Absorption spectra of chitosan capped AuNPs mixed atdifferent weights of zinc sulphate (a) 001 g (b) 005 g

capped AuNPsThe SPR peaks intensities are increased as theweight of zinc sulphate added to the chitosan capped AuNPsincreases

4 Conclusion

We have successfully synthesized chitosan capped AuNPs viachemical reduction technique We have also revealed thatAuNPs revolutionize their dimension and optical behaviourthrough variation of parameters such as concentration ofreducing agent weight of stabilizer and aging time Chitosanconcentration plays an important role in imparting extrahindrance strengthThe particles stability was contributed bychitosan even after 1 month of aging The chitosan capped

AuNPs were able to uptake analyte such as 120572-CNTs copperoxide and zinc sulphate

Conflict of Interests

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

Acknowledgments

The authors would like to express their greatest gratitude tothe Ministry of Higher Education of Malaysia and Universityof Malaya for funding through UMMOHE-HIR ResearchGrant (UMCHIRMOHEENG12) Special thanks are dueto Mr Low Chien Chong for providing the TEM images

References

[1] D A HandleyColloidal Gold Principles Methods and Applica-tions Academic Press New York NY USA 1989 edited by MA Hayat

[2] C Roos M Schmidt J Ebenhoch F Baumann B Deubzerand J Weis ldquoDesign and synthesis of molecular reactors for thepreparation of topologically trapped gold clustersrdquo AdvancedMaterials vol 11 no 9 pp 761ndash766 1999

[3] R G Freeman M B Hommer K C Grabar M A Jacksonand M J Natan ldquoAg-clad Au nanoparticles novel aggregationoptical and surface-enhanced Raman scattering propertiesrdquoJournal of Physical Chemistry vol 100 no 2 pp 718ndash724 1998

[4] L Cao P Diao L Tong T Zhu and Z Liu ldquoSurface-enhanced Raman scattering of p-aminothiophenol on aAu(core)Cu(shell) nanoparticle assemblyrdquo ChemPhysChemvol 6 no 5 pp 913ndash918 2005

[5] N Toshima and T Yonezawa ldquoBimetallic nanoparticles novelmaterials for chemical and physical applicationsrdquo New Journalof Chemistry vol 22 no 11 pp 1179ndash1201 1998

[6] J Turkevich P C Stevenson and J Hillier ldquoA study of thenucleation and growth processes in the synthesis of colloidalgoldrdquo Discussions of the Faraday Society vol 11 pp 55ndash75 1951

[7] J Frens ldquoControlled nucleation for the regulation of the particlesize inmonodisperse gold suspensionsrdquoNature Physical Sciencevol 241 pp 20ndash22 1973

[8] M-C Daniel and D Astruc ldquoGold nanoparticles assemblysupramolecular chemistry quantum-size-related propertiesand applications toward biology catalysis and nanotechnol-ogyrdquo Chemical Reviews vol 104 no 1 pp 293ndash346 2004

[9] A Sugunan C Thanachayanont J Dutta and J G HilbornldquoHeavy-metal ion sensors using chitosan-capped gold nanopar-ticlesrdquo Science and Technology of Advanced Materials vol 6 no3-4 pp 335ndash340 2005

[10] S Mandal P R Selvakannan S Phadtare R Pasricha and MSastry ldquoSynthesis of a stable gold hydrosol by the reduction ofchloroaurate ions by the amino acid aspartic acidrdquo Journal ofChemical Sciences vol 114 no 5 pp 513ndash520 2002

[11] A Sugunan and J Dutta ldquoNovel synthesis of gold nanoparticlesin aqueous mediardquo in Proceedings of the Material ResearchSociety Fall Conference MRS Boston Mass USA 1999

[12] H C Warad S C Ghosh C Thanachayanont and J DuttaldquoHighly luminescent manganese doped ZnS quantum dots forbiological labelingrdquo in Proceedings of International Conference

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012

The Scientific World Journal 3

were thoroughly characterized The stability of chitosan wasfurthered studied and discussed

2 Experimental Section

21 Materials Gold (III) chloride (AuCl3) acetic acid and

monosodium glutamate (MSG) (99 Na salt of L-glutamicacid) were purchased from Acros Organics Meanwhile chi-tosan (industrial grade) was purchased from Easter HoldingCo Ltd with deacetylation degree of 80 All chemicals wereused without further purifications and all the solutions wereprepared with distilled water

22 Preparation of AuNPs 2mL of 5mM AuCl3solution

(01517 g in 100mL water) was stirred and heated to 100∘CThen 3mL of 50mM Na salt of L-glutamic acid solution(MSG) (09357 g in 100mL water) is quickly poured into thegold solution The solution was stirred continuously untilthe colour changed from pale red to intense red The stepswere repeated with 100 150 200 250 and 300mM of MSGAnother set of samples was prepared for observing the agingbehaviour of the AuNPs The samples were left in ambiencetemperature for a month

23 Preparation of Chitosan Capped AuNPs The chitosansolution was prepared by mixing the said amount of blendedchitosan powder as purchased with distilled water andadequate amount of acetic acid The solution was stirred atroom temperature until the chitosan powder had completelydissolved in the water 990 120583L of chitosan solution (1 g ofchitosan in mixture of 100mL water and 150 120583L acetic acid)was then added to the as-synthesized 50mMofMSG reducedAuNPs A visible change of colour occurred immediatelyTheheating was discontinued to allow the solution to reach theambient temperature The steps were repeated with differentconcentrations of MSG (100 150 200 250 and 300mM)Another set of samples was prepared for observing the agingbehaviour of the chitosan capped AuNPs The samples wereleft in ambience temperature for a month

24 Preparation of Amorphous Carbon Nanotubes (120572-CNTs)ChitosanCappedAuNPs Thesynthesis procedure of120572-CNTsis followed by Tan et al [20] The procedure was instigatedwith mixture of 8mL of ethyl alcohol (90) 42 g of NaBH

4

(9999) and 15mL of 1M NaOH in a 25mL flask Thesolution was further stirred for the next 45 minutes beforebeing transferred to a Parr reactor with capacity of 200mLThe reactor was heated inside a furnace up to 200∘C andheld for 2 hours under scaled conditionThe Parr reactor wasallowed to cool to ambient temperature and the precipitatewaswashed thoroughlywith alcohol and deionisedwaterTheprecipitate was then dried in the vacuum oven 120572-CNTs wereadded to the optimum condition of chitosan capped AuNPssolution (1 g of chitosan powder and 100mM of MSG)

25 Preparation of Copper Oxide-Chitosan Capped AuNPs0005 001 005 01 and 05 g of purchased copper oxidepowderwere added to optimumcondition of chitosan capped

Figure 2 TEM image of AuNPs reduced with 100mM of MSG

Figure 3 TEM image of AuNPs reduced with 200mM of MSG

AuNPs solution (1 g of chitosan powder and 100mM ofMSG)

26 Preparation of Zinc Sulphate-Chitosan Capped AuNPs0005 001 005 01 and 05 g of purchased zinc sulphatepowderwere added to optimumcondition of chitosan cappedAuNPs solution (1 g of chitosan powder and 100mM ofMSG)

27 Characterizations of AuNPs Transmission electronmicroscope (Libra 120 TEM using accelerating voltageof 400 kV) was employed to assess the particles size anddistribution of the particles The optical properties of golddispersions were investigated by UV-Vis spectrophotometerusing UVIKON 923 UV-Vis spectrophotometer

3 Results and Discussion

31 TEM Analysis Figures 2 3 and 4 show the TEM imagesfor AuNPs prepared at different concentrations of MSG Theparticles are nearly spherical with high dispersibility Theaverage size of particles for 100 200 and 300mMMSG is 1815 and 9 nm respectively It is clearly shown that high molarof MSG produces smaller particle size

The role of chitosan in stericmechanism has been verifiedby the TEM image shown in Figure 5 The chitosan whichresembles a spider web infused a repelling force between theAuNPs separating them apart unlike the bare AuNPs (Figures2ndash4) The average interparticles distance increases to 96 nmdue to wrapping of chitosan around the AuNPs

4 The Scientific World Journal

Figure 4 TEM image of AuNPs reduced with 300mM of MSG

Figure 5 TEM image of chitosan capped AuNPs

32 UV-Vis Spectroscopy Analysis

321 Effect of Concentration of Reducing Agent MSGFigure 6 shows the absorption spectra of AuNPs at variousconcentrations of MSG The surface plasmon resonance(SPR) peaks are shifted to the smaller wavelengths indicatingthe reduction in particle sizes This result is in good agree-ment with the TEM images in Figures 2ndash4 The symmetricalshape of the absorp-tion spectra indicates that sample has anarrow particle size distribution

322 Effect of Chitosan as Stabilizer Figure 7 shows theabsorption spectra of bare and increased weight of chitosancapped AuNPs at the optimum concentration of reducingagent MSG (100mM) The absorbance of chitosan cappedAuNPs is higher than bare AuNPsThe SPR peak is shifted tothe longer wavelength for chitosan capped AuNPs This redshifted trend is continued for samples with increasing weightof chitosan The absorbance for chitosan capped AuNPs isslightly increased with the increase of chitosan weight Theattachment of chitosan on the surface of AuNPs affected theiroptical properties

323 Effect of Aging Figure 8 shows the absorption spectraof AuNPs with various concentrations of MSG after 1 monthaging time The SPR peaks are shifted to longer wavelengthcompared to their counterparts in Figure 6 The same goesfor their FWHM values which show more broadened peakafter 1 month ageing time This indicates that the AuNPs sizeand their particle size distribution are increased after aging

12

1

08

06

04

02

0

400 500 600 700

Nor

mal

ized

abso

rban

ce

Wavelength (nm)

a

b

c

d

e

Figure 6 Absorption spectra of AuNPswith various concentrationsof reducing agent MSG (a) 100mM (b) 150mM (c) 200mM (d)250mM (e) 300mM

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) Without chitosan(b) 1g chitosan(c) 2g chitosan

(d) 3g chitosan(e) 4g chitosan(f) 5g chitosan

Figure 7 Absorption spectra of bare and increased weight ofchitosan capped AuNPs at the optimum concentration of reducingagent MSG (a) 0 g chitosan (b) 1 g chitosan (c) 2 g chitosan (d) 3 gchitosan (e) 4 g chitosan (f) 5 g chitosan

Figure 9 shows the absorption spectra of bare and chi-tosan capped AuNPs for various concentrations of MSGafter 1 month ageing time The SPR peaks are shifted to thesmaller wavelength compared to the bare AuNPs (Figure 8)The same goes for their FWHM values which are smallerthan the FWHM values of the bare AuNPs These absorptionspectra have highlighted the role of chitosan adsorption onthe AuNPs surfaces in which their particle size stays smalleven after 1 month aging time Chitosan preserves stability

The Scientific World Journal 5

Table 1 Experimental values of SPR peaks for bare and chitosan capped AuNPs with full width half maximum (FWHM) after 1 month ageingtime

Sample SPR 120582max (nm) FHWM (nm)Concentration of MSG (mM) AuNPs Chitosan capped AuNPs AuNPs Chitosan capped AuNPs100 532 531 51 60150 544 537 72 52200 554 539 52 51250 544 527 96 46300 534 526 70 57

0

02

04

06

08

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 8 Absorption spectra of AuNPs with various concentrationsof reducing agent MSG after 1 month aging time (a) 100mM (b)150mM (c) 200mM (d) 250mM (e) 300mM

0

02

04

06

08

1

400 450 500 550 600 650 700Wavelength (nm)

minus02

Abso

rban

ce

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 9 Absorption spectra of chitosan capped AuNPs withvarious concentrations of reducing agent MSG after 1 month agingtime (a) 100mM (b) 150mM (c) 200mM (d) 250mM (e)300mM

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

(a) 0001(b) 0005(c) 005

Figure 10 Absorption spectra of chitosan capped AuNPs mixedwith different weights of 120572-CNTs (a) 0001 g (b) 0005 g (c) 005 g

and hinders agglomeration of AuNPsThe FWHM and otherexperimental results are listed in Table 1

324 Effect of Amorphous Carbon Nanotube (120572-CNTs)sOxides and Sulphate to Chitosan Capped AuNPs Figure 10shows the SPR peaks of chitosan capped AuNPs adjournedat 549 nm for three different weights of 120572-CNTs The SPRpeak intensity rises as the weight of 120572-CNTs increases Thisphenomenon can be explained with regard to the fact thatAuNPs are very sensitive in the weight change of 120572-CNTsupon exposure High surface ratios of AuNPs contribute tothe sensitivities and make them more reactive and able touptake the analyte

Figure 11 shows the absorption spectra of chitosan cappedAuNPsmixedwith different weights of copper oxideThe SPRpeaks are shifted from 521 to 577 nm as the weight of copperoxide increases This clearly shows the complexation ofchitosan cappedAuNPs towards the addition of copper oxideThe enlargement of the particles uptake can be underlined asthe peak intensity also shows dramatic increase as the weightof copper oxide increases

Figure 12 shows the absorption spectra of chitosan cappedAuNPs at different weights of zinc sulphate The spectra alsosuccessfully show analyte particles entrapment by chitosan

6 The Scientific World Journal

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

001(b) 0005(a) 005(c)

01(d)

Figure 11 Absorption spectra of chitosan capped AuNPs mixedwith different weights of copper oxide (a) 0005 g (b) 001 g (c)005 g (d) 01 g

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) 001(b) 005

Figure 12 Absorption spectra of chitosan capped AuNPs mixed atdifferent weights of zinc sulphate (a) 001 g (b) 005 g

capped AuNPsThe SPR peaks intensities are increased as theweight of zinc sulphate added to the chitosan capped AuNPsincreases

4 Conclusion

We have successfully synthesized chitosan capped AuNPs viachemical reduction technique We have also revealed thatAuNPs revolutionize their dimension and optical behaviourthrough variation of parameters such as concentration ofreducing agent weight of stabilizer and aging time Chitosanconcentration plays an important role in imparting extrahindrance strengthThe particles stability was contributed bychitosan even after 1 month of aging The chitosan capped

AuNPs were able to uptake analyte such as 120572-CNTs copperoxide and zinc sulphate

Conflict of Interests

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

Acknowledgments

The authors would like to express their greatest gratitude tothe Ministry of Higher Education of Malaysia and Universityof Malaya for funding through UMMOHE-HIR ResearchGrant (UMCHIRMOHEENG12) Special thanks are dueto Mr Low Chien Chong for providing the TEM images

References

[1] D A HandleyColloidal Gold Principles Methods and Applica-tions Academic Press New York NY USA 1989 edited by MA Hayat

[2] C Roos M Schmidt J Ebenhoch F Baumann B Deubzerand J Weis ldquoDesign and synthesis of molecular reactors for thepreparation of topologically trapped gold clustersrdquo AdvancedMaterials vol 11 no 9 pp 761ndash766 1999

[3] R G Freeman M B Hommer K C Grabar M A Jacksonand M J Natan ldquoAg-clad Au nanoparticles novel aggregationoptical and surface-enhanced Raman scattering propertiesrdquoJournal of Physical Chemistry vol 100 no 2 pp 718ndash724 1998

[4] L Cao P Diao L Tong T Zhu and Z Liu ldquoSurface-enhanced Raman scattering of p-aminothiophenol on aAu(core)Cu(shell) nanoparticle assemblyrdquo ChemPhysChemvol 6 no 5 pp 913ndash918 2005

[5] N Toshima and T Yonezawa ldquoBimetallic nanoparticles novelmaterials for chemical and physical applicationsrdquo New Journalof Chemistry vol 22 no 11 pp 1179ndash1201 1998

[6] J Turkevich P C Stevenson and J Hillier ldquoA study of thenucleation and growth processes in the synthesis of colloidalgoldrdquo Discussions of the Faraday Society vol 11 pp 55ndash75 1951

[7] J Frens ldquoControlled nucleation for the regulation of the particlesize inmonodisperse gold suspensionsrdquoNature Physical Sciencevol 241 pp 20ndash22 1973

[8] M-C Daniel and D Astruc ldquoGold nanoparticles assemblysupramolecular chemistry quantum-size-related propertiesand applications toward biology catalysis and nanotechnol-ogyrdquo Chemical Reviews vol 104 no 1 pp 293ndash346 2004

[9] A Sugunan C Thanachayanont J Dutta and J G HilbornldquoHeavy-metal ion sensors using chitosan-capped gold nanopar-ticlesrdquo Science and Technology of Advanced Materials vol 6 no3-4 pp 335ndash340 2005

[10] S Mandal P R Selvakannan S Phadtare R Pasricha and MSastry ldquoSynthesis of a stable gold hydrosol by the reduction ofchloroaurate ions by the amino acid aspartic acidrdquo Journal ofChemical Sciences vol 114 no 5 pp 513ndash520 2002

[11] A Sugunan and J Dutta ldquoNovel synthesis of gold nanoparticlesin aqueous mediardquo in Proceedings of the Material ResearchSociety Fall Conference MRS Boston Mass USA 1999

[12] H C Warad S C Ghosh C Thanachayanont and J DuttaldquoHighly luminescent manganese doped ZnS quantum dots forbiological labelingrdquo in Proceedings of International Conference

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012

4 The Scientific World Journal

Figure 4 TEM image of AuNPs reduced with 300mM of MSG

Figure 5 TEM image of chitosan capped AuNPs

32 UV-Vis Spectroscopy Analysis

321 Effect of Concentration of Reducing Agent MSGFigure 6 shows the absorption spectra of AuNPs at variousconcentrations of MSG The surface plasmon resonance(SPR) peaks are shifted to the smaller wavelengths indicatingthe reduction in particle sizes This result is in good agree-ment with the TEM images in Figures 2ndash4 The symmetricalshape of the absorp-tion spectra indicates that sample has anarrow particle size distribution

322 Effect of Chitosan as Stabilizer Figure 7 shows theabsorption spectra of bare and increased weight of chitosancapped AuNPs at the optimum concentration of reducingagent MSG (100mM) The absorbance of chitosan cappedAuNPs is higher than bare AuNPsThe SPR peak is shifted tothe longer wavelength for chitosan capped AuNPs This redshifted trend is continued for samples with increasing weightof chitosan The absorbance for chitosan capped AuNPs isslightly increased with the increase of chitosan weight Theattachment of chitosan on the surface of AuNPs affected theiroptical properties

323 Effect of Aging Figure 8 shows the absorption spectraof AuNPs with various concentrations of MSG after 1 monthaging time The SPR peaks are shifted to longer wavelengthcompared to their counterparts in Figure 6 The same goesfor their FWHM values which show more broadened peakafter 1 month ageing time This indicates that the AuNPs sizeand their particle size distribution are increased after aging

12

1

08

06

04

02

0

400 500 600 700

Nor

mal

ized

abso

rban

ce

Wavelength (nm)

a

b

c

d

e

Figure 6 Absorption spectra of AuNPswith various concentrationsof reducing agent MSG (a) 100mM (b) 150mM (c) 200mM (d)250mM (e) 300mM

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) Without chitosan(b) 1g chitosan(c) 2g chitosan

(d) 3g chitosan(e) 4g chitosan(f) 5g chitosan

Figure 7 Absorption spectra of bare and increased weight ofchitosan capped AuNPs at the optimum concentration of reducingagent MSG (a) 0 g chitosan (b) 1 g chitosan (c) 2 g chitosan (d) 3 gchitosan (e) 4 g chitosan (f) 5 g chitosan

Figure 9 shows the absorption spectra of bare and chi-tosan capped AuNPs for various concentrations of MSGafter 1 month ageing time The SPR peaks are shifted to thesmaller wavelength compared to the bare AuNPs (Figure 8)The same goes for their FWHM values which are smallerthan the FWHM values of the bare AuNPs These absorptionspectra have highlighted the role of chitosan adsorption onthe AuNPs surfaces in which their particle size stays smalleven after 1 month aging time Chitosan preserves stability

The Scientific World Journal 5

Table 1 Experimental values of SPR peaks for bare and chitosan capped AuNPs with full width half maximum (FWHM) after 1 month ageingtime

Sample SPR 120582max (nm) FHWM (nm)Concentration of MSG (mM) AuNPs Chitosan capped AuNPs AuNPs Chitosan capped AuNPs100 532 531 51 60150 544 537 72 52200 554 539 52 51250 544 527 96 46300 534 526 70 57

0

02

04

06

08

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 8 Absorption spectra of AuNPs with various concentrationsof reducing agent MSG after 1 month aging time (a) 100mM (b)150mM (c) 200mM (d) 250mM (e) 300mM

0

02

04

06

08

1

400 450 500 550 600 650 700Wavelength (nm)

minus02

Abso

rban

ce

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 9 Absorption spectra of chitosan capped AuNPs withvarious concentrations of reducing agent MSG after 1 month agingtime (a) 100mM (b) 150mM (c) 200mM (d) 250mM (e)300mM

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

(a) 0001(b) 0005(c) 005

Figure 10 Absorption spectra of chitosan capped AuNPs mixedwith different weights of 120572-CNTs (a) 0001 g (b) 0005 g (c) 005 g

and hinders agglomeration of AuNPsThe FWHM and otherexperimental results are listed in Table 1

324 Effect of Amorphous Carbon Nanotube (120572-CNTs)sOxides and Sulphate to Chitosan Capped AuNPs Figure 10shows the SPR peaks of chitosan capped AuNPs adjournedat 549 nm for three different weights of 120572-CNTs The SPRpeak intensity rises as the weight of 120572-CNTs increases Thisphenomenon can be explained with regard to the fact thatAuNPs are very sensitive in the weight change of 120572-CNTsupon exposure High surface ratios of AuNPs contribute tothe sensitivities and make them more reactive and able touptake the analyte

Figure 11 shows the absorption spectra of chitosan cappedAuNPsmixedwith different weights of copper oxideThe SPRpeaks are shifted from 521 to 577 nm as the weight of copperoxide increases This clearly shows the complexation ofchitosan cappedAuNPs towards the addition of copper oxideThe enlargement of the particles uptake can be underlined asthe peak intensity also shows dramatic increase as the weightof copper oxide increases

Figure 12 shows the absorption spectra of chitosan cappedAuNPs at different weights of zinc sulphate The spectra alsosuccessfully show analyte particles entrapment by chitosan

6 The Scientific World Journal

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

001(b) 0005(a) 005(c)

01(d)

Figure 11 Absorption spectra of chitosan capped AuNPs mixedwith different weights of copper oxide (a) 0005 g (b) 001 g (c)005 g (d) 01 g

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) 001(b) 005

Figure 12 Absorption spectra of chitosan capped AuNPs mixed atdifferent weights of zinc sulphate (a) 001 g (b) 005 g

capped AuNPsThe SPR peaks intensities are increased as theweight of zinc sulphate added to the chitosan capped AuNPsincreases

4 Conclusion

We have successfully synthesized chitosan capped AuNPs viachemical reduction technique We have also revealed thatAuNPs revolutionize their dimension and optical behaviourthrough variation of parameters such as concentration ofreducing agent weight of stabilizer and aging time Chitosanconcentration plays an important role in imparting extrahindrance strengthThe particles stability was contributed bychitosan even after 1 month of aging The chitosan capped

AuNPs were able to uptake analyte such as 120572-CNTs copperoxide and zinc sulphate

Conflict of Interests

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

Acknowledgments

The authors would like to express their greatest gratitude tothe Ministry of Higher Education of Malaysia and Universityof Malaya for funding through UMMOHE-HIR ResearchGrant (UMCHIRMOHEENG12) Special thanks are dueto Mr Low Chien Chong for providing the TEM images

References

[1] D A HandleyColloidal Gold Principles Methods and Applica-tions Academic Press New York NY USA 1989 edited by MA Hayat

[2] C Roos M Schmidt J Ebenhoch F Baumann B Deubzerand J Weis ldquoDesign and synthesis of molecular reactors for thepreparation of topologically trapped gold clustersrdquo AdvancedMaterials vol 11 no 9 pp 761ndash766 1999

[3] R G Freeman M B Hommer K C Grabar M A Jacksonand M J Natan ldquoAg-clad Au nanoparticles novel aggregationoptical and surface-enhanced Raman scattering propertiesrdquoJournal of Physical Chemistry vol 100 no 2 pp 718ndash724 1998

[4] L Cao P Diao L Tong T Zhu and Z Liu ldquoSurface-enhanced Raman scattering of p-aminothiophenol on aAu(core)Cu(shell) nanoparticle assemblyrdquo ChemPhysChemvol 6 no 5 pp 913ndash918 2005

[5] N Toshima and T Yonezawa ldquoBimetallic nanoparticles novelmaterials for chemical and physical applicationsrdquo New Journalof Chemistry vol 22 no 11 pp 1179ndash1201 1998

[6] J Turkevich P C Stevenson and J Hillier ldquoA study of thenucleation and growth processes in the synthesis of colloidalgoldrdquo Discussions of the Faraday Society vol 11 pp 55ndash75 1951

[7] J Frens ldquoControlled nucleation for the regulation of the particlesize inmonodisperse gold suspensionsrdquoNature Physical Sciencevol 241 pp 20ndash22 1973

[8] M-C Daniel and D Astruc ldquoGold nanoparticles assemblysupramolecular chemistry quantum-size-related propertiesand applications toward biology catalysis and nanotechnol-ogyrdquo Chemical Reviews vol 104 no 1 pp 293ndash346 2004

[9] A Sugunan C Thanachayanont J Dutta and J G HilbornldquoHeavy-metal ion sensors using chitosan-capped gold nanopar-ticlesrdquo Science and Technology of Advanced Materials vol 6 no3-4 pp 335ndash340 2005

[10] S Mandal P R Selvakannan S Phadtare R Pasricha and MSastry ldquoSynthesis of a stable gold hydrosol by the reduction ofchloroaurate ions by the amino acid aspartic acidrdquo Journal ofChemical Sciences vol 114 no 5 pp 513ndash520 2002

[11] A Sugunan and J Dutta ldquoNovel synthesis of gold nanoparticlesin aqueous mediardquo in Proceedings of the Material ResearchSociety Fall Conference MRS Boston Mass USA 1999

[12] H C Warad S C Ghosh C Thanachayanont and J DuttaldquoHighly luminescent manganese doped ZnS quantum dots forbiological labelingrdquo in Proceedings of International Conference

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012

The Scientific World Journal 5

Table 1 Experimental values of SPR peaks for bare and chitosan capped AuNPs with full width half maximum (FWHM) after 1 month ageingtime

Sample SPR 120582max (nm) FHWM (nm)Concentration of MSG (mM) AuNPs Chitosan capped AuNPs AuNPs Chitosan capped AuNPs100 532 531 51 60150 544 537 72 52200 554 539 52 51250 544 527 96 46300 534 526 70 57

0

02

04

06

08

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 8 Absorption spectra of AuNPs with various concentrationsof reducing agent MSG after 1 month aging time (a) 100mM (b)150mM (c) 200mM (d) 250mM (e) 300mM

0

02

04

06

08

1

400 450 500 550 600 650 700Wavelength (nm)

minus02

Abso

rban

ce

150mM(b)100 mM(a)

200 mM(c)

250mM(d)300 mM(e)

Figure 9 Absorption spectra of chitosan capped AuNPs withvarious concentrations of reducing agent MSG after 1 month agingtime (a) 100mM (b) 150mM (c) 200mM (d) 250mM (e)300mM

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)minus02

(a) 0001(b) 0005(c) 005

Figure 10 Absorption spectra of chitosan capped AuNPs mixedwith different weights of 120572-CNTs (a) 0001 g (b) 0005 g (c) 005 g

and hinders agglomeration of AuNPsThe FWHM and otherexperimental results are listed in Table 1

324 Effect of Amorphous Carbon Nanotube (120572-CNTs)sOxides and Sulphate to Chitosan Capped AuNPs Figure 10shows the SPR peaks of chitosan capped AuNPs adjournedat 549 nm for three different weights of 120572-CNTs The SPRpeak intensity rises as the weight of 120572-CNTs increases Thisphenomenon can be explained with regard to the fact thatAuNPs are very sensitive in the weight change of 120572-CNTsupon exposure High surface ratios of AuNPs contribute tothe sensitivities and make them more reactive and able touptake the analyte

Figure 11 shows the absorption spectra of chitosan cappedAuNPsmixedwith different weights of copper oxideThe SPRpeaks are shifted from 521 to 577 nm as the weight of copperoxide increases This clearly shows the complexation ofchitosan cappedAuNPs towards the addition of copper oxideThe enlargement of the particles uptake can be underlined asthe peak intensity also shows dramatic increase as the weightof copper oxide increases

Figure 12 shows the absorption spectra of chitosan cappedAuNPs at different weights of zinc sulphate The spectra alsosuccessfully show analyte particles entrapment by chitosan

6 The Scientific World Journal

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

001(b) 0005(a) 005(c)

01(d)

Figure 11 Absorption spectra of chitosan capped AuNPs mixedwith different weights of copper oxide (a) 0005 g (b) 001 g (c)005 g (d) 01 g

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) 001(b) 005

Figure 12 Absorption spectra of chitosan capped AuNPs mixed atdifferent weights of zinc sulphate (a) 001 g (b) 005 g

capped AuNPsThe SPR peaks intensities are increased as theweight of zinc sulphate added to the chitosan capped AuNPsincreases

4 Conclusion

We have successfully synthesized chitosan capped AuNPs viachemical reduction technique We have also revealed thatAuNPs revolutionize their dimension and optical behaviourthrough variation of parameters such as concentration ofreducing agent weight of stabilizer and aging time Chitosanconcentration plays an important role in imparting extrahindrance strengthThe particles stability was contributed bychitosan even after 1 month of aging The chitosan capped

AuNPs were able to uptake analyte such as 120572-CNTs copperoxide and zinc sulphate

Conflict of Interests

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

Acknowledgments

The authors would like to express their greatest gratitude tothe Ministry of Higher Education of Malaysia and Universityof Malaya for funding through UMMOHE-HIR ResearchGrant (UMCHIRMOHEENG12) Special thanks are dueto Mr Low Chien Chong for providing the TEM images

References

[1] D A HandleyColloidal Gold Principles Methods and Applica-tions Academic Press New York NY USA 1989 edited by MA Hayat

[2] C Roos M Schmidt J Ebenhoch F Baumann B Deubzerand J Weis ldquoDesign and synthesis of molecular reactors for thepreparation of topologically trapped gold clustersrdquo AdvancedMaterials vol 11 no 9 pp 761ndash766 1999

[3] R G Freeman M B Hommer K C Grabar M A Jacksonand M J Natan ldquoAg-clad Au nanoparticles novel aggregationoptical and surface-enhanced Raman scattering propertiesrdquoJournal of Physical Chemistry vol 100 no 2 pp 718ndash724 1998

[4] L Cao P Diao L Tong T Zhu and Z Liu ldquoSurface-enhanced Raman scattering of p-aminothiophenol on aAu(core)Cu(shell) nanoparticle assemblyrdquo ChemPhysChemvol 6 no 5 pp 913ndash918 2005

[5] N Toshima and T Yonezawa ldquoBimetallic nanoparticles novelmaterials for chemical and physical applicationsrdquo New Journalof Chemistry vol 22 no 11 pp 1179ndash1201 1998

[6] J Turkevich P C Stevenson and J Hillier ldquoA study of thenucleation and growth processes in the synthesis of colloidalgoldrdquo Discussions of the Faraday Society vol 11 pp 55ndash75 1951

[7] J Frens ldquoControlled nucleation for the regulation of the particlesize inmonodisperse gold suspensionsrdquoNature Physical Sciencevol 241 pp 20ndash22 1973

[8] M-C Daniel and D Astruc ldquoGold nanoparticles assemblysupramolecular chemistry quantum-size-related propertiesand applications toward biology catalysis and nanotechnol-ogyrdquo Chemical Reviews vol 104 no 1 pp 293ndash346 2004

[9] A Sugunan C Thanachayanont J Dutta and J G HilbornldquoHeavy-metal ion sensors using chitosan-capped gold nanopar-ticlesrdquo Science and Technology of Advanced Materials vol 6 no3-4 pp 335ndash340 2005

[10] S Mandal P R Selvakannan S Phadtare R Pasricha and MSastry ldquoSynthesis of a stable gold hydrosol by the reduction ofchloroaurate ions by the amino acid aspartic acidrdquo Journal ofChemical Sciences vol 114 no 5 pp 513ndash520 2002

[11] A Sugunan and J Dutta ldquoNovel synthesis of gold nanoparticlesin aqueous mediardquo in Proceedings of the Material ResearchSociety Fall Conference MRS Boston Mass USA 1999

[12] H C Warad S C Ghosh C Thanachayanont and J DuttaldquoHighly luminescent manganese doped ZnS quantum dots forbiological labelingrdquo in Proceedings of International Conference

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012

6 The Scientific World Journal

0

01

02

03

04

05

06

07

08

09

1

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

001(b) 0005(a) 005(c)

01(d)

Figure 11 Absorption spectra of chitosan capped AuNPs mixedwith different weights of copper oxide (a) 0005 g (b) 001 g (c)005 g (d) 01 g

0

02

04

06

08

1

12

400 450 500 550 600 650 700

Abso

rban

ce

Wavelength (nm)

(a) 001(b) 005

Figure 12 Absorption spectra of chitosan capped AuNPs mixed atdifferent weights of zinc sulphate (a) 001 g (b) 005 g

capped AuNPsThe SPR peaks intensities are increased as theweight of zinc sulphate added to the chitosan capped AuNPsincreases

4 Conclusion

We have successfully synthesized chitosan capped AuNPs viachemical reduction technique We have also revealed thatAuNPs revolutionize their dimension and optical behaviourthrough variation of parameters such as concentration ofreducing agent weight of stabilizer and aging time Chitosanconcentration plays an important role in imparting extrahindrance strengthThe particles stability was contributed bychitosan even after 1 month of aging The chitosan capped

AuNPs were able to uptake analyte such as 120572-CNTs copperoxide and zinc sulphate

Conflict of Interests

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

Acknowledgments

The authors would like to express their greatest gratitude tothe Ministry of Higher Education of Malaysia and Universityof Malaya for funding through UMMOHE-HIR ResearchGrant (UMCHIRMOHEENG12) Special thanks are dueto Mr Low Chien Chong for providing the TEM images

References

[1] D A HandleyColloidal Gold Principles Methods and Applica-tions Academic Press New York NY USA 1989 edited by MA Hayat

[2] C Roos M Schmidt J Ebenhoch F Baumann B Deubzerand J Weis ldquoDesign and synthesis of molecular reactors for thepreparation of topologically trapped gold clustersrdquo AdvancedMaterials vol 11 no 9 pp 761ndash766 1999

[3] R G Freeman M B Hommer K C Grabar M A Jacksonand M J Natan ldquoAg-clad Au nanoparticles novel aggregationoptical and surface-enhanced Raman scattering propertiesrdquoJournal of Physical Chemistry vol 100 no 2 pp 718ndash724 1998

[4] L Cao P Diao L Tong T Zhu and Z Liu ldquoSurface-enhanced Raman scattering of p-aminothiophenol on aAu(core)Cu(shell) nanoparticle assemblyrdquo ChemPhysChemvol 6 no 5 pp 913ndash918 2005

[5] N Toshima and T Yonezawa ldquoBimetallic nanoparticles novelmaterials for chemical and physical applicationsrdquo New Journalof Chemistry vol 22 no 11 pp 1179ndash1201 1998

[6] J Turkevich P C Stevenson and J Hillier ldquoA study of thenucleation and growth processes in the synthesis of colloidalgoldrdquo Discussions of the Faraday Society vol 11 pp 55ndash75 1951

[7] J Frens ldquoControlled nucleation for the regulation of the particlesize inmonodisperse gold suspensionsrdquoNature Physical Sciencevol 241 pp 20ndash22 1973

[8] M-C Daniel and D Astruc ldquoGold nanoparticles assemblysupramolecular chemistry quantum-size-related propertiesand applications toward biology catalysis and nanotechnol-ogyrdquo Chemical Reviews vol 104 no 1 pp 293ndash346 2004

[9] A Sugunan C Thanachayanont J Dutta and J G HilbornldquoHeavy-metal ion sensors using chitosan-capped gold nanopar-ticlesrdquo Science and Technology of Advanced Materials vol 6 no3-4 pp 335ndash340 2005

[10] S Mandal P R Selvakannan S Phadtare R Pasricha and MSastry ldquoSynthesis of a stable gold hydrosol by the reduction ofchloroaurate ions by the amino acid aspartic acidrdquo Journal ofChemical Sciences vol 114 no 5 pp 513ndash520 2002

[11] A Sugunan and J Dutta ldquoNovel synthesis of gold nanoparticlesin aqueous mediardquo in Proceedings of the Material ResearchSociety Fall Conference MRS Boston Mass USA 1999

[12] H C Warad S C Ghosh C Thanachayanont and J DuttaldquoHighly luminescent manganese doped ZnS quantum dots forbiological labelingrdquo in Proceedings of International Conference

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012

The Scientific World Journal 7

on Smart Materials SmartIntelligent Materials and Nanotech-nology (SmartMat rsquo04) pp 203ndash207 Chiang Mai Thailand2004

[13] N Nath and A Chilkoti ldquoLabel-free biosensing by surfaceplasmon resonance of nanoparticles on glass optimization ofnanoparticle sizerdquo Analytical Chemistry vol 76 no 18 pp5370ndash5378 2004

[14] V Pavlov Y Xiao B Shlyahovsky and I Willner ldquoAptamer-functionalized Au nanoparticles for the amplified optical detec-tion of thrombinrdquo Journal of the American Chemical Society vol126 no 38 pp 11768ndash11769 2004

[15] C Huang Y Huang Z Cao W Tan and H Chang ldquoAptamer-modified gold nanoparticles for colorimetric determination ofplatelet-derived growth factors and their receptorsrdquo AnalyticalChemistry vol 77 no 17 pp 5735ndash5741 2005

[16] D CHone AHHaines andDA Russell ldquoRapid quantitativecolorimetric detection of a lectin usingmannose-stabilized goldnanoparticlesrdquo Langmuir vol 19 no 17 pp 7141ndash7144 2003

[17] K Fujiwara H Watarai H Itoh E Nakahama and N OgawaldquoMeasurement of antibody binding to protein immobilized ongold nanoparticles by localized surface plasmon spectroscopyrdquoAnalytical and Bioanalytical Chemistry vol 386 no 3 pp 639ndash644 2006

[18] F Frederix J Friedt K Choi et al ldquoBiosensing based on lightabsorption of nanoscaled gold and silver particlesrdquo AnalyticalChemistry vol 75 no 24 pp 6894ndash6900 2003

[19] F L Mi S S Shyu C Y Kuan S T Lee K T Lu and S F AjngldquoChitosan-polyelectrolyte complexation for the preparation ofgel beads and controlled release of anticancer drug I Effect ofphosphorus polyelectrolyte complex and enzymatic hydrolysisof polymerrdquo Journal of Applied Polymer Science vol 74 pp1868ndash1879 1999

[20] K H Tan R Ahmad B F Leo M C Yew B C Ang andM R Johan ldquoPhysico-chemical studies of amorphous carbonnanotubes synthesized at low temperaturerdquo Materials ResearchBulletin vol 47 no 8 pp 1849ndash1854 2012