Geckeler K.E., Nishide H. (Eds.) Advanced Nanomaterials

References 245

Nielsch , K. ( 2007 ) J. Am. Chem. Soc. ,

129 , 9554 .

136 Yu , X. , Cao , C. and An , X. ( 2008 ) Chem.

Mater. , 20 , 1936 .

137 Wang , J. , Ma , Y. and Watanabe , K.

( 2008 ) Chem. Mater. , 20 , 20 .

138 Wang , T. , Wang , Y. , Li , F. , Xu , C. and

Zhou , D. ( 2006 ) J. Phys. Condens. Matter ,

18 , 10 545 .

139 Geng , F. , Zhao , Z. , Geng , J. , Cong , H.

and Cheng , H. - M. ( 2007 ) Mater. Lett. , 61 ,

4794 .

140 Lou , X.W. , Deng , D. , Lee , J.Y. , Feng , J.

and Archer , L.A. ( 2008 ) Adv. Mater. , 20 ,

258 .

141 Shen , X. - P. , Miao , H. - J. , Zhao , H. and

Xu , Z. ( 2008 ) Appl. Phys. A , 91 , 47 .

142 Xu , Y. , Wei , J. , Yao , J. , Fu , J. and Xue ,

D. ( 2008 ) Mater. Lett. , 62 , 1403 .

143 Malandrino , G. , Perdicaro , L.M.S. ,

Fragala , I.L. , Nigro , R. Lo , Losurdo , M.

and Bruno , G. ( 2007 ) J. Phys. Chem. C ,

111 , 3211 .

144 Shi , C. , Wang , G. , Zhao , N. , Du , X. and

Li , J. ( 2008 ) Chem. Phys. Lett. , 454 , 75 .

145 Zhao , Z. - G. and Miyauchi , M. ( 2008 )

Angew. Chem. Int. Ed. , 47 , 7051 .

146 Yan , Y. , Zhou , L. , Zhang , J. , Zeng , H. ,

Zhang , Y. and Zhang , L. ( 2008 ) J. Phys.

Chem. C , 112 , 10 412 .

147 Lu , H.B. , Liao , L. , Li , H. , Tian , Y. , Li ,

J.C. , Wang , D.F. and Zhu , B.P. ( 2007 )

J. Phys. Chem. C , 111 , 10 273 .

148 Chen , C. , Chen , D. , Jiao , X. and Wang ,

C. ( 2006 ) Chem. Commun. , 4632 .

149 Zhong , M. , Zheng , M. , Ma , L. , Li , Y.

( 2007 ) Nanotechnology , 18 , 465 605 .

150 Du , N. , Zhang , H. , Chen , B. , Ma , X. ,

Liu , Z. , Wu , J. and Yang , D. ( 2007 ) Adv.

Mater. , 19 , 1641 .

151 Rajasekharan , V.V. and Buttry , D.A.

( 2006 ) Chem. Mater. , 18 , 4541 .

152 Mao , Y. , Huang , J.Y. , Ostroumov , R. ,

Wang , K.L. and Chang , J.P. ( 2008 )

J. Phys. Chem. C , 112 , 2278 .

153 Du , N. , Zhang , H. , Chen , B. , Ma , X. and

Yang , D. ( 2008 ) Chem. Commun. , 3028 .

154 Wang , N. , Cao , X. and Guo , L. ( 2008 )

J. Phys. Chem. C , 112 , 12 616 .

155 Lai , M. , Martinez , J.A.G. , Gratzel , M.

and Riley , D.J. ( 2006 ) J. Mater. Chem. ,

16 , 2843 .

156 Aoki , Y. , Huang , J. and Kunitake , T.

( 2006 ) J. Mater. Chem. , 16 , 292 .

157 Zhao , J. , Wang , X. , Xu , R. , Meng , F. ,

Guo , L. and Li , Y. ( 2008 ) Mater. Lett. , 62 ,

4428 .

158 Meng , X. , Tan , X. , Meng , B. , Yang , N.

and Ma , Z. - F. ( 2008 ) Mater. Chem. Phys. ,

111 , 275 .

159 Han , W.Q. , Wu , L.J. and Zhu , Y.M.

( 2005 ) J. Am. Chem. Soc. , 127 ,

12 814 .

160 Zhou , K. , Yang , Z. and Yang , S. ( 2007 )

Chem. Mater. , 19 , 1215 .

161 Inguanta , R. , Piazza , S. and Sunseri , C.

( 2007 ) Nanotechnology , 18 , 485 605 .

162 Lin , Z. - W. , Kuang , Q. , Lian , W. , Jiang ,

Z. - Y. , Xie , Z. - X. , Huang , R. - B. and

Zheng , L. - S. ( 2006 ) J. Phys. Chem. B ,

110 , 23 007 .

163 Bao , N. , Shen , L. , Srinivasan , G. ,

Yanagisawa , K. and Gupta , A. ( 2008 )

J. Phys. Chem. C , 112 , 8634 .

164 Yang , Y. , Wang , X. , Zhong , C. , Sun , C.

and Li , L. ( 2008 ) Appl. Phys. Lett. , 92 ,

122 907 .

165 Singh , S. and Krupanidhi , S.B. ( 2007 )

Appl. Phys. A , 87 , 27 .

166 Nourmohammadi , A. , Bahrevar , M.A.

and Hietschold , M. ( 2008 ) Mater. Lett. ,

62 , 3349 .

167 Yasuda , K. and Schmuki , P. ( 2007 ) Adv.

Mater. , 19 , 1757 .

168 Saupe , G.B. , Waraksa , C.C. , Kim , H.N. ,

Han , Y.J. , Kaschak , D.M. , Skinner , D.M.

and Mallouk , T.E. ( 2000 ) Chem. Mater. ,

12 , 1556 .

169 Du , G. , Chen , Q. , Yu , Y. , Zhang , S. ,

Zhu , W. and Peng , L.M. ( 2004 ) J. Mater.

Chem. , 14 , 1437 .

170 Tong , Z. , Takagi , S. , Shimada , T. ,

Tachibana , H. and Inoue , H. ( 2006 )

J. Am. Chem. Soc. , 128 , 684 .

171 Yu , D. , Qian , J. , Xue , N. , Zhang , D. ,

Wang , C. , Guo , X. , Ding , W. and Chen ,

Y. ( 2007 ) Langmuir , 23 , 382 .

172 Yu , J. , Wang , A. , Tan , J. , Li , X. ,

Bokhoven , J.A.V. and Hu , Y. ( 2008 )

J. Mater. Chem. , 18 , 3601 .

173 Fang , Y. , Wen , X. and Yang , S. ( 2006 )

Angew. Chem. Int. Ed. , 45 , 4655 .

174 Yan , C. , Zhang , T. and Lee , P.S. ( 2008 )

Cryst. Growth , Des. , 8 , 3144 .

175 Wang , Y. and Cao , G. ( 2007 ) J. Mater.

Chem. , 17 , 894 .

176 Wang , Z. , Zhou , S. and Wu , L. ( 2007 )

Adv. Funct. Mater. , 17 , 1790 .

246 6 Synthesis of Inorganic Nanotubes

177 Olson , B.G. , Decker , J.J. , Nazarenko , S. ,

Yudin , V.E. , Otaigbe , J.U. , Korytkova ,

E.N. and Gusarov , V.V. ( 2008 ) J. Phys.

Chem. C , 112 , 12 943 .

178 Levard , C. , Rose , J. , Masion , A. , Doelsch ,

E. , Borschneck , D. , Olivi , L. , Dominici ,

C. , Grauby , O. , Woicik , J.C. and

Bottero , J. - Y. ( 2008 ) J. Am. Chem. Soc. ,

130 , 5862 .

179 Yu , T. , Park , J. , Moon , J. , An , K. , Piao ,

Y. and Hyeon , T. ( 2007 ) J. Am. Chem.

Soc. , 129 , 14 558 .

180 Zhao , Y. , Frost , R.L. , Martens , W.N.

and Zhu , H.Y. ( 2007 ) Langmuir , 23 ,

9850 .

181 Yuan , Y. , Liu , C. , Zhang , Y. and Shan ,

X. ( 2008 ) Mater. Chem. Phys. , 112 , 275 .

182 Liu , W. , Wang , S. , Chen , Y. , Fang , G. ,

Li , M. and Zhao , X. - Z. ( 2008 ) Sensors

Actuators B , 134 , 62 .

183 Fan , H.J. , Knez , M. , Scholz , R. , Nielsch ,

K. , Pippel , E. , Hesse , D. , Zacharias , M.

and Gosele , U. ( 2006 ) Nat. Mater. , 5 ,

627 .

184 Ye , C. , Bando , Y. , Shen , G. and Golberg ,

D. ( 2006 ) Angew. Chem. Int. Ed. , 45 ,

4922 .

185 Song , S. , Zhang , Y. , Xing , Y. , Wang , C. ,

Feng , J. , Shi , W. , Zheng , G. and Zhang ,

H. ( 2008 ) Adv. Funct. Mater. , 18 , 2328 .

186 Mukherjee , S. , Kim , K. and Nair , S.

( 2007 ) J. Am. Chem. Soc. , 129 , 6820 .

187 Chen , W. and Xia , X. - H. ( 2007 ) Adv.

Funct. Mater. , 17 , 2943 .

188 Chen , Y. and Wu , Q. ( 2008 ) Colloids ,

Surf. A , 325 , 33 .

189 Huang , K. - W. , Wang , J. - H. , Chen , H. - C. ,

Hsu , H. - C. , Chang , Y. - C. , Lu , M. - Y. , Lee ,

C. - Y. and Chen , L. - J. ( 2007 ) J. Mater.

Chem. , 17 , 2307 .

190 Chen , R. , So , M.H. , Yang , J. , Deng , F. ,

Che , C. - M. and Sun , H. ( 2006 ) Chem.

Commun. , 2265 .

191 Loiseau , A. , Williame , F. , Demonecy , N. ,

Hug , G. and Pascard , H. ( 1996 ) Phys.

Rev. Lett. , 76 , 4737 .

192 Chopra , N.G. , Luyken , R.G. , Cherrey ,

K. , Crespi , V.H. , Cohen , M.L. , Louie ,

S.G. and Zettl , A. ( 1995 ) Science , 269 ,

966 .

193 Terrones , M. , Hsu , W.K. , Terrones , H. ,

Zhang , J.P. , Ramos , S. , Hare , J.P. ,

Castillo , R. , Prassides , K. , Cheetham ,

A.K. . Kroto , H.W. , Walton , D.R.M.

( 1996 ) Chem. Phys. Lett. , 259 , 568 .

194 a) Yu , D.P. , Sun , X.S. , Lee , C.S. , Bello ,

I. , Lee , S.T. , Gu , H.D. , Leung , K.M. ,

Zhou , G.W. , Dong , Z.F. and Zhang , Z.

( 1998 ) Appl. Phys. Lett. , 72 , 1966 .

b) Zhou , G.W. , Zhang , Z. , Bai , Z.G.

and Yu , D.P. ( 1999 ) Solid , State ,

Commun. , 109 , 555 . c) Terauchi , M. ,

Tanaka , M. , Matsuda , H. , Takeda , M.

and Kimura , K. ( 1997 ) J. Electron

Microsc. , 1 , 75 .

195 Laude , T. , Matsui , Y. , Marraud , A. and

Jouffrey , B. ( 2000 ) Appl. Phys. Lett. , 76 ,

3239 .

196 a) Golberg , D. , Bando , Y. , Han , W. ,

Kurashima , K. and Sato , T. ( 1999 ) Chem.

Phys. Lett. , 308 , 337 . b) Fowler , P.W. ,

Rogers , K.M. , Seifert , G. , Terrones , M.

and Terrones , H. ( 1999 ) Chem. Phys.

Lett. , 299 , 359 .

197 Bengu , E. and Marks , L.D. ( 2001 ) Phys.

Rev. Lett. , 86 , 2385 .

198 Tang , C.C. , Bando , Y. , Sato , T. and

Kurashima , K. ( 2002 ) Chem. Commun. ,

1290 .

199 Zhi , C.Y. , Bando , Y. , Tang , C. and

Golberg , D. ( 2005 ) Solid State Commun. ,

135 , 67 .

200 Deepak , F.L. , Vinod , C.P. ,

Mukhopadhyay , K. , Govindaraj , A. and

Rao , C.N.R. ( 2002 ) Chem. Phys. Lett. ,

353 , 345 .

201 Wang , J. , Kayastha , V.K. , Yap , Y.K. , Fan ,

Z. , Lu , J.G. , Pan , Z. , Ivanov , I.N. ,

Puretzky , A.A. and Geohegan , D.B.

( 2005 ) Nano Lett. , 5 , 2528 .

202 Pal , S. , Vivekchand , S.R.C. , Govindaraj ,

A. and Rao , C.N.R. ( 2007 ) J. Mater.

Chem. , 17 , 450 .

203 a) Golberg , D. , Bando , Y. , Tang , C. and

Zhi , C. ( 2007 ) Adv. Mater. , 19 , 2413 . b)

Golberg , D. , Bando , Y. , Bourgeois , L. ,

Kurashima , K. and Sato , T. ( 2000 )

Appl. Phys. Lett. , 77 , 1979 .

204 Dai , J. , Xu , L. , Fang , Z. , Sheng , D. , Guo ,

Q. , Ren , Z. , Wang , K. and Qian , Y.

( 2007 ) Chem. Phys. Lett. , 440 , 253 .

205 Chen , X. , Wang , X. , Liu , J. , Wang , Z.

and Qian , Y. ( 2005 ) Appl. Phys. A , 81 ,

1035 .

References 247

206 Oku , T. , Koi , N. and Suganuma , K.

( 2008 ) Diamond Relat. Mater. , 17 , 1805 .

207 Wang , X.Z. , Wu , Q. , Hu , Z. and Chen ,

Y. ( 2007 ) Electrochem. Acta , 52 , 2841 .

208 Chen , H. , Chen , Y. , Liu , Y. , Fu , L. ,

Huang , C. and Llewellyn , D. ( 2008 )

Chem. Phys. Lett. , 463 , 130 .

209 Bechelany , M. , Bernard , S. , Brioude , A. ,

Cornu , D. , Stadelmann , P. , Charcosset ,

C. , Fiaty , K. and Miele , P. ( 2007 ) J. Phys.

Chem. C , 111 , 13 378 .

210 Kim , M.J. , Chatterjee , S. , Kim , S.M. ,

Stach , E.A. , Bradley , M.G. , Pender , M.J. ,

Sneddon , L.G. and Maruyama , B. ( 2008 )

NanoLett. , 8 , 3298 .

211 Arenal , R. , Stephan , O. , Cochon , J. - L.

and Loiseau , A. ( 2007 ) J. Am. Chem.

Soc. , 129 , 16 183 .

212 Wang , W.L. , Bai , X.D. , Liu , K.H. , Xu , Z. ,

Golberg , D. , Bando , Y. and Wang , E.G.

( 2006 ) J. Am. Chem. Soc. , 128 , 6530 .

213 Raidongia , K. , Jagadeesan , D. ,

Upadhyay - Kahaly , M. , Waghmare , U.V. ,

Pati , S.K. , Eswaramoorthy , M. and Rao ,

C.N.R. ( 2008 ) J. Mater. Chem. , 18 , 83 .

214 Jung , W. - G. , Jung , S. - H. , Kung , P. and

Razeghi , M. ( 2006 ) Nanotechnology , 17 ,

54 .

215 Gai , L. , Jiang , H. , Ma , W. , Cui , D. , Lun ,

N. , Wang , Q. ( 2007 ) J. Phys. Chem. C ,

111 , 2386 .

216 Dinesh , J. , Eswaramoorthy , M. and

Rao , C.N.R. ( 2007 ) J. Phys. Chem. C ,

111 , 510 .

217 Wang , F. , Jin , G. - Q. and Guo , X. - Y.

( 2006 ) Mater. Lett. , 60 , 330 .

218 Miikkulainen , V. , Suvanto , M. and

Pakkanen , T.A. ( 2008 ) Thin Solid Films ,

516 , 6041 .

219 Shen , G. , Bando , Y. , C.Y e, Yuan , X. ,

Sekiguchi , T. and Golberg , D. ( 2006 )

Angew. Chem. Int. Ed. , 45 , 7568 .

220 Malliakas , C.D. and Kanatzidis , M.G.

( 2006 ) J. Am. Chem. Soc. , 128 , 6538 .

221 Li , B. , Wu , R. , Pan , Y. , Wu , L. , Yang , G. ,

Chen , J. and Zhu , Q. ( 2008 ) J. Alloys

Compounds , 462 , 446 .

222 Taguchi , T. and Yamamoto , H. ( 2007 )

J. Phys. Chem. C , 111 , 18 888 .

223 Wan , C. , Guo , G. , Zhang , Q. ( 2008 )

Mater. Lett. , 62 , 2776 .

224 Liao , L. , Xu , Z. , Liu , K.H. , Wang , W.L. ,

Liu , S. , Bai , X.D. , Wang , E.G. , Li , J.C.

and Liu , C. ( 2007 ) J. Appl. Phys. , 101 ,

114 306 .

225 Hacohen , Y.R. , Grunbaum , E. , Tenne ,

R. , Sloan , J. and Hutchison , J.L. ( 1998 )

Nature , 395 , 336 .

226 Zeng , J. , Liu , C. , Huang , J. , Wang , X. ,

Zhang , S. , Li , G. and Hou , J. ( 2008 )

Nano Lett. , 8 , 1318 .

227 Fan , D.H. , Shen , W.Z. , Zheng , M.J. ,

Zhu , Y.F. and Lu , J.J. ( 2007 ) J. Phys.

Chem. C , 111 , 9116 .

228 Yan , C. and Xue , D. ( 2006 ) J. Phys.

Chem. B , 110 , 25 850 .

229 Yin , Y. , Jin , Z. and Hou , F. ( 2007 )

Nanotechnology , 18 , 495 608 .

230 Gautam , U.K. , Fang , X. , Bando , Y. ,

Zhan , J. and Golberg , D. ( 2008 ) ACS

Nano , 2 , 1015 .

231 Liao , H. - C. , Kuo , P. - C. , Lin , C. - C. and

Chen , S. - Y. ( 2006 ) J. Vac. Sci. Technol. ,

24 , 2198 .

232 Yang , D. , Meng , G. , Zhang , S. , Hao ,

Y. , An , X. , Wei , Q. , Ye , M. and Zhang ,

L. ( 2007 ) Chem. Commun. , 1733 .

233 Yang , L. , Luo , S. , Liu , S. and Cai , Q. ,

( 2008 ) J. Phys. Chem. C , 112 , 8939 .

234 Chen , H. , Chen , S. , Quan , X. , Yu , H. ,

Zhao , H. and Zhang , Y. ( 2008 ) J. Phys.

Chem. C , 112 , 9285 .

235 Djenizian , T. , Hanzu , I. and Premchand ,

Y.D. ( 2008 ) Nanotechnology , 19 ,

205 601 .

236 Mohapatra , S.K. , Banerjee , S. and

Misra , M. ( 2008 ) Nanotechnology , 19 ,

315 601 .

237 Chueh , Y. - L. , Chou , L. - J. and Wang , Z.L.

( 2006 ) Angew. Chem. Int. Ed. , 45 , 7773 .

238 Liao , L. , Liu , K. , Wang , W. , Bai , X. ,

Wang , E. , Liu , Y. , Li , J. and Liu , C.

( 2007 ) J. Am. Chem. Soc. , 129 , 9562 .

239 Chen , Z. - G. , Zou , J. , Li , F. , Liu , G. ,

Tang , D. - M. , Li , D. , Liu , C. , Ma , X. ,

Cheng , H. - M. , Lu , G.Q. and Zhang , Z.

( 2007 ) Adv. Funct. Mater. , 17 , 3371 .

Gold Nanoparticles and Carbon Nanotubes: Precursors for

Novel Composite Materials

Thathan Premkumar and Kurt E. Geckeler

249

Advanced Nanomaterials. Edited by Kurt E. Geckeler and Hiroyuki Nishide

ISBN: 978-3-527-31794-3

7

7.1

Introduction

One of the most stimulating challenges in modern chemistry, materials science,

and nanotechnology is the manipulation and assembly at the nanoscale. Carbon

nanotube s ( CNT s) constitute a novel class of nanomaterials with remarkable

applications in diverse domains. The attachment of metal nanoparticles to CNTs

represents a new means of obtaining novel hybrid materials with exciting charac-

teristics for a variety of applications such as catalysts and gas sensors, as well as

electronic and magnetic devices. These exceptional characteristics, which include

excellent electronic properties, good chemical stability, and a large surface area,

make CNTs good candidates as support materials for gold nanoparticles in many

key applications, ranging from advanced catalytic systems through very sensitive

electrochemical sensors and biosensors to highly efﬁ cient fuel cells. In this

chapter, we focus on the recent progress in this area by exploring the various

synthetic approaches and types of assemblies and interactions, in which gold

nanoparticles can be attached to CNTs, and also survey the various applications

of the resulting composites.

7.2

Gold Nanoparticles

The name of gold (Au) is derived from the Latin aurum (meaning “ shining dawn ” ).

Gold has the atomic number 79 (electron conﬁ guration, [Xe] 4f

14

, 5d

10

, 6s

1

), and is

one of the so - called “ noble ” metals, which are resistant to both corrosion and

oxidation. Gold is the most malleable and ductile of the known elements, with

characteristic properties of being dense, soft, and shiny. Gold nanoparticle s

( AuNP s), which are also known as “ colloidal gold ” or “ nanogold ” , are a colloid

of nanosized gold particles in a liquid (generally water). The ﬁ rst description of

250 7 Gold Nanoparticles and Carbon Nanotubes: Precursors for Novel Composite Materials

colloidal gold was reported by the philosopher and medical doctor Francisci

Antonii in 1618 [1] . Subsequently, in 1676, the chemist Johann Kunckles [2]

described “ … drinkable gold that contains metallic gold in a neutral, slightly pink

solution that exert curative properties for several diseases. ” Although colloidal gold

has been known from ancient times, when it was used as for staining glass, the

modern scientiﬁ c development of colloidal gold did not begin until Michael Fara-

day ’ s pioneering studies in the nineteenth century. In 1857, Faraday prepared a

red - colored solution of colloidal gold in a two - phase system by the reduction of an

aqueous solution of chloroaurate ( AuCl

4

−

) using phosphorus in carbon disulﬁ de

[3, 4] . The AuNPs are the most stable metal nanoparticles, and have been studied

extensively during the past decade owing to their fascinating aspects in materials

science, size - related electronics, and optical properties (quantum size effect), as

well as their applications in catalysis and biology. This is clearly evident from a

literature survey of published articles relating to AuNPs with respect to years [5] .

This analysis reveals that reports on AuNPs have increased signiﬁ cantly each year

(Figure 7.1 a), and indicates that remarkable attention – from both fundamental

Figure 7.1 Statistical survey of articles published on

(a) AuNPs and (b) CNTs. Contributions from the top ten

countries in percentage for (c) AuNPs and (d) CNTs.

7.3 Carbon Nanotubes 251

and applied aspects – has been paid to the synthesis, characterization, and potential

application of AuNPs.

When reducing the ﬁ rst, second or third dimensions (1 - D, 2 - D or 3 - D) of bulk

material to the nanometer scale, nanometer - thick 2 - D layers, 1 - D nanowires, or

0 - D nanoclusters, respectively, are produced. Nanoparticles have diameters of

< 100 nm and demonstrate new or enhanced size - dependent properties when com-

pared to larger particles, or to the bulk entity of the same material. Metal nano-

particles – and especially AuNPs – appeared as a new class of materials which were

of interest not only in the ﬁ elds of materials science and chemistry but also in

nanotechnology, on the basis of their exceptional catalytic, electronic, and optical

properties. Notably, these features related neither to the bulk metal nor to the

molecular compounds, but depended heavily on the particle size, the nature of the

protecting organic shell, and the shape of the nanoparticle [6] . For example, gold

nanocrystals of different shapes possess unique optical scattering responses.

Whilst symmetric spherical particles display a single scattering peak, anisotropic

shapes such as rods [7] , triangular prisms [8] , and cubes [9] exhibit multiple scat-

tering peaks in the visible wavelengths due to highly localized charge polarizations

at their corners and edges.

With regards to metallic gold, the nucleation and growth of nanoparticles have

been most widely achieved using colloidal methods rather than a variety of other

approaches [4] . In these techniques, the general approach is to reduce a gold salt

precursor in solution (mostly aqueous) in the presence of a stabilizing or protect-

ing agent; this improves the chemical stability of the AuNPs formed by avoiding

the aggregation among the particles. The advantages of these methods are: (i) large

quantities of nanoparticles can be synthesized; (ii) solution - based processing and

assembly can be readily implemented; (iii) no specialized equipment is necessary;

(iv) the technique is comparatively low - cost in nature; and (v) the preparation is

both facile and user - friendly. The aforesaid reasons are particularly important

when considering the real applications of AuNPs; in order to utilize AuNPs as

catalytic, electronic, or optical materials a large - scale synthesis and assembly

process is required.

7.3

Carbon Nanotubes

Carbon nanotubes, a new carbon allotrope, were discovered by Sumio Iijima

in 1991 [10] and have attracted wide and interdisciplinary attention. CNTs are

fullerene - related, tube - like structures which may be considered as a rolled - up sheet

of graphene. Every carbon atom is covalently bonded to three of its neighbors,

and the fourth electron is free to move over the whole structure; that is, it is delo-

calized (sp

2

- hybridization). There are two main types of CNT with high structural

perfection: single - walled carbon nanotube s ( SWNT s), and multiwalled carbon

nanotube s ( MWNT s). While the SWNTs consist of a single sp

2

- bonded graphene

sheet seamlessly wrapped into a hollow cylindrical tube, MWNTs include an array

252 7 Gold Nanoparticles and Carbon Nanotubes: Precursors for Novel Composite Materials

of concentric cylinders (a collection of several concentric SWNTs). Both of these

are typically a few nanometers in diameter (ca. between 0.4 and 3 nm for SWNTs,

and between 1.4 and 100 nm for MWNTs [11] ), and up to several micrometers to

millimeters in length. The SWNTs represent a very important type of CNT as they

exhibit signiﬁ cant electric properties that are not shared by the MWNT variants.

In analogy to the graphite modiﬁ cation of carbon, the unit cells of CNTs are planar

hexagons. CNTs may have a variety of helical structures [12] , depending on the

graphene sheet rolling - up phenomenon. The CNTs form bundles, which are

entangled together in the solid state, giving rise to a highly complex network.

Depending on the arrangement of the hexagon rings along the tubular surface,

CNTs can be either metallic or semiconducting.

The history of CNTs may be traced back to 1976, with the fabrication of very

small - diameter ( < 10 nm) carbon ﬁ laments [13, 14] . Nevertheless, until the discov-

ery of fullerene chemistry [15] in 1985, the importance of these as - prepared carbon

materials was not well documented. The discovery and development of fullerenes

led to an increased interest in carbon materials, and this in turn induced the

systematic study of carbon ﬁ laments. The CNT structure was ﬁ rst observed by

Iijima in 1991, using high - resolution transmission electron microscopy ( HR - TEM )

[10] . Although the ﬁ rst CNTs to be discovered were MWNTs, subsequently – in

1993 – smaller - diameter SWNTs were independently observed by Iijima [16] and

Bethune [17] . Since then, efﬁ cient methods for the synthesis of large - quantity [18]

and high - quality [19] CNTs, with their exciting electronic, mechanical, and struc-

tural properties, as well as their diverse potential applications, have paved the

way for global research interest and development activities. Today, these materials

form the subject of intensive investigation due not only to their academic

and industrial characteristics but also the scope of their application. Indeed, both

the number of studies on, and scientiﬁ c interest in, CNTs have increased dramati-

cally and continue to increase since their discovery – as demonstrated by the

huge numbers of articles relating to this topic which are published each year

(Figure 7.1 b).

Both, SWNTs and MWNTs may generally be synthesized using methods which

include arc - discharge [18, 20] , laser ablation [19, 21] , chemical vapor deposition

( CVD ) [22] , and the gas - phase catalytic process (HiPco) method [23] . Unfortu-

nately, no method has yet been introduced for the synthesis of pure CNTs; rather,

all of the methods proposed to date for the synthesis of CNTs lead not only to

impure products, such as carbon - coated metal catalysts, carbon - coated metal, and

carbon nanoparticles/amorphous carbon, but also to structural defects such as

dangling bonds. The impurities may generally be removed using a variety of puri-

ﬁ cation techniques, including: the oxidation of contaminants [24] ; ﬂ occulation and

selective sedimentation [25] ; ﬁ ltration [26] ; size - exclusion chromatography [27] ;

selective interaction with organic polymers [28] ; and microwave irradiation [29] .

Despite such a variety of techniques, each has been shown to have its own limita-

tions, such that problems persist in the puriﬁ cation of CNTs.

As CNTs can be synthesized with extreme aspect ratios (i.e., length - to - diameter

ratios), they are particularly appropriate for applications in electronics and semi-

7.3 Carbon Nanotubes 253

conductor devices. The inherent size, hollow geometry and extraordinary elec-

tronic properties of CNTs make them promising building blocks for molecular

or nanoscale devices. Further, the well - deﬁ ned geometry, exceptional mechanical

properties and remarkable electrical characteristics, in addition to their outstand-

ing physical properties [10] (see Table 7.1 ), qualify them for potential applications

[30] in nanoelectronic circuits, ﬁ eld emitters, nanoelectronic devices, nanotube

aquators, batteries, probe tips for scanning probe microscopy, nanotube -

reinforced materials, nanoelectromechanical system s ( NEMS ), and nanorobotic

systems [31] .

Table 7.1 Important properties of CNT s .

Property Item Data Potential application

Geometric Layers Single/multiple Structures, probes,

grippers/tweezers,

scissors

Aspect ratio 10 – 1000

Diameter

∼ 0.4 – 3 nm (SWNTs)

∼ 1.4 – 100 nm (MWNTs)

Length Several μ m to mm

Mechanical Young ’ s modulus

∼ 1 TPa (steel: 0.2 TPa)

Tensile strength 45 GPa (steel: 2 GPa)

Density

∼ 1.33 – 1.4 g cm

− 3

(Al: 2.7 g cm

− 3

)

Interlayer friction Ultra - small Actuators, bearings,

syringes, switches,

memories

Electronic Conductivity Metallic/

semi - conducting

Diodes, transistors,

switches, logic gates

Current carrying

capacity

∼ 1 TA cm

− 3

(Cu: 1 GA cm

− 3

)

Wires/cables

Field emission Activate phosphorus at

∼ 1 – 3 V

Proximity/position

sensors

Band gap

Eg (eV) ≈ 1 d

− 1

(nm)

Electron transport Ballistic, no scattering

Maximum current

density

10

A cm

− 2

Electromechanical Piezoresistivity Positive/negative Deformation/

displacement sensors

Thermal Heat transmission > 3 kW mK

− 1

(Diamond: 2 kW mK

− 1

)

Circuits, sensors,

thermal actuators

TPa, Tera - Pascal; GPa, Giga - Pascal; TA, Tera - Ampere; GA, Giga - Ampere.

254 7 Gold Nanoparticles and Carbon Nanotubes: Precursors for Novel Composite Materials

7.4

CNT – Metal Nanoparticle Composites

In nanocomposites, different materials such as metal nanoparticles, CNTs and

clay may be combined with another material, usually a polymer. Nanocomposites

have recently attracted considerable interest in both academic and industrial ﬁ elds

due to their unique mechanical, thermal and electronic properties. Nanoscaled

particulates such as CNTs have been investigated as ﬁ llers in a variety of polymeric

matrices to produce enhanced properties. Because of their exceptionally small

diameters (several nm), as well as their high Young ’ s modulus ( ∼ 1 TPa), tensile

strength ( ∼ 200 GPa) and high elongation (10 – 30%), in addition to a high chemical

stability, CNTs represent attractive reinforcement materials for lightweight and

high - strength metal matrix composites. Metallic composites (especially with noble

metals) containing CNTs would offer distinct advantages over polymeric compos-

ites. However, the development of metal matrix composites remains in its infancy,

despite its great potential, primarily because of the high fabrication costs involved

and difﬁ culties in scaling - up the production process.

It has been predicted, based on computer stimulations, that open nanotubes

may be ﬁ lled with liquid by capillary suction [32] . This has provided much specula-

tion that the ﬁ lling of extraneous materials into the hollow nanotube cavities might

have interesting effects on the physical and electronic properties of the encapsu-

lated materials. The modiﬁ cation of CNTs into composite nanoﬁ bers by ﬁ lling

them with molten materials through capillary action has been reported [33, 34] ,

and subsequently metal carbides have been entrapped into the hollow cavities of

CNTs by using an arc discharge method [35, 36] . In contrast, in 1994 Ajayan and

coworkers [37] reported for the ﬁ rst time that a combination of CNTs and metal

nanoparticles could also be achieved by depositing the metal cluster on the surface

(outside the tube) of the CNTs; this was termed the “ decoration ” of CNTs with

metal clusters. The method involved the use of SWNTs as a support material for

dispersing ruthenium nanoparticles that would then serve as a catalyst in hetero-

geneous catalysis. As a result, ∼ 0.2% (w/w) of Ru nanoparticles were deposited on

the surface of the CNTs. Following these successes, a variety of hybrid composites

was introduced and developed with either metal or metal oxide or semiconductor

nanoparticles. It is envisaged that these composite materials might ﬁ nd practical

uses as nanowires and novel catalysts.

The combination of metal nanoparticles (notably AuNPs) and CNTs may lead

to the development of a new class of nanocomposite materials, and lead in turn

to the successful integration of the properties of these two components in

new hybrid materials that present signiﬁ cant features for catalysis and nanotech-

nology. The combination of two classes of novel material may be obtained as

either particles coated on the surface of the CNTs (exohedral), or encapsulated

in the nanotube cavity (endohedral). Here, the CNT surface acts as a template

where nanoparticles (either naked or stabilized by protecting agents) are absorbed

or, in the case of a functionalized CNT, the nanoparticles may be linked through

a functional group of the organic moieties attached to the CNTs. This new type

Geckeler K.E., Nishide H. (Eds.) Advanced Nanomaterials

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