Langmuir 2002, 18, 8655-8659
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New Approach to the Assembly of Gold Nanoparticles: Formation of Stable Gold Nanoparticle Ensemble with Chainlike Structures by Chemical Oxidation in Solution Tongxin Wang, Deqing Zhang,* Wei Xu, Shuhong Li, and Daoben Zhu* Organic Solids Laboratory, Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China Received March 11, 2002. In Final Form: July 9, 2002 By reducing the pyrrole contents on their surfaces, gold nanoparticles (capped by alkanethiolates and thiolates with pyrrole units) were cross-linked covalently by chemical oxidation into a stable nanoparticle ensemble with chainlike structures. This new and convenient assembly method for gold nanoparticles may be also applied to other functional nanoparticles (e.g., CdS, “core-shell” Co/Pt, and Fe/Au).
Introduction Nanoparticles are attracting much attention due to their fundamental importance and potential applications in optics, electronics, catalysis, etc.1 Apart from the studies of discrete nanoparticles, it is also very important to fabricate nanoparticles into one-, two-, and threedimensional ordered structures since the collective properties of the resulting structures are expected to be different from those of the corresponding isolated nanoparticles.2 Until now, various strategies have been developed to form ordered nanoparticle arrays. They include controlled solvent evaporation,3 Langmuir-Blodgett technique,4 electrostatic attraction,5 hydrogen bonding,6 π-π stacking,7 DNA-driven assembly,8 and cross-linking induced by bifunctional molecules such as dithiol.9 Another potential approach to assemble nanoparticles is to cross-link them covalently by taking advantage of chemical reactions of terminal functional groups of thiolates adsorbed on the surfaces of nanoparticle.10 For instance, Murray et al. described the “ligand/metal ion/ ligand linker” approach for the assembly of nanoparticles.11 It is well-known that pyrrole can be polymerized easily to form polypyrrole by either chemical or electrochemical methods. Thus, it is probable that nanoparticles protected by thiolates containing pyrrole units can be cross-linked to generate a structurally interesting assembly of nanoparticles in the presence of chemical oxidants such as FeCl3. It should be mentioned at this point that the present approach is different from that detailed by Feldheim et * Corresponding authors. Fax: 0086 10 62559373. E-mail:
[email protected] (D.Z.). (1) (a) Stucky, G. D.; Mcdougall, J. E. Science 1990, 247, 669. (b) Alivisatos, A. P. Science 1996, 271, 933. (c) Roychowdhory, V. P.; Janes, D. B.; Bandyopadhyay, S.; Wang, X. IEEE Trans. Electron. Devices 1996, 43, 1688. (2) (a) Xia, Y.; Rogers, J. A.; Paul, K. E.; Whitesides, G. M. Chem. Rev. 1999, 99, 1823. (b) Li, M.; Schnablegger, H.; Mann, S. Nature 1999, 402, 393. (c) Caruso, F. Adv. Mater. 2001, 13, 11. (3) Murray, C. B.; Kagan, C. R.; Bawendi, M. G. Science 1995, 270, 1335. (4) (a) Chen, S. Langmuir 2001, 17, 2878. (b) Mendrum, F. C.; Kotov, N. A.; Fendler, J. H. Langmuir 1994, 10, 2035. (c) Leibowwitz, F. L.; Zheng, W.; Maye, M. M.; Zhong, C. Anal. Chem. 1999, 71, 5076. (5) (a) Shipway, A. N.; Lahav, M.; Gabai, R.; Willner, I. Langmuir 2000, 16, 8789. (b) Willner, I.; Katz, E. Angew. Chem., Int. Ed. 2000, 39, 1180. (c) Lahav, M.; Gabriel, T.; Shipway, A. N.; Willner, I. J. Am. Chem. Soc. 1999, 121, 258. (6) (a) Boal, A. K.; IIhan, F.; DeRouchey, J. E.; Thurn-Albrecht, T.; Rotello, V. M. Nature 2000, 404, 746. (b) Boal, A. K.; Rotello, V. M. J. Am. Chem. Soc. 1999, 121, 4914. (c) Boal, A. K.; Rotello, V. M. Langmuir 2000, 16, 9527. (d) Chen, S.; Kimura, K. Langmuir 1999, 15, 1075.
al.,12 in which they described ordered structures of gold nanoparticles with polypyrrole that was formed on the surfaces of nanoparticles within Al2O3 pores. We have previously reported that chemical oxidation of gold nanoparticles protected by entire thiolates with pyrrole units led to the nanoparticle assembly with diffuse and disordered structure,13 probably due to the fast multiscale cross-connection of pyrrole units. It is expected that the cross-linking of gold nanoparticles with this method can be controlled by reducing the pyrrole contents on the surfaces of gold nanoparticles. That is, the oxidation was performed with gold nanoparticles protected by both thiols with pyrrole moieties as terminal groups and alkanethiols, instead of gold nanoparticles capped by entire thiolates containing pyrrole units. Herein we report the assembly of gold nanoparticles (capped by alkanethiolates and thiolates with pyrrole units) into chainlike structures by chemical oxidation in solution. The effect of the contents of pyrrole units (adsorbed on the surfaces of (7) (a) Jin, J.; Iyoda, T.; Cao, C.; Song, Y.; Jiang, L.; Li, T.; Zhu, D. Angew. Chem., Int. Ed. 2001, 40, 2135. (b) Teranishi, T.; Haga, M.; Shiozawa, Y.; Miyake, M. J. Am. Chem. Soc. 2000, 122, 4237. (8) (a) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (b) Alivisatos, A. P.; Johnsson, K. P.; Peng, X.; Wilson, T. E.; Loweth, C. J.; Bruchez, M. P.; Schultz, P. G. Nature 1996, 382, 609. (c) Storhoff, J. J.; Mirkin, C. A. Chem. Rev. 1999, 99, 1849, and further references therein. (d) Taton, T. A.; Mucic, R. C.; Mirkin, C. A.; Letsinger, R. L. J. Am. Chem. Soc. 2000, 122, 6305. (e) Loweth, C. J.; Caldwell, W. B.; Peng, X.; Alivisatos, A. P.; Schultz, P. G. Angew. Chem., Int. Ed. 1999, 38, 1808. (f) Park, S.; Lazarides, A. A.; Mirkin, C. A.; Brazis, P. W.; Kannewurf, C. R.; Letsinger, R. L. Angew. Chem., Int. Ed. 2000, 39, 3845. (g) Park, S.; Lazarides, A. A.; Mirkin, C. A.; Letsinger, R. L. Angew. Chem., Int. Ed. 2001, 40, 2909. (h) Cao, Y.; Jin, R.; Mirkin, C. A. J. Am. Chem. Soc. 2001, 123, 7961. (9) (a) Brust, M.; Bethell, D.; Schiffrin, D. J.; Kiely, C. J. Adv. Mater. 1995, 7, 795. (b) Andres, R. P.; Bielefeld, J. D.; Henderson, J. I.; Janes, D. B.; Kolagunt, V. R.; Kubiak, C. B.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690. (c) Chen, S. Adv. Mater. 2000, 12, 186. (10) Templeton, A. C.; Hostetler, M. J.; Kraft, C. T.; Murray, R. W. J. Am. Chem. Soc. 1998, 120, 1906. (11) (a) Zamborini, F. P.; Hicks, J. F.; Murray, R. W. J. Am. Chem. Soc. 2000, 122, 4514. (b) Templeton, A. C.; Zamborini, F. P.; Wuelfing, W. P.; Murray, R. W. Langmuir 2000, 16, 6682. (c) Wuelfing, W. P.; Zamborini, F. P.; Templeton, A. C.; Wen, X.; Yoon, H.; Murray, R. W. Chem. Mater. 2001, 13, 87. (12) (a) Marinakos, S. M.; Brousseau, L. C.; Jones, A.; Feldheim, D. L. Chem. Mater. 1998, 10, 1214. (b) Marinakos, S. M.; Shultz, D. A.; Feldheim, D. L. Adv. Mater. 1999, 11, 34. (c) Marinakos, S. M.; Novak, J. P.; Brousseau, L. C.; House, A. B.; Edeki, E. M.; Feldhaus, J. C.; Feldheim, D. L. J. Am. Chem. Soc. 1999, 121, 8518. (13) Xu, W.; Liu, W.; Zhang, D.; Xu, Y.; Wang, T.; Zhu, D. Colloids Surf., A 2002, 204, 201.
10.1021/la025717+ CCC: $22.00 © 2002 American Chemical Society Published on Web 10/02/2002
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Wang et al.
Table 1. Preparation and Characterization Data for Gold (I + II) Nanoparticles elemental analysis (%) particle
feed ratio (PySH/C8SH)
A B C D E F G
Py 6/1 2/1 1/1 1/10 1/30 1/60
product
ratioa
12.8/1 3.6/1 2.2/1 1/5.1 1/14.1 1/24.3
C
H
N
average sizeb (nm)
compositionc
14.15 13.83 11.87 12.55 12.71 8.38 10.55
2.22 1.87 1.69 1.74 1.85 1.30 1.85
0.57 0.77 0.36 0.59
