NANO LETTERS
Self-Assembled Gold Nanoparticle/ Dendrimer Composite Films for Vapor Sensing Applications
2002 Vol. 2, No. 5 551-555
Nadejda Krasteva,† Isabelle Besnard,† Berit Guse,† Roland E. Bauer,‡ Klaus Mu1 llen,‡ Akio Yasuda,† and Tobias Vossmeyer*,† Materials Science Laboratories, AdVanced Technology Center Stuttgart, Sony International (Europe) GmbH, Heinrich-Hertz-Strasse 1, D-70327 Stuttgart, Germany, and Max-Planck-Institut fu¨ r Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany Received March 7, 2002; Revised Manuscript Received March 26, 2002
ABSTRACT Vapor-sensitive thin-film resistors comprising gold nanoparticles and different types of organic dendrimers (polyphenylene, poly(propylene imine) and poly(amidoamine)) were prepared via layer-by-layer self-assembly and characterized by UV/vis spectroscopy, atomic force microscopy, and conductivity measurements. While the metal nanoparticles were utilized to provide the film material with electric conductivity, the dendrimers served to cross-link the nanoparticles and to provide sites for the selective sorption of analyte molecules. Dosing the films with vapors of toluene, 1-propanol, and water significantly increased the film resistances. The chemical selectivity of this response was controlled by the solubility properties of the dendrimers.
During the past few years, self-assembled multilayered films of organically encapsulated metal nanoparticles have gained considerable attention due to their unique optical and electronic properties.1-6 Nanoparticle-based composite materials have potential applications in nanoelectronic and optoelectronic devices,7,8 chemical sensing,9-14 and catalysis.15,16 An intriguing feature of these materials is the possibility to tune their properties through a molecular level design by varying the material or the size of the particle core, or the composition of the organic shell. Following the solution phase synthesis of alkanethiol-stabilized Au-nanoparticles, which was introduced by Brust and co-workers,17 numerous reports described the use of organic thiols for constructing the organic shell of metal nanoparticles. More recently, the use of organic dendrimers as ligands for producing core-shell Au-nanoparticles has been reported.18-21 Dendrimers are globular molecules with well-defined size and structure, which can contain a great number of intramolecular and terminal functional groups. Such groups have been shown to act as endo- and exo-receptors for binding small size molecules or ions.21-23 This feature makes dendrimers especially interesting for the preparation of thin sensor films. High sensitivity and chemical selectivity of such films can be achieved by modifying the internal and/or * Corresponding author. E-mail:
[email protected]. † Sony International (Europe) GmbH. ‡ Max-Planck-Institut fu ¨ r Polymerforschung. 10.1021/nl020242s CCC: $22.00 Published on Web 04/18/2002
© 2002 American Chemical Society
peripheral functionalities and structural features of the dendrimer molecules.24-26 In a previous paper we described the preparation and sensing properties of composite films made from Aunanoparticles and disulfide-functionalized polyphenylene (PPh) dendrimers.27 When such films were used as chemiresistors, they responded very sensitively and quickly to the exposure with organic solvent vapors (detection limit for toluene: PPI > PAMAM), the sensitivity to toluene vapor decreased, whereas the relative response to 1-propanol and water vapor was enhanced. Currently, we are investigating how structural details of the dendrimer molecules determine the sensor characteristics by systematically varying the dendrimer structure. These investigations also include a detailed analysis of sorption and diffusion processes within the composite film materials, which will be published elsewhere. Acknowledgment. We thank Dr. N. Matsuzawa, Dr. Y. Joseph, and M. Rosenberger (Sony International (Europe) GmbH, Materials Science Laboratories) for the helpful discussions and the technical support. This project was partly supported by the BMBF, FKZ 03C0302A and FKZ 03C0299. Supporting Information Available: Experimental details on the nanoparticle synthesis, film preparation, and measurement setups, as well as data from UV/vis, electron transport, and vapor dosing experiments are presented in the Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org. References (1) Brust, M.; Bethel, D.; Kiely, C. J.; Schiffrin, D. J. Langmuir 1998, 14, 5425. (2) Musick, M. D.; Keating C. D.; Keefe, M. H.; Natan, M. J. Chem. Mater. 1997, 9, 1499. (3) Musick, M. D.; Keating C. D.; Lyon, L. A.; Botsko, S. L.; Pena, D. J.; Holliway, W. D.; McElvoy, T. M.; Richardson, J. N.; Natan, M. J. Chem. Mater. 2000, 12, 2869. (4) Fishelson, N.; Shkrob, I.; Lev, O.; Gun, J.; Modestov, A. D. Langmuir 2001, 17, 403. (5) Andres, R. P.; Bielefeld, J. D.; Henderson, J. I.; Janes, D. B.; Kolagunta, V. R.; Kiubiak, C. P.; Mahoney, W. J.; Osifchin, R. G. Science 1996, 273, 1690.
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