Development of an electroactive layer-by-layer assembly based on host–guest supramolecular interactions Flavio S. Damos a,b,d , Rita C.S. Luz a,b,d , Auro A. Tanaka c,d , Lauro T. Kubota a,d, * a Institute of Chemistry, UNICAMP, P.O. Box 6154, 13084-971 Campinas, SP, Brazil b Department of Chemistry, UFVJM, 391000-000 Diamantina, MG, Brazil c Department of Chemistry, UFMA, 65085-040 São Luis, MA, Brazil d Instituto Nacional de Ciência e Tecnologia de Bioanalítica, UNICAMP, P.O. Box 6154, 13084-971 Campinas, SP, Brazil article info Article history: Received 26 August 2009 Received in revised form 28 October 2009 Accepted 3 November 2009 Available online 06 November 2009 Keywords: Electrochemical properties Layer-by-layer assembly Host–guest interface Supramolecular interaction Multivalent interface abstract The development of a novel electrochemically stable host–guest supramolecular complex at a host sur- face is described. It was constructed by combining a self-assembled monolayer (SAM) of mono-(6-deoxy- 6-mercapto)-b-cyclodextrin (bCDSH), iron (III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeTMPyP) as the guest-link-molecule and b-cyclodextrin-functionalized gold nanoparticles (bCDAuNP). The building pro- cess of the layer-by-layer assembly was monitored by surface plasmon resonance spectroscopy (SPR). The binding processes between the host-functionalized gold surface and the linker molecule (FeTMPyP) were verified to be monovalent, and for host-functionalized gold nanoparticles with FeTMPyP, the interaction was determined to be bivalent. Finally, the electrochemical properties of the electroactive supramolecu- lar multivalent film were determined. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction The design and development of self-assembled monolayers (SAM) of thiol-based electrode surfaces have been interesting sub- jects of research in recent years [1]. One of the most attractive applications of these surfaces is their utilization as an electrocata- lyst model due to the strong correlation between the surface struc- ture and electrocatalytic activity. Among the possible candidates for the electrocatalytic active center, porphyrin is very attractive due to its well-known functions in biological and biomimetic sys- tems [2]. From a structural point of view, porphyrin is of particular inter- est since the orientation of its ring can be controlled. For example, perpendicularly and coplanarly oriented porphyrin monolayers can be obtained using monothiolated and multithiolated porphy- rins, respectively [3]. However, the direct immobilization of thiol-terminated metalloporphyrin might have some disadvan- tages. It has been reported that the thiol can coordinate to the cen- tral metal ion of the porphyrin, resulting in a multilayer formation and blocking the catalytic center. To overcome this problem, assembly strategies based on nanomaterials could be used, allow- ing for a high level of control of the system [4]. Currently, use of nanostructured materials for the generation of functional molecular assemblies is an important line of research in nanotechnology. Methods for integrating molecular components into well-ordered assemblies and well-defined supramolecular architectures are prerequisites for the construction of functional molecule-based devices [5]. Many supramolecular systems have been previously studied, mainly consisting of organized monomolecular films on surfaces. The extension of the supramolecular approach to multilayer film has recently been shown to enhance the properties of monomolec- ular films and, at the same time, create a new class of materials presenting functional groups at controlled sites in three-dimen- sional arrangements [6]. Alternating layer-by-layer (LBL) assembly is one method used to prepare nanolayered structures on solid substrates. This method al- lows for the construction of a film on a substrate of any composition or topology by alternating its exposure to solutions containing spe- cies with complementary affinities. LBL assembly has been achieved by exploiting attractive forces and alternating immersions. The method, initially developed to prepare electrostatically multilayer assemblies, has been successfully extended to various other driving forces such as hydrogen bonding [7], charge transfer [8], acid–base pairs [9], inter- or intramolecular interactions [10], covalent bonds [11], biospecific interactions [12], recently, host–guest interactions 0022-0728/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jelechem.2009.11.008 * Corresponding author. Address: Institute of Chemistry, UNICAMP, P.O. Box 6154, 13084-971 Campinas, SP, Brazil. Tel.: +55 19 3521 3127; fax: +55 19 3521 3023. E-mail address: kubota@iqm.unicamp.br (L.T. Kubota). Journal of Electroanalytical Chemistry 639 (2010) 36–42 Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem