Attachment of gold nanoparticles on indium tin oxide for tuning nanostructured electrode interfaces

Munetaka Oyama ,  Akiko Orimo ,  Shin-ichi Fujita 

Kyoto University, Graduate School of Engineering, Nishikyo-ku, Kyoto 615-8520, Japan

Abstract
     The attachment of gold nanoparticles (AuNPs) on indium tin oxide (ITO) electrodes permits their electroanalytical applications because of the electrocatalytic ability and bio-compatibility of AuNPs.   In recent years, we have been studying the fabrications of AuNP-attached ITO electrodes using a seed-mediated growth method, which was originally developed for the preparation of gold nanorods.  In addition to the easiness of the wet chemical preparation at room temperature, with the seed-mediated growth method, it was a success that the charge transfer resistance can be reduced for thus fabricated AuNP-attached ITO electrodes, and also they are applicable to the attachment of hemeproteins.  However, there is a difficulty in controlling the density of the attached AuNPs, though we tried several modified  approaches in the seeding and the growth processes.  

     In the present work, for the purpose of the denser attachment of AuNPs on ITO electrodes, we tried to perform the nanostructuring of AuNPs on the ITO surfaces using linker molecules.  In addition to the well-know linker molecules, 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminoptopropyltrimethoxysilane (APTMS), we used cysteamine because it is known that the linkage is possible via the bonding of S with the ITO surfaces.  Systematic comparisons of the attached nanostructures of AuNPs on ITO were carried out after the room temperature treatment of the ITO surafaces in ethanoholic linker solutions followed by the room tenperature attachemnet of  AuNPs using (i) one-step immersion into the 20-nm Au colloidal solution (Sigma) or (ii) two-step immersion, i.e., seed-mediated growth treatment. 

     Consequently, in the case (i), it was found that APTMS was suitable for the denser and homogeneous attachment of AuNPs on ITO surfaces keepin a dispersed state.    In contrast, in the case (ii), the nanostructuring of AuNPs were possible with MPTMS and cysyeamine using the seed mediated growth, while the growth of AuNPs were quite smaller with the APTMS linker.

     The differences of the attachment characteristics of AuNPs depending on the size were also observed.  As the results, it was found that smaller AuNPs attached dominantly on the surface of ITO.  The results of the competitive attachments of 5, 10, 20 nm AuNPs are presented. 

 

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Presentation: Keynote lecture at SMCBS'2009 International Workshop, by Munetaka Oyama
See On-line Journal of SMCBS'2009 International Workshop

Submitted: 2009-08-29 04:33
Revised:   2009-08-29 05:51