Langmuir-Blodgett films of thiol-capped gold nanoclusters: fabrication and electrical properties

Surface-modified nanoparticles are increasingly studied for their potential applications in the field of information processing. Here the Langmuir-Blodgett technique is used to prepare monolayers of dodecanethiol-capped gold nanoparticles (2.9 nm diameter) over macroscopic dimensions. Combining optical microscopy on the Langmuir film and scanning force microscopy (SFM) on transferred films, it is shown that the quality of the films is optimized in the 6-8 mN/m range. The dodecanethiol is displaced in situ by dipping the film in a solution of 2,5 "-bis(acetylthio)-5,2',5',2 "-terthienyl (T3) which interconnects the clusters. After dipping in the T3 solution, the conductivity of the monolayer increases up to 10(-3) Ohm(-1)/cm. The non-linear I-V characteristics measured on interdigitated electrodes and the non-linear scanning tunnelling spectroscopy (STS) I-V curves are tentatively explained within the frame of the Coulomb blockade theory. (C) 1998 Elsevier Science S.A. All rights reserved.