Factors controlling the electrodeposition of metal nanoparticles on pristine single walled carbon nanotubes.

The electrodeposition of metal (Pd and Pt) nanoparticles on networks of pristine single walled carbon nanotubes (SWNTs) has been investigated using a microelectrochemical cell. A microcapillary containing electrolyte solution and a reference electrode is contacted with a silicon oxide substrate bearing a SWNT network, connected as the working electrode. Electrodeposition is promoted by applying a potential between the SWNT network and the reference electrode. By combination of analysis of the resulting current-time curves with atomic force microscopy and field emission scanning electron microscopy imaging of the network surfaces after electrodeposition, the nature of metal nanoparticle formation on SWNTs has been elucidated. In particular, the parameters controlling nanoparticle number density, distribution, and size have been identified, with short deposition times and high driving forces favoring the formation of ultrasmall particles at high density. Capacitance and network resistance effects are minimized in the microcapillary configuration, making it possible to accurately analyze short time-scale deposition processes (millisecond time scale). Furthermore, it is also possible to make many measurements on a pristine sample, simply by moving the position of the microcapillary to a new location on the substrate.