Nanopores offer defined high rate of mass transport that can be controlled by modifying the geometry and the materials that compose the pores. If the nanopores are modified to incorporate a new material, a change in solution resistance inside the pores will be observed. This change can be used to study the properties of a material, for example its charge, surface area and reactivity. However, precisely controlling the deposition of a material inside such tiny volumes is a challenge. Moreover, it is frequently desired to deposit the material at a specific location within the pore, for example on the inside wall or just at the opening. When the material requires to be electrodeposited, achievement of such site specificity is difficult as it necessitates a continuous electrical contact that is exposed only at the desired sites. Bipolar electrochemistry is a powerful tool capable of localized electrodeposition on nanoscale electrodes in the absence of an electrical contact. In our work, two electrodes are placed on either side of a gold nanotube membrane and a potential bias is applied (1-4 V). The gold nanotubes act as bipolar electrodes due to the large potential drop across the membrane. Redox reactions, one cathodic and one anodic, occur at both ends of the nanotubes. One reaction is chosen such that it forms manganese dioxide which is selectively electrodeposited at one pore orifice (Figure 1). Manganese oxides are interesting materials for sensing, catalysis, supercapacitor and battery applications. Their well-defined porous structures exhibit high specific surface areas and lattices that allow the intercalation of ions, such as lithium. In this talk, we report on the mechanism of formation and growth rate of these MnO2 caps on gold nanopores as studied by electrochemistry and complementary techniques. We also report electrochemical measurements of the synthesized material, including its permselectivity towards lithium ions.

Gold nanotubes as bipolar electrodes for the deposition and study of manganese dioxide

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.