Green plating of high aspect ratio gold nanotubes and their morphology-dependent performance in enzyme-free peroxide sensing

The development of a green electroless plating protocol allowing the homogeneous deposition of nanoscale gold films on complex shaped substrates is presented. It is based on the environmentally benign reducing agent ascorbic acid and was used for the fabrication of gold nanotubes in porous polymer templates. The key action to achieve well-defined nanotubes of high aspect ratio (>100) was to reduce the reaction rate in order to ensure homogeneous metal deposition within the extended inner surface of the template. Depending on the plating time, nanotubes with porous as well as closed walls could be synthesized, which were characterized by SEM and EDX. Both nanostructure types were successfully implemented in the amperometric detection of hydrogen peroxide. The generally improved performance of the porous nanotubes compared to their closed counterparts was attributed to their better accessible and higher surface area (limit of detection: 2.3 mu M vs. 8.2 mu M; maximum of linear range: 11.7 mM vs. 8.0 mM; response time: 3.6 s vs. 5.5 s; sensitivity: 770 mu A mM cm(-2) vs. 360 mu A mM cm(-2)). These excellent performance parameters surpass comparable, conventionally synthesized Au nanotube arrays as well as enzyme-modified one-dimensional Au catalysts, proving the high potential of adapted electroless plating reactions for green nanotechnology.