Single point electrodeposition of nickel for the dissymmetric decoration of carbon tubes

Dissymmetric micro- and nanoobjects are of enormous interest in many areas ranging from molecular electronics to targeted drug delivery. So far it has been quite difficult to synthesize dissymmetric objects at these scales and most approaches are based on using interfaces to break the symmetry. Only a few bulk procedures are known so far to produce the so-called Janus-type objects. We report here a simple approach for the bulk generation of dissymmetric micro- and nanoobjects, especially carbon tubes (CTs), based on a known, but so far underestimated electrochemical principle, namely bipolar electrodeposition. A suspension of CTs is introduced in a capillary containing an aqueous nickel salt solution and a high electric field is applied to orientate and polarize the individual tubes. During their transport through the capillary under sufficient polarization, each tube is the site of water oxidation at one end, and of Ni²⁺ reduction at the other one. The resulting nickel deposit at one end of the tube allows manipulation of the objects with the help of a magnetic field.