In bipolar electrochemistry (BPE), faradaic reactions are driven on conducting particles not directly connected to an electrical power source, but immersed in a dielectric (solution) polarized by an applied electric field. Examples of use of BPE for controlling asymmetrical depositions on metal particles have been widely reported, while, few or no study dealt with BPE deposition on semiconductor nanoparticles. In a BPE experiment on a semiconductor in the dark, the holes concentration at the anodic side is so low that the oxidation occurs at a negligible rate so hindering also the associated cathodic process. The situation changes when BPE is performed under UV-light irradiation, so that the electrons are promoted to the conduction band, triggering the occurrence of oxidation and reduction reactions at the two opposite sides of the particle. In this work, these principles are used to control deposition processes onto the tips of TiO2 nanowires (TiO2-NWs). We demonstrate here that, when BPE is performed in the dark on TiO2-NWs in Au(III) solutions, no gold deposit is formed. When the NWs suspension is irradiated with UV light in the absence of an electric field, small metallic deposits, randomly located all over the particles are formed. Finally, when both UV light and electric field are applied, a metallic deposits is formed, but in a precise position of the NW, that is at its cathodic tip. These results indicate that the application of the external electric field allows one to drive locally the action of the light thus achieving the localized asymmetrical modification of the TiO2-NWs. The technique is applied to drive the deposition of different metals and/or conducting polymers at one or at the two opposite tips of TiO2-NWs. Relevant results and prospects are presented and discussed.

Janus-like deposits on TiO<sub>2</sub> nanowires by the combined action of bipolar-electrochemistry and light

247th National Meeting (2014)

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Janus-like deposits on TiO2 nanowires by the combined action of bipolar-electrochemistry and light

Janus-like deposits on TiO₂ nanowires by the combined action of bipolar-electrochemistry and light