Understanding and directing electrochemical reactions below the micrometer is a long-standing challenge in electrochemistry. Conning reactions to nanoscale areas paradoxically requires both isolation and communication with the bulk electrolyte in terms of potential and access of ions, respectively. Here, we demonstrate the directed electrochemical deposition of copper nanostructures by using an oscillating nanoelectrode operated with an atomic force microscope (AFM). Strikingly, the writing is only possible in highly dilute electrolytes and for a particular combination of AFM and electrochemical parameters. We propose a mechanism based on cyclic charging and discharging of the electrical double layer (EDL). The extended screening length and slower charge dynamics in dilute electrolytes allows the nanoelectrode to operate inside, and disturb, the EDL even for large oscillation amplitudes (~100 nm). Our unique approach can not only be used for controlled additive nano-fabrication but also provides insights into ion behavior and EDL dynamics at the solid-liquid interface.

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Wed, December 11 2019 at 00:00 (CET)