Potential-dependent restructuring and chemical noise at Au-Ag-Au atomic scale junctions

Science and technology of electrochemistry at nano-interfaces: concluding remarks

The Faraday Discussion on electrochemistry at nano-interfaces presented a platform for an incredibly diverse array of advances in electrochemical nanoscience and nanotechnology. In this summary, I have identified the factors which drive the development of the science and which ultimately support many impressive technological advances described. Prime among these are the emergence of new physical behaviors when device dimensions approach characteristic physical scaling lengths, the steadily increasing importance of surfaces as device dimensions shrink, and the capacity to fabricate and utilize structures which are commensurate in size with molecules, especially biomolecules and biomolecular complexes. In this Faraday Discussion we were treated to outstanding examples of each of these nanoscience drivers to produce new, and in many cases unexpected, electrochemical phenomena that would not be observed at larger scales. The main thrust of these collective activities has been to realize the promise implicit in several transformational experiments that were carried out in the last decades of the 20th century. Our task is not complete, and we can look forward to many additional developments springing from the same intellectual wellhead.

Direct-Write Formation and Dissolution of Silver Nanofilaments in Ionic Liquid-Polymer Electrolyte Composites

Materials with reconfigurable optical properties are candidates for applications such as optical cloaking and wearable sensors. One approach to fabricate these materials is to use external fields to form and dissolve nanoscale conductive channels in well-defined locations within a polymer. In this study, conductive atomic force microscopy is used to electrochemically form and dissolve nanoscale conductive filaments at spatially distinct points in a polyethylene glycol diacrylate (PEGDA)-based electrolyte blended with varying amounts of ionic liquid (IL) and silver salt. The fastest filament formation and dissolution times are detected in a PEGDA/IL composite that has the largest modulus (several GPa) and the highest polymer crystal fraction. This is unexpected because filament formation and dissolution events are controlled by ion transport, which is typically faster within amorphous regions where polymer mobility is high. Filament kinetics in primarily amorphous and crystalline regions are measured, and two different mechanisms are observed. The formation time distributions show a power-law dependence in the crystalline regions, attributable to hopping-based ion transport, while amorphous regions show a normal distribution. The results indicate that the timescale of filament formation/dissolution is determined by local structure, and suggest that structure could be used to tune the optical properties of the film.

Copper Nanowires through Oriented Mesoporous Silica: A Step towards Protected and Parallel Atomic Switches

The formation of copper atomic contacts has been investigated. Copper nanowires were grown by electrochemical deposition, in the scanning electrochemical microscopy (SECM) configuration, from a platinum microelectrode to an indium tin oxide (ITO) substrate. Self-termination leaves copper filaments between the two electrodes with an atomic point contact at the ITO electrode. Histogram analysis shows that the conductance of this contact is close to, or less than, 1 G0. Atomic contacts were also fabricated on ITO electrodes covered with vertically-aligned mesoporous silica films. Scanning Transmission Electron Microscopy images show that copper filaments occupy individual isolated nanopores. Contacts generated on bare ITO break down rapidly in sodium salicylate, whereas those generated in ITO/nanopores are unaffected; the nanopores protect the copper filaments. Finally, atomic switch behaviour was obtained using these ITO and ITO/nanopores electrodes.