Dealloying progress during nanoporous structure evolution analyzed by in situ resistometry

Abstract

The progress of dealloying, an electrochemical synthesis method capable of producing nanoporous structures with bulk outer dimensions, is studied by in situ resistometry. The resistance increases by three orders of magnitude while nanoporous gold or platinum is formed. Simultaneous monitoring of charge flow and electrical resistance increase proves to be an ideal combination for analyzing the etching progress, which in accordance with recent studies can be demonstrated to occur in two steps referred to as 'primary (or bulk) dealloying' and 'secondary (or ligament) dealloying'. A model is developed, which describes the resistance increase during etching as governed by the reduction of the master alloy backbone in favor of the nanoporous structure. This new approach allows an evaluation of the etching front propagation (primary dealloying) as well as the status of the already porous structure (secondary dealloying).

Enhanced Charging-Induced Resistance Variations of Nanoporous Gold by Dealloying in Neutral Silver Nitrate Solution

“…Due to porosity evolution and the concomitant formation of a strongly bound oxide during dealloying the electrical resistance of nanoporous metals increases by about 3 orders of magnitude compared to the initial resistance of the master alloy . This so-called ’primary oxide’ condition is associated with peculiar physical properties regarding the electrical resistance , as well as actuation .…”

“…Due to porosity evolution and the concomitant formation of a strongly bound oxide during dealloying the electrical resistance of nanoporous metals increases by about 3 orders of magnitude compared to the initial resistance of the master alloy. 31 This so-called 'primary oxide' condition is associated with peculiar physical properties regarding the electrical resistance 25,26 as well as actuation. 29 Therefore, in order to observe a metallic behavior of the np-Au material, the sample platelet was carefully reduced by cyclic voltammetry (CV) in 1 M KOH solution between potentials U Ag/AgCl of −400 mV and +800 mV with a scan rate of 1 mV/s prior to any resistance tuning experiments, which is shown in Figure 2.…”

Electrochemical switching of positronium triplet quenching

“…The backside of the contacted AuAg alloy was subsequently embedded in Thermokitt (Carl Roth) and dried at room temperature and 250 1C in air. Upon electrochemically dealloying 15 the AuAg alloy in 0.1 mol L À1 HClO 4 at a potential of 1150 mV (versus a commercial Ag/AgCl reference electrode, 3 mol L À1 KCl with 3 mol L À1 KNO 3 salt bridge), a nanoporous structure evolves. Subsequently the npAu electrode was cycled in 0.1 mol L À1 H 2 SO 4 with a scan rate of 0.5 mV s À1 between 200 and 1450 mV (versus Ag/AgCl) until the electrode is in a well-reduced and steady state.…”

Nano-mousses métalliques - Structure et élaboration

“…On trouvera également l'argent, le palladium, le platine, le cuivre [14]. Il existe deux modes de dissolution sélective, par attaque chimique naturelle et par attaque électrochimique [15]. La seconde méthode dite méthode du template fait appel à des techniques plus récentes.…”