Surface/interface investigation of positron diffusion in electrochemically reduced nanoporous Au from dealloyed nanoporous Au

Abstract

Positron lifetime measurements, variable energy positron beam Doppler broadening analyses, and electron microscopy studies were performed to investigate morphological evolution and its influence on positron diffusion behavior in electrochemically reduced nanoporous Au. Samples were obtained by potential cycling of as-dealloyed nanoporous Au within reduced potential intervals. Electron microscopy revealed significant morphological changes, resulting in a random structure composed of Au ligaments. Positron lifetime and S(E_P) measurements provided insights into effective diffusion length of positrons, which scaled with the ligament diameter with an exponent of ∼0.5, contrasting with the behavior observed in as-dealloyed nanoporous Au. Positronium fraction calculations showed preferentially positron diffusion toward the surfaces/interfaces of the ligament pore networks. Nanoindentation measurements of Young’s modulus correlated with the microstructure and defect characteristics of the reduced nanoporous Au. These findings enhance our understanding of how variations in vacancy defects associated with ligament surfaces/interfaces substantially impacts the mechanical properties of nanoporous Au assemblies.