Atom probe tomography of nanoporous gold formed by dealloying lean noble alloys

Probing the Surface Chemistry of Nanoporous Gold via Electrochemical Characterization and Atom Probe Tomography

“…As revealed by the plotted iso-concentration contours, Cu—originally absent from the NPG phase—is detected throughout almost all regions of the dataset due to the prevalence of trajectory aberrations. Although established APT data analysis algorithms, such as proximity histograms and surface excess calculations, can yield insightful information about the overall composition and shape of the ligaments [ 8 , 9 , 23 , 24 , 25 ], the local evaporation artifacts prevent an atomic-scale look at the monolayer covering the ligament surfaces.…”

“…A thorough investigation into the post-porosity coarsening of NPG developed from lean noble alloys is the subject of a future study. Preliminary observations indicated that after 1 h of exposure to 0.5 M HClO 4 and simultaneous polarization at 0 V MSE , which is well below the critical potential (+0.125 V MSE ; Figure 2 in [ 9 ]), the surface area reduced by a factor of ca. 0.9, as measured via EIS by the method described earlier.…”

“… A 3 nm slice of the Cu-filled NPG developed from Ag 94 Au 5 Pt 1 alloy (for detailed dealloying and APT procedures please refer to [ 9 ]) with different iso-concentration contour lines, color-coded for different at. % Cu, Ag, and Au values of 10 to 90%.…”

“…Gaining insight into the surface composition of metallic nanoporous materials could not only enhance the understanding of the underlying mechanisms of nanoporosity evolution and catalysis, but would be crucial in biosensing applications, in particular, in vivo sensors. However, obtaining insight into the entire surface composition of such tortuous nanostructures has proved to be challenging despite the use of various advanced atomic-scale characterization techniques such as atom probe tomography (APT) [ 8 , 9 ]. While APT reconstructions describe the materials with an atomic resolution, the composition of monolayers (subnanometer bins) cannot be resolved with certainty due to APT aberrations [ 10 , 11 , 12 ].…”

Advanced Characterization and Modification of Nanoporous Metals

“…One drawback of ordinary NPG for such purposes is the continued mobility of Au at the surface, which leads to coarsening of the structure, especially at elevated temperatures. The addition of small amounts of Pt [1] hinders such coarsening, even at low Au contents [2] and also has obvious relevance to catalysis.Atom Probe Tomography (APT) has proved very successful for the nanoscale analysis of NPG [2][3][4]. The essential step was to learn how to electroplate Cu into the pores, achieving complete filling, at least locally.…”