Acs grade

Master alloys Au₂₅Ag₇₅ were prepared according to ref. ^{27 (link)}, except that wire drawing and sectioning by a wire saw were used to make cylindrical samples, 1.17–1.37 mm in diameter and 1.90–2.10 mm in length. Electrochemical dealloying in 1 M HClO₄ (60% HClO₄, ACS grade, Merck) at ambient temperature used a potential of 1.26 V vs. SHE. Reference and counter electrodes (RE and CE) for dealloying were pseudo Ag/AgCl (+0.515 vs. SHE, “HydroFlex”, Gaskatel) and a coiled Ag wire (99.9985%, Alfa Aesar), respectively. Using 1 M HClO₄ prepared from high purity HClO₄ (70%, Suprapur, Merck), the as-dealloyed samples were reduced during 15 potential cycles between 0.01 and 1.01 V with a scan rate of 5 mV s⁻¹; this lead to mean ligament diameter L~20 nm. Cycling 15 times between 0.01 and 1.51 V at 5 mV s⁻¹ led to L ~ 35–45 nm. Rinsing with ultrapure water (Ultra Clear TWF UV TM, Siemens) and drying for >2 days in Ar (5.0) flow at room temperature followed. Samples with L ~ 150 nm were prepared by annealing L = 20 nm NPG at 400 °C for 1 h in Ar. Solid fractions, as determined from external sample dimensions and mass, were φ = 0.27 ± 0.01, 0.29 ± 0.02, 0.32 ± 0.03 for samples with L = 20, 40, 150 nm, respectively. Mean ligament diameters, L, were estimated from scanning electron micrographs. All potentials in this work are referred to the standard hydrogen electrode (SHE).

All reagents and solvents (ACS grade), LiChroprep RP-18, and SiO₂ supports for column and plate chromatography were obtained from Merck (MA, USA). Amberlite XAD16, α-terthienyl, β-sitosterol, stigmasterol, deuterated solvents, and dimethyl sulfoxide (DMSO-Hybri-Max) were obtained from Sigma Chemical (St. Louis, MO, USA).