Reactive Ag⁺ Adsorption onto Gold

Abstract

Proposed mechanisms of monolayer silver formation on gold nanoparticle (AuNP) include AuNP-facilitated under-potential reduction and antigalvanic reduction in which the gold reduces Ag+ into metallic atoms Ag(0). Reported herein is the spontaneous reactive Ag+ adsorption onto gold substrates that include both as-obtained and butanethiol-functionalized citrate- and NaBH4-reduced gold nanoparticles (AuNPs), commercial high-purity gold foil, and gold film sputter-coated onto silicon. The silver adsorption invariably leads to proton releasing to the solution. The nominal saturation packing density of silver on AuNPs varies from 2.8 ± 0.3 nmol/cm2 for the AuNPs preaggregated with KNO3 to 4.3 ± 0.2 nmol/cm2 for the AuNPs prefunctionalized with butanethiol (BuT). The apparent Langmuir binding constant of the Ag+ with the preaggregated AuNPs and BuT-functionalized AuNPs are 4.0 × 103 M–1 and 2.1 × 105 M–1, respectively. The silver adsorption has drastic effects on the structure, conformation, and stability of the organothiols on the AuNPs. It converts disordered BuT on AuNPs into highly ordered trans conformers, but induces near complete desorption of sodium 2-mercaptoethanesulfonate and sodium 3-mercapto-1-propyl sulfonate from AuNPs. Mechanically, the Ag+ adsorption on AuNPs most likely proceeds by reacting with molecules preadsorbed on the AuNP surfaces or chemical species in the solutions, and the silver remains as silver ion in these reaction products. This insight and methodology presented in this work are important for studying interfacial interactions of metallic species with gold and for postpreparation modulation of the organothiol structure and conformation on AuNP surfaces.

Surface Plasmon Resonance, Formation Mechanism, and Surface Enhanced Raman Spectroscopy of Ag+-Stained Gold Nanoparticles

“…PRS2 is a new spectroscopic method that enables quantitative decomposition of the sample UV-vis extinction spectrum into its absorption extinction and scattering extinction spectrum. The theoretical background, spectral acquisition, and data analysis procedure are available in recent publications (Athukorale et al, 2017b; Siriwardana et al, 2017; Xu et al, 2018a,b). Briefly, the excitation polarization of the spectrofluorometer is set vertical (V) and the detection polarization is kept either vertical or horizontal (H) to acquire PRS2 VV or VH spectra, respectively.…”

Dithiosulfindene Adsorption and Reaction on Gold Nanoparticles in Water

“…Reflective sample substrate (RSS) slides from Raminescent, LLC were used for the Raman and SERS acquisitions. These RSS slides are highly reflective substrates with negligible fluorescence and Raman background …”

“…These RSS slides are highly reflective substrates with negligible fluorescence and Raman background. 30 DTS Adsorption onto AuNPs. As-synthesized AuNPs (2 mL) were mixed with an equal volume of aqueous DTS with a predefined concentration.…”

NaHS Induces Complete Nondestructive Ligand Displacement from Aggregated Gold Nanoparticles

“…The normal and SERS spectra were acquired with the background-free reflective sample substrates (RSS) obtained with Raminescent LLC. 25 The Raman shift was calibrated with a neon lamp. UV−vis spectra were acquired with an Olis HP 8452 diode array spectrophotometer.…”