Tuning The Potential Of Nanoelectrodes To Maximum: Ag And Au Nanoparticles Dissolution By I- Adsorption Via Mg2+ Adions

Our work contributes to a better understanding of interfacial processes that lead to Ag and Au metal nanoparticle dissolution by repetitive oxidative steps. According to literature studies, the adsorption of an electron donor (nucleophile) such as I- to a metal nanoparticle raises the Fermi energy of the electrons, and consequently, an electron is transferred from the nanoparticle to an electrophilic species such as O-2. As a result, a metal cation is formed at the surface of the nanoparticle and subsequently dissolved into the solution; such repetitive processes lead to the complete dissolution of the nanoparticle. In this study, we show a remarkably simple method to increase the chemisorption rate of I- by generating additional adsorption active sites via Mg2+ adsorbed ions (adions) and consequently increasing the dissolution rate of metallic Ag nanoparticles (AgNPs). Thus, an increase of the dissolution rate by 57% was estimated when supplementing the Ag colloidal solution with I- and Mg2+, compared to the case when adding only I-. In addition, the significant increase in the chemisorption rate of I-, mediated by Mg2+ adions, leads to a 16% faster decrease in AgNPs radius, due to their dissolution, as probed by UV-Vis spectroscopy and by surface-enhanced Raman scattering (SERS). Further, electron density increase in single Au nanoparticles (AuNPs) due to partial charge transfer from chemisorbed I- ions, and subsequent AuNP dissolution, were tracked through single particle dark-field scattering.