Multilayers of mixed monolayer thiolate-protected Au nanoparticles with polycationic ligand shells are strongly and persistently adsorbed on Pt electrodes from dilute CH 3 CN/electrolyte solutions of the nanoparticles. The adsorption is so robust that the electrodes can be transferred, with rinsing, to nanoparticle-free CH 3 CN/ electrolyte (and other organic solvents) and their voltammetry observed without significant desorption. The nanoparticles have the average composition [Au 225 (TEA-thiolateThe cation sites are a quaternary ammonium-terminated ligand (TEA-thiolate + ) -S(CH 2 ) 11 N(CH 2 CH 3 ) 3 + ). The ferrocene content of the ligand shell (Y) allows voltammetric detection of the adsorption, and also affects it. This work describes how the extent of nanoparticle adsorption (surface coverage, Γ NP mol/cm 2 ) depends on the manner of exposure of the electrode (with potential scanning, at a fixed potential, or at open circuit) to the nanoparticle solution, and on the nanoparticle concentration, the electrolyte and its concentration, and on the mixed monolayer composition. Increase of the cationic TEA-thiolate + component of the mixed monolayer from X ) 18 to 27 increases, for a given exposure mode, the attained amount of adsorption from < one monolayer to > two monolayers, and broadens the voltammetric wave. The adsorption phenomenon is interpreted as induced by multiple ion-pair bridges between cation sites and electrolyte anions, and as such represents an entropic consequence of multiple interactions between nanoparticles and between nanoparticles and the electrode.
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