10.1021/ac9010364.s001
Rajesh Sardar
Rajesh
Sardar
Christopher A. Beasley
Christopher A.
Beasley
Royce W. Murray
Royce W.
Murray
Ferrocenated Au Nanoparticle Monolayer Adsorption on Self-Assembled Monolayer-Coated Electrodes
American Chemical Society
2009
monolayer films
polyfunctional character
SAM
3SO
nanoparticle film
nanoparticle adsorption
methyl termini
Nanoparticle Monolayer Adsorption
electrode
PF
CH 2Cl
NP
alkyl chain length
CF
Bu 4N electrolyte
7H
surface adsorption
2009-08-15 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Ferrocenated_Au_Nanoparticle_Monolayer_Adsorption_on_Self_Assembled_Monolayer_Coated_Electrodes/2835229
The robust, irreversible adsorption of ω-ferrocene hexanethiolate-protected gold nanoparticles (composition ca. {Au<sub>225</sub>(SC6Fc)<sub>43</sub>}) on electrodes provides an opportunity to investigate their submonolayer and monolayer films in nanoparticle-free solutions. Observations of nanoparticle adsorption on unmodified electrodes are extended here to Au electrodes having more explicitly controlled surfaces, namely self-assembled monolayers (SAMs) of alkanethiolates with ω-sulfonate, carboxylate, and methyl termini, and in different Bu<sub>4</sub>N<sup>+</sup><i>X</i><sup>−</sup> electrolyte (<i>X</i><sup>−</sup> = C<sub>7</sub>H<sub>7</sub>SO<sub>3</sub><sup>−</sup>, ClO<sub>4</sub><sup>−</sup>, CF<sub>3</sub>SO<sub>3</sub><sup>−</sup>, PF<sub>6</sub><sup>−</sup>, NO<sub>3</sub><sup>−</sup>) solutions in CH<sub>2</sub>Cl<sub>2</sub>. The nanoparticle surface coverage (Γ<sub>NP</sub>) and the stability of the adsorbed nanoparticle film to repeated ferrocene/ferrocenium redox cycling decrease in the order of sulfonate > carboxylate > methyl terminated SAM, with increasing hydrophobicity of <i>X</i><sup>−</sup> and with increasing alkyl chain length. The results are consistent with the proposal that the strong surface adsorption is jointly associated with the polyfunctional character of the nanoparticles, analogous to entropically driven adsorptions of polymeric ions on charged surfaces, and with lateral, ion-bridged nanoparticle−nanoparticle interactions.