Metal Nanoparticle Enhancement of Electron Transfer to Tethered Redox Centers through Self-Assembled Molecular Films

HERRERA, S..; DAVIA, F.; WILLIAS F.J.; CALVO,E.J.

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington DC; Año: 2019 vol. 35 p. 6297 - 6303

0743-7463

Metal-nanoparticle-mediated electron transfer (ET) across an insulator thin film containing nanoparticles with attached redox centers was studied using electrochemical impedance spectroscopy. Specifically, a gold spherical microelectrode was modified with 16-amino-1-hexa-decanethiol, creating an insulator film. This was followed by the electrostatic adsorption of gold nanoparticles and the covalent attachment of Os2+ redox centers. A variation of the Creager?Wooster method was developed to get quantitative information regarding the ET kinetics of the system. The experimental data obtained from a single measurement was fitted with a model that decouples two or more ET processes with different time constants and considers a Gaussian distribution of tunneling distances. Two parallel ET mechanisms were observed: one in which the electrons flow by tunneling between the surface and the redox couples with a low kET0 = 1.3 s?1 and a second one in which an enhancement of the electron transfer is produced due to the presence of the gold nanoparticles with a kET0 = 7 × 104 s?1. In this study, we demonstrate that the gold nanoparticle electron transfer enhancement is present only in the loc