On the monolayer adsorption of thiol-terminated dendritic oligothiophenes onto gold surfaces

The self-assembled monolayer formation of a series of thiophene dendron thiols with different generations and alkyl chain lengths onto gold surfaces is studied. Average film thicknesses and dielectric constants were calculated from SPR using a two-subphase differential method. The in situ adsorption of the thiophene dendron thiols was monitored by SPR kinetics measurements and fitted using an empirical three-step model. Electrochemical redox molecular probing experiments provided additional insight into surface coverage, which showed different abilities to block electron transfer at the monolayer/electrode interfaces. The surface coverage of the films was also estimated by QCM measurements and supported by static WCA measurements. Oligothiophene dendrons with functional thiol end groups are used as ligands to modify gold and semiconductor nanoparticles changing energy transfer and charge transport properties. These series of dendrons have competitive adsorption properties on Au surfaces. Using surface plasmon resonance spectroscopy, the adsorption kinetics are determined and modeled based on a non-linear fit, taking into account monolayer reorganization.