The Role of Cl- Ions During the Adsorption of Polyethylene Glycol (MW 20,000) onto a Polycrystalline Gold Electrode

摘要

The adsorption of polyethylene glycol (MW 20,000) (PEG20000) onto a polycrystalline gold electrode- in the presence of Cl ions was studied by differential capacitance measurements and quartz crystalmicrobalance. This study provides new physical insights into the adsorption behavior of this polymer- onto a solid electrode in the presence of Cl ions and KClO4. Three potential-based behaviors wereobserved: in the potential range from -0.90 to -0.62 V vs. the saturated calomel electrode (SCE), theprincipal adsorption process was observed to form a condensed PEG20000 phase. In addition, there was-a slight desorption of PEG20000. In the potential range from -0.62 to -0.10 V vs. SCE, the addition of Cl ions to the solution reduced the amount of PEG20000 adsorbed. This behavior was associated with the- lower number of available active adsorption sites on the gold surface due to the adsorption of Cl ions.In addition, we observed the superposition of the two adsorption processes on different active sites.-PEG was adsorbed on lower-energy adsorption sites (the most accessible adsorption sites), whereas Cl ions were adsorbed on higher-energy adsorption sites (the least accessible adsorption sites). The- potential range from -0.10 to 0.35 V vs. SCE was dominated by the adsorption of Cl ions, and a- displacement of adsorbed PEG20000 molecules associated with the adsorption of Cl anions wasobserved.