Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers.

Citation:

Burt DP, Cervera J, Mandler D, Macpherson JV, Manzanares JA, Unwin PR. Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers. Phys. Chem. Chem. Phys.Physical Chemistry Chemical Physics. 2005;7 (15) :2955 - 2964.

Date Published:

2005///

Abstract:

A new method was developed for measuring local adsorption rates of metal ions at interfaces based on scanning electrochem. microscopy (SECM). The technique is illustrated with the example of Ag+ binding at Langmuir phospholipid monolayers formed at the H2O/air interface. Specifically, an inverted 25 μm diam. Ag disk ultramicroelectrode (UME) was positioned in the subphase of a Langmuir trough, close to a dipalmitoyl phosphatidic acid (DPPA) monolayer, and used to generate Ag+ via Ag electrooxidn. The method involved measuring the transient current-time response at the UME when the electrode was switched to a potential to electrogenerate Ag+. Since the Ag+/Ag couple is reversible, the response is highly sensitive to local mass transfer of Ag+ away from the electrode, which, in turn, is governed by the interaction of Ag+ with the monolayer. The methodol. was used to det. the influence of surface pressure on the adsorption of Ag+ ions at a phospholipid (dipalmitoyl phosphatidic acid) Langmuir monolayer. The capacity for metal ion adsorption at the monolayer increased as the d. of surface adsorption sites increased (by increasing the surface pressure). A model for mass transport and adsorption in this geometry was developed to explain and characterize the adsorption process. [on SciFinder(R)]

Notes:

CAPLUS AN 2005:623564(Journal)