Self-assembled monolayers on mercury probed in a modified surface force apparatus.
Self-assembled monolayers (SAMs) of three thiol compounds formed on mercury are investigated by a combination of cyclic voltammetry, electrocapillary curves, and a novel method of measuring electrical double-layer properties. The last method involves a modified surface force apparatus in which a flat mica surface is pressed down toward a fixed mercury drop held beneath it, while both are immersed in aqueous electrolyte solution. Optical interference measurements are made of the mica-mercury separation as a function of electrical potential applied to the mercury, which yields information on the double-layer interaction between the two surfaces. Mercury is decorated by SAMs of 11-mercapto-1-undecanoic acid, which is shown to bring negative charge to the mercury/aqueous interface due to dissociation of the carboxylic acid groups; 11-mercapto-1-undecanol, which although it is uncharged changes the dipole potential of the interface; and 1-undecanethiol, which likewise changes the dipole potential, but by a different amount. The difference between the changes in dipole potential (90 mV) can be related to the different terminal groups of these two SAMs, -CH3 compared to -OH, that are in contact with the aqueous phase.
Clasohm
Lucy Y
LY
Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide SA 5095, Australia.
Chen
Miao
M
Knoll
Wolfgang
W
Vinogradova
Olga I
OI
Horn
Roger G
RG
D004563:Electrochemistry; D005227:Fatty Acids / Q000737:chemistry; D008628:Mercury / Q000737:chemistry*; D015335:Molecular Probes; D013438:Sulfhydryl Compounds / Q000737:chemistry
C505222:11-mercaptoundecanoic acid; D005227:Fatty Acids; D015335:Molecular Probes; D013438:Sulfhydryl Compounds; D008628:Mercury