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Our research efforts have focused on two topics:

1)  We have used Hg/GaIn junction device to probe the conductivity of the monolayer assemblies under electrochemical conditions as a function of surface properties of GaIn.  In this approach, the Hg drop and GaIn electrodes are polarized independently and simultaneously to the different electrochemical potentials.  Subsequently, the Hg drop extruded at the tip of the glass capillary and covered with a monolayer of alkanethiols is brought into contact with the surface of GaIn.  Pioneering work by Whitesides Group has shown that GaIn is a convenient substitute for Hg in junction devices.  Nevertheless the irreproducibility of obtained data seem to be a major obstacle in drawing quantitative conclusions based on tunneling measurements.  It appears that the formation of oxides or/and other surface impurities changes significantly the properties of GaIn surface.  We hope that by controlling the electrochemical potential of GaIn in aqueous environment we will be able to quantitatively reproduce the GaIn surface which will provide insight into tunneling mechanism in these devices.  We are currently analyzing data obtained for 3 different alkanethiols under variety of electrochemical conditions.   

2) We have investigated the effect of aliphatic alcohols (1-pentanol, 1 hexanol, 2-hexanol, and 1-heptanol) on the rates of electrochemical electron tunneling across monolayers of n-alkanethiols (CH₃(CH₂)_n–SH, n = 8, 9, 11) self-assembled on an expandable hanging mercury drop electrode (HMDE). The electron transfer between the solution dissolved Ru(NH₃)₆³⁺ and mercury electrode across the n-alkanethiol monolayer occurs via super exchange through-bond tunneling (ET) with a tunneling coefficient decay constant b = 1.1/CH₂. Gradual additions of aliphatic alcohols to the solution resulted in a decrease of the long-range electron transfer rate, by a maximum of 7-fold, dependent upon the alcohol concentration, but independent of the thickness of the n-alkanethiol monolayer (SAM) and the alcohol's chain length. We have proposed the mechanism involving competitive adsorption of the alcohol on the SAM surface to account for the observed kinetic effects.  The previously reported, liquid-like nature of n alkanethiol monolayers on mercury, allows stepwise expansion of the mercury drop electrodes coated with n-decanethiolate monolayer to ca. 125% of the initial surface area, resulting in an increase of the interfacial capacitance consistent with the overall decrease of the film thickness due to hydrocarbon tilt. The rate of ET, in the absence of alcohols, increases upon the hydrocarbon tilt consistent with the 2-pathway electron tunneling model. In the presence of aliphatic alcohols, the alkanethiol-coated Hg drop can be expanded up to ca. 150%, resulting in Ru(NH₃)₆³⁺ electron transfer rates about 10-fold smaller than expected by the 2-pathway model. This result was interpreted in terms of alcohol partitioning into the n-alkanethiol monolayer leading to partly disorganized films. This project resulted in a publication accepted to Journal of Electroanalytical Chemistry.