Results of cyclic voltammetric and impedance measurements demonstrate that small aromatic diselenides like diphenyl diselenide can form a self-assembled monolayer with 99% surface coverage on polycrystalline gold. The redox response of a solution species like Fe(CN)(4-/3-) is partially blocked as a result of SAM formation, and the double layer capacitance is also observed to decrease (i.e., 9.4 mu F/cm(2) as compared to 21 mu F/cm(2) for bare gold) due to the increased separation between the electrode surface and the plane of closest approach for ionic charges. Impedance analysis suggests that pinholes tend to distribute as isolated patches over the monolayer surface. Furthermore, quartz crystal microbalance measurement shows a steady-state mass loading of about 292 ng, indicating the monolayer formation.