Effects of halide anions on adsorption and 2D condensation of 5-fluorocytosine at hanging mercury drop electrode

Self-assembled layers, and 2D condensed molecular films as their specific cases, are known to be strongly sensitive to external conditions such as temperature, concentration of self-assembling substance(s) in solution, as well as composition of the supporting electrolyte in terms of the kind and concentration of present ions. In this work we have studied effects of a series of four sodium halides on the 2D condensation of 5-fluorocytosine (5-FC) at the hanging mercury drop electrode. This fluorinated nucleobase was selected for the study with respect to its unique 2D condensation properties (previously described in NaCl), showing remarkable capacitance pits in two potential regions (one around the potential of zero charge and the other within highly negative potential region). NaF electrolyte was not able to support 2D condensation of 5-FC, while in NaI and NaBr the 2D condensation was facilitated in comparison with the NaCl electrolyte. Furthermore, we have studied the formation of the 2D condensed film at different temperatures and ac perturbation frequencies to obtaining a complex view into the 5-FC 2D condensation processes. Our results show great importance of the composition of supporting electrolyte, and/or other experimental conditions on the properties of 2D condensed layers.