Study on Electron Transfer Across Surface of Nucleobases Terminated Self-assembled Film

3-Mercaptopropionic acid, Mg2+ and nucleotide monophosphate (NTMP) including guanosine monophosphate (GMP), adenosine monophosphate (AMP), cytidine monophosphate (CMP) and uridine-5′-monophosphate (UMP) were adsorbed onto Au substrates stepwise to form nucleobases terminated surface. Electron transfer (ET) process across the NTMP/Mg2+/MPA/Au multilayer self-assembled film was studied and the ET kinetics were determined using electrochemical methods including cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The experimental results showed that the rate of ET kinetics decreased in the following order: GMP/Mg2+/MPA/Au > AMP/Mg2+/MPA/Au > UMP/Mg2+/MPA/Au > CMP/Mg2+/MPA/Au. The calculated energy gaps (ΔEgap = ELUMO-EHOMO) of their corresponding Mg-NTMP complexes motif increased in the order: ΔEMg-GMP (0.89 eV) < ΔEMg-AMP (1.40 eV) < ΔEMg-UMP (1.57 eV) < ΔEMg-CMP (1.64 eV). The results suggest that the complexation of Mg with the NTMP, and their corresponding ΔEgap may play important role in their ET process across the nucleobases terminated multilayer self-assembled film.