ELECTROCHEMICAL-BEHAVIOR OF THE NAPHTHOQUINONE ANCHORED ONTO A GOLD ELECTRODE THROUGH THE SELF-ASSEMBLED MONOLAYERS OF AMINOALKANETHIOL

2,3-Dichloro-1,4-naphtoquinone (NQ) was anchored to a gold electrode s urface through the self-assembled monolayers of aminoalkanethiols (AAT , HS(CH2)(n)NH2: n = 2, 5, and 8). The effect of the alkyl chain lengt h of the AAT monolayer, which also acts as the spacer between the NQ m olecule and the gold electrode surface, on the redox behavior of the i mmobilized NQ has been studied by using a voltammetric technique. The surface coverage of the anchored NQ was estimated to be 3.8x10(-10) mo l cm(-2) in the case that 2-aminoethanethiol (HS(CH2)(2)NH2) was used as the monolayer constituent. The electron-transfer rate constant, k(e t), associated with the redox process of anchored NQ decreased from 9. 7 s(-1) at n = 2 to 0.78 s(-1) at n = 8, with increasing the chain len gth of the AAT monolayer, though the redox potential of NQ was scarcel y affected by the chain length. The tunneling barrier coefficient, bet a, of the electron transfer was estimated to be 0.36 Angstrom(-1), fro m the observed linear relationship between the k(et) value and the mon olayer chain length.