STUDY ON THE PHOTOELECTROCHEMICAL PROPERTIES OF VIOLOGENS IN ACIDIC MEDIA

Abstract

Viologens (V) are electroactive organic molecules bearing typical properties such as structural diversity,
high electron transfer, and particularly the redox state dependent colloring. Therefore, study on the
photoelectrochemcial properties of viologens is necessary to enlarge their applications in the fields of
electrochemical sensing and electrochromics. In this work, we present such research results on the
electrochemical properties of viologen molecules including dibenzyl viologen (DBV), diphenyl viologen
(DPV) và diethyl viologen (DEV) deposited on indium tin oxide (ITO) in acidic media by cyclic voltammetry
(CV) method. The DPV and DBV molecules undergo two subsequent redox processes (V2+ V
+ V
0
),
whereas the DEV only involves in single one (DEV2+ DEV+
) within the potential range of 0.3 V  1.0 V
vs Ag/AgCl (CKCl = 3M). Moreover, impact of the redox states on the optical property of DBV is
characterized in detail using in-situ UV-Vis technique. At E = -0.2V vs Ag/AgCl, where the DBV2+ cation
exists, the corresponding UV-Vis spectrum shows a featureless behavior. Contrarily, at E = -0.8V and E =
-1.0 V vs Ag/AgCl, where the DBV+ and DBV0 moieties are generated, respectively, the corresponding
UV-Vis spectra reveal such emerged absorption bands with their maximum peaks at 380 nm and 540 nm.
The findings demonstrate that the optical properties of viologens can be tuned by the applied electrode
potentials.