Electrochemical evaluation of the frontier orbitals of organic dyes in aqueous electrolyte

The frontier orbitals, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels, of organic dye (5-(4-(di-p-tolylamino)-phenyl)-4-hexylthiophen-2-yl)-2-cyanoacrylic acid (TT) and (5-(5-(4-(di-p-tolylamino)-phenyl)-4-hexylthiophen-2-yl-methylene)-4-oxo-2-thioxothiazolidin-3-yl)-acetic acid (TS) are evaluated by the electrochemical cyclic voltammetry in aqueous electrolyte. Both dyes are electrochemically active and conduct redox processes when the dyes are blended with DNA–CTMA(DNA-cetyltrimethylammonium). The redox processes of the dyes can be carried out under fast potential scanning, e.g. 1.5 V/s, which indicates the fast charge transfer between the dyes and the electrodes. Well-dispersed dye molecules in DNA–CTMA, rather than the aggregated molecules, result in well-defined redox peaks in the cyclic voltammetry. In addition, the conductive DNA is also proposed to be responsible for the fast charge transfer. HOMO and LUMO levels of TT and TS are −5.40 eV and −3.04 eV for TT, −5.42 eV and −3.40 eV for TS, respectively.