K. Viswanathan et P. Natarajan, STUDIES ON THE PHOTOELECTROCHEMICAL PROPERTIES OF THIONINE DYE COVALENTLY BOUND TO POLY(ACRYLAMIDOGLYCOLIC ACID), Journal of photochemistry and photobiology. A, Chemistry, 95(3), 1996, pp. 255-263
Thionine dye, TH+, covalently attached to a macromolecule, poly(acryla
midoglycolic acid) (P(AGA)), was prepared. Flash photolysis of the mac
romolecule-bound thionine, P(AGA)-TH+, in the presence of Fe(II) ions
shows that the absorption spectrum of polymer-bound semithionine radic
al is not significantly changed from that of monomeric semithionine. T
he rate constant for the disproportionation reaction of polymer-bound
semithionine is significantly decreased compared with that of unbound
semithionine. Cyclic voltammetric studies show that the electron trans
fer processes occurring at the electrode are less reversible for P(AGA
)-TH+ in homogeneous solution than for P(AGA)TH+ coated onto an electr
ode as a thin film. For P(AGA)-TH+ coated onto an electrode or an elec
trode immersed in P(AGA)-TH+ in homogeneous solution, cathodic behavio
ur is observed at the illuminated electrode, indicating a change in th
e polarity of the electrode in comparison with the reaction observed a
t a platinum electrode with thionine and iron(II) present in homogeneo
us solution. Stabilization of the charge-separated thionine-iron(II) c
omplex by the polymer network seems to be an important factor for effi
cient charge transfer at the electrode.