| Abstract: | We have studied whether photoconductivity is observed in polymer films containing the first transition metal complexes. Polymers investigated were poly(vinyl alcohol) (PVA), polyacrylamide, poly(acrylic acid), poly(vinyl pyrrolidone), and polyethylene glycol. Transition metal salts used were CrCl3, MnCl2, FeCl3, CoCl2, NiCl2, FeBr3, Fe(NO3)3, Fe2(SO4)3, and Fe(ClO4)3. Only in the PVA–FeCl3 film was relatively large photoconductivity due to the photoreduction of Fe3+ observed. ESR spectra indicate that an Fe3+ ion is chelated with two in-plane OH residues of PVA and coordinated with three Cl?ions on the meridian. UV irradiation causes an electron transfer from Cl? to Fe3+. The produced chlorine atom extracts an electron from the oxygen of a neighboring OH residue. The unpaired electron thus formed can move from one oxygen to another through hydrogen bonding. In other words, the photoconductivity is due to holes produced in the network of PVA hydrogen bonding by the reduction of Fe3+. Finally, we have tried to explain why the photoconductivity is observed only in the PVA–FeCl3 film. |
