Spectral changes of co-doped PVA films in relation to their structures

Summary The optical absorption spectra of Co-doped PVA thick films (1 mm) of different concentrations from 0.0 to 30% CoCl₂ are obtained at room temperature in the range 190–900 nm. Cobalt (II) is found to exist only in octahedral coordination for concentrations up to 10% with an asymmetrical absorption band located at 511 nm and shifted to longer weve length with increasing CoCl₂ content. For higher concentration (>10%) the coexistence of both octahedral and tetrahedral coordinations is indicated by the appearance of a new structured broad band centered at 665 nm. Variations in the obtained spectra suggest a tendency to higher degree of ordering in the amorphous regions of the polymer structure by CoCl₂ addition.