The Effect of the Concentration of Phosphotungstic Acid on Its Radiation-Induced Reduction in Nanocomposites with Poly(Vinyl Alcohol)

A detailed analysis of the previously discovered effect of the concentration of phosphotungstic acid (PTA) on its reduction within nanocomposite films with poly(vinyl alcohol) (PVA) induced by gamma radiation indicated that the molar absorption coefficient of the maximum of the PTA band due to intervalence charge transfer in reduced PTA heteropolyanions at low PTA concentrations is eight times higher than at high concentrations. Only 20% of this increase is attributed to the predominance of two- and one-electron-reduced heteropolyanions at low and high concentrations, respectively. We concluded that the main reason for the concentration effect is associated with a decrease in the size the PTA nanoparticles with decreasing PTA concentration in the films.