Effect of the U.V. Irradiation on the Aqueous Solution of Dye (i.e. Cresol Purple)

Abstract

This study aimed to estimate the effect of the U.V. irradiation on the aqueous solution of cresol purple. Then study the effect of the activation energy of each electron transfere on the absorbance and λ_max values. The absorbance and λ_max values of the selective λ_max solutions were chanced in most solutions, where the U.V radiation gave different values at different irradiation periods, most of solution gave low values of absorbance comparing with the original standard solutions of the indicator and the λ_max were changed, most of solution showed a relative changes in λ_max values and gave high absorbance values comparing with the original standard solutions of dye. The study attributed those changes in absorbance are due to the effecting to U.V irradiations on the type of electronic transition of π → π* and πn → π* which they were attributed to the original structure of the indicator used. The spectra of absorption of the unirradiated and irradiated solutions were measured in the wavelength from 250 to 650 nm according to λ_max of the original solution. The λ_max values were measured by studying the λ_max change at different time periods (5, 10, 15, 20 min) of U.V irradiance. To calculate the transition energy values were used the equation (ET = h C NA/λ).