Abstract
The aggregate states of Acridine Orange bimolecular probe in aqueous solution and micelle media were strudied by absorption spectroscopy. The absorption spectra of the solutions involving Acridine Orange (AO) change with their concentrations. On the basis of Kasha's theory on the difference spectrum between the solution of the AO monomer and that of dimer, the averaged distance between molecular planes of AO's and the dihedral angle in dimer molecules were estimated as 4.4 A and 80°, respectively.It was also shown that the AO dimer dissociates by the addition of surfactant to AO aqueous solution. Dissociation equilibrium of bimolecular associates (dimer) of AO was studied thermodynamically. At the temperature of 30-60°C, absorption spectra of aqueous solutions of AO showed only monomer and dimer bands. Spectral changes with varying temperature suggested that a simple equilibrium between AO dimer and monomer. The values of dissociation constant K and dissociation enthalpy δH were estimated to be 4.24-6.45×10-5 mol dm-3 in the range from 40 to 60°C, and 4.16 kcal mol-1, respectively.
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