Spectroscopic studies of the interaction between methyl orange and gemini surfactant

The influence of two kinds of cationic surfactants on spectral properties of methyl orange in aqueous solutions has been investigated by means of UV-vis spectroscopy in various pH values and concentration range. For the Gemini14-methyl orange (MO) solutions, a hyperchromic shift was observed from 509-403 nm with the decrease of spectra absorption by increasing the pH values. Spectral behaviour of dye-surfactant solutions with varying concentrations of surfactants confirmed that electrostatic hydrophobic interactions between dye and surfactant played an important role. An H-type aggregation appeared in the concentration ratio 1:2 for Gemini14 and methyl orange, but in the CTAB solutions, the ratio was 1:1. The initial decrease of the absorbance resulted from dye-surfactant complex formation. It can be concluded that the amount of the cationic groups plays an important role in the complex formation.