Micellization, aggregation, and molecular interactions involved in CTAB‐Alizarin Red S complexation

Abstract

AbstractSurfactant–dye complexation between anionic dye: Alizarin Red S (ARS) and cationic surfactant:cetyltrimethylammonium bromide (CTAB) was investigated in an aqueous medium at 303.15 K employing various physicochemical characterization to offer an understanding of the micellization conduct. Here, micellization and thermodynamic parameters have been calculated using the tensiometry and conductivity approach. The critical micelle concentration (CMC) of CTAB is observed to decrease in presence of ARS. The Gibbs energy of micellization () remains be negative on increasing the ARS content which indicated the spontaneity of the overall micellization process. Cyclic voltammetry (CV) reflected the impact of interactions between CTAB and ARS. ARS solubilization in CTAB micelles caused a red (bathochromic) shift in the ultraviolet–visible spectrum below the CMC thereby inferring that ARS undergoes J‐type aggregation in the pre‐micellar region. The intercept drawn following the Job's (corrected absorbance vs. CTAB volume ratio plot) method depicted the volume fractions of (equimolar) ARS (VARS) and CTAB (VCTAB) expressed in v/v occurring at VARS/VCTAB = 0.52/0.48, suggesting their stoichiometric ratio of 1:1 amid each molecule of ARS and CTAB leading to CTAB‐ARS ion‐pair complexation. A computational simulation method using molecular orbital energy calculations was used to evaluate the successive correlation between CTAB and ARS to comprehend the binding mechanism. The lower energy gap (ΔE) value of CTAB‐ARS indicated the favorable interaction of ARS with CTAB. Thus, the present work will reflect the significance of surfactant–dye systems in analytical and biochemistry research; and may open novel possibilities in dye absorption and their applications in the removal of dyes using surfactants.