The critical micelle concentration of hydroxyethyl laurdimonium chloride (HY) is estimated in this Letter. MgO exhibited substantial absorbance and fluorescence in presence of HY micelles. The optical properties of MgO were utilized to estimate the critical micelle concentration of a surfactant. The signals of spectra were assigned and explained in terms of electron transitions produced by magnesium and oxygen vacancies of different coordinations. The CMC values of HY evaluated by absorbance, fluorescence and specific conductivity were found to be 9.8, 8.0 and 2.7 mM, respectively. The synthesized MgO nanoparticles were characterized by XRD, TEM, UV and fluorescence spectroscopy. (C) 2015 Elsevier B.V. All rights reserved.