A Meticulous Focus on the Determination of Critical Micelle Concentration Employing Fluorescence Spectroscopy.

Abstract

Micelles are small spherical structures formed by one or a combination of amphiphilic structures known as surfactants. Surfactants are amphiphilic molecules with both hydrophilic and hydrophobic regions and can self-assemble into micelles above the critical micelle concentration, with the hydrophobic tails oriented inwards and hydrophilic head outwards. In this review article, critical micelle concentration determination using the fluorescence spectroscopy technique is described for both single and mixed micellar systems with the preparation of samples, working principle, and also about theoretical aspects. Fluorescence measurements using direct i.e. intrinsic fluorescence of surfactant molecule and indirect i.e. using extrinsic fluorescence probes have been discussed. Fluorescence spectroscopy offers a sensitive and valid approach for the characterization of surfactant behaviors in aqueous solutions. Various fluorescence parameters are measured at specific wavelengths with an increase in surfactant concentration and a plot is generated from which the critical micelle concentration is determined. Furthermore, the calculation of critical packing parameter is also described which gives an idea about the geometrical arrangement of the surfactant molecules in a micellar structure. This value also provides valuable insights into the micelle's shape and structure. In conclusion, the effectiveness of the fluorescence spectroscopy technique in determining the critical micelle concentration and the critical packing parameter is described in detail in this review article.