Investigating the micellization of the triton-X surfactants: A non-invasive fluorometric and calorimetric approach

Highlights: • The micellization of commercially important non-ionic Triton X surfactants has been studied. • Intrinsic and extrinsic fluorescence and calorimetric methods have been applied. • CMCs as reported by the external probes do not match well with that evaluated intrinsically for Triton X-165. • ITC results for determining the CMC support those obtained from intrinsic approach. • The process of micellization is shown to be entropically and enthalpically favorable. Using intrinsic and extrinsic fluorescence approaches, we have studied the Critical Micelle Concentration (CMC) of three non-ionic surfactants namely, Triton X-114 (TX-114), Triton X-100 (TX-100) and Triton X-165 (TX-165) which differ in number of polyethylene oxide (PEO) groups. We have established that for TX-114 and TX-100, the external fluorophores C-153 and ANS support our intrinsic approach, whereas, for TX-165, the same is perhaps not true. This has been attributed to the different numbers of PEO groups constituting the surfactant systems. We have also studied the CMC using Isothermal Titration Calorimetry (ITC) which is in excellent harmony with our intrinsic approach.