Studies of surfactant/water systems near the critical micellar concentration using thermal lens spectroscopy

Abstract

Abstract.A novel application of photothermal spectroscopy to the study of surfactant-water systems near the critical micellar concentration is reported. The thermal lens signal was induced by a slightly soluble dye and was measured with a dual-beam thermal lens spectrometer.For the two surfactants considered: nonyl phenol and Triton X-100, sharp variations of the thermal lens signal were observed at the critical micellar concentration (CMC), namely an increase for nonyl phenol and a decrease for triton X-100. These effects are arguably related to micelle formation.Our work serves as an initial assessment of the potential of the technique for the study of disperse systems of a higher complexity or dark systems where conventional techniques are impossible to apply.

Thermal and Nonlinear Optical Properties of Potassium Laurate/Water Solutions at Amphiphilic Concentrations around the Critical Micellar Concentration: A Laser Gaussian Single Beam Experiment in Millisecond Timescales

“…Figures and show typical results of a Z-Scan experiment with samples with c ≲ cmc and c > cmc: the optical transmittance as a function of time, with the sample at a fixed z position (Figure ); and the normalized optical transmittance as a function of z (Figure ). It is important to stress here that our results refer to pure mixtures, without any dye doping, different from the results described in refs and . Inspection of Figure shows a striking feature of the Z-Scan curve: before the amphiphilic concentration reaches the cmc, the peak-to-valley distance is small, indicating a small nonlinear response of the medium, but at concentrations of about 10 × cmc, this response increases and remains almost the same up to concentrations of about 100 × cmc.…”

“…Castillo and co-workers studied the surfactants Triton X-100 and the nonyl phenol using TLS in the vicinity of the cmc 18 using dyes to enhance the sample response. The thermal lens signal (as a function of c ) presented a crossover between two different behaviors, which was interpreted as due to changes in the heat transport properties of the medium, as a consequence of the micelle formation …”

“…Different experimental techniques have been used to study the molecular aggregation in solutions around the cmc, for example, differential scanning calorimetry, conductivity, and surface tension . The interest in studying the thermal properties of amphiphilic molecule solutions using the thermal lens spectroscopy (TLS) technique ,,, increased in the past decade. This technique is particularly sensitive and presents a low complexity .…”

The Use of Triton X-100 in Thermal Lensing of Aqueous Solutions

“…24 Thus, this proves the assumption that thermal lens spectrometry can detect surfactants down to the level they start affecting thermooptical parameters of the solvent. 4,5,8,9 The determination is characterized by good replicability (RSDrep = 3 -8%).…”

“…[1][2][3][4] Until now, a number of studies have dealt with surfactants as media modifiers in thermal lensing, but mainly in physicochemical studies. [5][6][7][8][9][10] The aims of this work were (1) to study the effect of an inert nonionic surfactant (Triton X-100) on performance characteristics of thermal lensing of iron(II)-1,10-phenanthroline and cobalt(III)-2-nitroso-1-naphthol as model systems and (2) to use the change in the thermooptical properties of water for the determination of the surfactant itself.…”