Valente A J M, Burrows H D, Pereira R F, Ribeiro A C F, Costa Pereira J L G, Lobo V M M
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
Langmuir. 2006 Jun 20;22(13):5625-9. doi: 10.1021/la060285e.
The effect of EuCl3 on the aggregation processes of sodium dodecyl sulfate was investigated. Electrical conductivity data, combined with Eu(III) luminescence measurements, suggest that the formation of micelles involving EuCl3 and SDS occurs at low SDS concentration; the formation of these mixed aggregates was also monitored by light scattering, which indicates that the addition of EuCl3 to SDS concentration at values below the critical micelle concentration of the pure surfactant results in a much higher light scattering than that found just with SDS micelles. It was also found that the Eu(III)/DS- complexes are formed with a binding ratio which varies between 20 and 4, depending on the initial concentration of Eu(III). As the concentration increases, turbidity occurs initially, but solutions become clear subsequently. In contrast to the behavior of SDS in the presence of aluminum(III), no flocculation was observed. From the analysis of electrical conductivity data and comparison with other systems, it is suggested that growth of aggregates happens, probably with formation of nonspherical systems. At the highest concentrations these may involve just Eu(III) and DS- ions. The effect of temperature on the SDS micellization process was studied. The calculated free energy of SDS micellization is not dependent on the initial EuCl3 but is dependent on the final balance between the presence of counterions in solution (ionic strength) and the temperature.
研究了 EuCl₃ 对十二烷基硫酸钠聚集过程的影响。电导率数据与 Eu(III) 发光测量结果相结合表明，在低 SDS 浓度下会形成包含 EuCl₃ 和 SDS 的胶束；还通过光散射监测了这些混合聚集体的形成，这表明在低于纯表面活性剂临界胶束浓度的值下向 SDS 浓度中添加 EuCl₃ 会导致比仅 SDS 胶束更高的光散射。还发现 Eu(III)/DS⁻ 络合物以结合比形成，该结合比根据 Eu(III) 的初始浓度在 20 到 4 之间变化。随着浓度增加，最初会出现浑浊，但溶液随后会变清。与 SDS 在铝(III) 存在下的行为相反，未观察到絮凝现象。通过对电导率数据的分析并与其他系统进行比较，表明聚集体可能会生长，可能会形成非球形系统。在最高浓度下，这些可能仅涉及 Eu(III) 和 DS⁻ 离子。研究了温度对 SDS 胶束化过程的影响。计算得出的 SDS 胶束化自由能不依赖于初始 EuCl₃，而是依赖于溶液中抗衡离子的存在（离子强度）与温度之间的最终平衡。
