Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
Langmuir. 2011 Oct 18;27(20):12312-21. doi: 10.1021/la202414h. Epub 2011 Sep 26.
The aggregation behavior of the DNA marker dye thiazole orange (TO), has been investigated in two types of surfactant assemblies, namely, premicelles/micelles of sodium dodecyl sulfate (SDS) and pre reverse micelles/reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT). In the case of an SDS/water system, absorption spectral changes of TO signify the formation of H-aggregates and H-dimers of the dye at premicellar concentrations, which subsequently convert to the monomeric form beyond the critical micellar concentration (cmc). Interestingly, the observed changes in the absorption and emission characteristics due to the surfactant-induced formation of H-aggregates/dimers of TO are found to be useful to estimate the surfactant concentration parameters for premicellar aggregation of SDS. In the case of an AOT/n-heptane system, similarly, H-aggregates/dimers are observed at low AOT concentrations, below the cmc. However, in this case, the H-dimers persist even beyond the cmc. This is attributed to the strong tendency of TO for self-aggregation and its favorable electrostatic interactions with the AOT head groups. With increasing water content in the AOT reverse micelles, the hydration of the dye leads to the conversion of H-dimers to the monomeric form. The steady-state fluorescence results are nicely corroborated with those from time-resolved fluorescence studies and demonstrate the interesting behavior of the surfactant-induced aggregation of TO dye.
DNA 标记染料噻唑橙（TO）的聚集行为已在两种类型的表面活性剂组装体中进行了研究，即十二烷基硫酸钠（SDS）的预胶束/胶束和双（2-乙基己基）磺基琥珀酸钠（AOT）的预反胶束/反胶束。在 SDS/水体系中，TO 的吸收光谱变化表明在预胶束浓度下染料形成 H-聚集体和 H-二聚体，随后在临界胶束浓度（cmc）以上转化为单体形式。有趣的是，由于表面活性剂诱导 TO 的 H-聚集体/二聚体的形成而观察到的吸收和发射特性的变化被发现可用于估计 SDS 预胶束聚集的表面活性剂浓度参数。在 AOT/n-庚烷体系中，同样，在低于 cmc 的低 AOT 浓度下观察到 H-聚集体/二聚体。然而，在这种情况下，H-二聚体甚至在 cmc 以上也存在。这归因于 TO 自聚集的强烈趋势及其与 AOT 头基的有利静电相互作用。随着 AOT 反胶束中含水量的增加，染料的水合作用导致 H-二聚体转化为单体形式。稳态荧光结果与时间分辨荧光研究的结果很好地吻合，证明了 TO 染料的表面活性剂诱导聚集的有趣行为。
