Yadav Shiv Narayan, Rai Summi, Bhattarai Ajaya, Sinha Biswajit
Department of Chemistry, Mahendra Morang Adarsh Multiple Campus, Tribhuvan University, Biratnagar, 56613, Nepal.
Department of Chemistry, University of North Bengal, Darjeeling, 734013, India.
Heliyon. 2024 Jun 13;10(12):e33014. doi: 10.1016/j.heliyon.2024.e33014. eCollection 2024 Jun 30.
This research aims to comprehensively investigate and analyze the UV-visible spectroscopic behavior of the methyl red (MR)-cetyltrimethylammonium bromide (CTAB) system under the influence of sodium polystyrene sulfonate (NaPSS) in aqueous and different volume fractions (v.f.) of ethanol (EtOH)-HO (0.1, 0.2, and 0.3) at 298.15 ± 0.2 K. In EtOH-HO solvent systems, the triple interactions of dyes-surfactants-polyelectrolyte (DSP) complex systems are entirely novel. MR interacts with CTAB in NaPSS in the binary solvent media (0.1, 0.2, and 0.3 v.f. of EtOH-HO) resulting in the formation of ion-pairs at very low CTAB concentrations, far below their apparent critical micelle concentration (CMC*) reducing the absorbance, and the new complexes above the CMC* due to solubilization of the MR into CTAB micelles observed by distinct spectral shifts. The CMC* values obtained from spectroscopic data increase in the order: (CMC*) (CMC*) (CMC*) (CMC*). This is because of the reduced polarity or dielectric constant and increased degree of water structure disruption around the hydrophobic chains of CTAB, where micelle formation occurs at somewhat higher concentrations. The Gibbs energy of micellization ( increases in the order: ) < ) ) ), which further supports the inhibitory effect of increasing ethanol content towards micellization. In the post-micellar region, the decrease in hydrophobic interactions and an increase in electrostatic interactions lead to a rise in the overall binding constant value. This means that, when NaPSS is present, the stronger electrostatic interactions in the post-micellar region contribute significantly to the increased binding of CTAB micelles with MR. The tautomeric activity of MR and the solvent composition played a prime role in affecting the interaction mechanism, as evidenced by the blue and red spectral shifts.
本研究旨在全面调查和分析在298.15±0.2 K温度下，在水以及不同体积分数（v.f.）的乙醇（EtOH）-水（0.1、0.2和0.3）中，聚苯乙烯磺酸钠（NaPSS）影响下甲基红（MR）-十六烷基三甲基溴化铵（CTAB）体系的紫外-可见光谱行为。在EtOH-水溶剂体系中，染料-表面活性剂-聚电解质（DSP）复合体系的三重相互作用是全新的。在二元溶剂介质（EtOH-水的体积分数为0.1、0.2和0.3）中，MR在NaPSS存在下与CTAB相互作用，在极低的CTAB浓度下（远低于其表观临界胶束浓度（CMC*））形成离子对，导致吸光度降低，而在CMC以上由于MR溶解到CTAB胶束中形成新的配合物，表现为明显的光谱位移。从光谱数据获得的CMC值按以下顺序增加：（CMC*） （CMC*） （CMC*） （CMC*）。这是因为CTAB疏水链周围的极性降低或介电常数减小，以及水结构破坏程度增加，胶束形成发生在稍高的浓度下。胶束化的吉布斯自由能（ ）按以下顺序增加： < < < ，这进一步支持了乙醇含量增加对胶束化的抑制作用。在胶束后区域，疏水相互作用的降低和静电相互作用的增加导致整体结合常数的值升高。这意味着，当存在NaPSS时，胶束后区域更强的静电相互作用对CTAB胶束与MR结合的增加有显著贡献。MR的互变异构活性和溶剂组成在影响相互作用机制方面起主要作用，蓝色和红色光谱位移证明了这一点。
