Discipline of Chemistry , Indian Institute of Technology Indore , Simrol Campus, Khandwa Road , Indore 453552 , MP , India.
Langmuir. 2019 May 14;35(19):6409-6420. doi: 10.1021/acs.langmuir.9b00357. Epub 2019 May 1.
Here, we report the interaction of mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) with hexadecyltrimethylammonium bromide (CTAB) surfactant and subsequent formation of self-assembled multicolor luminescent vesicles in aqueous medium. A continuous phase sequence from clear (C1) to turbid (T1), precipitate (P), turbid (T2), and clear (C2) has been observed for QD solution upon increasing the concentration of positively charged CTAB, indicating dynamic equilibrium between various self-assembled supramolecular structures. In contrast, no such changes have been observed in the presence of negatively charged sodium dodecyl sulfate and neutral Triton X-100 surfactants, indicating specific electrostatic interactions behind the observed phase separation behavior. Epi-fluorescence imaging in the C1 and C2 regions reveals the presence of surfactant-induced aggregates of QD. The morphologies and photoluminescence properties of self-assembled supramolecular structures in the T1 and T2 region have been explored by using scanning electron microscopy (SEM), atomic force microscopy (AFM), and confocal laser scanning microscopy (CLSM). SEM and AFM images reveal distinct spherical vesicles in the T1 and T2 regions of the binary mixture. Moreover, CLSM results show that these spherical vesicles are inherently luminescent due to the presence of self-assembled QDs. Fabrication of multicolor luminescent vesicles has been demonstrated by tuning the size of CdTe QD. Using CLSM, we have further demonstrated efficient encapsulation of Rhodamine 6G dye into these self-assembled vesicles without any structural disruption. While these luminescent vesicles are quite stable in neutral and basic pH (pH = 6.5-11), they are unstable in acidic pH (pH = 4.5-5.5). Moreover, it has been observed that this pH-responsive structural change is totally reversible. The present findings of self-assembled luminescent vesicles from QD-CTAB binary mixture may open up new opportunities in various applications such as bioimaging, drug delivery, and sensing.
在这里，我们报告了巯基琥珀酸（MSA）封端的CdTe 量子点（QD）与十六烷基三甲基溴化铵（CTAB）表面活性剂的相互作用，以及随后在水介质中形成自组装多色发光囊泡。当QD 溶液中阳离子 CTAB 的浓度增加时，QD 溶液已经观察到从透明（C1）到混浊（T1）、沉淀（P）、混浊（T2）和透明（C2）的连续相序列，表明各种自组装超分子结构之间存在动态平衡。相比之下，在存在阴离子十二烷基硫酸钠和中性 Triton X-100 表面活性剂的情况下，没有观察到这种变化，这表明观察到的相分离行为背后存在特定的静电相互作用。在 C1 和 C2 区域的 epi-荧光成像揭示了存在表面活性剂诱导的 QD 聚集体。通过使用扫描电子显微镜（SEM）、原子力显微镜（AFM）和共焦激光扫描显微镜（CLSM），研究了 T1 和 T2 区域自组装超分子结构的形态和光致发光性质。SEM 和 AFM 图像显示二元混合物的 T1 和 T2 区域存在明显的球形囊泡。此外，CLSM 结果表明，由于存在自组装的 QD，这些球形囊泡具有固有发光性。通过调谐 CdTe QD 的尺寸，已经证明了多色发光囊泡的制备。通过 CLSM，我们进一步证明了罗丹明 6G 染料有效地封装到这些自组装囊泡中，而没有任何结构破坏。虽然这些发光囊泡在中性和碱性 pH（pH = 6.5-11）下相当稳定，但在酸性 pH（pH = 4.5-5.5）下不稳定。此外，已经观察到这种 pH 响应的结构变化是完全可逆的。从 QD-CTAB 二元混合物中自组装发光囊泡的发现可能为生物成像、药物输送和传感等各种应用开辟新的机会。
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