Ligand displacement induced morphologies in block copolymer/quantum dot hybrids and formation of core-shell hybrid nanoobjects.
Ligand displacement induced morphologies in block copolymer/quantum dot hybrids and formation of core-shell hybrid nanoobjects.
复制标题
DOI：
10.1039/c7cp04343k
复制
发表时间：
2017-10
期刊：
影响因子：
--
通讯作者：
Sajan Singh;Pratick Samanta;R. Srivastava;A. Horechyy;U. Reuter;M. Stamm;Hsin‐Lung Chen;Bhanu Nandan
中科院分区：
文献类型：
--
作者：
Sajan Singh;Pratick Samanta;R. Srivastava;A. Horechyy;U. Reuter;M. Stamm;Hsin‐Lung Chen;Bhanu Nandan
我们研究了圆柱状聚苯乙烯嵌段聚（4-乙烯基吡啶）（PS-b-P4VP）嵌段共聚物（BCP）与三辛基氧化膦（TOPO）封端的硒化镉（CdSe）量子点（QD）的自组装。发现 QD 通过配体从 QD 表面置换 TOPO 与 P4VP 链相容。然而，我们发现量子点似乎优先定位在 PS/P4VP 界面处，以获得平移熵，从而进一步降低自组装结构的能量。有趣的是，随着 BCP/QD 复合材料中 QD 重量分数的增加，观察到的形态转变是由取代的 TOPO 从 QD 表面迁移到 PS 相驱动的，从而有效地增加了其总体积分数。因此，以PS为少数嵌段的PS-b-P4VP BCP在与QD的复合材料中表现出层状形态。此外，QD 在 PS/P4VP 界面的优先定位导致形成三层层状形态，这是由相对于 SAXS 数据中的高阶峰的主散射峰的抑制推断出来的。由于不对称嵌段共聚物的较长 P4VP 链过度拉伸，形态转变伴随着域间距的显着增加。然而，在以 P4VP 作为少数嵌段的 PS-b-P4VP/CdSe 复合材料中，由于辅助表面活性剂效应的主导以及 CdSe QD 的界面局域化，圆柱形形态得以保留，并且域间距减小。我们还证明，这些 PS-b-P4VP/CdSe 自组装杂化材料可以进一步用于获得分离的核壳纳米物体，例如含有 CdSe QD 的纳米纤维和纳米片。如此获得的纳米物体表现出CdSe量子点典型的光致发光特性。这些光致发光聚合物纳米物体在生物靶向和荧光标记方面具有潜在的应用。
We investigate the self-assembly of a cylinder-forming polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) mixed with trioctylphosphine oxide (TOPO) capped cadmium selenide (CdSe) quantum dots (QDs). The QDs were found to be enthalpically compatible with the P4VP chains via ligand displacement of TOPO from the QD surface. However, the QDs were found to localize preferentially at the PS/P4VP interphase plausibly to gain translational entropy in order to further lower the energetics of the self-assembled structure. Interestingly, the morphological transformation observed with increasing weight fraction of the QDs in the BCP/QD composite was driven by the migration of the displaced TOPO from the QD surface to the PS phase, effectively increasing its total volume fraction. Hence, the PS-b-P4VP BCP with PS as the minority block displayed lamellar morphology in its composite with QDs. Furthermore, the preferred localization of the QDs at the PS/P4VP interface led to the formation of a trilayer lamellar morphology which was deduced from the suppression of the primary scattering peak, relative to higher order peaks in the SAXS data. The morphological transformation was accompanied by a significant increase in the domain spacing due to excessive stretching of the longer P4VP chains of the asymmetric block copolymer. However, in the PS-b-P4VP/CdSe composites with P4VP as the minority block, cylindrical morphology was retained and the domain spacing decreased due to dominance of the co-surfactant effect as well as interfacial localization of CdSe QDs. We also demonstrate that these PS-b-P4VP/CdSe self-assembled hybrid materials could further be used to obtain isolated core-shell nanoobjects, such as nanofibers and nanosheets, containing CdSe QDs. The nanoobjects so obtained exhibited photoluminescence properties typical of CdSe quantum dots. These photoluminescent polymer nanoobjects could have potential applications in biological targeting and fluorescence labeling.