Beijing National Laboratory for Molecular Science, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, People's Republic of China.
University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
ACS Nano. 2016 Dec 27;10(12):11179-11186. doi: 10.1021/acsnano.6b06233. Epub 2016 Dec 1.
The fabrication of chiroptical plasmonic nanomaterials such as chiral plasmonic gold nanorods (GNRs) has been attracting great interest. Generally, in order to realize the plasmonic circular dichroism (PCD) from achiral GNRs, it is necessary to partially replace the surface-coated cetyltrimethylammonium bromide with chiral molecules. Here, we present a supramolecular approach to generate and modulate the PCD of GNRs through the hybrid gelation of GNRs with an amphiphilic chiral dendron gelator. Upon gelation, the PCD could be produced and further regulated depending on the ratio of the dendrons to GNRs. It was revealed that the wrapping of the self-assembled nanofibers around the GNRs is crucial for generating the PCD. Furthermore, the hybrid gel underwent a thermotriggered gel-sol and sol-gel transformation, during which the PCD can disappear (solution) and reappear (gel), respectively, and such process can be repeated many times. In addition, the hybrid gel could also undergo shrinkage upon addition of a slight amount of Mg ions, during which the PCD disappeared also. Thus, through the gel formation and subsequent metal ion- or temperature-triggered phase transition, PCD can be reversibly modulated. The results not only clarified the generation mechanism of PCD from the achiral GNRs without the chiral modification on the surface but also offered a simple and efficient way to modulate the PCD.
手性等离子体纳米材料的制备，如手性等离子体金纳米棒（GNRs），引起了人们的极大兴趣。通常，为了实现非手性 GNRs 的圆二色性（PCD），需要用手性分子部分取代表面包覆的十六烷基三甲基溴化铵。在这里，我们提出了一种超分子方法，通过 GNRs 与两亲性手性树枝状凝胶剂的混合凝胶化来产生和调节 GNRs 的 PCD。凝胶化后，可以根据树枝状大分子与 GNRs 的比例产生和进一步调节 PCD。结果表明，自组装纳米纤维围绕 GNRs 的包裹对于产生 PCD 至关重要。此外，混合凝胶经历了热触发的凝胶-溶胶和溶胶-凝胶转变，在此过程中，PCD 可以分别消失（溶液）和重现（凝胶），并且可以重复多次这样的过程。此外，当加入少量 Mg 离子时，混合凝胶也会收缩，在此过程中 PCD 也会消失。因此，通过凝胶形成以及随后的金属离子或温度触发的相转变，可以实现 PCD 的可逆调节。这些结果不仅阐明了在手性修饰不存在于表面的情况下从非手性 GNRs 产生 PCD 的机制，而且提供了一种简单有效的方法来调节 PCD。
