Photochemically-induced electronic switching in carbon nanotubes

本项目的中心目标是制造和研究能够在高和低导电性两种状态之间进行可逆切换的纳米线。电子开关应在单壁碳纳米管（SWCNT）内实现，基于光诱导反应，减少管的π共轭系统的延伸，从而减少其导电性。为了获得能够重复可逆开关的稳定器件，SWCNTs将被包裹在由蒽衍生物组成的致密表面活性剂壳中。之所以选择这种类型的化合物，是因为初步实验揭示了光诱导蒽环加成到SWCNTs上的可能性，这可以通过热活化逆转。蒽基表面活性剂的化学结构将被优化，以与SWCNTs的石墨烯层实现足够强的pi相互作用，并具有良好的疏水/亲水性。透射电子显微镜、荧光光谱和原子力显微镜将用于确定两亲分子在swcnts上的分子排列以及swcnts /配合物对水溶液的稳定性，这两者都是pH值、不同离子的存在、温度以及光照射的函数。通过详细的电荷输运测量、扫描隧道光谱和空间高分辨拉曼光谱，比较光照射前后SWCNT/表面活性剂配合物的电子结构。由于在所有三种方法中，将检查相同的单个SWCNTs，因此获得的数据将允许对辐射效应进行明确的解释。将采用相同类型的研究来确定是否可以热诱导或通过较短波长的照射来实现由初始构型的环还原组成的反反应。此外，热循环或光循环研究将进行，以调查设备的长期稳定性。

The central goal of the present project is the fabrication and investigation of nanowires that are able to undergo a reversible switch between two states of high and low electrical conductivity, respectively. The electronic switch shall be realised within single-wall carbon nanotubes (SWCNT) on the basis of light-induced reactions that decrease the extension of the pi-conjugated system of the tubes and hence their conductivity. To obtain stable devices capable of repeated reversible switches, the SWCNTs will be enclosed in a compact surfactant shell consisting of an anthracene derivative. This type of compound is chosen since preliminary experiments revealed the possibility of photo-induced cycloaddition of anthracene to SWCNTs, which can be reversed by thermal activation. The chemical structure of the anthracene-based surfactants will be optimised to achieve sufficiently strong pi-interaction with the graphene layer of the SWCNTs, combined with a well-balanced hydrophobic/hydrophilic character.Transmission electron microscopy, fluorescence spectroscopy, and atomic force microscopy will be performed to determine the molecular arrangement of the amphiphiles on the SWCNT and the stability of the SWCNT/complexes against aqueous solutions, both as a function of pH value, the presence of different ions, temperature, as well as photo-irradiation. The electronic structure of the SWCNT/surfactant complexes will be compared before and after photo-irradiation by detailed charge transport measurements, scanning tunnelling spectroscopy and spatially high-resolved Raman spectroscopy. Since in all three methods the same individual SWCNTs will be examined, the obtained data will allow an unequivocal interpretation of the radiation effect. The same types of investigation will be employed to determine whether the back reaction, consisting of cycloreversion to the starting configuration, can be thermally induced or achieved via irradiation with a shorter wavelength. In addition, thermal- or photo-cycling studies will be carried out to investigate the long term stability of the devices.